Catathrenia

1. Introduction to the case 

A healthy 41-year-old man presented with the chief concern of “abnormal breath sounds” during sleep for the past five years. He described making “funny noises” while exhaling after apparent breath-holding which awakened him and/or his wife almost every night. His Epworth sleepiness scale score was 6/24. There was no prior history of parasomnia or seizure disorder.

Physical exam revealed normal vital signs with a body mass index of 25kg/m2. Oropharyngeal exam revealed a Mallampati class I airway, and the remainder of the physical exam was unremarkable.

Polysomnogram (PSG) with extra arm electromyography leads and digital video recording was performed. The apnea/hypopnea index (AHI) was 1, no snoring was heard, and the oxyhemoglobin saturation remained at or above 95% throughout the study.

Expiratory groaning sounds were noted mainly during rapid eye movement (REM) sleep (see attached video), beginning with deep inspiration followed by protracted expiration during which a monotonous vocalization of groaning was produced (Fig. 1). The groaning was associated with bradycardia (Fig. 2) and ended with a grunt or an arousal (Fig. 1). The PSG findings closely resembled central apneas and were scored as such by the scoring technologist, but the respiratory dysrhythmia with bradypnea and the groaning sound during expiration preceded by a deep inspiration were distinguishing features for catathrenia. The patient declined treatment with continuous positive airway pressure (CPAP).

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Fig. 1. Overnight polysomnogram (120-s epoch) during REM sleep shows a deep inhalation (A) followed by prolonged exhalation (B) with the monotonous sound production (see online video).

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Fig. 2. 180-s epoch showing clusters of catathrenia resembling central apneas during REM sleep, differentiated by the presence of groaning.

2. Image analysis 

Fig. 1, Fig. 2.

3. Discussion 

The first case of catathrenia was reported in 1983 [1]. Since then, approximately 30 cases have appeared in the literature [4]. Onset is usually in adolescence or early adulthood, and affected individuals are often unaware of their sleep-related groaning, which usually is noted by their bed partner or a family member. Catathrenia is not associated with abnormal motor activity or other parasomnias, and physical exam, including direct laryngoscopy during wake, is usually unremarkable.

By PSG, catathrenia episodes are characterized by a deep inspiration followed by a protracted expiration when monotonous vocalization is produced [2]. The typical occurrence during REM has led to speculation that catathrenia represents exaggerated breathing irregularities during this stage of sleep. Groaning episodes usually occur with slightly decreased heart rate and blood pressure, last 2–49s, and end with a sigh or an electroencephalographic (EEG) arousal [3]. The respiratory tracings appear as central sleep apnea due to the apparent long cessation of flow and breathing effort, but careful inspection will show that in contrast to a central apnea, where the apneic pause is preceded by an exhalation, in catathrenia the breath preceding the apparent apnea is a large inhalation (Fig. 1, Fig. 2). Finally, respiratory events scored as central apneas in REM, may need close observation with a video or audio tape for vocalizations during the cessation of rhythmic inspiratory and expiratory effort.

This case illustrates the importance of being careful not to confuse catathrenia with a central apnea, especially during REM sleep, while inspecting polysomnographic tracings.