A 58-year-old man comes to the office accompanied by his wife, who is concerned about his abnormal behavior during sleep. Several years ago she first noticed that he would occasionally shout and jerk his arms and legs while remaining asleep. Over the past year, these episodes have become more frequent, occurring 3-4 nights a week, and his movements have become more violent. The episodes typically occur at least 2 hours after he has fallen asleep. Sometimes he kicks and punches his wife as if he were defending himself from attack. The patient has fallen out of bed on occasion and once knocked over the nightstand. His wife is afraid that he will inadvertently injure himself or her. The patient has no history of irritable, aggressive, or violent behavior during the day or any history of sleep difficulties; however, his dreams have become more intense and he has frequent nightmares of being attacked. He has a history of hypertension that is well controlled. Physical examination is unremarkable. This patient is at greatest risk of developing which of the following disorders?
This patient's repeated nocturnal episodes of violent and automatic complex motor behaviors reflecting dream enactment is consistent with rapid eye movement (REM) sleep behavior disorder (RBD). Dream enactment occurs because the muscle atonia that usually accompanies REM sleep is absent or incomplete in RBD. Episodes typically occur at least 90 minutes after sleep onset, coinciding with the onset of REM sleep, and are more frequent in the second half of the night when the percentage of REM sleep increases.
RBD is more likely to occur in men age >50 years and has a very strong association with the future development of alpha-synuclein neurodegenerative disorders. Alpha-synuclein is a synaptic protein that accumulates in some neurologic conditions. Up to 90% of patients with idiopathic RBD eventually develop either Parkinson disease (PD) or another disorder of alpha-synuclein neurodegeneration (dementia with Lewy bodies or multiple system atrophy). The rate of conversion of RBD to PD is approximately 50% every 10 years. Idiopathic RBD is considered a prodromal marker of PD and other synucleinopathies.
(Choices A, B, C, and D) Although RBD may occur in these nonsynuclein neurodegenerative disorders, it is much more commonly associated with PD. Furthermore, RBD is not considered a prodromal marker for these nonsynuclein disorders.
(Choice E) There is no known pathophysiological association between RBD and obstructive sleep apnea (OSA). Patients with suspected RBD should undergo polysomnography to confirm the diagnosis and rule out OSA and other conditions.
(Choice G) Patients with RBD are not at an increased risk of developing a seizure disorder.
Educational objective:
REM sleep behavior disorder (RBD) is characterized by dream enactment during REM sleep atonia. Most patients with idiopathic RBD eventually develop a disorder of alpha-synuclein neurodegeneration, most commonly Parkinson disease.