TEMPERATURE-SENSITIVE REPETITIVE DISCHARGES IN PARAMYOTONIA-CONGENITA

A 47-year-old female with paramyotonia congenita was studied with elec tromyography and showed minimal myotonic discharges but prominent repe titive discharges in hand muscles at room temperature. With cooling th e hand, the repetitive discharges ceased as the myotonic potentials be came prominent. With exercise and further cooling, the myotonic discha rges increased and the strength of the muscle and recruitment pattern decreased. With warming, the myotonic discharges decreased as the repe titive discharges reappeared. This is the first report of repetitive d ischarges occurring in a patient with temperature-sensitive sodium cha nnel myotonia. It is postulated that the repetitive discharges as well as the myotonic discharges are the manifestation of muscle membrane h yperexcitability secondary to the abnormal, noninactivating sodium cha nnels. (C) 1997 John Wiley & Sons, Inc.