Functional changes and adverse reactions after successful treatment of hereditary myokymia: a case report.

Abstract

Myokymia is a vermiform motion of muscle that can be found in conditions in which there is pathology to the peripheral nerve to that muscle. There are inherited syndromes that can present with muscle cramping and myokymia that have been described, but little information exists on long-term follow-up. In this case study, a 12-year-old girl had an inherited form of myokymia, as determined by clinical examination, electromyographic findings, and family history. The mode of inheritance appeared to be autosomal dominant with reduced penetrance. Carbamazepine was used successfully to treat this disorder. Measurements were made of strength and endurance before and after treatment; significant improvement was seen in endurance with little effect on strength. The patient was able to discontinue carbamazepine without return of symptoms and subsequently was not limited in her activities. Return of symptoms was seen with prednisone treatment for exacerbated asthma. The symptoms resolved with restarting the carbamazepine and weaning of the prednisone. Discussion is presented on the possible mechanism by which anticonvulsant and steroid therapy exert their effects on myokymia.