A 64-year-old man is brought to the office for evaluation of abnormal behaviors during sleep. According to his wife, over the past 3 months the patient has had episodes of repeatedly punching at the pillow and screaming loudly while asleep. When awakened from these episodes, he recalls a disturbing dream in which he is chased by assailants and must defend himself or escape. The episodes usually last less than 1-2 minutes. Vital signs are within normal limits. General physical and mental status examinations show no abnormalities. A formal sleep study (polysomnogram) is ordered. Which of the following is most likely to be identified during this testing?
Sleep stages | ||
EEG pattern & frequencies | Characteristics | |
Non-REM stage 1 (N1) |
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Non-REM stage 2 (N2) |
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Non-REM stage 3 (N3) |
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REM |
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EEG = electroencephalogram; REM = rapid eye movement. | ||
This patient's repeated nocturnal episodes of violent motor behaviors reflecting dream enactment are consistent with REM sleep behavior disorder (RBD).
Normal REM sleep is characterized by vivid dreams, rapid eye movements, and voluntary muscle atonia due to inhibition of motor neurons. In patients with RBD, degeneration of the brainstem nuclei responsible for inhibiting spinal motor neurons during normal REM sleep leads to incomplete or absent muscle atonia (ie, excessive, sustained muscle tone during REM sleep), facilitating dream enactment behaviors. 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. Patients can usually be awakened fairly easily and are alert and oriented. They may not recall their movements during sleep but can often recall their dreams.
RBD is more likely to occur in older adult men (average age 61 years). It can be caused by medications (eg, antidepressants, narcolepsy medications). It may also be a prodromal sign of neurodegeneration with risk of subsequent onset of Parkinson disease or dementia with Lewy bodies.
(Choices B and C) Sleep can trigger seizures in patients with many types of epilepsy. Epileptiform discharges often start from a specific focus (eg, temporal or frontal lobe) and may or may not generalize. This can cause rhythmic jerking and myoclonus, but complex motor behaviors corresponding with dream content (ie, dream enactment) are more consistent with RBD. Furthermore, REM sleep is somewhat protective in epilepsy; seizures most often occur during non-REM (NREM) sleep.
(Choice D) This describes EEG findings that are common in NREM parasomnias (eg, sleep terrors, sleep walking). Although these can present with movement during sleep, patients are not alert upon awakening and have no memory of the event. In addition, NREM parasomnias most commonly present in childhood.
(Choice E) Short sleep latency and sleep-onset REM periods are characteristic of narcolepsy, a disorder characterized by chronic excessive daytime sleepiness, intrusions of REM sleep phenomena (eg, hypnagogic hallucinations, sleep paralysis), and cataplexy (emotionally triggered muscle weakness). Narcolepsy typically begins in young adulthood.
Educational objective:
REM sleep behavior disorder is a parasomnia characterized by dream-enactment behaviors due to a loss of atonia during REM sleep. Patients can usually be awakened fairly easily, are alert and oriented, and can immediately recall their dreams.