The effects of botulinum toxin on hemifacial spasm: an electrophysiologic investigation.

Forty-one patients with unilateral or bilateral facial spasm were studied by electrophysiologic examination. All patients received local treatment with botulinum toxin. In the patients and controls, the measurements of the blink reflex revealed changes that (1) may indicate a central origin of the spasm in some cases, and (2) make it likely that the trigeminal nerve influences the facial nucleus and is thus involved in the regulation of the spasm.