In 1949 Dawson and Scott described a method of examining sensory impulses in human peripheral nerves. By their technique, the median or ulnar nerve at the level of the wrist was stimulated electrically using single shocks, and the action potential of the afferent volley recorded through surface electrodes placed over the nerve trunk at a higher level in the arm. The afferent volley contained both sensory impulses and antidromic impulses in motor fibres and gave rise to a small diphasic or triphasic potential with an amplitude of less than 50 microvolts and a duration of 2 to 3 milliseconds. To eliminate the contribution of motor fibres, Dawson (1956) modified his original technique and stimulated the digital nerves through small ring electrodes wrapped round the fingers, the afferent volley being recorded as before through surface electrodes placed over the median or ulnar nerve trunk in the arm. The sensory potentials recorded were similar in form to the mixed nerve action potentials obtained previously, but, being derived from digital nerves, they were considerably smaller in amplitude.In view of Dawson's findings it seemed worthwhile to investigate the behaviour of sensory action potentials in patients with peripheral nerve lesions, and the present paper is based on some 50 cases examined in this way. In general the technique has proved to be of considerable value in the clinical assessment of patients, and in certain cases it has provided more information about sensory nerve function than could be obtained by formal sensory testing.Methods These differed only in detail from those described previously by Dawson and Scott (1949) and by Dawson (1956). For stimulating the digital nerves, silver strips 2 to 4 mm. wide were used, covered by lint moistened in saline and firmly wrapped round the finger, with the cathode placed near the metacarpo-phalangeal joint and the anode in the region of the terminal interphalangeal joint. The stimulus itself was a brief condenser discharge (time constant approximately 70 microseconds) delivered through an isolating transformer. Surface recording electrodes were of the "saddle" pattern described by Dawson and Scott (see their Fig. 1) with an inter-electrode distance of 3 cm. Before applying the recording electrodes, the course of the median or ulnar nerve in the arm was usually mapped out by stimulation and observation of the motor response. In the few patients without any motor response to nerve stimulation the course of the nerve could not be determined in this way; in such a case recording electrodes were placed over the expected position of the nerve trunk and adjusted to give the largest response to sensory stimulation. The design of the recording electrodes was such that small lateral movements had little or no effect on the size of the recorded potential; they were thus particularly suitable for rapid tests on patients.Nerve action potentials were amplified in the conventional way and displayed on a cathode ray tube. For photography, the method of superimposition used b...

SUMMARY Nine patients are described with unilateral wasting of the hand muscles associated with elongated C7 transverse processes or with rudimentary cervical ribs. In three patients there was selective wasting of the lateral part of the thenar pad, accompanied by mild weakness of the other hand muscles. In four patients all the hand muscles were wasted, but this was more marked in the lateral part of the thenar pad than elsewhere. In two patients wasting was uniformly distributed throughout the hand. Weakness and wasting in the forearm was only present in four patients and was relatively mild. Sensory loss, when present, affected mainly the inner side of the forearm. Nerve conduction studies revealed no abnormality in the distal part of the median nerve, but some patients had reduced or absent sensory action potentials when the fifth finger was stimulated. In all nine patients a sharp fibrous band was found at operation, which extended from an elongated C7 transverse process or from a rudimentary cervical rib to the region of the scalene tubercle on the first rib. The fibrous band caused angulation of the C8 and TI roots in five patients, and of the lower trunk of the brachial plexus in three. Pathological changes were frequently visible in affected nerves at the site of angulation. Division of the fibrous band relieved pain and paraesthesiae in eight patients and atrested muscle wasting and weakness in nine patients. There was, however, only slight recovery of power in affected muscles; wasting in the hand appeared to be unchanged after periods of up to eight years.

