Sleep bruxism as a manifestation of subclinical rapid eye movement sleep behavior disorder.

A 59-year-old man with temporomandibular joint pain/dysfunction syndrome presented with a long history of nocturnal bruxism. All-night polysomnographic recordings with video monitoring showed episodes of teeth grinding or clenching occurring exclusively during rapid eye movement (REM) sleep, which were often associated with movements of the hands and fingers and/or brief vocalization. Throughout REM sleep, there was excessive phasic chin electromyographic twitching, without increased tone, and also excessive phasic electromyographic twitching in multiple muscle sites. The patient maintained a normal nonrapid eye movement-REM cycle, but showed increased REM density. Polysomnographic characteristics suggested that there may be a common pathophysiology in a certain type of sleep bruxism and the REM sleep behavior disorder. Sleep bruxism seen in this case is concluded to be a manifestation of subclinical REM sleep behavior disorder.