Overview
Definition
Bleeding into the subarachnoid space (between the arachnoid membrane and the pia mater), where cerebrospinal fluid circulates.
Epidemiology
High mortality rate (up to 50%). Affects slightly younger demographics than other strokes (mean age ~50).
Etiology & Risk Factors
- Rupture of a berry (saccular) aneurysm (80% of non-traumatic cases)
- Trauma (most common overall cause)
- Arteriovenous malformation (AVM) rupture
Clinical Symptoms
- 'Worst headache of my life' (Thunderclap headache) - sudden and extremely severe
- Nausea and vomiting
- Meningeal signs (nuchal rigidity, photophobia)
- Brief loss of consciousness or altered mental status
Clinical Approach
Diagnosis
- Non-contrast Head CT (highly sensitive if done within 6 hours of onset)
- Lumbar Puncture (if CT is negative but clinical suspicion is high) showing Xanthochromia (yellowish CSF due to bilirubin from RBC breakdown)
- Cerebral Angiography / CTA (to locate the aneurysm)
Management
- Aneurysm clipping (surgical) or endovascular coiling (to secure the aneurysm and prevent re-bleeding)
- Strict BP control (< 160 systolic)
- Nimodipine (calcium channel blocker specifically used to prevent vasospasm in SAH)
Complications
- Vasospasm (leading to delayed ischemic neurologic deficit, usually days 3-14)
- Re-bleeding (highest risk in first 24h)
- Hydrocephalus
- Hyponatremia (cerebral salt wasting)