Cerebral aneurysm classification based on angioarchitecture.

Cerebral aneurysms are commonly named based on their relationship with adjacent vessels in either the anterior or posterior circulation. Although such an approach has long proved useful, this terminology does not take into account potential hemodynamic forces or aneurysm wall properties that are likely to be important for cerebral aneurysm formation, growth, rupture, and treatment. Dissecting, traumatic, false, infectious, and tumorous aneurysms were excluded from review. Only aneurysms in which preoperative imaging studies and operative findings were sufficient for classification were included. All 329 reviewed aneurysms could be divided into 2 groups: fusiform (n=16) and saccular (n=313). Fusiform aneurysms could be subdivided into 2 types: simple (no branch vessel; n=10) and complex (one or more side branches; n=6). Saccular aneurysms could be subdivided into 3 groups: those not associated with a branch vessel (n=31), those associated with a side-branch vessel (n=125), and those located at a bifurcation (n=157). Each of these categories of aneurysms could be classified further based on its association with a conducting, primary, secondary, tertiary, or side-branch vessel. Classification of cerebral aneurysms according to this scheme adequately described all reviewed aneurysms. Grouping aneurysms according to this approach focuses on similarities in angioarchitecture and potential rheologic properties that should prove useful for evaluation of aneurysm growth, rupture, and treatment.