Headache Red Flags
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Direct answer
Red flags separate the dangerous secondary headaches from primary ones, and the SNOOP mnemonic organises them: Systemic symptoms or illness (fever, weight loss, malignancy, HIV), Neurological deficit or confusion, Onset sudden ("thunderclap"), Older age at new onset (over about 50), and Pattern change, Positional features, Precipitants like Valsalva, Papilloedema or Pregnancy. Any positive flag triggers targeted investigation — neuroimaging first for most, erythrocyte sedimentation rate and immediate steroids for suspected giant cell arteritis, with a low threshold for cerebral venous sinus thrombosis in puerperal Indian women.
What you must remember
- Thunderclap headache reaching maximum intensity within seconds to a minute demands urgent non-contrast CT; CT is highly sensitive for subarachnoid haemorrhage within the first 6 hours, and a negative late-presenting CT requires lumbar puncture for xanthochromia.
- Beyond aneurysmal bleed, the thunderclap differentials include cerebral venous sinus thrombosis (young women, puerperium, oral contraceptive use — common in Indian practice), cervical artery dissection (neck pain or trauma precedes), reversible cerebral vasoconstriction syndrome and pituitary apoplexy.
- New headache over age 50 with scalp tenderness, jaw claudication or visual symptoms is giant cell arteritis until disproven: raised ESR and CRP, start corticosteroids immediately (do not await biopsy), and arrange temporal artery biopsy within days.
- Raised intracranial pressure pattern: morning headache, worse with coughing, straining or bending, vomiting without nausea predominance, transient visual obscurations, and papilloedema on fundoscopy — image before any lumbar puncture.
- Positional headache — worse upright, relieved lying — suggests intracranial hypotension (post-dural puncture, spontaneous CSF leak); worse lying and on waking suggests raised pressure or a posterior fossa mass.
- New headache with fever, neck stiffness or rash means meningitis pathway (blood cultures, urgent LP where safe); headache with confusion and seizures is encephalitis until proven otherwise.
- Headache in pregnancy or the puerperium with seizures, visual loss or focal signs raises pre-eclampsia, CVT and reversible posterior leukoencephalopathy — all emergencies.
- Progressive "never the same again" headache in a cancer or HIV patient, or any headache with papilloedema, warrants urgent contrast-enhanced imaging.
Triaging three headaches in one emergency shift
Three patients, one hour. The first is a 46-year-old with the "worst headache of my life", maximal within a minute while straining at stool, now two hours in with neck stiffness but no deficit. This is the subarachnoid pathway: immediate non-contrast CT — within 6 hours its sensitivity approaches the high nineties per cent; if CT is negative beyond that window or suspicion persists, lumbar puncture after imaging looks for xanthochromia — the warning leak misread as migraine is the classic error. The second is a 70-year-old with three weeks of new right temporal headache, scalp tenderness on combing, jaw ache while eating, and yesterday a transient grey-out of vision. No imaging detour here: ESR and CRP now, prednisolone started immediately on suspicion (high-dose, guided by whether vision is involved), temporal artery biopsy arranged within about two weeks — steroids do not invalidate the biopsy that soon, and visual loss is the preventable catastrophe. The third is a 28-year-old delivered ten days ago, on no contraception, with a holocranial gradual headache, two focal seizures and left arm weakness. In India this is the cerebral venous sinus thrombosis triad — puerperium, seizures, deficit — and the investigation is CT/MR venography, not a plain CT alone; anticoagulation follows even with an infarct present, because the thrombosing sinus, not the venous infarct, is the target. Three patterns, three different first investigations, one principle: the red flag, not the pain severity, dictates the pace.
Where students slip
Examiners plant the same snares. Ordering an ESR "before starting steroids" in suspected giant cell arteritis and deferring treatment is the lethal rewrite — steroids come first, immediately. Treating a negative CT beyond 6 hours as exclusion of subarachnoid haemorrhage is the second — the lumbar puncture for xanthochromia completes the work-up. Attributing a puerperal headache with seizures to "migraine" or simply eclampsia while missing venous sinus thrombosis is the third, and the Indian exam loves it. And the fundoscope nobody uses: papilloedema found before a lumbar puncture is performed converts a routine work-up into a safe one.
Frequently asked questions
What does SNOOP stand for in headache screening?
Systemic symptoms/illness, Neurological deficits, Onset sudden (thunderclap), Older age at new onset (over about 50), and Pattern change or Positional/Papilloedema/Pregnancy features.
How is suspected subarachnoid haemorrhage investigated?
Urgent non-contrast CT (near-definitive within about 6 hours), followed by lumbar puncture for xanthochromia when CT is negative and the history is convincing; CT angiography locates the aneurysm.
Why is giant cell arteritis treated before biopsy?
Immediate high-dose corticosteroids prevent irreversible blindness, and the biopsy remains informative for about two weeks despite steroid initiation — treatment never waits for histology.
Why suspect cerebral venous sinus thrombosis in Indian practice?
Young puerperal women are disproportionately affected, presenting with progressive headache, seizures and focal deficits; MR or CT venography is the diagnostic study.
Which headache features suggest raised intracranial pressure?
Morning or Valsalva-worsening headache, vomiting without preceding nausea, transient visual obscurations and papilloedema — image before lumbar puncture.