Neurology · Topic 15 of 22
Headache Red Flags & Giant Cell Arteritis
Neurology · dangerous headache
Headache Red Flags & Giant Cell Arteritis
Screen every headache for red flags: thunderclap means a bleed work-up, fever means antibiotics now, and a new headache after 50 means think giant cell arteritis.
Key numbers
Thunderclap headache: CT for subarachnoid hemorrhageCT within 6 h of onset
Suspected GCA: start steroids before biopsyAge > 50
01 · Defined byThunderclap headache: CT for subarachnoid hemorrhage
A headache peaking within seconds is subarachnoid hemorrhage until proven otherwise: a negative noncontrast CT within 6 hours of onset, with a normal exam and no meningismus, rules it out; otherwise do an LP.
02 · DoSuspected GCA: start steroids before biopsy
Suspect giant cell arteritis in anyone over 50 with new headache, jaw claudication, scalp or temporal artery tenderness or visual symptoms — check ESR, CRP and CBC and start high-dose glucocorticoids immediately.
03 · DoFever, stiff neck: antibiotics before imaging
Headache with fever, meningismus or altered mental status: draw blood cultures and give empiric antibiotics plus dexamethasone at once — do not delay them for CT or lumbar puncture.
01
Causes & risk factors
Why it happensGCA overlaps polymyalgia rheumatica and aortitisPolymyalgia rheumatica symptoms occur in 40–60% of GCA; mean onset is about 70; aortitis can cause thoracic aneurysm or dissection, so image the aorta at diagnosis and periodically.
Also dangerous: venous sinus thrombosis, dissection, hemorrhageOther sudden or dangerous headaches: cerebral venous sinus thrombosis (MRI with MR venography), carotid or vertebral dissection (headache with neck pain), and intracerebral hemorrhage (vomiting, focal deficits, altered mental status).
Household headaches near heaters: check carboxyhemoglobinHeadache with exposure to fires, heaters, furnaces or poorly vented engines suggests carbon monoxide poisoning — measure a carboxyhemoglobin level.
02
Presentation
What you'll seeRed eye with halos: acute angle-closure glaucomaUnilateral frontal or orbital headache with halos, blurred vision, red eye and vomiting suggests acute angle-closure glaucoma — measure intraocular pressure.
Worse lying down or on waking: mass lesionHeadache worse with recumbency, on awakening or waking the patient from sleep, with vomiting, papilledema or loss of retinal venous pulsations, suggests a mass or raised intracranial pressure.
03
Do right now
In this orderFirst moves
1
→Screen every headache for red flags
2
→Fever, stiff neck: antibiotics before imaging
3
→Thunderclap headache: CT for subarachnoid hemorrhageCT within 6 h of onset
4
Suspected GCA: start steroids before biopsyAge > 50
Why each step
Screen every headache for red flagsRed flags: thunderclap onset, new headache after 50, neurologic signs or papilledema, meningismus, fever or weight loss, severe hypertension, immunosuppression or cancer, progressive worsening, red eye with halos.
Fever, stiff neck: antibiotics before imagingHeadache with fever, meningismus or altered mental status: draw blood cultures and give empiric antibiotics plus dexamethasone at once — do not delay them for CT or lumbar puncture.
Thunderclap headache: CT for subarachnoid hemorrhageA headache peaking within seconds is subarachnoid hemorrhage until proven otherwise: a negative noncontrast CT within 6 hours of onset, with a normal exam and no meningismus, rules it out; otherwise do an LP.
Suspected GCA: start steroids before biopsySuspect giant cell arteritis in anyone over 50 with new headache, jaw claudication, scalp or temporal artery tenderness or visual symptoms — check ESR, CRP and CBC and start high-dose glucocorticoids immediately.
04
Management
OrdersGCA: prednisone 40–60 mg; IV pulse for vision must knowTreat GCA with prednisone 40–60 mg daily (about 4 weeks, then slow taper); with visual symptoms give IV methylprednisolone 500–1000 mg daily for 3–5 days to protect the other eye.
Image urgently for thunderclap, papilledema or deficitsImage promptly (MRI, or CT if MRI is unavailable) for thunderclap headache, altered mental status, meningismus, papilledema or acute focal deficit; image less urgently for new onset after 50, cancer, HIV or pattern change.
Temporal artery biopsy stays positive for 2 weeksConfirm GCA with temporal artery biopsy (longer segments raise yield) — still diagnostic up to 2 weeks after steroids start; expert color Doppler ultrasound (halo sign) is an alternative if done within 5 days.
Add tocilizumab to spare steroids in GCAConsider tocilizumab with initial steroids for faster tapering and more sustained remission; most patients need at least 2 years of steroids — add bone protection, and low-dose aspirin for critical carotid or vertebral involvement.
05
Red flags & don'ts
Avoid harmGCA vision loss is sudden and irreversible complicationGCA vision loss comes from ischemic optic neuropathy, may follow brief amaurosis fugax and is irreversible once infarction occurs; jaw claudication and diplopia mark higher risk of blindness.
06
The rules
Know theseCT before LP with papilledema or focal signsImage before lumbar puncture when there is papilledema, a focal deficit, focal seizures, a known mass, a large stroke or suspected abscess — LP with mass effect can cause herniation.
07
Subarachnoid hemorrhage or migraine?
Commonly confused| Onset | Thunderclap — peaks within seconds |
|---|---|
| Pattern | New headache, unlike any before |
| Associated | Vomiting, syncope, meningismus, obtundation |
| Work-up | Noncontrast CT, then LP if needed |
08
More detail
ReferenceShow 6 reference facts
Idiopathic intracranial hypertension: migraine-like headache with papilledema, diplopia and pulsatile tinnitus — obtain MRI with MR venography, then LP for opening pressure.
Recurrent headaches with similar features since childhood or young adulthood in a well patient with a normal exam are rarely ominous; a clear change in pattern warrants evaluation for a secondary cause.
Migraine is unilateral or bilateral pulsating pain lasting 4–72 hours, often with nausea, photophobia and sonophobia, sometimes aura, worse with activity — diagnosed by history and exam alone.
Chronic subdural hematoma presents with sleepiness, confusion or hemiparesis in older patients, those on anticoagulants, with alcohol use, falls or head trauma — image.
Subarachnoid hemorrhage headache peaks within seconds and may bring vomiting, syncope at onset, obtundation and meningismus.
Treat nonmigrainous primary headaches with short courses of nonopioid analgesics; avoid opioids.
A headache that peaks in seconds is a bleed until imaging says otherwise; a new headache after 50 is secondary until proven otherwise — think giant cell arteritis.
Sources · Merck Manual Professional — Approach to the Patient With Headache · Merck Manual Professional — Giant Cell Arteritis (updated Aug 2026; cites 2021 ACR/VF GCA guideline) · Merck Manual Professional — Subarachnoid Hemorrhage (SAH) · Merck Manual Professional — Acute Bacterial Meningitis · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).