neuroimaging of headaches

NEUROIMAGING OFHEADACHESLaszlo L. Mechtler

ABSTRACTImaging for headaches is one of the most frequent and at times challenging deci-sions a neurologist has to make in the clinical practice of neurology and is compli-cated by today’s medical-legal milieu and overseeing regulatory organizations.Although the final decision should always be made by the treating physician, theAmerican Academy of Neurology has developed practice parameters for the imag-ing of headaches. One strong criticism of the overzealous use of neuroimaging inpatients with headache is the frequency of incidental findings, which may in turnincrease a patient’s anxiety and potentially cause an exacerbation of symptoms. Thismay subsequently lead to unnecessary testing as well as neurosurgical intervention.The clinical interpretation of incidental findings and headaches is best made by aneurologist who is able to correlate the imaging findings with the patient’s symp-toms and examination. One of the principal precepts in medicine, “primum nilnocere” or “first, do no harm” to patients, should be considered in the interpreta-tion of these so-called abnormalities. The development of programs to certifycompetence in physicians who have completed accredited training programs inneuroimaging as well as headache medicine by the United Council for NeurologicSubspecialties is an important advancement that allows clinicians the opportunity toenhance quality of patient care.

Continuum Lifelong Learning Neurol 2008;14(4):94–117.

INTRODUCTIONThe most common complaint in thepractice of neurology is headaches.The International Headache Society(IHS) classifies headaches (Interna-tional Classification of Headache Dis-orders, 2nd Edition) into 14 major cat-egories, subdivided into three broadgroups: primary headache (categories1 to 4); secondary headache (catego-ries 5 to 12); and cranial neuralgias,central and primary facial pain, andother headaches (categories 13 and14) (Headache Classification Subcom-mittee of the International HeadacheSociety, 2004).

Although the paradigm in the di-agnosis and treatment has shifted to-ward primary headaches, there contin-ues to be a need for clinicians to ruleout organic, or so-called secondaryheadaches. Therefore, a never-endingtension exists between the knowledgethat primary headache disorders arefar more frequent and the urge to or-der neuroimaging studies out of fear ofmissing an uncommon malady. Al-though a “therapeutic scan” would begreatly appreciated by patients andtheir families, it can also complicateand confuse the situation. Secondaryheadaches represent a symptom of

Relationship Disclosure: Dr Mechtler has received personal compensation for speaking engagements withCerenex Pharmaceuticals, GlaxoSmithKline, Inc., Merck & Co., Inc., Ortho-McNeil Pharmaceutical, Inc.,Pfizer Inc, Schering-Plough Corporation, and UCB Pharma.Unlabeled Use of Products/Investigational Use Disclosure: Dr Mechtler has nothing to disclose.

Copyright © 2008, American Academy of Neurology. All rights reserved.

94

pathologic organic process and are as-sociated with more than 316 disordersand illnesses. Although practice guide-lines have been developed, theseguidelines are not designed to super-sede sound clinical judgment whentreating individual patients. The cost-to-benefit ratio in performing a studyis tempered by the medical and legalimplications of omitting the study. Asclinicians, neurologists need to under-stand the merits of neuroimaging andits effect in the management of pa-tients with headache.

NEUROIMAGINGIn 1994, the American Academy ofNeurology (AAN) approved a guide-line for the use of neuroimaging inpatients with headaches and a normalneurologic examination. The consen-sus of the AAN was that “In adult pa-tients with recurrent headaches thathave been defined as migraine, includ-ing those with visual aura, with norecent change in pattern, no history ofseizures, and no other focal neurolog-ical signs or symptoms, the routine useof neuroimaging is not warranted”(Quality Standards Subcommittee ofthe American Academy of Neurology,1994). Since headaches account forapproximately 4% of all outpatient vis-its, the final decision to image is left tothe physician on a case-by-case basis.

In 2000, the United States Head-ache Consortium Report was unable tomake any evidence-based recommen-dations with regard to the relative sen-sitivity of magnetic resonance imaging(MRI), compared with computerizedtomography (CT) in evaluating mi-graine or other nonacute headaches(Silberstein, 2000). In the past, the ad-vantage of CT was its cost; over the lastseveral years, however, a gradual de-crease has occurred in the reimburse-ment rate for MRI. Irrespective of cost,CT is the study of choice in acutetrauma, acute subarachnoid hemor-rhage (within 24 hours), and when

MRI is contraindicated. In contrast,MRI is more sensitive than CT in de-tecting neoplastic disease, cervicome-dullary lesions, pituitary disorders, andvascular diseases, including subduralhematomas, arteriovenous malforma-tions, ischemic disease, venous infarc-tions, dissections, aneurysms, andsubarachnoid hemorrhages (after 72hours). Intracranial hypotension andhypertension are also better evaluatedby MRI with and without gadolinium.MRI is also more sensitive in second-ary headaches of pregnancy, whichmay be caused by cardiovascular dis-ease, sinus thrombosis, pituitary apo-plexy, disseminated intravascular co-agulation, or emboli, keeping in mindthat contrast should be avoided. Theuse of CT in adults and children hasincreased sevenfold in the past 10years. CT scans contribute approxi-mately 65% of effective radiation dosefrom all medical x-ray examinations.Radiation exposure is a special con-cern in children, who are considerablymore sensitive to radiation than adultsand have a longer life expectancy, re-sulting in a potentially higher likeli-hood to develop cancers. Cliniciansmust continually think about reducingexposure as much as reasonablyachievable by (1) reducing radiationdose, (2) decreasing serial studies, and(3) utilizing other imaging modalities,such as MRI and ultrasonography(Brenner and Hall, 2007).

Since the first commercial MRI scan-ner was manufactured in 1980, MRItechnology has continued to advance.Resolution and sensitivity in MRI haveimproved because of larger magnet size,availability of paramagnetic contrast,and the selection of acquisition se-quences for specific pathologic indica-tions. Newer vascular imaging pack-ages, such as MR angiography (MRA)and MR venography (MRV), have alsoimproved the sensitivity of MRI.

MRA is not routinely done unlessthere is a history of thunderclap head-

KEY POINT:

� The consensusof AAN is that in“adult patientswith recurrentheadaches thathave beendefined asmigraine,including thosewith visual aura,with no recentchange inpattern, nohistory ofseizures, and noother focalneurologicalsigns orsymptoms, theroutine use ofneuroimaging isnot warranted.”

95

Continuum: Lifelong Learning Neurol 2008;14(4)

ache, a family history of aneurysms, orheadaches that are continuously ipsilat-eral or progressive in nature. In thesecases, a time-of-flight study MRA wouldbe appropriate. In circumstances inwhich the history may include headtrauma, thunderclap headache, or fam-ily history of vascular malformations oraneurysms, a gradient-echo sequence,which is sensitive for hemosiderin andcalcification, should also be done.

Gadolinium-containing contrastagents are often used in MRI to en-hance the quality of images. Becausegadolinium is renally excreted, caremust be taken to screen patients forrenal disease or dysfunction. While theuse of low-dose gadolinium-basedcontrast agents (0.1 mmol/kg bodyweight) in patients with impaired renalfunction has been shown to be non-nephrotoxic, doses greater than 0.2mmol/kg have been associated with arare disorder called nephrogenic sys-temic fibrosis (NSF) in patients withadvanced kidney failure. Factors asso-ciated with NSF include dialysis, mod-erate/end-stage renal disease (glomer-ular filtration rate less than 30 mL/min/1.73m2), and repeated or higher-than-recommended doses of gadoliniumcontrast. NSF is a debilitating andsometimes fatal disease affecting theskin, muscle, and internal organs(Broome et al, 2007). Gadolinium isroutinely used in patients with head-ache consistent with the criteria in Ta-ble 5-1. It is important for routine im-aging protocols to be established andapplied to ensure the quality and con-sistency of each image. A sample rou-tine protocol for patients with head-ache that is currently instituted at theDent Neurologic Institute is outlined inTable 5-2.

Neuroimaging ordered by a neu-rologist or headache specialist will of-ten have a higher diagnostic yieldthan images ordered in the primarycare setting. Sempere and colleagues(2005) reported a study in 1876 con-

secutive patients with nonacute head-aches referred to a neurology clinic.Neuroimaging detected significant le-sions in 1.2% of patients. Wang andcolleagues (2001) retrospectively re-viewed 402 adult patients who hadbeen evaluated for chronic headaches

KEY POINTS:

� Gradient-echoimages aresensitive toblood flow,calcification, andhemorrhage.

