Focal sensory nerve abnormalities in patients with amyotrophic lateral sclerosis

Slowing of sensory nerve conduction is an unexplained finding in patients w ith sporadic amyotrophic lateral sclerosis (ALS). To study the frequency of these abnormalities and to study if a predisposition to the development of entrapment neuropathies is causal, 23 patients with definite ALS and 23 ag e-matched healthy volunteers were investigated prospectively. Antidromic se nsory and motor nerve conduction velocities (NCVs) were measured in ulnar a nd median nerves. Median sensory NCV was abnormally low in three patients i f compared with the lower limit of the control group; and median sensory NC V was abnormally low in nine patients (six right, eight left hands) if comp ared with ipsilateral ulnar sensory NCV. Sensory nerve conduction data did not correlate with clinical findings, such as forearm weakness or usage of canes. Motor nerve conduction data did not correlate with sensory nerve con duction data, with the exception of distal motor latency of right median ne rves, which correlated with right median sensory NCV. Our findings show how affection of sensory fibers of distal segments of median nerves can be det ected in individual patients with ALS. Nerve entrapment may contribute to t his affection, but it is not the only cause. This should be considered in d iscussions about diagnostic criteria for ALS. (C) 1999 Elsevier Science B.V . All rights reserved.