Is it best to perform an MRI of the brain and neck with or without contrast in a patient presenting with decreased sensation in the left arm and leg, upper back pain, and a normal CT head, for suspected stroke?

MRI Brain and Neck Imaging for Suspected Stroke

For this patient with unilateral sensory deficits and upper back pain, obtain MRI brain WITHOUT and WITH contrast, combined with MRA head and neck (noncontrast head MRA plus contrast-enhanced neck MRA). This approach provides optimal evaluation for both ischemic stroke and alternative diagnoses that could explain the presentation.

Recommended Imaging Protocol

Brain Imaging

• MRI brain without and with IV contrast receives the highest rating (9/9) from the American College of Radiology for TIA/stroke evaluation 1
• The contrast-enhanced sequences help determine infarct age and evaluate alternative etiologies such as inflammatory conditions, infection, or neoplasm that may mimic stroke 1
• MRI brain without contrast alone is rated 8/9 and remains highly appropriate if contrast is contraindicated 1
• MRI is significantly more sensitive than CT for detecting acute infarction 1

Vascular Imaging

• MRA head and neck without and with IV contrast is rated 8/9 for suspected stroke workup 1
• The preferred protocol combines noncontrast head MRA with contrast-enhanced neck MRA 1
• This combination evaluates for large vessel occlusion, arterial dissection (particularly relevant given upper back pain), and extracranial vascular pathology 1
• Noncontrast MRA alone (rated 8/9) remains highly appropriate if contrast cannot be administered 1

Clinical Reasoning

Why Contrast Matters in This Case

• The combination of sensory deficits with upper back pain raises concern for vertebral artery dissection, which may show enhancement of the vessel wall 1
• Contrast helps differentiate acute from chronic infarction and identifies inflammatory or infectious etiologies 1
• For neck vessels specifically, contrast-enhanced MRA reduces overestimation of stenosis severity that can occur with noncontrast techniques 1

Alternative Considerations

• If MRI is unavailable or contraindicated, CTA head and neck with IV contrast (rated 8/9) provides rapid vascular assessment 1
• The 2024 ACR guidelines emphasize that CTA offers the most rapid assessment for large vessel occlusion in acute stroke settings 1
• However, given the normal CT head and ability to obtain MRI per neurology's request, MRI remains superior for detecting subtle infarction 1

Key Clinical Pitfalls

Don't Miss These Diagnoses

• Vertebral artery dissection: Upper back pain is a red flag that necessitates careful vascular imaging of the neck 1
• Spinal cord pathology: While brain imaging is appropriate given the presentation, consider that upper back pain with bilateral limb involvement could indicate cord pathology 2
• Posterior circulation stroke: Sensory symptoms with back pain may indicate vertebrobasilar territory involvement, which MRI detects far better than CT 1, 3

Technical Considerations

• Ensure diffusion-weighted imaging (DWI) is included, as it's the most sensitive sequence for acute infarction 3
• Time-of-flight (TOF) MRA without contrast has high sensitivity for large vessel occlusion but may overestimate stenosis severity 1
• Perfusion imaging (rated 5/9) is not routinely necessary unless considering thrombolysis candidacy 1, 4

When Contrast Should Be Avoided

• Severe renal insufficiency (eGFR <30) due to gadolinium-associated risks 1
• Previous severe allergic reaction to gadolinium-based contrast 1
• In these situations, noncontrast MRI brain plus noncontrast MRA head and neck (both rated 8/9) provides excellent diagnostic information 1