Clinical features associated with REM sleep behavior disorder symptoms in the early stages of Parkinson's disease

We aimed to characterize the clinical features associated with REM sleep behaviour disorder (RBD) in early stage Parkinson's disease (PD). Presence of clinical RBD was determined according to ICSD minimal clinical criteria and a validated RBD questionnaire. We registered time of appearance of RBD symptoms in relation to PD onset and the occurrence of RBD symptoms in the past in non-RBD patients. RBD and non-RBD groups were compared in terms of motor and cognitive dysfunction. The same comparisons were made between patients who reported RBD symptoms at some point in time (including those non-RBD patients that reported occurrence of RBD symptoms in the past) and those who did not (RBDS and non-RBDS, respectively). We assessed 75 patients. Forty-one (55%) patients presented with RBD, 19 beginning before PD onset. Five non-RBD patients reported having had RBD symptoms in the past. There were no significant differences between RBD and non-RBD patients. RBDS group presented a significantly higher proportion of non-tremor motor sub-type compared to non-RBDS patients. Our results suggest that RBD is very frequent in the early stages of PD. In some patients, RBD symptoms could have disappeared before or in the first years after motor disturbance onset. Non-tremor motor sub-type was related to RBD symptoms history, rather than to the presence of RBD clinical criteria at time of evaluation, suggesting that the physiopathological changes that cause the association with motor status could remain, in spite of symptom fluctuation.