Treatment with botulinum toxin improves the hyperexcitability of the facial motoneuron in patients with hemifacial spasm

• Published in: Neurological research (New York) 2010-07, Vol.32 (6), p.656-660
• Main Authors: Ishikawa, Mami, Takashima, Koichi, Kamochi, Haruna, Kusaka, Gen, Shinoda, Sohji, Watanabe, Eiju
• Format: Article
• Language: English
• Subjects: ABNORMAL MUSCLE RESPONSE; Aged; Aged, 80 and over; BLINK REFLEX; Blinking - drug effects; BOTULINUM TOXIN; Botulinum Toxins, Type A - pharmacology; Botulinum Toxins, Type A - therapeutic use; Electric Stimulation - methods; Evoked Potentials - drug effects; F WAVE; Facial Nerve - drug effects; Facial Nerve - pathology; Female; Follow-Up Studies; HEMIFACIAL SPASM; Hemifacial Spasm - drug therapy; Hemifacial Spasm - pathology; Humans; Male; Middle Aged; Motor Neurons - drug effects; Neuromuscular Agents - pharmacology; Neuromuscular Agents - therapeutic use; Time Factors
• ISSN: 0161-6412; 1743-1328
• DOI: 10.1179/174313209X431129

Botulinum toxin type A (BTX) injection into the orbicularis oculi muscle is an effective treatment for patients with hemifacial spasm (HFS). The objectives of this study were to investigate the effect of this treatment on HFS, in particular the associated hyperexcitability of the facial motor nucleus, and to discuss the potential mechanism of HFS. F waves in the mentalis muscle were examined before, 2 and 6 weeks after the BTX treatment of only the orbicularis oculi muscle in ten patients with HFS. F/M ratio, duration of F waves and frequency of F waves decreased significantly after the BTX treatment compared with those before the BTX treatment. These findings demonstrate that the excitability of the facial motonucleus decreases after BTX treatment of the orbicularis oculi muscle. From these results, we hypothesize that the trigeminal afferent input and the cortical control contribute to the hyperexcitability of the facial motor nucleus in patients with HFS. This warrants further investigation into the pathophysiology of HFS.