MRI Brain Findings in Persistent Headache
In a previously healthy adult with persistent headache and normal neurological examination, brain MRI will most likely be completely normal or show only clinically insignificant white matter abnormalities, with serious pathology detected in only 0.2-0.4% of cases—no higher than the general asymptomatic population. 1
Expected Normal or Benign Findings
The overwhelming majority (>96%) of brain MRIs in patients with persistent headache and normal neurological examination will show either:
- Completely normal brain imaging 2, 1
- Incidental white matter abnormalities that are clinically insignificant, occurring in approximately 33% of chronic headache patients (predominantly in frontal regions) 3
- Minor structural variations with no pathological relevance or causal relationship to the headache 4
The yield of clinically significant findings in typical migraine or tension-type headache with completely normal neurological examination is equivalent to scanning asymptomatic volunteers—approximately 0.2% for migraine patients and 0% for tension-type headache patients 2, 1.
When Serious Pathology May Be Detected
Serious abnormalities are found in only 3.7% of all chronic headache patients referred for imaging, but this increases substantially to 14.1% in those with atypical headache features 5. The presence of specific red flags dramatically changes the pre-test probability:
Red Flag Features Requiring Imaging:
- Headache worsened by Valsalva maneuver 1, 6
- Headache that awakens patient from sleep 1, 6
- New-onset headache in older patients 1, 6
- Progressively worsening headache over weeks 1, 6
- Rapid increase in headache frequency 1, 6
- Abnormal neurological examination findings 2, 1
Specific Pathological Findings That May Be Detected
When serious abnormalities are present, MRI may reveal:
Structural Lesions:
- Brain tumors or metastases (though 94% of patients with brain tumors causing headache have abnormal neurological findings at diagnosis) 1
- Hydrocephalus or mass lesions causing increased intracranial pressure 6
- Chiari I malformation (particularly with occipital headache worsened by Valsalva) 6
Vascular Abnormalities:
Inflammatory/Infectious Processes:
Intracranial Hypotension:
- Diffuse pachymeningeal enhancement (abnormal dural-meningeal enhancement) 9
- Dural venous sinus enhancement suggesting compensatory venous expansion 9
Critical Clinical Decision Points
Testing should be avoided if it will not lead to a change in management and if the patient is not significantly more likely than the general population to have a clinically important abnormality 2, 1.
When MRI Is NOT Indicated:
- Typical migraine with normal neurological examination 1
- Tension-type headache with normal neurological examination 2
- Chronic headache without red flag features 2, 4
When MRI IS Indicated:
- Any abnormal neurological examination finding 2, 1
- Atypical headache pattern (14.1% yield of major abnormalities) 5
- Presence of any red flag features listed above 1, 6
- Seizures accompanying headache 2, 1
Common Pitfalls to Avoid
- Assuming severe headache is "just migraine" without proper evaluation, especially with occipital location or red flag features 6
- Ordering CT when MRI is appropriate, as CT misses the majority of structural lesions responsible for secondary headache 1
- Skipping the neurological examination, as this is the most important predictor of whether imaging will reveal pathology 1
- Misdiagnosing migraine as "sinus headache" and ordering unnecessary imaging 1
MRI Protocol Recommendations
When imaging is indicated, the American College of Radiology recommends MRI brain without IV contrast as the initial study, including: 1, 6
- T1-weighted sequences
- T2-weighted sequences
- FLAIR sequences
- Diffusion-weighted imaging for stroke evaluation
Contrast should be added only if the non-contrast study reveals abnormalities requiring further characterization 1.