Implications of nocturnal symptoms towards the early diagnosis of Parkinson's disease.

Nocturnal symptoms are frequent in Parkinson disease (PD) and consist of nocturnal sleep disorders such as REM sleep behavior disorder (RBD) and restless legs syndrome. There is an increasing need for reliable, early, pre-motor diagnosis of PD, since motor symptoms occur when there is already significant neuronal loss. Recent prospective studies have shown that over 80% of idiopathic RBD patients over time converted to PD and related synucleinopathies. RBD patients have autonomic, visual, and olfactory dysfunction as well as neuroimaging abnormalities similar to those seen in PD. Studies have shown that neuroimaging abnormalities and visual and olfactory dysfunction can help predict which RBD patients will likely convert to a neurodegenerative diagnosis within a short follow-up period. These factors make RBD an ideal population for prediction to PD conversion, allowing future testing and eventual use of neuroprotective strategies.