MS 176.qxp

RAPID EYE MOVEMENT (REM) SLEEP BEHAVIOR DISORDER (RBD) IS A PARASOMNIA CHARACTERIZED BY DREAM-ENACTING BEHAVIORS RELATED TO LOSS OF the normal generalized skeletal muscle atonia during REM sleep1,2. RBD may be idiopathic or associated with neurodegenerative diseases such as Parkinson’s disease3, multiple system atrophy4, dementia with Lewy bodies5, Machado-Joseph disease6 and parkinsonism with parkin gene mutations (Park2)7. Patients with RBD display abnormal motor and vocal behaviors such as punching, falling out of bed and shouting that are associated to frightening dreams1,2. However, these dream-enacting behaviors can also occur in other sleep disorders, a clinical situation termed as “pseudo-RBD”1. Recently, it has been shown that 65% of the subjects initially diagnosed as having idiopathic RBD eventually developed parkinsonism and/or dementia following a mean interval of 13 years8. Therefore, correct diagnosis of RBD is important because if “pseudo-RBD” is misdiagnosed as true RBD, then these subjects may be misinformed that they are at risk of developing parkinsonism and/or cognitive impairment, which could carry emotional consequences and medical malpractice liability. Moreover, correct diagnosis of RBD is also important because patients with RBD may injure themselves and their bed partners, and because this parasomnia can be effectively treated with clonazepam1,2. Here, we describe a group of 16 subjects who reported harmful or potentially harmful dream-enacting behaviors resembling RBD, but video-polysomnography (VPSG) failed to demonstrate REM sleep without atonia and excessive phasic muscle activity. Furthermore, VPSG demonstrated severe obstructive sleep apnea-hypopnea (OSAH) inducing abnormal motor and vocal behaviors.