Autonomous peripheral nerve activity causing generalized muscle stiffness and fasciculations: report of a case with physiological, pharmacological, and morphological observations.

A 14-year-old boy with generalized muscle weakness, stiffness and fasciculations associated with profuse and continuous electromyographic (EMG) activity is described. The spontaneous mechanical and electrical muscle activity was unaffected by sleep, general anesthesia, or spinal anesthesia but was abolished by small doses of curare, succinyl-choline, and gallamine. Proximal and distal peripheral nerve block caused moderate and marked reduction of EMG activity, respectively, thus indicating that the disorder is due to autonomous peripheral nerve activity. The delayed motor nerve conduction velocities and the structural abnormalities seen in some of the myelin sheaths by light and electron microscopic studies on sural nerve biopsy preparations constitute further evidence that the peripheral nerve is the site of abnormality in this disorder. Diphenyl hydantoin and carbamazepine maintenance therapy produced adequate clinical relief.