A Review of 65 Cases of Unruptured Aneurysms under Observation: The Risks of Untreated Aneurysm under 5 mm in Size.

A retrospective review of 65 cases with 75 aneurysms under conservative observation at our hospital during the past 7 years was performed to investigate the natural history of unruptured cerebral aneurysms. The median follow-up time was 2.8 years (47-2,476 days). There were 30 males and 35 females, and the mean age was 61.8. The criteria for decision of conservative treatment were as follows: 1) size of the aneurysms (less than 5 mm): 55 cases (73.3%) ; 2) age (more than 70) : 3 cases (4.0%) ; 3) high surgical risk: 6 cases (8.0%) ; 4) dissent: 2 cases (2.7%) ; 5) location of aneurysms: 8 cases (10.7%) ; 6) poor physical condition: 1 case (1.3%). There were 48 ICA aneurysms (64.0%), 62 aneurysms (82.7%) were less than 5 mm, 8 aneurysms (10.7%) had bleb, 72 aneurysms (96.0%) were asymptomatic, and 37 aneurysms (49.3%) were multiple aneurysms. Three cases were ruptured during the observation period. Two of the 3 ruptured aneurysms were small (less than 5 mm), asymptomatic, and were both multiple aneurysms with bleb. Contrary to previous reports, this study suggests that small multiple aneurysms with bleb may have higher risks of rupture under observation.