Periodic limb movements and sleep-wake disorder.

The relationship of periodic limb movements (PLM) and sleep-wake disorders in 11 patients was investigated. Two patients complained of insomnia. A patient with cervical spinal canal stenosis had a complaint of difficulty in initiating sleep. Movement index (MI) was 51 and PLM arousal index was 8. A patient with chronic hemodialysis had a complaint of difficulty in initiating and maintaining sleep. MI was 79 and PLM arousal index was 51. One patient with myotonic dystrophy showed 79 in MI and 3 in PLM arousal index. It is suspected that myotonic dystrophy is less sensitive to stimuli during sleep (i.e. PLM). These results suggest that the sleep-wake disorders associated with PLM relate to the threshold of awakening.