REM Sleep Behavior Disorder Following Focal Brainstem Ischemia: A Case Series with Polysomnographic Characterization.

Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by dream-enacting behaviors occurring in the presence of REM sleep without atonia (RWA) and is most commonly associated with synucleinopathies. Structural lesions of the brainstem have been reported as a potential substrate of secondary RBD, yet polysomnographically confirmed cases remain sparsely documented. We report two patients with focal ischemic brainstem lesions and clinically suspected RBD who underwent detailed neurological evaluation, neuroimaging, and video-polysomnography. In both patients, polysomnography demonstrated RWA consistent with RBD. The first patient, a 75-year-old woman, exhibited prominent vocalizations and complex motor behaviors during REM sleep with RWA affecting 91% of REM sleep duration. Brain magnetic resonance imaging revealed bilateral pontine gliotic changes and a punctate subacute ischemic lesion in the right pontine tegmentum. The second patient, a 41-year-old man with a prior ischemic stroke involving the right medulla oblongata at the ponto-bulbar junction, presented with dream-enacting behaviors and with RWA affecting 41% of REM sleep duration. In both cases, motor manifestations during REM sleep were not attributable to respiratory events. Clinical context and neuroimaging findings supported a structural ischemic etiology. These cases highlight focal brainstem ischemia as a plausible structural substrate of RBD and underscore the importance of detailed polysomnographic and neuroimaging assessment in patients with cerebrovascular disease presenting with dream-enacting behaviors. Focal ischemic brainstem lesions should be considered among the potential contributors to RBD, and their recognition may have important implications for diagnostic evaluation and clinical decision-making.