Background and Purpose—The aim of this study was to analyze the clinical results of Guglielmi detachable bare coil (GDC) embolization of intradural saccular aneurysms (AAs) at a single center and to relate the morphological results at various time points to the clinical situation.

Methods—All intradural saccular AAs treated with GDCs between 1993 and April 2005 were prospectively entered into a database completed by retrospective analysis of charts and images and a long-term clinical outcome questionnaire. In 413 consecutive patients, there were 466 treated AAs, of which 68.7% were ruptured and 31.1% were unruptured.

Results—The periprocedural thromboembolic event rate, retreatment procedures included, was 5.4%, causing permanent neurologic deficits in 2.2% of patients. One patient (0.2%) bled during a mean±SD clinical follow-up of 64.3±39.9 months (93 AAs were followed up for >8 years and 45 AAs were followed up for >10 years) for a total of 1810 patient-years. The modified Rankin Scale score was 0 in 54.7%, 1 in 21.0%, 2 in 12.1%, 3 in 7.1%, 4 in 2.1%, 5 in 0.3%, and 6 (death from unrelated causes) in 2.7% of patients. If an aneurysm, with or without a remnant, was unchanged for 12 months, then the risk for future morphological loss was 4.8%, whereas if an aneurysm showed a morphological loss during the earlier 12-month interval, the risk for additional late loss was 38.3% (P<0.001, odds ratio=12.4).

Conclusions—Embolization of saccular AAs entails a prolonged management period. A stable angiographic result during a 12-month interval predicts a low risk for morphological deterioration. This regimen, aiming for a stable angiographic result rather than complete aneurysm occlusion, gives a low rebleed rate and excellent clinical long-term results.