effects of temperature on human compound action potentials

Journal of Neurology, Neurosurgery, and Psychiatry, 1981, 44, 407-413

The effects of temperature on human compoundaction potentialsC F BOLTON, G M SAWA, AND K CARTER

From the Department of Clinical Neurological Sciences, Victoria Hospital,University of Western Ontario, London, Ontario, Canada

SUMMARY The upper limbs of 10 healthy subjects were cooled and then warmed over physi-ological temperature ranges. The compound action potentials of median digital nerves, mediansensory nerve at the wrist, radial sensory nerve at the wrist, and median thenar muscle, allshowed progressive reduction in latency, amplitude, duration and area during rising temperature.Our studies suggest that the sensory compound action potential changes occur predominantlybecause of the summated effects of reduction in the duration of the action potentials of singlemyelinated fibres, although disproportionate increase in the conduction velocity of larger my-elinated fibres also plays a role.

A decrease in the conduction velocity and an in-crease in the distal latency of human peripheralnerves are well documented electrophysiologicalsigns of neuropathy. However, when axonaldegeneration predominates and segmental demye-lination is minimal, these values are relatively un-altered, and the main effect is reduction in sensorynerve' and muscle2 compound action potential(CAP) amplitude. Unfortunately, many factors,both technical and physiological, affect this ampli-tude. As a result, the coefficient of variation (thestandard deviation as a percentage of the mean)of the CAP amplitude in control groups ap-proaches 60%.3 Even serial tests in a single,control person show a variation of 20% to 30%for sensory CAPs using needle electrodes,4 and15% using surface electrodes (Bolton, CF; un-published data).Many of the factors contributing to CAP

amplitude variation in healthy persons have beendefined for needle and surface electrodes.5 6 Limbtemperature may be an important variable thatneeds further definition. In two previous investiga-tions of the effect of temperature on CAP ampli-

Presented in part at the XlVth Canadian Congress of NeurologicalSciences, Halifax, Novia Scotia, 13-16, June 1979.

Address for reprint requests: Dr CF Bolton,Victoria Hospital Corpora-tion, South St Campus, 375 South St, X Middlesex, London, OntarioN6A 4G5, Canada.

Accepted 4 February 1981

tude, needle electrodes were used for recording,and there was concern that the equivocal resultsmay have been due to inadvertent movement ofthe tip of the needle during the experiment.5 7

Surface electrodes, although recording lowervoltage potentials, remain at an almost constantdistance from the nerve, tending to eliminate thissource of error. We therefore used surface elec-trodes in studying the effect of altering limb tem-perature, within physiological ranges, on thelatency, amplitude, duration, and area of the CAP.Antidromic and orthodromic radial sensory con-duction studies were performed in 10 healthysubjects.

Methods

The subjects were 23 to 31 years old, six males andfour females. In each subject the temperature of theright hand and forearm was lowered by the applica-tion of icepacks. All subsequent studies were per-formed at 15 minute intervals while the limb graduallywarmed over approximately two hours. In some sub-jects, warming was enhanced by the breeze from anelectric hair-dryer. Cutaneous surface temperaturewas monitored at the proximal part of the seconddigit, centre of the palm and the mid-flexor surfaceof the forearm immediately after each nerve conduc-tion study.One pair of recording and reference Beckman

miniature electrodes were placed 3 cm apart over thesuperficial radial nerve at the wrist, and a second pairwas placed over the median nerve at the wrist. Record-

407

Protected by copyright.

