Localized myokymia caused by peripheral nerve injury.

One year after a gunshot wound in the popliteal fossa, a 30-year-old man began to experience cramps and myokymia in the left gastrocnemius muscle. Myokymia was characterized by vermicular fibrillary movements localized to the gastrocnemius muscle and accompanied by plantarflexion and dorsiflexion of the toes. Neurologic examination, nerve conduction velocities, electromyograms, and muscle biopsy findings showed affection of left common peroneal and posterior tibial nerves. The myokymia disappeared during sleep, spinal anesthesia, and treatment with carbamazepine.