Contents

1 Cross;Sectional Anatomy of the Brain. . . . . . . . . . . . . . . . . . . . . . . . 1I. Imroduclion I

II. Midsayill-al >(.'Ction IIII. Commll .st.'Ction through the op(ic chia:.m 3IV. Coron:11 S(,'CllQll through the mamillary boJio 4v. A:rcial inm!:,'c through Ihe Ih:llamU'i and imcm....1capsule 5

VI. Axial irJJ:1boe through Ihe midbrain. mamillary hodics. and 0I1'11c lr.'Cl 6

2 Meninges, Ventricles, and Cerebrospinal Fluid. . . . . . . . . . . . . . . . . . 8l. Mcnill/,'C5 8

II. Vcnuicul:lr sy:.tcm 10III. Cerehrospm<lllluid 11IV. Hcml:ltion II

3 Blood Supply 15I. The spinal cord :mu lower hrain slcm 15

II. The imerna! carOl:id SYSlcm 16III. The \'cnchrolxlSilar system 17IV. 1111,' hl/XXI supply of lhe iIHem:'[ c;lpsulc 18V. Veins or till' hr..in 18

VI. Venous duml sinu.$t.'$ 18VII. Anyiogral1hy 18

VIII. The middle 11l1'nin!:,'ca] :1T(("ry 19

4 Development of the Nervous SystemI. n,C Ileur;l] wbc 24

II. Thc Ileum] crest 2SIII. Thc ;mlcrior ncuropore 26IV. The lX>Slcrinr neuropore 26V. Microglia 26

VI. Myelination 27VII. P(l~itiona] chullgc~ uf the ~pinal cord 27

VIII. The optic ncrvc and chiasma 27IX. The hypophysis 27X. Clllgenit;l]lll;llfonnillions of lhe eNS 27

. . . . ......... .... ...... . . 24

5 Neurohistology....................... • . • . • . • . • . • . • . . . .. 30I. N('urons 30

II. Nbsl SUI\ililllCC 31III. AXOTlflllranspor! 31IV. W:lII~'ri:m dl'gcncrmioll 31v. alrOllmlOl\,~is 3 I

VI. Rl'gcllcrlllionofncrvccclls 31VII. Gliill cclls 3I

VIII. TI1C blood-hrain 1,.1rricr 32IX. TI1C Mood-CSF harricr 32

,

vi Contents

X. Pigmcnt:> :1r1<1 inclusion, 32XI. TIlC cl:',,~itiC;llion o( ncr\'C tillers 32

XII. Tumurs of thc CNS anJ PN$ HXIII. Cut:ll\('Ou, rC't:el't"~ )j

6 Spinal Cord 36I. Gr..), :'111(1 whit contmuniG'ling rami 36

II. Termimuion 01 Ihe conus rneJullaris 36

III. Location o( Ih... m"jor Tl\O{o.- and senSO!1' nuclei of the spinal cord 37IV. TIle caw" C<.Jllin" 37V. TIl(" m\-oI:llic Tl."Hcx 37

7 Tracts of the Spinal Cord ..... "........................... 38I. ImrtlducllOrl 38

II. DurSll colllmn-mcdiallt·mni.scus rr.tlhwa)' 38III. ulICT.ll srmothal:llnic tract 40IV. uucml cnrl:icosrinaltracl 40V. 1-ln"Mhal:un.-.;pinal tract 44

8 Lesions of the Spinal Cord "............ 45I. 1:>.sc:lSCS of the l1\O{or nl"\.lrons and eorticospinr.1 tracts 45

II. SctlSOr)' p:llh""ay lesions 47III. wnhmcd mOlur "nJ senSOf')' lesions 47IV. Peril'her.ll nervous S)"I('m (PNS) lesions 48V. Imcn'crl:chml d1$k hemi:Uioll 48

9 Brain Stem "",,"........................................ 49I. Overview 49

II. Cro:,.,-.....'Ctron duough the m(odulb 49III. Cros,-,cClion dlTou~h the pons 51IV. CroSS'SCClrnn Ihrough the rostral .nidhrain 52V. C..nicobull'<lr tibers 51

10

11

12

13

Trigeminal Systemt. Ov... rview 53

II. The lrigemin:ll g,rnglion 53III. Trigcminolh,lhrmic jl:llhw<lrs 53IV. Tri~cl1lin:ll ret1cxes 55V. TIl(~ CUVo.'rnOllS sinus 57

Auditory System ...........•.•.....•.•..................I. OI'crl'i<:1I' 58

II. TI1... ilUdiwry I'ulhw:l\, 58III. J l<:nnng defccts 58IV. AudiwT}' tc,lS 59

Vestibular System .... " . ".. "•.••••.....•.•...............I. Ovcrvio.'w 61

II. Thc bhrrinlh 61III. TIle vCSl:ihul:tr p<ldl\\~lrS 62IV. V<:"stihulil-O(:ubr reflex..." 63

Cranial Nerves .......................•.•.•...•.•.......I. TIle oIfacwr'1 ne("\'e 65

II. TIle OI'l(ic nen'e 66III. TIle OCUIOmQlo.- nen'c (CN III) 66

53

58

61

65

Contents vii

IV. TIl(" lrochlear ner e (CN IV) 67V. TIle Iril.'Cmin:11 ncr ~ (CN V) 67

VI. TIle :IbJucenl ru-o·c (CN VI) 6SVII. Thc facial nem.' (CN VII) 69

VIII. The ~·e:.tihuloc,-,chlC"..r n..·o"e (CN VIII) 71IX. TIle glo:.:;opl\;u)"nl.'CalllCo"c (CN IX) 71X. TIle vag:llllCO'C (CN X) 74

XI. The acCc:.soI)' nCO"C (CN XI) 75XII. The h~'p('I;IO::»;llllco'e(CN XII) 77

14 Lesions of the Brain Stem . . . • . . . . . . . . . . . . . . . . • . • . .. 78I. lcsions of lilt nleJull.\ 78

II. Lesions of lhe rons 79III. lesions o( lhe midhr..in 80IV. Acoustic nClIrllll1:l ("chw,lllnul1la) 81V. Jugubr (O!lII1lCIl syndmmc 82

VI. "Locked· in" syndrome 83VII. Cemml p.l1lline myelinulysis 84

VIII. "Top of lhe ha,ilar" ~yndrome 84IX. Subcl;lvian ~le,,1 ~yndromc 84X. TIle cerehdlol'llll1ine :mgle 84

:1.5 Ce,ebellum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . • . • . • . . . . . .. 85I. Function 85

II. Anmomy 85III. TIl<~ maiO!" ccrebellar r;lIh""~I)' 86IV. Cerebellar drJunction 87V. Cerebellar synJromes and lun"lOfS 87

:1.6 Thalamus .............................•.•............. 88I. Imroduction

II. Major Ih:lbmic nuclei :md thcirconneclions 88III. Blood soppl~' 90IV. The internal c;lpsule 90

17 Visual System . . . . . . . . . . . . . . . . . . . . • . • . • . . . . . . . . . . • . • . . .. 91I. Introdoction 91

II. TIle visual palhway 91III. The pllpilbry light Teilex radl\\~IY 93IV. Tht· pllpil);,r)' dilmion p'llh\\"<!\, 93V. The nC;lr rdlcx ;ll\d :Kcullunud;'llon I';llhway 94

VI. ConiC<ll and subcllnic,ll centers (or ocu);tr lllotilil y 94VII. Oinical correhllion 96

18 Autonomic Nervous System ................•.•.•...•.•.... 98I. IntroduClion 98 ~

II. Cr:mi:tl IlCO'Cl> ""'hh 1';1r:IS~"mp:llhefic componellls 98III. Communicatlng r:11111 98IV. NeurUllansmiucl'5 98V. Clinical cOlTcI.lIion 101

19 Hypothalamus ..........................•.•.......•.... 103I. Introduclion 103

II. Functions 105III. Clinic~11 correl.uion 106

viii Contents

20 Limbic System """"""""""""""""""""."." .. ".............. 107I. Imroducllon 107

II. Major components .md conn<.'Clion" 107Ill. 111e P"pc: circuit lOSIV. Clinical correlation 109

21 Basal Ganglia and Striatal Motor SystemI. 8a,;:]1 ganglia III

II. TI,e "I ri<llal (extrapyramidal) Illotur ~rStcm I 12III. Clinic;llcurrclmion 113

III

22 Neurotransm'"'ters . . . . . . . . . . . . . . . . . . .. . . . . . . .. . .........I. Impon;llll lr-Jnsmitle~ .uld their p,llhw;'IYS II;

II. Funnioll"l and dinic,11 cunsidcmtions 120

115

23 Cerebral Cortex ........................•.•.•.•.•.•.•...I. [mroJuc[ion III

1I.111e"ix.layeredncoconcx IIIIll. Function"l area. 121IV. Nw.....ll dcs!rocti\'c hemispheric lesions ..lid ')'tlll'tUlIlS IZ7V. Cetl.'hr<ll d"mimlllcc 117

VI. Split.hr<lin syndrome Il8VII. 01 her lesil)ns of the curpllS c;lll,)sulll 128

VIII. Brain ilud spin:d C<lrd tumors 128

121

133

137Index .........................................•.•....

24 Apmxia, Aphasia, and Dysprosody 129I. Apr<IXi,1 IZ9

II. Aph'l.i'l 129III. Drspn~xJy 131

Appendix .

1.Cross-Sectional Anatomy of the Brain

I. INTRODUCTION. The illustrations in this ch:lplcr are accompanied by correspondingm:l1.'11Clic resonance imaging (MRI) scans. Together they represent a mini-atlas of brainslices ill the three onhogonal planes (i.e., mids..'lgittal. coronal. and axial). An inscn oneach figure shows rhe level of the slice. TI,e most commonly lested Structures an:' labeled.

II. MIDSAGITTAL SECTION (Figures 1-1, 1·2, and 1-3). TI,e loc:uion oflhe struc­lures shown in the fif,oures should be known.

Galcarine sulcus

Cerebellum (vermis)

~::::;i-- Fourth ventricle

Corpus callosumThaJam",

Fornix (column) Motor strip

Interventricular foramen \/-\c-\-i-iI-+"';C~enll1ll sulcussensory strip

Pineal body

Superior and Inferior co4liculi(tectum)

Septum p&llucldum

Mamillary-bodY eN III

lamina termlnalis.~~~==::~=~~Third ventricle

Anterior commissure

Medulla oblongata

Agure 1-1. MiJsaginal section of (he br.lin :md brain ~lcm ~ho\\'ing the SlrllClurCS surrounding rhc rhird andfourlll vcntricles.~ hrnm srem includes rhc midbrnin (M), pon~ (P), and medulla oblongol('[l.

1

2 Chapter 1

Paracenlrallobole

Precuneus

Cingulale gyrus

Superiot frontal gyrus

Anterior cerebral arlery

Crista galli

Basilar artery

Sphenoid sinus:~:=::==~~S~Clivis

Nasopharynx

C2

Superior sagittal sinus

Parielooccipital fISSUre

Vein of Galen

Cuneus

Cerebellar vermis

Cisternacerebellomedullaris

Figure 1-2. Mid$<lgill,11 Tll<ll,'1'k:tk re~ollance inlaging ~:<tion duuugh the brain and bmin ~tem ~ho",ing rheimponmu structufCli ~urrQUnding the thinl anJ fourth wlllrklc". This b a TI-weightoo image. The l;:r.IY m;.lt[eris I,'fll)' (hYJ'Oimensc). wln'reas tile white m:lIh:r is while (hyperintense).

Corpus callosum --"'----_

lateral ventricle ---.'<:

Anterior cerebral artery __-=""..Optic chiasm

Hypophysislinfundibulum

Mamillary body--~-

Cerebral aqueduct

Fornix Thalamus

Vein of Galen

Pineal gland

Superior and inlerior colliculi

Fourth ventricle

Cisterna cerebellomedullaris

Spinal cord

'---~- Subarachnoid space

Figure 1·3. 1\,liJ....gilt",l1 ma},'!lCtlC rcs.m:lllce ima<.:ing section through the brain stem and diencephalon. Nou'the ccrebrospin31 fluid tract: lalcr.ll ,·cntndc, inren;emMculal fommen ufMonro, third ,·emMele, cerchr:ll aque­ducl, fourth n:mridc, foramen o( Mal,ocndle, cerebdlOllledull<ll)' cistern, and spin...l subarAchnoid .space. NOll.'also the relation between the optic chIasm. infundihJlum, and hnXl(lhysis (pituitary gland).

Cross-sectional Anatomy of the Bram 3

III. CORONAL SECTION THROUGH THE OPTIC CHIASM (Figures:l.4 and :1.·5).The location of the S[nICtures shown in (he figures should be known.

.....

Oplic chiasm-Globus pallidus

,.....-"

Agure 1-4. Coronal sccllon o( Ihe bmin al the lc\·d o( lhe :mler;or COllllll".sure••lJXic chi,blll, ,mJ amn:­dol!;l. NOIe Ihm dU' imemal c:.psule llcs hclwecn the cauJmc nucleus :mJ Ihe lentl(onn noch,'us (gl,lI'lm 1'l;:,II.Juoand put:llllen).

seplum peltucidom _

Inlernal capsula

Amygdala

Hypophysis

Cavernous sinus

Intemerftspheric llssore

Cingulclle gyrus

Corpus callosum

'"::===~=~:tt Lateral ventricle- Caudale nucleus

Third ventricle

c...--,!~ Optic chiasm

::"'--':--': ...JL Intundibulum

Inlerior carotid arlery

Agure 1-5. Coronal m:lgnelic reson,lnce imaging seCtion through the alnygd"li., UPIIC chi:bl1l.1, m(un,lIhu­1ll1'l1, :tnd intern:.l c:lpsule. The c:werl'!UlIS sinus encircles the ~clla turck<l ,lI'ld cont:lins the (ollowing ~lrllCll1res:

cranial nerl'es (eN) Ill, IV, VI. V.l, :1I'ld V·2; posl/.!:mgli"l'lic sympmhet ic tiher.~: :mel 1110.' intern,11 c:tro1ld :mer\'.TIlis is a Tl.weighted image.

4 Chapter 1

IV. CORONAL SECTION THROUGH THE MAMILLARY BODIES (Figures :1.·6 and1-7). The [ocalion of rhe SlfiJCtures shown in the /igurL'S should be known,

Lateral

ventfide)",,;;;;;;;:;::;')7'-

ThOdventricle

Sobstantia/~::::::-:'1..~Mamillary bod".es

Fornix

caudate nucleus

~~<1~~~~GIobus pallidusLateral ventficle

Optic tractInllMldibulum

Hippocampus

Agure 1-6. Coroml] SCClioll of Ihe brain <It the ]n·d of the th~llmnus, m:ullill:lry lxxlics. and hippocmnp:l](oml:lli(m. NOte lh;ll the intem:l] c:lpsule li ..-s belwecn tht, thalamus :lll<1 the IClUiform nucleus.

Corpus callosum

CaUdate nucleus

Putamen

Globus pallidus

Hippoeampl.ls

Crus cerebri

Thalamus

Internal capsule

Substantia nigra

Interpeduncular Iossa

Base of pons

,..::..c:E.__-,,-,\- Pyramid 01 medulla

Agure 1-7. Qmll\al m:II,'11elic fC>,()ll;lllce imaging SCClion of lhe hrain <lnd hmin Slem:11 lhe le\'c1 of the lhal­amus, ,Ind IUPPoc:lInp;.11 formation. NOll' lhal lhe poslcrior limb of the imern:ll cal)Su]e lics lX:lwl-en Ihe lhala­mus :m,1 the lcllo;oon Illlcl..·u, (put:llnen anJ globus pallidus). This is a TI-wcighlOO posrcontrast hnagc.

Cross-Sectional Anatomy of the Brain 5

v. AXIAL IMAGE THROUGH THE THALAMUS AND INTERNAL CAPSULE(Figures 1..s and 1-9). The location of the structmcs shown in ,he tigurN should beknown.

Internal capsule(genu)

Internal capsule(anleriot ~mb)

Lalllflll ventricle(lrigone)

Inferior coIlicuLrs

VISUal corte~Pineal gland

("-fl\1~~~lnlemalcapsule

\~~JJ~~~~~;~~ {posterior limb}n ~~~l~ThalamusCaudate nucleus (tail)

Putamen

Globus pallidus

Fom;~

Third ventricle

Corpus callosum(splenium)

Agure 1..s. Axial ,;tttKlfl of the hr.tin at the le\'c1 of tile IIllemal capsule and nasal ganglia. Noll,- th:llthcintem..1G1psule has an "melior luub. a ~..enu. and a posterior limb. NOll' al;;o that the corpus Clillosum l~ scc;­

tioneJ through the genu and ~plenium.

laleral Yefltricle

Septum peuudicum __and Iorni~

PUlamen-~~

Globus pallidus _

Insula

Exlernal capsule

Velum inlerpos;tum

~ sagiltal sinus-----'

.--- Inlernal capsule (genu)

Inlernal capsule(posteriof limb)

Thalamus and thirdventricle

T.......

Co<po, """'"'"(splerWum)

VISUal rlMialions

~---~VISOaIcortex

Agure 1-9. Axi:11 n~'1\eIlC rcson..nce im..ging ,;tttion at Ihc le\'el of the internal G1psule and basal ganglia.Note Ihal the caudale nucleus hull,,0e5 IIlIO ,he fromal hom of the l:lIcml \"emricle. In Huminglon~dise35C, lhereis a massiH' loss of -y-:nmnObutyric :}(iJ (GABA)·ergic neurons in the caudatc nucleus that results in hydro­ceph'::llus ex ,·acoo. A lesion of the I"ocnu of the imamal capsule results in :1 commlateral wC:lk lower f:u;e withsp.::lring of the upper face. This IS:I TI.wdghled image.

6 Chapter 1

VI. AXIAL IMAGE THROUGH THE MIDBRAIN, MAMILLARY BODIES, AND OP·TIC TRACT (Agures 1.-1.0, 1.-:1.1., 1.-1.2, and 1.-1.3). The ]oc-;Jrioll of rhe 5trucrurl'S5hown in the figure!> !>hOllIJ be known,

Madarybody

'-"J """"""eN III

Figure 1-10. AXial SCC{I,m of the N:lln ;II the k\"Od ulth.., 1l1lJN:lln, 1\\;ulliII:u)' hoJlc:., ,Ill.! ;lllIn......II.I. NUIeIh,1I dlC ..ub.clIlua llIgT;1 ,..,,,.IT;lll'!> rhl' crus c..,r..,bn fr<,lm rhl' h"1:Ilk'Il!Um~'rhe lIuJbr.lin.

C,I.t5 cerebti

Substantla nigra

- Postariot Cllrebtal arlery

0uadfigemlrIal cist&rn

Cerebella< _rnos

Figure 1·11.. Axi;l[ magnetic resonance imaging (MRI) Sl'Crion :1{ fhe 1e\1:!1 of (he midbnin and nlamilla!)'boJil$. lkauS<' of (he high iron OOIllCIll, Ihe red nuclei, mamilla!)' boJIl$, aoo suhsrantia nign s1ww a r<'JucedMRI signal in n.weighll..J imaj,.'CS. Flowing blood in the cc....bnll vessels stands OUt as a ~lgnal mid. Cer...brospinal fluid proJuce!i a srrong signal in thl' \"l'ntric\cs aoo cisterns.

Cross-Sectional AIlatomy of the Btain 7

Optic nerve

Optic chiasm

Optic tracl

Mamillary bodies

Superior sagittal sinus-

---_ ""'ygtlata

Infundibulum

Lalll'fal ventricle(ocapital hom)

Figure 1-12. Axial magnetic rCS0llanc<' imaging secrio.:m Ilr rhe k·".;:1 of the opric chiasm, mamillary Ixxli<.'S,and midbrain. This p.1\icllI has neurofibromllr~is type I and :Ul opric ner"e gHotnll. NOh: the sb: of the right OJ>lie ncr"... The inflilldibulum is poslfix<.od. This is a TI-wdl:htcd imal:".

--Infundibvlum

- Sphtnood sinus

- Uneul

CNt cerebri

Figure 1-13, Axi;ll tn;lgllel ic rcson;lnce im;lging seCl iun at the level of Ihe IIllc;11 incisure, oculornowr Ilcr\'c.and inferior colliculus. b there pmhology within the orhh!

8

2Meninges, Ventricles,

and Cerebrospinal Fluid

I. MENINGES an' thl"C'(" connective ti~suc membranes thaI "urruund dll~ spinal CllrJ andbmin.

A. n,e¥ con~bt of rhe pia mater, arachnoid, and dura malcr.

1. The pia mater is a delicate, highly vascular !:lyer of (tlnnective riSSl.IC. It c1o:,(·lycovers the 'urt:lCC 'If rhe brain and spinal ('lrd.

2. The arachnoid is a Jclicat(·. nOll\':l$Cuhu CQnll{'Cli\"c tis:.ul' lIlt.:mhr:m\.', It is locatedhCl\wcn rhe Jura mater and the pi;l m:ller.

3. The dUT;1 matl'T is the oUler layer of mcninl:.'cs, It consbts 1)( J"I\s..' connl'Cti"o.:" tis­:.lIC.

B. Mcningial spaces

1. TIle sub.uachnoid space (Figure 2-1) lies octween rhe pia ll\:lt£'r ;mJ the :mlch­noid. It terminates at the Ic\'cl of the S\.'conJ s;lcral \'ertebra. II contains the ccrc­br<J.Spinal fluid (CSF).

2. SUbdUr..l[ SP:lCC

a. In rhl' cranium, thl' sulxlur;11 spnce is rrnverseJ by "bridging" veins.b. In thl: spinal cord, it is n clinic;ll1y insignificnnt potcntial space.

3. Epidural spacea. Thl: cranial epidural SpiKe is ,1 potential Sp:lCC. l[ conrains rhl: IIlcllingl'al ;JT­

('crics :mJ veins.b. The spinal cpidur.. l SPilCC contnins f;lrry areolnr ti.~sue.lyrnph:Hics. and vcnUllS

1,lc",uscs. The cpidur;11 space m"y be injecred with:J l\)l:nl anesthetic 10 pro­duce;) pnrnvcrrebr:11 ("s:1ddle") nerve block.

C. Meningial tumors

1. Meningiomas arc benign, well-circulllscribed, slow-growing rumors. They accountfor 15% of primary intracraninl rumors nnd arc llIore COllllllon in wOlllen th~11l inmen (3:2). Ninety percent of mcningiol1lns arc suprarellturial.

2. Subdural and cpidur;11 hematomasa. Subdural hematoma is caused by bccrarion of the superior cl'R·bral (bridging)

\'eins.b. Epidural hematoma is c"llSC\1 by bcctarion of the rniddk· meningeal artery.

D. Tmuma

E. Meningitis is inllammmion of the pia-arachnoid area of the bmin. tile spinal cord, orboth.

Superior silglttal S,"US

IntefWnll'itu~r

fot,men 101 MOr'IIolThlld venltlCle

Inlellll!duocu~'C'Slern

CereD,a' ,)queducl

Ponl,ne CISU!'In

Pia maierArachnOId

Dura male,

Central tanal

Meninges. Ventricles. and Cerebrospinal Fluid 9

ArachnOId granulallon

Velum inle'pcKllum

Glealce,ebl"l ~,n ofG,~n

Superio, cislern

SH"ghl s,"us '"lenlorlYm

Confluence 01 ehes,"uses

fou,lh ventrICle

Ce'ebellomeOul~ryflNINl ClSlern

Suba,achnold spate

Sutldurtl sp,ce

_ Epldur,1 space

Spinal c,slernConus medullMls

FIlum lermlnale

FIgure 2-1. The "ulmrachnoid ~p,'CCS ,IllJ cisterns ,,( thc br.lin ,lIld ~Jlimll cord. Cerd'r,,,pirml tlmd " pn>.duced in the ch, ,mid pl~xllses ,,(! he \'cntriclcs. II exits the fourth vcntrlcle, cireulml'" lt1 the "Uh.lfilchll(lld "pace,,md enters th~ superior sagiu,11 ~in\ls through the arachnoid granllhniollS. No!e Ih,,\ Ihe conll. medllll:trI~ ler­mimucs at L·1. Thc lutllh;1I cistl:Tn ends at 5-2. (Rel'rimed with l'lCrl1li~il)n (rum Noh,lek CR. SIf<lllllllga NL.Dl:nwrl:st It The HUllum Nl'1I'OIIS SySlelll, 41h c<1. 11,ltinlllrl:. WilIi,lms & W,lkin", 1991,]'. 68.)

1. Bacterilll meningitis is charaeteri:eJ clinically by fever. headache, nuchal rigiJery.and Kernig's sign. (With the parient supine. the examinl'r Ocxes the p:ltiCOl'" hip,bm cannot extend the knee without causing pain. It b a :.ign of meningeal iTrim­lion.) [Remember: Kernig = knee. I More lhan 70% of c.be" occur in chilJrenyounger than 5 years of age. TIle disease lIlay cauS!..' cranial nerve pal:.il's anJ hy­drocephalus.

10 Chapter 2

a. Common causes(1) In newborns, bacleri<ll meningiris is most frequently caused by Group B

streptococci (Slre/JIOCOCCUS agalacfiae) anJ Escherichia coli.(2) In older infants and young children, it is most frequently C:lUSl...1 by

HacmOfmillt:> influenzac.(3) In young adults. it is most frequently c:lused by NeisSl,.'Tia mcningifidis.(4) In older adults, it is most frequently c:lused by Sm"Jrococcl4s pllellllloniae.

b. CSF findings(1) Numerous polymorphollucle:lr leukocytes(2) DecreascJ glucose Icvels(3) Increased protein lewis

2. Viral mcningitis is also known as aseptic meningitis. It is characreri:\.-d clinicallyby fC\'cr, headache, nuchal rigidity, and Kemig's sign.a. Common causes. Many viruscs arc associ:ltl..J with viml meningitis, includ­

ing mumps. echovirus. Clxs;Jckie virus, Epstcin-B:lrr \'irus, anJ herpes sim­plcx tnle 2.

b, CSF findings(1) Numerous Iymphoc},tes(2) Norm:11 glucose le\'c1s(3) Moderately increased protein le\'e1s

II. VENTRICULAR SYSTEM

A. The choroid plexus is a speciali:ed stmcture that projectS intO the lateral, thirJ, andfounh "cntrick's of the brain. It consists of infoldings of blood \'essels of the pia matcrIIl:l! afe coverl-J by modified ciliatcJ ependymal cells. It sccrete$the CSF. TIght junc­tillns of the choroi,1 plexus cells fonn the blood-CSF barrier.

8, Ventricles contilin CSF and choroid plexus.

1. The twO lateral ventricles communicate widl the thirJ \'entricle through tile in­lern~ntriculaf foramina of Monro.

2, The third ventricle is located between the medial walls of Ihe diencephalon. Itcommunicates with the fourth ventricle through the c('rchr.ll aqucducl.

3. The cerebral aqueduct connens the third and fourth vcnrricles. It has no choroidplexus. Blockage of Ihe cerebral :lqUl,duet results in hydrocephalus.

4, The fourth ventricle communicates with rhe subarachnoid space through threeuurlcr ()ramina.

C, Hydroccphillus is dibtion of the cerebral ventricles c(luscd by blockllgc of the CSFpathll'ays. It is characterized by excessive accumulation ofCSF in the ccrebr<11 ventri­cles or subarachnoid space.

1. NoncoOlmunicilting hydrocephalus results from obstruct ion within the ventricles(e.g.. congenital aqueducral stenosis).

2. Communicating hydrocephalus rcsulrs from blockage within the subarachnoidspace (e.g.. aJhesions after meningitis).

3, Normal-pressure hydrocephalus occurs when the CSF is nor absorbed by thearnchnoid villi. It may occur .second<1r)' to posttraumatic meningeal hemorrhage.Clinically, it is charneteri:ed by rhe triad of progressive dementia, araxic gait, andurin:u)' incontinence. (Remember: wacky, wobbly, and wet.)

4. Hydrocephalus ex vacuo results from a loss o( cells in the caudate nucleus (e.g.,Huntington's disease).

5. Pseudotumor cerehri (benign inrmcmnial hypenension) r ..'Suits (rom increased

Meninges, Ventricles, and Cerebrospinal Auid 11.................... . -

resistance to CSF outflow at tho:: arilchnoiJ villi. It occurs in obese young womcnand is charaeteri:ed by papillcJema without mass, elevated CSF pressure, and de­teriorating vision. The ventricles may be slit-like.

Ill. CEREBROSPINAL FLUID is a colorless acellular fluid. It (Jows through the ventriclesand into the subarachnoid space.

A. Function

1. CSF supports the central nervous syslCm (CNS) and proreets it against con­cussive injury.

2. It transports hormones and hormone-releasing faclOrs.

3. h removes metabolic waste products through absorption.

B. Formation and absorption. CSF is fonm.'d by the choroid plexus. Absorption is pri­marily through the arachnoid villi inlO the superior 5..'lgittal sinus.

C. The composition of CSF is clinically rele\'ant (1:1.ble 2-\).

1. The normal numocr of mononuclear cells is less than 5hd.

2. Red blood cells in the CSF indicate sub.1.rachnoid hemorrhage (e.g., caused bytrauma or a rup[Ured berry aneurysm).

3. CSF glucose levels are normally 50 to 75 mg/ell (66% of the blood glucose level).Glucose levels are normal in patients wilh viral meningitis and decreased in pa­tients with bacterinl meningitis.

4. Total protein levels arc normally octween 15 and 45 mg/dl in Ihe lumbar cistern.PrOlcin levels are increased in patients with b..1.Ct"erial meningitis and normal orslightly increased in patienrs with \'iral meningitis.

5. Normal CSF pressure in the l:ncral recumbent position r.mges from 80 to 180 mmH20. Brain tumors and meningitis elcv;lIc CSF pressure.

Table 2·1Cerebrospinal Fluid Profiles in Subarachnoid Hemorrhage, B....cterial Meningitis, and Viral Encephalitis

Cerebrospinal Subarachnoid Bacterial ViralFluid Normal Hemorrhage Meningitis Encephalitis

Color Clear Bloody Cloudy Clear. cloudyCell count/mm3 < 5 lymphocytes Red blood cells > 1000 poly· 25-500 lymphocytes

present morphonuclearleukocytes

Protein < 45 mg/dl Normal to slightly Elevated> 100 Slightly elevatedelevated mgjdl < 100 mg/d\

Glucose - 66% > 45 mgjdl Normal Reduced Normalof blood (80-120 mgjdl)

Cell counlS in infants < 10 cells/mm3; protein in infants - 20-170 mgjdl.

IV. HERNIATION (Figures 2·2, 2-3. 2-4, 2.5, and 2-6)

A. Transtenlorial (uncal) herniation is protrusion of the brain through the tentorial in­cisure.

B. T....,lnsforaminal (tonsillar) herniation is protrusion of the bmin stem and cerebellumthrough the fommen magnum.

C. Subfalcial herniation is herniation below the falx ccrebri.

12 Chapter 2

Figure 2-2. Coronal secrion of:l 1\11110r in th~ suprat~ntorial compartment. (/) Anterior cerebral artery; (2)subfalcial herniation; (J) shifting of \'Cntridcs; (4} posterior «rebral artery (compression r<:sul" in contralateralhemianopia); (5) uncal (translcl1!orial) herniation; (6) Kernohan's notch, Witll damaged corticospinal and oor­tioobuloor fibers; (7) tentorium cerebelli; (8J pyramidal cells that gi\'C rise to the corticospinal rrae(; (9) tonsil­lar (tr3osforaminal) herniarion, which damab'CS \'it:al medullary centers. (Adapted with permission from L.."<.'('hRW, Shuman RM: Nn-ropalholDgy. New York.. Harper & Row, 1982, p. 16.)

o\)/ ',

,

\--,

7

Figure 2-3. Axial sed:ion through (he midbrain and (he hernialing parahippocamp31 b'Yru$. The left oculo­motor nen-e is being stTetched (dilaled pupil). The left posterior cerebral arteT"j' is compressed, resulting in a con­(l1lbteml hemianopia.~ right crus cerebri is damaged (Kernohan's nOlch) by Ihe lTec edb"C of the tentorial in­cisure, resulting in a oon(r:l.1ateI1l1 hemiparesi$. Kernohan'$ nO{ch results in a fube locali:ing sign. The caudaldispbcement of the brain stem c:Juses rupture of Ihe paramedian arteries of the basilar artery. Hen'lOTT~"C intothe midbrain and rostral pontine t~'gmentum is usually fuml (Durel hemorrhages). The posterior cerebral arterieslie superior to the oculomotor nenl:S. (I) Parnhippocampal b'YTUS; (2J crus «rebri; OJ posterior cerebral artery;(4J optie nen~ (5) optic chiasma; oculomotor nen",; (7J free edge of tentorium; (8J Kernohan '5 notch. (Adaptedwilh pemlission from Leech RW, Shuman RM: Newropaflwloo. Nl'W York., Harper & Row, 1982, p. 19.)

Meninges, Ventricles, and Cerebrospinal Fluid 13..................................................... . .

B

A

c

D

E

Figure 2-4. Magncrk re,on:mc(' Imaging scan showing br:lin Imum3. (A) Inlcn\31 capsule; (8) sulxlurolhelllalOllla; (C) sulxlur.ll hclllafOlIIa; (D) thalamus; (E) epiJur.ll helll:1I01ll:1. Eplduml hem:llomas may cross JuralalIachm('nts. Sulxluml hClllafOmas do IlOl cross dum! anachment>.. TIle hypennlcnsc signals arc caused bylIIclhemoglobin. Thi;; i~ a TI'"'ciglll<xl illl:lb~'

A

B

c

D

Figure 2-5. Compuu:J roolUgr.lphy scan axial section showing lill imr.lparenchymal helnorrh.'1&'C in Ihe leftfrOflt;llloh:. (A)lmmp".Ir('nch)·n'l:ll helliorrha!.'C; (8) bter.11 \'entriclc; (Cl imcrnal capsule; (D) calcilied glomusin rhe rngone region of Ihe larcr;ll ventricle.

14 Chapter 2

A

B

cD

Figure 2-6. C{lmpul~.,j IOmograph)' axinl seclion ~h(l\\'iTlg lin cpidul1ll hCl1lillnma ,Ind ,I ~kull fmClure. (A)Epidural hemalOnm; (IJ) ~kllll fmc(lITc; (C) calcifie<1 pineal gland; (D) calciti('{1 glolllu~ in lhc lrIl,'unc r('gion oflhe 1.'lel111 venlricle. Th~, epidural helll,lt,lma is ,I c1a""ic hicOllVCX, or lentiform. ~h:Jpc.

3Blood Supply

I. THE SPINAL CORD AND LOWER BRAIN STEM arc ;)upplied with bloOO throughthe anterior spinal arrery (Figure 3-').

A. The anterior spinal art.:!)' supplies Ihe anh:rior two-thirds of the spinal cord.

B. In dlC nn.-dulla, th... amcriof spinal artery I>upplic:. the pyramid. medial lemniscus, andfOOl fibers of cranial neryc (eN) XII.

~{---..::::::"""'--'i---lnt8mal carotid •.Medial striate a.--------,,.......