� High doses ofgadolinium-based contrastagents havebeen associatedwith a raredisorder callednephrogenicsystemic fibrosisin patients withadvanced kidneyfailure.

� Nephrogenicsystemic fibrosisis a rare andpotentially fatalsyndrome thatinvolves fibrosisof the skin,joints, muscle,and internalorgans.

� Neuroimagingdetectedsignificantlesions in 1.2%of patients withnonacuteheadaches.

TABLE 5-1 RecommendedRoutine Use ofGadolinium inPatients WithHeadache

‹ Patients with abnormalneurologic examination

‹ Patients with positionalheadaches

‹ Patients with exertional orValsalvamaneuver–exacerbatedheadaches

‹ Patients with cluster orneuralgia-type headaches orfacial pain

‹ Patients with known historyof cancer, AIDS, or infectiousdisease

TABLE 5-2 Standard Protocolfor Patients WithHeadache at theDent NeurologicInstitute

‹ T1-weighted axial 5 mm

‹ T2-weighted axial fast spinecho 5 mm

‹ Fluid-attenuated inversionrecovery (FLAIR) axial 5 mm

‹ Diffusion-weighted imagingaxial

‹ FLAIR and/or T1-weightedsagittal

‹ T2-weighted coronal 3 mmthrough circle of Willis

‹ HEADACHES

96


(duration of 3 months or greater) andhad no other neurologic symptoms orfindings. Major abnormalities that werefelt to be the actual cause of the head-ache were found in 15 patients (3.7%).Clinical suspicion is increased when cer-tain “red flags” (warning signs) are pres-ent as outlined in Table 5-3.

Neuroimaging in PediatricHeadachesMazzotta and colleagues (2004) per-formed a prospective study at multiplepediatric headache centers and foundthat 9.3% of the 1485 patients had in-

cidental findings. Findings that led tothe diagnosis of secondary headachewere observed in 9.1% of total pa-tients, including sinusitis in 57.0% andintracranial mass in 17.4%. The reportof the Quality Standards Subcommit-tee of the American Academy of Neu-rology and the Practice Committee ofthe Child Neurology Society (Lewis etal, 2002) made the following recom-mendations:

(1) Obtaining a neuroimaging studyon a routine basis is notindicated in children with

TABLE 5-3 “Red Flags” in Adult Patients With Headache

The “first or worst” headache (“thunderclap”)

Subacute headaches with increasing frequency and severity

Progressive or new daily persistent headache

Chronic daily headache

Headaches always on the same side

Headaches resistant to treatment

New onset of headaches in high-risk population

● Patients with cancer

● Patients who are HIV positive

● Patients with dementia

● Patients who are taking an anticoagulant

● Patients with neurocutaneous syndrome

New onset of headaches after age 50

Patients with headaches and seizures

Headaches associated with symptoms such as fever, neck stiffness, nausea, andvomiting

Headaches with focal neurologic deficits not meeting the InternationalHeadache Society criteria of migraine with aura

Headaches associated with papilledema, cognitive impairment, or personalitychange

Headaches precipitated by exertion, Valsalva maneuver, or positional changes

Atypical cranial neuralgias poorly responsive to treatment

Modified with permission from Evans RW, Rozen TD, Mechtler LL. Neuroimaging and other diagnostic testingin headache. In: Silberstein SD, Lipton RB, Dodick DW, editors. Wolff’s headache and other head pain. 8th ed.New York: Oxford University Press, 2007.

97


recurrent headaches and anormal neurologic examination.

(2) Neuroimaging should beconsidered in children with anabnormal neurologic examination(eg, focal findings, signs ofincreased intracranial pressure,significant alteration ofconsciousness), the coexistenceof seizures, or both.

(3) Neuroimaging should beconsidered in children in whomthere are historical features tosuggest the recent onset ofsevere headache, change in thetype of headache, or if there areassociated features that suggestneurologic dysfunction.

Just as in the adult population, clin-ical suspicion is increased when cer-tain red flags are present as outlined inTable 5-4 (Figure 5-1).

Headaches in Older AdultsSecondary headaches in patients overthe age of 50 present a challenge to theclinician. Only 2% of migraineurs havetheir first headache over the age of 50. Inaddition, as the incidence of primaryheadaches declines with age, the occur-rence of secondary headaches increases

with advancing age. Although neo-plasms may cause headaches in all agegroups, they are far more prevalent inpatients over the age of 50. The com-mon causes of headaches beginning latein life include primary and secondaryneoplasm, temporal arteritis, drug-in-duced headaches, trigeminal neuralgia,cervicogenic cervical myofascial pain,Parkinson disease, cerebrovascular dis-ease, postherpetic neuralgia, and associ-ated systemic diseases (Mechtler andStiles, 2005) (Figure 5-2).

Neuroimaging of PeripartumHeadachesHeadaches are one of the most commonsymptoms that occur in the postpartumperiod and are most frequent on days 3to 6 postpartum. Postpartum women of-ten have sleep deprivation along withirregular food intake and dehydration.The most common types of postpartumheadaches include tension-type head-aches, preeclampsia/eclampsia, spinalheadache, and migraine. Secondarycauses include cerebral venous throm-bosis, cerebral vasculopathy, subarach-noid hemorrhage, or intraparenchymalhemorrhage. The use of MRI duringpregnancy is considered safe, as mag-

KEY POINT:

� In children witha family historyofneurocutaneoussyndrome (ie,neurofibromatosis),a headache thatis poorlyresponsive totreatment is a“red flag” andmay warrantneuroimaging.

TABLE 5-4 “Red Flags” in Children

‹ Persistent headaches of less than 6-months’ duration that do not respond tomedical treatment

‹ Headache associated with abnormal neurologic findings, especially ifaccompanied by papilledema, nystagmus, or gait or motor abnormalities

‹ Persistent headaches associated with a negative family history of migraine

‹ Persistent headaches associated with substantial episodes of confusion,disorientation, or emesis

‹ Headaches that repeatedly awaken a child from sleep or occur immediatelyon awakening

‹ Family and medical history of disorders that predispose to CNS lesions andclinical laboratory findings that suggest CNS involvement

Reprinted with permission from Medina J, Pinter J, Zurakowski D, et al. Children with headache: clinicalpredictors of surgical space-occupying lesions and the role of neuroimaging. Radiology 1997;202:819.

‹ HEADACHES

98


FIGURE 5-1 A 15-year-old girl presented with positional headaches and normalexamination. A, FLAIR sagittal imaging confirms a “tight” posterior fossa,tonsillar herniation, and cervical syrinx. B, T2-weighted and (C) T1-weighted

gadolinium sagittal sequences rule out intramedullary mass. The diagnosis was Arnold-Chiari I malformation.

FIGURE 5-2 A 60-year-old man with a chronic frontal headache and growing “bump”on his forehead. A, T1-weighted contrast images show a large enhancingfrontal mass that erodes the calvarium and uplifts the scalp. B, Magnetic

resonance venography confirms infiltration and occlusion of the superior sagittal sinus.Headaches resolved after resection of a meningioma.

99


netic energy has not been shown to beharmful to the developing fetus. MRI ismore sensitive for uncommon disor-ders that may occur during pregnancy,such as pituitary apoplexy, cerebral ve-nous thrombosis, metastatic choriocar-cinoma, meningioma, prolactinomas,idiopathic intracranial hypertension,and subarachnoid hemorrhage (“senti-nel headaches”). For postpartum head-aches, an MRV is highly recommended.While gadolinium-based contrast agentsfor MRI are not recommended duringpregnancy, gadolinium contrast is notcontraindicated in lactating women.

MRI IN MIGRAINESThe most common abnormalitiesfound on MRI in migraineurs are whitematter lesions localized in the subcor-tical or periventricular white matter.These white matter lesions have beenvariably reported in 12% to 48% ofmigraineurs compared with 2% to 11%of control subjects (Evans et al, 2007).These multiple, small punctate hyper-intensities are seen best on fluid-atten-uated inversion recovery (FLAIR) im-ages. Several neuroimaging serieshave suggested an increase in preva-lence of T2-weighted foci of hyperin-tensities in patients who have mi-graines with aura. Kruit and colleagues(2004) evaluated 295 patients withproton density and FLAIR images in apopulation of migraineurs comparedwith well-matched controls (140 pa-tients). The results show that infarctswere seen most often in the posteriorcirculation of patients who experi-enced migraines with aura and whenmigraine attacks occurred more oftenthan once a month. Deep white matterlesions were also more common infemale migraineurs and in thosewhose attacks occurred more thanonce a month, but no differences wereseen between the migraineurs withand without aura. Meta-analysis fromseven case control studies determined

that patients with migraines had a 3.9times greater risk for white matter le-sions compared with controls (Swartzand Kern, 2004). Recent findings haveshown an increase in prevalence ofinfratentorial, mostly pontine, T2 hy-perintensities in migraineurs com-pared with the general population(Kruit et al, 2006).

