Abstract
The incidence of de novo intracranial aneurysm development and enlargement of untreated additional aneurysms is still unknown and requires further research. Over a 15.4-year period, the authors performed clinical surveillance in 748 consecutive patients with clip-ligated unruptured intracranial aneurysms. Serial magnetic resonance angiography was performed in 702 patients for 5.3±3.3 years. During 3716.3 patient-years of follow-up, the incidence of de novo aneurysm formation was 0.27%/patient-year. The cumulative incidence of de novo aneurysm development was 0.5%, 3.3%, and 6.4% at 5, 10, and 15 years, respectively. A total of 114 additional aneurysms were seen in 107 patients Over 621.8 patient-years of follow-up, the annual risk of aneurysm growth was 2.7%. The cumulative incidence of additional aneurysm growth was 12.5%, 28.6%, and 59.5% at 5, 10, and 15 years, respectively. None of the factors including sex, age, history of hypertension, history of smoking, family history of subarachnoid hemorrhage, multiplicity, and size of untreated aneurysm were statistically significant predictors of de novo aneurysmal formation or growth of additional aneurysms. The annual incidence of interventional processes (surgical clipping or coil embolization) was 0.73%/patient-year. Patients with clip-ligated unruptured intracranial aneurysms should be continuously monitored for a long period, and appropriate interventions should be considered according to neuroradiological findings to prevent the development of subarachnoid hemorrhages.