Ant. spinal 8••-------~+_1

AnI. communicating 8.----_,'

Vertebral •..--------\IPost. Inf. cerebellar a.-----~1'(t

'*=~~-----,=-r-"',-\--Post. communicating a.

~~~~~~~=t~~~~~C~:N IIISup. cerebellar a. Post. cerebral a.Basilar 8. N V

Transversa pontine 88.---<'/.,.,;:;........:'

eN VU-=======eN VIIl-CNVI------~

Ant. lnl. cerebellar B••-----.

Middle cerebral •.-_.....

Lat. slriate aa'-::====~!JAn\. chOroidal a.

ArW.. oerebfal •.--------1

Figure 3-1. Arteric;s of the ba.-.e of [he hrain :tnJ hr;lin ;:,tCIII, including die arterial circle of Willis.

"

.1.6 Chapter 3

II. THE INTERNAL CAROTID SYSTEM (sec Figure 3-1) consiSl5 of Ihe in[crnal carotidartery anJ its branches.

A. The ophthalmic artery emers the orbil wilh Ihe oplic nerve (CN 11). The cenlralancry of thc retina isa hranch of the ophthalmic arrery. Occlusion results in blindness.

B. The pos[crior communicating artcry irrigates the hypothalamus anJ \'emral thab­mus. An aneurysm of this artery is Ihe second most common aneurysm of Ihe circleof Willis. II commonly results in third-nen·e palsy.

C. TIle anlcrior choroidal arlery arises from the imernal carmid arrery. It is not parI oftill' circle of Willis. h pcrfuses [he lateral genicuble body, globus p.111idus. anJ poste­rior limb of Ihe internal capsule.

D. TIle anlerior cerebral artery (Figure 3-2) supplies the medial surface of rhe hemi­sphere from the frontal pole to [he parieto-occipital sulcus.

1. The anterior cerebral arrery irrig:Hes the paracentral lobule, which conrains theleg-fOOl area of the mawr and sensory cortices.

2. The anterior communicaling artery connects the two anterior ccrebml aneries.It is the !1l11st common site of aneurysm of rhe circle of Willis, which lila)' causebitcmporallower quadrantanopia.

3. The medial striate arteries (see Figure 3-1) arc thl' pcnNra[ing arll'ries of rhe an­terior cerebral anl'I)'. They supply the antl'rior portion of the putamen and cau­Jale nucleus and the ameroinferior p::lrl of Ihe imemal capsule.

E. The middle ccrebml artery (sec Figure 3-2)

1. This anel)' supplies Ihe laleral com·exity of the hemisphere, including:a. Broca's and \Vernicke's speech areasb. The face anJ aml areas of Ihe moror and sensor)' coniccsc. The frontal eye field

A •

___IAnterior cerebral ar1ery

Agute 3-2, ConiCl.lll:rTItOfIl':i of dlC dlf~'C cercbr:tl ancrics. (A) uueml aspt'Cl of Ihe hemisphere. Mosl ofdll.' I.lll'F.I[ convexil\' is "up'phcJ by the nuJdlc ccrct>m.1 :lnefY. (B) Mt.Jial lUll.! in(cfior aspeclS of till.' IlI.'Illl:irl'll:fe.TIle (IIltcnoc cere"r:11 anel)' sul'pho lhe lll<.-Jial :.\.uface 1,( Ihe henlbllhefe from Ihe hllnin.'l lennin:llb 10 lhe

CII11CU". TIll.' pOSlcnlK cercbF.II :1II(1)' <uppllC.'$ Ihe ,·isual cuncx and lhe fI05lerior inie-rior surface of the le-mpo­mll.)j'l('. (Modifi..-J (rolll Tondur)'. as prcs.:mcd in Sobon:. J: Alias dt-r Allmami... des M...nsdll"lI. Munich, Urban &Sch\\~Ir.cnbcrg, 1%1, PI'. 1)]-1 l8.)

Blood Supply 17

2. The laternl striate arteries (Figure 3-3) are the penetrating brnnches of me mid­dle cerebral flrtery. They are the arteri~ of stroke. and they supply the internalcapsule. caudate nucleus, putamen, and globus paltidus.

III. THE VERTIBROBASILAR SYSTEM (see Fil,oure 3-I)

A. The \·ertebral artery is a branch of the subclavian anery. It givcs rise to the anteriorspinal artery (sec I) and the posterior inferior cerebellar artery (PICA), which sup­plilS thc dorsolatcrnl quadrnnt of the medulla. Thisquadrnnt includes the nucleus am­bii;uUS (eN IX, X. :md XI) and the inferiur surface of the cerebellum.

B. The basilar artery is formed by the twO V<.'rtebral arteries. It gives rise to the follow­ing arteries.

1. The paramedian branches of the pontine arteries supply the base of the pons,which inciuJes the corticospinnl fibers :lOd the exiting rOOt fibers of the abducentnerve (eN VI).

2. The labyrinthine artery arises from the basilar artery in 15% of people. It arisesfrom the anteriur inferior cerebelbr arrery in 85% of people.

3. The anterior inferior cerebellar artery (AICA) supplies the caudal lateral pon­tine tegmcntum. including eN VII, the spinal trigeminal tract of eN V, and theinferior surface of the cerebellum.

4. TI,e superior cerebellar artery supplies the dorsolateral tegmentum of the rostral

Medial.1de

__ • Caudal' nud8tIs

__ • Internal capsule

o

o_"Gklbus pallklus

.'

.' ,Middlecerebrel anery

.'

-- -- •••• ------ Amygdale

.'

.'

._- ..

Third ventricle.

"'"

Caudate nucleus ".

Anterior cerebrallll\8l'Y •

Posler\(lr cereb.alllrtery -

~L...;""J

o

FIgure 3-3. Coronal..ecllon through the cerebr;ll henmpherc:ll the le\'c1 o( Ihe internal Cllpsulc: and thala­mus ~howing Ihe major \':l>cubr tcrrilOrlCS.

18 Chapter 3

pons (i.c., rostrnl [0 the mowr nucleus of eN V). the superior ccrdX'lbr peduncle.the superior surfl.lcC o( the cerebellulll and cereocllar nuclei, and the cochlear nuclei.

5. The posterior cerebral artery (see Figures 3-1,3-2, and ).) is connected to lhecarotid artery through the posrerior communicaring artery. It provides the ma­jor blood supply to the midbrain. It also supplies the thalamus. lateral and me­dial geniculate bodies, and occipitallobc (which includes the visual cortex andthe inferior surface o( the temporallobc, including ,he hippocampal (ormation).Occlusion o( this artery rcsults in a contralateral hemianopia with macularsparing.

IV. THE BLOOD SUPPLY OF THE INTERNAL CAPSULE comes primarily from the lat­eral striate arteries o( the middle cerebral artery and the anterior choroidal arrery.

V. VEINS OF THE BRAIN

A. The superior cerebral ("bridging") veins drain infO the superior sagittal sinus. L'1c­cration rCS\lhs in a subdural hematoma.

B. l1\e great cerebral "ein of Galen drains the deep cerebral \'eins into the straight sinus.

VI. VENOUS DURAL SINUSES

A. The superior sagittal sinus receives [he bridging \"(~ins. and through the arachnoid\'i1Ii. the cerebrospinal fluid (CSF).

B. 111ecavernous sinus conrainsCN III, IV, V-I :lIld V-2. VI, and the pos(j~:mglionicsym­

p:uhcric fibers. It also contains rhe siphon of the internal carotid artery (Fi~'lJre 3-4).

VII. ANGIOGRAPHY

A. Carotid angiography, Figures 3-5A and B show the intern:ll carotid artery. anteriorcerebrnl artery. and middle cerebral arrery.

Superior sagittal S;r1\lS

Anlerlor cerebral arlery

Cavernous pan ollCA

Petrosal pari ol ICA

Basilar arlefY

Superior cerebral veins

- Superior saglltal sinus

Branches of MeA

Straight sinus

Coo1lluenee ollhe$lnuses

..... Transverse Sinus

verlebral artery

Figure 3-4. Magncllc resoml1lCC angiogr..llll. latcral projcction. showing (he mHJor \'cnous sinuses and aner­ics. N()(c thc bridging \'cins entering the supcriOl'" sagirral sinus. leA = imcm:ll carouJ fJrlCry: MeA = middle:cercbral artcl')'; PeA = poslcrior ccrebral arlel')'.

Blood Supply 19

B. Vertebral angiography. Figures 3-5C and IJ show the \'erlebral arte!)'. PICA andAICA, b.'lsilar artery. superior cerebellar artery, and JX'Slerior cerebral anery.

C. Veins and dural sinuses. Fib'Ure 3-6 shows Ihe intcrnal cerebral \·cin. surcriorc.... rebralveins, great cerebral \'ein. superior ophthalmic vein. and major duml sinuses.

D. Digital subtraction angiography. See Figures 3-7. 3-8. 3-9. and 3-10.

VIII. THE MIDDLE MENINGEAL ARTERY. a branch of the maxillaI')' artery. enters the cra­nium through the foramen spinosum. It supplicsmos[ ofthe dum. including ilSc.'lI\'arial por­tion. Lacermion n.'SUhs in epidural hemorrhage (hematoma) (Fib'urcs 3-11 and 3-121.

Lislot structures:

o

1? 1,3,,

~ "17><'""l :;;::k~.'- ~ ( 4

c

1. Anteriof cerebral artery2, Anterior choroidal artery3. Anteriof inferior cerebellar artery4. Basilar artery5. Calcarine artery (01 posterior cerebral artery)6. Cailosomargioal artery (01 anterior cerebral artery)7. Callosomarginal and pericallosal arteries

(of anterior cerebral artery)a. Internal carotid artery9. Lateral striate arteries (of middle cerebral artery)

10. Middle cerebral artery11. Ophlhalmic artery12. PericaJlosal artelY (of anterior cerebral artery)13. Posterior cerebral artery14. Posterior choroidal arteries

(01 posteior cerebral artery)15. Posterior oommunicaling artery16. Posterior inferior cerebellar artery17. SUperior cerebellar artery18. Vertebral artery

Agure 3-5. CA) Carolid angi~'l1lm. Iater...1projt.'Clion. (8) ClroliJ .mgiogmm. amcropostcrior proj«:tion.(e) Vcrtcbnll ,lOgi~'fam, hllcral proj«:tion. (D) Venebrnl angiogmlll. ,lnlcroposlcrior projeclion.

20 Chapter 3

- Confluence of sinuses

- Straight sInus

• Great cerebral vein (of Galen)

~ .Transverse sinus---

Cavernous sinus ~ •••

Inferior sagittal mus, .Intema! c:erebral vein

~~.~', SUperior sagittal sinus

Superior ophthalmic vein,... "Superior cerebral veins (bridging veins)

••

Agure 3-6. QmlliJ ;1nl,;;Oj;r.un, \'enous ph:tSC. showin!; the cerchml veins ;1nd \'cnous sinu:>t:'S.

Callosomarginal artery'" ACA

Pericallosal arteryofACA

Frontopolar branchof ACA

Ophthalmic artery--­

Cavernous ICA ::::::::::::::;~::.Petrous ICA

Cervical ICA----.=....~

J

~.L__..::----~~-MCAMl segment

""''-----='7'--PCoM

Figure 3-7. Carotid 'Illl,;io,;r.un, Iater.11 proje<:lioll. IJcntify lhe conicoll br.mchcs of Ihe .lIllcrior cercbr.11:lncl)' (ACAl ;1nd middle ccrehr.11 ;1r!('ry (MCA). Follow Ihe coun;c of Ihe inteOl;11 QlfOlid .Inel)' (leA). Re·mcmber Ih31 ;1neurisms of Ihe poslwior communicating arrcry may result in Ihird·ncf\·e l"llsy. The l);lI";lcemr.11lohule is irrigated b\' Ihe callosoll\<Irgin:lt .\rlel)'. Conical br.mchcs of the MCA arc designated with dots. 1'CoM:< posterior c()mlllunic~tl;ngartery.

Blood Supply 23.

Al segment of M;A

ACoM-~

Cavernous part 01 ICA

COrlical bfanc:hes 04 MCA

lateral striate branchesolMCA

M1 segment 01 MCA

Supraclinold part or ICA

Petrous part ollCA

i--~"7-Cervical part or ICA

Agure 3-8. ClImid :mlliuur..lm, al\lertll'ustcrior prvj~"Ctlon. Ickmify the mllerior ccrcbr..ll :UICry (ACA). mid­dle cerebral anery (MCA). and imemal carvtid arlery (ICA). TIle huri:untal br.ll'Khes of'the MeA pcrfu.e thC'basal ~"lI\lllia and intemal capsule, ACoM = anterior cOllllllunlc,lIing anery.

Posterior choroidalarteries

PeA, Pl segmenl-!-,

Thalamopertorating -l--­arteries

PCoM

Superior cerebellar artery"""~

Basilar artery-J.~-

Verlebral arlery' -+....;:A""--~

'-''-c_--Parieto-ocdpitarbranches 04 PeA

Calcarine branchesor PCA

Hemispheric branchesolSCA

:...L--- PICA

:~~:===:==--- Vertebrallll1ery

Agure 3-9. Vertebral angilll,'r.l1ll. laterJI Jlruj~"CtiOll. Two "tnJClUrcs :lre fwnd benn.--en Ihe posterior cerebralarlt:l)' (PeA) and Ihe :lUpcrior cerebdhlr :UI('I)" tbe telllurium ,md Ihe third cranial nerve, PeaM. - poslcriOfcomlllunicating "riel)'; PICA = posterior inferior cerebellar arl<'I)': SCA = superior cerebellar anel)',

22 Chapter 3

CaJcarine arlefY 01 PeA---~:;;,"":::~

/

PCA ---~;:'::'!t,Superior cereoellar----

arlery \

Basilar arlery ----.-<~:::--,,~

PICA _------.tli;; ..V

>--Tempo!'lll branchesof PCA

~>--Verlebralarlery

Figure 3-10. Vef!ehnll angiogrmn. mucroposrerior projeclion, Which anery supplies rhe visual cortex! TheC;IIClrine ,lIlery, a bnmch of the pClSlcrior cerebr.-I anery (PCA). Occlusioll of Ihe rcA (calcarine ariel)') re~ul(S

in ,I CUllImlateml homonymuus hemianopia, with 1Il;IeUI:lr ~paring. PICA"" posterior inferior cerebellar arlcl1'.

Oufertable

Diploe

Du'"

Periosteum(of inner fable)

Figure 3-U. An epiJuml hem:l!Oma results from laceralioll of Ihe middle menin~,'eal ariel)'. Arterial bleed·ing imo Ihe cpidurol space forms:l bi((xwex dOl. The das.sic Mludd inrcnml" is seen in SO% of cases. Skull fr.te·tu~ are usuall~' found. Epidunll hcm:lIomas r.ucly cr~ suturallmes. (Reprinted wilh pennission from OsburnAG, Tung KA: Handbook of NellromdioiOlO: Bram and SkIIU. Sr. Louis, Mosb~', 1996. p. 191.)

Blood Supply 23

'1--\-- Arachnoid

Figure 3-12. A 5ubdural hematom;1 (SOH) re5ulu (rom lacer..lloo bridging vcim. SOHs are frequendy ac­companied by t~lImatic 5ubar..lChnoiJ hemorrhage>' and cor{ical contu5i0Il5. Sudden deceleration o( the headcau:iC5 rearing of rhe superior cerebral \·cins. The SOH clI:rend5 ovcr thc cre>'t of {he con\'ell:it\' imo the imer­hcmi5phcric hssuw, but doc5 nor cro:\S the dllral ,1U<lchmellr o( the f.J1:: cerebri. The clot can be Cre5Cen{'5haped,biconvCll:, or lllultilocul:ncd. SDHs arc more common rhan epidural hcmmornas. SOI·1s alIVaY5 c,mse bl""<lin dam­age. (Reprinted with permission (rom Q;;burn AG, Tong KA: Handbook of Neuroriu.liology: Brain lind Skllil. St.Louis, Mosby, 1996, p. 192.)

4Development of the Nervous System

I. THE NEURAL TUBE (Figure 4-1) gi\'cs rise ro the centr'dJ nenrous system (eNS) (i.e.,brain and spinal cordI.

A. The brain stem and spinal com h:l\'c:

1. An alar plate thaI gh"cs rise to the sensory neurons

2. A basal plate that gi\'cs risc [0 the motor neurons (Figure 4·2)

B. The neural tube gh'cs rise (0 three primary vesicles, which dC\'clop infO five sec­ondary vesides (Figure 4-3).

C. Alpha-fetoprotein (AFP) is foond in the amniotic fluid and maternal serum. It is anindicator of ncurnl rube defects (c.g., spina bifida, anencephaly). AFP Ic\"cis are fe­duct.'<i in mothers of (('tuses with Down syndrome.

Neural plate

" Notochord

e_..J

Neural crest

Surface ectoderm

Neural lube

... ~ Dorsal rool ganglion

"Q2=AJarplate (sensory)

Sulcus limilans

Basal plate (molor)

e

central canal

Figure 4-1. Developmcnt of thc neural tube and crest. The alar pl:uc glvcs rise 10 sensory neurons. The bastlI1I31c gh'cs rise 10 mOtor ncurons. TI1C ncural crest givcs rise w the peripheral ner....ous ~r~lcm.

24

Development of the Nervous System 2S

Semicirculard"'"

t)-- Taste bud cellof tongue

"f-~':' Skin

"

Ampullae

,':-':;---Cochlea

,,----Tela choroidea

'------ smooth muscle

~~~tJ~l--VISceral epithelium

Fourth ventricle ---,

SVA column ----\"-;"'IVGVA column --~-'\~~~~GVE column ---~\:=-t)'~

SVE column ---~--":-t")'~GSEcolumn ---"~,,~":~'_'.:J-.x

Floor plate ---/'

Somatic striated muscle---~~~(tongue)

Branchial striated muscle --------;(larynx)

SSA nud,; -----1~ '\-_""\ Ajar plate ----enGSA column ---It-

Pial blood vessels---~

Roof plate (epeodymallayer)

Figure 4-2. The bfilil\ stem showing the cell columns derived (rom the ..br ..oo basal platcs. The scven ern·ni..1nerve lnod..litics ,Ire shown. GSA == b'Cnernl SOln,ll1c ,.fferem; GSE '" l.ocnernl SOlll,llic c((erent; GVA = bocn­ernl \'iseeml afferent; GVE '" genefill \·iscer-..I efferent; SSA '" speci:.1 som:uic ,liferent; SVA == special \'iscefi,1"lferent; SVE '" special \'iscernl efferent. (Adapted with pcnnission (rom Panen 8M: HUllUm Embryology, Jrded. Ne\\' YorK, McGraw-Hill. 1969. p. 298.)

II. THE NEURAL CREST (see Figure 4-1) gives rise tu:

A. The peripher:lI nervous system (PNS) [i.e., peripheral nerves and sensory and aurQ­nomic ganglia]

B. The following cells:

1. Pscudounipolar ganglion cells of the spinal and cranial ner\'e ganglia

2. Schwann cells (which ehlborate the myelin sheath)

3. Multipolar ganglion cells of autonomic ganglia

4. Leplomeninges (dH~ pi:'l-arachnoid) em'dop the brain and spinal corJ

5. Chromaffin cells of the suprarenal mcdulla (which elaborate epinephrine)

6. Pigment cells (meianocYlcs)

7. Odontoblasls (which elaborate pr\~dentin)

8. Aorticopulmonary septum of the heart

26 Chapler 4

Three primaryvesicles

Five secondaryvesicles

Adult derivatives of:Walls Cavities

Lower part offoorth ventricle

Lateralventricles

Upper part offourth ventricle

Cerebellum

Cerebralhemispheres

Pons

\'--. M"""~

) t--Midbrain

\\---

I

---'\\--Midbrain , Mesencephalon-~f-(mesencephalon)

~MelencePhalon

--j-j--Hindbrain --==-,(rhombencephalon)

Myelencephalon---1'f--

--;:r=t,cavilY / Telencephalon

-ttForebrainL-.DiencephaIon'---,H-(prooeocepha""'1

Spinal cord

Figure 4-3. The bmin \'csiclcs indic<llinl; thc adult derivativcs o( their wall;; and cavilics. (Rcprimcd withpcrmis;;ion (rom Moore KL: Thl> Det'ew,ling Hlmlllll: CUllicllll)' Orieurillg Embl)·~. 4th cd. Phil:tdelphia. WBSmmdcrs, 1988, p. 380.)

9. ParJ.follicular cells (calcitonin.producing C-cclls)

10, Skelelal anJ conncrli\'e tissue components of the pharyngeal arches

III. THE ANTERIOR NEUROPORE. The closure of the anterior neuroporc gh'cs rise to thelamina term inalis. Failure to close results in anencephaly (i.e., failure of the brain to de­velop).

IV. THE POSTERIOR NEUROPORE. Failure to close resuh's in spina binda (Figure 4-4).

V, MICROGLIA arise from the monocyles.

Dura Spinal cord

Arachnoid

Transverse

'''''''''

Subarachnoid

'PO'"

[),,,.

Neural tissue

~

A. Spina blfld. occulta 8. Meningocele C. Menlngomvelocele D. Rachischisis

Agure 4-4. TIle \~driol.ls I)'pes of spin.l hi6Ja. (RCjlrmtl-J wilh pcnnis:.ion (rom S;".Ilcr TW: UnlRJll(llt'S Med­iCIII Embryology. 6th ed. &lrllUurC, Wilh;lllt'> & Wilklll., 1990, p. 363.)

Development of the Nervous System 27

VI. MYELINATION begins in the founh month of gestation. Myelination of the corti­cospinal tTOlCts i,. not complcteJ until the ...nd 'If th... ,..,;cond IXhmatal year. when the tntel:>become functional. Mydination in th... cercbr.tl a:>:>ocimion conex continues into the IhirJdecade.

A. Myelination of the eNS i,. accompli,.he.J b\' olij:,'odendrocylcs, which are nO[ foundin lhe rdina.

B. Mydination of the PNS b accolllplishL-d by Schwalm cells.

VII. POSITIONAL CHANGES OF THE SPINAL CORD

A. In the newborn. the conu,. IllcJullaris end,. at the third lumbar vertebra (L·J).

B. In rhe adult, Ihe conus medullaris ends lit L-I.

VIII. THE OPTIC NERVE AND CHIASMA arc Jcriwd from the diencephalon. TIle opticnerve fibcr~ occupy the choroid fissure. Fai!llre of this fissure to clo~e resultS in colobomairidis.

IX. THE HYPOPHYSIS (pituitary gland) is d<:rived from twO embryologic subSU':lla (Fig­ures 4-5 lind 4-6).

A. Adenohypophysis is derived from an eChxh.:rlllal dh'crticulum of th" primiri\'" mouthcaviry (stomodeum). which is also calk·d Rllthke's pouch. Remnanrs of Rathke'sjX)uch may give rise to a congenital qsric tumor, a cr.miopharyngioma.

B. Neurohypophysis develops from a ventral evagination of the hypothalamus (neu­roectodeml of the neural tube).

X. CONGENITAL MALFORMATIONS OF THE CNS

A. Anencephaly (meroanencephaly) results from failure of the anterior neuropore toclose. As a result. the brain does not JL'velop. The frequency of this condition is101000.

Third ventricle

Sphenoid bone

Pars intermediaof anterior lobe

Neurohypophysis(posterior lobe)

~'h""-Dura

Infundibulum of hypothalamus

r~~"'-77'------::o'''-~Diaphragma sellae

Optic chiasm

Adenohypophysis(anterior lobe) --Ii<\ofu,+<

Pars tuberalisof adenohypophysis -t----'iIl

Craniopharyngeal canal Remnant of Rathke's pouch

Figure 4-5. Midsagill:ll..eclion through the hypophrM" and ..ella tun~lca. 1lle adcnoll}'J)()rhY'>I~.IllCloolllg,hc p:l!"S rubcr:aHs and p:111i UltCn1lt..J1J. lli Jenvt-d (flllil R:ldlke's pouch (oruecuxlenn). The neurohypo"h~"$b

an.)CS frum the mfunJibulum of the hypodl:llamu:. (nCUflJl."'<:fwcnn).

28 Chapter 4

Figure 4-6. ~!IJs;lgllml 'CCli,'n through til('· brain 3u.'"m and dIencephalon. A cr.lllioph.lTyngiom:l (llJT()(.t'S)IIe3 3Ul'mSCIl,lr III the nllJlllll". It cOlnpn:::.scs the optic chiasm :mJ hnltJlh:lbmus. Tlus tumor b the most com­mun SUI'T:uclll"naltumur Ihm ,JCcurs in childhooJ and the most CnmmQfl cau~ olhYI'OI'iWit;ITism in chilJren.Tlll~ b:l TI-wclghll.'d m.lj;netlc rCotlfl,lllCe im.ll,'illg sc:m.

'., ,,.'.

,2 ,,

.....

B

"."

..

FOfsmen magnum

, ,,',

A

." ,"'..,.. '

•

"'

Figure 4-7. Arn"ld-Oll,lri m,lllonn,1I inn. Mid'>:Igimll secli"n. (A) Noon;ll cerehelium, founh n:mride, :mJ1'r;lln 31CIll. (B) Ahn"rm:l] cerehcllum, i"'unh vClllridc, and 11min 31CI1I ~ho\\'ing thc common COllb-cllll<l1 :morn­alll"; (I) hcakmg "f the tl'CI.,1 p1.ue, (2) :ll/Uloduct:ll slcno>is, (3) kinking :mtllr.msftlramlll.ll hemi;uion of th..·l1wJutI,llIIltllhe \'endmll canal. anJ (4) lK'mi,t(ion anti unrol1mg of Ihc cerehclbr \'eTml~ inlt) the \'cncbrnlC:ln;l1. An :lCCOmpan)'lIlg meningomyelocele i3 common. (Rcl'nnwJ wllh rcnni""ion from Fix jI} BRSNeuroanmomy. J\;lltil))nn·, Willi,lIn.> & Wilkins. 1996, p. n.)

Corpus callosum

Lateral ventricle

Massa intermedia ;i~~i~l~Third ventricle --"'1! ..

Pons --"8>0\+-

Development of the NelVOus System 29

Polymicrogyria

Superior saginal sinus

Straigtlt sinus

c--- Confluence 01sinuses

f---------Jift- Cerebellar vermis

---'--£;0,.'--- Posterior fossa cyst

Figure 4-8. I}.mdy-W"lkcr 1Il;llform:ltion. Midsagill:11 so.:ction. An CI'lOrt\lOl.lS dil"l[ion of the (ourth vemriclen..'SUh:s (rom ("ilure of I!)t." for::nnm:l of Lu.chb lInd ~-Ia~:endic to open. This (ondilion is associated ..... lth ()((ipi­ml menin!,'ocelt·, de\'adon of the confluence of tile sinu:>cs (IOreu!:lr Hemphili). agenesis of the cerebellar \'er­mis, and splenium o( the corpus cllllosom. (Reprillloo ~'ith pcnni»lorl (rom Dudek RW, Fix JQ BRS Embryology.&lhillwre, Williams & Wilkins. 199i, p. 9i.)

B. Spina biflda resulu from failure of the posterior neuropore to fom\. The defect usuallyoccurs in the sacrolumbar region. The frcquenC)' of spina bifida occulra is 10%.

C. Cranium bifidum results from a defect in the occipital bone through which meninges.cerebellar tissure, and the fourth ventricle may herniate.

D, Arnold·Chiari m:llformation (type 2) has a frequency of I: 1000 (Figure 4· 7).

E. Dandy.Walker lIlalfOrln:ltion has il frequency of I :25000. It may result from riboflavininhibitOrs, posrcrior fossa trauma. or viral in(ection (Figure 4-8).

F. Hydrocephalus is most commonly caU:K'(1 by srenosis of rhe cerebral aqueduct duringdc\"(·lopmcnr. Excessiw cerebrospinal nuid Olccurnubtes in rhe ventricles and sub­arachnoiJ space, This condilion Illay result from malernal infection (cytomegalovirusand lOxoplaslllosis). The frequency is I: I(X)().

G. Feral alcohol syndrome is the most COllllnon cause ofmental retardalion.1t includes micro­cephal~' and conl,oeniml hcan: diset;c; hoioplOiCnccphaly is [he Ill()';[ se....ere m:mifestation.

H. Holoprosencephaly resuhs from f<lilurc of midline cleavage of lhe embyonic forebrain.Tl,e t~lencepbloncOnl<lins a singular \'cntricular caviry; is seen is trisomy 13 (Palausyndrome); the corpus c:lllosum may be absent; holoprosencephal)' is rhe most severem<lnifcsmrion of lhe feral <llcohol s)"ndrome.

I. Hydranencephaly rcsulufrom bilateral hemispheric infarclionsecondary lOocclusiono( lhe carQ{id arterieS. TllC hemispheres arc replaced by hugely dilated vennicles.

5Neurohistology

I. NEURONS arc classified by the number o( processes (Fi1.'Urc 5-1).

A. P~udounipolar neurons are IOGHcd in the spinal dors.,1 rom ~..angli;1 anJ sensory gan­glia of cr.lOial nc.....cs (C ) Y, VII. IX, and X.

Nissl substance

Schwann cell

Motor neuron

Nerve endings in muscle (myoneural junction)

Myelin sheath

Collateral branches

Auditory

Sensory (receptor) neurons

Olfactory

TTelaxon

"Synaptic endings (boulons terminaux)

Nod.01 Aanvier

Axonorigin _

Dendrite zone

Figure ~1. TI'I:lCl> o( nerve cdb. OIt;tCl'If)' neurons :uc bipobr ;lnd unmyc1in:u('(1. Auditory neurons ;uc hipo­\:IT :lnd rnyclin:lIl-d. ll...,rs;.l TIl()( gangllOll cdb (cUran('olls) arc plicudounirohu and mrclimucd. MO{()T neurons:IT(' multipular and mrdinalC<1. AlTOU's inJicatc input Through the ;I)(ons of mhcr IlCurollS. Nc.....c cells arc Ch;lf­oclcri:cd b)·.he prc..encc oiNIS>.1 Sllhslflnce :md rough endoillflsmic rclicuhnn. (/I.·loc!ilied with pcnnission iromC'lrpeiller MB. 5U1in): Illllnlm NClfTOOlllIIOlII)". Baltunore. Wllli;uns & Will.:ill~. 1983, p. 92.)

3.

Neurohistology 31

B. Bipolar neurons ;Ir~ found in Ihe cochlear anJ \'estibular &oanglia ofCN VIII. in theolfactory ner\'e (C I). and in the retina.

C. Multipolar neurons an' the Iarg\.'S1 populalion ofnerve cells in the nervoussysu.·m. Thisgruup includes motor neurons. neurons of the auronomic nen·OlIs SySICIIl, intem<.'UfOns,p)'ramidal cells uf the cercbml conex, and Purkinje's cdls of the cerebellar concx.

D. 11ll"re arc approximmcly 1011 neurons in Ih(' bmin anJ approximmely lOll) nt"urons inIht" n('oconcx.

II. NISSl SUBSTANCE is characleristic uf neurons. It cunsistsof rosenes of polysomcs andrough ~ndoplasmic n::liculum; therdore, il has;l rule in prolcin synlhesis. Nissl subslanceisfounJ in the nerve cdl body (perikaryon) ami dendrites, nor in Ihe axon hillock 1)1' axon.

III. AXONAL TRANSPORT lIleJiates rill' illlracelllllar Jisrribmion of secrelury proteins. or­g:mellcs, :'lnJ cyruskdef:ll <"lemcnts. II is inhibiled by culchicine, which depolYllll:ri:es mi­crorubules.

A. Fasl anterograde axonal transport is respl lIlsihle for transporring :111 newly synt hesizeJmembranous organelles (vesicles) and preCllrSllrs (>f ncuro[r:lllsmitters. This processOCCurS:l£ the fate of 200 [0 400 lIlm/d:'ly. II' i.~ mediall,J by neurotubules and kincsin.(Fast rr:lllSrX11't is neurorubule-dep<.'ndent.)

B. Slow :llllerograde tr-dnsporl is responsible for lr:msl'0ning fibrilbr C\,toskdef:J1 andprotoplasmic clemenls. This pnx{'ss occurs at Ihe rate of I 105 mm/day.

C. Fast relrogr-.lde lrdnsporl returns used materials from the axon (enninal ro the cellboJ~' for Jegnkl:lI ion anJ recrcling:Jl :1 nlte of 100 to 200 mm/da)'. It It:lllspons nervegrowth factor. neurotropic viruses, and toxins, such as herpes simplex, rabies. p0­

liovirus, and telanus toxin. It is mcJi:ucJ by neurorubules and dynein.

IV. WALLER IAN DEGENERATION is amerogmde degenl:ration characleri:cJ by th.... dis­appearance ofaxons and myelin sheaths anJ the secondary prolifer:llion ofSchwann cells.IT occurs in Ihe central nervous syslem (CNS) and the peripheral nervOllS system (PNS).

V. CHROMATOLYSIS is the result of retrograde degellet::ltion in the neurons of lhe eNSand PNS. There is a luss ofNissl substance after axolOlIly.

VI. REGENERATION OF NERVE CELLS

A. eNS. Effective reg..::n..::r:ttiun Joes not uccur in the CNS. For ex:nnple, there is no re­generation of th..:: optic nerve. which is:1 tr~lCt <)f the diencephalon. There arc no base­ment membr:mes or endoneural investments surrounding the axons of the CNS.

B. PNS. Regcncr:uioll Joes occur in the PNS, The proximal tip of a severed axon growsilllO the endoneuml tube. which cunsists of Schwann cell basement mcmbr:me andendoneurium, The axon sprout grows at the r:lle of 3 nun/day,

VII. GLIAL CELLS :Ire lhl' nonneurnl cdls of (he n('rmus sySll"Ill.

A. Macroglia consist of aSlrocytes and oligodendroc}'les.

1. ASlrocyte:; perfurm the following function3:a. 11ley prtljl.'C1 foot processes Ihal em'clup Ihe basement membmne ofc:lpillar­

ics. neurons. ;md synapses.b. Th(')' fonn the extt'rnal and intcrnal glial-limiling m{'mbranes of the CNS.c. TIle)' playa role in the melabolism of cenain neurolransmillers le.g.• 1­

aminOOutyric aciJ (GABA), scrotonin, glulmnmel.

32 Chapter 5

d. Onley buffer the potassium concenrralion of rhe extnlcellular space.e. TIley form glial scars in damaged areas of the br.lin (i.e., asnogliosis).f. They contain glial fibrillary acidic protein (GFAP), which ;s a marker for as­

trocytes.g. TIley conwin glutamine synrhetase. another biochemiclll marker for astrocytes.h. May be idemifiL-d with monoclonal antibodies (c.g., AzB;).

2. Oligodendrocytes are the myelin-forming cells of fhe eNS. One olib'Odendrocytccan my"linate as many as 30 axons.

B. Microglia arise from monocytes and function as the sca\'cnb'Cr cells (phago.::ytcs) ofthe eNS.

C. Ependymal cells ,If(' ciliated cells that line the central canal and \'entricles of rhebrain. TIley also line the luminal surface of the choroid plexus. Th~ cells producecerebrospinal fluid (CSF).

D. Tanycytes are modified ependymal cells thm contact clpillarics and neurons. TIleY meJi­ate cellular trallSpOfT between dlC vemricles and r!lc IleulUpil. TIlC)t project to hyporhal­amic nuclei th.1t "1,'lIlate dlC release ofgon..-mropic hormone /Tom t!lc adenohypoph)'sis.

E, Schwann cells are derh"ed from the neural crest. TIley are Ihe myelin-forming cells ofIhe PNS. One Schwann cell can myelinale ani)' one intemooe. Schwann cells im·~t

all myelinaled and unmyclinated a..'<onsof the PNS and arc separated from each orherb)' the nodes of Ran\'ier.

VIII. THE BLOOD-BRAIN BARRIER consists of rhe tight junctions of nnnfenesnared en­dothelial cells; some authorities include rhe asuocytic foot processes. Infarction of braintissue dCSTroys the tight junctions of endothelial cells and rC$ulu in vasogenic edema,which is an infiltratc of plasma into the extracellular space.

IX. THE BlOOD-CSF BARRIER consists of the right junctions between the cuboidal cp­idlelial cells of the choroid plcxus. TIle barrier is permeable to some circulating peptidcs(e.g., insulin) and plasma protcins (e.g., prealbumin).

x. PIGMENTS AND INCLUSIONS

A, Lipofuscin granules <lrc pigmented cytoplasmic inclusions that commonly aCClllIlU­hnc with aging. They ,ITC considered residual bodies thar arc deth'eJ from lysosolllcs.

B. Melanin (neuromelanin) is blackish intracytoplOlsmic pigmcnt found in the substan­tia nigra lmd locus cocruleus. It disappears from nigral neurons in patients who haveParkinson's Jisease.

C. Lewy bodies arc neuromll inclusions that are char.lcteristic of Parkinson's disease.

D. Negri bodies are intracytoplasmic inclusions that are pathOl,'110monic of rabies. TIley arefound in the pyramidal cells of the hippocampus and rhe Purkinjc cells ofthe cerebellum.

E. Hirano bodies arc intrlillcuronal, eosinophilic, rod like inclusions that arc found in thehippocampus of patients with Ahheimer's disease.

F. Neurofibrillary tangles consist of intracytoplasmic degenerated ncurofilaments. Theyarc seen in pmicnts with Al:heimer's disease.

G. Co\\'dr)' type A indusion bodies are intranuclear inclUSions that are found in neu­rons and glia in herpes simplex encephalitis.

XI. THE CLASSIFICATiON OF NERVE FIBERS is shown in Table )-1.

Neurohistology 33

Table 5-1.ClassificiUion of Nervc Fibers

FiberDiameter

holm) *

ConductionVelocity(m/sec) Function

Sensory axonsla (A-o)Ib (A-o)II (A·P)III (A-S)

IV (C)

Motor axonsAlpha (A-ul

Gamma {A·-y}

Preganglionic autonomic fibers (BI

Postganglionic autonomic fibers (C)

•Myelin sheath included if present.

12-20 70-120 Proprioception. muscle spindles12-20 70-120 Proprioception. Golgi tendon organs

5-12 30-70 Touch. pressure. and vibration2-5 12-30 Touch. pressure. fast pain. and

temperature0.5-1 0.5-2 Slow pain and temperature,

unmyelinated fibers

12-20 15-120 Alpha motor neurons of ventral horn(innervate extrafusal muscle fibers)

2-10 10-45 Gamma motor neurons of ventral horn(innervate intrafusal muscle fibers)

<3 3-15 Myelinated preganglionic autonomicfibers

1 2 Unmyelinated postganglionicautonomic fibers

XII. TUMORS OF THE CNS AND PNS arc ~hv\\'n in Figure 5-2.

A. One·third of brain tumors arc I11Clastatic, and two-thirds are primary. In metastatictumors, the primary site of malignancy b the lung in 35% ofcases. the breast in 17%.in the gastrointestinal U:'lCt in 6%. mdanomil in 6%. and the kidney in 5%.

B. Brain Imllors ate classified as glial (50%) or nonglial (50%).

C. According to national board questions, the five IIlUSt common brain tumors are:

1. Glioblastoma muhiforme, thl' most common and lllost (awl type

2. Meningiolllll, a benign llonitll'asive IUlllur of the falx ,mel the convexity of thehemisphere

3. Schwannoma, a benign periphcrnlllllllur derived (rom Schwann cells

4. Ependymoma, which is found in till' velltricles and accounts for 60% ofspinal cordgliomas

5. Medulloblastoma, which i~ the second must common posterior fossa tumor seenin children and ~na)' melastasi:e through the CSF tmcts

XIII. CUTANEOUS RECEPTORS (Fi!,"urc 5-J) are JiviJ(od into t.....o large groups: free nerveendings and encapsulated endings.

A. Free nerve endings :Ir~ nociceph>rs (p,ain) and th~nnoreceptors (cold and heat).

B. Encapsul:.lh:d endings arc touch rccepwTS (Melssner's corpuscles) and pressure and vi­br:uion rt."Ceptors (Pacinian COll>uscI6).

C. Merkel disks an: Unenl""llpsulatoo light touch receptors.

34 Chapter 5

)--"r-- GlloblaslorN1 multilotme• represer'llS 55% 01 gliomas• malignant; rapicJy !alai

astrocytic tumor• commonty~ in the I.ontal and

temporal lobes and ba.saI gangia• Irequently aosses the mdne Yia the

corpus caloslm (buIIerfly glioma)• fflOSf common prionary brain tumor• NsklIogy: pseudopaJisar;I

perivaso.oIar pseudoro$elles

Oligodendrogliomas• represenl 5% 01 al

!he gliomas• !7OW slowly and are

relaliYely benign• most common in !he kontallobe• caJcilicalion in~ 01 cases• cells look ~ke"'friedeggs' (perinu::lea.l\alos)

Meningiomas• derived lrom aracMokl cap cells and lepresenlthe second most

common primary intracranial brain lUmot after aSl.oeylomas (15%)• are not invasive: they indent the brain: may produce hyperostosis• padlology: concenlric: whor1s and calcified psammoma bodies• location: parasagittal and convexiry• gender; females> men• associated with neurolibromalOSis'2 (NF·2)

Astrocytoma,• represent 2O'llo 01 the gliomas• histologically benign• lM1usety inIi1trale the hemispheric ..tIite malte<• most convnon glioma bond in !he posterior

Ependymomas tossa 01 children

A

B

Germlnomas• germ ceM tumors tha' are commonly

seen rn the pineal regron (>50%)• overlie the tectum ot \he midbrain• cause obstruclNe hydrocephalus due to

aQl,le(luclal stenosis

• \he common cause of Paunaud's syndromeO_-'2f'l,=,

B,ain .bscltSRS /r-_• may resull lrom sinusilrs,

mastoiditis,hema1ooenous spread

• Iocaton: lrontal andtempofallobes. cerebelum

• organrsms: streptoeoe:ei.staphlocooci. and

"'"""""'"• 'esul in cerebral edemaand hemiallon

Colloid eyslS ollhlrd Yflltricle• comprise 2"110 oIl'llraerarnaJ gliomas• are 01 ependymal origin• Iot.Wtd at the ~_ntricularJoraminIa• ventricular obslnJcbon resuhs I'l increased •

intracranl31 p1'essd"e, and may causeposiIionaI headaches, "drop altacb:Of sudden tleattl

Brain stem glioma• u$l,lally a benign pilocylic: astroeyloma• usually causes cranial nerve palsies• may cause the "lodled-in" syndrome

C,anlopharynglomas• represent 3% 01 primary brain tumors• derived Irom epitheliaf 'e<TWlllIlts 01 Ra1hl<e's pouch• location: suprasellar arad inlerior to !he opOc chiasma• cause bilemporaf hemranopl8 and hypopiluilarism• calcitieation is common

Piluitary ~nomas (PA)• most common lumors of the pltuilary gland• prolactinoma is !he most common (PA)• derived Irom lhe stomodeum

(Rathke's pouch)• repreS8f'l1 8% ot primary brain tumors• may cause hypopituilarism, visual

lield delects (bitemporal hemianopiaand cranial nerve palsies CNN III, IV,VI, V·, and V·2, and postganglionicsympalhetlc fibers to the dilalormusclo of tho iris)

Schwannomas (acoustic neuromas)• consist of Schwann celfs and arise hom the

vestibular division 01 CN VIII• comprise approx, 8% 01 Intracranial neoplasms• pathology: Antoni A and B tissue and Verocay bodies• bilaleral acousllc neuromas are diagnoslic 01 NF·2• gender: female> mon

Choroid plellus papillomas• histology: benign: no necrosis Of inYasiIIe leatures• represent 2% ot the gliomas• one ot \he most common brain tUmoB in patients" 2 yea~ of age• occur in decreasing Irequency: lourtto, lateral. and third ventricle• CSF owrproduclion may cause hydrocephalus

Cerebellar aslrcx:ytomas• benJgn tumors 01 childhood with good prognosis• most common pediatric: intracrarvaltumot• contain pllocylic: astroeyles and Rosenthal libers

Medulloblastom,s "~__"",L/-~• rllpfesent 7% ot primary brain tumors• repr&S6f'lt a primiliye

neuroectodermal turTlOf (PNET)• second moSI common posterior lossa

tumor in children• responsible for the posterior vermis syndrome• can metastasize via Ihe CSF tracts• highly radiosenSitive

HemangloblllSlomas-------~• characterized by abundanl capillary blood vessels

<lI'Id foamy cells: moSt Ol1on found in the celebellum• when found in the cerebellum and retina,

may represent a part 01 the von Hippel·Lindau syndrome• 2% of primary intf8C'anial lumors: 100'. of posterior fossa,,- :~=~==;.~=::~==~Int,asplnat tumo., Ependymomas• Schwannomas 30% • represent 5~. ot the gliomas• Meningiomas 25~ • histology: benign, epen<lymaltubules.• Gliomas~ perivascular pseodoroseltes• Sarcomas t~;, • 4~. are supratentoriat: 60% are inlralentoriaf (posterior lossa)• Ependymomas represent • most common spWlal cord glioma (60%)~ of intrame<lUllary gliomas • thwd most common posterior fossa 'umor In chifdren and adolescents

Figure 5-2. TUI1l"~ Pc' Ih(· celllmi :mJ IX·,il,h~'r:l1 tle,nlU> sy~ll·llb, (AI Surmt~'ntori,llltllll"""',(B) Inir.lICll·ll'rI..1(1"."'I~'n", I~'~l) ,1l,,1 illlt:I~l'in"llulllill'S. In chilJrl'll. 70'''' (II tUII"'''''' ,If.' llllmn:~m"fl,'1. In ....lull,;;, 70% oflUn"'11i an: ~lIl'r.llcnl"n"l.eN "" Ct:ltl",1 ncrn.'; CSF = c('rchn"'I'IIl:llllui,l.

