title: Hemifacial spasm: an electrophysiological evidence of facial motorneurons hyperexcitability.
abstract: 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. In normal subjects, the mean absolute refractory period was found to be 271.42 +/- 64.36 ms, in hemifacial spasm 160.00 +/- 50.62 ms and in Parkinson's disease 157.14 +/- 53.45 ms. The absolute refractory periods obtained from patients were significantly shorter than in normal controls (p < 0.05). However the values between patients with hemifacial spasm and Parkinson's disease were not (p > 0.05). This result strongly supports bilateral facial motoneurons hyperexcitability as the underlying mechanism of hemifacial spasm.
authors.affiliation: Department of Medicine, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors.forename: S
authors.initials: S
authors.lastname: Eksantivongs
authors.forename: N
authors.initials: N
authors.lastname: Poungvarin
authors.forename: A
authors.initials: A
authors.lastname: Viriyavejakul
authors.forename: J
authors.initials: J
authors.lastname: Punyamee
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005152:Facial Muscles / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000502:physiology*; D012032:Refractory Period, Electrophysiological; D013035:Spasm / Q000503:physiopathology*