Headache Differentials
Key Facts
Red flags for secondary headache (SNOOP₄): Systemic symptoms/illness, Neurological signs, Onset sudden (thunderclap), Older age (>50 new headache), Previous headache different, Positional, Precipitated by Valsalva, Progressive.
Source: AAN; Headache Australia.
Warning
Thunderclap headache (maximal intensity within seconds) is SAH until proven otherwise. CT brain within 6 hours has ~99% sensitivity — if negative and >6 hours, perform LP for xanthochromia.
Life-Threatening Causes
| Diagnosis | Key Features | Investigation |
|---|---|---|
| SAH | Thunderclap, "worst ever", meningism | CT brain → LP if negative |
| Meningitis | Fever, neck stiffness, photophobia | LP, blood cultures |
| Temporal arteritis | Age >50, jaw claudication, visual loss | ESR/CRP, temporal artery biopsy |
| Cerebral venous sinus thrombosis | Headache + focal signs, pregnancy/OCP | CT venogram or MR venogram |
| Space-occupying lesion | Progressive, worse morning, focal signs | CT/MRI brain |
| Hypertensive emergency | SBP >180, end-organ damage | BP, fundoscopy, renal function |
| Acute angle-closure glaucoma | Eye pain, red eye, halos, fixed mid-dilated pupil | IOP measurement |
Primary Headache Patterns
| Type | Duration | Features |
|---|---|---|
| Migraine | 4–72 hr | Unilateral, pulsating, nausea, photo/phonophobia, aura |
| Tension-type | 30 min–7 days | Bilateral, pressing, mild-moderate, no nausea |
| Cluster | 15–180 min | Unilateral orbital, autonomic features (lacrimation, rhinorrhoea) |
Approach
- ABCs and assess for red flags
- Focused history: onset, character, duration, associated features, medications
- Neurological exam: pupils, fundoscopy, focal deficits, meningism
- CT brain if any red flag present
- LP if meningitis or SAH suspected with negative CT