Multiple system atrophy (MSA) is a rare sporadic progressive neurological disorder characterized by a varying combination of symptoms and signs. Onset is during adulthood (>30 years). Affected individuals may experience symptoms similar to those found in Parkinson’s disease (parkinsonism); cerebellar signs such as progressive impairment of the ability to coordinate voluntary movements (cerebellar ataxia); and impaired functioning of the portion of the nervous system (autonomic nervous system) that regulates certain involuntary body functions (autonomic failure) such as heart rate, blood pressure, sweating, and bowel and bladder control. When parkinsonian symptoms predominate, the disorder may be referred to as MSA-P (parkinsonian phenotype); when the cerebellar symptoms predominate the disorder may be referred to as MSA-C (cerebellar phenotype). The exact cause of MSA is unknown.
The term multiple system atrophy was first introduced in the medical literature in 1969. It encompasses three presentations of a single disease formerly thought to be separate disorders, specifically Shy-Drager syndrome (which emphasized autonomic dysfunction), striatonigral degeneration (which emphasized parkinsonian symptoms), and sporadic olivopontocerebellar atrophy (which emphasized cerebellar symptoms), although the cases of each of these that were originally described presented a combination of all three clinical features, and brain pathology was found in both the striatonigral and olivopontocerebellar structures. Additionally, there is a hereditary form of olivopontocerebellar atrophy that is not part of the multiple system atrophy spectrum.