The introduction of 3-tesla MR sys-tems into the clinical arena has im-proved the sensitivity for detectingCNS changes, thanks to an increasedsignal-noise ratio and spatial resolu-tion. Voxel-based morphometry is afully automated whole-brain tech-nique that is being used as an unbi-ased method for the assessment of dif-ferences in brain volume. Migraineurswith T2 white matter lesions had sig-nificant reduction of gray matter den-sity when compared with healthy con-trols. Such changes were located in thecortex of the frontotemporal lobe andin the cingulum (Rocca et al, 2006).Three-tesla imaging has also shownabnormalities in iron hemostasis with-in the periaqueductal gray matter. Irondeposits were increased within theperiaqueductal gray matter and pro-gressed with the severity of the head-ache (Welch et al, 2001).

An increased prevalence of patentforamen ovale (PFO) was found in pa-tients with migraine with aura but notin those without aura. PFOs werefound in approximately 20% to 25% ofthe general population and about 50%of patients who had migraine withaura. A moderate- or large-sized shuntwas found more often in the mi-graineurs than in the controls. Shunt-ing may occur at rest or with elevationin the right atrial pressure during Val-salva maneuver. PFO may be detectedby transesophageal echocardiogram,transthoracic echocardiogram, or trans-cranial Doppler of the middle cerebralartery with bubble injection of agitatedsaline (Spencer et al, 2004). Cardiac

KEY POINTS:

� There is noknown risk toperforming anMRI duringpregnancy, butgadoliniumcontrast is notrecommended.

� FLAIR imaging isthe mostsensitivesequence for theevaluation ofmigraine-relatedwhite matterlesions.

� TranscranialDoppler withagitated salinebubble is asensitive test forthe detection ofpatent foramenovale, whichoccurs in up to50% of patientswho havemigraines withaura.

‹ HEADACHES

100


MRIs are also being utilized more of-ten for the evaluation of PFOs (Hortonand Bunch, 2004; Mechtler, 2004).

MELAS and CADASILMELAS is the term used for the syn-drome clinically characterized by mito-chondrial myopathy, encephalopathy,lactic acidosis, and strokelike episodes.MRI findings include abnormal signalintensity in the basal ganglia and in-farctions. In patients with this disor-der, magnetic resonance spectroscopy(MRS) shows an elevation of lactateand may be more sensitive than MRIin the detection of MELAS-associatedabnormalities. Clinically, MELAS be-gins with migraine, then progresses tohemiplegic migraine and eventually tostroke. Approximately 90% of the pa-tients are symptomatic by age 40,and many of these “strokelike” eventscross usual vascular territories. MRSmay potentially be used as a screeningdevice for mitochondrial cytopathyand as a tool to follow treatment re-sponse. MRS does show a lactate dou-blet peak at 1.3 ppm in 65% of cases,and changes may precede diffusion-weighted image (DWI) abnormalities.On routine MRI, these acute strokelikecortical lesions have a so-called shiftingspread of appearance, disappearance,and reappearance elsewhere. The le-sions cross typical vascular territories,and the lactate level in the CSF is ele-vated (Kaufmann et al, 2004).

CADASIL (cerebral autosomal domi-nant arteriopathy with subcortical in-fracts and leukoencephalopathy) is seenin young adults and presents with mi-graines with and without aura, mooddisturbance, focal neurologic deficits,strokes, and dementia. Most patientswill show symptoms by the age of 60,usually beginning with a migraine anda prolonged aura. CADASIL is causedby a NOTCH3 mutation on chromo-some 19 that can be autosomal domi-nant or sporadic. With dynamic contrast-enhanced MRI, a significant reduction of

cerebral blood volume within subcor-tical T2 white matter lesions is found,but not in normal-appearing white mat-ter. Typical white matter changes inCADASIL involve the anterior temporalpoles and the external capsule. Thereare two types of lesions: (1) large coa-lescent lesions in the white matter, isoin-tense on T1-weighted imaging (T1WI)and bright on T2-weighted imaging(T2WI); and (2) small well-delineatedlacunaelike lesions that spare the cor-tex and are hypointense on T1WI andhyperintense on T2WI. CADASIL isunderrecognized and underdiagnosedand should be considered in patientswith the following history:

• One or more recurrent subcorti-cal ischemic stroke, especiallybefore the age of 60 and in theabsence of vascular risk factors

• Migraines with aura, especiallywith atypical and prolonged auras

• Early cognitive decline with sub-cortical dementia (Markus et al,2002)

INCIDENTAL FINDINGS ON MRIIncidental findings are previously un-detected abnormalities with potentialclinical relevance that are unexpect-edly discovered and unrelated to thepurpose of the examination. One ofthe difficulties with ordering MRIs inmigraineurs or patients with headacheis the relatively high frequency of in-cidental findings. Depending on theexperience of the physician orderingthe tests, these findings may be misin-terpreted as the cause of the head-ache. Some of the more common inci-dental findings seen on MRI areoutlined in Table 5-5. These findingsare often categorized based on theirclassification as a normal anatomicvariant, parenchymal lesion, or cysticlesion.

Headaches are rarely, if ever, asso-ciated with the above-noted findings.Exceptions are enlarged pineal cysts or

KEY POINTS:

� Magneticresonancespectroscopyshows a lactatepeak at 1.3 ppmin the majorityof patients withMELAS and mayprecedediffusion-weightedimagingabnormalities.

� Typical whitematter changesin CADASILinvolve theanteriortemporal polesand the externalcapsule.

101


arachnoid cysts that are associated withmass effect or obstructive hydrocepha-lus. Telangiectasias, or developmentalvenous anomalies, when associatedwith other vascular malformations (ie,cavernous hemangioma) can rarelycause hemorrhage. In general, far toomuch emphasis is placed on these inci-dental findings in regard to the patho-physiology of the patient’s pain syn-drome and furthermore may causeunwarranted patient anxiety as well as

further diagnostic testing, which may beunnecessary and potentially harmful(Figure 5-3).

Normal Anatomic VariantsVariations of CSF-containing spacesare commonly seen as incidental find-ings. These include ventricular asym-metry, cavum septi pellucidi, cavumvergae, and cavum veli interpositi.

Ventricular asymmetry of thefrontal horns and bodies of the lateralventricles is common, with the leftgenerally larger than the right. Withlateral ventricular asymmetry, close in-spection of the foramina of Monro isneeded to rule out masses in this re-gion, such as colloid cysts, giant cellastrocytomas, or intraventricular tu-mors.

Present in 2% to 3% of normaladults, cavum septi pellucidi is a vari-able-sized CSF collection between thetwo layers of the septum pellucidum,anterior to the foramina of Monro. Ithas been reported more often inclosed-head injuries as well as inschizophrenics but has not been re-ported with an increase in frequencyamong patients with headache. Por-tions of cavum septum pellucidi ex-tending posteriorly to the columns ofthe fornix are known as the cavumvergae. Cavum velum interpositum isa triangle-shaped CSF space betweenthe bodies of the lateral ventricles, be-low the fornices, and above the thirdventricle (Epelman et al, 2006).

Arachnoid granulations are smallprotrusions of the arachnoid throughthe dura. They extend to the venoussinuses of the brain, allowing CSF toexit the subarachnoid space and enterthe bloodstream. These well-definedfilling defects are seen most oftenaround the transverse and sigmoid si-nuses. Arachnoid granulations havealso been called pacchionian bodies.On high-resolution MRIs utilizing thinslices, up to 70% of patients werefound to have arachnoid granulations.

KEY POINTS:

� Incidentalfindings are notthe cause ofheadache exceptwhen cysts areassociated withmass effect andobstructivehydrocephalusor whendevelopmentalvenousanomalies ortelangiectasiasare associatedwith otherarteriovenousmalformationsor hemorrhage.

