REM sleep behavior disorder (RBD) and neurodegeneration

First described by Schenck and collaborators, criteria for RBD are now defined by the ASDA and include complex behaviors during REM sleep with a loss of skeletal muscle atonia. Mild up to harmful body movements are associated with dream mentation and nightmares and disrupt sleep continuity. Polysomnographic evaluation is needed to establish a final diagnosis. RBD most likely reflects dysfunction in the brainstem circuitry and the dorsolateral pontine tegmentum, where REM sleep without atonia can be induced in animal experiments. Recent studies with cohorts of RBD patients point towards the hypothesis that RBD may represent a preclinical marker of a neurodegenerative process in synucleinopathies such as PD and MSA and may precede motor symptoms for years.

Comella and coworkers (1998) reported a frequency of 15% clinically diagnosed RBD in PD patients, whereas Gagnon and coworkers (2002) found, that one third of an unselected population of PD patients revealed RBD when investigated polysomnographically. Only 50% of these patients would have been detected by history only. Neuroimaging studies of patients who presented to the sleep clinic with characteristic complaints of RBD revealed a marked reduction of presynaptic dopamine transporter binding indicating early PD or MSA and a decreased olfactory function (Stiasny-Kolster et al 2006). RBD seems to be especially frequent in those patients with PD and psychosis or hallucinations. It is controversely discussed, if RBD is also a preclinical marker for cognitive decline in Parkinsonism. Clinical observation and video polysomnography is needed to evaluate the extent of RBD and to decide, if a treatment with i.e. clonazepam or melatonin is necessary.

References: [1] American Sleep Disorders Association: International classification of sleep disorders, 2nd revision: diagnostic and coding manual. Rochester: American Sleep Disorders Association; 2005. [2] Comella CL, Nardine TM, DiederichNJ, et al: Sleep-related violence, injury, and REM sleep behavior disorder in Parkinson's disease, Neurology. 1998;51:526–529. [3] Gagnon JF, Bedard MA, Fantini ML, et al: REM sleep behavior disorder and REM sleep without atonia in Parkinson's disease, Neurology. 2002;59:585–589.