Introduction: Cognitive decline affects a large proportion of patients with ischemic stroke. Intracranial atherosclerotic disease (ICAD) is a common stroke etiology associated with a high and prolonged risk of recurrence. In the ERSIAS phase-II trial, patients with symptomatic ICAD received revascularization with encephaloduroarteriosynangiosis (EDAS) plus intensive medical management (IMM) of stroke risk factors. We present a subgroup analysis of features affecting cognitive outcomes. Hypothesis: To evaluate the factors contributing to cognitive decline in patients who underwent revascularization for symptomatic ICAD. Methods: ERSIAS patients without aphasia that completed at least one year of follow-up were included. Cognitive status was evaluated using MoCA at baseline and each follow-up and classified as improved/preserved vs. worsened. Classification and Regression Tree Analysis (CART) was used to identify factors associated with changes in cognitive function. Factors considered were age, sex, stenosis vs. occlusion, baseline-mRS, good collateralization and compliance with diabetes (DM) hypertension (HTN), and hyperlipidemia (HLD) treatments. Results: In ERSIAS, the mean MoCA at baseline was 22.4 (SD 4.9), and 23.9 (SD 4.9) at one-year follow-up in the complete population. Thirty-nine patients were included in this analysis. Median age was 46 (IQR 37.0-56.0), and 27 (69.2%) were female. MoCA improved or remained stable in 33 (84.6%) patients and declined in 6 (15.4%). CART analysis revealed that the most relevant factors for improved MoCA were compliance with DM treatment (94.5%(yes) vs.74.2%(no) p=0.02) HLD treatment (83.3% (yes) 60.5%(no) p=0.2) and stenosis 99.1% vs. occlusion 80.9%, p=0.6 Other factors where not found to be contributory. Conclusions: Compliance with DM treatment is a significant predictor of cognitive preservation in symptomatic ICAD patients. Our findings emphasize the importance of IMM of stroke risk factors in patients with intracranial atherosclerosis, even after surgical revascularization.