Exclusion criteria6
| Exclusion criteria | Clinically established/ probable MSA | Possible prodromal MSA | Differential |
| Substantial and persistent beneficial response to dopaminergic medications | ✓ | ✗ | Parkinson’s disease |
| Unexplained anosmia on olfactory testing | ✓ | ✓ | |
| Fluctuating cognition with pronounced variation in attention and alertness and early decline in visuo-perceptual abilities | ✓ | ✓ | Dementia with Lewy bodies |
| Recurrent visual hallucinations not induced by drugs within 3 years of disease onset | ✓ | ✓ | |
| DSM-V Dementia within 3 years of disease onset | ✓ | ✓ | Dementia with Lewy bodies Progressive supranuclear palsy Corticobasal degeneration |
| Downgaze supranuclear palsy/slowing of vertical saccades | ✓ | ✓ | Progressive supranuclear palsy |
| Brain MRI findings suggesting an alternative diagnosis (eg, progressive supranuclear palsy, multiple sclerosis, vascular parkinsonism, symptomatic cerebellar disease) | ✓ | ✓ | |
| Documentation of an alternative condition (MSA look-alike, including genetic or symptomatic ataxia and parkinsonism) known to produce similar symptoms and plausibly connected | ✓ | ✓ |
DSM-V, Diagnostic and Statistical Manual of Mental Disorders; MSA, multiple system atrophy.