Mid- to Long-term Durability of Clip-ligated Asymptomatic Unruptured Cerebral Aneurysms

The long-term neuroradiological prognosis of clip-ligated asymptomatic unruptured cerebral aneurysms is still unknown. Neuroradiological studies with contrast material (computed tomography [CT] angiography and/or digital subtraction angiography) were performed in 272 consecutive patients (283 procedures) with clip-ligated 316 aneurysms at 5 years or later after the procedure to evaluate local recurrence of the target aneurysms. There were 48 aneurysms at the anterior communicating artery (ACoA), 9 at other anterior cerebral arteries, 45 at the posterior communicating artery (PCoA), 64 at other internal carotid arteries, 139 at the middle cerebral artery, and 11 in the posterior circulation. Neck/aneurysm remnant was identified in 19 (6.0%) cases. The most recent imaging was performed at an average of 85.2 months (median, 75 months) after the procedure. Two aneurysms showed local recurrence at 79-113 months after the procedure. The overall annual recurrence rate was 0.15% (Kaplan-Meier) and 0.10% (patient-year). In patients with completely clipped aneurysms, the annual recurrence rate was 0.15% (Kaplan-Meier) and 0.053% (patient-year). In patients with neck remnant, the annual recurrence rate was 1.2% (Kaplan-Meier) and 0.8% (patient-year). This study demonstrates that the incidence of local recurrence of clip-ligated asymptomatic unruptured cerebral aneurysms is very low despite the fact that priority is often given to patency of the normal vessel rather than perfect obliteration of the aneurysm. Although the incidence is very low, local recurrence may take place long after procedures, and continuous monitoring by neuroradiological imaging with contrast material is imperative.