Motor disturbance during REM sleep in group A xeroderma pigmentosum

We investigated motor phenomena during rapid eye movement (REM) sleep in 13 patients with group A xeroderma pigmentosum aged from 11 to 39 months, and compared them with those obtained from 12 age-matched controls. At the time of sleep study, they had no abnormality on routine electrophysiological examinations. The amount of REM sleep and the incidence of motor phenomena during REM sleep in patients were similar to those in age-matched controls. However using the newly designated indices, we demonstrated disturbance on both the tonic motor inhibition occurring during the whole REM sleep period and the phasic one acting simultaneously with horizontal rapid eye movements in these patients. Since the motor inhibition during REM sleep is mediated by the subcortical structures, our study indicate that these structures are functionally impaired in group A xeroderma pigmentosum even during the early stage of the illness.