Hemifacial spasm: an electrophysiological evidence of facial motorneurons hyperexcitability.

Twenty patients with primary hemifacial spasm and ten patients with Parkinson's disease were studied by means of paired stimuli blink reflex. The second stimuli were delivered at a varying time interval between 50-900 ms. The R2 response's absolute refractory periods were compared between patients and twenty one age-matched normal controls as well as between hemifacial spasm and Parkinson's disease.