Hemifacial spasm in sleep.

We conducted polygraphic studies during wakefulness and all-night sleep in 13 patients with cryptogenic and 3 with postparalytic hemifacial spasm. The movements decreased progressively with deepening sleep stages, reaching lowest values in REM sleep. The reduction was inversely related to the severity of movements during wakefulness. There was no relation between hemifacial spasm and mimic activity on the unaffected side. Central inhibitory processes may account for the partial decline in intensity of the movements in sleep.