Table 2.

Aneurysm characteristics

Characteristic	Frequency (N = 1322)
Aneurysm size (maximum aneurysm length)	12.79 ± 8.75
< 10 mm	630 (47.7%)
10–25 mm	555 (42.0%)
> 25 mm	137 (10.4%)
Average neck size	6.21 ± 3.92
Average parent artery diameter	3.88 ± 0.82
Aneurysm form
Saccular	1099 (83.1%)
Fusiform	109 (8.2%)
Dissecting	83 (6.3%)
Blister	31 (2.3%)
Location
Anterior circulation
Anterior circulation proximal	1105 (83.6%)
Anterior circulation distal	48 (3.6%)
Posterior circulation	169 (12.8%)
Basilar	29 (2.2%)
Vertebral artery and other vessels in the posterior circulation*	140 (10.6%)

Data are shown as n (%) or the mean ± SD

*Other vessels in the posterior circulation include the posterior cerebral artery and posterior inferior cerebellar artery