Synopsis
Triage headache by onset, context and neurological findings, identify time-critical secondary causes, and choose imaging or lumbar puncture for a defined diagnostic question.
- First ask how quickly pain reached maximum intensity: instantaneous or within minutes is a thunderclap phenotype and must be investigated for subarachnoid haemorrhage and vascular alternatives.
- A new progressive headache with fever, immunosuppression, malignancy, pregnancy, recent trauma, cognitive change, focal signs or papilloedema has a lower threshold for urgent investigation.
- Measure blood pressure and temperature, perform fundoscopy where competent, assess visual acuity and fields, and document a full neurological examination including cognition and gait.
- For suspected subarachnoid haemorrhage arrange immediate non-contrast CT head; the role and timing of lumbar puncture depend on scan timing, interpretation and the NICE pathway.
- Do not perform lumbar puncture before resolving contraindications such as signs of raised intracranial pressure, focal mass effect, cardiorespiratory instability or a bleeding risk.
- Jaw or tongue claudication, scalp tenderness, visual symptoms and polymyalgic features in an older adult suggest giant cell arteritis; inflammatory markers cannot safely overrule a strong phenotype.
- Normal neuroimaging does not make every secondary cause disappear: cerebral venous sinus thrombosis, dissection, meningitis, pituitary apoplexy and pressure disorders need targeted tests.
- A familiar primary headache can coexist with a new secondary disorder; compare the current episode with the person's established pattern instead of relying only on a previous migraine label.
- Avoid routine imaging solely for reassurance when migraine or tension-type headache is clinically secure and no secondary features are present, because incidental findings can create harm.
Key red flags
Pain reaching maximal severity instantly or within a few minutes, particularly during exertion or sexual activity, needs urgent vascular assessment even when examination later normalises.
Papilloedema, transient visual obscurations, pulsatile tinnitus, diplopia, progressive morning headache or vomiting suggests pressure pathology; a sixth-nerve palsy can be a false localising sign.
Fever, meningism, rash, photophobia, seizure, behavioural change or reduced consciousness should trigger immediate sepsis and meningitis or encephalitis pathways, recognising that the complete cluster may be absent.
New headache with scalp tenderness, jaw or tongue claudication, visual disturbance, constitutional features or polymyalgia in an older person threatens irreversible sight and requires immediate action.
New unilateral head or neck pain with partial Horner syndrome, pulsatile tinnitus, cranial-nerve symptoms or delayed cerebral ischaemia warrants urgent arterial imaging and stroke expertise.
Severe new or changing headache during pregnancy or after birth, especially with hypertension, proteinuria, seizure, focal signs or thrombosis risk, must not be dismissed as ordinary migraine.
Investigation priorities
Detect acute subarachnoid or other intracranial haemorrhage and major mass effect in an emergency presentation.
Management branches
A person presents with a new, severe or substantially changed headache.
- Stabilise ABCDE, check glucose, temperature and blood pressure, establish exact onset-to-peak time and identify seizure, focal deficit, meningism, visual threat or impaired consciousness.
- Activate the relevant emergency pathway for thunderclap headache, sepsis, pregnancy-related hypertension, acute eye disease, carbon monoxide exposure or intracranial pressure signs.
- Obtain focused exposure, medicine and risk history while arranging the correct immediate imaging or specialist examination, avoiding routine primary-headache treatment as a diagnostic trial.
- Reassess symptoms and neurology after initial analgesia because improvement does not exclude haemorrhage, dissection, infection or raised pressure.