What are the diagnostic tests for headaches?

Diagnostic Tests for Headache

Neuroimaging (CT or MRI) is only indicated for headache when red flags are present, with CT without contrast preferred for suspected intracranial hemorrhage and MRI preferred for most other concerning causes. 1

Red Flags Requiring Diagnostic Testing

The following red flags should prompt consideration of diagnostic testing:

• Abnormal neurological examination findings (significantly increases likelihood of intracranial abnormality) 2
• Thunderclap headache (sudden or abrupt onset) 1, 3
• New onset after age 50 1, 3
• Progressively worsening headache pattern 1
• Headache awakening patient from sleep 2, 1
• Headache worsened by Valsalva maneuver 2, 1
• Associated fever or neck stiffness 1, 3
• Focal neurological deficits 1, 3
• Papilledema on examination 1, 3
• Recent head or neck trauma 1
• History of cancer or immunocompromised state 1, 3
• Systemic symptoms 1
• Onset during pregnancy or postpartum 1
• Headache precipitated by exertion, sexual activity 1, 4

Neuroimaging Selection Algorithm

1. CT without contrast:

   • First choice for suspected intracranial hemorrhage 1
   • When immediate results are needed
   • For patients who cannot undergo MRI

2. MRI:

   • Preferred for most other concerning causes of headache 1
   • Better visualization of posterior fossa, brain stem, and vascular abnormalities
   • Higher sensitivity for detecting small lesions

Additional Diagnostic Tests

Based on clinical suspicion, the following tests may be indicated:

• Blood tests:

  • Complete blood count, metabolic panel, ESR/CRP for suspected systemic conditions 1
  • Thyroid function tests for suspected endocrine disorders

• Lumbar puncture:

  • Indicated for suspected meningitis 1
  • For suspected subarachnoid hemorrhage when CT is negative but clinical suspicion remains high
  • CSF analysis for cell count, protein, glucose, culture, opening pressure

• Sleep study:

  • For suspected sleep apnea in patients with morning headaches 1

Common Pitfalls to Avoid

• Overuse of neuroimaging when red flags are absent leads to unnecessary radiation exposure and costs 1
• Failure to recognize dangerous secondary causes by not properly assessing red flags 1
• Misdiagnosing migraine as sinus headache (recurrent "sinus headaches" are often migraines) 1
• Inadequate documentation of headache patterns 1

Evidence Quality Considerations

The American College of Radiology and American Academy of Neurology provide the most recent and highest quality guidance on neuroimaging for headache 1. The recommendations emphasize that neuroimaging should be reserved for patients with red flags, as the yield of significant findings in patients with normal neurological examinations and no red flags is very low.

The 2025 Praxis Medical Insights guidelines represent the most current and comprehensive approach to headache evaluation 1, while the older Headache Consortium guidelines from 2000 2 provide supporting evidence for the importance of abnormal neurological examination findings as a predictor of intracranial abnormalities.