A benign motor neuron disorder: delayed cramps and fasciculation after poliomyelitis or myelitis.

Two patients had a delayed syndrome of benign fasciculation after complete recovery from paralytic poliomyelitis and a third had the syndrome after an attack of purely motor myelitis. Myalgia was prominent in all three, and two had frequent cramps. Denervation hypertrophy occurred in two. The patients were observed for at least three years, and no new weakness was seen. These cases suggest that some chronic diseases of motor neurons may be benign.