Neuroimaging in multiple system atrophy

Multiple system atrophy is an adult-onset, invariably progressing neurodegenerative disorder, clinically characterized by autonomic dysfunction and a variable combination of parkinsonism, cerebellar ataxia, and pyramidal signs. Diagnosis, especially at the disease onset, can be particularly challenging, due to the frequent clinical overlap with Parkinson's disease and other atypical parkinsonisms. Current diagnostic criteria include, as supportive feature for a diagnosis of possible multiple system atrophy, typical brain abnormalities on magnetic resonance imaging, positron emission tomography, or single photon emission tomography. Neuroimaging studies in multiple system atrophy can be crucial in differential diagnosis and may be helpful in revealing pathological changes related to disease progression, potentially aiding to monitor disease and to verify the efficacy of novel therapeutic strategies. In this chapter, we provide a comprehensive overview of the cardinal neuroimaging studies in multiple system atrophy, aiming at identifying markers of disease and progression, characterizing disease-specific clinical subtypes, and supporting differential diagnosis from Parkinson's disease and other parkinsonian disorders.