� Incidentalfindings increasea patient’sanxiety and mayalso potentiallycause needlessimaging andneurosurgicalintervention.

TABLE 5-5 IncidentalFindings Seen onMRI

‹ Normal Anatomic Variant

Ventricular asymmetry

Cavum septi pellucidi/Cavumvergae

Cavum veli interpositum

Arachnoid granulations

Mega cisterna magna

Enlarged Meckel cave

Transverse sinus asymmetry

‹ Parenchymal

White matter lesions

Developmental venousanomaly

Capillary telangiectasia

Lipoma

Low-lying cerebellar tonsils

Prominent perivascular spaces

Ependymitis granularis

‹ Cysts

Pineal cyst

Arachnoid cyst

Choroid plexus cyst

Choroidal fissure cyst

Tornwaldt cyst

Sinus retention cyst

‹ HEADACHES

102


DWIs showed isointensity to normalbrain tissue, which is higher than thereported signal intensity of arachnoidcysts and lower than that of epider-moids (Kan et al, 2006).

A large cisterna magna, alsocalled mega cisterna magna, is thespace between the medulla oblongataand the inferior surface of the cerebel-lum. Mega cisterna magna is a cystlikeenlargement of the cisterna magnaseen in 1% to 3% of the population.Mega cisterna magna communicateswith the subarachnoid space and thefourth ventricle.

An enlarged Meckel cave is locatedjust inferolateral to the cavernous si-nus and is hyperintense on T2WIs. Itcontains the gasserian ganglion. Occa-sionally, Meckel caves may be quiteenlarged but are usually symmetric.The enhancement pattern is never ho-mogenous, but circumferential.

ParenchymalDevelopmental venous anomalies(DVAs), also called venous angiomas,are congenital cerebrovascular malfor-mations with angiogenically maturevenous elements. The veins that com-promise a DVA usually form a littlecluster called a caput medusae. Theyare most often seen adjacent to thefrontal horn of the lateral ventricle orwithin the cerebellum. There is no ar-terial component to these malforma-tions. The incidence of DVAs has beenreported to be 2.6%. DVAs are poorlyvisualized on T1WIs, and the study ofchoice is a T1-weighted contrast se-quence. Large DVAs can possiblypresent as a flow void on T2WIs. Fif-teen percent to 20% of DVAs occurwith a coexisting cavernous malforma-tion and have also been associatedwith telangiectasias. Although therehave been case studies of patients

FIGURE 5-3 Incidental findings. A, Choroidal fissure cyst (arrow) (FLAIR) B, Choroidplexus cyst (arrow) (FLAIR). C, Developmental venous anomaly (arrow) (T1-weighted imaging with gadolinium). D, Tornwaldt cyst (arrow) (FLAIR). E,Ependymitis granularis (arrows) (FLAIR). F, Enlarged perivascular spaces(arrows) (T2-weighted imaging).

103


who have had seizures or brain hem-orrhages, DVAs do not cause anysymptoms and are felt to remain dor-mant or silent throughout life. Mostsymptomatic patients have associatedcavernous malformations, which arebest observed on gradient-echo im-ages. In a patient diagnosed with aheadache or migraine, a DVA is aprobable incidental finding unless thereis evidence of an associated cavernousmalformation or blood products.

Capillary telangiectasias havebeen recognized with increasing fre-quency on MRI studies. Most likelylocalized in the pons, capillary telan-giectasias may be hyperintense onT2WIs and hypointense on gradient-echo imaging. They are not seen onnoncontrast TIWI, but are best visual-ized with gadolinium-contrast TIWIstudies. There is no mass effect, and

they are generally asymptomatic.About two-thirds of capillary telangi-ectasias reveal an enlarged drainingvessel. The overwhelming majority ofcapillary telangiectasias are clinicallysilent, but when associated with hem-orrhage, they are usually also associ-ated with other vascular malforma-tions (Castillo et al, 2001) (Figure5-4).

Intracranial lipomas are malfor-mations believed to result from abnor-mal differentiation of the meninxprimitiva, the undifferentiated mesen-chyma that surrounds the developingbrain. CNS lipomas are congenital mal-formations, not true neoplasms. Theseare predominantly located in the sub-arachnoid space: 80% are in the mid-line, 80% are supratentorial (of which40% to 50% are in the interhemisphericfissure over the corpus callosum), 15%

KEY POINT:

� Gradient echomay show ahypointensebloomingartifact indevelopmentalvenousanomalies if acoexistingcavernousmalformation ispresent.

FIGURE 5-4 A 35-year-old patient with lifelong history of episodic severe headachesconsistent with International Headache Society criteria for migraineswithout aura. MRI shows evidence of an enhancing lesion within the pons

consistent with a capillary telangiectasia. C, D, The incidental finding was not seen on TI-weighted imaging noncontrast or T2-weighted imaging sequences, except for subtlechanges on FLAIR. A, B, Patient responded well to pharmacotherapy.

‹ HEADACHES

104


to 20% are suprasellar, 10% to 15% arein the pineal region, and 20% are in-fratentorial. Blood vessels and cranialnerves almost always course throughthem; therefore, surgical treatment hasa high morbidity and is rarely indi-cated. Interhemispheric lipomas arealmost always associated with hypo-genesis or agenesis of the corpus cal-losum. On CT, lipomas are sharply de-marcated areas of hypodensity. TheMR appearance of a lipoma is that of ahyperintense mass on T1-weighted se-quences and hypointense on long rep-etition time (T2WI). Large lipomas willreveal chemical shift artifact resultingfrom the different chemical shifts ofwater and fat. Chemical shift artifactresults in the appearance of a dark rimat one edge of an object (eg, lipoma)and a bright rim at the opposite edge.Application of a fat-saturation pulse(short tau inversion recovery) willmake the lipoma hypointense to graymatter, confirming the diagnosis anddistinguishing it from a hemorrhage(Bakshi et al, 1999).

Large perivascular spaces, or Vir-chow-Robin spaces, are fluid-filledspaces that appear to contain CSF andsurround penetrating arteries predom-inantly in the basal ganglia. Othercommon locations are midbrain, deepwhite matter, and the subinsular cor-tex. They can be differentiated fromlacunar infarcts by their typical loca-tion, CSF signal in all pulse sequences,and lack of surrounding gliosis (FLAIRhyperintensity). Numerous prominentVirchow-Robin spaces in the basalganglia are called etat crible.

Ependymitis granularis is charac-terized by small foci of increased T2-signal intensity and is commonly seenalong the anterolateral aspect of thefrontal horns. This represents a focalpooling of interstitial fluid. Ependymi-tis granularis should not be mistakenfor demyelinating plaque, microangi-opathy, or transependymal CSF flow.

CystsPineal cysts on high-resolution MRIare seen in 23% of the normal popu-lation. Although the prevalence of pi-neal cyst in autopsy series has beenreported to be between 25% and 40%,pineal cysts are non-neoplastic, in-trapineal, homogeneous fluid-filledcavities clearly distinct from the tec-tum. Sixty percent of pineal cysts areslightly hyperintense to CSF on T1WI,while on FLAIR they are mildly hyper-intense. A TIWI sagittal image will re-veal a lack of mass effect on the adja-cent structures, such as the tectum andcorpus callosum, and 60% will en-hance either completely or partially.Most pineal cysts are clinically silent,discovered incidentally, and have agender ratio of 3:1 favoring females.Benign pineal cysts are usually lessthan 3 cm in size, homogenous, andcause no perilesional edema or hydro-cephalus. When not associated withmass effect, pineal cysts rarely causeheadaches (Pu et al, 2007).

Arachnoid cysts are the most com-mon congenital cystic abnormalities inthe brain that do not communicatewith the ventricular system. Fifty per-cent to 60% are found in the middlecranial fossa, while other locations in-clude the cerebellopontine angle(10%), suprasellar (10%), and miscel-laneous (convexity, quadrigeminal).They constitute approximately 1% ofall intracranial masses. Even if they arelarge, arachnoid cysts are usuallyasymptomatic and have a male-to-fe-male ratio of 4:1. It is uncommon formiddle fossa arachnoid cysts to be as-sociated with headaches. An MRI willtypically show a sharply demarcatedround/ovoid extraaxial cyst that fol-lows CSF signal on all sequences. DWIshows no restriction hypointensitiesand may be used to help differentiate atrue arachnoid cyst from an epider-moid cyst (Osborn and Preece, 2006)(Figure 5-5).

