Abstract. Sensory and motor nerve conduction has been measured in 56 patients with chronic renal failure. Slowed nerve conduction was present in one or more segments in 38 of 39 patients with a 24‐hour creatinine clearance below 10 ml/min/1.73 m2. The impairment involved upper and lower extremities, motor and sensory fibres, distal and proximal segments, and fast and more slowly conducting fibres. The amplitude of sensory action potentials was reduced, mainly due to increased temporal dispersion and to increased incidence of irregularities in the shape of potentials. The electromyographic contraction pattern at maximal effort in the abd. poll. brev. muscle was rarely abnormal, whereas the pattern in the ext. dig. brev. muscle was compatible with a moderate to severe loss of motor units in 21 of 29 patients. All patients with electrophysiological signs of impaired nerve function had slowed motor conduction in the common peroneal nerve and/or slowed sensory conduction in the median nerve. The demonstration in the present material of an almost uniform slowing of nerve conduction in all segments examined contrasts with the reported distribution of structural changes, predominantly located in the distal parts of the legs. The hypothesis is put forward that the slowing of nerve conduction is not solely dependent on structural changes, but also on a universal toxic effect upon the nerve axon membrane by uremic toxin(s) other than urea and creatinine.

Abstract. In uremic patients the sensory conduction velocity was relatively more reduced in the wristelbow segment than in the digit‐wrist segment of the median nerve when the nervous impulse was initiated by supramaximal stimuli delivered to sensory fibers in digit 1 or 3. The proximal segment became affected earlier in the course of progressive kidney insufficiency than the distal segment. These findings were also apparent from the longitudinal course in the individual patient, and it is suggested that the uremic intoxication of the axon membrane function leads to a decremental impulse propagation.

Abstract. The sensory and motor conduction velocity in the median and common peroneal nerve in 56 patients with chronic renal failure (CRF) showed a linear correlation with the endogenous creatinine clearance (CCr) in a semilogarithmic system. The nerve conduction became impaired more severely and earlier in the course of CRF in males than in females. A significant reduction of the conduction velocity can be expected in half of the patients when the kidney function is reduced to about 10% of normal, and in terminal renal failure only few patients will show conduction velocities within normal limits. When the covariation with CCr was taken into account, the conduction velocity was not influenced by the serum concentrations of creatinine and urea, indicating that neither of these represent the neurotoxic substances in the uremic syndrome. There was no difference between the conduction velocities in patients with and without clinical signs of neuropathy when a correction was made for incomparability in the degree of renal failure. Furthermore there was a striking disparity between the predominance of clinical neurological signs in the distal parts of the legs and the almost uniform slowing of the nerve conduction in upper and lower extremities. These two latter findings indicate that the correlation between clinical findings and nerve conduction is more complicated than might be assumed from previous studies.

Abstract. Serial determinations of the sensory and motor nerve conduction, and of the vibratory perception threshold (VPT), and serial clinical neurological examinations have been performed in 16 patients during progressive renal failure and/or regular hemodialysis. During progressive renal failure a gradual and almost equal slowing of the nerve conduction was observed in lower as well as in upper extremities, although clinical neuropathy was prevalent in the lower extremities. In contrast to the gradual slowing of the nerve conduction, clinical findings usually developed abruptly, the first indication being a sudden rise in VPT. During regular hemodialysis there was no further slowing of the nerve conduction, nor was there any significant improvement. Despite this fact a marked decrease in VPT occurred within the first months, followed by a somewhat slower remission of other clinical findings. The present study thus confirms and adds further evidence to an existing dissociation between clinical findings and nerve conduction data, demonstrated in a previous study based on single observations in a larger material of patients with varying degree of renal failure. With the aim of preventing clinical neuropathy, VPT is advocated as the most valuable and simple method among the neurological variables studied for the selection of the optimal time for institution of regular hemodialytic treatment.

The normal nerve conduction in sensory and motor fibres of the median nerve has been studied in 20 females and 28 males, 16-62 years of age. There was no significant sex difference in conduction velocity. The intraindividual variation in repeated measurements was 0.9-1.8 m/sec. The conduction velocity decreased with age in all segments, and the interindividual variation was 3.4 to 4.5 mjsec (S,,*). Sensory fibres conducted faster than motor fibres of the same segment, but the difference became gradually eliminated with age. The sensory conduction velocity in the proximal segment (wrist-elbow) decreased more rapidly with age than in the distal segment (digit-wrist). Fast and more slowly conducting fibres were almost equally affected by age, resulting in an increase in the temporal dispersion of the sensory action potential. The amplitude of the sensory potential (log,,, pV) was a function of the temporal dicipersion and of the distance of the near nerve electrode from the nerve. With these corrections the amplitude was independent of age, i.e. there was no evidence of a reduction in the number of fibres. The sensory threshold to electrical stimuli increased with age and-independent of age-with the slowing of the sensory conduction velocity between wrist and elbow.During the past 20 years the determination of sensory and motor conduction velocity has obtained a prominent position in the study of the peripheral nerve function. When measuring the conduction velocity with a standard technique and procedure, age is probably the most important source of variation in normal subjects. Motor and sensory fibres, however, do not seem to be affected in parallel. Thus data presented by La Fratta and Canestrari (17) indicate that the conduction in mixed nerves becomes relatively more slowed by age than in motor fibres. This is consistent with findings by Buchthal and Rosenfalck (3), who examined purely sensory and motor fibres. They showed that sensory nerve conduction was faster than motor in young per-sons, while in old persons (70-88 years) this relationship was in fact reversed. Other electrophysiological parameters change with age, e.g. a significant decrease in the amplitude of the sensory nerve action potential has been demonstrated (3, 15). The present study, however, shows that this was solely due to an increase in the temporal dispersion of the action potential.This study was designed to derive clinically applicable limits of the normal inter-and intraindividual variation of sensory and motor conduction parameters, considering the effect of age and the interaction between the recorded parameters. The relative slowing of conduction in sengory and motor fibres and in distal and proximal segments was analysed. MATERIAL AND METHODSThe material comprised 20 females and 28 males, 16 to 62 years of age. The age distribution was the same in the two sexes. Clinical sym'ptoms or signs of peripheral nerve dysfunction were absent and there was no evidence of diseases known to predispose to peripheral neuropathy. Four persons were...