Head CT. Subarachnoid hemorrhage fills the basilar cisterns (the "star sign") but the ventricular system does NOT contain hemorrhage.
Subarachnoid Hemorrhage
Subarachnoid hemorrhage is bleeding into the subarachnoid space. Trauma is the most common cause. Cerebral artery aneurysm is the most common non-traumatic cause.
Aneurysmal rupture typically presents with thunderclap headache and focal neurological deficit, and has an all-cause mortality of roughly 50% at 6 months.
Modifiable Risk Factors for Cerebral Aneurysm:
- Hypertension
- Tobacco Abuse
- Hyperlipidemia
- Increased Intracranial Pressure -> Brain Herniation -> Death
- Cerebral Vasospasm
- Obstructive Hydrocephalus