A total of 49 studies (n=14,651) were included. The sample size ranged from 10 to 3,498.
Nineteen studies evaluated coiling (n=1,967 in the tables; n=1,925 in the text): 7 seven prospective studies (n=852) and 12 retrospective studies (n=1,115). Ten were retrospective single-centre studies, five were prospective single-centre studies and four were multicentre or community-based.
Thirty studies evaluated clipping (n=12,684 in the tables; n=11,363 in the text): 4 prospective studies (n=2,963), 23 retrospective studies (n=7,640) and 3 community-based studies (n=2,081). Twenty-one studies were retrospective single-centre studies, one was a prospective single-centre study and eight were multicentre or community-based.
The AORs ranged from 0 to 30% and mortality varied from 0 to 12%. Procedural mortality ranged from 0 to 9.7%; most studies reported procedural mortality as 0%.
The cumulative AOR was 8.8% (95% confidence interval, CI: 7.6, 10.1). For single-centre retrospective studies the AOR was 8.1% (95% CI: 6.2, 10.4).
The plot of AOR versus median study year showed that AORs have declined since the introduction of coiling in the early 1990s.
The AORs ranged from 0 to 25.1%. The cumulative AOR was 17.8% (95% CI: 17.2, 18.6).
The plot of AOR versus median study year showed that AORs increased in the 1990s. For prospective multicentre and community-based studies the cumulative AOR was 19.7% (95% CI: 18.9, 20.5). For retrospective studies the AOR was 7.9% (95% CI: 6.7, 9.3).