on Novem

ber 16, 2021 by guest.http://jnnp.bm

j.com/

J Neurol N

eurosurg Psychiatry: first published as 10.1136/jnnp.44.5.407 on 1 M

ay 1981. Dow

nloaded from

http://jnnp.bmj.com/

C F Bolton, G M Sawa, and K Carte)

ing and reference Teca ring electrodes were placed3 cm apart on the second digit, the recording electrodeoverlying the proximal crease. At each nerve conduc-tion study, the radial nerve was stimulated in theforearm through a Disa stimulating probe, electrodes2-5 cm apart. The pulses were 01 ms in duration andof supramaximal voltage. In antidromic median sen-

sory conduction the nerve was sitimulated at the wrist,just lateral to the recording electrodes, then at theelbow, and finally at the upper arm. In orthodromicmedian sensory conduction, the Teca ring electrodeswere used for stimulation instead of recording. Formedian motor conduction studies, Beckman miniaturerecording and reference electrodes were placed atstandard positions over the thenar eminence andproximal thumb. The thenar CAP was recordedsimultaneously with the antidromic sensory CAP on aseparate oscill'oscope channel from stimuli deliveredto the median nerve at wrist, elbow and upper arm.The sites of stimulating and recording electrodes wereconstant during the experiment. Resistance of theelectrodes was measured at intervals during the experi-menit. Teca ring electrodes had to be reapplied attimes because the electrode paste dried; this manoeuvreprevented electrode resistance from rising. Tissueresistance was not measured, but Ludin and Beyeler7sh(owed tissue resistance was unchanged during asimilar experiment.

Polaroid pictures of the oscilloscope traces weremagnified five itimes for accurate measurement.Latency was measured as the time from stimulusartifact to beginning of the negative phase of theCAP, and duration was the time of the negativephase. Because of the possible interference of the latepositive phase of the antidromic sensory CAP bymuscle CAP, the peak to peak amplitude and thetotal duration -of the CAP were not measured. Therise time was not studied since it was often too beiefto be measured accurately. Amplitude was measuredas the height of the negative phase. The statisticalcalculations were performed on a Tektronix 451 com-puter, using Plot 50 statistics, volume 1, software. Thearea of the negative phase was computed using theTektronix computer, oscilloscope and graphics tablet.Proximal and distal unipolar, and bipolar recordingarrangements were set up5 in two subjects. Supra-maximal stimuli were delivered to the median nerveat wrist. CAPs were recorded via Teca ring electrodes,pliaced 3 0 cm apart on the third digit, and proximalelectrode overlying the proximal crease. The referenceelectrode for the monopolar recordings was a silverStrip placed along the length of the fifth digit andhypothenar eminence. By this method, it was possibleto compare CAPs recorded from proximal and distalmonopolar, and bipolar recording arrangements usingthe same stimuli.

Equzipment used included a Disa 14E1 1 stimulator;low noise integrated circuit amplifiers with high inputimpedance and a frequency range set of 20 to5,000 Hz; and a Hewlett-Packard 141B oscilloscope.With tl ds equipment and technique, all CAPs were

of large enough voltage that averaging wasunnecessary.

Results

The mean range of cutaneous temperature riseduring warming was less proximally than distally,the expected physiological temperature gradient.However, there was considerable variation be-tween individuals in the range and rate of tem-perature rise that was induced by this experiment(table 1), likely reflecting differences in physio-logical adaptation to cooling and warming.We found strong correlations between the vari-

ous nerve conduction measurements and each ofthe three sites of cutaneous temperature monitor-ing, but the best correlations were with thecutaneous temperature site that was nearest to thelength of nerve over which conduction velocitywas measured (table 2), or to the recordingelectrode from which the CAP was recorded andits various measurements determined (table 3).The change of the nerve conduction measurementswith increasing temperature varied considerablybetween subjects, but at least one subject showedstatistically significant changes for each measure-ment (example in fig 1) the only exceptions beingthe CAP amplitudes of the median sensory nerveat the wrist (table 3).

Conduction velocity rose at a mean rate ofbetween 1b64 to 2-31 m/OC for the motor andsensory nerves (table 2).

