Box 2: Recommendations for imaging for headache2^,4^,5^,8^,9

Red flags	Suggested tests
New onset of a headache in a patient with a history of cancer or immunodeficiency4	Enhanced MRI or contrast-enhanced CT5
New neurologic deficit4	Noncontrast CT2,5
Rapidly increasing frequency and severity of headache; thunderclap onset; headache causing the patient to wake from sleep4	Noncontrast CT; consider CT angiogram in cases of thunderclap onset to rule out aneurysm2,5,8
First-degree relative with known aneurysm or subarachnoid hemorrhage8	Consider CT or MR angiogram to rule out aneurysm8
Associated dizziness, lack of coordination, tingling or numbness4	Consider CT or MRI including angiogram to rule out dissection or vascular insufficiency2,5
Headache associated with sexual activity, orgasmic type with thunderclap onset (nonacute)9	Consider CT or MRI including angiogram to rule out aneurysm or dissection2,9