Blink reflex excitability is abnormal in patients with periodic leg movements in sleep.

The excitability of the late component of the blink reflex was measured in 19 patients with periodic leg movements in sleep (PLMS) and in 18 control patients with other sleep complaints. PLMS patients were not different from controls regarding age, body mass index, and apneas and hypopneas per hour of sleep. The latencies of the R1 and R2 components of the blink reflex were not different between the groups. However, in PLMS, the excitability of the R2 response was markedly enhanced: The second R2 response to a pair of stimuli given at an interval of 500 ms was in PLMS 59.5% (range 21-87%) of the first R2 response and in controls 18.8% (range 2-79%) (p < 0.0001, Mann-Whitney U test). These results provide further evidence of an altered motor control in PLMS, which is likely to be located subcortically and possibly related to the dopaminergic striatopallidal system.