Two Cases of REM Sleep Behavior Disorder Combined with Severe Obstructive Sleep Apnea: Misdiagnosed as “Pseudo-REM Sleep Behavior Disorder” by Diagnostic Polysomnography

REM sleep behavior disorder (RBD) is a sleep disorder characterized by loss of normal voluntary muscle atonia during REM sleep associated with complex motor behavior while dreaming. Dream-enacting behaviors can also occur in patients with other sleep disorders such as obstructive sleep apnea (OSA). This clinical situation has been termed "pseudo-RBD". In contrast, OSA causes frequent arousal, which may consequently result in masking of RBD symptoms. We reported two patients with severe OSA, who were initially diagnosed with "pseudo-RBD" but on continuous positive airway pressure (CPAP) titration, rediagnosed with "true-RBD". When RBD is clinically suspected but is not confirmed by diagnostic overnight polysomnography, we have to keep in mind that RBD could be detected during CPAP titration.