KEY POINTS:

� Chemical shiftartifact and fat-suppressionpulse sequencehelpdifferentiate alipoma from ahemorrhage.

� Short tauinversionrecovery is usedto suppress fatsignal.

� An arachnoidcyst is a well-demarcated,round/ovoid,extraaxial cystthat follows CSFsignal. Diffusion-weightedimaging ishypointense,while inepidermoids it ishyperintense.

105


A choroid plexus cyst is the mostcommon cyst seen intracranially inadults. Most cases are hyperintense onT1WI as well as T2WI. A rim or nod-ular enhancement with contrast ispresent. A high signal or restricted dif-fusion is seen on DWI in 65% of pa-tients. Choroid plexus cysts are preva-lent in approximately 40% of older

patients, and they are usually bilateral,rarely causing symptoms.

Choroidal fissure cysts are rela-tively common incidental findings.They are typically ovoid, 5 mm to 30mm in diameter, lateral to the cisternaambiens, and superior medial to thehippocampus within the choroidal fis-sure. They follow a CSF signal in all

FIGURE 5-5 A 40-year-old man presented to his primary doctor with a frontal naggingheadache that was progressive over the past week. FLAIR (A) and spin-echoT2-weighted imaging (B) showed evidence of bilateral middle fossa

arachnoid cysts (arrow). In addition, significant hyperintensities were seen in the ethmoidsinuses. The patient was treated for acute sinusitis with complete resolution of his pain.Subsequent images showed near complete resolution of the ethmoiditis (C, D, [arrows])and unchanged incidental finding of middle fossa arachnoid cysts.

‹ HEADACHES

106


pulse sequences and are asymptom-atic (Osborn and Preece, 2006).

A Tornwaldt cyst is a benign de-velopmental lesion located on the pos-terior wall of the nasopharynx on themidline, with an incidence of 0.06%.The content of the cyst is generallyhigh in protein and anaerobic bacteria.As a result, Tornwaldt cysts appear to behyperintense on T1WI and T2WI and donot enhance. Patients with these cystsare generally asymptomatic but rarelydevelop halitosis (Moody et al, 2007).

The detection of incidental find-ings poses various practical and ethi-cal issues. Performing MRIs at high-field strength and with more sensitivesequences may lead to the detection ofsubtle brain abnormalities that wouldnot have been detected previously.Medically significant findings in asymp-tomatic patients undergoing imaging oc-cur in 1% to 2% of cases. A recent pro-spective, population-based cohort studyof 2000 patients concluded that asymp-tomatic brain infarcts were present in7.2% of patients, cerebral aneurysms in1.8%, and benign primary tumors in1.6%. White matter lesions were foundin all but 5.4% of participants aged 45 to59 and in all but 2% of those aged 75and older (Vernooij et al, 2007).

Incidental findings in a healthy pe-diatric population were detected in21% of patients (Kim, 2002). Of these,8% of the total subject population re-quired either routine or urgent clinicalreferral. The most common nonrefer-rable finding was chronic sinusitis. Inpatients who required referral, find-ings included acute sinusitis, focalwhite matter lesions of uncertain etiol-ogy, and tonsillar ectopia. Of the chil-dren who presented to the emergencydepartment with headaches, 77% hada secondary cause. This is significantlyhigher compared with adults who hada 16% to 20% incidence of secondaryheadaches on presentation. Of thesechildren, 45% suffered from secondaryheadaches with neurologic causes.

In general, patients with headache,especially migraineurs, have a relativelyhigh incidence of anxiety. For childrenand adults, the presence of comorbidanxiety or depression was associatedwith significantly higher medical costswhen compared with migraine alone(Pesa and Lage, 2004). An incidentalfinding can place added psychologicalburden on these patients, which wouldunfortunately magnify their symptoms.Most incidental findings do not causeheadaches; still correlation betweenheadache and incidental findingsshould be made by a neurologist orneurosurgeon. Finally, it is importantto convey to the patient that only aclinical expert can label neuroimagingfindings as “symptom related,” “inci-dental, but without consequences,” or“incidental with consequences.”

RHINOSINUSITISRhinosinusitis consists of a group of dis-orders characterized by inflammation ofthe nasal mucosa and the paranasal si-nuses. The IHS criterion for acute frontalsinus headache is pain located directlyover the sinus that can radiate to thevertex or behind the eyes. An acutemaxillary sinus headache is located overthe antral area and can radiate to theupper teeth and the forehead. Acuteethmoiditis is a headache that is locatedbetween and behind the eyes and canradiate to the temporal area. Acute sphe-noiditis headache is located in the oc-cipital area, the vertex, the frontal re-gion, or behind the eyes (Silberstein,2004). Imaging characteristics of acutesinusitis include air-fluid levels, partialor complete opacification of a sinus, andmucosal membrane thickening of atleast 4 mm. Findings suggestive ofchronic sinusitis include mucosal thick-ening, bony remodeling, polyposis, andmucous retention cysts. Incidental sinusinflammation is present on MRI in morethan 32% of asymptomatic patients.Polyp and retention cysts are a rarecause of headaches (Cady et al, 2005).

KEY POINTS:

� Incidentalfindings are seenin 21% ofhealthy children.

� Nasal changeson MRI fluctuateseveral times aday.

107


Imaging findings of mucosal thickeningfluctuate with the normal nasal cycle.There is a cyclical passive congestionand decongestion of each side of thenasal turbinates, nasal septum, and eth-moid air cells mucosa that rotates fromside to side over the course of 1 to 8hours. Chronic sinusitis is not validatedas a cause of headaches or facial painunless it relapses into the acute stage.Although most headache specialistsagree that chronic recurrent headachesare rarely caused by sinus disease, theexception to the rule would be sphe-noid sinusitis. This is an uncommon in-fection and accounts for approximately3% of all cases of acute sinusitis. Typi-cally, this headache is aggravated bystanding, walking, bending, or cough-ing and is the most common symptomof acute sphenoid sinusitis.

IDIOPATHIC INTRACRANIALHYPERTENSIONIdiopathic intracranial hypertension(IIH), also known as pseudotumorcerebri, is characterized by elevatedCSF pressure without ventriculomeg-aly. The condition occurs most com-monly in obese women of childbear-ing age. The incidence may be at least19 per 100,000 in women between theages of 20 and 44 who are at least 20%above their ideal body weight. Diag-nostic criteria of IIH include: (1) in-creased intracranial pressure greaterthan or equal to 250 mm H2O; (2)symptoms or signs of increased intra-cranial pressure without any localizingfeatures; no mass or lesion; no evi-dence of hydrocephalus, structural orvascular lesion; normal CSF contents;and (3) no clinical or neuroimagingsuspicion of venous sinus thrombosis.Symptoms most commonly reportedin a case-control study of outpatientswith IIH include headaches (94%),transient visual obscuration (68%),pulse-synchronous tinnitus (58%),photopsia (54%), and retrobulbar pain(44%) (Friedman, 2004). The head-

ache profile is consistent with a severedaily pulsatile headache that graduallyincreases in intensity. There may beassociated nausea but rarely vomiting.Papilledema is the hallmark sign ofIIH. Horizontal diplopia occurs in ap-proximately one of three patients withIIH, and sixth nerve palsies are presentin 10% to 20% of patients.

On the TIWI, a partially emptysella turcica is seen quite often. Ingeneral, partial empty sellas are evi-dent in 30% of the normal population.Empty sellas without headaches is mostlikely an incidental finding (Binder et al,2004). Enlarged tortuous optic nervesheaths and posterior sclerae flattening,as well as small venous sinuses andveins, may also be seen in IIH. Afterappropriate treatment, which may in-clude weight loss, carbonic anhydraseinhibitors, serial lumbar punctures, orlumbar puncture shunt/optic nervesheath fenestration, normalization ofthe size of the cerebral sinuses andveins may occur, as well as reversal ofthe partial empty sella. In this way,imaging can be used to follow the pa-tient’s response to the treatment.

