Catathrenia (nocturnal groaning): an abnormal respiratory pattern during sleep.

Catathrenia (nocturnal groaning) is a rare condition characterized by monotonous irregular groans occurring during sleep. Ten patients (five women; mean age: 27 +/- 7.4 years, range: 15-41) with sleep-related groaning persisting for years or decades and normal daytime fibreoptic laryngoscopy and respiratory function tests underwent videopolysomnographic recording (VPSG) analysing their respiratory patterns during sleep. After the VPSG, all patients were clinically followed up for a mean period of 4.9 +/- 3.5 years. On VPSG, all patients showed nocturnal groaning during NREM sleep and particularly during REM sleep stages. Groaning was associated with disproportionate prolonged expiration causing reduced breathing rate without oxygen desaturation. The breathing pattern with prolonged expiration and sound production alternated with a normal respiratory pattern without groaning. Endoesophageal pressure during groaning showed mildly positive swings at the initial phase of expiration suggesting a partial mild expiratory upper airway obstruction. At the end of the follow-up period, all patients reported persistent nocturnal groaning but no other clinical manifestations. Groaning confined to sleep alternating with normal breathing and the absence of long-term clinical consequences suggest that catathrenia is because of an abnormality of the internal respiratory drive system, possibly related to persistence of a neonatal (vestigial) type of breathing pattern.