Should an MRI with contrast be performed to evaluate possible acute stroke and chronic lacunar infarctions?

MRI Without Contrast is Recommended for Acute Stroke Evaluation

For evaluating possible acute stroke and chronic lacunar infarctions in this patient, MRI without contrast is the appropriate imaging modality—contrast administration is not necessary and provides no additional diagnostic benefit for this clinical scenario. 1, 2

Rationale for Non-Contrast MRI

Acute Stroke Detection

• MRI with diffusion-weighted imaging (DWI) without contrast is superior to CT for detecting acute ischemic stroke, with sensitivity of 77% versus 16% for CT in the first 3 hours, and remains superior for up to 12 hours after symptom onset 1, 2
• DWI detects cerebral ischemia within minutes of onset and can differentiate acute from chronic stroke based on temporal evolution of diffusion characteristics 1
• A standardized multimodal MRI protocol (DWI, FLAIR, gradient-echo/SWI) can be completed in approximately 10 minutes without requiring contrast 2

Chronic Lacunar Infarction Evaluation

• MRI without contrast is definitively superior to CT for detecting and characterizing lacunar infarcts, identifying lesions in 74-86% of cases compared to lower CT sensitivity 3, 4
• T2-weighted and FLAIR sequences without contrast readily demonstrate chronic lacunar infarctions as focal areas of increased signal intensity in deep brain structures 1, 4
• T1-weighted sequences are most sensitive for detecting cavitation in chronic lacunar infarcts (94% sensitivity at 90 days), though FLAIR may miss cavitated lesions in the brainstem and thalamus 5

Why Contrast is Not Indicated

Limited Utility in Standard Stroke Imaging

• Guideline consensus states there is insufficient evidence to support MRI with contrast for initial imaging of vascular dementia or stroke evaluation 1
• MRI findings of both acute and chronic ischemic changes "can be depicted without the use of IV contrast material" 1
• The American College of Radiology imaging recommendations for acute stroke do not include contrast-enhanced MRI in their standard protocols 1, 2

Specific Role of Contrast (When It Would Be Used)

• Gadolinium-enhanced MRI is primarily useful for distinguishing recent from remote lacunar infarcts in patients with multiple small infarctions, where recent lesions enhance and chronic ones do not 6
• However, this distinction can typically be made using DWI sequences without contrast, as acute lesions show restricted diffusion 1, 7
• Contrast-enhanced MRA may be performed for vascular imaging, but this is separate from parenchymal brain imaging and should be acquired in the arterial phase to prevent venous contamination 1

Recommended Imaging Protocol

Core Sequences (All Without Contrast)

• DWI: Detects acute ischemia with highest sensitivity 1, 2
• FLAIR: Identifies chronic lacunar infarcts and white matter disease 1
• T2-weighted: Most sensitive for detecting multiple lacunar infarcts 4
• Gradient-echo (GRE) or SWI: Detects microhemorrhages and blood products 1
• T1-weighted: Best for identifying cavitation in chronic lacunar infarcts 5

Additional Vascular Imaging (If Needed)

• MRA without contrast (time-of-flight technique) can assess intracranial vasculature for stenosis or occlusion 1
• This addresses the stroke mechanism evaluation without requiring gadolinium 1, 8

Clinical Caveats

When Contrast Might Be Considered (Rare Scenarios)

• If multiple small infarctions are present and determining which lesion is acute versus chronic would fundamentally change management, gadolinium may help identify enhancing (recent) lesions 6
• However, DWI has largely replaced contrast-enhanced imaging for this purpose in modern practice 7

Addressing the Incidental Finding

• The "nonspecific soft tissue opacification bilateral external auditory canals" noted on CT is unrelated to stroke evaluation and would not influence the decision regarding contrast administration for brain MRI 1
• This finding requires separate clinical otologic evaluation, not contrast-enhanced neuroimaging 1