SPONTANEOUS INTRACRANIALHYPOTENSIONIntracranial hypotension is a frequentlymisdiagnosed syndrome of headachecaused by reduced intracranial CSF pres-sure. CSF volume depletion may occurafter trauma, after craniotomy or lumbarpuncture, and after trivial trauma. Intracra-nial hypotension also may be spontane-ous, especially in patients with connec-tive-tissue disorders such as Marfansyndrome. The typical clinical profile is ayoung or middle-aged adult with ortho-static headaches. MRI abnormalities mostoften seen on sagittal and axial T1WI in-clude brain descent in 40% to 50% ofcases, caudal displacement of tonsils in25% to 75% of cases, diffuse pachymenin-geal dural enhancement in 85% of cases,and bilateral subdural fluid collections in15% of cases, of which the majority are

KEY POINTS:

� Sinus retentioncysts and/orpolyps are a rarecause of chronicheadachesunless theyinvolve thesphenoid sinus.

� Empty orpartially emptysella is nearlyalways anincidental andasymptomaticfinding, but itmay beassociated withidiopathicintracranialhypertension.

� Imagingcharacteristics ofidiopathicintracranialhypertensioninclude emptysella, enlargedtortuous opticnerve sheaths,posterior scleraeflattening, andsmall venoussinuses.

‹ HEADACHES

108


hygromas. Other cerebral findings includecrowding of the posterior fossa, engorge-ment of the cerebral venous sinuses, andobliteration of some of the subarachnoidcisterns (prepontine or peri-chiasmatic cis-terns) (Farb et al, 2007). Within the spine,evidence of extra-arachnoid fluid collec-tions, meningeal diverticula, spinal pachy-meningeal enhancement, and engorge-ment of the spinal epidural venous plexuscan be seen. At times, identification of theactual leak may be seen (Schievink, 2006).In patients with chronic positional head-aches, a T1-weighted contrast study ismandatory if one wants to diagnosespontaneous intracranial hypotensionsyndrome (Mokri, 2004) (Table 5-6)(Figure 5-6).

CEREBRAL VENOUSTHROMBOSISHeadaches are a prominent symptomin 75% to 95% of patients with cerebralvenous thrombosis (CVT) (Cumurciucet al, 2005). The headaches of CVT arepersistent and can be worsened by aValsalva maneuver or recumbency.

Local causes of CVT include mastoid-itis, sinusitis, trauma, or neurosurgicalprocedures. More systemic causes in-clude septicemia, herpes, HIV, cancer,prothrombotic conditions (factor VLeiden mutation), protein S deficiency,pregnancy, use of oral contraceptives,and vasculitis. Other symptoms andsigns of CVT include seizures, papill-edema, altered consciousness, and fo-cal neurologic symptoms. Only 15% to30% of the patients experience head-aches alone (Leach et al, 2006).

MRI and MRV are recommended forthe appropriate evaluation of patientswithsuspectedCVT. Transverse sinus hypopla-sia and atresia are normal variants. Asym-metric transverse sinuses are seen in up to50% of patients, with partial or completeabsence of one transverse sinus in 20% ofthe cases. In most cases, the right sinus islarger than the left (Alper et al, 2004). OnT1WI, acute thrombus is isointense whilesubacute thrombus becomes hyperin-tense. On T2WI, initially the thrombus ishypointense and then becomes hyperin-tense when subacute. The T2 gradient-

KEY POINTS:

� In patients withpositionalheadaches, acontrast MRI isneeded to ruleout intracranialhypotension.

� Transverse sinusasymmetry isseen in nearly50% of patients,with right beingmore dominant.

� Intracranialhypertensionoccurs in 20%to 40% ofpatients withcerebral venousthrombosis.

TABLE 5-6 International Headache Society Diagnostic Criteria ofHeadache Attributed to Spontaneous (or Idiopathic)Low CSF Pressure

‹ Diffuse and/or Dull Headache That Worsens Within 15 Minutes AfterSitting or Standing With at Least One of the Following:

Neck stiffness

Tinnitus

Hyperacusia

Photophobia

Nausea

‹ At Least One of the Following:

Evidence of low CSF pressure on MRI

Evidence of CSF leakage on conventional myelography, CT myelography, orcisternography

CSF opening pressure less than 60 mm H2O on sitting position

Data from Headache Classification Subcommittee of the International Headache Society. The internationalclassification of headache disorders: 2nd edition. Cephalgia 2004;24(suppl 1):1–160.

109


echo image shows that the thrombus ishypointense but “blooms” (Idbaih et al,2006). In 40% of cases, a DWI shows ahyperintense clot and an occluded vessel.With contrast, a peripheral enhancementaround the acute clot is usually present,similar to the ‘‘empty delta sign’’ on con-trast-enhanced CT. On MRV, there is anabsence of flow and an occluded sinuswith abnormally enlarged collateral chan-nels (Figure 5-7).

COLLOID CYSTThird ventricular colloid cysts may be acause not only of cough and exertionalheadaches, but also of thunderclapheadaches. Headaches are the mostcommon symptom of a third ventricularcolloid cyst and are reported in 68% to100% of diagnosed patients. The head-

ache is generally located in the bilateralfrontoparietal or frontooccipital region.Pain is typically quite severe and re-lieved by recumbency. Loss of con-sciousness, change in cognition, sei-zures, coma, and death may occur. Themean size of colloid cysts is 15 mm, and99% wedge near the foramen of Monro,attached to the anterior, superior, thirdventricular roof. Two-thirds are hyperin-tense on T1WI, while the majority areisointense to the brain on T2WI. DWIdoes not restrict, and on FLAIR it is hy-perintense. MR is also predictive of theease with which the colloid cyst can beaspirated; if the signal intensity is darkon T2WI, signifying a high viscosity(high-proteinaceous or cholesterol-laden cysts), it will be quite difficult toaspirate (Armao et al, 2000). A patientwith positional headaches associatedwith a colloid cyst, especially accompa-

KEY POINT:

� “Location,location,location” is thebest clue tolocating colloidcysts; 99% arewedged into theforamen ofMonro (anteriorsuperior thirdventricle).

FIGURE 5-6 Gadolinium-contrast magnetic resonance images in the axial, coronal, andsagittal plane demonstrating diffuse pachymeningeal thickening andenhancement. The patient is a 40-year-old man with reports of postural

headaches after resection of left middle fossa meningioma. In patients with positional orexertional headaches, contrast studies may be diagnostic in intracranial hypotension.

‹ HEADACHES

110


nied by hydrocephalus, should be im-mediately referred to a neurosurgeon(Hellwig et al, 2003) (Figure 5-8).

CHIARI I MALFORMATIONCough, exertional, and sexual head-aches may be classified as primary, butthe clinician must search for secondarycauses that include Arnold-Chiari type 1malformation, subarachnoid hemor-rhage, intracranial metastasis, posteriorfossa masses, carotid or vertebral arterydissection, and cerebral aneurysm.

Chiari I malformation is a congen-ital malformation with cerebellar ton-sillar herniation of at least 5 mm belowthe foramen magnum. When symp-tomatic, crowding of the craniocervi-cal junction, obstructive hydrocepha-lus, and syringomyelia may occur. Thefundamental problem appears to beunderdevelopment of the posteriorfossa. Symptoms most commonly re-ported in patients with Chiari I malfor-mation include suboccipital headaches,retroorbital pressure or pain, clumsi-ness, dizziness, vertigo, tinnitus, pares-

thesias, muscle weakness, and lowercranial nerve symptoms (Arnett, 2004).

The imaging characteristics ofChiari I malformation include tonsilsthat extend more than 5 mm below theline connecting the basion with theopisthion. This is best seen on sagittalT1WI. Tonsillar tips that extend lessthan 5 mm below the foramen mag-num are normal and may be calledtonsillar ectopia. Cerebellar tonsilsnormally ascend with age; an exten-sion of 6 mm is normal until the age of10, 5 mm for patients aged 10 to 30years, and 4 mm for those aged 30 to80 years. In the typical Chiari I mal-formation, the low-lying tonsils arepointed in a “peglike” manner andhave a vertical (not horizontal) orien-tation. There is usually a compressedor absent cisterna magna. Syrinx canoccur in 15% to 75% of patients.Phase-contrast MRI reveals pulsatilesystolic tonsillar descent and ob-structed CSF flow through the foramenmagnum (Hofkes et al, 2007). Theworkup for a Chiari I malformation

KEY POINTS:

� Symptoms ofArnold-Chiari Imalformationincludesuboccipitalheadaches,retroorbitalpressure or pain,clumsiness,dizziness,vertigo, tinnitus,paresthesias,weakness, andcranial nervesymptoms.

� Cerebellartonsils, whichare displaced bymore than 5 mmto 6 mm belowthe level of theforamenmagnum with“peglike”(triangular)appearanceconfirm thediagnosis ofChiari Imalformation.

