Abstract
A higher frequency of motor and breathing sleep-related disorders in multiple system atrophy (MSA) populations is reported. REM sleep behaviour disorder (RBD) is one of the most robust markers of an underlying alpha-synucleinopathy. Although a large corpus of literature documented the higher prevalence of RBD in MSA, few studies have systematically investigated the prevalence of RBD as mode of disease onset and its role in disease progression. Moreover, there has been increasing interest in phenoconversion into synucleinopathies of cohorts of patients with isolated RBD (iRBD). Finally, some studies investigated RBD as predictive factor of conversion in isolated autonomic failure, a synucleinopathy presenting with autonomic failure as the sole clinical manifestation that could convert to a manifest central nervous system synucleinopathy. As the field of neurodegenerative disorders moves increasingly towards developing disease-modifying therapies, detecting individuals in the prodromal stage of these synucleinopathies becomes crucial. The aims of this review are to summarise (1) the prevalence of RBD during the course of MSA and as presenting feature of MSA (iRBD), (2) the RBD features in MSA, (3) MSA progression and prognosis in the subgroup of patients with RBD predating disease onset, and (4) the prevalence of MSA conversion in iRBD cohorts. Moreover, we summarise previous results on the role of RBD in the context of isolated autonomic failure as marker of phenoconversion to other synucleinopathies and, in particular, to MSA.
Highlights
Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterised by a heterogeneous combination of autonomic failure, cerebellar syndrome, parkinsonian features poorly responsive to levodopa, and pyramidal signs [1].The diagnostic criteria define three degrees of certainty for diagnosis and two phenotypes: parkinsonian (MSA-P) or cerebellar (MSA-C), according to the predominant feature at the time of evaluation [1]
Prevalence of REM sleep behaviour disorder (RBD) as first symptom of disease onset ranged from 10 to 60.0% when calculated in overall multiple system atrophy (MSA) samples and from 21.4 to 63.6% when calculated only in MSA patients with RBD (Table 2)
RBD is a key feature of MSA, playing a role in the presentation, prognosis, and progression of disease
Summary
Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterised by a heterogeneous combination of autonomic failure, cerebellar syndrome, parkinsonian features poorly responsive to levodopa, and pyramidal signs [1]. A meta-analysis performed in 2015 on 13 studies reported a summary prevalence of clinically suspected RBD in MSA ranging from 25 to 100%, with a summary prevalence of 73% (95% confidence interval [CI] = 62–84%) in a pooled sample of 324 patients. Prevalence of RBD as first symptom of disease onset ranged from 10 to 60.0% when calculated in overall MSA samples and from 21.4 to 63.6% when calculated only in MSA patients with RBD (Table 2) This variability in results may be a consequence of the differences in study design, sample size,
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