Select pain quality (throbbing, pressing), location (bilateral, unilateral, occipital), associated symptoms (nausea, photophobia, phonophobia, aura, autonomic signs), and red flags (new onset severe, waking from sleep, focal deficit, papilledema) → differentiate migraine, tension headache, cluster, or secondary headache.
⚠️ Red flags (SNOOP): Systemic symptoms, Neurologic deficit, Onset after 50yr (or <3yr), Onset sudden (thunderclap), Prior headache history change, Positional headache, Precipitated by Valsalva, Papilledema.
Select pain quality (throbbing vs pressing), duration (4‑72h vs minutes to days), location, associated features (nausea/vomiting, photophobia, phonophobia, aura, autonomic signs), and red flags → system applies ICHD‑3 criteria for migraine, tension, cluster, and secondary headaches (sinusitis, pseudotumor, tumor).