Neurohislology 35

Free nerve endings Meissner corpuscles Merkel cells

Deri'TVs

Merkel disk

...."",", "",m'",'''' } Epido,mi,

IJ--~ Pacinian corpuscles

Adipose tissue

o

A-P fiber

o

Cutaneous nerve

Agure $-3. Foor imporlam cumn~s r.x:cptofS. Free ne.....e endings m....Jiate rain and lempermure sensalion.Meissner oorpusck'S of Ihe Jemlal p::lpillae mediate maile ",'O-point discrimination. Paccinian corpuscles of thedermis m...-diatc tOllch. pressure and \·ibrntion sensation. Merkel disks mooiate light looch.

6Spinal Cord

I. GRAY AND WHITE COMMUNICATING RAMI (Fi~rurc6.1)

A. Grny communicating rnmi contain unmydin:uN ['OStl,oanglionic sympmhcric flbers.They arc founJ ;u alllcn-is of the spinal corJ.

B. White communicating Tami coma;n myl'limm'd prcl,oanglionic liymly,uhclic fil'CTS.They arc (0\111(1 fmm T-J til L-l (thC' CXICIll of the Imcml hom and th.:- inH'm,roiob,­ernl cell column).

II. TERMINATION OF THE CONUS MEDULLARIS (sec Figure 2-1) occurs in the new­born m rhe !(>H" of rhe body of ,he thir<llumhar \"cncrm (L·}). [n ,Ill' aJulr. if occurs at,he lc\'c1 of til<.' lo\\,{'r burder of rhe firSI lumhar n'nchra (l·!).

Prevertebral ganglion

Motor endplateGSE fiber

Alpha motor neuronof ventral hom (GSE)

GSA fibers

InterneuronGVA fiberSweat gland

Dorsal rootganglion

Peripheralnerve

Postganglionic, \,~ \ Preganglionicfibers ~'While '. .\ fibers (GVE)

, -4' ramus ~ ~ - (4 " PostganglionicGray ramus ,neuron

Blood vesser ~r~r-::::= Digestive tubeParavertebral ganglion (f

(sympathetic trunk)

Figure 6-1. TIle (ulir (lI11Cli"nal cnml'onetlls n( the Illllr.,cic sllinal n.... rn.': /;cncr.tl d:\Cer.tl :,tT~'renl (GVA),g.... ncrnl somllfic affercnl (GSA). Jlcncml Sl'mali( elierent (0SE). :tnJ I,ocllernl \'isccrnl cf(.... n.'tlI (GVE). Prol'rlO­ccpli\'e, cUl:tneous. :md visn'ml rdl...x :on:;i :Irc muwn. TIll' musclc slrclch (myoralic) reHex mdlll.k~ lhc lllllsdespindl.... GSA ,Iorsal n'lOl Jlangfinll cell. GSE \,('nlml hum m'lIor nellH'n, :ull.! ,kdelJll muscle.

3.

Spinal Cord 37

Table 6-1.The Five Most Commonly Tested Muscle Stretch Reflexes

Muscle Stretch Reflex

Ankle jer1<Knee jer1<Biceps jer1<Forearm jerkTriceps jerk

Cord Segment

5-1L-2-L-4C-5 and C-6C-5-e<;C-7 and C-8

Muscle

GastrocnemiusQuadricepsBicepsBrachioradialisTriceps

III. LOCATION OF THE MAJOR MOTOR ANO SENSORY NUCLEI OF THESPINAL CORO

A. The ciliospinal center of Budge, from C-B (Q T-Z, mediates the sympathetic innerva­tion of the eye.

B. The intermediolateral cell column, from C-B to L·3, mediates the entire sympatheticinnervation of the body.

C. The nucleus dorsalis of Clark, from C·B ro L·3, gives rise to the dorsal spinocerelx'l­lar tract.

D. The parasympathetic nucleus, from 5-Z to 5-4

E. 111e spinal accessory nucleus, from C-I ro C·6

F. The phrenic-nucleus, from C-3 to C-6

IV. THE CAUDA EQUINA. Motor and sensory rootS (L.Z to Co) that are found in the sub­arachnoid space below the conus medullaris fonn the cauda equina. They exit the \'enc­bral canal through the lumlxlr interwnebrnl and sacral foramina.

V. THE MYOTATIC REflEX (see Figure 6-1) is a monosynaptic and ipsilateral musclestretch reflex (MSR). Like all reflexes, the myotatic reflex has an afferent anJ an efferentlimb. Interruption of either limb results in areflexia.

A. The afferent limb includes a muscle spindle (receptor) and a dorsal rOOt ganglion neu­ron and its la fiber.

B. 11,c efferent limb includes a ventral horn mOtor neuron that innervates striated mus­clc (effector).

C. The fivc most commonly tcsted MSRs arc listed in Table 6-1.

7Tracts of the Spinal Cord

I. INTRODUCTION. Figure 7-1 sh"ws the ascending and descending (met;; of the spinalcOTel. This chapteT c, weTS four of the major tracts.

II. DORSAL COLUMN-MEDIAL LEMNISCUS PATHWAY (Figure 7.2; sec also Figure8-1 )

A. Function. The do~,1 c'llumn-mcJiallemniscus pathway mediates tactile discrimina­tion. vibration S('nsariun. form rcclJgnition. and joint and musclescnsarion (consciousrropri()C("prion).

B. Receptors inciuJe Pacini's and Meissner's tactile corpuscles. join! receplOrs. musclespindles, and Gol).!i 1.'llllon org:ms.

C. First-order neurons aTC' located in the dorsal root ganglia ;It alllc\'c1s. They projeCT,owns TO the spinal curd rhruuj.!h Ihe medial rOOT cnny zone. First-order neurons gh'cri.~(' TIl;

1. The J.!mcilc fasciculus fmm the lower exrremiry

Ascending tracts

Gracile lasciculus

Cuneate lasciculus

Dorsal spinocerebellar tract

Lateral spinothalamic tract

Ventral spinothalamic tract

o

Descending tracts

Lateral corticospinal tract

Hypothalamospinal tract

Rubrospinal tract

Vestibulospinal tract

Ventral corticospinal tract

Figure 7-1. The major ascending :lnd .IcscenJinj.: p;uhwars (>f Ih,' spin:ll conI. The usc,'nding sensory IT:lCU;Ire .nnwn ...n tilt: kff. and th,' de-<ccndlng rn\~l,'r lr;ICI~ :lrc shown (>11 lhe ng#z,.

38

Tracts of !he Spinal Cord 39

Pons

Medulla

')";''r--Arm area

++-- Spinal trigeminal nucleus

'4----:I----Mediallemniscus

Midbrain

'----J~--Decussation ofmedial lemniscus

~------ Medal lemniscus

~_~< ';!>------Mediallemniscus

Internal capsule ----!t,.,....ff-

Thalam~-----~~rl___il_;t ""'- Head area

~~~~~~~=Face areaVentral posterolateral

---.)><i~:S:::~?:::::;:~~(l~ nucleus ollhatamusLentiformnucleus:'" (neuron III)

Postcentral gyrus

"'C;::::------Leg area

\~::<"',._--Trunk area

Nucleus gracilis

Nucleus cuneatus----~L,,-r

Internal arcuate libers(neuron II) -------1".:::::..----

Cuneate fasciculus

Dorsal root gg'~":9~1~IO~"~'~'~"~~:::~~:~~:~~~;~~~=========- Gracile fasciculus(neuron I) - Cuneate fasciculus

Cervical cord

(®~~~~-----Gracile fasciculus

Mel,,",,', - ,oorpUSCIe~ :/~ __ ~ - -.... Lumbosacral cord

Paciniancorpuscle --,...,"'''-__'=

Figure 7-2. The Jorsal column-mooiallemniscus pathlOo'll}·. Impulses conducted by Ihl~ I'mhlOo~I~' rnc..J.;IlC Jl~­

Cr1min:ltory tactile sense (e.g.• tooch...·jhration, P'fessurel and kmc"lhellC !lCIlSC (c.g.• iJ'.biIlOIl. nlO\·en~IlI). Thedors..'11 column syStem l",,--diates conscious proprioception. (Ad'll'lloo wuh ~rmission irum Cll·~nto:-t ~IB. SulmJ: Human Nellr(lmlaloln:Y. Baltimore, Williams & Wilkin•• 1983. p. 266.)

40 Chapter 7

2. The Cllncare fasciculus f~olll rhc 1I1'f'<'r extTl'll1ily

3. The cullarl~I~llsfur ~rinal reflexes (c.g., lll,·oraric reflex)

4. TIlle' aXI'ns thai ;L'«"cnd in rhe dnT"al cnlllll1n~ and tennin:l\c in dw ,Il:T;icilc ;llldcuneate nucle; of Ih(' caudal nwdlilb

D. Sl"Cond-order neurons ;'rc Incated in the }!mcil(' allli CUllcat(' nucl('i of thc cauJalIlll-Julla. They gh·c rise I" axon" and ;nt('rnal arcuate fil'Crs Ihm dl"CllSSo11(' and fnrm acUlIlpacl fil'Cr hunJle (i.e.. m{"o.!iallemlliscus). The Illediallclllni.sclis m:cell1.!S Ihrnughthe ctlnl~llateral b~l;n ;;;tl"m and H'rm;nares in Ihe \·('llTral rustl'rLlbteral (VPL) nu­cleus of Ihe Ihalamus.

E. Third-order neurons are l"cal('(1 in tilt' VPL nucl{'us ,)f the thalamus. TIw)' rrujl"'CtIhrnut:h thl' r"-rcri,,r lilllh of Ihe illtem;)1 clpsule III the I'llslccnlml ,Il:ynlS, which isIhe rrimary "'um:l1. >SCIlSl.ry nlrtcx (I'I< 'l!tn,lIl1l's areas 3. I. anJ 2),

F. Transection of the dors-11 eolumn-media!lcmniscus trael

1. Above the sensory d{'Cussalion, Ir:105(·cri••n r(';;;\lhs in cumml:ul'mllossnf the Jor­s.,1 cI,llImn 1ll....Ia!ilics.

2. In the spinal cord, tmnR"1.:li"n r("<lIlts in ip~i1mcral luss of the JOTS.11 culumnlIlllllal it ics,

III. LATERAL SPINOTHALAMIC TRACT (Figllre 7- >: "'C'l' also Figur(' 8-1)

A. Funclion. Th.. Imeml spillOlhalalllic tmcl IllNialCS pain :mJ tl'lllpemlllTe senS."1Iion.

B. Receplors arl' fflX' Ol'f\·C l'nJing-s. TIll' lareT;11 spin,'thalamie Imct receh'('S inp\II frumfast- ;Illd :.luw-c"I1Juclin~ pain fil'Crs (i.e .. A & ,md C, r('1>f'L'·Cli\·c1y).

C. Firsl·order neurons ;.re f"lInJ in Ih.. dilf"al r.....Jt J:::tn.t:lia:u allle\'cls. Thq· prujo.:."Ct ax­ons II' til(' spin:ll cnrd dlTllugh rh1.· d.II"ulall'r..l trael ,-.f Li:-';;;;-l\ll'r (I'lIer.11 rLll11 ('nTT)'

:nnc) II) ~o.:onJ·l,rder n('urons.

D. Second-order ncuronll ;.rl' ft'lIlld in rill' dorsal hurn. They givc rise to axons that .1("­cms;uc in dw \·cntral while commissur.. and as{'("nd in lhe c.mtrabll·r:.1 bteml fu­niculus. Theil axnns termin,l(c in the VPS llucleus ,-,f Ihe thalamus.

E. Third-order ncur'lIls arc found in the VPL nucleus o( the thalamus, They prujcctI'hTClllgh the I'ostel ;,)r limh of till' internal G1l'sulc [, 1 111(' prinwry ~11llat(lscn..... ,ry cor­t..x (Brodmann's ;lrl':l,~ 3. I. :md l).

F. Tr,lIlSl'ction of the lateral spinothalamic Iracl results in c, \Il1T01lateral l().~s. ,f pain andtClllpcralur(' h'lo\\' Ihe lesinn.

IV. LATERAL CORTICOSPINAL TRACT (Fij,lllre 7·4: see ;ll~, Figure 8-1)

A. Funclion. TIll' Iater:.l cnnicospillnl Ir,K"1 mcdin[l's \<nluluary skille.1 mOIOl aClivity,primarily, 'f Ih.. ul'lx'r liml's. It is 11'" fully myC"linmc.I'llllilt he end of 1he seo.:.l[\L! ye;.r(B:lhinski's :oign).

B. Fiber caliber, AI' )TLlximatC"ly 90% of lhe fil1Crs lie hetween I :md 4""111. and 4% lie:11)(11"(' lOJ.L1Il (frol 1 til(' gianr cells o( &'1:),

C. Origin and termination

1. Origin. Till' 1:1I.'r;11 ctlnicospinallmcl arises frlllll layt:r V of th(" cer{"hml conexfrom lIun' conic:ll :ueas in equal aliqull1:>:a. TIl(' prcmotor corlex (BruJm:lnn's an,'a 6)b. TIle prim:.ry corlex (Br,,,lmann's aTl'a 4)

Tracts of the Spinal Cord 41

Ventral posterolateralnucleus (VPl)Neuron III

cerebral cortex(postcentral gyrus)

~ii:":~-: .7,'7'::le-- Axons of neuronsin posterlor limb ofinternal capsule

Crus cerebri --'

(~,",,--rL-+---A'""""'"'

Corpus callosum ----f';=-~---""'

Intemal capsule ----\tI~~_::___:;:;;----J~~

Mediallemni$CUs --------JI----{21

Thalamus -------\~;.(.1_J1I_ ....___'\

Medulla

CJ 0 0

Neuron I(dorsal root ganglion cell)

\\---~ Lat6fa1spinothalamic tract

•

Freenerve ~endings W--

Neuron II Ventral while commissure

Figure 7-3. The hltcf:11 ~lJinl)th;lhlll\ic 1f:!Ct. Imllulses comll!CtOO b)' this Imct rnt-Jiatc p;lin ;md thermalsense. Numcrous collatcmls arc <!is\rihu{eu 10 the hrain stem reticul;lr (ormation. (Rcprimed with rcrml~lon

(rom Clq~lllcr MH, Sutin J: f-IwntUl NCrlTO(lIlIl/0IllY. 1~r1thl\orc,Williams & Wilkins, 1983. 1'. 274.)

42 Chapter 7

Large pyramidalcells of Betz

Motor cortex~Igyrus)

Medulllo

Spftlel eonl

Pons

Medulla

t:::=",. Longitudinal libelS inbasiler portion of pons

, __--Genu 01Internal capsule

'-_--Anteflor limb 01Internal capsule

C'='~---~_

;,------- Ventral corticospinal tract(uncrossed Mons 01 neuron 1)

'-/---+----- Pyramldel decussaHon

..._~ ~;.;~~:::----Ventral wtlite COtllilissure

CNXII--~

CN III

CN VI ----.:!!~~

Lenticular nucleus

Laleral corticospinaltr8C\(crossed !\)lons 01 neuron I)

""""­,,'n

Figure 7-4. TIIC ItIlcrai :md WIllI'..1cOr1ic~llinai (pyr:u1l1.bl) rrm::ts. TI,csc m:ljor Je"cendin~ mowl' r:llh.war~ nwdi:llC \·olillom.1 mow! ;,c,idt~" TI)(" cdl< I,f nli~ir1 arc locall-J in the rremOIOI, the mOlor, :l1ld the ltI."n·..or~' cnrliCCS. CN = cr:m,;,1 nervc. (Rq,ril\l('d wilh J'('nnl~<inll fmm Cmpel1lcr MR, Sutin J: HllIntm Nell'r(l{IIUl!Omy. Baltimorc, WiI]i;lIns & Wilkins, 1983,11.285.)

Traets of !he Spinal Cord 43

Ophthalmic artery

-----'---'t~---::iMedUlla

Middle ear

0.",,,,,,,,,,sinus

/11'----_ eN vLong V-3

ciliary nerve

Inlemal carotid artery

v-

To dilator01_Vessels of face

MuRe(s muscleof eyelid

Sweat g,andslfollace .~.

Subclavlan artery

"''.Y"" Superiorcervical ganglion

EXlemalcarotid artery

':::1--:o--S.:.plnal cord (T·1)

ClliospInal center(In lateral hom)

Sympathetic trunk

Figure 7-5. 1111,' oculosymp.-uhcl1C p.llh"~.ty. Hypollmt:llIllc iibcnol'roJecllo the ipslbteml dlio:>pin.'11 celllerof the intcrmediol:ncr..l cell culumn at T-I. The ciliospinal cemer prOjects preganglionic symp:llhClic iibers rolhc superior ccrviGlI g;mglion. "T1l<- supenor ceryiaol ganglion prOJ<."'Cts reriV;lSCUbr postJ;mglionic sympathetictihcT'$ through the lympantC (:;I\'il\', GI\·cmou;; sinus. and $lll"erior orbit..1hssure to the dilalor muscle of lhe iris.ImcrTllplion of lhis p.'1dl\\~I\':1( :my Ic\'c\ results in Homer's syndrome. eN"" cranial ncr\"l,~.

c. The primary sensory cortex (Brodmann's areas 3. I. and 2)d. Arm, face, and foot areas. The arm and face areas of the motor homunculus

are found on lhe lateral convexitY; the foot region of the mOlOr homunculus isfound in the paracentral lobule (sec Figure 23·2).

2. Termination. The lateral corticospin:ll (r.:Ict tcrmin:ltes contrabter.:llly, throughin[erneurons, un vetllr"l horn motor neurons.

D. Course elf Ihe Inleral corticospinal rmCI

1. Telencephalon. The breml corticospio:ll tr:tct runs in [he pDSt('rior Iimbofrhe in­ternal capsule in the telencephalon.

2. Midbr.lin. The b[er.:ll corticospinal tract runs in the middle threl"-fifths of the cruscerdlri in the miJbr.:lin.

3. Pons. TIle latcr.:I1 corticospin,,1 rr.:lCI nlllS in the base of the pons.

4. Medulla. TIle lateml corticospin:ll tmct runs in the mcdulbry pyramids. Between85% and 90% of the corticospinal fibcrsdeeussate in [he pymmid:ll decuss...tion asthe l:ul"r.:Il corticospinallr.:lcl. TIle rctl\:lining 10% to 15% of Ihc fibers continueas the :tnterior corticospinaltr:tC1.

5, Spinal cord. The I:ueml cortico:;pinaltr.lcl runs in Ihe dors...1quadram of the I:n·eral funiculus.

44 Chapter 7

E. Transection of the later-II corticospinal tract

1. Above the motor decussation. [F.msccrion resllhs in comralater.:ll spastic paresisand B:lbinski's sign (llpgoing we).

2. In the spinal cord, transection rl'Sults in ipsilatcral spastic paresis anJ Babinski'ssign.

V. HYPOTHALAMOSPINAL TRACT (Figu~ ).;)

A. Anatomic location. The hYPOlhalamospinal tmct projects withoot interruption fromthe hypothalamus to the ciliospinal center of the intennediolareral cell column at T­I to T·2. h is found in rhe spinal CON at T·l or above in the dorsolateral quadrant ofthe lateral funiculus. It is also foond in the lateral tegmentum of the medulla, pons,and midbrain.

B, Clinical features. Interruption of this tract at any level results in Horner's syndrome(i.e., miosis, ptosis, hemianhidrosis. and app.1rent enophthalmos). The signs are al­ways ipsilmeral.

8Lesions of the Spinal Cord

I. DISEASES OF THE MOTOR NEURONS AND CORTICOSPINAL TRACTS (F;g.ures 8-] :mJ 8-2)

A. Upper motor neuron (UMN) lesions ;ITC cause..1 by Imn"t.'<:liun of the corticospinalImet or llcsrmclion of the cunical cdls of on~in. TIlt·y f('~ult in sp.lstic p.lrcl1is wid,l'yrnmiJal signs (Babinski's 5i1->1\).

B. Lower motor neuron (LMN) lesions arc caused hy J.nnaJ,.'(" to rhe mOhlf neurons.They result in flaccid paralysis. ardlexia. mrophy. fa~icul;llillllS.anJ fihrillations. Po­liom~'e1itisor Wcrdnig-Hoffman disease (sec Figure S-2A) f{'slllt~ (rom J:nna,L't' lO rhemulor neurons.

Gracile fasciculus

Lateralcorticospinal tract

Lateralspinothalamic Iract

Ventral while commissure

=

Ipsilaleralloss ollactile discrimination andposition and vibration sensation from leg

Ipsilateral loss ollaetile discrimination andposition and vibration sensation from arm

Ipsilateral spastic paresiswith pyramidal signs

Coolralaleralloss 01 pain and1emperalure sensation onesegment below lesion

Ipsiialeraillaceid paralysis in affected myotomas

Bilateral loss or pain and temperaturesensation within dermatomes of invotved segments

Figure 8-1. Tr:ms\·crsl.' ....>('!ion 01 the (cr\'[c;,l spin:,! cord. The dllllc.llI)· 11l1lx.nam a-ecndllll,; and descend­ing pmhw:,ys llr,' ~htlwn tlfl ll~ le!f. Clinic:ll ddidb thar re~uh Imlll thc mlerrupl K.Ill llllhc:>c Palh"~I)'S an' shownon 111(· righf. C\."ilnlCfi\"c IC'I,'n~ (ll the dn"",l horn~ rt>ulr III mU·~lhc".1and Ill'dlexi,l. Ibln,clion o( duo \"\~Illml

while commissuTC 11l1.'rrul''' rhc centrallr..msrn[,;,.lon of p..in :md tCIll~r.lIure Ill1pl.lbc' h,l,ller..,lly IhfOU!!h lhebrcml sl'lIlurhalamlc ImCI'.

4'

46 Chapter 8

Figure B-2. Cla:<.<ic ksi, '11~ "f Ihc spilwl c,)rd. (A) Puliumyclitis :lnd progrcs.~ivc infantile muscu!:Jr ;]tmphy(Wcrdnig-Ih,ffm;mn di~e;l"Cl. (/3) Mlllliplc .'iClewsis. (C) [xl[i;;11 column discasc (tabes dorsalis). (/)) Amr­otT,'phic hlln:]1 :sckrrkib. (E) Ilcmbcct ion "I the spin;.l c,)rd (Brown-St::qu;lrd syndrome). (F) CtJmplclc vcmmlspin;,l ;lr!cry occlusion "f the -,pill;.l cord. (G) SulJacure comhincd dcgcncr:l\ion (vitamin BIZ Iwur"Iy'lIhy). (/-I)S\,rln!=nmyt:"1i;].

C. CombinL-d UMN and LMN disease. An example of a combined UMN and LMN dis­caS(' is amyotrophic lateral sderosis (ALS, or Lou Gehrig's disease) [S<.'C Figure 8­lDI. ALS is call~d by damage [0 the corricospinal,rncts. with pyrnmidlll signs. and bydamage [Q the LMNs. with LMN symptoms. Patients with ALS have no sensorydeficit:'.

Lesions of the Spinal Cord 47

II. SENSORY PATHWAY LESIONS. An example of a condition causN by these lesionsis dorsal column disease (tabes dorsalis) (see Figure 8-2e(. This disease isset'n in patientswiTh neuro:syphilii. It is charneteri:ed by a loss of tactile discrimination and posirion and\"Ibration sen&1tion. Irritatl\'c in\'olvellll'1l[ of the dors.'ll roots results in pain and pares­thesias. Patiems have a Romberg sign. (Subject stands with his feet logether. When hecloses his eyes, he loses his halance. This is a sign of JOTS..'l1 column ataxia.)

III. COMBINEO MOTOR ANO SENSORY LESIONS

A. Spinal cord hemisection (Brown-Scquard syndrome) (see Figure 8-2E] is caused bydnm:lge TO rhe following structures:

1. The dorsal columns [gracile (Ilog) and cuneate (arm) fasciculi]. Damage resultsin ipsilatcrnlluss of taetile discrimination and position and vibrarion sensation.

2. The lateral corticospinal tract. D.lmaj,.'C results in ipsilateral spastic paresis withpyramidal signs below rhe l{'sh..IIl.

3. The lateral spinothalamic tract. Damage results in cOnlralateralloss of pain andtemperature sensation one segment helow the lesion.

4. The hypothalamospinal tract at T-t and above. Damage results in ipsilateralHorner's s~tndrome (i.e.. miosis. pwsis. hemianhidrosis. and apparent enoph­thalmos).

5. The ventral (anterior) horn. Darn:lge results in ipsilar('ral t1accid paralysis of in­ncrviltell muscles.

B. Ventral spinal artery occlusion (see Figure 8-2F) causes inf:lrction of the :lnter;or two­rhirJs of rhe spinal cord, but spares the dorsal columns and horns. It results in damageto rht, f,)lluwing structures:

1. The lateral corticospinal tracts. Damage results in bilateral spastic paresis withpyramidal signs bEolow the lesion.

2. TIle lateral spinothalamic tracts. Damage results in bilateral loss of pain and rem­perature sensation helaw the lesion.

3. TIle hypothalamospinal tract at T-2 and alxwe. Darna!;:e resulTS in bilateralHomer's synJrome.

4. The ventral (anterior) horns. Dam:lgc results in bilateral flaccid paralysis of theinm'rvarul muscl('s.

5. The corticospinal tr.lcts to the Solcr"l parasympathetic centers at S-l to S-4.D,l1lwgc results in bibtcral d<l1llage imd loss of voluntary bladder and bowelcontrol.

C. Subacute combined degeneration (vitamin 8 11 neuropathy) (see Figure 8·2GI iscaused by pernicious (megaloblastic) anemia. It results from damage to the followingsrructures:

1. The dorsal columns (gracile and cuneate fasciculi). Damage resulTS in bil:ueralloss of tactile Jiscrimination and rosition and \'ibrarion ;;cnsmion.

2. The lateral corticospinal tracts. Damage results in bilateral spastic paresis withpyramidal signs.

3. The spinocerebellar tracts. Damage results in bilateral .mn and leg dystaxia.

D. S)'ringomyelia (sce Figure 8·2H) is a central cavitation of rhe cen'ical cord of un­known ('[iolngy. It res\lhs in d:lmage to the following structures:

48 Chapter 8

1. TIle ventral white commissure. Damage to decuS&"1ting lateral spinothalamic ax­ons cauS\.'S bilateral loss of pain and temperature sensation.

2. The venlral horns. LM lesions result in flaccid pam lysis of the intrinsic musclesof the hands.

E. Friedreich's ataxia has the 5."1me spinal corJ pathol~,yand symproms as sulxtcUle com­bined degeneration.

F. Multiple sclerosis (see Fib'lJre 8-2B). Plolques primaril\' involw the while matter of lhecervical segmenlS of the spinal cord. The lesions are random and asymmeuic.

IV. PERIPHERAL NERVOUS SYSTEM (PNS) LESIONS. An example ofa PNS lesionis Guillain-Barrc syndrome (acme idiopathic JXllyneuritis, or postinfectious polyneuritis).It primaril~' affects the mowr filx-rs of the ventral rootS and peripheralnelTcs. and it pro·duces LMN symptoms (i.e., muscle weakness, ascending flaccid p,lfalysis, and areflexia.)Guill<lin-Barrc syndrome has Ihe following features:

A. It is characteri:ed by demyelination .md cdem.!.

B. Upper cervical roor (C4) involvement and respirarory pam lysis arc common.

C. Caudal crani:ll nerve ill\'okemem with facinl diplegia is prcscm in 50% of cases.

D. Elcv:lted protein Icvcls may GlUS{' j);'lpilledema.

E. To a leSS\:r degree, sensor)' filx-rs arc afk-<:ted. resulring in paresthL'Sias.

F. The protein level in the cerebrospinallluiJ is ele\·atecl. but without pk'OCytosis (albu­minoc)'tologic dissociation).

V. INTERVERTEBRAL DISK HERNIATION is seen:lt the L-4 to L·) or L·) to 5·1 inler­space in 90% ofcases. It appears at thcC-)IOC-6orC-6IOC-7 interspace in 10% ofGtscs,

A. Intervertebral disk herniation consists of prolapse. or herniation. of the nucleus pul­posus through the defective anulus fibrosus and into the vertebral canal.

B. TI\e nucleus pulposus impinges on the spinal roots, resulting in spinal root symptoms(i.e.. p:lrcsthcsias, p.1in. scnsoryloss. hyporellexi<l. and muscle weakness).

VI. CAUDA EQUINA SYNDROME (SPINAL ROOTS L3 TO CO) results usually froma nerve root rumor. an ependymoma, a dermoid tumor. or frOill a lijXlma of the lerminalcord. Is characteri:ed by:

A. Severe radicular unilateral pain

B. Sensory distribution in unilmeral saddle-shaped area

C. Unilaterall1l11scle rltrophy and absl'nt quadriceps (LJ) and ;Ink Ie jerks (51)

D. Incontinence al,d sexual functions are nOt marked

E. Onset gr.ldual and unilateral

VII. CONUS MEDULLARIS SYNDROME (CORD SEGMENTS 53-CO) usually resulrsfrom an intramedullary tumor, e,g, ependymoma, Is characterized by:

A. Pain usually bilateral and nO{ sc\'erc

B. Sensory distriburion in bilateral saddle-shaped ar("rI

C. Muscl(" changes nOt marked: quadriceps and ankle reflexes nomlal

D. Inconrinence and scxual functions sc\'erly impaired

E. Onset sudden and bilaTeral

9Brain Stem

I. OVERVIEW. Tllt' brain stem inciuJes the medulla, pons. and midbrnin. If extends fromtht· pyramidal dccu$S.lfion [0 rhe poslcrior commi.ssure. The "min s[eln recein'S its blo..-,Jsupply from Ihl' \"cnchrobasilar system. h contains cralli,,1 nernos (eN) III to XII (exceptthe srin0l11Y,ln of eN XI). Figures 9-1 and 9-2 sho\\' ilssunacc ,lllillOm)'_

II. CROSS-SECTION THROUGH THE MEDULLA (F;.u'C 9·)

A. Medial structures

1. TIl(' hypoglossal nucleus of eN XII

2. TIle nwdiallemniscus, which l"lllllains ClOSS("J fihcrs from rhe gracile and cunc:uenuclei

3. TIle pyramid Cconico:;:pinal trans)

Third ventricle

Inlerlor cerebellar peduncle

Striae medullaresCuneale tubercle

Gracile tubercleCuneale fasciculusGracile lasciculus

",f

(i;;~ti~t;; "'".-' Lateral geniculate bodyMedial geniculate body

Crus carebri

11\~~s::~s~:uperior cerebellar peduncle. . Middle cerebellar peduncle

Pineal body

Superiorcolticulus

Hypoglossal trigoneVagal tOgene

Inferior coIliculus

Facial colliculus :>.«:'Z;;;;:ttlVestibular area

Figure g..1. The- oofl'al ~lIrf~loCC of Ihe hruin SICIll. Thc three CCf(;hdbr pcJundC's h~we h.-cn rl'l1Ion-J 10 e,,­rose Ihe rhlllnhcml (0I'S.'1. TIle rrnchlcar ncrve is Ihe only nervc 1<, l.'''U Ihl.' hr.lin ~(elll from II\\.' dorsal surface.TI1C filoCi,ll c(llhculu~ surmpun.,; the b'Cnu of lhe f;lei,,1 nerve .111.1 Ihe ahducem nudeu). eN '" cr."li~lll\\.'rve.

49

so Chapter 9

CN VUI

CN XII00ve,-,""-,,

Py<an;dcervical nerve I'-~~rft

Olfactory bulb (CN I)Optic chiasm

~'l'-Olfactory tract

InfundibulumTuber cioereum

\ /"'" ./Mammary body

;s.Q~Optic""'"

CN III

;-=It:=~~r- CN IVCN V (motor root)

P~~~~~~§~J~~~CN V (seo5OfY root)Middle cerebeRar CN VIeN VII

peduncle eN VII rlfllermEKiate)CN VIII

CNIXeNXCNXI

CN II

OlfactOl'y trigoneAnterior perforated

","'Ian<e --"PCInteq:leduncular lossa_E~-

Crus cerebri(cerebfal~)

Figure g..2. TIll: ,'cmrJI surf.-ee of rhe hr:.in stem anJ the all:-ehcJ crnnial IlCn:es (eN).

Hypoglossal nucleus of eN xu

~~~~~~~~:;!.YLInlerlor olivary nucleus

Solilary tract and nucleus

Dorsal motor nucleus 01 CN X -t-;,!..:::::'.:'~

Inferior cerebellar peduncle, ---\-

--W'@Nucleus ambiguus (CN X)

Vestibular nuclei

Hypolhalamospinal tract

Spinal trigeminal nucleus

Spinal trigeminal lract

<:::v,;~t-Spinal lemniscus

CN XII

Pyramid

Medial lemniSC1JS

Figure g..3. Tr.lllSvefSC K'Clioll of the mcJulla al the miJoli"ary level. Thc ,'agal nen:e !crnnial nerve (CN)XI, hytJ'Ol,(loss.:llner...e (CN XII), :mJ vL"S[ibubr ner...e (eN VIII) :nc prominem in this seclion. TIle nucleus am·bigulls giv/:;S risc [0 sp«:ial "isccr:.l cffcrtom iibclS to CN IX, X, anJ Xl.

Brain Stem 51

B. lateral structures

1. The nucleus ambiguus (C IX, X, and XI)

2. The \'estibular nuclei (CN VlII)

3. TIle inferior cerebellar peduncle, which contains the JotS.."l1 spinocerehdlar. cu­neocerebellar, and oli\"(x:erebellar tracts

4. The lateral spinothalamic tract (spinal lemniscus)

5. The spinal trigeminal nucleus and tract of eN v

Ill. CROSS-SECTION THROUGH THE PONS (Figure 9·4). The pons has ;l durs,"lltegmentum and a \'entral base.

A. Medial structures

1. Medial longitudinal fasciculus

2. AbduceOl nucleus ofCN VI (underlies f,Kial colliculus)

3. Genu (iOlcmal) ofCN VII (underlies facial nerw) Ifacml colliculusl

4. AbJucent fibers ofCN VI

5. Medial lemniscus

6. CorricospinClI tract (in the base of the pons)

B. Lateral structures

1. FClcial nudeus (CN Vll)

2. Facial (imraClxiClI) nen'e fibers

3. Spinal trigeminal nucleus and tract (CN V)

4. L"lteral spinothalamic n<lcr (spinal lemniscus)

5. Vestibular nuclei ofCN VIII

6. Cochlear nuclei ofCN VIII

Abductml nucleus (CN VI)

Vestibular nerve (CN VIIl)

Facial nucleus (of CN VII)

Spinal lemniscUS

Foorthventricle

Vestibular nuclei (01 CN VIII)

~ Inferior cerebellar peduncle

\S........\J --J- Spinal trigeminaltract and nucleus

CNVII

Middle cerebeYar pedunde

Medial lemniscus

CNVI

Trapezoid body

Figure 9-4. Tmns\'el'$C section of the pons at the l~ve1 of the rtbdueent nucleus of cmnlal nerve (eN) VI anu[he facial nucleus of eN VII. MLF "" medial longirudln'll fasciculus.

52 Chapter 9

MLF

Spinal lemniscus

Cerebral aqueduct

Superior collic1Jlus

Periaqueductal gray

_ ,~- cerebral pedoode (crus carobri)

ConicospinaJ tract

Red nucleus

Cortioobulbar tract

1'c1-----.f4c"t---\i-OcuIomotor nucleus

CN III

Substantia nigra

Medial lemniscus

Oentatolhalamic tract

Medial geniculate body ",(/::::;""),

Figure 9-5. Tmnsvc('S(" se<:lion of (hc midbrain.n the level of (he supcriOf eoUiculus. oculomoror nucleus oferomi.ll nerve (CN) Ill. .1lK! red nuclcus.l\'ILF = mooiallongiludio..",l fasciculus.

IV. CROSS-SECTION THROUGH THE ROSTRAL MIDBRAIN (Figure 9-5). The mid­brain has a dorsal tectum. an intemlooiate tegmentum, and a base. The aqueduct lies be·tween the rectum and rhe tegmentum.

A. Dorsal structures include the superior colliculi.

B. Tt.-gmentum

1. Oculomotor nucleus (eN III)

2. Medial longitudinal fasciculus

3. Red nucleus

4. Substrlntia nigm

S. Dcntrltorh;llamic tract (crossed)

6. Mcdial1cmniscus

7. Larem I spinothalamic tmct (in the spinallemnisclls)

C. Crus ccrebri (basis pedunculi cerebri, or cerebral peduncle). The corticospinal tr.lctlies in rht, middle three-fifths of the crllS cercbri.

V. CORTICOBULBAR FIBERS (see also Figure 13-4) project bilatcmlly to all motor era­ninl nerve nuclei excepl the facifll nucleus. The division of the (acial nerve nucleus thfltinnervales lhe upper f<lcc ([he orbiculflris oculi muscle and above) receives bilateral cor­ticobulbar input. The division o( the (acial nerve nucleus th:1.t innerv:l.tcs [he lower facereceives only contralateral corticobulbar input.

1.0Trigeminal System

I. OVERVIEW. The trigeminal system provides sensory innervation (0 the face. oral cav­ity. and supratentorial dura through general somatic affcrcnl (GSA) fibers. It also inner­vales the muscles of mastication through special visceral cfferenl (SVE) fibers.

II. THE TRIGEMINAL GANGLION (semilunar or gasserian) conrains pseudounipolar gan­glion cells. It has three di\·jsions:

A. The ophthalmic nerve [cranial nerve (eN) v- I] 1il's in the wall of the c:l\'cmous si­nus. It cmel'S the orbit through the superior orbital fissure and innervates the forehead,dorsum of the nose, upper eyelid, orbit (cornea and conjunctiva), and cranial dura.The ophthalmic nen'c mediates the afferent limb of the corneal reflex.

