Delayed emergence of a parkinsonian disorder in 38% of 29 older men initially diagnosed with idiopathic rapid eye movement sleep behavior disorder

We report longitudinal data on a group of 29 male patients 50 years of age or older who were initially diagnosed as having idiopathic REM sleep behavior disorder (RBD) after extensive polysomnographic and neurologic evaluations. Thirty-eight percent (11/29) were eventually diagnosed as having a parkinsonian disorder (presumably Parkinson's disease) at a mean interval of 3.7 +/- 1.4 (SD) years after the diagnosis of RED, and at a mean interval of 12.7 +/- 7.3 years after the onset of RED. To date, only 7% (2/29) of patients have developed any other neurologic disorder. At the time of RED diagnosis, data from the RED group with eventual Parkinson's disease (n - 11) and the current idiopathic RED group (n = 16) were indistinguishable, with two exceptions: the RBD-Parkinson's disease group had a significantly elevated hourly index of periodic limb movements of non-REM sleep and an elevated REM sleep percentage. RED was fully or substantially controlled with nightly clonazepam treatment in 89% (24/27) of patients in both groups. Thus, RBD can be the heralding manifestation of Parkinson's disease in a substantial subgroup of older male RED patients. However, a number of presumed Parkinson's disease patients may eventually be diagnosed with multiple system atrophy (striatonigral degeneration subtype). Our findings indicate the importance of serial neurologic evaluations after RED is diagnosed and implicate the pedunculopontine nucleus as a likely site of pathology in combined RBD-Parkinson's disease, based on experimental and theoretical considerations rather than on autopsy data.