Lost in a Dream

Rapid-eye-movement sleep behavior disorder (RBD) is a parasomnia that is closely associated with neurodegenerative disorders. RBD is usually caused by neurodegeneration within the brainstem that disables the system responsible for immobilizing skeletal muscles during REM sleep and thus permits motor neurons to activate these muscles during dreaming. The underlying source of the brainstem neurodegeneration spreads over time to other central nervous system regions until it has sufficiently evolved to permit clinical recognition of the underlying neurodegenerative disorder. Longitudinal follow-up of patients with RBD has demonstrated that most patients subsequently develop some neurodegenerative disorder years later, particularly the synucleinopathies. We review the relationship between RBD and dementia with Lewy bodies, which is one of the synucleinopathies. The management of RBD is reviewed with discussion of the relevant considerations in patients with dementia with Lewy bodies.