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Although measurements of nerve conduction velocity in man were first made nearly a hundred years ago, the procedure was not used clinically until 1948 when Hodes, Larrabee, and German reported reduced conduction velocity in regenerating motor nerves. Later, Hodes (1949) described slow conduction in surviving nerve fibres after poliomyelitis, and more recently it has been shown that conduction may also be slow in certain localized peripheral nerve lesions (Simpson, 1956), in polyneuritis, and in peroneal muscular atrophy (Henriksen, 1956;Lambert, 1956; Gilliatt and Thomas, 1957;Gilliatt and Sears, 1958).The use of conduction velocity measurement as a diagnostic procedure in neurology requires a knowledge of the range of values encountered in healthy individuals. Normal values for maximum conduction velocity in human peripheral nerves have already been described by Norris, Shock, and Wagman (1953) and by Henriksen (1956), but in order to obtain a control series for our own laboratory, we have estimated maximum conduction velocity in 180 normal nerves supplying the small muscles of the hands and feet. Our own results, which are in good agreement with those of previous writers, are contained in the first part of this paper.In estimating conduction velocity, the motor nerve trunk is stimulated at two levels and the time interval between the stimulus and the onset of the muscle action potential recorded in both instances. This interval represents conduction time in the largest and most rapidly conducting motor nerve fibres stimulated, together with a further delay at the neuromuscular junction and in the muscle itself. Provided that both stimuli are supramaximal, the difference in latency of the two muscle responses is a valid estimate of conduction time in the most rapidly conducting fibres in the nerve trunk between the two points stimulated. However, conduction time in the smaller and more slowly conducting fibres of a motor nerve cannot be measured in this way as the time of onset of their muscle action potentials is obscured by the discharge of earlier units.This point is of some clinical importance, as it is not uncommon for patients to show values for maximum conduction velocity that are slightly below the accepted normal range; in such a case the question arises as to whether this represents conduction in abnormal fibres or whether it could be due to conduction in slow normal fibres uncovered by the loss of the larger and more rapidly conducting ones.In order to obtain some evidence on this question, we have attempted to compare the conduction times of different nerve fibres supplying a single muscle; the results of this investigation are presented in the second part of the paper. MethodsAll tests were performed in a warm room with the subject lying on a couch and covered with blankets. In a few subjects with cold hands or feet, the limbs to be tested were immersed in hot water for five or 10 minutes before the session, but no other method of controlling temperature was attempted.In measurements of maximum co...

SUMMARY A small pneumatic cuff inflated around the knee was used to produce tourniquet paralysis in baboons. A cuff pressure of 1,000 mm Hg maintained for one to three hours produced paralysis of distal muscles lasting up to three months. Nerve conduction studies showed that most of the motor fibres to the abductor hallucis muscle were blocked at the level of the cuff and that they conducted impulses normally in their distal parts. There was a significant correlation between the duration of compression and that of the subsequent conduction block. When tested two to three weeks after the tourniquet, the amplitude of the response of m. abductor hallucis to nerve stimulation distal to the cuff was usually slightly reduced compared with the precompression figure. This was assumed to mean that a small proportion of the motor fibres had undergone Wallerian degeneration as a result of compression. Maximal motor conduction velocity was reduced in recovering nerves. It was also reduced when a cuff pressure of 500 mm Hg was used, which was insufficient to produce persistent conduction block. In such cases a reduced velocity without evidence of block could be demonstrated 24 hours after compression. Ascending nerve action potentials were recorded from the sciatic nerve in the thigh, with stimulation at the ankle. Before compression the fastest afferent fibres had a significantly higher velocity than the fastest motor fibres in the same nerve trunk. Results after compression suggested that the high-velocity afferent fibres had a susceptibility to the procedure similar to that of the fastest motor fibres.In clinical practice, particularly in orthopaedic surgery, it is well recognized that the application of a tourniquet to a limb is sometimes followed by paralysis which may persist for weeks or months. While most of the reports in the literature date from the period when rubber tubing or Esmarch bandages were used (Lejars, 1912;Eckhoff, 1931), occasional examples have been reported after pneumatic tourniquets (Bruner, 1951;Moldaver, 1954 by Denny-Brown and Brenner in 1944. They found that there was local demyelination of nerve fibres under the tourniquet but no loss of axonal continuity through the lesion. The electrical excitability of the motor nerves distal to the tourniquet was preserved, and in most cases power in the affected muscles recovered within a few weeks. Conduction velocity during the recovery period was studied by Mayer and Denny-Brown (1964) who found it to be reduced at the site of the tourniquet compared with the velocity above and below this level.In the present experiments we have reinvestigated the conduction block produced by a tourniquet, with special reference to the timecourse of recovery. In baboons it has been possible to apply a pneumatic cuff rather than the narrower rubber tubing used by Mayer and Denny-Brown in the cat. Recovery in individual 638

