A brainstem inflammatory lesion causing REM sleep behavior disorder and sleepwalking (parasomnia overlap disorder)

A 40-year-old woman with no prior parasomnia developed an acute inflammatory rhombencephalitis with multiple cranial nerve palsies and cerebellar ataxia, followed by myelitis 6months later, and by an intracranial thrombophlebitis 1month after. Between and after these episodes, she had a persistent, mild right internuclear ophtalmoplegia, a mild cerebellar ataxia, and a severe REM sleep behavior disorder (RBD) lasting for 2years. She talked, sang and moved nightly while asleep, and injured her son (cosleeping with her) while asleep. In addition, she walked asleep nightly. During video-polysomnography, there were two arousals during slow wave sleep without abnormal behavior, while 44% of REM sleep was without chin muscle atonia with bilateral arm and leg movements. There were small hypointensities in the right pontine tegmentum and in the right dorsal medulla on T1-weighted magnetic resonance imaging, suggesting post-inflammatory lesions that persisted between acute episodes. The RBD and sleepwalking did not improve with clonazepam, but improved with melatonin 9mg/d. The unilateral small lesion of the pontine tegmentum could be responsible for the parasomnia overlap disorder as in other rare lesional cases.