Table I Cutaneous temperature rise during warmingof upper limb in 10 healthy subjects

Mean low(range) °C

Finger 22-5 (19-7-27-0)Palm 25*3 (22-8-28-0)Forearm 26-9 (251-29 5)

Mean high(range) °C

33-6 (30 5-36 2)32-1 (29 5-34 5)30 9 (28-3-34 0)

Meandiference °C

11-16-84 0

Table 2 Absolute change of conduction velocitieswith cutaneous temperature

b (m/s/°C) r2

Median sensoryantidromicElbow-wrist* +1 64 (046-.374) 0 34 (0-05-063)Wrist-digitt +2-31 (1-21-3-41) 0 76 (050-100)

Median sensoryorthodromic

Digit-wristt +2 18 (0 68-3 68) 0-69 (0 40-0 98)Median motororthodromicElbow-wrist* +1 47 (0 00-3 66) 0-45 (0-21-0-69)

Linear regression values (mean (range)) in 10 healthy subjects; b-baluein equation y =a+bx; r2-coefficient of determination; *-correlatedwith forearm temp; t-with palm temp.

408


on Novem


j.com/

J Neurol N


ay 1981. Dow

nloaded from


The effects of temperature on human compound action potentials

90-

80

, 70-

a 60-

< 50-

40-

3020 22 24Temperature IC

Fig I The relationship betwCAP of the median digital ne

and rising temperature of thethat digit in a healthy subjeci

The CAP distal latencnerves (antidromic) and that the wrist (orthodromic) s

was similar, but not identiwhen the latency of thedigital nerves was correlatture, instead of digit tentable 3, the rate of decreidentical to that of the CA]nerve at the wrist. Thus,latency in both antidroimedian sensory conductioifirming Buchthal and RoseThis result is to be expecdistances between stimuelectrodes are the same fc

they are interchanged for the respective antidromicy = 185 80 - 4 92x and orthodromic conduction.r2= 095 The CAP distal latencies of the radial sensory

nerve at the wrist (antidromic) and the thenarmuscle (orthodromic) decreased to a similardegree, and both were approximately twice thedegree of decrease of orthodromic median nerveconduction. The reason for these observations isnot apparent. The greater decrease of thenarmuscle CAP latency, compared to median digitalCAP latency, was not due to the negative phaseof the median digital nerve CAP being interferedwith by muscle CAP. We would have observedsuch an interference, since we recorded both

26 28 30 32 CAPs simultaneously on separate oscilloscopechannels, using the same stimulus.

'een the amplitude of the The CAP amplitudes of the median digital?irves of the index finger nerves and the radial sensory nerve at the wrist?cutaneous surface of both fell markedly, but the fall was much less fort. CAP amplitude of the median sensory nerve at the

wrist and thenar muscle. The CAP durationchange was greatest for the thenar muscle, and

-ies of median digital much less for the three sensory nerves.ie median sensory nerve Since the combined effect of increase in tem-;howed a decrease which perature was a reduction in both CAP amplitudeical (table 3). However, and duration, changes in CAP area were marked.CAP of the median The CAP area decreased approximately 10%/°C

ted with palm tempera- for radial sensory nerve, 5% for median digitalnperature as shown in nerves, and 3% for the median sensory nerve atase of the latency was the wrist and median thenar muscle (table 3).P of the median sensory In antidromic sensory conduction, the CAPs ofthe absolute values for median digital nerves were recorded on stimulationmic and orthodromic of the median nerve at the wrist, elbow and uppern were the same, con- arm (fig 2). (In orthodromic median sensory con-nfalk's5 earlier finding. duction, CAPs cannot usually be recordedted since the sites and proximal to the wrist using surface electrodes,lating and recording without utilising averaging techniques. In radial:r each subject, except nerve antidromic sensory conduction, we arbi-

Table 3 Change (mean range) of CAP measurements with cutaneous temperature

CAP Distal latency Amplitude Duration Area

b(ms/°C) r2 b(uV/°C) r2 b(ms/°C) r2 b(%/°C) r2

Median digital -0-07 0-84 -1 90 0-79 -0-06 0-78 -5-5 0-83nerves+ (0 02-0-16) (0 69-0 99) (0-52-492) (056-1 00) (0-02-0-12) (0 55-1 00) (3 5-10-0) (0-70-096(antidromic)Median sensory -0-11 0-76 -0-04 0-33 -0 05 0-67 -3-1 0-39nerve at wristt (0-05-0 15) (0 50-1 00) (0-00-0 09) (0 08-0 58) (0-014 09) (0-44-0 90) (0 2-7-3) (0-10-068)(orthodromic)Radial sensory -0 21 0-78 -1-76 0-55 -0-10 0-38 -10-78 0-51nerve at wristt (0 10-032) (0-66-090) (0 49-3 03) (0-28-082) (0 00-0-21) (0-14-0-62) (0 1-20 0) (0-02-0-82)(antidromic)