B. The maxillary nerve (eN V.2) lies in the wall of the cavernous sinus and innervatesthe upper lip and cheek, lower eyelid. anterior portion of the remple. oral mucosa ofthe upper mouth, nose, pharynx, gums, teNh and palate of the upper jaw. and cranialdura, h exits the skull through the foramen rorundum.

C. The mandibular nerve (eN V-3) exits the skull through the foramen O\'ale. Its sen­sory (GSA) component innervates the lower lip and chin. posterior portion of thetemple, external3uditory meatus, and tympanic membrane, external ear. teeth of thelower jaw, oral mucosa of the cheeks and floor of the mouth, anrerior two-thirds of thetOl)gue, tempJromandibular joint, and cranial dura.

D. The motor (SVE) component of eN v accompanies the mandibular nerve (eNV-)) through the foramen 0\'3Ie. It innervates the muscles of mastic:nion, 111ylohyoid,anterior belly of the digastric, and rensores tymp.mi .md veli palatini, It inncn':Hes themuscles that move the jaw, the lateral and medial prerygoids (Figure 10-1).

III, TRIGEMINOTHALAMIC PATHWAYS (Fig"," 10-2)

A. The ventral trigeminothalamic tract mediates pain and temper:lture sensation fromthe face and oral cavity.

1. First-order neursms are located in the trigeminal (gasserian) g:mglion. They giverise to axons that descend in the spinal trigeminal tracr and synapse with second­order neurons in the spinal trigeminal nucleus.

2. Second-order neurons are locatecl in the spinal trigemin... l nucleus. The)· give riseto decuss..'lring axons that terminate in the contralateral ventral posterollll-dial(VPM) nucleus of rhe thalamus.

3. Third-order neurons are locatecl in the VPM nucleus of the thalamus. They pro-

53

54 Chapter 10

Motor cortex -,.:.>

UMN

Superior cerebellar peduncle

Chief sensory nucleus CN V7

'--L

Motor nucleus eN v

Medial lemniscus

Corticospinal tract

lMN

Condyloid PflXesS

4th ventlicle

CNV molor

-\-Poo,

Lateral pterygoid muscle

••·•••••••••,

Figure 10-1. Function and innerv:nion 0( {hc latcral prCtH,'oid musclcs (LPMs). TI1C LPM r('Ccivcs irs in­nervation from rhe motor nucleus of the rril,,'cmin,,l nerve found in thc rosTr;11 JXlns. Bilareral innerv,lIion of rheLPMs results in prorrusion of rhe rip of thc mandible in the midline. TIle LPMs also open the j;III'. Dcn('"rvarionof one LPM results in dC"i:ltion of thc mandiblc £0 the ipsihllcnll or wcak side. The trigemin"llllofOr nuclellSreceives bilarer,ll corticobulb:lr input. eN = cmnial nerve; LMN = lower motor neuron: UMN = upper motorneurOll.

jcct through the posterior limb of thc internal capsule to the face area of the s0.­

matosensory cortex. (Brexlmann's areas 3, I, and 2).

B. The dorsal trigeminothalamic tract mediates tactile Jiscrimination and pressure sen­s.."1tion from the fuce and oral cadty. It receives input from Meissner's and Pacini's cor­puscles.

1. First-oroer neurons arc located in the trigeminal (gasserian) ganglion. Theysynapse in the principal sensory nucleus of CN V.

2. Second-order neurons are located in the principal sensory nucleus ofCN V.They project to the ipsilateral VPM nucleus of the thalamus.

Trigeminal System 55

Internal capsule(posterior limb)

- - - • Dorsal IrigeminothaIamic tract

~~~~'Caudatenucleus

~~~~

Ventral posteromedial' "f.J~~r?1I~nucleus of thalamus,

Yeotraltrigeminothalamic tract - - - -

Face area ofpostcentral gyrus -.. -r:'!!i"",,i:!

MotOf branch of CN Y·3

5enSOl'y branch of CN Y-3

, ,• Spinal trigeminaltraet

5eoSOl'y branch of CN Y·2'0-4>7

, Principal senSOl'y nucleus of CN Y

/ / 5eosory bfanch of CN V-',,

'" Mesencephalic nucleus of CN Y,,,,,

/,Spinal trigeminal nucleus /

Pons

Midbrain

,Motor nucleus of CN Y /

Spinal cord

Figure 1()'2. TI1C ventral (p;lin lltld temper-,lfurc) and dOl'$.11 (discrimin:uive lOuch) trigcminoth;ll~lInicplllh­wuys. eN '" cr.lllial nerve.

3. Third-order neurons are loc,ned in the VPM nucleus of the thalamus. Theyproject through the posterior limb of the internal capsule ro the bee areaof the somatosensory eonex. (Brodmann's areas 3, I, and 2).

IV. TRIGEMINAL REFLEXES

A. Introduction (Table 10-1)

1. The corneal reflex is a consensual disynaptk reflt'x.

56 Chapter 10

Table 10-1.The Trigeminal Reflexes

Reflex

Comeal reflexJaw jer1l.Tearing (lacrimal) reflexOCulocardiac reflex

Afferent Umb

Ophthalmic nerve (CN Vol)Mandibular nerve (CN V-3)*Ophthalmic nerve (CN V-lOphthalmic nerve (CN Vol)

Efferent Umb

Facial nerve (CN VII)Mandibular nerve (CN V-3)Facial nerve (CN VII)Vagal nerve (CN X)

•The cell bodies are found in the meseocephalic nucleus of CN V.CN ... cranial nerve.

2. The jaw jerk reflex is a monosynOlptic myotatic reflex (Figure 10.3).

3. The tearing (lacrimal) reflex

4. The oculocardiac reflex occurs when pressure on the globe results in bradycardia.

B. Clinic.ll corrchuion. Trigeminal neuralgia (tic douloureux) is chataclerizeJ by recur­n::nt P:lrox~'sms of sharp, Slabbing pain in one or more hranches of the trigeminal nl'n·l'on one siJe of Ihe face. II usually occurs in people older than 50 years uf age, and it ismote common in wumen Ihan in men. Carbama:epine is the drug of choice for idio­pathic trib'Cminal neuralgia.

MOIOr nucleus CN Vwith secondary neuron

Mesencephalic nucleuswith primary neuron

V-3

Muscle spindlefrom masseter muscle

Masseter muscle

L-----Motor division CN V

Principal sensory nucleus of CN V

Spinallrigeminal nocleus

Agure 1Q..3. Th(" ,a"" lerk (m.:lSSClCr) reltex. 11,e ..ffercnt limb is V·3, and the efferem limb is the IllO(Ot rt)(l(

lll:1( accofllp<lllies V·3. Fi~t-t)rJcr SCI'lSOf't' neurons arc Ioc:lll-J in the mesencephalic nucleus. The jaw jerk reflex,like all muscle stretch rt:flcxe.., I.S <Illlonosptaptic m~·or.tCtK rcilex. HnJCITctlexia indicates an upper mor:or nctl­rtln lesion. eN = cr:mial nen·e.

Cavernoussinus

Pituitary gland(hypophysis)

Infundibulum

Trigeminal System 57

Optic chiasm

Intemal carotid ar1ery

Anleriorc~noid process

CN III

1~!r--CN1V

'.),1,..-- CN V-I

tii--=--l!,--_ CN VI and

postganglionicsympalhelics

CN V-2

Agure 10-4. TIle CContents of thl' c:,,·cmous sinus. TIle wall of the (;l\'emotl~~lIlUS contains the ••phlh:tlmiccmni:llncr...c (CN) V-I and maxil1,lry (CN V·2) di\'isions of the trib'Cminal nl'l"\·l' (CN V) and the trochl~':lr

(eN IV) and oculomotor (eN HI) nel"\·c.~. The siphon of tile imern,ll carotid artery :mJ thl" :11>.. lu«'nt ner...e (CNVI), along with IXJSt~allulionic s~'mpmhetic fibers, lil-s within the C""'emotIS ShIll',

v. THE CAVERNOUS SINUS (Figure 10-4) contains th<.- following :>!TlIClureS:

A_ Internal C:lrotid :lrlery (siphon)

B. eN III, IV, V_I, V-2, ,md VI

C. Postganglionic sympathetic fibers en route to th: orhit

58

1.1.Auditory System

I. OVERVI EW. The 3udiwI)' system is an exteroceptive special somatic ,,((crem system thatcan derecr sound frequencies from 20 H: to 20,CXX) H:. h is dcri\"ed from the otic veside,which is a derinlth'c of the otic placode. a thickening of the surface ectoderm.

II. THE AUDITORY PATHWAY (Figure 11-1) consists of the following structures.

A. The hair cells of the org.m of Corti are innervated by the peripheral processes ofbipo­Jar cells of the spiral ganglion. TIley are stimulated by vibrations of the basilar membrane.

1. Inner hair cells arc the chief sensory elements; they synapse with dendrites ofrn}'elimued neurons whose axons comprise 90% of the cochlear nerve.

2. Outer hair cells synapse with dendrites of unmyelinated neurons whose axonscomprise 10% of the cochlear nerve. The OHCs reduce the threshold of the IHCs.

B. The bipolar cells of the spiral {cochlear} g.1nglion projecr peripherally [Q the hair cellsof the 0'l."'n ofConi.1l1ey projCCI centrally as [he cochlear nerve ro [he cochlear nuclei.

C. The cochlear nerve [cranial nerve (eN) VIII] extends from the spiral ganglion tothe c("rebelloponrine angle. where it emers the brain Slem.

D. The cochlear nuclei recei\'e input from the cochlear nerve. They projccr comralater­ally to the superior olivary nucleus and larerallemniscus.

E. The superior olivary nucleus, which plays a role in sound localization, receives inputfrom the cochlear nuclei. It projects to the lateral lemniscus.

F, The trapezoid body is located in the pons. It contains dccussaling fibers from the ven­nnl cochlear nuclei.

G. The laternllemniscus rece yes input from the contralateral cochlear nuclei and supe­rior olivary nuclei.

H. The nucleus of inferior colliculus receives input from the lateral lemniscus. It pro­JCCtS through the brachium of the inferior colliculus to the medial geniculate lxxIy.

I. The medial geniculate body receives inpul from the nucleus of inferior colliculus. hprojects through the internal capsule as the auditory radiation ro (he primary auditot')°conex. rhe trnns\'crse temporal gyri of Hesch!.

J. The transverse temporal gyri of Heschl contain the primat')' auditory cortex (Brod­mann's areas 41 and 42). The gyri are located in the depths of the lateral sulcus.

III. HEARING DEFECTS

A. Conduction deafness is caused by internlption of the passage of sound waves throughthe external or middle car. It mOlY be caused by obstruction (e.g., wax), otosclerosis,or otitis media.

Auditory System 59

Nucleus of inferior coIiculus

Intemal capsule

Caudate nucleusThalamus

M""'" --k--

Putamen:JLentifOfTTl nucleus

~t:kfiir1~~GlobuSpallidu'i. Transverse gyrus

~~:J~~~ of temporal lobe

f..--- AuditOfY radiations in sublenticularpart of internal capsuleBrachium 01 ----Medial genic\lIate body

inferior coIliculus -----cP-1~5~;===--Commissure 01~ inferior coIIiculus

<l:P------LaterallenvVscus

(jtc:=~;fl>-------Nucleus and commissureollateraJ IerTlliscus

Tectorial membrane

Hair cells

Spiral ganglion

Cochlear nerve (CN VIII)

Superior

olivary nucleus --'::S1~~;;;~~

Dorsal and ven""':'-"--I-Ci,-tj-,cochlear nuclei

Trapezoid body

Pyramidal tract

Base of pons

Figure 11-1. Periphcwlllnd centrol connections of the auditory system. TIl is syStem nriS(.·s from t he h:lir cellsof Ihe organ of Coni :md tcrminates in the transverse Icmpoml gyri of I-lcschl of the superior lempor.IIl;)'nlS. Itis chamctcrited by the bi1:lter.l1ity of projections nnd the lOnOlopic locnlimtioll of pilch ,If ;llllc\·c\s. For exam­ple. high pitch (20,000 I-h) is loc,llilcd ,It the b,ISC of the cochlca and in the pnstcromedi,]l p,lrt of the tmnsvcrsetcmporol gyri. eN "" emni,]1 nerve.

B. Nerve deafness (sensorineural, or perceptive. deafness) is causc<1 by disease of thecochlea. cochlear nerve (acoustic neuroma), or cenrral <luditory conncClions. It is usu­ally caused by presbycusis that results from degenerative disease of the organ ofCortiin the first few millimeters of the bas.11 coil of the cochlea (high-frC<luency loss of4tJ00.-8000 H,).

IV. AUDITORY TESTS

A. Tuning fork tests (Table 11-1)

60 Chapter 11

Table 1.1.-1.Tuning Fork Test Results

otologic Anding

Conduction deafness (left ear)

Conduction deafness (right ear)

Nerve deafness (left ear)Nerve deafness (right ear)Normal ears

Weber Test

Lateralizes to left ear

Lateralizes to right ear

Lateralizes to right earLateralizes to left earNo laterlization

Rinne Test

BC > AC on leftAC > BC on rightBC > AC on rightAC > BC on leftAC > BC. both earsAC > BC. both earsAC > BC. both ears

Cooduction deafness'"' middle ear deafness (e.g.• otosclerosis. otitis medial: nerve deafness'"' sensorineural deaf­ness (e.g., presbycusis: AC '"' air conduction: BC = bone conduction.

1. Weber's test is perf,)rmcd by placing:l vibrating tuning fork on the vertex of theskull. Normally, a patient hears ('qunlly on lx)[h sides.a. A pntiellt who h;lS lInihlleral conduction deafness hears the vihration more

loudly in thc affectloJ car.b. A patient who has unilateral partial nerve deafness hears the vibration more

loudl)· in Ihe normal car.

2. The Rinne test compares air and bone conduction. It is pcrformcd by placing a vi·brating lUning fork on the mastoid process ulltilthe \'ibration is no longer heard;Ihen the fork is hdd in front of the car. Nonnally. a patient hears the vibration inIhe air aftcr bonc conduction is gone.a. A patient who has unilateral conduction deafness docs nOI hear Ihe \'ibra­

tion in the air after bone conduclion i:. gone.b. A pat ient who has unilateral partial nerve deafness hears the vibmtion in Ihe

air aftcr hone conduction is &'One.

B. Brain stem auditory c\'oked potcntials (BAEPs)

1. Testing method. Clicks arc prescmcd to one car. then to the other. Scalp ek'(:·trodes and :l computet genet::ltl' a scties of sc\'en wa\"(~s. The waves arc associalOOwilh specific areas of the :ludiwly p:uhw:l)'.

2. Diagnoslic value. This method b valuable for diagnosing brain S!<.'1ll lesions (mul~

tiple sclerosis) and ,x.mcrior fossa wmms {acoustic nellromas).lt is also useful forassessing hen ring in infants. Approximatcly 50% of pnticms with multiple sclcro·sis have ;lbnorl11:11 BAEPs.

:1.2Vestibular System

I. OVERVIEW. Like the <luditory system, the vestibular system isdcrivcd from the otic vcsi~

cleo The otic vesicle is a derivative of the otic placode, which is a thickening of the sur,face ectoderm. nlis system maintains posture and equilibrium and coordinates head andeye movements.

II. THE LABYRINTH

A. Kinetic labyrinth

1. Three semicircular ducts lie within the three semicircular canals (Le.. superior,latcml, and posterior).

2. These ducts respond to angular acceleration and dei:e1eration of the head.a. They contain hair cells in rhe crista ampullaris. The hair cells respond to en­

dolymph flow.

EnoolymphalicI duet

.Ampulla/ / and crista

..- Utricle","" I and maCtJla

,, ,\ Cochlear duet,Saccule and macula

5emicircular ducts•\'" ',,,,, ,, ,,

,, ,L.. Vestibular nerve and

ganglion in intemalauditory meatus

- Carebello­pontine angle

,'PyramidMedial Iermiscus I

Inferiorolivarynucleus- ---

MLF.

Vestibular ~'~'~~~~~~~~~~6oodei .,-'-;~__'~,"S--': - I FJoccuIus

,Inferior \ - - -Juxtarestilonn

cerebellar 00 bodypeduncle· .--

Figure 12-1. Peripheral connections of [he \-est:ibolar s~~em_ The h.'1ir cells of [he crumc ampullares andthe 1113CUbe of [he utriclc and So"lCCule projen, through [he \'f,'sribolar nerve, to the vC5tibular nuclei of (hemedulla and pan;; and [he tlocculonodular lobe of [he cerebellum (\'Wibulocerebellum), MLF '" mediallol\gi­[udinal fasciculus.

61

62 Chapter 12

b. EnJolymph flow W\\';lrd the :'llllpulla (ampullopcrnl) or utricle (\ltriculopcrol)is a smmb'Cr stimulus th:'ln is endolymph flow in rhe op(X)Sirc direction.

B. Sialic labyrinth

1. The utricle anJ s"lccule rcspunJ to the position of the head with respeet 10 linearaccelcr.nion and the pull of gr:wity.

2. The utricle and sacculc contain hair cells whosc cilia arc embc...IJl'{l in themolirhic 111l."mhmne. Whcn hair cclls ;"Ire bent tuward the longest cilium (kinneil.illlll), the fr ....quency of sensory Jischarge incr....ascs.

III. THE VESTIBULAR PATHWAYS (Figllre's 12-l and 12-2) consisrof the followingstruc­HIres.

A. Hair cells of Ih .... scmicircular dUCIS, s.1ccule. and utricle are inncrv"ul,J by periph­eml proceSSl-'S of bipohlr cells of the "cstibubr ganglion.

Vestibular area ofcerebral COl1ex ---~

(~~~~1:-:~;;-r_~-"l<~~- ThalamusVentral posterior >;

inftlrior nucleus ----'j.~

Veslibulothalamic tracts

M<bam ----------<{,.-"

Abducent nudeusof eN Viol pons

MLF

--0;--'=\;';-- Nodulus of cerebellumMLF

I..-,;;;:'::.<'::=---- Vestibular ganglion

MLF-+~I

JuxtareSliform body -_/ _~-\1d1J1.1

Vestibular nuclei

<jf--- lateral vestibulospinal (Deiters') tract

Figure 12·2. TI1C" major ccncral conneclions o( lhc ,"c~cihubrsyslem. VC'Slihular nuclei projen. chrtlu!:h chea,ocl'nJing llll'l.lialiongillidinal (:HICiellll (MI-F), til (he ocubr lIl,nor nuclei anJ ~uhscr,"e \"eslibulo-ocubr rdlcxes,Ve~c ihul:.r Iluc!e'i al.... ' pr,'jccl. chrou!:h Ihe descendlllg MLF ;Ind ];ueml \'cstiblllo>pinal tmclS, to Ihe ,"emr,11 h, ,mIll< 'I, 'r IlCl,r"n.< ,,( Ihe ,pin,,1 CNd ;,nd 111('-li;lIe tX.l$tur.,1 rdlexe~. eN = cwni;ll nerve.

Vestibular System 63

B. The veslibular ganglion is iocared in the fundus of the infernal au<litory meatus.

1. Bipobr neurons project through their peripheral processes to the hair cells.

2. Bipolar neurons project their central processes as thc \'cstibubr ncr\·c !cranialncrve (CN) Villi to the \,c:>tibular nuclei and to the l1occuloncxlubr lobe of thecerebellum.

C. Vestibular nuclei

1. These nuclei receive input from:a. The semicircular ducts. s.."1ccule, and utricleb. The l1occulonooular lobe of the cerebellum

2. The nuclei project fibers to:a. The l1occulonooular lobe of the cerebellumb. CN III, IV, and VI through the medial longitudinal fasciculus (MLF)c. The spinal cord through the laternl \'estibulospinal tractd. The \·entral posteroinferior and posterolat'cral nuclei of the thalamus, both of

which project to the postcentral g)TUS

IV. VEST1BUlG-OCULAR REFLEXES arc mediated b)' the \·cstibular nuclei, MLF, ocularmOtor nuclei, and CN III, IV. and VI.

A. Vestibular (hori:ontal) nystagmus

1. The fast phase of nystagmus is in the direction of rotation.

2. The slow phase of nystagmus is in the opposite direction.

B. Postrotatory (hori:ontal) nystagmus

1. The fast phase of nystagmus is in the opposite direction of rotation.

2. TIlC slow phase of nystagmus is in the direction of rotation.

3. Thc patient past-points and falls in thc direction of previous rot<ltion.

C. Caloric nystagmus (stimulation of hori:ontal ducts) in normal subjects

1. Cold water irrigation of the external audito!)' meatus results in nystagmus to theopposite side.

2. Warm water irrigation of the external auditory meatus rcsuhs in nystagmus to thesame side"

Normal conscious subject Bralnstem intact MlF (bilateral) lesion Low brainslem lesion

Figure 12·3. Cold C:lloric responses in the unconscious patien!. When the br:.lin ~tem i~ inmcl, the eycs de·viate to"~lrd the irrigated ~ide; with bilateral transection of the mcJiallongilUdin;11 fasciculi ('\'ILF), the eye Jc.viau:$ 10 Ihe abducted ~ide. DesInICtion of thecaudal brain stem rcsuhs in no deviation of the e)"cs. l)(mbk·hetidedarJ"O\.l'S indicate nysugmus; single-headed arJ"O\.l'S indicale deviation of the e)"cs to one Side.

64 Chapter 12

3. Remember the mnemonic COWS: Cold Opposite, Warm Same.

D. Test resulrs in unconscious subjects (Figure 12.3)

1. No ll\,smg-mus is secn.

2. When rhe brain stem is intact, there is deviation of the eyes to the side of the coldirrigation.

3. With bilateral MLF transection, there is deviation of th" alxl.ucting eye to the sideof the cold irrigation.

4. With lower brain stem damage to the vcstibular nuc1('i, there is no deviation of the"res.

1.3Cranial Nerves

I. THE OLFACTORY NERVE, the first cranial nerve (eN I) [Figure 13-11, mediates ol­faction {smell).lt is the only sensory system th:\[ has no prcconical reby in the ,hal;lllllls.The olfactory nerve is a special visceral afferenr (SVA) nerve. It consists of unmyelinatedaxons of bipolar neurons that aTC located in the nasrll mucosa, the olf,ICtory epithelium. Itenters the skull through the cribriform plme of the ethmoid bone (sec appendix).

A. OlfacTory pathway

1. Olfactory r«eplOt cells are firsl-ordcr neurons that project to the mitral cells ofthe olfactory bulb.

2. Mitral cells are the principal cells of the olfactory bulb. They are excitawry andglurnminergic. They project through the olfactory tract and lateral olfactory striato the primary olfactory cortex and amygdala.

OIfaetOf)' td) (CN I)CN II Optic chasm

---''-OIfactOf)' tractOlfactory trigone Infundibulum

Anterior perfOO'~"",t"""'-74,1~,';;T uber cinereumsubstance - Mamiflary body

Interpeduncular fossa Optic tract

Crus cerebri CN til(cerebral peduncle) eN IV

CN V lmotor root)

;~on~'~~~~~~i~~~~~CN V sensory root)CNVI

Middle cerebellar CN VIIpeduncle CN VI1 (inlellTlediale)

eN VIIICNIXCNXCNXI

Agure 13-:1. The base of the brain "'jrh anac.hed cranial nerves (eN). (Reprinted "i[h renmsslOl'l fromTmex Re, Kellner CEo Detailed Adas of l~ HeM ond Neck. New York, Oxford University Press. 1958, p. 34.)

.5

66 Chapter 13

3. TI,e primary olfactory cortex (Brodmann's area 34) consists of the piriform cor­tex dKI[ O\'erlies the uncus.

B. Lesions of the olfactory pathway result from trauma {e.g.. skull frncture) and. often,from olfactory groove meningiomas. ThC5t' lesions cause ipsilateral anosmia (Iocali~­

ing value). Lesions that invoke the (XlrahippocalllJXlI uncus may cause olfuctory hal­lucinations luncinate fits (sei:ures) with deja \·ul.

C. Foster Kennedy syndrome (FKS) consists of ipsilateral anosmia, ipsilateral optic atro­phy, and contrahneml p<!pilledema. It is usually cause<1 by an anterior fossa meningioma.

II. THE OPTIC NERVE (CN II) is a special somatic afferent (SSA) nerve that subscrves vi­sion and pupillary lighr reflexes (afferent limb) (see Olaprer 191. It is nor a true peripheralnerve, but is a tract of rhe diencephalon. A tmnsccro...-d optic nerve canoot rq;,>enerare.

III. THE OCULOMOTOR NERVE (CN III) isa general somatic efferent (GSE). b>eneral vis­ceral efferent (GVE) nen:e.

A. General characteristics. The oculomOlor nelYC moves the eye, constricts the pupil,accommodates, and converges. It exits rhe bmin stem from the interpt.-duncular foss.."1of rhe midbrain, paSSt.-"'S through the ca\"cmous sinus. and enters the orbit through thesuperior orbital fissure.

1. 111e GSE component arises from the oculomo{Qt nuclell3 of the rostral miJbmin.It innervates four extraocular muscles and the levator palpebrae muscle. (Re­member the mnemonic SIN: superior muscles are intoners of the globe.)a. TI,e medial rectus muS(;le adducts thc eye. With irs opJXlSire parmer, it con-

verges the eyes..b. 11,e superior rectuS muS(;le elel'ates. intorts, anJ adducts the eye.c. 11,e inferior rectus muS(;le Jepresses, cxrorts, and adducts the eye.d. 11,e inferior oblique muscle elevates. extorts, and alxlucrs the eye.e. TI,e levator palpebrae muscle e1e\'ates the upper eyelid.

2. The GVE component consists of preganglionic p:lfasympathetic fibers.a. TIle Edinger-Westphal nucleus projects preganglionic parasympathNic fibers

to the ciliary ganglion of the orbit through CN III.b. The ciliary ganglion projects postgangliollic p:lrasrmpathetic fibers to the

sphincter muscle of the iris (miosis) and the ciliarr muscle (accommodation).

B. Clini..:al correlation

1. Oculomotor paralysis (palsy) is seen with transtentorial herniarion (e.g., rumor,subdural or epidural hemawma).a. Denervation of the levator palpebrae muscle causes ptosis (i.e... drooping of

the upper eyelid).b. Dcnervation of the extraocular muscles causes the affect\·d eye to look "down

and om" as a result of the unopposed action of the lateral recrus alld superioroblique muscles. TIle superior oblique and lateral rcctus muscles are inner­vated by CN IV and CN VI, respecrivcly. Oculomotor palsy results in diplopia(double \'ision) when dle patiem looks in the direction of rhe parNic muscle.

c. Interruption of parasympathetic innervation (internal ophthalmoplegia) re­sults in a dilated. fixed pupil and p<"1ralrsis of accommodation (cycloplegia).

2. Other conditions associated with eN III imp."1irmenta. Transtentorial (uncal) herniation. Increased supratelltorial pressure (e.g.,

from a tumor) forces the hippocaJ1\p<!luncus through the temorial notch andcompresses or stretches the oculomotot nen·e ..

Cranial Nerves 67

(1) Pupilloconstrictor fibers are affected first, resulting in ~ dilatt.-d, fixed pupiL(2) Somatic efferent fibers are affected later, resulting in external strabis·

mus (exotropia).b. Aneurysms of the carotid and posterior communic:uing aneries of[('n com­

press CN III within the cavernous sinus or imerpe·dllncul:u cistern. They usu­ally affect the peripheral pupilloconstricror fibers first (e.g., uncal herniation).

c. Diabetes mellitus (diabetic oculomotor palsy) often affects rhe oculolllotornerve. h damages the cemrnl fibers aocl sjXlrcs rhe pupil1oconstricwr fibers.

IV. THE TROCHLEAR NERVE (CN IV) is a GSE ncrve.

A. General characteristics. The trochlear nerve is a pure mOtor nl'rvt' that innt'rvates thesllperioroblique muscle. This muscle depresses, intons, and alxluclS the eye. (Sce Rg­ure 17·40.)

1. It arises from the comral:neml trochlear nucleus of the caudal midbrnin.

2. It decussates beneath the superior medull~ry velum of tht' midbmin and exits thebrain stem on irs dorsal surface, caudal to the inferior colliculus.

3. It encircles the midbrain within the subarachnoid space, passes through the cal"emous sinus, and enters the orbit through the superior orbital fissure.

B. Clinical correlation. CN IV paralysis resulrs in thl' following conditions:

1. Extorsion of the e)'c and weakness of downward ga:e

2. Vertical diplopia, which increases when looking down

3. Head tilting 10 compensate for extorsion (may be misdiagnosed as iJiopalhic tor­ticollis)

4. Head trauma. Because of irs course around the midbmin, the trochlear ncrye ispanicularl)' vulnerable to head trauma. The trochlear dl'CUS$..'l1 ion underlies the su­perior medullary velum. Trauma at this site often results in bilateral founh-nen'cpalsies. Pressure against the free border of the tentorium (herniation) may injurethe nerve.

V. THE TRIGEMINAL NERVE (CN V) isa spedal visceral efferem (SVE), general somatic~ffcrent (GSA) nerve (sec Chapter 10).

A. General characteristics. The rrigemin~l nerve is the nerve of pharyngeal (brachifll)arch 1 (1ll~ndibular). It has three divisions: ophthnlmic (CN V-I), maxillary (CNV.I), ~nd mflndibular (CN V-3) Isee Chapter 101. ./

1. The SVE component arises from the motor trigeminal nucleus rhat is found in theIater:11 midpontine tegmentum. Ir innervates the muscles of mastic.ltion (i.e .•tempomlis, m~sseter, lateral, and medi~l prerygoids), rhe tensores tympani and velipalatini, the m)'elohyoid muscle, and rhe anterior belly of the digastric muscle.

2. 111e GSA component provides sensory innervation to the face, IllUCOUS membranesof the nasal and oral cavities and frontal sinus, hard p~[ .. te, and dccp stnlctures ofrhe head (proprioception from muscles and the temporomandibular joint). It inner­vares rhc dum of the amerior and middle cranial fOSSo'le (suprntentorial dura).

B. Clinical correlation. Lesions result in the following neurologic deficits:

1. Loss of general sensation (hemianesthesia) from the face and mUCO\b membranesof the oral and nasal cavities

2. Loss of the corneal reflex (afferent limb, CN V.I) (Figure 13·21

68 Chapter 13

Primary neuron

Principal sensorynucleus (eN V)

q~V.2~ V-3

V·3 (motor)

CNVII

~~fo.'"

,o~•.~:...<=----..<P' --

~:::::;:---------- -- .Secondary neuron

Spinallrigeminal nucleus

$pinal trigeminal lracl

Trigeminolhalamicpain liber

Facial nudeus

Genu eN VII-;,_.::.

Decussatingcorneal renex fiber

Figure 13-2. 11K: (nnw:.l rdlc:< pmhw;'\y ~ho....ing the Ihlce neurons :md Jeeuss.:.nion. 111ls rcllCl< is Ct)llSC'Il­

'tl,ll. IIh· rhe pUllill,lry [,gill reflex. Second-order p;-ain neurons :m~ f'lI.m,1 in rhe c:m..!:J1 divblon of till,' .'l'in:,1tril;"IIL1nal nudC\l~. So.:.octJ'l<.I-'JI"OCr CUnIcal reticle nCU!\)lb ;Irt: ("und;1( more r""lmllc\'ds.

3. Flaccid paralysis of the muscles of masticmion

4. Dc\,jation of the jaw to the weak side as a fesult of the UIlOppOSCJ action of lhe"Pl't)sitc later.11 pterygoid muscle

5. Paralysis of the tensor tympani muscle. which leads to hypoacusis (pani"t dc'lf·ness to low-pitched sounds)

6. Trigeminal neuralgia (tic douloureux), which is characterized by recurrent parox­ysms of sharp. stabbing pain in one or more branches (If the navc (sec Chaptcr (0)

./General characteristics. The abducent nerve is a purc GSE nerve that innervates theblt::r;ll r('ClllS muscle. which alxlucts the eye.

1. It ariS{'s from the alxlucent nucleus that is found in lhe dorsomC(lial tegmentum ofthl' caudal pons.

2. Exiting intraaxial fibers pass through lile corticospinal tracr. A lesion results in al~

ternating abducent hemiparesis.

VI. THE ABDUCENT NERVE (CN VI)

A.

3. It passes lhrough ,he pontine cistern and c:",ernous sinus :lIld emers the orbitthrough the superior orbiTal fissure.

B. CliniC'I! correlation. eN VI paralysis is the mOSt common isolated pals~t lhat resuhsfrom I he long I~ripheral course of ,he nerve. It is seen in patientS with meningitis. Sl.lb·arachnoid hemorrhab't'. late-stage syphilis. and tT:luma. Abducent nerve paralysis reosuits in the following defects:

Cranial Nerves 69

1. Convergent (mt-odiall strabismus (esotropia) with inabiliry to alxlucr rhe eye

2. Hori:ontal diplopia with maximullI scpararion of the Jouble images when look­ing toward d,e paretic lateral rectus muscle

VII. THE FACIAL NERVE (CN VII)

A. General characteristics. The facial nerve is a GSA, general visceral afferent (GVA),SVA, GVE, and SVE nelTC (Fib'llreS 13-3 and 13·4). It mediates facial movements,taste, s.,livation, lacrimation, and general sensation from the external car. It is thenerve of the pharyngeal (brachial) arch 2 (hyoid). It includes th(' facial nerve proper(motor division), which contains the SVE fibers that inner""te the muscles of facial(mimetic) expression. C 1 V)I includes the imennediate nen:c. which contains GSA.SVA. and GVE fibers. All first-order sensory neurons are founJ in the geniculare gan­glion within the temfXJral bone.

1. Anatomy. The facial nerve exirs the bmin stem in th(' cerebellopontine angle. Itenters the imernal auditory mearus and the facial canal. h then exits the facialcanal and skull through the stylomastoid foramen.

2. TIle GSA component has ce\l1xxlies locared in the geniculate ganglion. It inner­vates the posterior surface of the external ear through lh(' posterior auricularbranch ofC VII. It projecrs cemrnll)· to lhe spinal rrigcminaltract and nucleus.

3. TIle GVA component has no clinical significance. The cdl hodies arc located inthe geniculate ganglion. Fibers innervate the soft palare and the adjacent pharyn­geal wall.

4. TI,e SVA component (taste) has cell bodies locared in the geniculate ganglion. II

......... Motor root nerve 01 CN VIIIn stylomasloklloramen

CN 11

lacrimal gland

Pterygopalatine ganglion

Nasal andpalatine glands

Tongue(taste. anteriortwo-thirds)

Ungual nerve ---j;

Submandibular ganglion

Sublingual gland

CN V-2

CN V·3

CN V-1

Stapedialnerve

Trigeminal ganglion

Major petrosal nerve

Superior salivatorynucleus (GVE)

I>I~I-Motor nucleus of CN VII (SVE)

Nucleus 01 solitary tract

Solitary lract (SVA)

Agure 13-3. TIle functional components of the f'lei:.1 nerve Icrani;l1 ncl'\'l,' (eN) VIII.

70 Chapter 13

UMN lesion 01COIticobulbar tract --<iel>(e.g.• stroke ofinternal capsule) Facial nudeus of pons

Upper lace division

lower face division

"-J~- LMN lesion 01 eN VII(e.g.• 8elrs palsy)

Orbicularis oris ------1,<

Muscles oIladal expression: r-~...... "

Frontalis -----+f----,,- ~\

"""",.ris_OOU_';_----'.+_~)I~Buccinator

(~)

Platysma-------1\ J l

Figure 13-4. Cmicobulbar innervation of the f.lcial nerve [crnnial nerve (eN) VIII nucleus. An upper mo­tor Ilcur,m (UMN) lesion (c.g.. stroke involving the imernal c;lpsule) results in COt1lr;llilleml ,,·e;lkne.s:; oi theluwer iacc, with sparing o( the uPlx'r face. A lower motor neuron (LMN) lesion (e.g., Bcll'.~ p;ll~y) rcsuhs in raral­\'sis ur' thc fnci:d muscles ill both the upper and lower (iICC.

projects centrally to the solirary tr:lCt and nucleus. It innervntes the taste buds fromthe :It\terior two-thirds of the tongue through:a. The intcrmediale nerveb. The chorda tympani, which is loc:ued in the tympanic cavity medial to the

tympanic membrane and malleus. It comains the SVA and aVE (parasympa­thetic) fibers.

c. The lingual nerve (a branch ofCN V.3)d. TIle central gustatory pathway (sec Figure 13-3). T."lSte fibers from CN VII.

eN IX. and eN X project through rhe solimry tmet to the solit:lry nucleus.TIle solitary nucleus projCCts through the cenrraltegmental traci 10 Ihe ven­tml posteromedial nucleus (VPM) of thc thalamus. TIle VPM projects 10 thegllsralOry cortex of (he parierallobc (paricral operculum).

5. TI,e eVE component is a parasympatheric companelll that innervalcs the

Cranial Nerves 71.

lacrimal. submandibular. and sublingual glands. It contains pre~pnglionicparasym·pmhetic neurons that are located in the superior sali\'alol)' nuclell5 of Ihe caudalpons.a. Lacrimal pathway (see Figure 1)-]). The superior sali"<ltory nucleus projects

through the inteffilediate and greater petros.."1l nerves to the pterygopalatine(sphenopalatine) ganglion. TIle pterygopalatine ganglion projCCts to thelacrimal gland of the orbit.

b. Submandibular pathway (see Figure 1)·3). The superior salivatory nucleusprojects through the intermediate nerve and chorda rympani to the suh·mandibular ganglion. The submandibular ganglion projecrs to and innervatesthe submandibular and sublingual glands.

6. TIle SVE component arises from the facial nucleus, loops around the abJucent nu·c1eus of the caudal pons, and exits the brain stem in the cercbelloponrinc angle. Itenters the internal auditory meatus, tra\'erses the facial canal. sends a branch tothe stapedius muscle of the middle car. and exits the skull through the st}·lomas.toid foramen. It innervares the muscles of facial expression. the stylohyoid muscle.the posterior belly of the digastric muscle, and rhe stapedius muscle.

B. Clinical correlation. Lesions (see Figure 14·2) cause the following conditions:

1. Aaccid paralysis of the muscles of facial expression (upper and lower face)

2. Loss of the corneal reflex (efferent limb), which may lead to corneal ulceration

3. Loss of laste (ageusi:l = gust:ltory :lnesthesia) from the anterior two-thirds of lhetongue, which Ill"y result from damage to rhe chorda tympani

4. Hyperacusis (increased acuity to sounds) as a resull of st:lpedius pa~llysis

5. Bell's palsy (peripheral facial paralysis). which is caused by trauma or inf<.'Ctionand involves d,e upper and lo.....er face

6. Crocodile tears syndrome (Iacrimmion during caring). which is a resuh o( "ber.rant regeneration after trauma

7. Supranuclear (central) facial p."11sy, which resulrs in contralmeral we"kncss o( thelower face, with sparing of the upper ("ce (sec Figure 13·4)

8. Bilateral (acial nerve palsies, which occur in Guillain-B;lffc syndrome (sec Chap.tcr 14)

9. Mobius' syndrome, which consists o( congcnit:ll f:lci;']1 diplegia (CN VII) and con­vergem srrabislllus (CN VI)

VIII. THE VESTIBULOCOCHLEAR NERVE (CN VIII) is an SSA nerve. It h"s 111'0 (unc­tional divisions: the vestibular nervc, which maintains equilibrium and b"lance, and thecochlc"r nerve, which mediates hearing (see Chapters II and I2). II exits th.:- brain sremm the cercbellopomine angle and emers rhe imemal auditory meatus. It is confined 10 thetemporal bone.

