Blink reflex R2 recovery curves in patients with facial palsy within ten days after onset.
The purpose of this study was to investigate the acute changes in blink reflex responses in patients with facial palsy. We used the blink reflex R2 recovery curves as an index of the excitability of the blink reflex neural circuit and evaluated the excitability of the blink reflex within 10 days after onset. Twelve patients with peripheral facial palsy were selected on condition that the degree of facial palsy was so mild that R2 responses of the blink reflex were measurable on the affected side, and they were compared with 12 healthy volunteers. Conditioning and test electrical stimuli were delivered on the affected side of the supraorbital nerve. Ipsilateral R2 response (iR2) of the blink reflex in patients was significantly enhanced at interstimulus intervals (ISIs) between conditioning and test stimuli from 100 to 1,000 ms, in comparison with the control subjects. These findings suggested hyperexcitability of the blink reflex neural circuit in patients with facial palsy. In addition to iR2, contralateral R2 response (cR2) in the patients was also significantly increased at ISIs of 100-1,000 ms to the same extent as the enhancement of iR2. All these findings suggested that the hyperexcitable changes developed in a common pathway of iR2 and cR2, but not in the ipsilateral facial motor neurons. It is suggested that the hyperexcitability of the neural circuit of the blink reflex during an acute period of facial palsy is an adaptive response to compensate for impaired facial motor function.
Toda
Naoki
N
Department of Otolaryngology, Kochi National Hospital, Kochi, Japan. mutimaro@d2.dion.nc.jp
Nakamura
Katsuhiko
K
Takeda
Noriaki
N
D000328:Adult; D000368:Aged; D001767:Blinking / Q000502:physiology*; D004576:Electromyography; D005158:Facial Paralysis / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020127:Recovery of Function; D012018:Reflex / Q000502:physiology*