NeurologyPending review

Subarachnoid haemorrhage

Sudden rupture of a blood vessel, most often a berry aneurysm, into the subarachnoid space causes an instantaneous, maximal-at-onset thunderclap headache as blood irritates the meninges and abruptly raises intracranial pressure, making the pattern of onset itself the diagnostic clue.

In a nutshell

SAH is sudden rupture of a vessel, usually a berry aneurysm, into the subarachnoid space, causing an instantaneous thunderclap headache, meningism from blood irritating the meninges, and a risk of both rebleeding and delayed vasospasm-driven ischaemia.

Classic presentation

Sudden, severe worst headache of my life that is maximal within seconds, with neck stiffness, vomiting and transient loss of consciousness.

Key points

The onset pattern is the key clue: maximal at onset (thunderclap) distinguishes SAH from headaches that build up gradually.

You’ve reached the end of the preview

This topic is part of full high-yield access. Create a free account to read every key point, first-line investigation and exam trap — or browse the free sample topics without one.

Educational content pending clinical review. Not medical advice.