Headache Red Flags — When a Headache Needs Urgent Evaluation

Red flags that change the plan

A red flag does not automatically mean something dangerous is present — it means the usual statistical reassurance no longer applies and targeted evaluation is warranted. The classic framework is SNOOP: Systemic symptoms, Neurologic signs, Onset sudden, Older age at onset, Pattern change; extended versions add Papilloedema, Positional headache, Precipitated by Valsalva, Pregnancy-related and Painful eye with autonomic features (SNOOP10).

• Thunderclap onset: maximal within seconds to one minute — emergency, consider subarachnoid haemorrhage
• Fever with neck stiffness, confusion or rash — emergency, consider meningitis/encephalitis
• New neurological deficit: weakness, speech disturbance, vision loss, double vision — emergency
• Headache after head trauma, or new headache in pregnancy/postpartum with hypertension
• New-onset headache after age 50, cancer history, immunosuppression, or anticoagulant use
• Worse with lying flat, coughing, straining, or waking from sleep with nausea — consider raised intracranial pressure
• Progressive pattern change over weeks, or headache that is always same-sided and never switches
• Painful red eye with visual halos — consider acute glaucoma (ophthalmic emergency)

How screening works at the clinic

Every consultation includes structured red-flag questioning plus fundoscopy-capable examination where indicated. When red flags are absent and the pattern fits a primary headache disorder, imaging is usually unnecessary — this protects patients from incidental findings and unnecessary cost. When flags are present, referral pathways to urgent neuroimaging or emergency care are arranged the same day rather than delayed.

• Structured SNOOP-based history for every headache patient
• Neurological examination including fundi, gait and focal screening
• Clear written guidance on which symptoms mean go to hospital immediately
• Same-day escalation pathway when urgent imaging is indicated

Guidelines referenced:

• NICE guideline CG150 — Headaches in over 12s: diagnosis and management
• ICHD-3 secondary headache diagnostic criteria
• AHS/AAN Choosing Wisely guidance on avoiding routine neuroimaging for stable primary headache