Original articleVocalization during episodes of prolonged expiration: a parasomnia related to REM sleep
Introduction
The term ‘parasomnia’ refers to clinical disorders that are not related to abnormalities of the sleep/wake processes per se, but that are characterized by undesirable physical phenomena occurring predominantly during sleep [1]. To date, many parasomnias with affinity for NREM sleep, REM sleep or both sleep states have been identified. In the International Classification of Sleep Disorders (ICSD, 1990) sleeptalking (somniloquy), sleep terrors (pavor nocturnus), REM sleep behavior disorder are listed as separate diagnostic entries [2]. In the present article, we report on a sleep-related respiratory phenomenon that has features in common with the syndromes mentioned above, that also may be confused with central sleep apnea, but still is distinct on several points. Polysomnography (PSG) typically reveals bradypneic events that tend to cluster and are most prevalent during REM cycles in the latter part of nocturnal sleep. These bradypneas consist of a deep inspiration, followed by prolonged expiration and expiratory monotonous vocalization. In order to support our hypothesis that a specific nosological entity is involved, we report here all pertinent information on this new parasomnia, including the clinical records, the results of descriptive statistical analyses, differential diagnosis and outcomes of therapeutic interventions.
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Methods
During a 3-year period, 1836 subjects presenting with various kinds of sleep disorders were studied in our sleep laboratory, which is part of a multidisciplinary sleep disorders center operating in a university hospital setting. The diagnostic work-up of all patients comprised administration of a 91-item sleep questionnaire, medical history, general clinical examination, and full PSG including video-recording of sleep. The parasomnia that is subject of the present article was detected in ten
Clinical records
To date, we have identified ten patients of caucasian race (seven males and three females) showing the particular sleep-related disorder that is subject of the present study. This patient group represents 0.54% of the population admitted to the sleep lab during the 3-year observation period. Their clinical records, including medical history and neurological examination, are summarized in Table 1, Table 2. All patients denied the presence of sleep paralysis, sleep onset hallucinations and
Discussion
The clinical hallmark of the sleep disorder described in this article is nocturnal vocalization. The vocal noise produced by the patients is reported to be loud, to occur on a regular basis and to be of serious annoyance to room-mates or bed partners, at whose instigation medical attention may be sought. The first symptoms typically appear during adolescence or early adulthood. The history is not suggestive of an inherited pattern. Although patients are usually unaware of their breathing
Acknowledgments
We are indebted to M. Neyens for the scoring of sleep studies; F. De Poorter for patient care; Dr R. Deman for referring one of the patients; Professor G. Bullock for review of English grammar. We express our special appreciation to Dr John W. Shepard, Jr, M.D. and Dr Michael Silber, M.D. (Mayo Clinic, Rochester, MN, USA) for review of some polysomnographic data and expert advice. This research was supported by the Flemish Fund for Scientific Research (FWO grant no. 3.0092.93).
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