[Electrophysiological study of hemifacial spasm].

Hemifacial spasm is characterized by intermittent involuntary contractions of one or several groups of muscles innervated by the facial nerve. The possible causal mechanisms have been the subject of numerous publications. The pre-eminent work of Moller and Jannetta implicates the compression of the facial nerve at its point of entry into the central nervous system, the Root Entry Zone, while the physiopathology is poorly understood, two principle hypotheses emerge: 1) ephaptic transmission between injured fibers; 2) hyper excitability of the facial motor nucleus. Using standard electromyographic techniques and blink reflex studies, we were able to demonstrate hyperexcitability of the facial nucleus. The cause of this hyperexcitability remains unexplained. It could be the result of a permanent antidromic stimulation from a peripheral ectopic center of excitation.