RBD is a parasomnia. It is categorized as either idiopathic or symptomatic. Idiopathic RBD is the term used when RBD is not associated with another ongoing neurological condition. When it results from an identifiable underlying etiology, RBD is referred to as symptomatic RBD (and considered a symptom of the underlying disorder). Up to almost 92% of patients with idiopathic RBD will go on to develop a neurodegenerative disorder. The disorders most strongly associated with RBD are the synucleinopathies, particularly Parkinson's disease, dementia with Lewy bodies, and to a lesser extent, multiple system atrophy.