Conduction of the sciatic nerve in its proximal and distal segment in patients with ALS (amyotrophic lateral sclerosis).

Conduction in the proximal segment of the sciatic nerve was assessed by recording the latencies of M and H responses from soleus muscle, in the distal segment by comparing the latencies of M waves from the abductor hallucis muscle, obtained by stimulating the tibial nerve in the popliteal fossa and at the ankle. Data from 30 patients with amyotrophic lateral sclerosis (ALS) were compared with an age-matched group of healthy subjects. We observed an increase in the difference between the latencies of M and H responses from soleus, and a lengthening of the distal latency of the M wave from abductor hallucis. The motor conduction velocity of the tibial nerve was preserved. The functional significance of the data are discussed. It is suggested that they indicate a slowing of conduction in the proximal segment of the sciatic nerve and that they can be correlated with pathological findings in proximal nerves in ALS and in the experimental anterior horn cell disorder.