Decreased phasic EMG activity during rapid eye movement sleep in treatment-naïve Parkinson's disease: effects of treatment with levodopa and progression of illness.

Abstract

Rapid eye movement (REM) sleep behavior disorder (RBD) is frequently associated with Parkinson's disease (PD) and may anticipate its diagnosis by several years. We assessed the presence of motor dyscontrol during REM sleep in treatment-naïve PD patients and investigated the putative effect of levodopa (L-dopa) treatment on motor activity. Overnight sleep studies were performed on 15 previously untreated PD patients and 14 controls at baseline, again after a 3- to 9-month treatment period with a low dose of L-dopa, and 2 to 5 days after treatment discontinuation (in 8 patients). No differences in sleep parameters were observed across groups or treatment conditions. None of the patients met criteria for RBD at baseline, whereas 5 patients were symptomatic at the time of the second sleep study. A quantitative analysis of electromyographic (EMG) activity during REM sleep showed a lower phasic twitching activity in untreated PD than in controls. However, an increase in both phasic twitching and tonic activity was found after treatment with L-dopa. Discontinuation of treatment resulted in a return to pretreatment values of phasic but not of tonic EMG activity. Thus, the increase in phasic activity seems to depend on the effects of L-dopa, whereas the increase in tonic EMG activity during REM sleep might be caused by other factors such as the progression of disease. Potential implications for the understanding of the relationship between RBD and PD are discussed.