Analysis of blink activity and anomalous eyelid movements in patients with hemifacial spasm.

To assess spontaneous blinking and anomalous eyelid movements in patients with hemifacial spasm with an emphasis on interocular differences. Spontaneous eyelid movements were registered bilaterally for 3 min using a high-speed video camera in 28 patients with hemifacial spasm (HFS) who had not been treated with botulinum toxin injections for at least 5 months. The degree of blink conjugacy, maximum velocity, and amplitude of the closing phase of the blinks were determined for the affected and non-affected sides. Out of the 28 subjects, 23 (82%) presented with abnormal nonconjugate spasms that were similar to blinks, and in 17 (61%), high-frequency eyelid twitches were detected between blinks on the affected eye. The rate of nonconjugate blink-like spasms ranged from 0.3 to 24.7 movements/min. With regard for conjugate blinks, there was no significant interocular difference in amplitudes or eyelid closure velocities. The amplitude and velocity were significantly lower for nonconjugate movements than for spontaneous blinks. HFS is a unique condition in which complex patterns of eyelid movements, including both conjugate and nonconjugate movements, are present. Conjugate movements correspond to spontaneous blinking, and the same metrics were observed in affected and non-affected eyes. Nonconjugate movements correspond to anomalous nonconjugate blink-like spasms and high-frequency eyelid twitches in the affected eye, both of which were characterized by lower amplitudes and velocities than were observed in conjugate movements.