Prodromal Parkinson's disease--using REM sleep behavior disorder as a window

Abstract

REM sleep behavior disorder (RBD) is characterized by loss of REM atonia of sleep, such that patients act out the contents of their dreams. Perhaps the most important facet of idiopathic RBD is that it is a powerful prodromal marker of Parkinson's disease (PD) and other synucleinopathies. Several prospective studies have now established that patients with idiopathic RBD have up to an 80% risk of developing a defined neurodegenerative synucleinopathy. This has profound implications for understanding and treating early disease. First, the extremely high risk and long latency/time to intervene make RBD patients the ideal candidates for neuroprotective therapy against synucleinopathy. Second, RBD patients can be used as a 'test lab' to assess other potential prodromal predictors of PD, which could be applied to the general population in future large-scale screening programs. Third, assessing epidemiology of RBD allows us to study the epidemiology of PD and dementia with Lewy bodies 10-15 years earlier, reducing bias and opening new hypotheses as to the mechanism of action of selected risk factors. Finally, by prospectively observing RBD patients as they transition to full neurodegenerative synucleinopathy, one has an unprecedented window in which to directly observe evolution of PD from its prodromal stages. The evidence for RBD as a marker of prodromal PD and all these implications will be discussed.

Keywords: Dementia with Lewy bodies; Parkinson's disease; Prodromal; REM sleep behavior disorder.