PREDICTING OUTCOME FOLLOWING SURGICAL-TREATMENT OF UNRUPTURED INTRACRANIAL ANEURYSMS - A PROPOSED GRADING SYSTEM

Surgical treatment of unruptured aneurysms is gaining increased suppor t owing to the recently defined poor longterm natural history of these aneurysms. The benefit of treatment ultimately depends on the relativ e risk of subsequent aneurysm rupture in untreated patients versus the risk of surgery. To identify those patients at a higher risk from sur gery, the authors reviewed the management of 172 patients with unruptu red intracranial aneurysms treated at their institution. The size of t he aneurysms ranged from 3 to 45 mm (mean 13.7 mm). Twenty-two patient s (12.8%) had aneurysms in the posterior circulation, and 32 (18.6%) o f these were giant aneurysms. Major morbidity occurred in 12 patients (6.9%) and five patients (2.9%) died. MuItivariate logistic analysis o f several risk factors revealed that aneurysm size and location had an independent correlation with surgical outcome and that patient age ap proached statistical significance. Patients presenting with ischemic c erebrovascular disease, in particular, did not have a higher risk of a poor outcome. A simple classification for predicting patients at high risk from surgical morbidity and mortality is proposed. Preoperative grading is based on the size and location of the aneurysm and patient' s age. The lowest,made is given to young patients with small anterior circulation aneurysms, and the highest made includes elderly patients with complex giant posterior circulation aneurysms. A retrospective an alysis of this classification demonstrated a strong correlation with p ostoperative outcome. The incidence of poor outcome progressively incr eased with a higher grade, ranging from 0% in Grade 0 to 66.6% in Grad e VI. An analysis of this classification on 50 consecutive surgically treated patients with unruptured aneurysms not included in the analysi s also validated the predictive value of this system. Along with predi cting outcome, this classification should provide a standardized forma t for comparison of results from different clinical centers as well as different therapeutic techniques (surgical vs. endovascular) without omission of significant risk factors found to influence outcome.