Differential diagnosis of headache

1. Big picture

Headache is one of the most common symptoms in medicine, but the exam logic is simple:

First decide: primary headache or secondary dangerous headache.

Primary headache is painful but usually not life-threatening. Secondary headache may indicate subarachnoid hemorrhage, meningitis, stroke, intracranial tumor, raised intracranial pressure, hypertensive emergency, temporal arteritis, glaucoma, sinusitis, or drug/toxin effect.

The safest clinical algorithm:

ABC if unstable → check red flags → neurological examination → decide if urgent imaging/lumbar puncture is needed → then classify the headache pattern.