REM Sleep Behavior Disorder (RBD) as a marker of neurodegenerative disorders.

Rapid eye movement (REM) sleep behavior disorder (RBD) can occur in the absence of any other obvious associated neurologic disorder or in association with a neurodegenerative disease, in which case it is considered as symptomatic RBD. RBD is frequently associated with Parkinson's disease (PD), Lewy body dementia or multiple system atrophy (MSA), and in several cases may even antedate the occurrence of motor symptoms by decades. When no neurologic disorder is obvious, RBD can be considered as idiopathic (iRBD). Several studies have looked at neurophysiologic and neuropsychological functions in iRBD and have found evidence of CNS dysfunction during both wakefulness and sleep in a variable proportion of these patients, challenging the concept of iRBD. Identifying subjects with a high risk of developing a neurodegenerative process may be crucial in order to develop early intervention strategies. Some prospective results in iRBD showed that potential markers of neurodegeneration are the following: 1) marked EEG slowing on spectral analysis; 2) decreased striatal 123I-FPCIT; 3) impaired color vision.