A. Vestibular nerve (sec Figure 12-1)

1. General characteristicsa. h is associated funetion"lIy with the cerebellum (f1occulonodular lobe) anJ

ocular mOtor nuclei.b. It regulares compensawry eyc lllovemelllS.c. Its first·order sensory bipolar neurons "rc located in rhe \'estibular ganglion in

the (undus o( the internal auditory meatus.

72 Chapter 13

d. It projectS its peripheral processes to the hair cells of the cristae of the semi­circular ducts and [he hair cells of the utricle ami saccule.

e. It projects irs central processes to til(' four \'cslibul:u nuclei of Ihe brain stemand the Ilocculonodular lobe of the cerebellum.

f. It conducls eff('rem fibers to dk' hair cells from the brain stem.

2. Clinical correlation. Lesions result in disequilibrium, vertigo, anJ ny.stagmus,

B. Cochlcarncr\'C{S(~eFigureII-I)

1. General characteristicsa. Its first-order sensory hipolar neuron~ :Irc lucateJ in the spiral (nx:hlear) gan­

glion of thl." modiolus of [he cochlea, within ,11(' temporal bone.b. It projCCtS its peripheral rnJce~--s 10 the hair cells of til(" Ofl,.",n of Coni.C. It projccts irs central proce:;scs to thc JorsoiIl anJ velUml cochlear nuclei of [he

brain stem.d. It conducts efferent fibers to the hair cells from ,he brain stem.

2. Clinical correlation. o...--structi\"(.' lesions cause hearing loss (sensorineural deaf­ness). Irri"'th'e lesions can calise tinnitus (ear ringing). An acoustic neuroma(schw:mnoma) is a Schwann ccllrumor of rhe cochlear nef\'e lhar causes Jeafness{sec Chapter 14}.

IX. THE GLOSSOPHARYNGEAL NERVE (eN IX) ;,,, GSA, GVA, SVA, SVE, ,,00eVE nCf\'c (Figure U-S).

A. General char.lcteristics. The glossopharynb'Cal nerve is primatily a sensory nef\·('.Along with C X, CN XI, and CN XII, it mediates t,lste, salivation. and swallowing.It mediates input from the carotid sinus, which cunwins harorecepwrs th:1( monitorarterial bloo.:l prCSSllfl'. It al50 mediates input from the carotid body. which conwinschemorecerwrs lhal m(mitor the COl and O! concentr:uion of the blood.

1. Anatomy_ CN IX is the nerve of ph:H)'nge:l1 (branchial) arch J. It exits the br:linstem (medulla) from the postolivary sulcus with eN Xand CN XI. It exits the skullthrough the jugular foramen with eN X and CN Xl.

2. The GSA component innervates part of the externall'ar and the eXlernal ;Iudi­tot)' meatuS through the auricular branch of the \'agus nerve. It has celt bodies inthe supNior ganglion. It pmjens its central pr,x;es.ses tl) the spillal ttigeminal tractnnd nucleus.

3. The eVA component innervates structures thaI arc deriveJ frolll rhe endoderm(e.g., pharynx). It innerv:ltes the mucous memlmUles of the posrcrillr one-thirdof the tongue. tonsil. upper pharynx. tympanic cnvity, and ilu,liwry tube. It also in­nerv:IlCS the carotid sinus (bnroreccprors) ilnd carotid body (chemoreceptor,,)through the sinus nerve. It has cell hodies in the inferior (l'cITosal) ganglion. It isthe "ffcrent limb of the b"'g reflex and the carotid simlS rellex.

4. The SVA component innerv:ltes the taste huds of thc posterior one-third of thetongue. It has cell bodies in the inferior (petro:;al) ganglion. It projecls its centralprocesses to the solitary tract and nucleus (for a Jiscussion of the central pathway.see VII A 4 J).

5. The SVE component innerva'cs only the styl<lph:lf)'ngcus muscle. It arises fromthe nuclcus ambiguus of the Iateml medulla.

6. TIl(' eVE component is a parasympathetic component that innerv:ltl.'S lhe jXlrotidglanJ. Preg:lIlglionic pamsymparhctic ncurons arc located in the inferior s:.llivatol'ynucleus of the medulla. They project lhrough the tympanic and h,'sset peITos:11

Motor cortex k,.\---T.-UMN

<\;:>--+- Corticobubar tract

Decussation

Cranial Nerves 73

,--UMN

Medial lemniscus

Pyramid

A

~"uC~f:j.~NUCIeUS amiguus

eN x (vagal nerve)

LMN

Levator veli palatiniand palatal arches

UMN lesion

P---+-LMN

B

Figure 13·5. Inncrvation of the palmal \lrches :md uvula. Sensory inncrvmion is 1l1L"ilimcd by thc glO$<sopharyn~:eal ncrvc [cranial nervc (eN) IXI. Motor inncrvation of the palatal arches and u\'ula IS mcdiarcd hyIhe VlIl.'lIS nerve (CN X). (A) A normal JXI!:nc and uvu1:l 1n:1 person who is sa)'ing MAh.~ (B) A JXllielll wilh:mupper momr ncuron (UMN) lesion (leM :md a lowcr mowr neuron (L\iN) lesion (righl). When !Ius p:llieOl sa)'SM Ah,~ Ihe palatal arches sag. The uvula deVlalCS 101l.~lrd lhc intacl (Iefl) side.

nerves 10 lhe olic ganglion. Poslganglionic fibers from {he mic ganglion projecl to

the pnrotid gland through the auriculolemponll nerve (eN V-3).

B. Clinical correlation. Lesions calise the follow;r,g condirions:

1. Loss of the gag (pharyngeal) reflex (intemlprion of the afferenl limb)

2. Hypersensitive carotid sinus reflex (syncope)

3. Loss of general sensation in [he pharynx. tonsils, fauces. and back of [he tongue

74 Chapter 13

4. Loss of tllsle from Ihe posterior one-thinl of Ihe tongue

5. Glossopharyngeal neuralgia. which is char.lCteri:ed by sc\"cre stabbing pain in therout of the wng\IC

X. THE VAGAL NERVE (eN X) is a GSA. GVA. SVA, SVE. and GVE ner\"e (,)\."'C fig­ure 13-5).

A. General characteristics. The \'aboal nerve mediates phonation, swallowing (wilh CNIX. eN XI. and C XII). c1e\';ltion of Ihe pabte, taste, and cUlancous scns.-"i...lO fromthe ear. II inner\'ates the \'iscera of th<.' neck, thorax, and abdomen.

1. Anatomy, Th..· vagal nen'e is Ihe n('rv(' of pharyngeal (bmchial) arches 4 and 6,Pharyng<.'nl nrch 5 is cilher absent or nk.limentary. It exits Ihe brain slem (medulla)from the !XlSI,.,lh·fll)· sulcus. It exits the skull dlfough the jugular foralllen with CNIX ~m.J eN Xl.

2. The GSA component innervates the infr;atclllorial dum, external car. ext('rnal au­diTOry lIle;l!US, :lnd tymp:mic membrane, J t has cclllxx1ies in till' superior (jugular)ganglion. and it projects its ccntml processes to the spinal trigeminal tmcl ~md nu­cleus.

3. Th~· eVA component innen'aH's thl' mucous membmnes of Ihe phnrynx. larynx.l'sophagus. tmche:l. anJ thomcic and abJominal \'iscem «(0 the left colic flexure).It has ccll bo.xlies in Ihe inferior (mxlosc) ganglion, II projects its celllr.ll processesto th..· sOlitaf)' trOlo.;t :lnd nucleus.

4. The SVA component innervates the (aSle buds in the epiglottic region. It has cellbuJil'~ in til\.' inft'rior (noJosc) ganglion. It projects its ccnlmll'roc..·SSC's ro til\' s<11i­fal)' 1r,ICf and nudeus. For a discussion of the ccntml pathway. S("C VII A 4 J.

5. TIn' SVE component inner\'ates rhe phaf)'ngcal (brachial) arch tnllsck-softhe lar­ynx anJ phal)'nx, [he stri:ucJ lllll:>cle of the upper esophab'US. the muscle of theU\'ula, anJ Ih" It.'vawr \'eli palmini anJ palatoglossus muscles. It f<."'Cci\"es SVE in­put from rhe cmnia! di\'ision oflhe spinal acccssof)' ner....e (CN XI).lt arises fmmIhe nuclt'us amhib'\llIS in rhe Iateml medulla. TIle SVE component provides the ef­ferent limh of the gag renex.

6. TIll' eVE componcnl inncn'mes the viscer:l of the neck and the thomcic (heart):IllJ ahJuminal cadties;ls f:lr as lhe lef, colic flexure. Preg~mg1ionic pamS)'lllpa­fhetic neurons Ihal :Ire located in the dorsal1l10IQr nucleus of the medulla projectto 111<: rennin:ll (inrr.lIlurml) ganglia of the \<isc('ral organs (sec Figult' 18-2 andT:rble 18-1).

B. Clinic:11 correlation. Lesions and reflexes C(lllse the following conditions:

1. Ipsilatcral pimllysis of the soft palnte, phnrynx, anJ laf)·nx dmr leaJs to dyspho­nia (hU:lrscness). dyspnea. dysarthria. and dysphagi:l

2. Loss of the g:lg (p.1latal) reflex (efferent limb)

3. Anesllu'sia of Ihe pharynx and larynx that leads to unilateml loss of the coughrdlex

4. Aortic aneurysms and tumors of the neck and thomx Ihat frequentl)' compressthe \"agal ner...e

5. Completc laryngt.":I1 paralysis. which can be mpidly fatal if it is bilateml (asphyxia)

6. Parasymp.1thctic (wgelati\,e) disluroonces, including bradycanlia (irrirmin' le­sion). rachycanlia (destructi\'e lesion). and dilation of the stomach

Cranial NeNes 75

7. The oculocardiac reflex, in which pressure on the eye slows the heart rare (affer­ent limb of CN V·I and efferent limb ofCN X)

8. The carotid sinus reflex, in which pressure on the carotid sinus slows the heartrmc (bradycardia) lefferent limb ofCN XI

XI. THE ACCESSORY NERVE (CN XI), or spinal accessory nerve, is an SVE nerve (Fig­urc 13-6).

A. General characteristics. The accessory nen'e mediates head and shoulder movementand innervates the laryngeal muscles. It has the following divisions:

1. The cranial division (accessory portion), which arises from the nucleus ambiguusof the medulla. It exits the medulla from the posrolivary sulcus and joins the va­gal nerve (CN X). It exits the skull through rhe jugular foramen wirh CN IX andCN X. It innervates the intrinsic muscles of the larynx through the inferior (re­current) laryngeal nerve, with the exception of the cricothyroid muscle.

2. The spinal division (spinal portion), which arises from the ventral hom of cervi­cal segmenrs Cl through C6. The spinal roots exit the spinal cord laterally be­tween r1w vemml and dorsal spinal rOO[5, ascend rhrough the foramen magnum,and exit thc skull through the jugul::l.r foramen. It innervates the stemocleid~

mastoid muscle with the cervical plexus (C-2) and the trapezius muscle with rhecervical plexus (Co3 and C-4).

B. Clinical correlation. Lesions cause the following conditions:

• }-------!f-- Facial nucleus WI pons

CN Ix----,/~il

Ambiguus nucleusin medulla ---++1

Jugular foramen

CNIX--¢

CNX--t--O

II ep-CNXI

t--t---Accessory nucleusin spinal cord (C1-C5)

Figure 1J..6. The crnnial and spinal di"isioru; of~ acces:sory nerve (cranial nerve (eN) lX). The cranialdi\'ision hitchhikes a ride wim the accessory nerve. men joins the vagal nerve to become me weriDt (recurrent)hlf)'I\l,.>C;11 ner....e. The recurrem laf)'fll,.ocal nef"e innef''ates the intrinsic muscles of me larynx, except for thecricothyroid muscle. The spin:11 dh'ision innef''ates the trapezoid and stemocleidomasroid muscles. Three nervespltSS through the jugular foramen (glomus jugularc tumor).

76 Chapter 13

1. Paralysis of the sternocleidomastoid muscle that results in difficulty in turningthe head ro the contralateral side

2. Par.llysis of the trapezius muscle that results in shoulder droop and inability roshrug the shoulder

3. Paralysis of the larynx if the cranial root is invoked

-'--UMNo ' o --UMN

Corticobulbar tract --cbct>-- Corticobular tract

Decussation

\/\

LMN

LMN lesion(flaccid paralysis)

UMN lesion(spastic paralysis)

Decussation --",

LMN

Hypoglossal nerve

co

Pyramid

Medial lemniscus

A B

Figure 13-7. Mowr inner,,;uion of Ihe 101lj,'lIC. Conicobulhar lil>cn; proje<1 preJorn;n:mtly 10 the comr;:lbl­er.,1 hYJXll;lossal nudcu.~. An upper lllotor neuron (U/I.·IN) lesion causes JC\'iat;on 0( the pr(l(nxkoJ 10nl,'UC to Ihewe;'1,; (comrahlternl) Side. A lower motor neuron (L\1N) lesion c:m>C5 deviation of tile 1'r(l(n1dcd 101'b'Ue 10 IhelI'e;,1,; (IJblhueflll) side. (A) Nomlal tOIlI.'lIC. (B) TOIll,'UC wilh UMN and LMN lesions.

Cranial Nerves 77

XII. THE HYPOGLOSSAL NERVE (eN XII) is a GSE nerve (Figure 13-7).

A. General characteristics. The hypoglossal nen'(' mediates tongue movement. It arisesfrom the hypoglossal nucleus of rhe medulla and ex irs the medulla in the preoli\'arysulcus, It exirs du," skull through rhe hypoglossal canal, and it innervates the intrinsicand extrinsic muscles of the tongue. Extrinsic muscles arc the genioglossus. str­loglossus, and hroglossus.

B. Clinical correlation

1. Transection resuhs in hemiparal)'sis of the tongue.

2. Prorrusion causes the lOngue to point 1O\I:aru the weak side bc<:ausc of the unop­posed acrion of the opposite genioglossus muscle.

1.4Lesions of the Brain Stem

I. LESIONS OF THE MEDULLA (Fil.~re 14-1)

A. Medial medullary syndrome (anterior spinal artery syndrome). Affected structuresand rcsulmm dellciLS include:

1. The corticospinal tract (medullary pyramid). Lesions result in commbtcral spas­tic hemiJXlresis.

2. The medial lemniscus. Lesions rcsuh in contralatcmlloss of wetile and vibrationscnso1tion from the trunk and extremities.

3. The hypoglossal nucleus or intraaxial rOOI fibers rcr.mial nerve (eN) XII]. Le­sions h.-sult in ipsiialCrnl flaccid hcmiparalysis of the longue. When promlded. thelongue points £0 the sid£' of the k'Sion (i.e., the weak side). Sec Figure IJ. 7.

Vestibular nuclei

Homer's lrad

Inferior cerebellar peduncle

Spinal lrigemlnal Iract and nUcleus-+~t:'J:\

CNX~~'(

Nucleus ambiguus

Lateral spinothalamic tract

CNXII

Pyramid

Medial lemniscus

NudeIJS of solitary tract

Dorsal molor nucletJs 01 eN x

Hypoglossal nucleus

•

A

Figure 14-1. Vasculllr lesions of the cauu.11 pons at the level of the hyJlOt:los.s...1nuclcus ofcranial nerve (CN)XII :IIlU ,hc dorsallJ'lO(of nucleus of CN X. (A) McJi:11 m...-Jullliry ~Yllull)mc (arlcrial spmal :uu::ry). (8) L'ucrallllC\lulbry lrosu:rior inferior cerehcllar ;Inel)' (PICA)I syndrome.

78

lesions of the Brain Stem 79

B. Lateral medullary syndrome Lposterior inferior cerebellar artery (PICA) syndrome]is characterized by dissociated scn;;ory loss (see I B 6---7). Affe<:too stnlClll!\.'S anJ re·sultant deficiu include:

1. The vestibular nuclei. Lesions rcsuh in nY~lagmus. nausea. vomiting. and \'enib'O'

2. TIle inferior cerebellar peduncle. Lesions result in ip$ilatcral cerehcllar signs le.g..dys(~xi:J, dysmcnia (pas( poiming), drsdi3dochokincsb].

3. TIle nucleus ambiguus of CN IX, eN X, and eN XI. Lesions result in ipsil:nemllaryngeal. pharyngeal, and palatal hemipamlysis li.e.. loss of the l;:ag reflex (effer­ent limb). dys.'mluia. dysphagia. and dysphonia (ho.:u~eness)J.

4. The glossopharyngeal nerve roots. Lesions result in loss of the b':lg reflex (,Ifferellllimb),

5. The vagal nerve roots. Lesions result in the sallie deficit.s as seen in lesions in­volving the nucleus ambigllus (sec I B).

6. The spinothalamic tracts (spinal lemniscus). Lesions result in conrralarcralloS$of pain and tcmpenll'ure sensation frOllllhe trunk and exrremities.

7. The spin'll trigeminill nucleus and tract. Lesions result in ipsilateral loss of r:linand temperalllrc sensation from the face (faci:ll hemianesthesia).

8. TIle descending sympathetic trdCI. Lesions result in ipsibter:ll Horner's syndroml'(i.e.. ptosis. miosis. hem ianhidrosis. and apparelll enophthalmos),

II. LESIONS OF THE PONS (Figure 14-1A)

A. Medial inferior pontine syndrome results from occlusion of the paramedian branchesof the basilar artery. Affe<:ted structures and resultant deficits include:

1. The corticospinal tract. Lesions result in comrnlateral $p<,stic hemiJY.lresis.

2. The medial lemniscus. Lesions result in contrnlaternllossof tactile sensation fromthe trunk and cxtrcmitit.'S.

•

Medial lemniscus

Corticospinal traCl

Vestibolar (MJClei

Abducent nucleus

Lateral sPinothalamiC traCl

CN VIII (vestibular nerve)

CN VII

Nucleus CN VII

Spinal trigeminal nucleus and tract ----'l-~=I__t_.JA~~

Agure 14--2. Vascular lesions 'If the cltl"bl pon":11 the level of the abducent nucieUli of cmnlal ncr\"C (CN)VI lInJ the facial nucleUli of CN VII. (Al ~'kdial mfcrior ponllne SynJrOfnC. (8) L'ller,ll inferior pontine syn­drome 1:IIlICrior inferior cerebellar :lrlCI)' (AlCA) synJromel. (C) Mcdiallongitudmal fa:.ciculw. (MLF) ~)'ll'

dn:lInc.

80 Chapter 14

3. The abducent nerve roors. lesioll5 resuh in ipsilmerallareral reclUs paral}'sis.

B. Lateral inferior pontine syndrome lamerior inferior cerebellar artery (AICA) syn­drome) (Fi~..ure 14-28). Affccled ,.tNc!Ures and resultant deficits include:

1. The facial nucleus and intraaxial ncr\'{' fibers. lesiuns resulr in:a. Ipsibrernl filcial nervc p:unlrsisb. Ipsibtemlloss of mste from the illllcrior lwo-lhirds of rhe TOnguec. Ipsibtemlloss of Iflctil1l:tt iOll lind reduced salivlll iond. Lo~~ nf cornc;ll ;lnJ stapedial reflexes (efferent limbs)

2. TIle cochlear nuclei and intraaxial nerve fibers. le~ions result in unilaternl cen­nal Jcafnl'ss,

3. TIl{' veslibular nuclei and intraaxial nerve fibers. lesions result in nySlagmus.nausea. vomiting. and \,('(tigo.

4. The spinal trigeminal nucleus and tract. lesions result in ipsila(erall~ of rainand tempcrarurc S('ns.'lrion from Ihe face (facial hemianesthesia).

5. The middle and inferior cerebellar peduncles. lesions result in ipsilatemllimband gait dysraxia,

6. The spinothalamic tracts (spinal lemniscus). lesions rcsuh in conrmlrHemllossof pain and temperarure semalion from Ihe Trunk and extremilies.

7. The descending sympathetic trl.lct. lesions result in ipsilareml Horner's syndrome.

C. Medial longitudinal fasciculus (MLF) syndrome (internuclear ophlhalmoplegia)[sec Figure 14-2CI interrupts fibers from rhe conrr.lbtcral abducent nucleus Ihal pro­jecl, lhrough rhe MLF. to rhe ipsilareral medi:ll rectus subnucleus ofCN Ill. It causesmedial rectus pals}' on aucmproo lateral conjugate ga:e and nystagmus in the ab­ducring c)'e. Convergence remains inmcr. This syndromC' is ofren seen in pmicms wilhmultiple sclerosis.

O. Facial colliculus syndrome usually resulrs from a pontine ~Iioma or a \'ascular acci­denr. The internal g.:-nu ofC VII and the nucleus ofCN VI underlie the facial col­liculus.

1. Lesions of the internal genu of the facial nerve cause:a. Ipsilateml f.Jcial paralysisb. Ipsilaremlloss of the corneal reflex

2. Lesions of the abducent nucleus cause:a. Lateral rcctus paralysisb. Medial (wnvergent) strabiSlllusc. Hori:ontal diplopia

III. LESIONS OF THE MIDBRAIN (F;g"" 14·3)

A. Dorsal midbrain (Parinaud's) syndrome (Sl.'C Fi~"llre 14·jA) is often lhe r('Suh of:1pinealoma or germinoma of rhe pineal region. AffL'CtN structures and resulmntJeficils include:

1. The superior colliculus and prelt.'Ctal area. Lesions cause paralysis of upwarJ anJdownward ga:e. pupillary disturbances, and absence ofcom'ergence,

2. TIle cerebral aqueduct. Compression causes noncommunicating hydrocephalus.

B. Paramedian midbrain (Benedikt> s}'ndrome (sec Figure 14·313). Affecred strucltlresnnd resultant deficirs include:

Lesions of Ihe Brain Stem 81

Red nucleus

c

:x~(' -Z:?~t-- Medial lemniscus

IY:rt--+- Dentatothalamictract

APosterior commissure and center lor verticaJ conjugate gaze

St4lerior colliaJlus

Nucleus of CN III

t;"''i'7~r:::~~~,,", Spinothalamic tract

•

Corticobulbar tract

Substantia nigra -1--+

Conicospinallract ~"'--

Medial geniC1Jlate body

CN III

Figure 14-3. Lesions of the rostral midbrain at the level of the superior collieulus and oculomotO£ nucleusofemnial ne....·c (CN) Ill. (A) Dorsal midbmin (Parinaud's) syndromc. (B) rammedian midbrain (Benedikt) syn­drome. (C) Mcdial midbrain (Weber) syndrome.

1. The oculomotor nerve roots (intraaxial fibers). Lesions cause complete ipsilateraloculomotor pflrfllysis. Eye abduction and depression is caused by the intact lateralrectus (eN VI) and superior oblique (eN IV) muscles. Ptosis (paralysis of the le­vator palpebra muscle) and fixation and dilation of the ipsilateral pupil (completeinternal ophthalmoplegia) also occur.

2. The dentatothalamie fibers. Lesions cause contralateral cerebellar dystaxia withintenrion nemor.

3. The medial lemniscus. Lesions result in contralateral loss of tactile sensation fromthe trunk and extremities.

C. Medial midbrain (Weber) syndrome (see Figure 14-3C). Affected structures and re­sultant deficits include:

1. The oculomotor nerve roots (intraaxial fibers). Lesions cause complete ipsilateraloculomotor paralysis. Eye alxluction and depression is caused by intact lateral rec­tus (CN VI) and supetior oblique (CN IV) muscles. Ptosis and fixation and dila­tion of the ipsilateral pupil also occur.

2. The corticospinal tracts. Lesions result in contralateral spastic hemiparesis.

3. The eorticobulbar fibers. Lesions cause contralateral weakness of the lower face(eN VII), tongue (CN XII), and palate (CN X). The upper face division of thefacial nucleus receives bilateral conicobulbar input. The uvula and pharyngealwall are pulled toward the normal side (CN X), and the protruded tongue pointsto the weak side..

IV. ACOUSTIC NEUROMA (SCHWANNOMA) [Figure 14-4J is a benign rumor ofSchwann cells that affects the vestibulocochlear nerve (CN VlIl). It accounts for 8% ofall intracranial tumors. It is a posterior fossa tumor of rhe internal auditory meatus andcerebellopontine angle. The neuroma often compresses the facial nerve (CN VII), whichaccompanies eN VIII in the cerebellopontine angle and internal auditory meatus. It mayimpinge on the pons and affect the spinal trigeminal tract (CN V). Schwannomas occurtwice as often in fcmalcs as in males. Affccted structures and resultant deficits include:

82 Chapter 14

Figure 14-4. Ma~neric rC>.Oll:mce image of an acousrlc neuroma. This cororml ~Iion "hows dilalion of lhe\·cnmck.". The "c"lIhulocochll:;lr ncr\'(' is "biblc in the Icft imemHl audlf{)('}' lI\('atus. Thc Ilunor indent:> Ihc hlr·o:rall"'lh. Cmnl,,1 ner\'e (CN) Imbics induJe CN V, VII. anJ VIII. Syml'lOllb includ... ullilmer..11 ,Ie"focss. f,I(I,,1,me:.lhe:.I.1 ,Illd "·...,llme.». and an ;lhscnt coronal rcllcx. Tllb is ,I Tl-weighrcd llll.l/:e.

A. The cochlear nerve of CN VIII. Damag... resulrs in tinnitus and unilal'cral ncrvcdeaf­ness.

B. The vcstibuhlr nerve of CN VIII. Damage rl'sults in "crt igo. nystagmus, nausea, ,'om­iting, and unsteadiness of gait.

C. The facial ncrvc (eN VII). Dmn<lge resulrs in f<lcialweakness <lntl loss ofthecorne:llreflex (efferent limb).

D. The spinal Iril;cminal tract (CN V). Da1ll<lge results in p:lresthesin. <lnest hesia of theipsilateral face. and loss of the corneal reflex (afferent limb).

E. Neurofihromatosis type 2 often occurs with bibleral acousric neurumas.

V. JUGULAR FORAMEN SYNDROME usu<ll1y results frum a posterior fossa tumor (e.g.,l:lomus jUl:ul:lrc Itlmor, rhe most common inner e;lT tumor) thm compresses eN IX. X,;mtl Xl. Affecled snucturcs and resultant deficits include:

A. The glossopharyngeal nerve (eN IX). D;l111age results in:

1. lpsilarernlloss of rhe gag reflex

2. lpsilaternlloss of pain, tempcrnture. and taste in the tonl,'Ue

B. The ,ragal nenrc (eN X). Damage results in:

1. Irsilmeml pamlysis of the soh pnbt~ and larynx

2. lpsil:ucmlloss of the l,':Ig reflex

Lesions of the Brain Stem 83

C. TIl(' accessor)' nerve (eN XI). Damage result's in:

1. Paralysis of the sternocleidomastoid muscle. which results in rhe inabiliry ro rumthe head (0 the opposite side

2. Paralysis of the tr.lpc:ius muscle. which cauS(.'S shoulder droop and inability toshrug the shoulder

VI. "LOCKED-IN" SYNDROME is a lesion of the base of [he pons as [he result of infarc·[ion, trauma. tulllor. or demyelination. TIle corticospinal and conicobuloor tracts arc af·

Leh SCLA

II'~CThrombosjs

VA

ASA

BCT

CCA~Leh SCLA

VA

BCT

~ ACA~UL '"

~~MeA MCA ACOM

ICA PCA~ e-SCA

AICAJ,EA

ECA PICAjof ECA

IASA

Aorta Aorta

A II B II

Figure 14-5. An,uomy of the suhcf:I\'ian sl'-~ll s\'nJrome. Thrumbosis of Ihe proxill'l.'ll pan o( the subcb\'ian,mery (kfl) rcsulrs in retrograde hlooJ no\\' dnough d'lC ipsi!mcml \'enebr.11 artery and imo the Ic(t M1hcb\'ian,mery. Blood can be shumoo (rom Ihe righl vertebral anery ,md down the left \'enebral 'lrll:ry (A), Blood m,ly..Iso reach the le(t \'cnehr.11 anery through thc cafO(id circuhnion (8). ACA = ,u\lcriorccrebell.. r anc!)'; ACOM= alllcrtor communic,lling ,InC!)'; AICA =anterior infcrior cerebellar .me!)'; ASA = amcrior spinal :Inc!)'; BA.,. basi1;1r ,InC!)'; BCT = br.loChioc:cphalic lrunk: CCA = comlllon c.lfO(iJ anery; ECA = CXlen'l.,1 cafO(id ancry;ICA = imemal carOlid :mcry; MCA "" middle cercbr.11 :mcl)'; PeA ,.. JlOSlcrior cerebral tlnc!)'; PCOM = porIcrior communic:uing ancry; PICA = po:.terior infcriorccrchclhlr :U1cry; SCA = superior communicating :mc!)';SCtA = subchwi:m anery; VA = vcn('br.ll artcry,

84 Chapter 1.4

feered bilaterally. The oculomotor and trochlear nerves are not injured. Patients arc con­scious and may communicate through vertical eye movements.

VII. CENTRAL PONTINE MYELINOLYSIS is a lesion of Ihe base of the pons that affccls Ihecorticospinal and corticobulbar tracts. More than 75% ofcases are associated with alcoholismOf rapid cOlTCCtion of hnXlfIatremia. Symptoms include spastic Quadriparcsis, pseudobulbarpalsy, and mental changes. This condition may become the locked. in syndrome.

VIII. "TOP OF THE BASILAR" SYNDROME results from embolic occlusion of the rostralbasilar artery. Neurologic signs include optic ataxia and psychic paralysis of fixation ofgaze(Balint's syndrome), ectopic pupils, somnolence, and conical blindness, with or withoutvisual anosognosia (Anton's syndrome).

IX. SUBCLAVIAN STEAL SYNDROME (Figure 14-5) results from thrombosis of the leftsubclavian artery proximal to the vertebral artery. Blood is shunted rerrograde duwn (heleft vertebral nrrery :md into the left subclavian artery. Clinical signs include transientwenkncss nnc! claudication of the left arm on exercise and verrcbrobnsilar insufficiency(i.e., verrigo, dizziness).

X. THE CEREBELLOPONTINE ANGLE is rhe junction of the medulla, pons, and cere­bellum. eN VII and Vll1 arc found there. Five brain tumors, including a cyst, are often lo­Cated in thecerebcllopontine angle cistern. Remember the acronym SAME: schw:mnoma(75%), arachnoid cySt (I %), meningioma (10%), ependymoma (I %), and epidermoid(5%). TIle percentages refer to cerebcllopomine angle tumors.

1.5Cerebellum

I. FUNCTION. The cerebellum has three primary functions:

A. Maintenance of posture and balance

B. Mainlcnancc of muscle tone

C. Coordination of voluntary mOlor acth'ity

II. ANATOMY

A. Cerebellar peduncles

1. TIle superior cerebellar peduncle contains the major output (rom the cerebellum,rhe dentatotha1:unic mer. 111is rrae! !Cnninnles in the \'cntmll:ucml nucleus ofthe thalamus. It has one major affeTenr pat hway, the ventral spinocerebellar tmcr.

2. 111e middle cerebellar peduncle receives pontocerebellar fibers. which project to

the neocerebellum (ponroccrcbcllum).

3. The inferior cerebellar peduncle has three major afferent tracts: the dorsal spi­nocerebellar tract, the cuneocerebellar tract, and fhe olivoccrcbcllar [mCl (rom theconrrabrcml inferior olivary nucleus.

B. Cerebellar cortex, neurons, and fibers

1. The cerebellar cortex has three layers.a. The molecular layer is the outer layer underlying the pia. It contains stellate

cells, basket cells, and the dendritic arbor of the Purkinje cells.b. The Purkinje cell layer lies between the molecular nnd rhe gramlle ccillayers.c. The granule layer is rhe inner layer overlying the whire maner. It contains

granule cells, Golgi cells, and cercbell:1r glomeruli. A cerebeiLu glomerulusconsists of a mossy fiber rosette, granule cell dendrites, and n Goigi cell axon.

2. Neurons and fibers of the cerebelluma. Purkinje cells convey the only output from the cerebellar cortex. They pro­

jeer inhibitory output [Le., "Y-mllinoblltyric acid (GABA)] to the cerebellarand vestibu1:~r nuclei. These cells arc exciTed by parallel and climbing fibersand inhibited by GABA-ergic basket and stellate cells.

b. Granule cells excite (by way of gluramatc) Purkinje, basket, stellare. andGolgi cells through pMallel fibers. They ;Ire inhibited by Golgi cells and ex­cited by mossy fibers.

c. Par-illel fibers are the axons of granule cells. These fibers extend into the mo­lecular layer.

d. Mossy fibers are the afferent excitatory fibers of the spinocerebellar, pontO-

85

86 Chapter 15

cerebellar, and wSlibuloccrcbellar tracu. They Icrminale as moss)' flberroscues on granule cell dendrites, The)' excilc granule cells to dischargeIhrough their parallel flbers.

e. Climbing fibers are Ihe afferent excirawT)' (b)' \\'3)' of aspartalc) fibers of Iheoli\'ocerebellar trael. These fibers arise from the contralateral inferior olh":ltynucleus. They terminate on neurons of the cerebellar nuclei and dendrites ofPurkinje cells.

III. THE MAJOR CEREBELLAR PATHWAY (Figure 15-1) consisls of Ihe followingstructures.

A. The Purkinje cells of the cerebellar cortex projeci to the cerebellar nuclei (e,g., den­nne, cmooliform, globose, and fasligial nuclei),

B, The dentate nucleus is the major eff('clOr nucleus of the cerebellum. It gi\"Cs rise t(1the dentalOl halamic traCI, which projects I hrough the superior cerebellar peduncle to

the conlrnlnleral venl'rall:n\'rnl nucleus of the rhalamus. The decussation of the su­perior cerebellar peduncle is in the cnudal midbrnin tCgllll'ntUIll.

COfIicopontine neuron

Corticospinal neuroo ~--,~;!:~

Ventral lateralnucleus 01 thalamus

Internal capsule(posterior limb)

Lentiform

""""'"~VI/' ,.,..!>"""r- Red nucleus

Emboliform nUCleus~~~~:~,~~~:~f::;~~;~::-_ Superior cerebellarpeduncle

Dentate nucleus -f7''''-..",''

Pyramidal decussatioo

Middle cereoenar peduncle

Rubrospinal tract

Corticospinal tract

Agure 15-1, The priocip.... l ccrchdbr conne<:tions. l1lc major c((crcm palh\\'a~' is Ihe OCIU:lI01h:,brllO(:or·r1CallT:lCI. TI1C ccrehcllunl rl"Cl."i\'('! inpul (rom Ihe ccrl."bml COrlCX Ihrough the COrlicopomocl."rcbclbr ImCI.

Cerebellum 87

C. The ventral lateral nucleus of the thalamus receives the dentalOthalamic tract. Itprojects to the primary mOlOr cortex of the precentral gyrus (Brodmann's area 4).

D. The motor cortex (motor strip, or Brodmann's area 4) receives input from the ven·trallareral nucleus of the thalamus. It projects as the corticopontine nac[ to the pon·tine nuclei.

E. The pontine nuclei receive input from the motor cortex. Axons project as the ponto­cerebellar rmcr [0 the contralateral cerebellar cortex, where they terminate as mossyfibel1i, thus completing the circuit.

IV. CEREBELLAR DYSFUNCTION includes the following triad:

A. Hypotonia is loss of the resistance normally offered by muscles to palpation or passivemanipul:niol\. It results in a floppy, loose-jointed, rag-doll appearance with pendularreflexes. The patient appears inebriated.

B. Dysequilibrium is loss of balance characterized by gait and trunk dystaxia.

C. Dyssynergia is loss of coordinated muscle activity. It includes dysmetria, intentiontremor, failure 10 check movements, nystagmus, dysdiadochokinesia, and dys­rhythmokinesia. Cerebellar nystagmus is coarse. It is more pronounced when thepatient looks toward the side of the lesion.

V. CEREBELLAR SYNDRDMES AND TUMDRS

A. Anterior vermis syndrome involves the leg region of the anterior lobe. It results fromatrophy of the rostral vermis, mOSt commonly c:lused. by :llcohol :loose. It causes gait,trunk, and leg dystaxia.

B. Posterior vermis syndrome involves the flocculonodular lobe. It is usually the resultof brain tumors in children and is most commonly caused by medulloblastomas Ot

ependymomas. It causes truncal dystaxia.

C. Hemispheric syndrome usually involves one cerebellar hemisphere. It is often the re­sult of a brain tumor (astrocytoma) or an abscess (secondary to otitis media Ot mas­toiditis). It causes arm, leg, and gait dystaxia and ipsilateral cerebellat signs.

D. Cerebellar tumors. In children, 70% of brain tumors are found in the posterior fossa.In adults, 70% of brain tumors are found in the supratentorial compartment.

1. Astrocytom<ls constitute 30% ofall brain tumors in children. They are most oftenfound in the cerebellar hemisphere. After surgical removal, it is common for thechild to survive for many years.

2. Medulloblastomas are malignant and constitute 20% of all brain tumors in chil­dren. They are believed to originate from the superficial granule layer of the cere­bellar cortex. n,ey usually obstruct the passage of cerebrospinal fluid (CSF). As aresult, hydrocephalus occurs.

3. Ependymomas constitute 15% of all brain tumors in children. They occur mostfrequently in the fourth ventricle. They usually obstruct the passage of CSF andcause h)·drocephalus.

..

1.6Thalamus

I. INTRODUCTION. The thalamus is the largest division of Ihe diencephalon. II plays animpon;l.m role in the integration of the .sensory and mawr systelllS.

II. MAJOR THALAMIC NUCLEI AND THEIR CONNECTIONS (Figu", 16.1)

A. The anterior nudcus rccein's hypothalamic input from the ,"amillary nucleusrhrough rhe mamillothalamic tract. It projectS lO [h(' cingulOllc .l,,'ynls and is part of rhePape: circuit of emotion of rhe limbic system.

B. TIle mediodorsal (dorsomooial) nucleus is reciprocally connected to the prefrontalcortex. II has abumlam connections wid, inrmlaminnr nuclei. It rccci,·cs input fromthe :JmYl.tdala, .subsmntia nigra. and temporal neocortex. When it is (k'Stroyed, mem­ory loss occurs (Wcrnickc-Kors.1koffsyndrome). The mwiooors::ll nucleus plays a rolein rhe expression of affect, emotion, and beh:wior (limbic (unction).

C. The centromeclian nucleus is the largest intmkunin:u nucleus. It is redprocally con­nected to the motor cortex (Broomann's arca 4). TIle centromooian nucleus receivesinpur from the globus pallidus. It projects to the strinrum (caudate nucleus and puta­men) and projects diffusely to the emire neocortex.

D. The pulvin:lr is the largest thalamic nucleus. It has reciprocal connections with theassociation cortex o( the occipital, parietal, and JX>Stcrior tcmpor:lllobes. It receivesinput from the lateral and medial geniculate Ixxlies and the superior col1iculus. It playsa role in the integriltion of visual, auditory, i1nd somcsthctic input. Destruction ofthe domin:lnt rulvinar may result in sensory dysphasia.

E. Ventral tier nuclei

1. The ventr,ll anterior nucleus receives inpur from the globus pallidus and sub­st:mti:l nigra. It projects diffusely to the prefrontal cortex, orbital cortex, :md pre­morar cortex (Brodmann's area 6).

2. The ventrill [ateral nucleus receives input from the cerebellum (dentate nucleus),globus pallidus, and substanria nigra. It projects ro the motnr cortex (Broomann'sarm 4) and the supplementary mntor cortex (Brodmann's area 6).

