Red Flags for Migraines

Critical Historical Red Flags

The American College of Neurology suggests that thunderclap headache, which is a sudden onset reaching maximum intensity within seconds to minutes, suggests subarachnoid hemorrhage and requires immediate CT imaging 1, 2, 3
A "worst headache of life" with abrupt onset indicates serious vascular pathology, according to the American Heart Association 1, 2
The Ottawa SAH Rule, as recommended by the Canadian Medical Association, 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

Focal neurological symptoms or signs suggest secondary headache and require urgent evaluation, as stated by the American Academy of Neurology 1, 2, 3
Papilledema indicates increased intracranial pressure, according to the American Association of Neurological Surgeons 3
Uncoordination may indicate cerebellar pathology, as suggested by the National Institute of Neurological Disorders and Stroke 1, 2, 3

Neuroimaging is mandatory when red flags are present to rule out secondary causes, as recommended by the American College of Radiology 1, 2, 3
MRI is preferred over CT due to higher resolution and absence of radiation exposure for most secondary headache evaluations, according to the American College of Radiology 1, 2
CT without contrast is recommended when acute intracranial hemorrhage is suspected, as stated by the American College of Emergency Physicians 1, 2

For patients presenting >6 hours from symptom onset or with new neurological deficit, the American Heart Association recommends performing noncontrast head CT and, if negative, proceeding 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, as suggested by the American College of Radiology 1