Progression of multiple system atrophy (MSA): a prospective natural history study by the European MSA Study Group (EMSA SG).

The disease-specific Unified Multiple System Atrophy Rating Scale (UMSARS) has been developed recently and validated for assessing disease severity in multiple system atrophy (MSA). Here, we aimed at (1) assessing rates of disease progression in MSA and (2) validating UMSARS for sensitivity to change over time. Impairment was assessed at two time points 12 months apart using UMSARS Part I (historical review), UMSARS Part II (motor examination), as well as measures of global disease severity, including UMSARS Part IV, Hoehn and Yahr (HY) Parkinson's disease staging, Schwab England Activities of Daily Living (SE ADL), and a three-point global Severity Scale (SS3). Fifty patients (male:female ratio, 1:0.9; possible MSA, 16%; probable MSA, 84%; MSA-parkinsonian, 58%; MSA-cerebellar, 42%) were assessed twice with an interval of 12.3 months. UMSARS II scores progressed by 57.3% (P<0.0001) and UMSARS I scores by 35.6% (P<0.0001) in relation to the respective baseline scores with no differences between motor subtypes, diagnostic categories and gender. Significant inverse correlations between (1) UMSARS I or UMSARS II progression and (2) baseline disability measures (i.e., the respective UMSARS or SS3 scores) and disease duration were found. Furthermore, the increases in HY staging, SE ADL and SS3 correlated significantly with UMSARS I, UMSARS II, and UMSARS IV progression. This report is the first prospective study showing rapid annual UMSARS rates of decline in MSA. Our data contribute to the ongoing validation process of UMSARS, and they facilitate the planning and implementation of future neuroprotective intervention trials.