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Motor Nerve in the Guillain-Barre Syndrome

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Motor Nerve in the Guillain-Barre Syndrome J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.39.6.538 on 1 June 1976. Downloaded from Journal ofNeurology, Neurosurgery, andPsychiatry, 1976, 39, 538-544 Conduction velocity in the proximal segments of a motor nerve in the Guillain-Barre syndrome DAVID KING AND PETER ASHBY From the EMG Department, Toronto Western Hospital, Toronto, Ontario, Canada SYNOPSIS Conduction velocity from spinal cord to axilla (estimated using the F wave) has been compared with conduction velocity from axilla to wrist (measured in the conventional manner) in the motor fibres of the ulnar nerve in 17 control subjects and in 11 patients with the Guillain-Barre syndrome (GBS). In the patients with GBS the conduction velocity was, in general, reduced to a similar extent in both the proximal and the distal portions of the motor fibres, suggesting that the disease process is usually diffuse. In two patients, however, the conduction velocity in the proximal segment was disproportionally reduced and in one of these the conduction in the distal was normal. It is velocity segment concluded that theProtected by copyright. estimation of conduction velocity in the proximal segments of motor nerves may be of value in the assessment of patients with GBS. Patients with the Guillain-Barre syndrome parent until two to three weeks after the onset (GBS) commonly develop a reduction in motor of the syndrome (Peterman et al., 1959; Hum- nerve fibre conduction velocity which helps to phreys, 1964; Kaeser, 1970; Eisen and Hum- differentiate the condition from other types of phreys, 1974). neuromuscular disease (Peterman et al., 1959; In a proportion (10-20%) of patients with Cerra and Johnson, 1961; Lambert and Mul- otherwise typical GBS it is not possible to der, 1964; Isch et al., 1967; Kaeser, 1970; Mc- demonstrate slowing of conduction in the Quillen, 1971; Eisen and Humphreys, 1974). distal segments of motor nerves even at the The reduced conduction velocity can be attri- peak of the neurological deficit (Lambert and buted to an increase in the internodal conduc- Mulder, 1964; McQuillen, 1971; De Jesus, tion time resulting from segmental demyelina- 1974; Eisen and Humphreys, 1974). There are http://jnnp.bmj.com/ tion (Rasminsky and Sears, 1973). several possible explanations for this: Conduction velocity is usually measured in (1) the disease process could be so mild that the most accessible distal segment of motor the conduction velocity of the fastest motor nerves. The slowing of nerve conduction velo- fibres is not depressed below the normal range; city in this segment is usually uniform but may (2) the demyelination could involve pre- be patchy (Bigot and Goulon, 1970; Kaeser, dominantly the roots or proximal portions of 1970), most marked distally (Isch et al., 1967), the spinal nerves where conduction can not be on September 27, 2021 by guest. or most marked at potential sites of nerve measured using conventional techniques compression (Lambert and Mulder, 1964). Al- (Kaeser, 1970; Eisen and Humphreys, 1974); though sometimes present within a few days of (3) the weakness could result from conduc- the onset of symptoms, the characteristic re- tion block (Kaeser, 1970) or axonal disruption duction in conduction velocity may not be ap- (Oppenheimer and Spalding, 1973). The measurement of conduction velocity in the proximal portions of motor nerves would Address for correspondence: Dr. P. Ashby, 25 Leonard Avenue Toronto M5T 2R2, Ontario, Canada. clearly help to distinguish between these (Accepted 20 January 1976.) possibilities. 538 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.39.6.538 on 1 June 1976. Downloaded from MWotor nerve conduction velocity in Guillain-Barre syndrome 539 Kimura (1974) has devised a method of esti- ulnar nerve at the wrist and at the axilla and mating conduction velocity in motor nerve conduction velocity in the fastest motor fibres fibres from the spinal cord to the proximal part calculated in the conventional manner. Supra- of the limb using the F wave. In the present maximal stimuli were then delivered to the ulnar study, the conduction velocities from the nerve at the wrist and at the axilla simultaneously, spinal cord to axilla (estimated with this tech- allowing the compound action potential of the ab- nique) and axilla to wrist (estimated in the ductor digiti minimi generated by the stimulus at usual the wrist, and the F wave generated by the stimu- way) in the motor fibres of the ulnar lus at the axilla to be visualized. When two nerve are compared in normal subjects and in stimuli are delivered simultaneously to the ulnar a group of patients with GBS of varying de- nerve in this way the orthodromic volley resulting grees of severity. It is concluded that the tech- from the axillary stimulus cannot evoke a muscle nique is of value in the assessment of patients action potential as it collides with the antidromic with GBS. Kimura and Butzer (1975) have re- volley generated at the wrist. After checking that