What MRI findings contribute to the diagnosis of a patient with dizziness on standing, difficulty maintaining balance, uncontrolled urination, and rigidity of the upper and lower limbs?

MRI Findings in Multiple System Atrophy (MSA)

The clinical presentation of orthostatic dizziness, balance difficulty, urinary incontinence, and limb rigidity without olfactory or memory deficits strongly suggests Multiple System Atrophy (MSA), and the characteristic MRI findings include putaminal atrophy with T2 hyperintensity, the "hot cross bun" sign in the pons, and cerebellar/pontine atrophy. 1

Clinical Reasoning for MSA Diagnosis

The constellation of symptoms points away from idiopathic Parkinson's disease and toward an atypical Parkinsonian syndrome:

• 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

• Absence of olfactory complaints helps distinguish this from idiopathic Parkinson's disease, where early olfactory system involvement with Lewy body deposition is characteristic 1

• Absence of memory disorders argues against corticobasal degeneration (CBD), which presents with cortical features including dementia and apraxia 1

• Balance difficulty with rigidity reflects the combination of cerebellar ataxia and extrapyramidal symptoms that characterizes MSA 1

Specific MRI Findings for MSA

Putaminal Changes

• Putaminal atrophy with T2 hyperintensity is the most characteristic finding in MSA-P (striatonigral degeneration subtype) where Parkinsonian features predominate 1
• The putaminal rim sign (hypointense lateral rim on T2) may be visible 1

Pontine and Cerebellar Changes

• "Hot cross bun" sign - cruciform T2 hyperintensity in the pons - is highly specific for MSA-C (olivopontocerebellar atrophy subtype) where cerebellar symptoms predominate 1
• Pontine and cerebellar atrophy with associated T2 signal changes in the middle cerebellar peduncles 1

Middle Cerebellar Peduncle Signal Changes

• T2 hyperintensity in the middle cerebellar peduncles reflects olivopontocerebellar degeneration 1

Imaging Modality Recommendations

MRI without contrast is 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

• CT has limited soft-tissue characterization compared to MRI and is not preferred for workup of Parkinsonian syndromes, though it can demonstrate patterns of regional volume loss 1

• Contrast administration is typically not indicated unless there is concern for inflammatory or neoplastic causes 1, 2

Common Diagnostic Pitfalls

• Do not mistake this for idiopathic Parkinson's disease based solely on rigidity - the prominent autonomic dysfunction (orthostatic hypotension causing dizziness, urinary incontinence) and absence of olfactory symptoms point to MSA 1

• Progressive supranuclear palsy (PSP) typically presents with vertical supranuclear gaze palsy and unexplained falls with axial dystonia, which are not described in this case 1

• Correctly diagnosing Parkinsonian syndromes on clinical features alone is challenging, making MRI an essential diagnostic tool 1