Multiple system atrophy of the cerebellar type: Clinical state of the art

ABSTRACT Multiple system atrophy (MSA) is a late‐onset, sporadic neurodegenerative disorder clinically characterized by autonomic failure and either poorly levodopa‐responsive parkinsonism or cerebellar ataxia. It is neuropathologically defined by widespread and abundant central nervous system α‐synuclein–positive glial cytoplasmic inclusions and striatonigral and/or olivopontocerebellar neurodegeneration. There are two clinical subtypes of MSA distinguished by the predominant motor features: the parkinsonian variant (MSA‐P) and the cerebellar variant (MSA‐C). Despite recent progress in understanding the pathobiology of MSA, investigations into the symptomatology and natural history of the cerebellar variant of the disease have been limited. MSA‐C presents a unique challenge to both clinicians and researchers alike. A key question is how to distinguish early in the disease course between MSA‐C and other causes of adult‐onset cerebellar ataxia. This is a particularly difficult question, because the clinical framework for conceptualizing and studying sporadic adult‐onset ataxias continues to undergo flux. To date, several investigations have attempted to identify clinical features, imaging, and other biomarkers that may be predictive of MSA‐C. This review presents a clinically oriented overview of our current understanding of MSA‐C with a focus on evidence for distinguishing MSA‐C from other sporadic, adult‐onset ataxias. © 2014 International Parkinson and Movement Disorder Society