In clinical practice parkinsonian features associated with MSA need to be distinguished from Parkinson´s disease (PD) as well as other atypical parkinsonian disorders.
Recognition of typical disease manifestations will facilitate a correct clinical diagnosis in many instances. In contrast to atypical parkinsonian disorders including MSA-P, patients with PD usually exhibit a beneficial response to chronic L-dopa therapy which then usually becomes complicated by motor fluctuations and dyskinesias. Although patients with PD and MSA-P may both develop orthostatic and urogenital disturbances, these frequently manifest early in MSA-P and late in PD. Early unexplained falls combined with vertical gaze palsy represent cardinal features of PSP. Patients with CBD typically develop an asymmetrical extrapyramidal syndrome comprising bradykinesia, rigidity, dystonic posturing and superimposed myoclonus. In addition there is prominent cortical dysfunction, predominantly ideomotor apraxia. Progressive cognitive decline associated with marked fluctuation of attention and vigilance as well as visual hallucinations characterize the dementia syndrome of patients with DLB, a substantial proportion of whom develop additional parkinsonian features. The differential diagnosis of MSA-C includes other adult onset cerebellar ataxias. Principally, molecular genetic testing for spinocerebellar ataxia type 1 (SCA1) and type 2 (SCA2) should exclude those hereditary ataxias associated with OPCA-like pathology, and testing for SCA 6 those with a pure cerebellar syndrome although such testing is not usually necessary. Early presence of autonomic and urogenital dysfunction represent a helpful red flag indicating MSA-C rather than other causes of sporadic OPCA.