Red flags: emergent (address immediately) Thunderclap onset Fever and meningismus Papilledema with focal signs or reduced level of consciousness Acute glaucoma Red flags: urgent (address within hours to days) Temporal arteritis Papilledema without focal signs or reduced level of consciousness Relevant systemic illness Elderly patient: new headache with cognitive change Other possible indicators of secondary headache (less urgent) Unexplained focal signs Atypical headaches (not consistent with migraine or tension-type headache) Unusual headache precipitants Unusual aura symptoms Onset after age 50 y Aggravation by neck movement; abnormal neck examination findings (consider cervicogenic headache) Jaw symptoms; abnormal jaw examination findings (consider temporomandibular joint disorder)

Based on the Scottish Intercollegiate Guidelines Network guideline²⁹ and expert opinion of the Guideline Development Group.