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Nephropathic cystinosis is a lysosomal storage disorder leading to renal failure by age 10 years. Prolonged patient survival following renal transplantation has allowed the development of previously unknown long-term complications. Muscle involvement has been reported in a single posttransplant cystinosis patient, but the range of clinical, electrophysiologic, and histologic features has not been fully described. Thirteen of 54 post-renal-transplant patients that we examined developed weakness and wasting in the small hand muscles, with or without facial weakness and dysphagia. Tendon reflexes were preserved and sensory examinations were normal. Electrophysiologic studies in 11 affected patients showed normal nerve conduction velocities and preserved sensory action potentials. The voluntary motor units in the affected distal muscles had reduced amplitude and brief duration, confirmed with quantitative electromyography in 4 patients. Biopsy of the severely affected abductor digiti minimi or extensor carpi radialis brevis muscles in 2 patients revealed marked fiber size variability, prominent acid phosphatase-positive vacuoles, and absence of fiber type grouping or inflammatory cells. Crystals of cystine were detected in perimysial cells but not within the muscle cell vacuoles. The muscle cystine content of clinically affected muscles was markedly elevated. We conclude that a distal vacuolar myopathy is a common late complication of untreated nephropathic cystinosis. Although the cause is unclear, the general lysosomal defect in this disease may also affect the lysosomes within muscle fibers.

While the excitability changes which follow a propagated nerve impulse have been the subject of numerous studies in animals, there have been few references to this subject in man. An attempt to study the refractory period of the human ulnar nerve was made by Wagman and Flick (1951), but as recordings were made from the hypothenar muscles rather than from the nerve itself, the results are difficult to interpret. Krnjevic, Kilpatrick, and Aungle (1955) applied pairs of shocks to the ulnar nerve at the wrist, and investigated the least interval at which a response to the second shock could be recorded from the nerve at the elbow; only two subjects were examined and no estimate of the relative refractory period was made. Brown (1960) also used stimulation of the ulnar nerve at the wrist with recording at the elbow in four subjects, and noted that the recovery of normal responsiveness was followed by transient supernormality.In the present work we have studied the refractory and supernormal periods of the human median nerve with stimulation at the wrist, action potentials being recorded from the nerve above the elbow by a technique similar to that originally described by Dawson and Scott (1949). A briefpreliminaryaccount of this work has been published elsewhere (Gilliatt and Willison, 1962). METHODSFour healthy subjects were used, their ages ranging from 20 to 40 years. Most of the experiments were carried out on two subjects (R.W.G. and R.G.W.) but the main results were confirmed in the other two subjects as well.Before each experiment the subject sat with both arms in hot water to above the elbows for five or 10 minutes. He then lay covered with blankets on a couch, with the arm under examination wrapped in several layers of cotton wool. When these precautions were taken skin temperature, which was measured by a thermistor close to the stimulating cathode, remained above 35°C. throughout experiments lasting up to one hour; no 'Clinical research fellow, M.R.C. experiments are included in the present series in which skin temperature fell below 35°C.Two stimuli of independently variable intensity were delivered through a single cathode over the median nerve at the wrist. The stimulus interval could be varied in 0-1 msec. steps from 0 to 1 I-0 msec. and in 1 msec. steps for intervals longer than this. Each stimulus was a condenser discharge with a rapid rise-time, the decay having a time constant of 60, 100, or 160 psec. Voltage was continuously variable up to 350V. In most of the experiments a time constant of 160 jtsec. was used for both shocks but when small changes in nerve threshold were to be studied, for example, in plotting the supernormal period, a shorter time constant was used for the test shock. In this situation a brief shock had the advantage that a larger voltage range could be used when the physiological change in nerve threshold was small. Both stimuli were delivered through a single isolating transformer (ratio 1: 1) the output impedance being less than 1 kilohm. To allow mixing of stimuli from two...