The growing literature on the rapid eye movement (REM) sleep behaviour disorder (RBD)–neurodegenerative disease association continues to provide insights into normal and abnormal neurological functioning, particularly in the synucleinopathies.1 The Braak staging scheme for the Parkinson’s disease (PD) phenotype of Lewy body disease (LBD) nicely explains the temporal evolution of features in the many patients with PD—autonomic dysfunction and/or RBD, typically followed years later by parkinsonism, followed years later by dementia—which reflects the progression of Lewy bodies and Lewy neurites in a largely ascending manner from the peripheral nervous system, with or without the spinal cord, to the brainstem to the limbic system to the …