Blink reflex studies in postparalytic facial syndrome and blepharospasm: trigeminal and extratrigeminal somatosensory stimulation.

PURPOSE: The somatosensory-evoked blink reflex (SBR) is one of the release phenomena of blink reflex, possibly resulting from increased excitability of brainstem reticular formation. METHODS: The authors investigated trigeminal blink responses and SBR in 26 patients with postparalytic facial syndrome (PFS) with synkinesia, 18 patients with essential blepharospasm, and 36 healthy volunteers (control participants). RESULTS: Trigeminal blink reflex responses were elicited in all participants, whereas SBRs were elicited in 44.4% of control participants, 38.9% of patients with essential blepharospasm, and 65.4% of patients with PFS. The mean R2 amplitude and duration and the mean amplitude and duration of SBR were highest in patients with essential blepharospasm. The mean latency of SBR was shorter on the symptomatic side of patients with PFS when compared with the asymptomatic side. The mean R2 duration on the symptomatic side of the patients with PFS was longer than the control participants. CONCLUSIONS: These results showed that somatosensory stimulation could be used as an alternative method to demonstrate increased excitability in facial motor neuron in patients with PFS and essential blepharospasm. Disease states relating to different peripheral and/or suprasegmental structures could also influence blink reflex and change its basal excitability and manner in which the reflex responds to modulatory factors.