3. The ventTOl1 posterior nucleus (ventrob:ls:ll complex) is the nucleus of termin:l­tion ofgeneral somatic afferent (fotlCh, pain, and temper:llure) and spedal visceralafferent (taste) fibers. It has twO subnuclei.a. The ventTOl1 posterolateral nucleus receives the spinOlhalamic tmcts and the

Hll'di:l[ lemniscus. It projecrs to the somesthctic (sensory) cortex (Brodmann'sareasJ.l,and 2).

b. The \'entral posteromedial (VPM) nucleus receives the rrigeminothalamictracts and projects to the somesrhctic (sensory) carrel( (Brodmann's are:lS J, I,and 2). TIle gustatory {tasre) pathway originates in the solitary nucleus and

Thalamus 89

•Anteriof'

nuclear group ntemal medulary lamina____.1

VPL

8

Mediodorsalnucleus

Pulvinar

lateral geniculate body:::::SZC"'""~M~edial geniculate body

Me<ial1emnisaJs }Spinothalamic tracts

(Amygdaloid """""Tempol'al neocortexSubstantia nigra

Prefrontal cortex

"--~~~~,- .. {AfeaS18and19Inferior parietal lobule

-1-:::f~~~~::~ {Inferiof ooiliculusLateral lemniscus

Areas 41 and 42Optic tract

Area 17

Cingulate gyrus

Area 4

Dentate nUCleUS)Globus paliidusSlbstantia nigra

Area 6 )DlHuse frontal cortex

•Mamitlothalarnic tract}Fornix

Globus pallldus }Substantia nigra

Areas 3, 1, 2Trigeminothalamic

tracts and Iaste palhways

Figure 16-1. M:ljOf th:lbmi( nudci :md their (Olllll..'(lions. (A) Don;ohuer.11 aspt."CI :lnd Ill"jor nuclei, (8)Major afferem and efferent (onncnions. VA = vcnlr.ll allicrior nuclcus; VL = VClllr.lll:llCr.11 nuclcus; VPL =vcntml poo;tcrior l:lIeral nuclcus; VI'M = \'cmml poslcrior meJial nucleus.

projects via the cemraltegmelllallTact to VPM, and thence to the gustatorycortex o( Ihe postcentral gyrus (Brodmann's area 3b), o( the (ramal operculullland insular cortex. The taSle pathway is ipsilateral.

F. Metathalamus

1. TIle lateral geniculate body is a visual rela)' nucleus. It receivcs retinal input throughthe optic tmcl and projccrs to the primary visual cortex (Brodmann's area 17).

2. The medial geniculate body is an auditory relay nucleus. It r«eh'cs auditory in­pur through the brachium o( the inferior colliculus and proj«ts to the primary au­ditory (Quex (Brodmann's areas 41 and 42).

G. TI,C reticular nudcus of thalamus surrounds (he (halamus as a Ihin lorer of 'Y-aminobu­lyric acid (GA BA)-ergic neurons. II li<:s betwccn the external tm..-dullary lamina and theimernal capsule. It receives cxcit<lIol)' collateral input from corricothalamic and thala­mucortical fibers. It projects inhibitory fibers to thalamic nudei fr01l1 which it n:{:eivcsinput. It is thought tn pIny ;l role in nQrmal clcctrocncephaolgrarn rendings.

90 Chapter 16

III. BLOOD SUPPLY. The thalamus is irrigmed by three arteries (see Figure J.).

A. The posterior communicating artery

B. The posterior cerebral artery

C. The anterior choroidal arter)' (Iatcral ~:cnicuklle body)

IV. THE INTERAL CAPSULE (Figure 16·l) is a layer of white matter (myclinau.-d axons) thatseparates the caudate nucleus and the thalamus medially from the lentiform nucleus klTerally.

A. The anterior limb is located between the cllud:1te nucleus :md the lentiform nucleus(globus pallidus and putamen).

B. The genu contains the corticobulbar fibers.

C. The posterior limb is located between the thalamus and the lentiform nucleus. It con·tains conicospinal (pyramid) 6bers as well as sensory (pain. temperature. and touch).visual. and auditory ooia[ions.

D. Blood supply

1. The anterior limb is irrigated by [he medial srri:ne branches of [he anterior cerebralartery and rhe lateral striate (lenticulostriate) branches of [he midJle cerebral artery.

2. The genu is perfused either by dircct branches from the internal carotid anel)' orb\' p:lllidal branches of the anterior choroidal artery.

3. TIle posterior limb is supplied by branches of the anterior choroidal anery nnJlenticulostriate branches of the middle cercbml aneries.

caudate nucleus --/-'-

Corticobul>a.r fibers --r"-14-fJ

Posterior limb --+--+t-Thalamus --1--

Sensory radiations fromVP nucleus to areas 3. 1. 2

Lateral geniculate body(vision)

/' Anterior ~mb

Globus pallidus

--<-_Putamen

~nl--+_~r-CorticosPinalfibers

I ~_ Auditory radiation to transversetempol"al gyri of Heschl(areas 41 and 42)

VISual radiation 10striate COl1ex of oocipitallobe (area 17)

Agure 16-2. l-Iori:omal.scClion o( Ihe righ, imernal capsule showing rhc m:ljor iihcr f'rojc<:tions. Cll1lical1\'important lraclS lie in the i,ocnu and IXJ<iilerior timbo Lesions o( Ihe internal capsule caus.:: COntrablleml hemi·p;lresis ;)nd cOlltml:ueral hemianopia. VI' = \"enrr.ll posterior nucleus.

1.7Visual System

I. INTRODUCTION. The visual £)'s[em is served b)' the OPlic: neryc, which is a special so­marie afferent nervc.

II. THE VISUAL PATHWAY (Figure 17-1) includes the following ~rruclurcs.

A. Ganglion cells of the rNina foml the optic nerye [cranialncrvc (eN) II). n)C~t pro­jecr from the nas;11 hcmiretina to the comralateral lateral gcniculrnc body and fromthe temporal hcmiretina to the ipsil::ncrallrltcral gcnicul:uc body.

\:~:::o'""::"'- Visual corteIC area 17

Visual radiation to lingual gyrus

Visual radiation 10 cuneus

Retina

+i-Jlf---Lateral geniculatebody

Optic tracl,

'fIJ>-Optic nerve

7

'), ,• 3

5

• '0(),()

~3ca

()·ca~5~

G'c.(){t

Agure 17-1. The visual p:nhway (rom the retina to the visu'll conc:o; showiny ViSU;11 iicld defecls. (I) lpsilm.cr.11 hllndness. (2) Hinas.'l.l hcmianopi:l. (3) Bilcmpoml hemi:mopia. (4) Higlll hcmi:ltlopia. (5) Right upper quad­r..lnt:1ll0pl:I. (6) Rightlowerquadr:lnltlnopia. (7) Right hemianopia wIth 111.1Cularsparing. (8) Le(t cOflsuicuxl6c1Ja5 a result of cl'ld-Sl<lb'C gbUCOln:I. Bil:ller.ll comuicled fields may be sccn H1 hy~teria. (9) Le(t cemml scOl:omtl a5

,)Cen in optic (relrobulbar) neuritis in mulliple sclerosis. (10) Upper altllUdinal hCllllanopia AS a rcsoll oi'bil:lrcraldt'SIRJClion of Ihe lingu.11 b'yri. (I J) Lower ahirudin.11 hemianopia a:> a rcsoh o(hil:ller..ll ~tRJCliOll of the cunei.

91

92 Chapter 17

B. The optic nerve projectS from the lamina cribrosa of [he scleral canal. [hrough the op­[ie canal, to Ihe op[ic chiasm.

1. Transection causes ipsilmeral blindness, wi[h no direc[ pupillary light renex.

2. The section of the optie ner"e at the optic chiasm rransecTS all fibers from ·[he ip­silateml retina as well as fibers from the contralateral inferior nas..'ll quadram thatloop into the optic nerve. TIl is lesion cauS\."'S ipsilateral blindness and a comralat­eraJ upper temporal quadrant defect (junction scotoma).

C. The optic chiasm contains decuss..'lting fibers from [he twO nasal hemirClinas. It con­mins noncrossing fibers (rolll [he twO Icmpoml hemiretinas and projects fibers to Ihcsupmchiasmatie nucleus of the hYP()Ihalamus.

1. Mids.1gittal transection or pressure (o(ten from a pituitary tumor) causes bitem·poral hemianopia.

2, Bilatcrallatcral compression causes binasal hemianopia (calcified interna I carotidarteries),

D. The optic tract contilins fibcrs (rom the ipsilateral temporal hcmirelinil ilnd dH.'contralateral nasal hemiretina. It projecls to the ipsilaterallarcral geniculate body,prelccral nuclei. and superior colliculus. Transection C<IUseS cOlllralareral herni­'lIlopia.

E. TIle lateral geniculate body is a six-layered nucleus. Layers 1,4, and 6 receh'e crosseJfibers; layers 2, J, and 5 receive uncrossed fibers. The klleml geniculare bod)' rccci,'esinput from I:lyer VI of the striarc correx (Brodmann's area 17), h also receives fibersfrom the ipsilateml temporal hemirc[ina and ,he commlatcml nas..11 hemire[ina, IIprojects thrO\lgh the geniculocakarine tr,lct to la)'er IV of the primary ,'isual coru'x(Brodmann's area 17),

F. Thc gcniculocalcarine tmct (visual radiation) projects [hrough twO divisions to thevisual cortex.

1. The upper division (Figure 17·2) projects (Q rhe upper bank o( the calcarine sul­cus, the cuneus. It conrains inplll from the superior retinal quadranls, which rep­resem the inferior visuallie1d quadmnts,a. Transection causes a contmlmcmllo\\'er quadrantanopia.b. Lesions that im'olve bOlh cunei cause a lower alrirudinal hemianopia (alii.

rudinopia),

2. The lower division (see Figurc 17·2) loops from ,he lateral geniculate body anle·riorly (Meyer's loop), rhcn POStcriorly, [0 terminare in the lower bnnk of the cnl·carine sulcus, the lingual gyrus. It contains input from the inferior retinal quad.mnts, which represent the superior visuallield quadrants.a. Transcction causes a contmlatcral upper quadrantanopia ("pic in the sky"),b. Transection o( both lingual gyri causes nil upper altitudinal hemianopia (ai­

titudinopial,

G, The ,'isual cortex (Brodmann's area 17) is locared on [he banks of Ihe calcarine lis·sure, The cuneus is rhe upper bank. The lingual b')'rus is the lower bank. Lesions causecontmlateral hemianopia wirh macular sparing. The ,'isual conex has a rctinotopicorgani:ation:

1. The posterior area receh·es macular input (cemral vision).

2. The interml'diate area receives parmnacular input (peripheral inpur),

3. The anterior area recch'es monocular input.

Visual System 93

FIeld detects

Lower r. homonymous quadrantanopia

Lesion A 01 visual radiations tosup. bank of calcarine sulcus

III

~,,~~~~/8Z..::c;~~r~ ~Loop 01 Meyer ..- / Upper r. homonymous quadrantanopia

/Lesioo B of visual radiations 10

info bank 01 calcarine sulcus

lat. geniculate body,

Figure 17-2. Rekltions of the left tipper ,md left lower divisiorl5 of the geniculocalcarine tract to the lateralventricle and calcarine sulcus. TnmsectiOIl of the upper division (A) results in right lower homonymous quad­rantanopi;l. Tmnscctioll of the lower division (8) results in right upper homonymous quadmntanopia.(Reprinted with permission from Fix JD: BRS NeurOOlltllomy. Baltimore, Williams & Wilkins, 1997, P 261.)

III. THE PUPILLARY LIGHT REFLEX PATHWAY (Figure 17-3) has an afferent limb(eN II) and an efferem limb (CN III). It includes the following S[[ucrures:

A. Ganglion cells of the retina, which project bilaterally to the pretectal nuclei

B. The pretectal nucleus of the midbrain, which projects (through the posterior com­missure) crossed and uncrossed fibers to the Edinger-Westphal nucleus

C, The Edinger.Westphal nucleus of eN III, which gives rise to preganglionic parasym·pathetic fibers. These fibers exit the midbrain with CN 111 and synapse with postgan­glionic parasympathetic neurons of the ciliary ganglion.

D. The ciliary ganglion, which gives rise to postganglionic parasympathetic fibers. Thesefibers innervate the sphincter muscle of the iris.

IV. THE PUPILLARY DILATION PATHWAY (Figure 17-4) is mediated by the sympa­thetic division of the autonomic nervous system. Interruption of this pathway at any levelcauses ipsilateral Horner's syndrome. It includes the following structures:

A. The hypothalamus. Hypothalamic neurons of the paraventricular nucleus project di­rectly to the ciliospinal center (TI-T2) of the intennediolateral cell column of thespinal cord. ~

B. The ciliospinal center of Budge (Tl-T2) projects preganglionic sympathetic fibersthrough the sympathetic trunk to (he superior cervical ganglion.

C. The superior cervical ganglion projects postganglionic sympathetic fibers through theperivascular plexus of the carotid system to the dilator muscle of the iris. Postgan­glionic sympathetic fibers pass through the tympanic cavity and cavernous sinus andenter the orbit through the superior orbital fissure.

94 Chapter 17

Posterior commissure

Prelectal nucleus

Brachium ofsuperior oollic1Jlus-7<

Eamger-Weslpl'\al )><fl'\­nucleus of CN III

Red nucleus

cerebral aqueduct

Thalamus

~\;-,\--Medial genic1Jlatenucleus

lateral geniculate

"""""Crus cerebri

,....,,,-CN II

~","- Retinal ganglionic cell

~::~ ;?4L Sphincter muscle of Iris

Figure 17-3. TIle pUllilbry light P;llh\\~I\,. Lighl shinl-d illlO one eye C;UlSCS bOlh pupils 10 cOlulric!. The re­Spol'ISC in the stimubtcd ere is called dw din-oct pupilbry liglll retlex. TIle rc.>pol"ISC in the opposite eye is c:III..,.;Ithe consensual pupilla'1' light reflex. eN - cmnial ner'..e.

V. THE NEAR REflEX AND ACCOMMODATION PATHWAY

A. The cortical visual pathway projects from the primM)' visual conex (Brodmann's :Irea17) to the visual association cortex (Brodm:mn's area 19).

B. The visual associ;ltion cortex (Broomann's area 19) projecrs through the conico­rectal tr:lCl to the superior colliculus and pretectal nucleus.

C. The superior col1iculus and pretectal nucleus projcct to the oculomotor complex ofthe midbrain. TIlis complex includes the following smlclures:

1. TI,e rostral Edinger,\\'estphal nucleus. which mediates pupillary constrictionthrough the ciliary I,':tnglion

2. TIl(' caudal Edinger.Westphal nucleus, which mediates contrnction of the ciliarymuscle. This contraction increases the refractive power of the lens.

3. TIle mediall"(.octus subnucleus of eN 111, ",hich mediates convergence

VI. CORTICAL AND SUBCORTICAL CENTERS FOR OCULAR MOTILITY

A, The frontal eye field is locauxl in the posterior pan of lhe middle fromal gyrus (Brod·mann's area 8). It regulates voillmary (saccadic) eye movementS.

Visual System 95

A •~ i&5 ~ iOO:) .~ ~

e Flashlight swung from right eye to left eye e Looking straight ahead

C 0 cit.~ aD ~ ~ ~ aD ·aenLooking righl Looking left Eyes converged LooIOng straight ahead

E F G

~ aD ~ zr=]$ ~ illi ·Efu CiiLooking right Looking up Eyes converged Looking left and down

H I J

fi%. illi Efu ~ .~ ib a tr!j~

No reaction to light Eyes converged Eyes of a comatose patienl Looking straight ahead

Agure 17-4. OcUIHr mOlOf p:lbics and pupillal')' s)"IldmmL"S. (A) Rebrive ll(("relll (M:lrcUS CunnI pupil. lefteye. (0) Homer's syndrome. le(t e)·c. (C) huemUc!CHr opluhalrnuplcgi'l, right cye. (0) TIlird·ner....e lJHls)', lefteye. (E) Sixth·nerve pals\', right eye. (F) P:lrnl)'sis o( upw;.lfd gaz" and COIl\"erl,'encc (Parinaoo's syndrome). (G)Founh·ncrve pollsy, right eyc. (H) AIb'Yll RobertsOn pupil. (/) DcSlfucti\"e lesion o( the righl (ronrHl C)'C tick!, U)Tllird-!lL'f\'e 1l111sy with ptosis, righl eyL'.

1, Stimulation (e,g" from an irrimrive lesion) causes contralateral deviation of theeyes (i.e" away from the lesion).

2. Destruction causes transient ipsilatcml conjul,;ate deviation of the eyes (i.e.• to­ward the lesion).

B. Occipital eye fields arc located in Brodmann's areas 18 and 19 of the occipirallobes.These fields nrc corticnl centers for involuntary (smooth) pursuit and tr:leking move·ments. Stimulation causes contralateral conjllg:ue deviation of the eyes.

C. The subcortical center for lateral conjugate gaze is locared in the abducent nucleusofrhe pons (Figure 17-5). Some authorit ics place the "center" in the pammedian pon­tine reticul:lr formation.

1. It receives inpu(from the contr.:llateral frontal eye field,

2. It projects to the ipsilater..lliateml recrus muscle :lnd, through the mediallongitu.dinal (:lsciculus (MLF). ro the comraknemllllCl.lial rectus subnucleus of the ocu·lomotOr complex,

D. The subcortical center (or vertical conjugate ga:e is loc3[l.-'C! in Ihe midbmin at theIc\'c1 of the posterior commissure. II is called Ihe rostral interst itial nucleus of the MLFand is associated with Parinaud's syndrome (sec Figurl.-'S 14-}A and 17·4F),

96 Chapter 17

Bilateral MLF syndrome

- Lelt

A et'!~ t:::~-. ,

-+-Right -

B it:~ ~. ........

Convergence

C e:~ <~t):

Patient with MLF syndrome camotadduct the eye on attempted lateralconjugate gaze, and has nystagmusin abducting eye. The nystagmus isin the direction ollhe large arrow-head. Convergence remains inlaet.

Right MlFLeIt MLF

Medial rectussubnucleus01 CN III

I Lateral rectus musde~

I~A!I\J\ ~\'--/~

Medialrectusmuscle

Midbrain

Figure 17-5. GJnnt'clions of lhe pOlllino: cemer for hlteml conjugtUc gll:C. Lesions of the medi:lllnngiludi­1l;t1 (;lsciculus (MLF) between the ;llxlucem :lnd oculomotor nuclei result in l1lcJiall"t-"(:IUS pals\' {HI aucrnplcJhueT:II conjug;I1C gaze and horizonlal n\'stagmus in the ;llxlucfing eye. Convergence remains intaCl (inwr). A un i­hueral MLF lesion would afTec! only the ipsiblcmlmcJial recrus. eN "" CT:lllhll nerve.

VII. CLINICAL CORRELATION

A, In MLF syndrome, or internuclear ophthalmoplegia (sec Figure 17·4), [here is dam­age (dcl1\)'din:uion) [0 the MLF between the Ollxluccnt and oculomoror nuclei. Itcauses medial rectus palsy on attempted lateral conjugate ga:e and monocular hori­:omal nystagmus in d\e alxluc[ing eye. (Convergence is normal.) TI\is syndrome ismost commonly seen in multiple sclerosis,

B. One-and-a-half syndrome consists of bilaternl lesions of the MLF and a unilatemlle­sion of the abducent nucleus. On aucmptcd latcml conju&"lte ga:e, the only musclethm functions is the intaCtlmeral rectus.

C. Argyll Robertson pupil (pupillary light-ncar dissociation) is the absence ofa miOticreaction to light. both direct and consensual. with the preservation of:1 miOlic rcac­tion to n(Oar stimulus (accommodation-eon\'ergcnce). It occurs in s\,philis anddiabet(Os.

Visual System 97" " , .

D. Horner's syndrome is caused by mmscction of the oculosympathetic pathway at anylevel (see IV). This syndrome consists of miosis. ptosis. apparent enophthalmos, andhemianhidrosis.

E. Relative afferent (Marcus Gunn) pupil results from a lesion of the optic nerve, theafferent limb of the pupillary light reflex (e.g.. retrobulbar neuritis seen in multiplesclerosis). The diagnosis can be made with the swinging flashlight test (see Figure 17­4A).

F. Transtentorial (uncal) hemiation occurs as a result of increased supratentorial pres~

sure, which is commonly caused by a brain tumor or hematoma (subdural orepidural).

1. The pressure cone forces the parahippocampal uncus through the tentorial in·cisure.

2. The imp.1.cted uncus forces the contralateral crus ccrebri a~,'ainst the tentorial edge(Kemohan's norch) and putS pressure on the ipsilaternl eN III and posterior cere·bral anery. As a result, the following neurologic dek'Cts occur.a. Ipsilateral hemiparesis occurs as a result of pressure on the corticospinal tract.

which is locared in the contralateral crus cercbri.b. A 6.."ed and dilated pupil, ptosis, and a "down-and-out,,, eye are caused by

pressure on the ipsilateral oculomotor nern~.

c. Contralateral homonymous hemianopia is caused by compression of the pos­terior cerebral artery, which irrigates the visual cortex.

G. Papilledema (choked disk) is noninflammatory congestion of the optic disk as a re­suh of increased intracranial pressure. It is most commonly caused by brain rumors.subdural hematoma, or hydrocephalus. It usuall)' does not alter visual acuity, but itmay cause bilateral enlarged blind spots. It is often asymmetric and is gre:uer on theside of the supratentorial lesion.

H. Adic's pupil is a large tonic pupil that reacts slowly to light but docs react to ncar (Iight­ncar dissociation). Frequently sccn in females with absem knee or or ankle jerks.

9.

1.8Autonomic Nervous System

I. INTRODUCTION. The autonomic nervous system CANS) is a general visceral efferentmQlOr system that controls and regulates smooth muscle, cardiac muscle, and glands.

A. The ANS consists of (Wo types of projection neurons:

1. Preganglionic neurons

2. Postganglionic neurons. Sympathetic ganglia have imcmcurons.

B. Autonomic output i5 conrrolled by the hypothalamus.

C. TI,c ANS has three divisions:

1. Sympathetic. Figure 18-1 shows the symp:uhctlc innenr(uion of the ANS.

2. Parasympathetic. Figure 18-l shows the parasympathetic innen"ariono(the ANS.Table 18-\ compares the effects of symp:llhClic and p.1r3symp:Hhcric aClivilY onorgan sySl'cms.

3. Enteric. TIle emeric division includes the intramural ganglia of the g:lSlrointesrj.nal trner, submucosal plexus. and myenteric plexus.

II. CRANIAL NERVES (CN) WITH PARASYMPATHETIC COMPONENTS ;ndud,dlC following:

A. CN III (ciliary ganglion)

B. CN VII (ptcrygopalatine and submandibular ganglia)

C. CN IX (olic ganglion)

D. CN X [rerminal (mural) ganglial

III. COMMUNICATING RAMI of the ANS include:

A. White communicating rami. which are found berwcen T· J and L·3, arc myelinatcd,

B. Gray communicating rami, which are found at all spinallcvc1s, arc unmyelinated.

IV. NEUROTRANSMITTERS of [he ANS includc:

A. Acetylcholine, which is rhe neurotransmitter of the preganglionic neurons

B. Norepinephrine. which is rhe neurmrnnsminer of the posq.'<lnglionic neurons. withthe exception of sweat glands and some blood vessels that receive cholinergic sympa­thetic inner\'ation

C. Dopamine. which is the neurotransminer of rhe small intensely fluorescent (SIF)cells, which are interneurons of rhe sympathetic ganglia

Autonomic Nervous System 99

,p Tarsal muscle

..__------1.;.< J

..

, , lacrimal gland

"Eye: dUator ol pupil

St.tJmandibular andsublingual glands

Parotid gland

.....T+,

•1!~

" Bronchial tree~1! ~lac plexus•..•1l, "-rio< .""""'"E

'<. " rnesentelic plexus

~

¥ Small intestine•l Adrenal medulla'

•>i Large intestine

;;;;

J~ Inferior

L·3mesenteric plexus

~ Ductus deferens

,, ,, ,, ,, ,, ,, Sympathetic trunk'

Figure 1.8-1. Thc sympmhcric (thoracolumoor) inncl'o'ation of the alilonomic ncl'o'OUS SYSlcm. TIle emiresymp:tthelic innerv:llion of the head is through rhe superior cCI'o'ical g;lIll;lion, Gnly cOnlmunicatinl: nlmi ,uefound :1( :lll spinal cor.:llevcls. While communic:lting nlllli arc found only in spinal segments T·I throol;h L·J.

100 Chapter 18

MedullaDorsal motor " ,

nucleus 01 "vagal nerve,'

Ciliary gangion

Pterygopalatne gangion

Eye: constrictorof pupil anddiary body

~"'"~~"""

5__

and sublingualglands

Parotid gland

Hear1

Bronctial tree

Stomactl

SmaB intestine

""- large intestinetJt

5-25-3 V5-4 Urinary bladder

Pelvic Asplanctnc

"""'"tW

GeoitaI erectile tissue

FIgure 18-2. The pamsymp:lIhclic (craniosacral) innervaliOll 0{ lhe aUlooomic nervous system. Sacral OUI­

/low includes 5q,'lllenu S-2 dUOUb"\ 5-4. Cranial ourflow is mediated through cranial nerves (CN) III, VII, IX,and X.

Autonomic Nervous System 101.

Table 18-1Sympathetic and Parasympathetic Activity on Organ Systems

Structure

E",Radial muscle of irisCircular muscle of irisCiliary muscle of ciliary body

Lacrimal glandSalivary glandsSweat glands

ThermoregulatoryApocrine (stress)

HeartSinoatrial nodeAtrioventricular nodeContractility

Vascular smooth muscleSkin. splanchnic vesselsSkeletal muscle vessels

Bronchiolar smooth muscleGastrointestinal tract

Smooth muscleWallsSphincters

secretion and motilityGenitourinary tract

Smooth muscleBladder wallSphincterPenis. seminal vesicles

Adrenal medulla

Metabolic functionsLiver

Fat cellsKidney

Sympathetic Function

Dilation of pupil (mydriasis)

Viscous secretion

IncreaseIncrease

AccelerationIncrease in conduction velocityIncrease

ContractionRelaxationRelaxation

RelaxationContractionDecrease

Little or no effectContractionEjaculation-secretion of epinephrine and

norepinephrine

Gluconeogenesis andglycogenolysis

LipolysisRenin release

Parasympathetic Function

Constriction of pupil (miosis)Contraction for near visionStimulation of secretionWatery secretion

Deceleration (vagal arrest)Decrease in conduction velocityDecrease (atria)

Contraction

ContractionRelaxationIncrease

ContractionRelaxationErection-

•Note erection versus eJaculation: Remember point and shoot: p - parasympathetic, s - sympathetic.Reprinted with permission from Fix J: BRS Neuroanatomy. Media. PA, Williams & Wilkins, 1991.

O. Vasoactive intestinal polypeptide (VIP), a v;lsodi!awr that iscolocalized with acetyl.choline in some postganglionic parasympathetic fibers

E. Nitric oxide (NO). a newly discovered neurotransminer that is responsible for the reolaxation o( smooth muscle. h is also responsible (or penile erection (sec Chapler 22).

V. CLINICAL CORRELATION

A. Megacolon (Hirschsprung's disease, or congenital aganglionic megacolon) is char­acteti:ed by extreme dilation and hypertrophy of the colon, with fecal retention. andby the absence of ganglion cells in the myenteric plexus. Ir occurs when neural crestcells do not mif,'fOne into The colon.

B. Familial dysautonomia (Riley.Day syndrome) predominantly affects Jewish chilodren. h is an autosomal recessh'e trail that is characterized by abnonnal swearing. un·

102 Chapler 18

smble blood pressure (e.g., orthosmtic hypotension), difficulty in feeding (as a rcsuhof inadequate muscle (one in the gastrointestinal tract), and progressive sensory loss.h results in the loss of neurons in the au(onomic and sensory 1p.nglia.

C. Raynaud's disease is a painful disord("r of the terminal arteries of the extremities. It ischaracteri:ro by idioparhic paroxysmal bilareral cyanosis of the digirs (as:l resuh ofar­rerial and :lrteriolar consrriClion because ofcold or emorion). It may be uemro by pre­grmglionic sympathectomy.

D. Peptic ulcer disease results from excessivc production of hydrochloric acid occause ofincreased parflsympflthetic {tone) stimulation.

E. Horner's syndrome (see Chapter 17) is oculosympathetjc paralysis.

F. Shy-Drager syndrome involves preganglionic symparheric neurons from rhe inter­mroiolareml cell column. It is charocteri:ro by orthostatic hypotension, :lnhidrosis,impotence, and bladder atonicity.

G. Botulism. The toxin ofClostridilfln oondimtffi blocks the release of acerylcholine andresults in paralysis of aU striated muscles. Autonomic efreer;;; include dry eyes. drymouth. and gastrointestinal ileus (oowcl obstruction).

H. Lambert-Eaton myasthenic syndrome (St.'e Chapter 22)

1.9Hypothalamus

I. INTRODUCTIONA. General structure and function. The hYPOlhalamus is a division of Ihe diencephalon

that subscn'CS three systems: the autonomic nervous s)'srcm. enJoerine system. andlimbic system. The hypmhalamus helps to maintain homOOSlasis.

B. Major hypothalamic nuclei and their functions

1. TIle medial preoptic nucleus (Figure 19-1) rC!.'lllarcs th" release of !,'Onadotropichormones from rhe adenohypophysis. It contains the scsuall)' dimorphic nucleus,the de'l'e1opment of which depends on tcsrosu.'ronc lcn~ls.

2. The suprnchiasmaric nucleus receives direct input (rom the retina. h pbys a rolein the regulation of circadian rhythms.

VentromedIal nucleus• satiety center• destruction results in obesity

and savage behavior

Mamlltary body• receives input from

hippocampal formationvia lornix

• projects to anterior nucleusot thalamus

• contains hemorrhagic tesionsin Wernicl<e's encephalopathy

Dorsomedial nucleus• stimulation results in obesity and savage behavior

Posterior nucleus• thermal regulation (conservation 01 heal)• destruction results in inabilily to thermoregulate• stimulates the sympathelic NS

Lateral nucleus• stimulation induces eating• destruction results in slarvation

Arcuate nucleus• produces hypolhalamic releasing lactors• contains DOPA-ergic neurons thaI inhibil prolactin release

Paraventricular and supraoptIc nuclei• regulate water balance• produce ADH and oxytocin• destruction causes diabetes insipidus• pamvenlricular nucleus projects to

autonomic nuclei of bminstem andspinal cord

Anterior nucleus• thermal regulation

(dissipation ot heat)• stimulates parasympathetic NS -11~{/1(i'l;;j~• destruction results in hyperthermia

Preoptic area• contains sexual dimorphic nucleus• regUlates release of gonadotropic

hormones

Suprachlasmatlc nucleus• receives inputlrom retina• controls circadian rhythms

Agure 19-1. Major hypOlh:Lhllnic nuclei and their fUllcriolls. ADH =:uuidiurclic honnonc; eN =cranialnerve; DOPA = Oop;.llll1ne; NS = nervous system,

1.3

104 Chapter 19

3. TIlC anterior nucleus plays a rolc in remperature regulation. It stimulates theparasympmheric nervous system. Destruction results in hyperthemlia.

4. The paraventricular nucleus (Figure 19-1) synthesizes ~mridiureric hormone(ADH). oxytocin, and corticotropin-releasing hormone. It gives rise to rhesuprnopricohypophyseal tract. which projectS to the neurohypophysis. It regulateswater balance (conservation) and projects directly to the autonomic nuclei of thebrain stcm and all levels of thc spinal cord. Desrruclion results in diabetes in­sipidus.

S. The supraoplic nucleus synthesizes ADH and oxytocin (similar [0 the par-lVen­tricular nucleus).

6. The dorsomedial nucleus. In animals. So'wage behavior resultS when this nucleusis stimulated.

7. The ventromedial nucleus is considered a satiety center. When stimulated, it in­hibits the ut},'e to eat. Bilateral destruction results in hyperphagia. obesity. and sav·age bcha\·ior.

Paraventricular nudeus

ThO'"ventricle Atcuate (tubefal) nucleus

Tuberohypophyseallract

Posterior lobe (neurohypophysis)

Supraopl~ypophyseal trael

Sinusoids of infundibular stem

_ ~~ocin

Hypophyseal vein

Inlerior hypophyseal artery

Supraoptic nucleus-tte;,.;~

Opticchiasm

Hypophyseal portal veins~~

Superior hypophyseal artery

Anterior lobe (adenohypophysis)

Figure 19-2. The hypophyscal porrol] s)'stem. The paraventricular and supmoplic nuclei produce antidiuretichormone (ADH) (Ind OXytOCill and transpon: them through the supraopticoOypopnyseal Inlel 10 the capillarybed of the ncuroll)·J'Ophysis. The arcuate nocleus of the infundibulum transport$ hypothalamic-stimulating hor­moncs through the wbcroh)'pophyseal nact to the sinusoidsof the infundibular srem. 1bese sinusoids Ihen draininto Ihe sccondary capillary plexus in the adenoh)l)ophysis.

Hypothalamus :1.05

8. The arcuate (infundibular) nucleus contains neurons that produce facwrs thmstimulate or inhibit the action of the hypothalamus. This nucleus gives rise tothe tulx-rohypophyseal tmct, which tenninates in the hypophyseal ponal system(sec Figure 19-2) of the infundibulum (medium eminence). It coma ins neuronsthat produce dopamine (i.e., prolactin-inhibiting factor).

9. The mamillary nucleus receives input from the hippocamJXlI formarion rhroughthe po:5tcommissural fornix. It projecrs [0 the anterior nucleus of rhe thalamusthrough the mamillorhalamic tract (pan of the Pape: circuit). Patients withWernicke's encephalopathy. which is a thiamine (\'itamin BI ) deficiency. ha\'elesions in the mamillary nucleus. Lesions are also associatt.-d with alcoholism.

10. The posterior hypothalamic nucleus plays a role in thermal I\.""gularion (Le.,consct\'ation and increased production of hear). Lesions result in poikilother­mia (i.e.• inabili[)' [0 thermoregulate}.

11. The lateral hypothalamic nucleus induces eating when stimulated. Lesionscause anorexia and starvation.

C. Major fiber systems of the hypothalamus

1. The fornix is the largest projection to the hypothalamus. It proj(>Cts from the hip­pocampal formation ro the mamillary nucleus. anterior nucleus of the thalamus.and sepral area. The fornix then projects from the sepral area to Ihe hippocampalfomlation.

2. The medial forebrain bundle trnvcrscs the entire Iaternl hypothalamic area. It in­terconnecrs the orhitofromal conex. septal area. hypothalamus, and midbrnin.

3. The mamillothalamic tract projects from the mamillary nuclei to the anterior nu­cleus of the thalamus (pan of the Pape: circuit).

4. The stria terminalis is the major p<1thway from the amy/,tdala. It inrerconnect5 theseptal area, hypothalamus. and amygdala.

5. The supr"dopticohypophysial tract conducts fibers from rhe suprnoptic and par­avenlricular nuclei to the neurohypophysis. which is the release sitc for ADH andoxytocin.

6. The tuberohypophysial (tuberoinfundibular) tract conducts fibers from the ar­CUflre nucleus to the hYlXlphyscal portal system (see Figure 19-2).

7. The hypothalamospinal tract contains direct descending autO lOmic fibers. Thesefibers influence the preganglionic sympathetic neurons of th·,: inrcrmediolatemlcell column and prcgflnglionic neurons of the sacral pamsymp.lthet ic nucleus. [n­terruption above the first thol<lcic segment (T.\) Cflllses Honwr's syndrome.

II. FUNCTIONS

A. Autonomic function

.1. The anterior hyPothalamus has an excitatoT)' effect on the parasympathetic ncr­\'OUS system.

2. The posterior hypothalamus has an excitatory effect on the s)'mpathetic nervoussystem.

B. Temperature regulation

.1. The anterior hypothalamus re/,'lllates and maintains body tcmpernture. OcstnJc­tion causes hyperthermia.

106 Chapter 19

2. The posterior hypothalamus helps w produce and conserve heat. Destructioncauses dl(~ inability [0 thermoreguhue.

C. Water balance regulalion. The paraventricular nucleus synthesizes ADH, whichcomrols water excretion by the kidneys.

D. Food intake regulation. Two hypothalamic nuclei playa role in the control of ap­petitc.

1. When stimulated, the ventromedial nucleus inhibits the urge TO cat. Bilateral de­struction results in hyperphagia, obesity, and s."lVage behavior.

2. When stimulated, the lateral hypothalamic nucleus induces the urge to cal. De·struction causes starvation and emaciation.

III. CLINICAL CORRELATION

A. Diabetes insipidus. which is characterized by polyuria and polydipsia, is the Ix-stknown hypothalamic syndrome. It results from lesions of the ADH p.·nhways to theposterior lobe of the pituimry gland.

B. The syndrome of inappropriate ADH secretion is usually caused by lung tumors ordrug therap}' (e.g.• carbam3zepine, chlorpromazine).

C. Crnniopharyngioma is a congenital tumor thar originates from remnants of Rathke'spouch (see Chapter 4). This tumor is usually calcified. It is the most common supra­tentorial tumor in children and the most common cause of hypopituitarism in chil­dren.

1. Pressure on the chiasma results in bitcmporal hemianopia.

2. Pressure on the hypothalamus causes hypothalamic syndrome (i.e., adiposity, di·abetes insipidus, disturbance of temperature regulation, and somnolence).

D. Pituitary adenomas account for 15% of clinical symptomatic intracranial tumors.They arc rarely seen in children. When pituitary adenomas arc endocrine-active, theyC:lUSC endocrine ahnonnalities (e.g., amenorrhea :Ind galactorrhea from a prolactin­secrcring adenoma, rhe most common typc).

1. Pressure on the chiasma results in bitemporal hemianopia.

2. Pressure on the hypothalamus may cause hypothallllnus syndrome.

20Limbic System

I. INTRODUCTION. The limbic system is considered the anatomic substrate Ihm under­lies bchaviomJ ..ndemotional expression. It isexprcsS<.'(llhrough the hypothalamus by wayof rhe "Ulonamic nervous system.

II. MAJOR COMPONENTS AND CONNECTIONS

A. 111e orbilofronlal cortex mediates the conscious perception of smell. II has recipro­cal connections wilh rhe mediodorS;ll nucleus of the L1mlamus. It b inlcrcQnne<:tedlIuough the medial forebrain bundle wid, the septal area anJ hypOIhalamic nuclei.

B. The mediodorsal nucleus of the thalamus has reciprocal connections wilh the or­bitofronlal;md prefronml cortices as well as the hypothalamus. It rccci\'t"S input (romthe am)'gJab and plays a role in affective behavior anJ memory.

C. The anterior nucleus of the thalamus receives iopur from the mamillary nucleusthrough rhe mamillorhalamic tract and fornix. It projects to the cingulare gyrus andis a major link in ,he Pape: circuiL

D. The sepral area isa telencephalic structure. It has reciprocal connections with the hip­Ix>campal formation through the fornix and with the hypothalamus through the me­dial forebrain bundle. It projects through the stria Tll<.-duUaris (thalami) to the habe­nular nucleus.

E. The limbic lobe includes the subcallosal atea, paraterminal gyrus, cingulflte gyrus andisthmus, <lnd parahippocampal gyms, which includes dl(' uncus. It cont"ins, buried inthe parahiPIx>campal gyms, the hippoc:unpal formatiOl' and amygdaloid nucle"r com·plex.

