Is a computed tomography (CT) head or magnetic resonance imaging (MRI) head with or without contrast better for migraine evaluation?

MRI Without Contrast is Superior to CT for Migraine Evaluation

MRI without contrast is the preferred imaging modality for migraine evaluation, as it provides superior soft tissue resolution and better detection of relevant abnormalities without radiation exposure. 1

Imaging Indications for Migraines

Neuroimaging is generally not indicated for typical migraine presentations with normal neurological examinations. However, imaging may be warranted when specific red flags are present:

• Sudden severe (thunderclap) headache
• Abnormal neurological signs or symptoms
• Headache with persistent vomiting
• Progressive or worsening pattern of headache
• Positional headache
• Immunocompromised state
• History of cancer
• New onset headache in patients over 50 years old
• Pregnancy with atypical headache features 1

MRI vs CT Comparison for Migraine Evaluation

MRI Advantages

• Higher sensitivity for detecting parenchymal abnormalities
• Superior soft tissue resolution
• No radiation exposure
• Better detection of subtle abnormalities that may be missed on CT
• Can detect small bright foci on T2-weighted images that are undetectable on CT 2
• More sensitive for detecting early ischemic changes, which is relevant as 70% of missed stroke diagnoses present with altered mental status 3

CT Limitations

• Less sensitive for detecting parenchymal abnormalities
• Radiation exposure
• Inferior soft tissue contrast compared to MRI 3
• May miss small lesions that are detectable on MRI 2

Contrast vs No Contrast

For initial migraine evaluation, MRI without contrast is typically sufficient 1. Contrast should only be added if:

• Abnormalities are found on the non-contrast scan
• There is suspicion of infection
• There is concern for a mass lesion
• Inflammatory conditions are suspected 3, 1

Clinical Evidence

Research has demonstrated the superiority of MRI over CT in migraine evaluation. In one study of 74 patients with classic migraine, 26% had multiple foci of bright signal in the brain on T2-weighted MRI that were not detected on CT scans 2. This highlights MRI's superior sensitivity for detecting subtle abnormalities that may be relevant to migraine pathophysiology.

Special Considerations

• For suspected vascular abnormalities (aneurysm, AVM), MRA should be added to the MRI protocol 1
• For suspected venous sinus thrombosis, MRV should be considered 1
• In emergency settings where rapid assessment is needed (e.g., thunderclap headache with concern for subarachnoid hemorrhage), CT may be appropriate as an initial test due to its speed and availability, but MRI remains superior for comprehensive evaluation 3, 4

Pitfalls to Avoid

1. Overimaging: The yield of neuroimaging in patients with typical migraine features and normal neurological examinations is extremely low 1, 5

2. Misinterpreting incidental findings: MRI may detect incidental abnormalities unrelated to headaches that could lead to unnecessary anxiety and additional testing 5, 6

3. Relying on CT alone: CT may miss subtle abnormalities that could be relevant to migraine pathophysiology 2

4. Using contrast unnecessarily: For initial evaluation, non-contrast MRI is typically sufficient unless specific indications for contrast exist 1

In conclusion, when imaging is clinically indicated for migraine evaluation, MRI without contrast is the preferred modality due to its superior sensitivity and lack of radiation exposure. CT should be reserved for emergency situations or when MRI is contraindicated.