Association between bruxism and nocturnal groaning.

Bruxism is a well-known sleep-related movement disorder, usually associated with teeth damage and morning temporo-mandibular discomfort. Nocturnal groaning (NG) is a less common entity consisting of a nocturnal monotonous sound, which occurs during the expiratory phase, especially during REM sleep, recently classified among parasomnias. We describe the first case of an association between bruxism and NG. According to the polysomnographic findings, bruxism and NG episodes were closely related to each other and seemed to be organized in stereotyped sequences. Both phenomena always occurred during NREM sleep and were synchronous with cortical arousals, leg movements, and sympathetic activations. The hypothesis of a common trigger mechanism for NG and bruxism, through an arousal-induced activation, is discussed.