b(m V/C)Median thenar -0-26 0-84 -0-24 0-46 -0-25 0-77 -2-7 0-62musclet (0 08-052) (070-0 98) (0-00-0-55) (0 08-0 84) (0-08-071) (0 62-0 92) (0 2-5-6) (0 35-0 89)

Designations as in table 2; T-Correlated with digit temp.

409


on Novem


j.com/

J Neurol N


ay 1981. Dow

nloaded from


C F Bolton, G M Sawa, and K Carter

0o

-...--220C- 310C

- 5-

l0 /I C

- 10.

(a)

(b)

(c)

I20,V

0cm

Fig 2 The CAPs of median digital nerves from

stimulation at wrist (a), elbow (b) and upper arm (c)at cool and warm finger temperatures. Note thedecrease in the amplitude, duration and area of CAon more proximal stimulation, independent oftemperature, but the further decrease in thesefeatures at higher temperature. An analysis of theresults of this experiment in all 10 subjects is shownin fig 3. (Dots in lower scale are at I ms intervals.)

trarily decided to stimulate at only one site.) TheCAP of median digital nerves normally becomesdispersed, of lower amplitude and greater dur-ation, on more proximal stimulation (fig 2), owingto the differing conduction rates of larger mye-linated fibres. We compared the % change per OCin these CAP measurements with increasingdistance at the three sites of stimulation (fig 3).Area, amplitude and duration all showed a greater% decrease on more proximal stimulation (in thatorder), suggesting that rising temperature causeda relatively greater increase in conduction velocityof larger myelinated fibres, although this relativeincrease was small.The size and shape of the CAP recorded with

bipolar surface electrodes is due partly to the

Wrist Elbow UpperarmI t

Latency

Area

10 20 30 40 50

Fig 3 The relationship between the effects of risingtemperature on median digital nerve CAPmeasurements and increasing distance betweenstimulating and recording electrodes for the 10subjects. %/°C for each measurement was determinedby converting the absolute value of b in the equationy=a+bx for each subject to a % and thencalculating the mean % for the 10 subjects;I designate sites of stimulation of median nerve.

voltage difference between reference and recordingelectrodes induced by the successive arrival timesof the CAP at each of these electrodes.5 To deter-mine if the greater rate of conduction of the largermyelinated fibres induced by the temperature riseaffected this voltage difference, we recorded theCAP of median digital nerves on antidromicstimulation by both bipolar and monopolar tech-niques in two subjects. The CAP from eachtechnique showed similar changes in size andshape with increase in temperature (fig 4), showingthat latency changes between the electrodes in-duced by the increased conduction rate of largermyelinated fibres was insignificant.

Discussion

Our study has shown that the various CAPmeasurements are remarkably sensitive to tem-perature change, and such change must be takeninto account if these measurements are to beaccurately interpreted in clinical electrophysiology.However, we emphasise that we documented onlytemperature effects within physiological ranges inthe upper limb of healthy young adults; theseresults may not apply to nerves of older persons,nor to diseased nerve.

410

- 15I_l


on Novem


j.com/

J Neurol N


ay 1981. Dow

nloaded from



g=S 9^<~~~218 OC

2ms

Fig 4 Recording of monopolar and bipolar actionpotentials in one subject at cool and warmtemperatures. A t each temperature, the upper traceshows the bipolar, the middle trace the proximalmonopolar, and the lower trace the distal monopolar,action potentials; all three action potentials wererecorded at the middle finger from the same

supramaximal stimulus to the median nerve at thewrist (see Methods). Note the reductions in latency,amplitude and duration are similar at highertemperature for bipolar and monopolar recordings.

