The majority of motor parasomnias and almost all nocturnal seizures occur out of NREM sleep. 1,2 The only well-defined disorders that are exclusively REM related are REM sleep behavior disorder (RBD) 3 and painful nocturnal erections. Catathrenia is a disorder that arises mostly but not exclusively out of REM. 4 There is also a single case report of periodic movements in sleep (PMS) occurring predominantly in REM. 5 Otherwise, the medical literature is sparse on reports of REM dependant motor parasomnias. We report an unusual case of a stereotypical REM sleep motor parasomnia.
A 54-year-old man presented with a 5-year history of complex, stereotypical, and nocturnal movements that were disruptive to his wife's sleep and minimally to his as well. They tended to occur several times a week usually 4 hours into sleep and repeated approximately every 30 seconds for about an hour. Their semiology, according to his wife, did not change from night to night. He aroused easily from these and was immediately alert without any dream recall. These were not triggered either by sleep deprivation or stress. The next day he was not sleepy (Epworth sleepiness scale score 5/24), but fatigued and had sore upper extremities and neck muscles.
Medical and family histories were noncontributory. He was only on antihypertensives and allopurinol. Physical examination was unremarkable.
An MRI of the brain was normal. A polysomnogram (PSG) was done with 16 EEG channels, 2 EOG channels, 2 mentalis EMG channels, thermistor, pressure transducer, chest and abdomen effort belts, oximetry, 1 channel ECG, 2 bilateral tibialis anterior (TA) EMG channels, and a snore microphone. The PSG was significant only for mild positional obstructive sleep apnea with a total AHI of 10/hr, supine AHI of 22/hr, and lateral AHI of 1/hr. No PLMS occurred. No events occurred on the night of the PSG and his muscle tone was appropriately suppressed in REM sleep.
The patient was monitored overnight. The previous montage was replicated with the exception of the TA electrodes, snore microphone, and the thermistor. Thirteen distinct typical events, of 3 seconds duration each, were captured, all arising from REM sleep. Three of the events occurred in the first REM period of the night at a frequency of one every 30 seconds. Three of the second REM period with a frequency of 1 per minute, another two at the beginning of the third and