Suprasellar Cistern Involvement with Peripheral Extension
- Characteristic of saccular aneurysm rupture but can also occur from other etiologies such as a non-saccular aneurysm or a vascular malformation
Perimesencephalic & Low Basal Cisterns
- Idiopathic but can rarely be due to vertebrobasilar aneurysm rupture in approximately 5% of cases. Other rare causes of the perimesencephalic pattern include a cervicomedullary junction tumor, vascular malformation, or acute arterial dissection
Cerebral Convexity
- Heterogeneous group of etiologies including reversible cerebral vasoconstriction syndrome, cerebral amyloid angiopathy (CAA), posterior reversible encephalopathy syndrome (PRES), cerebral venous thrombosis (CVT), and other less common causes.