cently published the findings of a similar study the orthodromic volley from the proximal site of in patients with mild GBS. stimulation had been successfully blocked, the amplification was increased in order to examine the F waves in more detail. The latency of the METHODS earliest proximally evoked F wave was measured from its onset. The latency axilla-cord-axilla was Studies were carried out on 17 control subjects determined by subtracting the distal latency of the and 11 patients with GBS. The control subjects compound action potential produced by the iso- Protected by copyright. were either normal volunteers (nine) or patients lated axillary stimulus and by subtracting a fur- (eight) referred for electrophysiological examina- ther, arbitrary, 1.0 ms to allow for the reactivation tion for conditions that were unlikely to affect of the anterior horn cells. The distance from the conduction in the upper limbs. proximal point of stimulation to the vertebra pro- The patients with GBS were those who had minens was measured in the manner described attended the electromyographic laboratory in the by Kimura (1974). previous four years. Some patients were examined Comparisons of proximal and distal conduction during the acute phase of the disease and others re- velocities in the normal and patient populations called for examination during convalescence. The were made using Student's t test and the correla- diagnosis of GBS was accepted if the patients tion coefficient. Probabilities of less than 0.5 (two had had the typical onset of progressive weakness, tailed) were considered significant. with areflexia, attributable to a symmetrical poly- neuropathy, accompanied by a raised CSF protein. The patient's clinical condition at the time of the electromyographic examination was graded as RESULTS http://jnnp.bmj.com/ normal', 'mild' (definite neurological deficit but The technique was found to be relatively not hospitalized), 'moderate' (hospitalized but able and to sit or stand), and 'severe' (hospitalized and un- simple studies could usually be completed able to sit or stand or requiring ventilation). within 10 minutes. In normal subjects, the Proximal conduction was determined by the proximally evoked muscle compound action method devised by Kimura (1974). Electrical potential could be readily blocked (Fig. 1), and stimuli generated by a Grass S 88 stimulator were several F waves each having a consistent lat- delivered to the ulnar nerve at the wrist and/or ency obtained (Fig. 2). The estimates of the on September 27, 2021 by guest. axilla through gold plated bipolar surface elec- conduction velocity measured using the F wave trodes 0.5 cm in diameter, 3 cm apart. The com- conformed closely to estimates of conduction pound action potential of the abductor digiti from Erb's point to the axilla obtained in the minimi was recorded with spring clip electrodes conventional manner in subjects in whom this (C. F. Palmer (London) Ltd.), amplified using a Tektronix 2A61 differential amplifier with filter could be carried out. In the patients with GBS, settings 0.6 Hz and 10 kHz, and displayed on a who often had dispersed and irregular com- Tektronix 561A and a Tektronix 564 storage pound muscle action potentials, the F waves oscilloscope. The traces were photographed using could generally be recognized by the character- a Tektronix C 12 Polaroid camera. istic variability of their occurrence and their A supramaximal stimulus was delivered to the constant latency (Fig. 3). J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.39.6.538 on 1 June 1976. Downloaded from 540 David King and Peter Ashby BOTH I, AXILLA J- WRIST \ ms .J i/1 --~ FIG. 1 Extinction of the orthodromic M response by simultaneous stimulation of the ulnar nerve at {2mV2 the wrist and at the axilla in a normal subject. ms Compound action potential recorded with surface electrodes over abductor digiti minimi. The lower FIG. 3 F waves obtained from stimulation of the trace shows the M response obtained by supra- ulnar nerve in the axilla in a patient with the maximal stimulation of the ulnar nerve at the Guillain-Barre syndrome. wrist and the middle trace that obtained by supra- maximal stimulation of the ulnar nerve in the axilla. When both stimuli are delivered simultane- ously (top trace), the antidromic volley generated CONTROL SUBJECTS There was no significantProtected by copyright. at the wrist collides with the orthodromic volley difference between the mean and the originating at the axilla. The longer latency proximal muscle compound action potential is therefore mean distal conduction velocities of the normal abolished. volunteers and the subjects referred for neuro- physiological studies for conditions unlikely to affect conduction in the upper limbs. These data were therefore pooled. In the control sub- jects (Table 1) the mean calculated conduction velocity in the proximal segment, spinal cord TABLE 1 PROXIMAL AND DISTAL CONDUCTION VELOCITIES IN ULNAR NERVE FIBRES IN CONTROL SUBJECTS http://jnnp.bmj.com/ Subject Age Sex Proximal conduction Distal conduction (yr) velocity velocity (m/s) (m/s) ...
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