Excessive muscle activity increases over time in idiopathic REM sleep behavior disorder

Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by excessive electromyographic (EMG) activity due to dysfunction of the brainstem structures modulating REM sleep atonia. Patients with idiopathic RBD often develop a neurodegenerative disease, such as Parkinson disease, over the years, suggesting progression of an underlying pathologic process in the brainstem. It is unknown if the excessive EMG activity in REM sleep changes over time in patients with idiopathic RBD.

University hospital sleep disorders center.

Eleven patients with idiopathic RBD who were studied at baseline and after a mean follow-up of 5 years.

NA.

Eleven patients with idiopathic RBD underwent polysomnography (PSG) at the moment of the diagnosis of RBD (PSG1) and after a mean follow-up of 5 years (PSG2). Tonic EMG activity in PSG1 and PSG2 was blindly quantified and compared in the mentalis muscle during REM sleep. Phasic EMG activity in PSG1 and PSG2 was blindly quantified and compared in the mentalis muscle, both biceps brachii, and both anterior tibialis during REM sleep. Patients were 9 men and 2 women with a mean age of 73.2 +/- 5.4 years and a mean RBD duration of 10.7 +/- 5.3 years at PSG2. In each of the 5 muscles and combination of muscles evaluated, phasic EMG activity was significantly greater in PSG2 than in PSG1 (P < 0.022 in all muscles studied). Mentalis tonic EMG activity increased from 30% to 54% (P = 0.013). No correlation was found between age of the patients and quantity of EMG activity at PSG1 (tonic; P = 0.69, phasic P = 0.89) and at PSG2 (tonic; P = 0.16, phasic; P = 0.42).

Excessive tonic and phasic EMG activity during REM sleep increases over time in subjects with idiopathic RBD. This finding suggests that, in subjects with idiopathic RBD, there is an underlying progressive pathologic process damaging the brainstem structures that modulate REM sleep.