When and how to investigate the patient with headache

The common complaint of headache usually has a benign cause, most often a primary headache syndrome. The history and neurologic and general physical examinations usually permit a definitive diagnosis. When in doubt, diagnostic testing is indicated. Certain historical and examination findings increase the likelihood of a secondary headache disorder and the need for diagnostic testing. These include (1) recent head or neck injury; (2) a new, worse, worsening, or abrupt onset headache; (3) headache brought on by Valsalva maneuver or cough; (4) headache brought on by exertion; (5) headache associated with sexual activity; (6) pregnancy; (7) headache in the patient over the age of ~50; (8) neurologic findings and/or symptoms; (9) systemic signs and/or symptoms; (10) secondary risk factors, such as cancer or human immunodeficiency virus (HIV) infection. Less worrisome are headaches that wake the patient from sleep at night, always occur on the same side, or show a prominent effect of change in posture on the patient's pain. Diagnostic studies include neuroimaging, cerebrospinal fluid (CSF) examination, and blood tests, which are selected depending on the patient's history and findings. For most patients, the diagnostic test of choice is a magnetic resonance imaging (MRI) brain scan. Computed tomography (CT) of the brain is usually obtained in the setting of trauma or the abrupt onset of headache. CSF examination is useful in diagnosing subarachnoid bleeding, infection, and high and low CSF pressure syndromes.