F. The hippocampal formation is a sheet of archicorrcx that is jelly-rolled into theparahippocrllllpal gyrus. It functions in leflrning, mcmory, and recognition of novelty.It receives major input through the entorhinal cortex and projects Ilmjor outputthrough the fornix. Its major structures include the following:

1. The dentate gyrus, which has a three-layered archicorrex. It conrainsgnmule cellsthai receive hipPQ:amJXII input and project Output to the pyramidal cells of thehippocampus and subiculum.

2. The hippocampus (cornu Ammonisl, which has a three-la)'ered archicortex. Itcontains pyramidal cells ,hat project through the fornix ro the sepral [Irea and hy.porhalaTllus.

3. The subiculum, "'hich receives input rhrough rhe hippocampal pyramidal cells. Itprojects through the fornix to the mamillary nuclei and rhe anrerior nucleus of Ihethalamus.

107

108 Chapter 20

G. The amygdaloid complex (amygdala) IFigurc ZO.I; see also Figure 21.11 is a b..'lsal gan­glion that underlies the parahippocampal uncus. In humans, stimukuion causes fearand signs of s}'mpmheric overnctivity. In othcr animals, stimulation resulrs in cess..... ·tion ofactivity and heightened attenriveness. Lesions cause placidity and hypersexualbehavior.

1. Input is from the sensory associ:nion cortices, olfactory bulb and cortex, hypo.thalamus and sepral area, and hippocampal fonnarion.

2. Output is through the stria tcrminalis [0 the hypothalamus and scpml arca. TIlercis :llso output to rhe mediodors:ll nuclcus of the thalamus.

H. TIle hypothalamus h:ls reciproc:ll connections with the :lllly!.'<bla.

I. TIle limbic midbrnin nuclei and associ.ned neurotransmitters include rhe ventraltegmental arca (dopamine), ",phe nuclei (sctownin). and locus ceruleus (norepi·nephrine).

III. THE PAPEZ CIRCUIT (Figure 20·2) includes rhe following limbic struCtures:

A. The hippoc:nnp<ll formation, which projects lhrough the fornix 10 the mnmillary nu·c1eus ,lIld septal area

B. TIle mamillnry nucleus

Hippocampallonnation

7 ,-Stria tenninalisix······~ _. .

5eptaI area Hypothalamus

VAFP/VAPP,-.

of Broca •••• ---~.-, . --

.Olfactory bulb and : Autonomic centers

olfactory cortel(Amygdaloid nllCleus

or brain stem

,,VAFP/VAPP

Sensory associationand ~mbic cortices

Fom

Diagonal band

Agure 20-1. Millor connections of the amy~>dalo;d nucleus. This nucleus receives input from three majorsources: Ihe olfaclOry S~lem, SCfUOry a$SOCiarion and limbic cortices, and hyporhalamlls. Majorompm is throughtwO channe1s: [he stria teml;n:.lis projects to Ihe h)"poIhal:.mu~ and rhe .seplrJl llTC3. and rhe \'entr,l! amyg­dalofugal p.1rhway (VAH') projects 10 the hyporhalamus. brain stem, :md spin:ll cord. A sm;lller effel'\'nt bundle.rhe dia~'OIla1 band of Broca, projc.'Cu to the .septal :ll'\'a. Affel'\'nt fibers {rom the hypothalamus .md brain SH:m en­ler Ihe amygd.1loid nucleus lhrough the \'entral am\,~>dillopct<ll pmh~~.y (VAPP).

Limbic System 109

Figure 20-2. Major ~Jf(('rent and efferent limbicconnections of the hippocllmp,11 (ormation. TIlis forma·tion hllS three components: the hippocampus (cornuAmn"lOllis), subiculum, and dentale b"l·nIS. TIle hip­poc:nnpus proje<:ts to lhe scpml area, IIlC subiculum pro­jeers to lI,C mamillary nuclei, and lhe dencue b"l"tUSdoesllO( project beyond the hif'POCUmp;l1 (orm."ldon. Thecir­cuit of rape: (0110""5 [his route: hippocampal form."ltion[Q mamillary nuclcu:s to anterior thalamic nuclCU'l [Q

cingulmc b'YfUS 1O en[jxhinal C(l£tex 1O hippocmnpal (or­mation.

5eptaJ ""'.

Mamillary body

- - -- - _. Mammothalamictrnct

Anterior nudeusoI_~

- -- --- - -Anterior 6mb ofinternal capsule

Ciogulate gyrus

-- -- _••••••• -Cingulum --

Entorhinal cortex

t-- --------Perforantpalhway

H~

formation

C. The anterior thalamic nucleus

D. The cingulatc gyrus (Brodmann's areas 23 and 24)

E, The entorhinal area (Brodmann's area 28)

IV. CLINICAL CORRELATION

A. Kluver·Bucy syndrome results from bilateral ablation of rhe amerior temporal lobes.including the amygdaloid nuclei. It causes psychic blindness (visual agnosia). hyper­phagia, docility (placidiry), and hypersexuality.

B. Amnestic (confabulatory) syndrome results from bilateral infarction of the hip·pocampal formarion (i.e., hippocampal branches of rhe posterior cerebral arteries andanterior choroidal arteries of [he inrernal carotid arlcries). It causes anterograde am·nesia (j.e., inabiliry (() learn and remin new information). Memory loss suggests hip­pocampal pa[hology.

C. Foster Kennedy sy';!drome resul[S from meningioma of the olfactory groove. Themeningioma compresses rhe olfacrof)' traC[ and optic nerw. Ipsilateral anosmia andopric arrophy and conrralareral papilledema occur as a result of increased imracranialpressure.

D. The hippocampus is the mosr epileprogcnic parr of rhe cerebnnn. Lesions ma~' causepsychomotor arracks. Sommer's secror is very sensitive to ischemb.

E. Bilateral transection of the fornix may cause rhe aClllC amnesric synJrome (I.e., in·abili[y to consolidate shorr-rem memory inro long-rerm memory).

110 Chapter 20

Agure 20-3. Midsagirml SC(;tiOll rhrou,;h thebrain stcm and dicnccphalon showing the dimibu­rion of leiians in Wcmicke's encephalOfXlrhy. (A)Ml--dio,Jot~11 nuclcusofthe r1l<I!;IIII11S. (8) Massa in­rcn",,--dia. (C) Pcrh'enrricubr arC-d. (D) Mamillarynuclei. (£) Midbrain and pontine ll-'b'tllCntum. (F)In{crial- colliculus. Lesions in rhe m."I11lillary nucleian:: :1.iSOCimc.:1 widl Wemickcsenccph:llopi.lthy andlhi:unine (vimmin B.) ddiciency.

•A . ..

•B .:.C

F0

E

F. Wernickc's encephalopathy results from a thiamine (vitamin B1) deficiency. The clin­ical triaJ includes ocular dismrbances and nystagmus, gait ataxia, and mental dys­function. Pathologic features include mamillary nuclei. MD nuclei of the thalamus.and pcriaqueJucml gray and pontine tegmentum (Figure ZO-3).

G. Strachan's syndrome results from high-dose thiamine (vitamin 8 1) thempy. The clin­ical triad includes spinal ataxia, optic atrophy, and nerve deafness.

H. Bilateral destruction or removal of the cingulate gyri causes loss of initiative and in­hibition as well as dulling of the emotions. Memory is unaffected. Lesions of the :m­rerior cingulate gyri cause placidity. Cingulectomy is used to trear severe anxiety anddepression.

21.Basal Ganglia and Striatal Motor System

I. BASAL GANGLIA (Figure Zl-l)

A. Components

1. Cauda Ie nucleus

"ta~}Globus Lentiformpanidus nucleus

ippocampus

Fomil(

Internal _~~~fj~~#~-tt~~~capsule ~ ~~~~~~~~~~~~Claustrum -:;::lE":j;~:'!:!~

Third ~:~~~~~~~t q""'\;'" z..:::::l'C Subthalamicventricle nucleus

00"' 1m"Substantia nigra Maminary

I>ody

caudate

""'~"".~~ThalamUS~

FIgure 21·1. CoronalliCClloll Ihroul;!llhe miJth:.ll:nnlu:u the level of the m,'llllillary N.d.($. 1be rosa11o'<ln­glia are :.11 prominent lit this lcn~1 and include the striatum lind lentiform nucleus. 11lC :lUbthalamlc nudell) andsl.lhsr.mria nib'T3 are imrorrnm components of rhe )lrialal IllOlOr Sy)!CIll. eM = cenrmnl(~km nu<:lcu); VA =veruml anrerior nudell:>; VL = \"cmmll:lrcml nucleus.

1.1.1

112 Chapter 21

2. Putamen

3. Globus ~Ilidus

B. Grouping of the basal ganglia

1. The strialUm consisrs of the caudate nucleus and putfl.men.

2. The lentiform nucleus consists of the globus pallidus and putamen.

3. The corpus striatum consists of the lentiform nucleus and caudate nucleus.

4. The claustrum lies between the lentiform nucleus and the insular cortex. It h;l$reciprocal conncctions between the scnsory cortices (i.e., visual cortex).

II. THE STRIATAL (EXTRAPYRAMIDAL) MOTOR SYSTEM (.,., F;gme 21·1) pby,a role in the initiation and execulion of somatic mOlor activity, especially willed move­ment. It is also im·olved in automatic slcreorypt.-.J poslural and reflex motor activity (e.g..normal suhjccts swing their arms when they walk).

A. SlrUClUre. TIle suiaral motor system includes the following srruclUres:

1. Neocortex

2. Striatum (caudatoput'dmen. or neostriatum)

3. Glohus pallidus

Neocortex

<)0

~0

"VA, VL eM S1rlatum •,•,

Thalamus f~

~ 8~ ~

i}

::0

Subthalamic Globus • ~nucleus pallidus S

"-I if

Substantia anigra

IBl11in stem and

spinal cord

Figure 21-2. Major afferent :md efferent conneclions of lhe Strialal syStem. 1ne strialum receives major in·put (rom Ihrcc sources: Ihe thalamus. neocortex. and subsmmia nigra. 1ne striatum projccl5 10 the globus p;ll.lidus and substantia nigra. 111e globus p..llidus is Ihe e((<.'Clor nucleus of the Slri:ll~ll s}'stem; it projects 10 thc thal­amus and $ubd".hlmic llucleus. 111C substanlia nigr:1 also projects to dlC Ihabmus. 111e striatal motor systcm isc:-;prcsscd throul:h the conicobulb:lr and cOrlic05Pin;11 tmCts. eM = ccntrorncdian nucleus: GAOA "" ..,.aminobmyric lldd: VA = \'entr:ll anterior nucleus; Vl :so \'cnlr:lllatemi nucleus.

Basal Ganglia and Striatal Motor System U3

4. Subthalamic nucleus

5. Substantia nigra (i.e., pars compacta and pars rei icularis)

6. Thalamus (ventral anterior, ventral lateral, and ccntromcdbn nuclei)

B. Figure 21-2 shows the major afferent and efferent connections of the slrillml system.

C. Neurotransmitters (Figure 21-3)

III. CLINICAL CORRELATIONA. Parkin,;on's disease is a degenerative disease that affl"Cu the substantia nigra and its

projections to the striatum.

1. Results. Parkinson's disease causes a depletion of dopamine in the substantia ni­gra and striatum as well as a loss of me1anin·containing dopaminergic neurons inthe substantia nigra.

2. Clinical signs are bradykinesia. Stooped posture. shuming b':lil. cOb'whecl rigidity.pill-rolling tremor, and masked facies. Lewy bodies arc found in {he mclanin­conmining neurons of {he substantia nigra. Progrl'Ssive supranuclear palsy isassoci3led with Parkinson disease.

3. Treatment has been successful with L-Dop.1. Surgical intervention includes palli­dotomy (rigidity) and ventral thalomotomy (tremor).

on's disease)

struction results inatkinson's disease)

GLU GLUNeocortex Blain stem and

spinal cord

" , (Destruction results in Huntingt~

~ ....GLU • Dopamine

S. nigra:

Thalamus --"m Compacta • • (DeACh- • Relicularis -p

~ ~, GABAISP

I",,

I ~,

~ ~~ ,,

~ ~ ~,,,,

GLU,

Subthalamic Globus · - - - ~ (Lesions found here

nucleus pallidusin Wilson's disease)

• GABA,

, ,,, ,, ,

(Destruction resultsin hemlballJsm)

(Lesions found herein kernicterus)

Agure 21-3. M,ljor neurotr:.Illsminers of the slri"tal mOlOr SYSlem. Wllhin lIlI.' sHilltum,!:lohm rallidus. :mJpMS relicularis of the SUhsl,lll(ia nigr:1 (S. nigra). y-'lminoh.Jtyric :lCid (GABA) is the prl-dorninalll IlCurouans­mitler. GABA nlay COCXiSI in the same neuron with enh'ph:llin (ENK) or suhsronce P (SP). Dopamine­conminin!: neurons :Ire founJ in th~' p;.lrs comp;.lcm of lI,e substmuia nigr.l. Acelylchollne (ACh) is found in theloc;II circuli ncurolu of the slri:lIum. 11\e subthalmllic nucleus projecLS excimrOf)' glmmllinell:ic fibers lO theglobos 1:l.11Iidus. GI.U "" jl:lulalliate.

114 ChaPter 21

B. Methylphenyhetrahydropyridine (MPTPHnduced parkinsonism. MPTP is an analogof meperidine (DemelOl). It destroys dopaminergic neurons in the substantia nif,,1fa.

C. Huntington's disease (chorca) is an inherited autosomal dominant movement dis,order thm is traced ro a single gene defecr on chromosome 4.

1. It is associated with degenenltion of the cholinergic and y.aminoburyric acid(GABA),ergic neurons of the striatum. It is accompanied by gyml atrophy in rheftontal and temporal lobes.

2. Glutamate excitocoxiciry. GLU is released in the striatum and binds to its receprorson striatal neurons resulting in an action potental. GLU is removed from the extra·cellular space by astrocytes. In Huntington's disease GLU is bound to the N-methyl·D-aspanate (NMDA) receptor resu\[ing in an influx ofcalcium ions and subsequentcell death. This cascade of events with neuronal death most likely occurs in cere·brovascul:lr accidents (e.g., stroke).

3. Clinical signs include choreiform movements, hYJXItonia, ,md progressive de·mentia.

D. Other choreiform dyskinesias

1. Sydenham's chorea (St. Virus' dance) is the most common cause of chorea over­all. It occurs primarily in girls, typically after a bout of rheumatic fever.

2. Chorea gravidarum usually occurs during the second trimester of pregnancy. Manypmiems have a history of Sydenham's chorea.

E. Hemiballism is a movement disorder that usually results from a vascular lesion of ,hesubthalamic nucleus. Clinical signs include violcm contralateral flinging (ballistic)movements of one or both e"tremities.

F. Hepatolenticular degeneration (Wilson's dise,lse) is;m autosomal recessive disorderthat is caused by a defect in the mct,lbolism of copper. The gene locus is on chromo­.some: 13.

1. Clinical signs include choreiform or atherotic movements, rigidity, and wing~

beating tremor. Tremor is the most common neurologic sign.

2. Lesions are found in rhe lentiform nucleus. Coppcr deposirion in the limbus ofthe cornea gives rise to the corneal Kayser.F1eischer ring, which is a pathogno­monic sign. Deposition of copper in the Ih'er leads to muhilob.-.r cirrhosis.

3. Psychiatric symptoms include psychosis, personality disorders, and dementia.

4. The diagnosis is based on low serum ceruloplasmin, elevated urinary excretion ofcopper, and increOlsed copper concentration in a liver biopsy specimen.

5. Treatment includes penicillamine, a chelator.

G. Tardive dyskinesia is a syndrome of repetitive choreic movement that affect the faceand trunk. h results from treatmem with phenothiazines, bmyrophenones, or mew·c1oprnmide.

22Neurotransmitters

I. IMPORTANT TRANSMITIERS AND THEIR PATHWAYS

A. Acetylcholine is the major transmiuer of the pcriphernl ncn'Oll:. sy:m'm, neuromus­cular junction, parasympathetic nervous system, preganglionic symp:nhcric fibers. andp:>:sq;anglionic sympathetic fibers that inner....:ne SWe:lt glands and some hlOlXl ,'esselsin the skeletal muscles (Fil:.'ure 22-1). ACelylcholine is found in rhe neurons of the so­malic and visceral mowr nuclei in the brnin Sh'm and spinal cord. It is also found inthe basal nucleus of Meynert. which degencl"3tcs in AI:heimer's disease.

B. Catccholamines. Figure 22·2 shows the biosynrhcric pathway {orc:uccholamincs. Epi­nephrine. although a catecholamine, plays an insigninC:lIlt role as a central n('n:QUssystem neurotransmitter. In the body, epinephrine is found primarily in rhe adrenalmedulla. In thc ccntral neryous sysrcm. ir is rcsrricte<! to small ncuronal c1ustcrs in rhebrain stem (medulla).

1. Dopamine (Figure 22-3) is deplered in parients wirh Parkinson's disease and in­creased in patients with schi:ophrcnia. Dop..1mine is found in the arcuafe nucleusof the hypothalamus. It is the prolactin-inhibiting factor. Irs tWO major receptorsare Dl and Dl .

Acetylcholine (ACh)

Neocone~

~""9Nucleus basilis 0' Meyner1 in 'orebraink-- -'-- .'

(Alzheimer's disease)

Cranial nerve. molor neurons. andpreganglionic parasympalhetiC neurons

Spinal molor neuronsAUlooomic preganglionic neurons

Local cireuil neuronsin strialum (caudalopulamen)

Hippocampallormalion

Agure 22-1. DistribUlion of acelylcholine-comaining neurons :Illd their axonal projccllons. Tl'IC ha~ll nu·deus of Meynert rrojcclS 10 Ihe emire COrtcx. Tllis nucleus dcb'CncTmcs in pmicllls with Al:heimcr's dbeas<:'.5uiaml accl)'lcholinc Ioc:ll circuiT neurons deb'Cnerare in p;lliems wirh Huntinuwn'~ d,...ca;;c.

1.15

1.16 Chapter 22

Tyrosine

Tyrosine hydroK)ifase

L-Dopa

Oops d9C8tboxy1ase

Dopamine

Norepinephrine

I'henyMthanoIatnine N-methyt transferase

Epinephrine IAgure 22-2. Symhesis of catecholamines (romphenylalanine. Epinephrine:. which isderived (rolll nor­epinephrine. is found primarily in the adrenal medulla.

a. 0l receplors are postsynaptic. They activate adenylate cyclase and are exci­tatory.

b. O2 receptors arc both postsynaptic and presynaptic. TI,ey inhibit ::ldcnylatcCyciOlSC and arc inhibitOry. Antipsychotic drugs block O! receptOrs.

2. Norepinephrine (Figure 22-4) is the transmitter o( mOst postganglionic sympa­thetic neurons. Antidepressant drugs enhance its transmission.a_ Norepinephrine plays a role ill anxiety slates. Panic attacks are believed to re­

sult (rom paroxysmal discharges from rhe locus ceruleus. where norepineph­rinergic neurons arc found in Ihe highesl concenlTmion. Most poslsynaptic re­ceplOTS of Ihe locus ccruleus palhway are 13 1 or 131 receptoTS thar activatea<!('n},late cyclase and ar(' excitatory.

Dopamine

k'''----Cerebellum

""'"MedoRa

Nigrostriatal tl8Cl~~,

Ventral tegmentalarea 01 midbrain

-"'Substantia nigra of rnidbfain

Mesolimblc Iract (mesocoltlcal tract)

~v-<~=~-:/'<::CorpuS callosumUmbic coltex (cingulate gyrus Striatum (caudatenUCleus and putamen)

\~-SplnoJ ""'"Figure 22-3. DisrriOOlion of dopamine-conmininG neurons and Iheir projcclioru. Two mlljor ascendingdopamine f'atll\\~lYS arise in the midhmin: the nigrostri:mll tmct from the subst;Ulti,1 niGra and the mesolimbictmct from the \'~nlral tcgm~nml ;lre'l. In patients with Pilrkin;;on's disease, loss of dopaminergic neurons occursin the subSlllntia nigra and the ventral teGmental area. Doplll1linergic neurons from the arcuate nucleus of thehl'l>Olhalallllls projecl to the portilll'esseis of the infundibulum. DopaminerGic neurons inhibit prolncl in.

Neurotransmitters ll7

Norepinephrine (NE)

Amygdala:::::::'~}::­locus ceruleus of pons and midbrain

Thalamus

Cerebellar corteI':

Flgure 22-4. D!~tnhUlion of nnrer;nephrint'-eOflfaininJ.; neur,IOS ,u'K.Ifhcir rnlJCCll0m. The l"cII. ccrult'us(1ocal~"<.I in the pons :md rnidbr,.in) is fhe chief 50tJrcc of Ilor.tdl'<'neq.:ic 6hcf". TIle locus c("rult·u~ I'roJt'cu h) 1111f"LnS of the cemml nervous S}·S'!("lll.

b, The cCltecholamine hypothesis of mood disorders sTall,'S th:.t r\..JucN norepi­nephrine activity is related to depression. and that incrca:.cd nllrcpincphrincactivity is relared to mania.

C. Serotonin [S-hydroxytryptamine (S~HT)] is an ind,olaminc (FiguTl.' 22-). Scrol:onin­containing neurons are found only in the r-dphe nuclei of fhe br..;n stem.

1. The permissive serotonin hypothesis states fhar when )-I-IT activity is rcJuced,decreased levels of catecholamines cause depression and insomnia. In addition,when )-HT acrh'iry is increased, elevated levels of c,lIccholamincs cause mania.Dysfunction of 5-HT may underlie obsessive-compulsivc disorJer.

2. CCTlain antidepressants increase )-HT availability by reducing its rellplake. )-HTagonists that bind )-HT1A and those that block )-HT! have antiJepreSS<l1ll prop­cnies. Fluoxetine is a SClcclive serotonin reupmke inhibitOr (SSRI).

D. Opioid pcptides (endogenous opiates) induce responses similar to rhose ofl\t'roin andmorphine.

1. Endorphins include f3-endorphin, which is the major endurphin (ounJ in thebrain. It is one of the most powerful analgesics known (48 times 1I10re potent thanmorphine). Endorphins arc found exclusively in the hYlxllhabmus.

2. Enkephalins are the most widely distributed and abundant opiate Ix:ptides. Theyarc found in [he highest concentration in the glubus pallidus. Enkepha1ins coex­ist with dop..'1mine, "'f-aminoburyric acid (GABA), norepinephrine. ;lnd ;lcClyl~

choline. They arc colocali~{'d in GABA·crgic pallidal neurons. ;lnd th\.·y playa rolein pain suppression.

3. Dynorphins folloll' the distribution map for enkephalins.

E. Nonopioid neuropcptides

1. Substance P plays a rotc in pain transmission. It is most highly cunccnrratt-d inthe substantia nigra. h is also found in the dor.;.,l TOOl ganglion cells :md sub:itan­tia gelatinQS.1. h is colocali:ed with GABA in the srri:uonigrnl tract and plays arole in movement disorders. Substance P le\'cls arc reducL-d in paticlUs withHuntin~..ton's disease.

us Chapter 22

Serotonin (S-HT)

Raphe nuclei inmidbrain. pons. and medulla

Spinal cord

Hippocampallormation

cerebellar cortex

TI)'plophan

~ Tryptophan-S-hydroxylaS6

SoHydroxylryptcphan

~ Aromatic L-amino acid d6catboJl)'faS6

serotonin (SoHydroxylryptamine)

Figure 22-5. Dbuibulion of 5.hydroxyll)'pl:lmine (serolOnin).conl,llning neurons :lnd their projcclions.Serolonin.conl:lining neurons are (ound in the nuclei o( the mphI,'. TIley proj"'C1 widch' to Ihe (ord)min, cere·bellum. and spin.,1 cord. TIle inset shows the symhetic IX'lh~':IYof .serof(>niJ>

2. Somatostatin (somatotropin~release inhibiting f;;.c!ur). Somatostatinergic neu·rons from the anterior hypothalamus project their ::rxons to the median eminence,where som:uost:uin enters the hypoph}'seal portal system and regulates the releaseof growth hormone and thyroid~stimulatinghormone. The concentration of s0­

matostatin in the neocortex and hippocampus is significantly reduced in patientswith AI:heimer's disease. Srri:ltal somatostatin 11,'\'1,'15 are increased in patientswith Huntington's disease.

F. Amino acid transmitters

1. Inhibitory amino acid transmittersa. GABA (Figure 22-6) is the major inhibirory neurotransmitter of the brain. Pur­

kinjc, stell<lte, basket, <lnd Goigi cells of the cerebellar cortex arc GA BA·ergic.(1) GABA-ergic striatal neurons project to the globulus pallidus ::mel sub-

st:llltb nigm.(2) GABA~ergic pallidal neurons project to t.he thalamus.(3) GABA-crgic nigral neurons project to the thalamus.(4) GABA receptors (GABA·A and GABA·B) are intimately associated

with bemodi<lzepine·binding sites. Bcmodia:epines enhance GABA ac·th'ity.(a) GABA-A receptors open chloride channels.(b) GABA-B receptors arc found on the terminals of neurons [h;lt use

:mmhcr transmitter (i.e.• norepinephrine, dopamine, serotonin).Activarion ofGABA-B recepwrs decreases the release of the othermmsmitter.

b. Glycine is rhe major inhibitory neurotrnnsmitter of the spinal cord. It is usedby Ihe Renshaw cells of the spinal cord.

Neurotransmitters 119

y-Aminobutyric acid (GABA)

Pur1dnje cells ofcerebellar cortex

local circuit GABA neuron

Hypothalamus

Substantia nigra (pars reticularis

Lateral vestibular nucleus

-~

~pan_,,_Striatum local circuit GABA neurons

Globus pallidusHypothaIamocort tract Nigrothalamic net

StrIatonigraltract •\._-+- Cerebellar nuclei

'.3t~-Cerebeoar cortex

Figure 22-6. Distribution of '1-aminobut)'ric acid (GAI3A)·containing neurons and their pwjl'ctions.GABA-ergic neurons ,lfC the m;ljor inhibitory cells of the central n('ryous sySt('m. GABA local circuit neurons;lfC found in the neocortex, hippocamp;11 fonmltion, ,mel cer{"helhlr coftex (Purkinje cells). Suimal GABA-ergicn('Uf(ms project to Ihe Ih;lbmus ;md suhlll;lhunic nuc1('us (nOt sho"'n).

2. Excitatory amino acid tmnsmittersa. Glutamate (Figure 22-7) is the major excitatory tmnsminer of the bmin.

Neocortical glutamatergic neurons project to the 5'fr;atum, .5Ubthal:ltllic nu­cleus, and thalamus.(1) Glutamate is the tr.ln5'mittcr of rhc cerebellar I,rranule cells.(2) Glutamate is also the transmitter of nonnocicepth·c, large, primaf)' af­

ferent fibers that enter the spinal cord and brain stem.(3) Glutamate is the transmincr of the corticobulbar and corticospinal

tracts.

Glutamate

Pyramidal neurons 01 neocortex

_, ./ Striatum

Corticoslriatal fibers --;/-----\)fl-J Fomix

---'

Septal nuclei

CorticoOOlbar and corticosPioaJ tr,...,;.......:::~~\

G-.,---\-- Pyramidal cell 01hlppocampallormation

Granule cells ofcerebellar cortex

! .--,<--Proprioceptive fibers in dorsal roots

Agure 22-7. DbrributiQIl of gluramatC'-i;:omaining Ill'Ul'OIlS :uld lheir projCCtlollS. GluramalC' is IhC' Ilktje,rexcilatory transm;tterof Iht· cemml llC'rvOUSS)'lllem. Oxtkal glulamatergic neurons projCCl1O Ih(' striatum. Hip­poclmp:11 :md ;>ubicu!:lr glut1umltcrgic n('urons project through t!\(' (ornlX 10 the S('pt"J.1 area anJ hnx)lh.. lamus.The gmnul(' cdls of the cerebellum :lre glut;tmarergic,

120 Chapter 22

b, Aspartate, a majorexciratory transmitter of the brain, is the transmitter of theclimbing fibers of the cerebellum. Neurons ofclimbing fibers arc found in theinferior olivary nucleus.

c, Beha,'ioral correlation. Glutamate, through its N-methyl-D-aspartate(NMDA) r«eptors, plays a role in long-term pmenti:uion (a memOf)'process) of hippocampal neurons. Glutam:ue plays a tole in kindling and sub­sequent seizure activity. Under certain conditions, glummat(' and its analogsarc neurotoxic.

d. Glutamate excitotoxicity. GLU is released in the striatum and hineL. to its re­ceptors on striatal neutons resulting in an action potential. GLU is removedfrom the extracellular space by astrocytcs. In Huntington's disca~ GLU isbound (0 the N-methyl-D-aspartatc (NMDA) receptor resulting in an influxof calcium ions and subsequent cell death. This cascade of evems wirh ncu·ronal death most likely occurs in cercbrovascular accidems (stroke).

3. Nitric oxide is a recently discovered gaseous neurotransmitter thm is producedwhen llitric oxide-synthase converts arginine to citrulline.a. It is locared in rhe olfacwry system, striatum, neocortex, hippoc:unpal forlll:l'

tion, supraoptic nucleus of rhe hypothal:llllus, and cerebellum.b. Nitric oxide is responsible for smooth muscle rebxation of the corpus cavcr­

nosum and thus penile erection. It is also believed to playa role in memoryformaTion becausc of its long-term potentiation in the hippocampal forma­tion. In addition, nirric oxide functions as a nitrovasodilator in the cardio­vascubr system.

II. FUNCTIONAL ANO CLINICAL CONSIDERATIONS

A. Parkinson's disease results from degenetation of the dop:.lminergic neurons that arefound in the pars comp'1Cm of the substantia nigra. It causes a reduction ofdopaminein the striatum and substantia nigra (.sec Chapter 21 III A).

B. Huntington's disease (chorea) results from a loss of acetylcholine- and GABA­containing neurons in the striatum (caudaloputamen). The effect is a loss ofGABAin the stri:lrulll and substantia nigra (.sec Chapter 21 III C).

C. AI:heimer's disease results from the degeneration ofcorrical neurons and cholinergicneurons in th(' basal nucleus of Meynert. It is associated with a 60% to 90% loss ofcholine acetylrr;msferasc in the cerebral cortex. Histologically, Alzheimer's dise;lse ischaracteri:('d by the presence of neurofibrillary tangles, senile (neuritic) plaques,:\myloid substance, gr.mulovacuolar degeneration, and Hirano bodies_

0, Myasthenia gravis results from aU[Qantibodies against the nicotinic acctylcholine re­cepror on skeletal muscle. These antibodies block the postganglionic acctylcholinebinding site. Thymic cells augment B-cell production of autoantibodies. Thc cardinalmanifestation is fntigable weakness of the skeletal muscle. The extraocular muscles,including the levator palpebrae, are usually involved. Edrophonium or nl"OStigmine in­je<:tion is used for diagnosis.

E. lambert-Email myasthenic syndrome is caust.'d by a presrnaptic clefL'Ct of acetylcholinerelease. It l"aU5C.-S weakness in the limb muscles. bur not in the bulb.1t muscles. Fifry per­cenr of cases arc associared with neoplasms (i.e., lung. breast, prostatd. In thL"SCp.1tienrs, muscle strength imprOl;cs with u~. (In myasthenia gravis, musch.' use rcsultsin muscle fini/,'11e.) Autonomic d)osfunction includes cll')' mouth, constipation. impo­tence. :md urinary incontinence.

23Cerebral Cortex

I. INTRODUCTION. The ccrcbrnl conex. the lhin. gray cO\wing of both hemispheres ofthe brnin, has twO rypes: the neocortex (90%) and the allocortex (10%). Motor cortex isthe thickest (4.5 mm): visual cortex is the rhinest (1.5 mill).

II. THE SIX-LAYERED NEOCORTEX. L.1)'CrS II and IV of the neocortex arc mainl)' af·ferent (j.e., receiving). L1.)'crs V and VI are mainly efferem (i.e" scnding).

A. Layer I is the molecular layer.

B. Layer II is the external granular layer.

C. Layer III is the external pyramidal layer. It gives rise [Q association and commissum!fibers and is the major source of carricQConical fibers.

D. Layer IV is the inlernal granular layer. It receives th:llamocortic:ll IibcN from thethalamic nuclei of the "cnrral tier (i.e.. \'cmral po5tcrohueral and \'cntral posterome­dial). In the visual correx (Brodmann's area 17), layer IV reeeh'cs input fl"Ofll the lat­eral geniculme body.

E, Layer V is the internal pyramidal layer. It gh'cs rise 10 corricobulbm, corricospin:ll.and corricostriaral fiben:. II conlains Ihe giam pyramidal cells of Bet:. which are foundonly in the mOlor conex {Brodmann's area 4}.

F, Layer VI is the muhifonn layer. It is the major source of corticOlhalamic fibers. Itgi\'cs rise (0 projection, commissural, and association fiben:.

III. FUNCTIONAL AREAS (Figure 23-1)

A. Frontal lobe

1. The motor corlex (Brodm:mn's area 4) and premOlor cortex (BroJmann's area 6)are somatotopically organitecl (Figure 23·2). Destruction of these areas of thefrontal lobe causes contralateral spastic paresis. Contralmeral promllor drift is as­sociated with frontal lobe lesions of the corticospinal tracl.

2. Frontal eye field (Brodmann's area 8). Destruction causes deviation of thc eycs 10

the ipsilatcral side.

3, Broca's speech area (Brodmann's areas 44 and 45) is located in the posterior partof Ihe inferior fronml gyrus in the dominam hemisphere (Fibrurc 23-3). Destruc­tion resuhs in elCpressi\·e, nonfluem aphasia (Broca's aphasia). The patient under­srands both wrincn and spoken language, but cannot aniculme speech or wrilenonnally. Broca's aphasia is usually associated with contralateral mcial and armweakness because of the itwol\'e1l1Cnl of the motor strip.

4, Prefrontill corlex (Brodmann's nreas 9-12 and 46-47). DcstTucrion of Ihe amI.'-

.1.22 Chapter 23

•

-Primary visual cortex (17)

_ -JVisual association1 cortex (39, 19, 18)

\Auditory associalion cortex (Wernicke's

speech area of lett hemisphere) (22)

46

8

,,9

PrimaIy motor cortex (4)\ ,Primary somatosensory cortex (3, 1, 2)

~....,~':I--:r.~'-~ ...Vestibular cortex (2),-~Somatosensory associalion

cortex (5, 7, 40)

Frontal eye field (8) \

Prefrontal cortex

(9,10, 11, 12)~ ... ..t!:-... r10 45

Broca's speech area oflett hemisphere (44, 45) I

Secondary somatosensory ...and gustatory cortex ,

Primary auditory cortex (41, 42)'

B

Premotor cortex (6) \

Primal)' motor cortex (4h,__-r'T--......,I./ Primal)' somatosertSOfY cortex (3, " 2)

~ Visual associationcortex (19, 18)

-limbic: lobe

,Somatosensory association, cortex (5, 7)

46,

8r ......-",,\\ate COrtexc;~ 24

9

.r

,f)-Limbic lobe .... 9"~'---'-2~ '~::';;'Y:::--<'-:;;~~':9 ,'-...:.'!-',...,..r~~ ",,:,'",

Septal area"""" 38 \' 37-,19"

~,t:i::2iu,~5'~,~'"''-'~~;;>..I,Primary visual cortex (17)

Limbic lobe I I \ \ Uncus (28), ,, ,Primary olfactory cortex (34) 'Parahippocampal gyrus

Prefrontal cortex(9,10,11,12)-..-..

Figure 23-1_ Some mow.. and sensory areas of the cerebral cortex. CA) Lateral co,wex surface of the hemi­sphere. (8) MeJial surface of ,he hemisphere. The numbel'5 rcter to ,he Brodmann brain map (Brodmann's areas).

Cerebral Cortex 1.23

B Motor homl,lnCl,lll,lS

Figure 23-2. The :>CI\5OI)' and mOlor homunculi. (A) Scn5Or)' reprcscnmlion in the pom:cnual gyrus. (B)MOlor reprcscnr:ltion in lhe pr\.'Cemml gyrus. (Reprimed wilh permission from Penfield W, RasmUS$(':n T: T~u'Tebrul Corle.1; of Mall. New York, H:lfncr, 1968, pp. 44, 57.)

rior two-thirds of the frontallobc convexity results in deficits in concentr:ltion,orientation, abstrncting ability, judgment, :md problem-solving ability. Otherfronwl lobe deficits include loss of initiative, inappropriate behavior, release ofsucking and grasping reflexes, &oait apraxia, and sphincteric incontinence. De­suuction of the orbital (frontal) lobe results in inappropriate social behavior (e.g.,usc of obscene language, urinating in public). Perseveration is associated withfronrallobe lesions.

B. Parietal lobe

1. The sensory cortex (Brodmann's areas 3, I, and 2) is somaroropically organized(see Figure 23-1). Destruction results in contralateral hemihypcs[hesia and aster­eognosis.

2. The superior pilfietallobule (Brodmann's areas 5 and 7). Desuuction results ineontmlrllcral flstereognosis and sensory neglecL

3. The inferior parietal lobule of the dominant hemisphere. Damage results inGerstmrmn's syndrome, which includes the following deflcits:a. Right and left confusionb. Finger a\;nosiac. Dysgraphia and dyslexiad. Dyscalculiae. Contralateral hemianopia or lower quadrantanopia

4. TIle inferior parietal lobule of the nondominant hemisphere. Destruction resultsin the following deficits:a. Topographic memory Joss

124 Chapter 23

_----I~r-~...LArcua'e(superior longitudinal) fasciculus(cooctuction ",nh"",,,)Motor cortex vocatization (6, 4) "t"' ........

~9Yrus(39)

Broca's speech area (44, 45)(Broca's aphasla)

VISUal associationcortex (18, 19)

Primary visual cortex (17)

s._-=:::~------.k.-"<\wernicke'sspeech area (22)(Wernicke's aphasia)

Figure 23-3. Corti"ll af\'as of Ihe dominant hemisphere that play an important role in l:mguage production.The visual image of a word is projccu:d from the visU:ll Cortcx (Broom:mn's area 17) 10 the visual associ:Jfionconices (Broom,mns areas 18 and 19) and then to the angular gyrus (Broomann's area 39). Further procwingoccurs in Wemickc's spo..-ech ,lrell (Brodm:ll\n's area 22), where Ihe auditory form of Ihe word is recalled. Throughthe arcuate fasciculus, this inform:llion reaches Broca's speech area (Brodmann's areas 44 and 45), ..,here motor)pecch programs control the \'ocali:ation mechanisnlS of the precentral gyrus. Lesions of Broca's spcc<:h area.Wcmicke's speech are:l, or the :lrcuale fasciculus ~It in dysphasia.

b. Anosognosiac. Construction apraxia (Figure 23·4)d. Dressing apra.xiae. Contralateral sensory neglectf. Contralateral hemianopia or lower quadrantanopia

C. Temporal lobe

A

I~:>..t( s~

•1012. II +-

B c

Agure 23-4. Testin~ for constRIction apraxia. (A) Thc patielll was asked to copy the f:ICe of a dock. (8)Th<:- p;!l'lelll was asked to hisect a hori:onralline. (C) The patient w:u asked to copy a cross. 11ldC drawings)how cOlllralaleral nq:k"Cl. TIle rcsponsihle lesion is found in the l\OI"loiominant (right) parietal lobe. A lefthemi:lll<'Pla. by itself, does not rt"SUh in conrralatetal neglect.