FIGURE 5-7 A 32-year-old woman who presented with a severe headache and seizure.Diffusion-weighted images (A) confirm an acute right frontal lobe infarctnot in the typical arterial distribution (arrow). T1- and T2-weighted images

were normal within the first 24 hours of presentation. T1-weighted sagittal (B) imagesshowed a increased signal (arrow) representing a thrombus within the superior sagittalsinus. Magnetic resonance venogram (C) and venous phase angiogram (D) support thediagnosis of superior sagittal thrombosis (arrows indicate occlusion). Risk factors forvenous thrombosis include: dehydration, pregnancy, oral contraceptives, trauma,disseminated intravascular coagulation, neoplasms, hypercoagulable states, infections, andidiopathic.

Reprinted from Evans RW, Rozen TD, Mechtler LL. Neuroimaging and other diagnostic testing in headache. In:Silberstein SD, Lipton RB, Dodick DW, editors. Wolff’s headache and other head pain. 8th ed. New York: OxfordUniversity Press, 2008:86. By permission of Oxford University Press, Inc.

111


should include a brain MRI to rule outa secondary Chiari I malformation anda complete spine MRI to rule out syr-inx and tethered cord (Case 5-1).

CRANIAL NEURALGIANeuralgias are defined as intenseburning and stabbing pain caused byirritation or damage to a nerve. Neu-ralgia may be idiopathic or secondary.The prototype of cranial neuralgia is tri-geminal neuralgia, which is character-

ized by a brief electric shocklike pain,most frequently in the maxillary andmandibular divisions of cranial nerve V.Secondary causes of cranial neuralgiasinclude skull-base tumors, vascular com-pression, neuritis, multiple sclerosis,herpes zoster, sinus disease, dental dis-ease, and trauma. Glossopharyngealand occipital neuralgia are well-defined,but far less common, cranial neuralgias.Secondary causes of trigeminal neural-gia include leptomeningeal disease (ie,

FIGURE 5-8 A 60-year-old patient with episodic headaches and syncope. A, FLAIR axialimage showing a right lateral ventriculomegaly and early transependymalCSF flow. B, T1-weighted (T1WI) fat saturation axial image confirms an

ovoid mass adjacent to the right foramen of Monro (arrow). C, Sagittal T1WI images showthe colloid cyst as a mass (arrow) that shortens the T1WI (hyperintense) consistent withproteinaceous material. D, The T2WI image shows the short T2 cyst (arrow) enlarging andpartially obstructing the intraventricular foramen with transependymal CSF leak adjacentto the frontal pole.

Reprinted from Evans RW, Rozen TD, Mechtler LL. Neuroimaging and other diagnostic testing in headache. In:Silberstein SD, Lipton RB, Dodick DW, editors. Wolff’s headache and other head pain. 8th ed. New York: OxfordUniversity Press, 2008:70. By permission of Oxford University Press, Inc.

‹ HEADACHES

112


carcinomatosis) and primary tumors,such as adenoid cystic carcinoma andsquamous cell carcinoma with retro-grade perineural spread of tumor intothe cavernous sinus, gasserian ganglion,and trigeminal nerve. Patients who havetumor-related trigeminal neuralgia usu-ally experience progressive or continu-

ous pain, although bouts of intensifica-tion may occur. In contrast, patientshaving idiopathic trigeminal neuralgiaare afflicted by short attacks of severepain with intervals of painless periods.Cranial neuralgias can also be caused byneurofibromatosis type II. Glossopha-ryngeal neuralgias cause pain over the

FIGURE 5-9 A, B, Preoperative sagittal T1-weighted imaging (T1WI) with contrast and FLAIR showingan intraventricular mass (star) with secondary Chiari I malformation (arrowhead) andpartial empty sellar (block arrow). C, Postoperative T1WI sagittal contrast study with

significant improvement of tonsillar herniation and partial empty sellar. Positional headaches completelyresolved after surgery.

Case 5-1A 38-year-old man presented for evaluation of positional headaches, provoked by lookingupward and coughing. The pain was a disabling headache associated with photophobia,sonophobia, and nausea without vomiting and had been progressive over the past year. Thepain was worse on awakening and occipital in location. When he looked upward, the pain wasimmediate and caused him to drop to his knees. Laughing, sneezing, and straining alsoaggravated his headache. No visual symptoms were noted. The patient also reported a daily low-grade headache for which he took six tablets of acetaminophen plus aspirin plus caffeine a day.Complicating the history was a diagnosis of a “benign” intraventricular tumor that had beendiagnosed 30 years earlier but had never been biopsied or treated. Serial MRIs in the past hadbeen stable. Neurologic examination was essentially normal except for diffuse hyperreflexia.

MRI of the brain showed a large heterogenous mass within the lateral ventricle measuring5.2 cm � 6 cm � 4.3 cm. Minimal progression had occurred when compared with the study done5 years earlier. Evidence of a partially empty sella and significant Chiari I malformation measuring15 mm was present but had not been discernible on the previous MRI. The moderatehydrocephalus was not associated with transependymal flow.

The diagnosis was (1) intraventricular ganglioma causing a secondary Chiari I malformation,(2) analgesic rebound headache, and (3) positional headache secondary to Chiari I malformation.

After subtotal resection of an intraventricular ganglioglioma, the headache completelyresolved. Postoperative MRI of the brain confirmed postoperative changes, resolution of thetonsillar herniation, and improvement of the empty sella (Figure 5-9).

Comment. This is a case of acquired secondary Chiari I malformation. The most common causeof secondary cough headaches is a Chiari I malformation. Sagittal T1WI is recommended inpatients with exertional coughing, sneezing, and laughing headaches.

113


ninth cranial nerve distribution, whichmay be lancinating in nature. Pain in thethroat, tonsillar region, posterior third ofthe tongue, larynx, and nasopharynx isquite common. Secondary causes in-clude leptomeningeal metastases ormasses in or around the jugular fora-men. In all patients with cranial neural-gias, standard imaging sequences are TI-WIs with and without contrast with thinslices through the skull base and thin-slice T2WI through the posterior fossa

for the evaluation of aberrant vascula-ture. Thin slices, 2 mm or less, throughthe posterior fossa will allow precise im-aging of the exiting cranial nerves aswell as adjacent vessels. Leptomenin-geal metastasis is also a common causefor cranial neuralgias as well as head-aches. It is best seen with magnetizationtransfer or postcontrast T1WIs. Postcon-trast FLAIR images are also being usedfor the evaluation of leptomeningeal dis-ease (Mechtler, 2007) (Figure 5-10).

FIGURE 5-10 A 35-year-old patient with left-sided trigeminal neuralgia that is becomingmore frequent and is associated with continuous paresthesias in themaxillary and ophthalmic branch of cranial nerve V. A, B, T2-weighted

images (T2WIs) show a relative hypointense extraaxial mass within the Meckel cave andcerebellopontine angle on the left (arrows). C, D, T1WI contrast study showshomogeneous enhancement (arrows). Imaging and pathology were consistent withmeningioma. The diagnosis was secondary trigeminal neuralgia.

‹ HEADACHES

114


CONCLUSIONIn 2006, the United Council of Neuro-logic Subspecialties (UCNS) adopteda neuroimaging core curriculum andexamination to prepare neurologistsfor the independent practice of neuro-imaging as a subspecialty of neurol-ogy. The primary purpose of the UCNSis to provide for accreditation and cer-tification with the goal of enhancing

the quality of training in neurologicsubspecialties, such as headaches andneuroimaging, and improve quality ofpatient care. Headache specialists andneurologists now have a unique op-portunity to be certified in both sub-specialties and advance the diagno-sis, treatment, and research of themost common ailment in society, head-aches.

REFERENCES

Alper F, Kantarci M, Dane S, et al. Importance of anatomical asymmetries of transversesinuses: an MR venographic study. Cerebrovascular Dis 2004;18(3):236–239.

Armao D, Castillo M, Chen H, Kwock L. Colloid cyst of the third ventricle: imaging-pathologic correlation. AJNR Am J Neuroradiol 2000;21(8):1470–1477.

Arnett BC. Tonsillar ectopia and headaches. Neurol Clin 2004;22(1):229–236.

Bakshi R, Shaikh ZA, Kamran S, Kinkel PR. MRI findings in 32 consecutive lipomas usingconventional and advanced sequences. J Neuroimaging 1999;9(3):134–140.

