Outcome After Clipping of Unruptured Intracranial Aneurysms Depends on Caseload

OBJECTIVE: Although most neurovascular centers currently have a coil first policy, the percentage of coiled versus clipped aneurysms, as well as treatment outcomes, varies strongly between these centers. This study evaluates the impact of an increase in clipping caseload on treatment outcome in a large single-center series. METHODS: All consecutive patients who underwent microsurgical clipping of unruptured intracranial aneurysms between January 2003 and April 2014 in our department were analyzed retrospectively. According to the change of the chairman in the neurosurgical department (1 September 2008) with a subsequent increase in the clipping volume, the entire cohort was divided into 2 groups with equal time intervals (historic and current cohorts). RESULTS: There were 94 clipped unruptured intracranial aneurysms in the historic cohort and 252 in the current cohort. Unfavorable outcome at 6 months postoperatively (defined as modified Rankin Score >2) was observed in 8 cases (8.5%) in the historic cohort and 7 cases (2.8%) in the current cohort (P < 0.0001). The surgical mortality decreased from 3.2% to 0%. Cerebral infarction on postoperative computed tomography scan was observed in 25 cases (26.6%) in the historic cohort and 19 cases (7.5%) in the current cohort (P < 0.0001). Within the current cohort, there was a progressive improvement of surgical outcome over the time. CONCLUSIONS: The improvement of the surgical outcome after increasing the clipping caseload underlines the importance of sufficient surgical volume for maintenance of competitive treatment results.