Subarachnoid Haemorrhage

Definition and causes. Bleeding into the subarachnoid space. About 85% follow rupture of a saccular (berry) aneurysm — anterior communicating > posterior communicating > middle cerebral bifurcation; 10% are perimesencephalic non-aneurysmal (benign course); the remainder are due to AVM, trauma, vasculitis, coagulopathy or reversible cerebral vasoconstriction syndrome. Risk factors: hypertension, smoking, alcohol, family history, adult polycystic kidney disease and connective tissue disorders.

Clinical features. Sudden “worst headache of my life” (thunderclap headache) peaking within seconds, with vomiting, neck stiffness, photophobia, transient loss of consciousness and seizures. A sentinel or warning bleed precedes the major event in up to 40%. Fundoscopy may show subhyaloid or vitreous (Terson) haemorrhage. In the elderly the presentation is often atypical — confusion, collapse or coma with less prominent headache and meningism.

Grading. Hunt and Hess (I — mild headache/nuchal rigidity, through V — deep coma and decerebrate posturing) and the WFNS scale (based on GCS plus motor deficit) grade clinical severity; the modified Fisher scale grades the volume and distribution of blood on CT and predicts vasospasm.

Diagnosis. Immediate non-contrast CT head — sensitivity exceeds 95% within the first 6 hours and falls steadily thereafter. If the CT is negative and suspicion persists, perform a lumbar puncture after 12 hours, looking for xanthochromia (ideally by spectrophotometry) and a red cell count that does not clear between successive bottles. Then CT angiography or digital subtraction angiography to define the aneurysm.

Treatment. Admit to a neurocritical care unit. Secure the aneurysm within 24 hours by endovascular coiling (preferred — ISAT showed better outcomes) or surgical clipping. Bed rest, analgesia, stool softeners; control blood pressure before the aneurysm is secured (systolic <160 mmHg) while avoiding hypotension; nimodipine 60 mg orally every 4 hours for 21 days to prevent delayed cerebral ischaemia; maintain euvolaemia and normonatraemia. Antiepileptics only if seizures occur.

Complications. Rebleeding (peaks in the first 24 hours; the highest-mortality complication); delayed cerebral ischaemia from vasospasm (days 4–14); hydrocephalus — acute obstructive needing an external ventricular drain, and chronic communicating needing a VP shunt; hyponatraemia from cerebral salt wasting or SIADH; neurogenic pulmonary oedema; stunned myocardium / Takotsubo cardiomyopathy with ECG changes and raised troponin; seizures; and long-term cognitive and mood impairment. Overall mortality is 30–40%.

AHA/ASA 2023 Guideline for Aneurysmal Subarachnoid Haemorrhage (replacing the 2012 guideline). Key positions: treat the ruptured aneurysm preferably within 24 hours, aiming for complete obliteration; early enteral nimodipine is beneficial; prophylactic hypervolaemia and haemodynamic augmentation are harmful and should NOT be used (Class 3: Harm) — maintain euvolaemia instead, and induce hypertension only once symptomatic delayed cerebral ischaemia develops; routine statin therapy and intravenous magnesium are not recommended; and outcomes are better when patients are managed in high-volume centres with dedicated neurocritical care units, so timely transfer is recommended.