Headache Red Flags: When to Seek Urgent Medical Evaluation

Most headaches are primary (migraine, tension-type, cluster). Secondary headaches require prompt identification. Use the SNOOP4 mnemonic for red flags:

SNOOP4 Red Flags

Letter	Feature	Examples
S	Systemic symptoms	Fever, weight loss, malignancy, immunosuppression
N	Neurologic deficits	Weakness, numbness, vision loss, ataxia, confusion
O	Onset sudden/thunderclap	Peak intensity <1 min (SAH, RCVS, dissection)
O	Older age (>50) new onset	Giant cell arteritis, mass lesion, trigeminal neuralgia
P	Pattern change	Frequency, severity, character change; progressive
P	Positional	Worse supine (IIH), better supine (CSF leak)
P	Precipitated by Valsalva	Cough, strain, exertion (Chiari, mass)
P	Papilledema	IIH, mass, venous thrombosis

Additional Urgent Features

• Headache awakening from sleep (mass, sleep apnea, cluster)
• Post-traumatic headache (subdural, CSF leak)
• New headache in pregnancy/postpartum (preeclampsia, CVT, pituitary apoplexy)
• Immunocompromised host (opportunistic infection, lymphoma)
• Anticoagulation (subdural hemorrhage)

Action Thresholds

• Emergency (call 911/ED): Thunderclap, focal deficit, altered consciousness, papilledema, post-traumatic with LOC.
• Urgent (same-day): New onset >50, progressive pattern, systemic signs, immunosuppressed.
• Prompt (within days): Pattern change, positional, Valsalva-triggered.

Diagnostic Approach

• Non-contrast CT head: First-line for thunderclap, trauma, focal signs.
• MRI brain: Mass, IIH, posterior fossa, cervicomedullary junction.
• Lumbar puncture: SAH (if CT negative), meningitis, IIH, carcinomatous meningitis.
• CTA/MRA: Vascular dissection, aneurysm, CVT.

When in doubt, image. Missed secondary headache carries higher risk than over-investigation.