Familial continuous motor unit activity and epilepsy.

A mother and son both had muscle stiffness due to continuous generalized muscle twitching, beginning in childhood and associated with epileptic seizures. Electromyography (EMG) showed continuous motor unit activity (CMUA) at rest, which decreased during ischemia, sleep, and carbamazepine treatment, and was abolished by anesthetic nerve blockade. Genetic analysis disclosed a G724C point mutation in the potassium channel KCNA1 gene. The electrophysiological data suggested pathological impulse generation in both the peripheral and central nervous system, probably related to abnormal ion channel function. Copyright 2001 John Wiley & Sons, Inc.