By conducting a review of clinical outcomes for patients with aneurysms treated using current microneurosurgical techniques and intensive care unit management, we determined that grading systems based only on the clinical condition of the patient failed to produce a significant stratification of outcome between individual grades of patients. We hypothesized that outcome prediction for patients surgically treated for intracranial aneurysms could be improved by including factors other than clinical condition that were also strongly associated with outcome.
To identify potential factors for inclusion in a risk prediction tool, we conducted a multivariate logistic regression analysis of patient- and lesion-specific factors suspected to be associated with outcome in a series of 434 aneurysm operations. Factors that were strongly associated with outcome were used to develop a comprehensive grading system. In the system, 1 point is assigned for Hunt and Hess Grade IV or V, Fisher Scale score of 3 or 4, aneurysm size greater than 10 mm, patient age older than 50 years, and if the lesion is a giant (≥25 mm) posterior circulation lesion. By adding the total points, a 5-point grading system (Grades 0-5) is obtained.
Age of patient, size of aneurysm, severity of subarachnoid hemorrhage(Fisher Scale evaluation of density of blood present as revealed by computed tomography), and clinical condition (Hunt and Hess grade) were each independently and strongly (relative risk, >4) associated with long-term outcome. In addition, there was a trend for increased risk with larger(>25 mm) posterior circulation lesions. When applied to the study population, individual grades on the new grading scale correlated well with actual outcome. In a prospective assessment of the system as applied to an additional 72 operations with at least 1 year of follow-up, the correlation of individual grades and outcome was strong and validated the retrospective findings.
This new grading system is easy to apply, separates patients into groups with markedly different outcomes, and is comprehensive, allowing for more accurate prediction of surgical outcome for both unruptured and ruptured cerebral aneurysms.