Background: Aneurysmal subarachnoid hemorrhage is one of the most serious neurosurgical conditions. There are a few studies in Thai population.

Objective: To investigate factors related to poor outcome after cerebral aneurysms clipping and establish a risk score model to predict unfavorable outcome.

Material and Method: A nested case-control study was conducted from cohort data between January 2010 to December 2016 at Her Royal Highness Princess Maha Chakri Sirindhorn Medical Center and Saraburi Hospital. One hundred and sixtyeight aneurysmal subarachnoid hemorrhage patients were enrolled in the study. Surgical outcome was assessed by Glasgow Outcome Scale (GOS). The number of the case per control was 1:1. Factors associated with unfavorable outcome were analyzed. A risk score model was developed by backward stepwise binary logistic regression analysis, and the Receiver Operating Characteristic (ROC) curve was constructed.

Results: Factors associated with poor outcome were the Modified Fisher grading scale of grade 3 or 4 (OR 17.8; 95% CI 6.8 to 46.7), the best motor response of Glasgow Coma Scale M4 or M5 (OR 8.1; 95% CI 3.2 to 20.4), and age of patients over than 60 years (OR 3.2; 95% CI 1.2 to 8.4). The final risk score model = 1 (age over than 60) +2.5 (GCS M4 or M5) +5.5 (Modified Fisher grading scale 3 or 4). The corresponding ROC for the accuracy of predicting the unfavorable outcome was 0.91; 95% CI 0.86 to 0.95 (p<0.001).

Conclusion: The simple risk score model based on three independent factors (Modified Fisher grading scale of grade 3 or 4, the best motor response of GCS being M4 or M5, and the age of the patients >60 years) was created to predict unfavorable outcome.

Keywords: Cerebral aneurysm, Aneurysmal subarachnoid hemorrhage, Cerebral aneurysm clipping outcome, Outcome predictive model, Risk score model