What are the American Academy of Neurology (AAN) guidelines for brain imaging in a patient presenting with headaches?

AAN Guidelines for Brain Imaging in Headache Patients

Routine neuroimaging is not recommended for patients with non-acute headache who have a normal neurological examination and no red flag features, as the yield of significant abnormalities (0.2-0.5%) is no higher than in asymptomatic individuals (0.4%). 1, 2

Core Principle: Risk-Based Imaging Strategy

The American Academy of Neurology guidelines emphasize that neuroimaging should only be performed when:

• The patient has a significantly higher probability of abnormality than the general population 1
• The imaging results would actually change clinical management 1

When Neuroimaging Is NOT Indicated

Do not image patients with typical primary headache patterns and normal neurological examinations:

• Migraine with normal exam: Only 0.2% (2/1086) show serious abnormalities—identical to asymptomatic volunteers 1, 2
• Tension-type headache with normal exam: 0% (0/83) show serious abnormalities 1, 2
• Chronic headache (undefined type) with normal exam: 0.5% show abnormalities 1

Red Flags Requiring Neuroimaging

Image immediately when any of these features are present:

High-Priority Red Flags

• Thunderclap or abrupt onset of severe headache (subarachnoid hemorrhage concern) 1, 3, 4
• Headache awakening patient from sleep (increased intracranial pressure) 1, 2, 3
• Rapidly increasing headache frequency over weeks 1, 2, 5
• Focal neurologic signs or symptoms on examination 1, 4
• Papilledema 4, 6

Additional Red Flags

• History of uncoordination 1
• Persistent headache following head trauma 1, 4
• Marked change in established headache pattern 1
• Headache worsened by Valsalva maneuver (increased intracranial pressure) 3
• Positional headache 4
• New headache in patients ≥50 years old (temporal arteritis concern) 4, 7

Special Populations Requiring Lower Threshold for Imaging

• Immunocompromised patients 4, 7
• Cancer patients 4, 7
• Pregnant patients 4, 7
• Patients with hypercoagulable disorders 4

Atypical Presentations Requiring Imaging

Image when headache characteristics deviate from typical primary headache patterns:

• Atypical migraine aura: Visual aura lasting >60 minutes (typical aura: 5-60 minutes) 5
• Motor symptoms persisting >72 hours 5
• Cough, exertion, or sexual activity-triggered headaches (require MRI before diagnosing as primary) 4
• Trigeminal autonomic cephalalgias 4, 7

Imaging Modality Selection

MRI without contrast is the preferred modality for non-acute evaluation:

• Superior for detecting: Soft tissue abnormalities, inflammatory processes, demyelinating diseases, small infarcts, masses, and vascular malformations 2, 5, 3
• MRI with and without contrast: Use when red flags present or atypical features 2, 5, 3

CT without contrast is reserved for:

• Acute presentations requiring immediate hemorrhage exclusion 3, 6
• Emergency settings 6

MRI with diffusion-weighted imaging (DWI):

• Preferred for suspected posterior circulation stroke (can present with isolated visual symptoms) 5

Common Pitfalls to Avoid

• Do not dismiss sleep-related headache as benign even with normal examination—this is a specific red flag 3
• Do not confuse photophobia with a red flag—it is an expected migraine symptom 3
• Do not over-image typical migraine with normal examination when red flags are absent 3
• Do not rely solely on treatment response to determine imaging need—analgesic failure alone is not an indication 3
• Recognize that false positive findings are more likely than true positives in low-risk patients, potentially leading to harmful cascades of unnecessary procedures 1

What Neuroimaging Does NOT Include

Electroencephalography (EEG) is not useful in routine headache evaluation unless seizure disorder, atypical migrainous aura, or episodic loss of consciousness is suspected 1