Enhanced Benefit of STA-MCA Bypass Surgery in Chronic Terminal Internal Carotid and/or Middle Cerebral Artery Occlusion Patients With Impaired Collateral Circulation: Introducing a Novel Assessment Approach for Collateral Compensation.

Background: Ischemic stroke is one of the major emergency diseases leading to death and disability worldwide, characterized by its acute onset and the urgent need for prompt medical intervention to reduce mortality and long-term disability. Chronic terminal internal carotid artery and/or middle cerebral artery occlusion (CTI/MCAO) is an important subtype of intracranial artery occlusive disease. The superficial temporal artery-to-MCA (STA-MCA) bypass has been proposed to improve cerebral blood flow (CBF) and cerebrovascular reserve (CVR), potentially enhancing neurological outcomes. However, its safety and efficacy in CTI/MCAO patients remain controversial. Methods: A total of 107 CTI/MCAO patients from Nanjing Brain Hospital, enrolled between July 2019 and June 2022, were divided into surgical and medical treatment groups. Cerebral perfusion and collateral formation were evaluated using pseudocontinuous arterial spin labeling (pCASL) and digital subtraction angiography (DSA). Modified Rankin scale (mRS) score and complication rates were compared between the two groups. In addition, correlations between Matsushima grades, early-arriving flow proportion (EFP), and lesion-side cerebrovascular (LCBV) scores were analyzed. Results: The surgical group showed significantly lower mRS scores than the medical group (p=0.018), with no significant differences in complication rates at the 6-month follow-up (p=0.861). CBF differed significantly among affected MCA segments (p < 0.001), particularly in the insular and opercular regions (M2-M3) (p=0.006). Matsushima grades in unilateral CTI/MCAO patients were negatively correlated with preoperative LCBV scores (γ _s = -0.468, p=0.005) and EFP (γ _s = -0.648, p=0.007). EFP demonstrated high accuracy in predicting LCBV scores in CTI/MCAO patients (AUC = 0.902, p=0.004). Conclusion: STA-MCA bypass surgery improved neurological outcomes in CTI/MCAO patients, particularly those with poor preoperative collateral compensation. EFP may serve as a reliable, noninvasive tool for assessing collateral circulation status in this population.