FFinalistSouthampton · 2027
Neurology
AKT · Neurology/Stroke & vascular

Subarachnoid haemorrhage

Bleeding into the subarachnoid space (ruptured berry aneurysm ~85%)

Overview

Spontaneous bleeding into the subarachnoid space, usually from a ruptured berry aneurysm. The classic "thunderclap" headache — sudden, maximal at onset, worst ever — demands urgent CT and, if negative, an LP for xanthochromia.

Recognise

  • Sudden "thunderclap" headache — maximal within 1 minute, "worst headache of my life"
  • Meningism (neck stiffness, photophobia), nausea/vomiting, reduced consciousness, seizures
  • Associations: ADPKD, Ehlers-Danlos/connective tissue disease, coarctation, smoking, hypertension

Red flags

  • Reduced GCS, focal deficit, rebleeding (highest risk first 12h), hydrocephalus, vasospasm (delayed ischaemia)

Differentials & how to tell them apart

Migrainebuilds over time, prior episodes — not instantly maximal
Bacterial meningitisfever + gradual onset; SAH headache is instantaneous
Venous sinus thrombosis (CVST)subacute headache, risk factors, CT venogram
Reversible cerebral vasoconstrictionrecurrent thunderclap, beaded vessels

Investigations

Urgent non-contrast CT (blood in basal cisterns). If CT negative but suspicion remains → LP ≥12h after onset for XANTHOCHROMIA (bilirubin). CT angiogram to localise the aneurysm.

Management

Urgent CT (then LP if negative) → neurosurgery; nimodipine to prevent vasospasm

  1. 1Urgent non-contrast CT; if negative and onset ≥12h ago, LP for xanthochromia. Confirmed SAH → refer to neurosurgery, CT angiogram.Gate: CT within 6h is highly sensitive; beyond that a negative CT does NOT exclude SAH → do the LP (≥12h after onset, for xanthochromia)
  2. 2Nimodipine to reduce vasospasm; definitive aneurysm treatment by endovascular coiling (preferred) or surgical clipping; monitor for rebleed/hydrocephalus/hyponatraemia (SIADH).
Nimodipine — oral calcium-channel blocker to prevent vasospasm/delayed ischaemia
Analgesia, antiemetics — supportive

Key points

Xanthochromia (LP ≥12h) distinguishes true SAH from a traumatic tap. Nimodipine is for vasospasm prevention, not the headache. Coiling generally beats clipping.

Monitor & prognosis

GCS, neuro obs, for rebleed/vasospasm/hydrocephalus/Na+; angiographic follow-up.

High early mortality; rebleeding and delayed ischaemia are the killers.

Source: NICE; neurosurgical guidance