What type of aneurysm accounts for 75% of cases of subarachnoid hemorrhage?

The type of aneurysm that accounts for 75% of cases of subarachnoid hemorrhage is the berry (saccular) aneurysm. These aneurysms are characterized by a sac-like bulge on one side of an artery, commonly found at the bifurcations of the major cerebral arteries at the base of the brain.

Berry aneurysms are especially significant in the context of subarachnoid hemorrhage because they tend to rupture, leading to bleeding in the subarachnoid space. This condition can cause severe headaches, neurological deficits, and requires urgent medical attention. The prevalence of berry aneurysms as a cause of subarachnoid hemorrhage highlights their clinical importance, as identifying and managing these aneurysms can greatly reduce morbidity and mortality.

While other types of aneurysms, like dissecting and fusiform aneurysms, can cause hemorrhagic events, they are less frequently associated with subarachnoid hemorrhage compared to berry aneurysms. Mycotic aneurysms, which occur due to infection, are also relatively rare and not the primary concern when considering the majority of subarachnoid hemorrhage cases. Thus, the prominence of berry aneurysms in this context