Catathrenia (nocturnal groaning): a new type of parasomnia.

Four patients between 15 and 25 years of age presented with exclusively expiratory groaning during sleep. Groaning usually occurred during the second part of the night, beginning at age 5 to 16 years. Patients were unaware of the nocturnal noise, but it alarmed others. Results of otorhinolaryngologic and neurologic examinations were normal. Expiratory groaning arose during REM and non-REM sleep stage 2, and was repeated in clusters. Nocturnal groaning, which the authors term catathrenia, represents a distinctive parasomnia.