Rapid eye movement behaviour disorder

Clinical record

A 70-year-old man was referred to a specialist sleep service in December 2010 by his general practitioner at the prompting of his wife. He reported a 7–8-year history of near-nightly, increasingly severe sleep disturbance with vivid dreams which would occur in the latter half of the night. Bedclothes were often found strewn around the room, and he would wake in unusual positions. The dreams usually related to being chased or attacked, and the patient could recall them in great detail. While asleep, the patient frequently shouted in response to the dreams. Violent motor responses to the dreams were also common — the patient had kicked, punched and attempted to choke his wife while asleep, he had fallen out of bed, and he had leapt into wardrobes and onto bedside tables. The patient and his wife had suffered injuries. He had surrounded his bed with mattresses to prevent further injury, and had taken to restraining himself to the frame of his bed with two belts strapped firmly around his waist and chest. He reported being aware of the violent behaviour. His wife had moved into a separate bedroom for her own safety.

The patient reported that he slept for 6–7 hours/night and did not experience problematic daytime sleepiness (his Epworth Sleepiness Scale score was 1 out of a possible 24 [a normal daytime sleepiness level]). He did not have a history of any of the following: snoring, witnessed apnoeas, choking arousals or other symptoms suggestive of obstructive sleep apnoea; symptoms of restless legs syndrome; cataplexy, hypnagogic hallucinations or sleep paralysis; or psychiatric illness or neurological problems. He reported taking oxazepam 15–30 mg on rare occasions, but this had no impact on the sleep disturbance. His body mass index was 36 kg/m². Results of a physical examination, including a full neurological examination, were unremarkable. The patient was not taking any psychotropic medication. Results of blood tests (complete blood count; levels of electrolytes, urea, creatinine and C-reactive protein; liver function tests; thyroid function tests; and iron studies) were unremarkable.

The patient underwent overnight laboratory-based polysomnography (Figure) with video monitoring. Total sleep time was 404 minutes, with a normal sleep efficiency (time asleep ÷ time in bed) of 85.7%, a normal arousal index of 9.3 events/hour and a normal apnoea–hypopnoea index of 0.7 events/hour. Minor periodic limb movements were detected but were not associated with electroencephalographic arousals.

During periods of rapid eye movement (REM) sleep, abnormal motor activity was detected (Figure, B). Muscle tone, as measured by electromyographic tone, actually increased during some periods of REM sleep, and phasic limb movements were seen during these periods. The patient thrashed his arms around on a number of occasions during REM sleep, but no other violent motor activity was detected. There was no evidence of seizure activity on the electroencephalogram recording. The polysomnography findings were thought to be consistent with a diagnosis of REM sleep behaviour disorder.

After receiving education regarding his diagnosis, the patient was started on clonazepam 0.25 mg at night. There was no significant response at this dose, which was then titrated up in 0.25 mg increments to a dose of 1 mg at night, at which point the symptoms abated significantly. At 2-year follow-up, the patient reported that this improvement had been maintained, with violent dream enactment behaviour occurring rarely, and no episodes of falling out of bed or injuries. He reported significant subjective improvement in his sleep quality. To date, no emergence of neurological symptoms has been noted.