Vocalization during episodes of prolonged expiration: a parasomnia related to REM sleep.

Objective: We report on a sleep-related respiratory dysrhythmia that is characterized by episodes of bradypnea associated with vocalization.Background: To date, many parasomnias with affinity for NREM sleep, REM sleep or both sleep states have been identified. While the reported clinical syndrome may resemble these known parasomnias, different clinical features are pointed out.Methods: Ten patients (seven males and three females) aged between 20 and 49 years, were included. All patients underwent standard clinical examinations and full polysomnography.Results: The principal complaint was unusual sound-making during sleep. Polysomnography demonstrated the presence of clustered bradypneic events associated with prolonged expiration and expiratory sound production. Replay of the sound signal revealed monotonous vocalization, consistent with groaning. These episodes occurred predominantly during REM sleep. Repeated sleep studies showed a remarkably constant night-to-night consistency of these vocalization episodes. Medical and neurological examinations disclosed no particular abnormalities, except in one patient, in whom a frontal meningioma was detected. Different empirical treatments, including pharmacotherapy and nasal continuous positive airway pressure therapy, provided insufficient symptomatic control.Conclusions: The syndrome described above clearly has distinct features with respect to well-defined sleep disorders, such as central sleep apnea syndrome and somniloquy. Therefore, it is proposed as a separate nosological entity.