Binder DK, Horton JC, Lawton MT, McDermott MW. Idiopathic intracranial hypertension.Neurosurgery 2004;54(3):538–551.

Brenner DJ, Hall EJ. Computed tomography—an increasing source of radiation exposure.N Engl J Med 2007;357(22):2277–2284.

Broome DR, Girguis MS, Baron PW, et al. Gadodiamide-associated nephrogenic systemicfibrosis: why radiologists should be concerned. AJR Am J Roentgenol 2007;188(2):586–592.

Cady RK, Dodick DW, Levine HL, et al. Sinus headache: a neurology, otolaryngology,allergy, and primary care consensus on diagnosis and treatment. Mayo Clin Proc 2005;80(7):908–916.

Castillo M, Morrison T, Shaw JA, Bouldin TW. MR imaging and histologic features ofcapillary telangiectasia of the basal ganglia. AJNR Am J Neuroradiol 2001;22(8):1553–1555.

Cumurciuc R, Crassard I, Sarov M, et al. Headache as the only neurological sign ofcerebral venous thrombosis: a series of 17 cases. J Neurol Neurosurg Psychiatry2005;76(8):1084–1087.

Epelman M, Daneman A, Blaser SI, et al. Differential diagnosis of intracranial cysticlesion at head US: correlation with CT and MRI. Radiographics 2006;26(1):173–196.

Evans RW, Rozen TD, Mechtler LL. Neuroimaging and other diagnostic testing inheadache. In: Silberstein SD, Lipton RB, Dodick DW, editors. Wolff’s headache and otherhead pain. 8th ed. New York: Oxford University Press, 2007.

Farb RI, Forghani R, Lee SK, et al. The venous distention sign: a diagnostic sign ofintracranial hypotension at MR imaging of the brain. AJNR Am J Neuroradiol 2007;28(8):1489–1493.

Friedman DI. Pseudotumor cerebri. Neurol Clin 2004;22(1):99–131, vi.

115


Headache Classification Subcommittee of the International Headache Society. Theinternational classification of headache disorders: 2nd edition. Cephalalgia2004;24(suppl 1):9–160.

Hellwig D, Bauer BL, Shulte M, et al. Neuroendoscopic treatment for colloid cysts of thethird ventricle: the experience of a decade. Neurosurgery 2003;52(3):525–533.

Hofkes SK, Iskandar BJ, Turski PA, et al. Differentiation between symptomatic Chiari Imalformation and asymptomatic tonsilar ectopia by using cerebrospinal fluid flowimaging: initial estimate of imaging accuracy. Radiology 2007;245(2):532–540.

Horton SC, Bunch TJ. Patent foramen ovale and stroke [published erratum appears inMayo Clin Proc 2004;79(2):279]. Mayo Clin Proc 2004;79(1):79–88.

Idbaih A, Boukobza M, Crassard I. MRI of clot in cerebral venous thrombosis: highdiagnostic value of susceptibility-weighted images. Stroke 2006;37(4):991–995.

Kan P, Stevens EA, Couldwell WT. Incidental giant arachnoid granulation. AJNR Am JNeuroradiol 2006;27(7):1491–1492.

Kaufmann P, Shungu DC, Sano MC, et al. Cerebral lactic acidosis correlated withneurological impairment in MELAS. Neurology 2004;62(8):1297–1302.

Kim BS. Incidental findings on pediatric MRI images of the brain. AJNR Am J Neuroradiol2002;23(10):1674–1677.

Kruit MC, Launer LJ, Ferrari MD, van Buchem MA. Brain stem and cerebellarhyperintense lesions in migraine. Stroke 2006;37(4):1109–1112.

Kruit MC, van Buchem MA, Hofman PA, et al. Migraine as a risk factor for subclinicalbrain lesions. JAMA 2004;291(4):427–434.

Leach JL, Fortuna RB, Jones BV, Gaskill-Shipley MF. Imaging of cerebral venousthrombosis: current techniques, spectrum of findings, and diagnostic pitfalls.Radiographics 2006;26(suppl 1):19–41.

Lewis DW, Ashwal S, Dahl G, et al. Practice parameter: evaluation of children andadolescents with recurrent headaches: report of the Quality Standards Subcommittee ofthe American Academy of Neurology and the Practice Committee of the ChildNeurology Society. Neurology 2002;59(4):490–498.

Markus HS, Martin RJ, Simpson MA, et al. Diagnostic strategies in CADASIL. Neurology2002;59(8):1134–1138.

Mazzotta G, Floridi F, Mattioni A, et al. The role of neuroimaging in the diagnosis ofheadache in childhood and adolescence: a multicentre study. Neurol Sci 2004;25(suppl3):265–266.

Mechtler L. Role of neuroimaging in our understanding of the pathogenesis of primaryheadaches. Curr Pain Headache Rep 2004;8(5):404–409.

Mechtler LL. Pain due to tumors of the skull base. In: de Leon-Casasola OA, ed. Cancerpain: pharmacologic, interventional, and palliative approaches. Philadelphia: Saunders,2007:55–68.

Mechtler LL, Stiles MA. Secondary headaches. In: Silberstein SD, Stiles MA, Young WB,editors. Atlas of migraine and other headaches. 2nd ed. Boca Raton, FL: Taylor & Francis,2005:99–133.

Medina J, Pinter J, Zurakowski D, et al. Children with headache: clinical predictors ofsurgical space-occupying lesions and the role of neuroimaging. Radiology 1997;202:819.

Mokri B. Low cerebrospinal fluid pressure syndromes. Neurol Clin 2004;22(1):55–74, vi.

‹ HEADACHES

116


Moody MW, Chi DH, Mason JC, et al. Tornwaldt’s cyst: incidence and a case report[published erratum appears in Ear Nose Throat J 2007;86(3):129]. Ear Nose Throat J 2007;86(1):45–47, 52.

Osborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imagingapproach. Radiology 2006;239(3):650–664.

Pesa J, Lage MJ. The medical costs of migraine and comorbid anxiety and depression.Headache 2004;44(6):562–570.

Pu Y, Mahankali S, Hou J, et al. High prevalence of pineal cysts in healthy adultsdemonstrated by high-resolution, noncontrast brain MR imaging. AJNR Am JNeuroradiol 2007;28(9):1706–1709.

Quality Standards Subcommittee of the American Academy of Neurology. Practiceparameter: the utility of neuroimaging in the evaluation of headache in patients withnormal neurologic examinations (summary statement). Report of the Quality StandardsSubcommittee of the American Academy of Neurology. Neurology 1994;44:1353–1354.

Rocca MA, Ceccarelli A, Falini A, et al. Brain gray matter changes in migraine patientswith T2-visible lesions: a 3-T MRI study. Stroke 2006;37(7):1765–1770.

Schievink WI. Spontaneous spinal cerebrospinal fluid leaks and intracranial hypotension.JAMA 2006;295(19):2286–2296.

Sempere AP, Porta-Etessam J, Medrano V, et al. Neuroimaging in the evaluation ofpatients with non-acute headache. Cephalalgia 2005;25(1):30–35.

Silberstein SD. Practice parameter: evidence-based guidelines for migraine headache (anevidence-based review): report of the Quality Standards Subcommittee of the AmericanAcademy of Neurology [published erratum appears in Neurology 2000;56(1):142].Neurology 2000;26;55(6):754–762.

Silberstein SD. Headaches due to nasal and paranasal sinus disease. Neurol Clin 2004;22(1):1–19, v.

Spencer MP, Moehring MA, Jesurum J, et at. Power m-mode transcranial Doppler fordiagnosis of patent foramen ovale and assessing transcatheter closure. J Neuroimaging2004;14(4):342–349.

Swartz RH, Kern RZ. Migraine is associated with magnetic resonance imaging whitematter abnormalities: a meta-analysis. Arch Neurol 2004;61(9):1366–1368.

Vernooij MW, Ikram MA, Tanghe HL. Incidental findings on brain MRI in the generalpopulation. N Engl J Med 2007;357(18);1821–1828.

Wang HZ, Simonson TM, Greco WR, Yuh WT. Brain MRI in the evaluation of chronicheadache in patients without other neurological symptoms. Acad Radiol 2001;8(5):405–408.

Welch KM, Nagesh V, Aurora SK, Gelman N. Periaqueductal gray matter dysfunction inmigraine: cause or the burden of illness? Headache 2001;41(7):629–637.

117


neuroimaging of headaches

Documents