P251 Contribution of electrophysiology in muscular channelopathies diagnosis

Abstract

Muscle channelopathies are a rare group of neuromuscular disorders caused by mutations in ion channels. Periodic paralysis is defined by the occurrence of episodic acute and reversible attacks of muscle weakness, electrophysiological exploration was not enough codified, following the works of Fournier et al. (2004) the contribution of EDX was greatly improved. We report the results of 3 cases with periodic paralysis and discuss the interest of EDX. In 3 patients aged 14, 46 and 43 years, changes in the amplitude of motor potentials were studied during long and short-term stress tests. Results were compared with those observed in 10 controls. In both three patients, a reduction in amplitude of CMAP induced by stimulation of the ulnar nerve with recording at the adductor muscle of the 5th finger was noted after a long muscle contraction (5 min); This decrease is clear from 30 min after end of the exercise and persists for at least 50 min, this has never been observed in normal subjects. This results are similar to those reported by Fournier et al., 2004, Kuntzer et al., 2000, McManis et al., 1986, Meola et al., 2009, Tan Veronica et al., 2011. The diagnosis of periodic paralysis is difficult because of their rarity; from the poverty of objective clinical signs outside crises. Differential diagnosis may occur with other acute flaccid paralysis. electrophysiology can even guide the molecular analysis. electrophysiology, if executed according to recent protocols, is important to confirm the diagnosis (especially since EDX abnormalities can be found even a year after a crisis) and also to orient molecular diagnosis.