[Sleep behavior disorder (RBD) in synucleionopaties]

Abstract

REM sleep behavior disorder (RBD) is parasomnia characterized by violent movements and an increased motor activity during REM sleep that may be either idiopathic or coupled with neurodegenerative disorders. A clinical-pathologic experience reveals that, save for dementia and Parkinsonism, 97% of RBD patients exhibited the existence of Lewy bodies that defined this parasomnia as being the specificum of synucleinopathies. Parkinson's disease patients had established RBD prevalence in 33%-60% and subclinical RBD in 58% of the referred patient group. The prevalence in patients with multiple system atrophy and diffuse Lewy body disease was 90% and 50%-80% respectively. RBD appears in 0.5% in the form of an idiopathic disorder but the number of those asking for medical support is 10-fold lower. Individual case study of the patients suffering from degenerative diseases, falling within the group of tauopathies with RBD records, induced the analysis of a possible clinical differences, revealing that patients with underlying synucleinopathies, commonly develop RBD prior to motor or cognitive disorders related to their main disease; patients with tauopathies reflect tendency to develop RBD either jointly with or following the development of Parkinson's disease. The difference has been reasoned by selective sensitivity in key structures of brainstem in synucleinopathies blamed for RBD incidence, whilst the referred were less damaged in tauopathies and other degenerative diseases. In fact, the system of atonia is considered to be more susceptible to alpha-synuclein deposits than to tau proteins. Interestingly enough, 17.8% of Parkinson's patients experience RBD prior to Parkinsonism onset; further screening revealed that 38% of the patients are to develop Parkinsonism in some later period, ranging in the interval from 3.7 +/- 1.4 years. The percentage is to rise to 45%-65% later, throughout the period from 5 to 15 years. Subject to the theory of Braak et al (2003), the spread of Parkinson's disease, may serve as an explanation for RBD that is an initial "preclinical symptom" of synucleinopathies, principally in Parkinson's disease. According to Braak, there is an evident pathoanatomic similarity between RBD and Parkinson's disease in 1st-2nd stage. Namely, Braak stage 2 involves key areas controlling sleep and movements of bulbus so that RBD patients may be the ones exhibiting preclinical alpha-synucleinopathy.

Conclusion: RBD is a parasomnia occurring as the consequence of brainstem damage and typical marker of synucleinopathies. Synuclein deposits exhibit a special affinity for atonia; Braak's theory of Parkinson's disease spreading indicates that this very region is actually damaged in stage 2. Pathomorphological similarity between RBD and stage 2 of Parkinson's disease thus recognizes RBD as a hallway to Parkinson's disease-the point getting screening-studies support.