What is the preferred imaging modality, MRI (Magnetic Resonance Imaging) brain scan or CT (Computed Tomography) head scan, for diagnosing migraines?

MRI vs CT for Migraine Headaches

Neither MRI nor CT is routinely recommended for patients with migraine headaches who have a normal neurological examination, as both modalities have low diagnostic yield in this population. 1

Neuroimaging Recommendations for Migraine

• Neuroimaging (either MRI or CT) is not usually warranted in patients with migraine who have normal findings on neurological examination (Grade B recommendation) 1
• The prevalence of significant intracranial abnormalities in migraine patients with normal neurological examinations is approximately 0.2%, making routine imaging unnecessary 1
• Brain MRI obtained at the specific request of migraine patients with normal neurological examination results has a yield equivalent to that of the general asymptomatic population 2

When Neuroimaging Should Be Considered

• Neuroimaging should be considered in patients with headache and an unexplained abnormal finding on neurological examination (Grade B recommendation) 1
• A lower threshold for imaging may be appropriate in patients with:
  • Atypical headache features that don't fulfill the definition of migraine 1
  • Headache worsened by Valsalva maneuver 1
  • Headache that awakens the patient from sleep 1
  • New-onset headache in older patients 1
  • Progressively worsening headache 1
  • Rapid increase in headache frequency 1

MRI vs CT Comparison

• Based on limited data, MRI may be more sensitive than CT in identifying clinically insignificant abnormalities, but may be no more sensitive than CT in identifying clinically significant pathology 1
• There is insufficient evidence to make definitive recommendations regarding the comparative sensitivity of MRI and CT (Grade C recommendation) 1
• The greater resolution of MRI appears to be of little clinical importance in the evaluation of non-acute headache 1

Special Considerations

• In emergency settings with suspected subarachnoid hemorrhage, CT without contrast is preferred due to its superior ability to detect acute blood products 1
• For suspected brain tumors in emergency settings, CT without IV contrast can be performed initially, but contrast-enhanced studies may be needed if MRI is not possible 1
• CT is sometimes preferred in acute settings due to its speed and availability, particularly when evaluating for acute conditions 1, 3

Principles for Diagnostic Imaging Decision-Making

The U.S. Headache Consortium advocates three consensus-based principles for diagnostic imaging:

1. Testing should be avoided if it will not lead to a change in management 1
2. Testing is not recommended if the patient is not significantly more likely than the general population to have a significant abnormality 1
3. Testing that is not normally recommended may make sense in individual cases, such as in patients who are excessively worried about serious problems causing their headaches 1

Common Pitfalls to Avoid

• Ordering neuroimaging for reassurance alone may not reduce patient anxiety according to limited evidence 4
• Incidental findings are common (up to 38.5% in some studies) and may lead to unnecessary additional testing and patient anxiety 5
• "Sinus headache" is a common misdiagnosis among migraine sufferers, and neuroimaging is not indicated for this presumptive diagnosis 1
• Overreliance on neuroimaging may delay appropriate migraine-specific treatment and management 2