Lower motor neuron dysfunction in patients with multiple sclerosis.

A patient in whom multiple sclerosis (MS) was ultimately diagnosed presented with a lower motor neuron syndrome involving 1 hand, with EMG evidence of denervation. Twelve other patients were subsequently identified with definite MS and asymmetric hand atrophy. These patients were studied clinically and electrophysiologically. Evidence of chronic and ongoing denervation was noted in the hands of 12 of the 13 patients; in only 3 patients could the EMG abnormalities be accounted for by peripheral nerve lesions. Thus, lesions resulting in lower motor neuron damage may occur in the central nervous system in MS patients. We suggest that demyelination in the region of the ventral root exit zone may account for these findings.