Combined multiphase CTA and CTP in assessing cerebral collateral circulation and predicting prognosis in AIS/TIA with symptomatic MCA M1 stenosis/occlusion: a subacute, non-reperfused cohort

Purpose: Accurate assessment of collateral circulation is essential for individualized treatment in ischemic cerebrovascular disease. This study aims to establish a comprehensive evaluation of cerebral collateral circulation and predict functional outcomes. Methods: This multicenter prospective cohort study enrolled patients with acute ischemic stroke (AIS) or transient ischemic attack (TIA) due to symptomatic intracranial atherosclerotic stenosis (sICAS), presenting within 7 days of symptom onset without acute thrombolysis or thrombectomy. All underwent multimodal CT imaging and had significant stenosis/occlusion of the middle cerebral artery (MCA) M1 segment. Collateral structure was evaluated via multiphase CTA (mCTA) score, and collateral function by average Tmax delay time between bilateral MCA territories. Patients were categorized into four groups: C (+) (good structure+function), C (-) (poor structure+function), C (mix1) (poor structure, good function), and C (mix2) (good structure, poor function). The primary outcome was modified Rankin Scale (mRS) score 0-2 at 90 days. A nomogram was constructed to predict this outcome, incorporating mCTA score, delay time, and other relevant clinical risk factors. Results: 471 patients were included: 191 in C (+) group, 45 in C (mix1) group, 128 in C (mix2) group, and 107 in C (-) group. Multivariate analysis revealed that C (+) group was significantly associated with mRS 0-2 at 90 days (adjusted odds ratio [aOR] 2.58, 95% CI 1.06-6.40; p = 0.04 vs. C [-]). The nomogram model showed good calibration and discrimination, with a C-statistic of 0.85 (95% CI 0.80-0.89). Conclusion: A favorable comprehensive collateral profile is associated with better functional outcomes.