MRI Findings in Multiple System Atrophy (MSA)

Clinical Presentation and Diagnosis

The American College of Radiology suggests that the clinical presentation of orthostatic dizziness, balance difficulty, urinary incontinence, and limb rigidity without olfactory or memory deficits strongly suggests Multiple System Atrophy (MSA) 1
Autonomic dysfunction (orthostatic dizziness and urinary incontinence) combined with Parkinsonian features (rigidity) is the hallmark of MSA, particularly the MSA-A subtype (Shy-Drager syndrome) where autonomic dysfunction predominates 1, 2
The absence of olfactory complaints helps distinguish MSA from idiopathic Parkinson's disease, where early olfactory system involvement with Lewy body deposition is characteristic 1, 2
The absence of memory disorders argues against corticobasal degeneration (CBD), which presents with cortical features including dementia and apraxia 1, 2

Putaminal atrophy with T2 hyperintensity is the most characteristic finding in MSA-P (striatonigral degeneration subtype) where Parkinsonian features predominate 1, 2
The "hot cross bun" sign - cruciform T2 hyperintensity in the pons - is highly specific for MSA-C (olivopontocerebellar atrophy subtype) where cerebellar symptoms predominate 1, 2
Pontine and cerebellar atrophy with associated T2 signal changes in the middle cerebellar peduncles are characteristic of MSA 1, 2

The American College of Radiology recommends MRI without contrast as the preferred initial imaging modality for evaluating suspected Parkinsonian syndromes, as it effectively demonstrates patterns of regional volume loss and signal abnormalities characteristic of MSA 1, 2, 3
Contrast administration is typically not indicated unless there is concern for inflammatory or neoplastic causes 4, 3