Cerebral Cortex 125

•

c

( (

9O"11aIa18ra1 Sj)&Slic paresis In leg area

"

•Contralalerallowefquadranlanopia

Figure 23-5. Focal dcslnlcrivc hemispheric lesions and the resulting symptoms. (A) Lmeral convcx surfaceof the dominant left hemisphere. (B) Larcml convex surf..KC of the nondorninant right hemisphere. (C) Medialsurface of the Ilondomimlnt hcmispherc.

126 Chapter 23........................................................................................................................................................._ .

Field at vision

l R

..~~.:.......OlfKtk.n-......

l,,,,,,Writini

Simple language

comprehension ../

l ~ eM

Rvisual

'-'--fieldMajor I'lemisphere Minor I'lemisphen!

Tnnsected corpus callosum

Figure 23-6. Funclions of the split bnlin a(ter [nmsc<:tion of th!! corpus calloswn. TaClile and visual perc!!P­tion is projcclN! to the conrr:l!::tter:ll hemisphere. olfaction is perceived on the same sid!!. and audition is per­ceil'ed predomin:llltlr in the opposite hemisphere. The left (l) hemisphere is dominant for language. The right(R) hemisphere is dominant for spatial construction and nonverbal idemion. (Reprinted with pcnnission fromNob"ck CR. Dcm;lrcst RJ: The HUllum Nen'Qus System. Malvern, PA. Lea & Fcbiger, 1991, p. 416.)

1. The primary audimry cortex (Brodmann's areas 41 and 42). Unilateral destruc­tion resuhs in slight loss of hearing, Bilateral loss results in COrlical deafness.

2. Wernicke's speech area in rhe dominant hemisphere is found in rhe posterior panof the superior temporal gyrus (Brodmann's area 22). Destruction results in recep­ti\"(', fluent aphasia (Wernicke's aphasia), in which the patient cannot understandany form of language. Spee<h is spontaneous, fluent, and rapid, bur makes littlesense.

3. Meyer's loop (see Chapter 17 11 F 2) consists of the visual radiations that projectto the inferior bank of the calcarine sulcus. Interruption causes conrralatemlup­per quadrant anopia ("pie in the sky").

Cerebral Cortex 1.27

4. Olfactory bulb, tract, and primary cortex (Brodmann's arca 34). Dcstmetion re­sults in ipsilateral anosmia. An irritative lesion (psychomotor epilepsy) of the un­cus results in olfactory and gustatory hallucinations.a. Olfactory groove meningiomas compress the ollnctory tl<lCt and bulb result­

ing in anosmia. See Foster Kennedy syndrome Chapter 13 I C.b. Esthesioneuroblastomas (olfactory neuroblastOmas) arise from bilx>lar sen­

sory cells of the olfactory mucosa; they can extend through the cribrifonn plateimo the amerior cranial fossa. Preseming symptOms arc similar to FosterKennedy syndrome.

5. Hippocampal cortex (arehicortex). Bilaterallcsions result in thc inability to eon­solidme short-term memory imo long-tern) memory. Earlier memories are retrievable.

6. The anterior temporal lobe, including the amygdaloid nucleus. Bilateral damageresults in Kluver-Buey syndrome, which consists of psychic blindness (visual ag­nosia), hyperphagia, dociliry, and hypersexuality.

7. Inferomedial occipitotemporal cortex. Bilaternllesions result in the inability torecognize once-familiar faces (prosopagnosia).

D. Occipital lobe. Bilateral lesions cause cortical blindness. Unilateral lesions cause con­tmlmernl hemianopia or quadramanopia.

IV. FOCAL OESTRUCTIVE HEMISPHERIC LESIONS ANO SYMPTOMS. Figu~ 23·SA shows the symptoms of lesions in the dominam hemisphere. Figure ZJ-5B shows thesymptoms of lesions in the nondominant hemisphere.

V. CEREBRAL DOMINANCE is determined by the Wada test. Sodium mnoharbital(Amyml) is injected into the carotid anery. If the patient becomes aphasic, the anestheticwas administeu.-d to the dominant hemisphere.

A. The dominant hemisphere is usually the left hemisphere. It is responsible for propo­sitionallanguage (grammar, symax, and semantics), SlXcch, and calculation.

B. The nondominant hemisphere is usually the right hemisphere. It is responsible forthrec-dimensional, or spatial, perception and nonverbal ideation. II also allows supe­rior recognition of faces.

Agure 23-7. Chimeric (hybrid) figure of a faceused to examine the hemispheric funC[ion of com­missurotomized patients. The patiem is instructed tofixate on the dot and is asked to describe whar he sees.If he says that he sees the face ofa man, chen the lefthemisphere predominates in vocal tasks. Ifhe is askedto point to the face and he points to the woman, thenthe right hemisphere predominates in poiming tasks. /

128 Chapter 23

VI. SPLlT·BRAIN SYNDROME (Figure 2}·6) is a discoooeClion syndrome th:u resultsfrom tr:msL'<:tion of the corpus callosum.

A. The dominant hemisphere is bener at "ocal naming.

B. The nondominant. mute hemisphere is benerat pointing (Q a stimulus. A person can­nOI name objects thm are presemed to the nondominam visual COrtex. A blindfoldedperson cannot name objects that are presemed to the nondomin:m[ sensory cortexduough touch.

C. Tesl (Figure 23-7). A subject ,·iews a composite picture of tWO half-faces (i.e., achimeric, or hybrid. fib'llre). The right side shows a man: the left side shows a .....oman.TlH' picture is removed. and the subject is asked to describe what he 53W. He may re­slxmd that he saw a man. bm when asked to point to what he saw, he points to thewoman,

D. In a p,'uiem who has alexia in the left visual field. the \'erool symbols seen in the rightvisual cortex ha\'e no access to the language cemers of the left hemisphere.

VII. OTHER LESIONS OF THE CORPUS CALLOSUM

A. Anterior corpus callosum lesion may result in akinetic mutism or tactile anomia.

B. Posterior corpus callosum (splenium) lesion may result in alexia without agraphia.

C. Callosotomy has been successfully used to treat Mdrop attacks" (colloid cyst of third,'entriclc).

VIII. BRAIN AND SPINAL CORD TUMORS (.e< Ch,p,,, 5)

24Apraxia, Aphasia, and Dysprosody

I. APRAXIA is the inability to perform mowr activities in the presence ofinrxt motor andsensory systems and noml"l comprehension.

A. Ideomotor apraxia is rhe inability, in response (0 [1 vernal command. (0 perform mo­Wf ac(i\'i[~' that can be pcrfomloo with ease sponr:alloously (e.g., slicking our thetollbruC). This condition is associated with a lesion in the dominant hemisphere.

B. Ideational apraxia is the inability to penonn a multistep activity Of demonsume theuse of a real objt.'Cl (e.g.. (001). This condition is associated with a lesion in rhe dom­inant hemisphere.

C. Construction apraxia is the inability w clrnw or consrrucr a geometric figure (e.g., the(ace of a clock), If the patient draws only the right half of the clock. this condition iscalled hemincglecr. and the lesion is loc:ned in the riglu inferior parietal lobule (seeFigure 23-4).

D. Gait apr.l.xia is the innbility to use the lower limbs properly. The patient has difficultyin li(ting his (eet (rom the floor, a frontal lobe sign seen with normal pressure hydro­cephalus (gait apraxia, dementia, incontinance).

II. APHASIA is impaired or absent comlllunic~Hion by speech, writing, or signs (i.e., losso( the capacity (or spoken language). The lesions arc located in the dominant hemi­sphere. Associate the (allowing symptoms and lesion sites with the :lppropriate aphasia(Figure 24·1).

A. Broca's (motor) aphasia

1. Lesion in frontal lobe, in the inferior frontal gyrlls (Brodmann 44, 45)

2. Good comprehension

3. Hfortful speech

4. Dys~Hthricspeech

5. Telegraphic speech

6. Nonfluent spe<.><:I\'

7. Poor repetition

8. Contralnterallower f3cial and upper limb weakness

B. Wernicke's (sensory) aphasia

1. Lesion in posterior temporal lobe, in the superior temporal gyrus (Brodmann 12)

2. Poor comprehension

129

130 Chapter 24

Fluent,-Nonnuent,-

Goodcomprehension

Conductionaphasia

Broca'saphasia

Transcorticalmol'"

aphasia

Poo'comprehension

Wemicke'saphasia

Transcorticalsensoryaphasia

Mixedtranscortical

aphasia

Figure 24-1. TIle Mllphllsia sqUllreMmakes it easy [0 differentiate the six most common Mnational board":tphasias. Broc~I'S, concluclion, :tnd Wernicke's llphasias are all ch:uoctcrized by poor repetition, (Adapted w(thpcmlission (rom Miller j, Foumain N: Neur%gJ Recall, B."llrimorc, Willi:tnu & Wilkins, 1997, p. 35.)

3. Flucnr speech

4. Poor repetition

5. Quadrantanopia

6. Paraphasic errorsa. Non sequiturs (L. docs not follow) are statements irrelevant to the quesrion

asked.b. Neologisms MC words with no meaning.c. Driveling speech

C. Conduction aphasia

1. Transection of the arcuate fasciculus; the arcuate fasciculus inrerconnects Broo-m,l1ln's speech area with Wernicke's speech area.

2. Poor repetition

3. Good comprehension

4. Fluent speech

D. Transcortical motor aphasia

1. Poor comprehension

2. Good repetition

Apraxia, Aphasia. and Dysprosody 131

3. Nonfluent speech

E. Transcortical mixed aphasia

1. Poor comprehension

2. GoOO repetition

3. NonAuent speech

F. Transcortical sensory aphasia

1. Poor comprehension

2. Good repetition

3. Fluent speech

G. Global aphasia n."sults from a lesion of the pcrisylvi:m area, which conrains Br0c3's:andWernicke's :arcas. Global :aphasia combines :all of the symplOffiS of Broca's and Wer­nicke's aphasias.

H. Thalamic aphasia is a dominant th:alamic syndrome. It closely rt.'SCmbles a thoughtdisordcr of patients with schi:ophrenia and chronic drug-induced psychosis. Symp­roms includc fluent paraphasic speech with nonnal comprehcnsion:and repetition.

I. Basal ganglia. Diseases of the basal ganglia may cause :aphasia. lesions of the anteriorbasal ganglia result in nonfluent aphasia. Lesions of the JXlStcrior basal g:mgli3 rC$Ultin nuent aphasia.

J. Watcrshed infarcts are areas of infarction in the b:>und:lry mnes of the anterior, mid­dle. and postcrior cerebral artcries. These areas arc vulnerable ro hypoperfusion :andthus may sep.1ratC Broca's and Wernickc's speech arcas from the surrounding corrcx.TIlese infarcts cause the motor, mixed, and sensory transcorrical:aphasias.

III. DYSPROSODY is a nondominant hemispheric language deficit that serves propositionallanb'Uab7C. Emotionality, inflection, melody, emphasis, :lOd gesturing are affccted.

A. Exprcssivc dysprosody results from a lesion that corresponds to Broca's arca, but is 10­catcJ in the nondominam hemisphere. Patients cannOt express emotion or inflectionin their speech.

B. Reccptivc dysprosody results from a lesion that corresponds to Wernickc's area, but islocnted in the nondominant hemisphere. P3tients cannot comprehend the emotion­ality or inflection in the speech they hear.

Appendix: Table of Cranial NervesCranial Nerve T,pe Origin Function Course

I--Olfaetory SVA Bipolar olfactory Smell (olfaction) Central axonsneurons (in project to theolfactory epithe- olfactory bulb vialium in roof of the cribriform platenasal cavity) of the ethmoid bone.

ll-optic SSA Retinal ganglion cells Vision Central axons con-verge at the opticdisk and form theoptic nerve, whichenters the skull viathe optic canal. Opticnerve axons terminatein the lateralgeniculate bodies.

lIl-ocutomotorParasympathetic GVE Edinger-Westphal Sphincter muscle Axoos eltit the

nucleus (rostral of iris; ciliary midbrain in themidbrain) muscle interpeduncular

Motor GS, Oculomotor nucleus Superior, inferior, fossa, traverse the

(rostral midbrain) and medial recti cavernous sinus,and enter the orbit

muscles; inferiorvia the superior

oblique muscle;levator palpebrae orbital fissure.

muscle

IV-Trochlear GS, Trochlear nucleus Superior oblique Axons decussate in(caudal midbrain) muscle superior medullary

velum, exit dorsallyinferior to theinferior colliculi,encircle the mid-brain, traverse thecavernous sinus,and enter the orbitvia the superiororbital fissure.

V-TrigeminalMotor SVE Motor nucleus CN V Muscles of masti- Ophthalmic nerve

(mid pons) cation and tensor exits via thetympani muscle superior orbital

Sensory GSA Trigeminal ganglion Tactile, pain, andfissure; maxillary

and mesencephalic thermal sensation nerve exits via the

nucleus CN V from the face; the foramen rotundum;

(rostral pons and oral and nasal mandibular nerveexits via the fora-midbrain) cavities; and themen ovale; ophthal·supratentorial duramlc and maxillarynerves traverse thecavemous sinus;GSA fibers enter thespinal trigeminaltract of CN V.

VI-Abclucent GS, Abducent nucleus lateral rectus Axons eltit the pons(caudal pons) muscle from the inferiOr pon-

tine sulcus, traversethe cavernous sinus,and enter the orbitvia the superiororbital fissure.

(appendix cont.)

133

134 Appendix

Cranial Nerve

VII-FacialParasympathetic

Motor

sensory

Sensory

VIII-Vestibull»cochlearVestibular nerve

Cochlear nerve

IX-GlosSI»pharyngealParasympathetic

Motor

Sensory

sensory

sensory

Type

Gil!

SVE

GSA

SVA

SSA

GVE

SVE

GSA

GVA

SVA

Origin

Superior salivatorynucleus (caudal000"

Facial nucleus(caudal pons)

Geniculate ganglion(temporal bone)

Geniculate ganglion

Vestibular ganglion(intemal auditorymeatus)

Spiral ganglion(modiolus oftemporal bone)

Inferior salivatorynucleus (rostralmedulla)

Nucleus ambiguus(rostral medulla)

Superior ganglionUugular foramen)

Inferior (petrosal)ganglion (in jugularforamen)

Inferior (petIosal)ganglion (in jugularforamen)

Function

Lacrimal gland(via spheno­palatine ganglion);submandibularand sublingualglands (via suo.mandibularganglion)

Muscles of facialeltpression;stapedius muscle

Tactile sensation toskin of ear

Taste sensationfrom the anteriortwo-thirds of tongue(via chorda tympani)

Equilibrium(innervates haircells of semi­circular ducts,saccule, andutricle)

Hearing (innervateshair cells of theorgan of Corti)

Parotid gland (viathe otic ganglion)

Stylopharyngeusmuscle

Tactile sensationto eltternal ear

Tactile sensationto posterior thirdof tongue, pharynx,middle ear, andauditory tube; inputfrom carotid sinusand carotid body

Taste 'rom posteriorthird of the tongue

Course

A.xons exit the ponsin the cerebellarpontine angle andenter the internalauditory meatus;motor fiberslJaverse the facialcanal of thetemporal bone andeltit via the stylo­mastoid foramen;taste fibers tr&verse the chordatympani and lingualnerve; GSA fibersenter the spinaltrigeminal tract ofCN V; SVA fibersenter the solitarytract.

Vestibular andcochlear nerves joinin the internal audi­tory meatus andenter the brain stemin the cerebellopon­tine angle; vestibularnerve projects to thevestibular nuclei andthe nOCC\llooodularlobe of the cerebel­lum; COChlear nerveprojects to the coch­lear nuclei

A.xons eltit (motor)and enter (sensory)medulla from thepostolivary sulcus:altons eltit andenter the skuli viajugular foramen;GSA fibers enterthe spinal trigeminaltract of CN V; GVAand SVA fibers enterthe solitary tract.

(appendix cont.)

Appendix 135............................................................................................................ ............................................................................................

Cranial Nerve T,pe Origin Function C......

X-Vagal Axoos exit (motor)Parasympathetic GV, Dorsal nucleus of Viscera of the and enter (sensory)

CN X (medulla) thoracic and medulla from theabdominal CaY- postolivary sulcus;ities to the left alIOOS exit andcolic flexure enter the skull via(via terminal the jugular fora-(mural) ganglia) men: GSA fibers

enter the spinalMOlOr SV, Nucleus ambiguus Muscles of the trigeminal Ifact

(mid·medulla) larynx and of CN V; GVA andpharynx SVA fibers enter

Sensory GSA Superior ganglion TactHe sensation the solitary tract.

(jugular foramen) to the external ear

Sensory GVA Inferior (nodose) Mucous membranesganglion (in of the pharynx,Jugular foramen) larynx, esophagus.

trachea. andthoracic andabdominal viscerato the left colicnexure

Sensory SVA Inferior (nodose) Taste from theganglion (in epiglottisjugular foramen)

XI-Accessory SVE Axons from the cranialMotor (cranial) Nucleus ambiguus Intrinsic muscles division exit the

(medulla) of the larynx medulla from the(except the cOCo- postolivary sulcusthyroid muscle) and join the vagalvia recurrent nerve: axons fromlaryngeal nerve spinal division exit

Motor (spinal) Ventral hom Sternocleidomastoid the spinal cord.

neurons Cl-e6 and trapezius ascend through the

muscles foramen magnum,and exit the skUllyia the jugularforamen.

XII-Hypoglossal GS, Hypoglossal nucleus Intrinsic and extrinsic Axons exit from the(medulla) muscles of the preolivary sulcus

tongue (except the of the medullapalatoglossus and exit themuscle) skull via the hypo.

glossal canal.

SVA - special visceral afferent: SSA - special somatic afferent: GVE - general visceral efferent; GSE • general s0­

matic efferent: SVE '" special visceral efferent: GSA '" general somatic afferent: GVA .., general visceral afferent: CN- cranial nerve. •

Index

lullic P:l~'C numbers dcsign:l.lc figures: p:J~,'e numbers followed by ~t~ desii,'l1..11C mblcs; (stt also) refers to relatedIOpies Of more detailed IOpic brCllkdowllS. Topics h3\'iog more than one subcntl1' 3rc listed under lhe noun le.g..Body (bodies): c:;Il"(l(idl.

AbJocenl ncrve (CN VI) (see llnder Cranial nerves)Accessc>r)' ncr"... (CN XI) (see 1I!1deT Cranial nen'es)Accommod.1tion. ocular, 66-67Acetylcholine. 98. 113, 115Acoustic neuroma ($Chwannoma), 33. 34, 60,

81--82Al,'flO5ia

lin~,'cr. I ZJ\,jsual (d)'slc:da), 125

Alar (sensory) pl:ue, 14. 24, 25AI:hcimer's disease. 32, 115. J15. 118,-Aminobulyric acid (GABA), 85, 89, 113, 114,

117.118,1/9Amyorrophic l:ncral sclerosis (ALS. Lou Gehrig's

disease),46Ancnc('ph:II)' (mcro;lllcnccphaly). 26, 27Aneurysm, 67. 74Angiogmphy

C:lrorid, 18, 19, la, 11ccrcbml blood supply, 18-19, 10, 21, 22digiml subtraction, 19.1J-lZ\·cnebral. /9. 21

Anosmi:l,66, 125Anosognosia.l24Aph:l~i:l. I29-IJ 1, 130

bus:!1 ganglionic, IJ IBroca'~, 121. 125, 129conduction, 125. 130gloh,d. lJ IIhalamic,131transcortical mb:ed. 130Imnscortiealmotor, 130-131t r;lllscortiC:l1 sensory, I JIWernicke's, 125. 125, 129

Apmxin,129conmuction, 124, 124. 129dressing, 124ideation;ll, 129idcomotor. 129

Aqucducml stenosis, 28, 29Amchnoid gmnu[;lfion. 9Argyll.RobertSOn pupil. 95. 96Arnold·Cfli;lri m:Mormation. 28. 29Astereognosis. 125

Astrocytes, 31-32Astrocytoma, 3-4, 87

cerebdlar,34Ataxia, Fricdrekh's, 48AudilOl)' system, 58--60

auditOl)' path\\';l~', 58.59hearing defects. 58-59

Autonomic nen'GUS Syslem, 98-102, 99, 100.101 t (su also Hypor.h.... lamus; Limbicsystem)

Axonal transport. 3\

Basal "..anglia, 111-112. 131Bas:ll (mQ(or) plate. 14. 25Bet: pyramid..-II cells, 42Blood·brain b.1rrier, 32Blood·CSF barrier, 32Blood supply, 15-23 (see also Anciography and

sptcijic 'ascis)of internal capsule, 18,90.90intemalcarolidsystem,15,16,16-17middle meninl,tCal :Irlery, 19, n, Z3spinal cord :tnd lower brain stem. 15. 15thalamic, 90veins. 18venous dural sinuses, 18vertebrohasibr system, 15, 17-18

Body (bodies) (scc also Nucleus InucleiDcarotid, nCowdry type A inclusion. 32geniculate

Inteml, 49, 89, 89, 90, 91 , 93 (sec also Cranialnerves; II (optic) 91)

medi:ll, 49, 89,89,90Himno,32juxtarestifoml, 61,62Lewy, 32, 113rruunill:Jry, 1,2,6,7,50,103,105,109mcdiall,'Cniculare, 52,58,59,81Negri,32pineal. I, 49tmpc:oid, 51 , 58,59

Botulism, 102Brain lUmors, 28,33-34,82,84,87

137

138 Index

Br.lin 11imors--COl1linll~J

llCOUSlic nO::lIrom:t (schw;mnoma), 3J.--.-34, 81--82aSUOq'lOma, 34, 87"blillerl1)' gliOlml" (see Glioblastollla)bmin abscess. 34choroid plexus J)<lpillomas, 33colloid cyst oflhird n'lluide, 33cmniorharyngiomas, 28,34ependymoma, J3-J4, 871.'Cnninoma of pineal region, 34, SOgliobl:tslom:l muhifonllC. 33, 34gliom:l. romine. oplk. 7.34heln:lllgiobl:btoma.34llwdul1obbSlOma,3J-J4meningioma, 33-34oli1.'Olk·ndrq;liOfn:I. J4pilUit~lrY ;!dcrlOlll;l. J4pcobclinom;l, J4

Broca's aphasia, Ill, 1Z9Brodrmmn·san.-as.lll

C:.IUda equina, 37C:.1\"emol.lssinus.57Centr.ll pollline 1ll)·e1inolysis. 1MCerebellum. connt"Clions, 85-86

s)·ndromc:s. 87lUmors.87

Ccrebr:ll cono::x fllllclion. 121-1 Zifront;11 k>he. Ill-I ZJlimhk. 107-1101l:lrielllllobc.I23-I24rO::lI1poT:lllohe. 124ocdl'il:lliobc. 1Z7Spill-hmin sydrornc. 127-128

Cerebrospinal tluid (CSF). II, Ill, 32OlUTea

gr:l\'id;\fUIll, 114Huntington's, 113, 114,117.118Sydenh:lm's (Sc Vitus' dance), 114

Choroid pb:us, 34Omc:\:

allocoftcl(, 121archicortcl(, 127cntnrhinnl. 109no::ocortex, 121piriform, 66

Corti. orglln of, 58, 59Cr:1I1inlnerves, 65, 133-lJ5

llhdllCerlt (VI), 65, 67, 68-69,133Hccessory (XI), 65, 68, 69, 135HCOl.lSlic (VllI), 58-60, 65.134cochlear (VllI), 58, 60, 65.134fad;!1 (VIl), 65. 69-71, 133glossophnryn1.'\':11 (IX), M, 72-74. 133hypogloS$al (XII), 65. 76-77, iJ5illl'cnnedilllO:: (VII), 65, 69, 70oculomOlOf (Ill), 65, 66. 67. 133otf."lClOry (1).65.66. 1J3

oplic (II), 65--66. 91, 97, 13Jspinal accessory (XI). 65, 75, 135Trigeminal (V), 53, 55-57, 67. 68, 133uochlear (IV). 65, 67, 133\'agal (X), 65, 7+-75, 135\'estiblilar (VIII), 61. 6+-65, 71.72, IHveslibulocochle3r (VIlI), 58, 6+-65, 71, 131

Craniopharyngoma, 27, 28. 31Crest. neural, 14. 25-26CriSia amplilbris, 6/

Dandy-W3lker malformation. 19, 19Deafness. 80

conduction. 58nerve (sensorineural, perceptive). 59. 68

Diabetes insipidus. 101, 106Dura mater, 8, 9.21.13Du~1 helIlOTThage. 11O)'norphins. 117Dyscalculia, 113Dysdiadochokinesia, 87Dysequilibrium.87Dysgraphia, 113Dyskinesia, tardh'e, 114Dyslexia, 113, /25Dysmenia.87Dysphasi3.88O)'Sprosodia (dysprasody), /15, 13 IDysrhythmokinesia,87Dyssynergia, 87DySiaxia, BO, 87

Endorphins, 117Ependymoma, 33. 87Eye fields

fromal, 9+-95, IIIoccipital, 95

Facial nerve (CN VII) (see 14nder Cmnial nerves)Fewl alcohol syndrome, 29Filum termin~llc, 9Finger agnosill, 123Foster Kennedy syndrome, 66, 109Fricdfcich's atal(ia, 18

Gait apraxia (dystaxia), 80'Y-aminobUlyric acid (GABA), 85, 89.113,114,

!17, 118, 1/9Genninoma, 34, 80GI:lnd(s)

pineal, 1,2,5pituitary (hypophysis), 1. 3,27,17,18,57

GlioblaslOma mliltiforme, 33. 34Glomus. calcified, /4Glossopharyngeal nerve (CN IX) (seo: under CT3niat

nerves)Glummate. 119, / /9.120Glycine. 118

Head tilting, 67Hearing defeclS, 5&-59Hematoma

epidur.:il,8, 13, 14,12subduml,8, 13, 23

Hemianesthesia, 67. 73-74, 80Hcmianhydl"(l5is, 97Hemianopia

altitudinal,91bilemporal, 91,106with macul:lr sparing, 18,91

HemilxJl1ism, 113, 1IiHemihypesthc,;kl, J25Hemiparesis (hemiplegia), 125

altem.uing abducem, 68ipsilaterial,97spastic, 82

Hepatolcllticular degeneratioll (Wilson's disc'ISC),113,114

Hernilnioncerebml,II-14hippocamp."ll gyrus, 12illlerverlebral disk, 18subfa1cial,12tonsillar (uansfomminal),12u"dnstemorial (uncal), J2, 66,97

Hippocampalform:uion, 107, 108, 109, 115, /Ji,JIB

Hippoc;unpus (cornu Ammonis), 4,6, 107Sommer'S5e(:torof,l09

Hirschsprung'sdisease (mqrdCOlon), 101Holoprosencephaly, 29Hydr.lllencephaly, 29Hydrocephalus, 10, 29Hypcracusis.71HYpe5lhc,;ia, 125Hyperphagia, 109, 127Hyperreflexia, 56Hyperscxu;llity, 109, 127HYPOf;lossal nerve (eN XII) (sec llIW'I" emnial

nerves)Hypophysis (pituitary gland), 3, Z7. 27, 2B, 104

anterior lobe, 104lXlsterior lobe, 104

HY1Xlpituilarism, 106Hypothalamus, 43, 93, 98, /03, 10]-106, /04, log,

IIi, 1/8H~'IXllOnia, in cerebellar disease, 87

Internal capsule, 90anterior limb of, 90~:cnu of, 90poslerior limb of , 90

JUj,'\llar fommen syndrome, 82-8]

Kayscr-Acischer ring, 114Kernicterus (nuclear jaundice), 1/3

lnoe~ 139

Kemoh."ln's nOlch, /2, 97

L"Imina lermin."llis, 1Lentiform nucleus, 112Limbic SYSlem, 107-110, 100, 109Lipofuscin l,'T'dnulcs, 32LMN (lower mOlor neuron) lesions. i5, 45-46,,.Locus cemleus, 116, 1/7

Medial forcbr.:lin bmin bundle, 105Megacolon (Hirsch.>prung'sJiscasc), 101Meninl,'CS,8-IOMeningitis, 8-10

Ir.lCteri'll, 9-10viml, 10

Mcnin",'ornyclocdc,28MClhylphcnyltcrtahydropyridinc (MPTP) induco..'d

patkinsonism, 113Meyer's loop, 9/, 92,125Microgli,l (HOrleg,1 cells), 26, 32Multiplc sclerosis, 48, 80Myastheni:1 gm\'is, 120Myelin;ltion, 26Myotactic reflex, 37

NI.."Ul1Il CfCSt, 24, 25-26Neurop;lthy

vilamin 81. 105, 110, 110vilamin BI !. 47

Nroroporeanlerior, 26poslerior, 26, 26

NeUfOlr.:lllsminers, 115--120 (see also specific sub-_fi)

acetylcholinc.115'lSp."lrr,Lle, 120OOp;lmine, 116Jynorphins, 117endorphins, 117enkcphalins, 117GABA,118glutam:llc, 119glycine, 118nitricoxidc (NO), 101, 120norepincphrine, 117scrownin, 117sotll,ltos(;ltin, liBsltbilanceP,117,118\'asoacli\'c intestin;il polypt:plKle (VIP), 101

Nis.;;l substance, 31Nucleus (nuclei)

abducem,ofCNVI,51,79:tmbil,'\lus, 50, 51, 73. is, i8, 79amY1,'<1aloidcus, J. 6, lOS, 108, 127arCIt."lle (infundibular), 103, 105arcuale (ruber:tl) hypothalamic. 104, 1/6basal of Mc)'ncrl, 115, 115

140 Index

Nucleus (nucicil--COll!imdcaudate, 3. 'I, 5. Ii. 41, 55. 90. Ill. "I, 116cr.mial nen;e nuclC'i

ofCN IIIEdinger-Westphal. 94n'lOl:or. 52.66

ofCN IV, 50ofCN V, 51. 54

chief sensor)'. 54mesencephalic. 55-56mowr.54spill"!. 55

dCN VI, 5\ofeN V[I, 51. 68-70ofCN VIII

cochlc"r, 59veslibular, 50-51, 61--62

of eN IX;\mbiguus.75

ofCN Xambigulls. 50. 73

ofCN XIambiguus. 75spinal accessor)'. 75

ofCN XIIhypoglass.'ll. 76. 78

cuneatc, of medulla. 39denmte. 86. 89globuspaltidus.III-112gracile. of medulla. 39of inferior colliculus, IhYPolhalamic. 1/6Icmifonn. IIImamilla!"'i.6. lOS (SCt aUo Body: lnamilJary)niger. IIIoli\'ary

inferior, 50, 61superior. 58. 59

paran'mricubr of hypOlh"ltunus. 104phrenic, 37preoptic, 103prctccral of midbrain. 94putalllcn, IIIraphe, 116, 117red, 6, 51, 8/, 86,rubel', 6. 52, 81, 86scptal. 109, 116-118so!itarius (of SQlimr)' [racl),sublhal;unic. 4, Ii. 113. 113suprachiasmiatic.103supraoptic, UNdl.'1.lamic, 88--89,107,109-melh)'I-D-asran:ue (N~'IOA) receplors, 120)".Slagmus. n. 80caloric, 63, 63cerebelbr, 87IJOSlrol3tory (hori:omal). 63in unconsciousnc:s.s. 64

\'estibular (hori:omal), 63

Oculomotor nCIYC (CN III) (J«' IlI'Idrr Cmni,'ll IlCn"el)Olfaclory ncn'c (CN I) (J«' Imlkr Cmnial nem~:s)

OlfaclOl')' sySlem, 65, 66Oligodcndrocytcs. 32Optic nen'e (CN II) (see undtrCranial nen'cs)Otic placode. 61Otitis media. 58Otosclerosis, 58Oxytocin, 104, 104

Pallidotom~'. 113P"petcircuit, 108--109, 109Papilledelll;\ (choked disk), 97Parkinson's disease, 113,\15, 1/6Pe!"SCver:ltion, 123Pia-amchnoid, 8Polyomyetilis, 45--46Polyneuritis, acutc idiopathic (Gui1tain H.1ITC syn­

drome).48Posrinfeetious polyneuritis (Guil\ain-B.'lrre s~'n-

drom<"), 48Presbycusis, 59Prolactin.inihihiting factor. 115Pronator drift, 121Prasopai,'llosia, /15Pscudolumor cerehri. 3DPsychic blindness. 109, \27Ptosis, 66, 82, 95. 97Pupil

Argyll-Robertson, 95. 96fixed dilated. 97relath'e afferent (Marcus Gunn), 95, 97

Purkinje cell, 85-86Pyramidal rra<:t, 42--44

Quadranmnopia ("pie in the sky~l. 91, lB. 124.115,130

homonymous, 93

Ramus (rami)communicating, of :lUWllOlllic ncrvous systcm, 98gray and white communiC;lting, 36, 36

Raphe nuclei, 118Rathke's pouch, n,17Raynaud's disease, 102Rcllex(es)

carO(id sinus. 73, 75corneal,55. 55l.67,68. 71.80gag (faucial), 73jaw jerk (masseler). 56, 56,561myO(aclic. 36,37pupillary light (see Cr.mial nen'cs; II (oplic)

91)Relina,91Rinne ICSt. 60Romberg. 47

Index 141.....................................................................................................................................................................................................-S,.ccule, 6/,62Schw,mn cells, 32Schw,mnoma (:ICOllstic neumm,I), J3, 34, 60ScOtoma, junclion, 91Serotonin (5·hydroxylryptamine, 5.HT). 117. /18Signs

&lbinski's,44Kcrnig's,9

Sinuses, of the dur::l,lO, 57Spina bitid;l, 26-28Spin'll cord. 1, 8, 36-48, /16, 1/7

blood supply, 15, 15components, 36-37Ie,;ions. 45-48 (St.. «Iso specific rnriries'

of mOCot neurons and conicospinalrr.lcu. 45.45-46,46

mucor/sensory combined. 47-48pcripher:11 nervous S)'Slem (PNS), 47sensol')' path ....":I)·. 46,47

positional chang~ in development, 27tracts of, 36-44 (sa «Iso TractlsU

SIr:lhismw, 69. 80Sui.te medullares, 49Srri;lrcnninalis, 105, 108Suimum, 112-113, 115-116, 118-120SulxJrur:11 hClllatOl1m, 8, 13, 23Substance?, 1/3,117Suh.tantia nigra, 4. 6, 7, 17, 52, 81,89, J 12,113,

/13,1/6,1/9Sydenham's chorea (St. Virus' dance), 114Syndromes

amnCSric (confabulal')'j, 109,mterior spin31 artery, 46-47,1Ilterior vermis, 87Amon's, 84Arnold·Chi;lri,28Argyll-RobertsOn pupil. 95. 96Balint's. 84Bcnedikl's,80-81Brown !Xqu,ml (spinal cord hemisccrion), 46---47Central JXlllline myelinolysis, 84crocodile le,lrs, 71Dandy-W;llker, 29dorsal midbmin (P,lrinilud's), 80, 95, 95(acial collic\llus, 49, 80(etill alcohol, 29Foster Kenn••'d\', 66, 109(rontililobc, )25Gersllm1l\I1'S, 125Guillain &lrr~, 48, 71Horner's, 47, 79, 80, 93, 95, 97, 102, 105of inapprollriMe ADH secreTion (SIADH), 106intcrnucle:lr ophthalmoplegia, 80, 96jugubr for:lInen, 82-83Kluver.BlIey, 109, 127l:lIubert·Emon my:lsrhenic, 102hueml inferior pontine, 80hlleml medullary (PICA). 78. 79

"Iockoo-in," 8J-84medi;ll inferior romine, 79, 79-80mediallongirudinal fasciculus (MLF, internuclear

opluhalrnoplegia), 80, 96, 96medial medullary, 78medial midhl3in (Weber's), 82MObius, 71m)'cslhenia gl3vis, 120of tlondolninant inferior p:.IIietallobule, 125one-and-a-half,96paramooian midbl3in (Benedikt's), 80-81PICA. 78poliom)'elitis,45--46posterior vermis, 87pupillaI')' light, 95Riley-D.lY (familial dysautonomia), 101-102Sh)·.Dra~oer, 102Srrnchan's. 110subcla\'ian Sle'oIl, 83, 81~lOP of the basilar," 81Weber's, 81Werdnig-Hoffmann,46Wernicke·KOI$llkoff, 88Wernicke's encC'ph:llopalhy, 110

S)"ringomelia, 47-48

Tabes dOlS3lis, 46T..1n)'Cyles, 32Tardive d)'Skinesia, 114Thalamus, I. 2, 4, 5, 13, 17,39,41,42,49,62,

88-90,112,113, 113, 1/7, 1/9blood supply, 90internal capsule, 90, 90 (sa ol.so Capsule: internal)major nuclei and connections, 89

Thiamine (vimmin 131) de6denC)', 105, 110, 110TIc douloureux (trigeminal neul3lgia), 56, 68Tmcts (see aho P:lthway[sll

conicobulbar, 52, 73, 76, 81,1/9corticospin:ll, 12, 38, 42, 45, 45-46, 46, 47, 51.

51,54,78,79,82,86,1/9dcnfOthahlmic,8/descending sympathetic, 79dorsal colllmn-meJiallemni:;cus pathway, 38-40, 39gcniclllocillc;lrinc (ue also Cmnial nerves: II (01'-

tic)91)Horner's, 78mamillothalmnic,B9.105olfactory, 50, 65,127optic, 4, 6, 7,17, B9, 91 (see ahoCranial nerves:

II (optic))solitary, 50, 69

nucleus of, 78spinocerebellar, 00rs.1l, 38spinorh:llarllic, 38, 47, 51. 79,80, BI , 89

ltltcl3l,78spinotri~'Cmin:II,50, 51, 5/,68,79,79,80supraopticohypophyseal, 104, 105trigemi1lQ(halamic, 53-55, 55, B9

::1.42 lnoex

TrilCI.r--Cmuimdruberohypophyseal. 104veslibulospinal, laleml, 38

Tmll5pon, axonal, 31Trigemin.'ll nerve (CN V) (su undeTCranial nerves)Tril,.ocminal neuralgia, 56Tremor, intention (cerebellar), 87

stalic, rdling (Parkinson), 113Trochlear nerYe (CN V) (su under Cranial nerves)Tuning fork 1t':S15, 59. 60t

Ulcer, peptic, 102-Uncal (lranSlclllO£ial) hernialion, 12, 66, 97Uncinate ri15, 115Uncus, 6, 7UPMN (upper mOlOr neuron) lesions, 45, 45-46,46Urinary bbdder, 100Utricle, 61, 62Uvula,73

VH!.'l.IS nerve (CN X) (see lIluler Cmnial nerves)V"SQ;l(rive intesrinal peptide (VIP), 101

Ventricles, 8, 9Ventrolateral thalamotomy, 113Vertigo, n. 80Vest:ibular system, 61-64Vesc:ibuloeoehlear nervt'; (CN VIII) (sa Ul'IdtT

Cranial nerves)Visual pathway, 91-92Visual system, 91, 91-97,93-96Vitamin BI2 neuropathy, 47Vi[;lmin B1 (thiamine) deficiency, 105, 110,

110

Wallerian degeneration, 31Walel'$hd infarcts, 131Weber's test, 60Wernicke's encephalopathy, 103, 105Wernicke's (fluent) aphasia, 125Wernicke's speeeh area, 125Wemig-Hoffman disease, 46White and gray communicating rami, 36, 36Wilson's disease (hepatolenticular degeneration),

113,114