What are the red flags for migraines?

Red Flags for Migraines

When evaluating a patient with suspected migraine, you must immediately identify red flag features that suggest a dangerous secondary headache disorder requiring urgent investigation, as these can indicate life-threatening conditions such as subarachnoid hemorrhage, intracranial mass, or meningitis.

Critical Historical Red Flags

Acute Onset Features

• Thunderclap headache (sudden onset reaching maximum intensity within seconds to minutes) suggests subarachnoid hemorrhage and requires immediate CT imaging 1, 2, 3
• "Worst headache of life" with abrupt onset indicates serious vascular pathology 1, 2
• The Ottawa SAH Rule mandates investigation for subarachnoid hemorrhage in alert patients >15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour if any of the following are present: age ≥40 years, neck pain/stiffness, witnessed loss of consciousness, onset during exertion, thunderclap headache, or limited neck flexion 1

Pattern Change Features

• Marked change in headache pattern (significant alteration in previously stable headache characteristics) requires investigation for secondary causes 1, 2, 3
• Progressive headache that worsens over time suggests an intracranial space-occupying lesion 1, 2
• New headache onset after age 50 raises concern for temporal arteritis or other secondary causes 1, 2, 3

Provocative Features

• Headache aggravated by Valsalva maneuvers (coughing, sneezing, exercise) indicates possible increased intracranial pressure or space-occupying lesion 1, 2, 3, 4
• Headache awakening patient from sleep may indicate increased intracranial pressure 1, 2
• Headache brought on by exertion warrants evaluation 1, 4

Associated Historical Features

• Persistent headache following head trauma suggests intracranial injury including subdural hematoma 1, 2, 3
• Headache with weight loss and/or change in memory or personality indicates secondary headache, possibly malignancy 1, 2
• Atypical aura (not following typical migraine aura characteristics) may indicate transient ischemic attack, stroke, epilepsy, or arteriovenous malformations 1, 2

Critical Physical Examination Red Flags

Neurological Signs

• Focal neurological symptoms or signs suggest secondary headache and require urgent evaluation 1, 2, 3, 5
• Papilledema indicates increased intracranial pressure 3, 5
• Uncoordination may indicate cerebellar pathology 1, 2, 3
• Impaired memory and/or altered consciousness or personality suggests secondary headache 1, 2

Meningeal Signs

• Neck stiffness is a possible indicator of meningitis or subarachnoid hemorrhage 1, 2, 5
• Limited neck flexion on examination is part of the Ottawa SAH Rule criteria 1
• Unexplained fever may indicate meningitis 1, 2

Diagnostic Approach When Red Flags Are Present

Imaging Strategy

• Neuroimaging is mandatory when red flags are present to rule out secondary causes 1, 2, 3
• MRI is preferred over CT due to higher resolution and absence of radiation exposure for most secondary headache evaluations 1, 2
• CT without contrast is recommended when acute intracranial hemorrhage is suspected 1, 2

Specific Protocols for Suspected Subarachnoid Hemorrhage

• For patients presenting >6 hours from symptom onset or with new neurological deficit: perform noncontrast head CT and, if negative, proceed to lumbar puncture 1
• For patients presenting <6 hours from symptom onset without new neurological deficit: noncontrast head CT on a high-quality scanner interpreted by a board-certified neuroradiologist is reasonable 1

Critical Pitfall to Avoid

Do not rely solely on neuroimaging without considering the complete clinical picture, as this is a common error that can lead to missed diagnoses 1. Conversely, overlooking the need for neuroimaging when red flags are present significantly worsens morbidity and mortality 2, 6.

Context: Distinguishing from Typical Migraine

Typical migraine features include recurrent headache attacks lasting 4-72 hours, unilateral location, pulsating quality, moderate to severe intensity, aggravation by routine physical activity, and associated symptoms like nausea, vomiting, photophobia, and phonophobia 7, 3. A preexisting migraine diagnosis does not exclude a secondary headache disorder - patients with known migraine can still develop dangerous secondary causes 6.