Rapid Eye Movement Sleep Behavior Disorder: A Review of the Literature and Update on Current Concepts.

Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by abnormal behaviors emerging during REM sleep that may cause injury or sleep disruption. The diagnosis requires polysomnography (PSG) demonstrating a loss of normal skeletal muscle atonia during REM sleep. RBD results from dysfunction of the brain stem circuits responsible for maintaining normal REM sleep atonia and suppressing behaviors during REM sleep. The diagnosis of idiopathic RBD (IRBD), that is, RBD without an identifiable cause, is frequently followed years later by the development of a neurodegenerative disorder, most commonly one of the synucleinopathies. As such, RBD is often a step in the progression of a neurodegenerative disorder. In this circumstance, it is a manifestation of neurodegeneration occurring in the brain stem before spreading to adjacent and other CNS regions, resulting in the development of symptoms and signs that permit recognition of a specific neurodegenerative disorder. RBD has been linked with narcolepsy and has been associated with a variety of other disorders. The management of RBD focuses on preventive/safety measures, counseling, monitoring for the development of a neurodegenerative disorder, and pharmacotherapy, which is typically effective but not well understood. The purpose of this article is to review and update our current understanding of the clinical features, epidemiology, demographics, pathophysiology, evaluation, diagnosis, differential diagnosis, causes, associations, and the clinical management of RBD.