We monitored temperature from the cutaneoussurface. The superficial radial and median digitalnerves lie superficial to the deep fascia, close tothe cutaneous surface. Temperature at this site isgoverned by the sweat and blood flow regulatedby cutaneous sympathetic fibres.8 As a result, thesurface cutaneous temperature is only approxi-mately 1°C less than the tissue temperature near

these nerves.49 However, the median nerveproximal to the digits lies beneath the deep fasciaand, in this part of its course, probably does notfollow as closely the cutaneous surface tempera-ture. Nonetheless, there was, in individual sub-jects, an excellent correlation between cutaneoussurface temperature at each of the three sites andthe various nerve conduction measurements. Theexcellent correlation included conduction velocitiesfrom the deeper segments of the median nerve,our results being similar to other studies in whichsubcutaneous or intramuscular temperature was

monitored.5 10-12 Moreover, we found that thedistal latency of the thenar CAP changed026 ms/°C, a rate similar to that recorded byCarpendale, who recorded temperature fromwithin the thenar muscle.'3

Striking changes in CAP latency, amplitude,duration and area occurred, all of these valuesshowing a negative linear correlation with tem-perature, that is all decreased as temperature rose.The magnitude of these changes varied consider-ably between individuals. However, the correlationfor each of these values was statistically significantin at least one subject, the only exceptionsbeing the CAP amplitudes of the median sensorynerve at the wrist.The amplitude fall with rise in temperature for

the median sensory nerve at the wrist recordedorthodromically was small, and similar to thatreported by Ludin and Beyeler7 for the tempera-ture range 26-360C. They used needle electrodesfor recording and found a puzzling rise in ampli-tude as temperature increased from 22-260C. Inan earlier study, Buchthal and Rosenfalk5 foundno consistent change in this amplitude, a resultthey attributed to inadvertent movement of theneedle electrode during the experiment. The some-what equivocal change in the amplitude of themedian CAP at the wrist recorded orthodromicallycontrasts with the marked fall in CAP amplitudein both the median digital nerves and the radialsensory nerve at the wrist recorded antidromically.Hlavova et all4 had previously noted this contrast-ing result between median nerve orthodromic andantidromic conduction. The reasons are open tospeculation: (1) there may be differences betweenorthodromic and antidromic conduction that haveyet to be defined, (2) the nerves of the cutaneousand subcutaneous tissue may be particularly sensi-tive to temperature change. They lie beneath therecording electrodes and may have been activatedin median and radial nerve antidromic conductionand such activation may have contributed to theCAP, whereas nerves of this tissue beneath theelectrode at the wrist in orthodromic median con-duction arise from the palmar cutaneous branchof the median nerve and were presumably notactivated, (3) the vasodilating response withwarming occurs predominantly in cutaneous andsubcutaneous tissues superficial to the deep fascia.The median digital and superficial radial nerves arein this superficial location and would be more sub-ject to such a response than the median nerve atthe wrist which lies beneath the deep fascia. Thevasodilating response would increase vascular andinterstitial fluid, tending to move the recordingelectrode further from the nerve; it might alsoincrease the volume within the endoneural space,tending to decrease the density of nerve fibreswithin this space. Greater distance of recordingelectrode to nerve, and decreased density of nerve

411


on Novem


j.com/

J Neurol N


ay 1981. Dow

nloaded from


412

fibres, are both known to decrease the amplitudeof CAPs.5 'o The relevance of these various factorsrequires further investigation.The results of animal experiments (if they apply

to man) suggest the main mechanisms of thesensory CAP changes. Although Tasaki andFugital' reported a rise of the action potential ofsingle axons of the toad recorded extracellularly,the weight of evidence favours a fall in amplitudewith increase in temperature. Such a fall occurredin the intracellularly recorded action potential ofthe squid axon'7 18 and in the extracellularly re-

corded action potential of frog myelinated fibres'9and single myelinated fibre of rat ventral root.20However, a decrease in the duration of these actionpotentials has been a more consistent observationand is more marked than the fall in amplitude(fig 5). Temperature also affects the rate of con-

duction of myelinated fibres, the larger myelinatedfibres of the cat cervical vagus nerve conductingmore rapidly with increase in temperature thanthe smaller diameter fibres.2' A total conductionblock will occur in myelinated fibres only at very

high or very low temperature.21-23 Thus, humanCAP changes during physiological temperaturerise probably occur by two main mechanisms: (1)the action potential of a single myelinated nerve

fibre is only mildly reduced in amplitude but con-

siderably reduced in duration, the summated effecton the CAP from a nerve trunk being a reduction

