Would I use a CT (Computed Tomography) of the brain or a CTA (Computed Tomography Angiography) of the brain for a migraine patient?

Neuroimaging for Migraine Patients: CT vs CTA

For a typical migraine patient with normal neurological examination and no red flags, neither CT nor CTA of the brain is indicated as routine neuroimaging is not warranted in these cases. 1, 2

When to Consider Neuroimaging in Migraine

Neuroimaging should only be considered when specific "red flags" are present:

• Abnormal neurological examination findings - strongest indicator for imaging 2, 1
• Sudden severe (thunderclap) headache - may indicate subarachnoid hemorrhage 1
• Atypical features that suggest secondary causes:
  • Headache that awakens patient from sleep
  • Rapidly increasing frequency of headaches
  • Headache worsened by Valsalva maneuver
  • New-onset headache in older patients (>50 years)
  • Progressively worsening headache pattern
  • Positional headache
  • History of cancer or immunocompromised state 1

Choosing Between CT and CTA

If imaging is indicated based on red flags:

1. For typical evaluation with red flags but no vascular concerns:

   • MRI without contrast is the preferred initial imaging modality 1
   • CT may be appropriate as an initial test in emergency settings where rapid assessment is needed 1

2. For suspected vascular abnormalities:

   • CTA should be considered when:
     • Thunderclap headache (sudden severe headache) 3
     • Suspected arterial dissection
     • Suspected reversible cerebral vasoconstriction syndrome (RCVS)
     • Suspected aneurysm 4, 5

3. For suspected venous sinus thrombosis:

   • MR Venography (MRV) is more appropriate than CTA 1

Diagnostic Yield Considerations

• The yield of neuroimaging in primary headache disorders without red flags is extremely low 1
• CTA in patients with acute headache, normal neurological examination, and normal non-contrast CT has a low diagnostic yield (7.4%), with most findings being incidental aneurysms 5
• The number needed to scan with CTA to find a clinically significant abnormality (excluding incidental aneurysms) is approximately 61 5

Common Pitfalls to Avoid

• Overimaging patients with typical migraine and normal neurological examination
• Misinterpreting incidental findings that can cause unnecessary patient anxiety
• Relying on CT alone when MRI would be more appropriate for comprehensive evaluation
• Using contrast unnecessarily when non-contrast imaging would suffice 1

Special Populations

• Pediatric patients with isolated headache or classic migraine without neurological signs generally do not require imaging 3
• Patients over 50 with new-onset headache should be evaluated for temporal arteritis with ESR and CRP before considering neuroimaging 1

Remember that the prevalence of significant intracranial abnormalities is only approximately 0.2% in patients with migraine and normal neurological examination 2, making routine neuroimaging unnecessary and potentially harmful due to incidental findings and radiation exposure.