sah

Subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space, the area between the arachnoid membrane and the pia mater surrounding the brain. SAH can be traumatic or spontaneous; the spontaneous form is most often caused by rupture of an intracranial aneurysm or, less commonly, by arteriovenous malformations, moyamoya disease, or other vascular anomalies. Aneurysmal rupture is the leading cause of nontraumatic SAH and carries a high risk of rebleeding if not promptly treated.

The hallmark is a sudden, severe headache, often described as thunderclap. Other symptoms include neck stiffness, photophobia, nausea, vomiting, loss of consciousness, or neurological deficits.

Non-contrast CT is the initial test; most helpful within 6-24 hours of onset. If CT is negative but SAH remains suspected, a lumbar puncture or spectrophotometric analysis for xanthochromia can confirm. CT angiography or MRI can identify aneurysm or AVM. Digital subtraction angiography is the gold standard for vascular anatomy.

Immediate priorities include securing the airway, monitoring and controlling blood pressure, and preventing rebleeding. Definitive treatment aims to secure the source of bleeding: microsurgical clipping or endovascular coiling of the aneurysm. Hydrocephalus may require external ventricular drain. Nimodipine is commonly used to reduce delayed cerebral ischemia from vasospasm; management of vasospasm and hyponatremia is important.

SAH has high mortality and morbidity; overall mortality remains significant in the first weeks, with many survivors experiencing cognitive or functional impairment. Risk factors include hypertension, smoking, excessive alcohol use, cocaine or amphetamine use, and family history. Prevention focuses on management of aneurysms in high-risk individuals and risk factor modification.