Impact of Diabetes on Collateral Circulation and Thrombectomy Outcomes in Acute Ischemic Stroke: A Prospective Cohort Study.

Background: In large-vessel occlusion (LVO) stroke, mechanical thrombectomy (MT) restores flow yet outcomes vary. Collateral robustness and the metabolic milieu especially diabetes may shape tissue rescue, but the diabetes-collateral link and its impact on recovery remain uncertain. Objective: To determine whether pre-existing diabetes is independently associated with (1) poorer angiographic collateral status at baseline and (2) higher 90-day functional dependence after mechanical thrombectomy, and to evaluate whether collateral grade modifies the diabetes-outcome relationship after accounting for baseline infarct core volume, stroke territory, and reperfusion success. Methods: Prospective cohort of 41 adults with acute ischemic stroke (AIS) undergoing MT. Collaterals were graded using the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) score for anterior circulation and the Basilar Artery on Computed Tomography Angiography (BATMAN) score for posterior circulation. The primary analysis prespecified anterior strokes (n=33). The primary endpoint was 90-day functional dependence (modified Rankin Scale (mRS) 3-6). Multivariable logistic regression adjusted for clinical, imaging, and procedural covariates; sensitivity analyses included all strokes with a posterior-circulation indicator. Results: Diabetes was present in 59%. In the anterior subgroup, patients with diabetes more often had poor collaterals (45.0% vs 7.7%) and higher functional dependence (60.0% vs 15.4%), with similar reperfusion rates. In adjusted models, baseline diffusion-weighted imaging (DWI) core independently predicted poor outcome (per 10 cc: odds ratio (OR) 2.85; p=0.012), while diabetes showed a large but imprecise association (OR 19.02; p=0.081). The modified Thrombolysis in Cerebral Infarction (mTICI) grade was not independently significant. In the full cohort, posterior location (OR 19.33; p=0.045) and DWI core (OR 3.02; p=0.004) remained associated; diabetes trended similarly (OR 12.25; p=0.064). Conclusions: Diabetes clusters with weaker collaterals, larger cores, and greater disability despite high reperfusion. Tissue burden, not angiographic grade, chiefly drives outcomes. Metabolic phenotyping and pragmatic glycemic stewardship warrant testing.