Locked in Lucid Rhythms: A Case of Rhythmic Movement Disorder in Rapid Eye Movement (REM) Sleep.

Sleep-related rhythmic movement disorder (SRRMD) is uncommon in adults. It can closely mimic nocturnal epilepsy and rapid eye movement (REM) sleep behavior disorder (RBD), creating significant diagnostic challenges. We report the case of a man in his mid-20s presenting with chief complaints of nightly head movements during sleep occurring multiple times each night. He intentionally shook his head to terminate these episodes, a volitional strategy he had developed to escape lucid dreams. Video-electroencephalogram (EEG) monitoring over two nights excluded epilepsy. Polysomnography (PSG) confirmed stereotyped lateral head rolling exclusively during REM sleep at approximately 1 Hz, without any loss of REM sleep atonia, thereby excluding RBD. Comorbid mild obstructive sleep apnea (apnoea-hypopnoea index (AHI) 8.7 events/hour) was also identified. Nasal septoplasty partially improved symptoms. He reported excessive daytime sleepiness, with an initial Epworth Sleepiness Scale (ESS) score of 22. Due to the presence of excessive daytime sleepiness, two Multiple Sleep Latency Tests (MSLTs) were performed at different time points to evaluate for a primary hypersomnia disorder. However, both studies were conducted under suboptimal conditions. The first was performed in the presence of untreated mild sleep apnea, and the second while the patient was receiving medications known to suppress REM sleep. Neither study demonstrated sleep-onset REM periods, and mean sleep latencies of 7.2 and 12 minutes did not meet the diagnostic criteria for narcolepsy. Nevertheless, narcolepsy could not be definitively excluded because of the suboptimal testing conditions. The patient did not report symptoms suggestive of cataplexy. He experienced rare episodes of isolated sleep paralysis and a single episode of hypnopompic hallucination. The patient denied experiencing sleep attacks. He managed daytime sleepiness by scheduling daytime naps, which could last up to one to two hours. Sequential pharmacotherapy with amitriptyline, followed by nortriptyline, and subsequently the addition of venlafaxine and bupropion, achieved complete resolution of rhythmic movements and excessive daytime sleepiness. We identified no previous reports describing a patient with successful management of rhythmic head movements during REM sleep using sequential tricyclic antidepressant (TCA), selective serotonin reuptake inhibitor (SSRI), and serotonin-norepinephrine reuptake inhibitor (SNRI) therapy for this condition. At the six-month follow-up, the patient's ESS score improved from 22 to 3.