T0o0Gv

0

Time (ms)0 *5

Fig 5 Action potentials recorded from singlemyelinated fibres of rat ventral root at 37'C (a), at31°C (b), and at 37°C after exposure to scorpionvenom for 30 s (c). Note marked reduction ofduration, and mild reduction in amplitude withhigher temperature (figure taken from Bostock H,Sherratt RM, and Sears, TA: Overcoming conductionfailure in demyelinated nerve fibres by prolongedaction potentials. Reprinted by permission fromNature, Vol. 274, No. 5669, 385-7, Copyright (©o)1978 Macmillan Journals Limited).

C F Bolton, G M Sawa, and K Carter

in both amplitude and duration; and (2) thelarger diameter myelinated fibres conduct at adisproportionately greater rate, causing a dis-persion of the CAP, that is a further reduction inamplitude but an increase in duration. The firstmechanism is likely to be the predominant one. Itovercomes the second mechanism, resulting inan overall decrease in duration of the CAP. Thesecond mechanism can be examined in isolationby noting the effect on the CAP of stimulatingthe nerve at increasing distances from the record-ing electrodes, since, according to the all or nonelaw, the action potential of single myelinatedfibres induced in this way should remain constantin size and shape when the recording electrode isstationary. Without temperature change, thisresults in a progressive dispersion of the CAP, areduction in the amplitude and an increase in theduration of the CAP, due to greater rates of con-duction by larger myelinated fibres (fig 2); thereduction in area and relatively less increase induration likely occurs because the CAP becomesso dispersed that electrical activity from some ofthe fibres is unrecordable. With rising tempera-ture, there was a further reduction in area, ampli-tude and, to a lesser extent, duration on moreproximal stimulation (figs 2, 4), indicating morerapid conduction in larger myelinated fibres rela-tive to smaller myelinated fibres tended to dis-perse the CAP. However, this effect was mild,suggesting again that the effect of temperature onthe action potential of single myelinated fibres ispredominant, the summated effect strongly influ-encing CAP area, amplitude and duration.

Interpretation of the changes in thenar muscleCAP are particularly complicated and involve notonly a consideration of neural events, but ofevents at the neuromuscular junction and musclemembrane; such considerations are beyond thescope of this discussion. Briefly, however, a mildfall in the amplitude of the thenar muscle CAPwith rising temperature occurred in a few subjectsin our study. Ricker et al24 showed a greater fall,which they attributed to changes in muscle cellmembrane. They also showed that the twitch forceincreased, presumably a temperature effect on thecontractile apparatus. These investigators notedmuscle CAP duration decreased, but did notquantify the decrease. We found that durationchanged more consistently than amplitude, at-025 ms/°C.

We thank Miss Betsy Toth, secretary, for typingthe manuscript, Mr Mike Clark, electronicstechnician, for constructing EMG equipment, and


on Novem


j.com/

J Neurol N


ay 1981. Dow

nloaded from



personnel in the Department for volunteering ashealthy subjects.

References

1 Buchthal F, Behse F. Peroneal muscular atrophy(PMA) and related disorders. 1. Clinical mani-festations as related to biop3y findings, nerve con-duction and electromyography. Brain 1977; 100:41-66.

2 Bolton CF, Gilbert JJ, Girvin JP, Hahn AF.Nerve and muscle biopsy. Correlation of electro-physiology and morphology in polyneuropathy.Neurology (Minneap) 1979; 28:354-62.

3 Bolton CF. Electrophysiological changes in uremicneuropathy following successful renal transplanta-tion. Neurology (Minneap) 1976; 26:152-61.

