Should an MRI with or without contrast be used to evaluate new onset headaches?

MRI for New Onset Headaches: With or Without Contrast?

For new onset headaches, MRI without contrast is the preferred initial imaging study, with contrast added only when specific indications are present such as suspected infection, tumor, or inflammatory conditions.

Initial Imaging Selection for New Onset Headaches

MRI vs. CT

• MRI without contrast is superior to CT for evaluating most causes of headache, particularly for detecting small brain tumors, posterior fossa lesions, and early ischemic changes 1, 2
• CT is primarily indicated in emergency settings where:
  • Rapid assessment is needed
  • Subarachnoid hemorrhage is suspected (98% sensitivity, 99% specificity for acute SAH) 1
  • Patient cannot undergo MRI due to contraindications

When to Add Contrast

Contrast should be added to MRI only in specific circumstances:

• When abnormalities are found on initial non-contrast scan
• Suspicion of infection
• Concern for mass lesion
• Suspected inflammatory conditions 2

Red Flags Requiring Neuroimaging

Imaging is warranted when headaches are accompanied by:

• Sudden severe (thunderclap) onset
• Abnormal neurological examination
• New onset headache in patients over 50 years
• Headache with persistent vomiting
• Immunocompromised state
• History of cancer
• Headache aggravated by exertion or Valsalva maneuver
• Positional headache 1, 2

Yield of Neuroimaging in Headache

• The diagnostic yield of neuroimaging in patients with chronic headache and normal neurological examination is extremely low (approximately 0.9%) 3
• In a study of 306 patients with chronic headache and normal neurological examination, only 0.7% had clinically significant findings on MRI 4
• Neuroimaging for typical primary headache patterns without red flags has a number needed to scan of approximately 61 to find a clinically significant abnormality 2

Special Considerations

Primary vs. Secondary Headaches

• Most primary headaches (migraine, tension-type) can be diagnosed based on history and examination alone 5
• Secondary headaches require investigation for underlying causes, with imaging selection based on suspected etiology

Specific Headache Types

• Cluster headaches have a higher pre-test probability (5%) for intracranial abnormalities and generally require MRI 3
• Trigeminal autonomic cephalalgias generally require MRI evaluation 6

Potential Pitfalls

• Overimaging patients with typical headache patterns can lead to detection of incidental findings that cause unnecessary anxiety and further testing 2
• Neither contrast enhancement nor repeated MRI contributed to diagnosis in patients with chronic headache and normal neurological examination 4
• MRI may reveal clinically insignificant abnormalities in up to 44% of patients with chronic headache 4

Additional Vascular Imaging

Consider adding specialized vascular imaging in specific scenarios:

• MR Angiography (MRA) for suspected vascular abnormalities
• MR Venography (MRV) for suspected venous sinus thrombosis 2
• Contrast-enhanced MRV may be helpful when evaluating areas such as the sigmoid venous sinuses 1

In summary, while MRI without contrast is the preferred initial imaging study for new onset headaches requiring investigation, the decision to image and whether to add contrast should be guided by the presence of red flags and specific clinical suspicions.