4 Rosenfalk A. Early recognition of nerve disordersby near-nerve recording of sensory action poten-tials. Muscle and Nerve 1978; 1:360-7.

5 Buchthal F, Rosenfalk A. Evoked action poten-tials and conduction velocity in human sensorynerves. Brain Res 1966; 3:1-122.

6 Bolton CF, Carter K. Human sensory nerve com-

pound action potential amplitude. Variation withsex and finger circumference. J Neurol NeurosurgPsychiatry (in press).

7 Ludin HP, Beyeler F. Temperature dependenceof normal sensory nerve action potentials. JNeurol 1977; 216:173-80.

8 Valbo AB, Hagbarth HE, Torebjork HE, WallinBG. Somatosensory, proprioceptive, and sympath-etic activity in human peripheral nerves. PhysiolRev 1979; 59:919-57.

9 Abramson DI, Luke SWC, Rickert BL, Talso JF,Lee SW. Latency changes in distal median nerveproduced by alterations in ambient temperatures.J Appl Physiol 1%96; 27:795-803.

10 DeJesus PV, Hansmanowa-Petruscewicz I, BarchiRL. The effect of cold on nerve conduction ofhuman slow and fast nerve fibers. Neurology(Minneap), 1973; 23:1182-9.

11 Lowitzsch K, Hopf HC Galland J. Changes ofsensory conduction velocity and refractory periodswith decreasing tissue temperature in man. JNeurol 1977; 216:181-8.

12 Henriksen JD. Conduction velocity of motornerves in normal subjects and in patients with

neuromuscular disorders. Thesis. Minneapolis,1956.

13 Carpendale MTF. Conduction time in the ter-minal portion of the motor fibers of the ulnar,median and peroneal nerves in healthy subjectsand in patients with neuropathy. Thesis. Univer-sity of Minnesota Graduate School, 1956.

14 Hlavova A, Abramson DI, Rickert BL, Talso JF.Temperature effects on duration and amplitudeof distal median nerve action potential. J ApplPhysiol 1970; 28:808-12.

15 Lambert EH, Dyck PJ. Compound action poten-tials of sural nerve in vitro in peripheral neur-opathy. In: Dyck, PJ, Thomas PK, Lambert EH,eds. Peripheral Neuropathy. Philadelphia: WBSaunders Co, 1975; I:241.

16 Tasaki I, Fugita M. Action currents of singlenerve fibers as modified by temperature changes.J Neurophysiol 1948; 11:311-5.

17 Hodgkin AL, Katz B. The effect of temperaturein the electrical activity of the giant axon of thesquid. J Physiol (Lond) 1949; 109:240-9.

18 Huxley AF. Ion movements during nerve activity.Ann NY Acad Sci, 1959; 81:221-46.

19 Schaepfle GM, Erlanger J. The action of tem-perature on the excitability, spike height andconfiguration, and the refractory period observedin the responses of single medullated nerve fibers.Am J Physiol 1941; 134:694-704.

20 Bostock H, Sherratt RM, Sears TA. Overcomingconduction failure in demyelinated nerve fibersby prolonging action potentials. Nature 1978;274:385-7.

21 Li CL, Mathews G, Bok FA. Effect of tem-perature on the response of cervical vagus nerve.Exp Neurol 1977; 55:709-18.

22 Rasminsky M. The effects of temperature on con-duction in demyelinated single nerve fibers. ArchNeurol 1973; 28:287-92.

23 Low PA, McLeod JG. Refractory period, con-duction of trains of impulses, and effect of tem-perature on conduction in chronic hypertrophicneuropathy: electrophysiological studies on theTrembler mouse. J Neurol Neurasurg Psychiatry1977; 40:434-47.

24 Ricker K, Hertel G, Stadieck G. Increased vol-tage of the muscle action potential of normal sub-jects after cooling. J Neurol 1977; 216:33-8.

413


on Novem


j.com/

J Neurol N


ay 1981. Dow

nloaded from


effects of temperature on human compound action potentials

Documents