Elevated Tmax >4 Seconds Volume Predicts Worse Functional Outcome Following Endovascular Treatment in M2 Middle Cerebral Artery Occlusion.

BACKGROUND AND PURPOSE: Acute ischemic stroke (AIS) due to M2 middle cerebral artery (MCA) occlusion represents the most frequent medium vessel occlusion (MeVO), yet the benefit of EVT in these patients remains uncertain. The perfusion parameter Tmax >4 seconds reflects delayed contrast arrival and captures regions of hemodynamic compromise that may include both potentially salvageable tissue and areas at risk of infarction if reperfusion is delayed or incomplete. This study therefore aims to evaluate whether the Tmax > 4s volume perfusion deficit predicts functional outcomes in patients with M2 occlusions who undergo EVT. MATERIALS AND METHODS: For this retrospective multinational study, AIS patients with M2 MCA occlusion who underwent EVT were included. We performed univariable and multivariable logistic regression analysis to predict the mRS outcomes 90 days after the stroke (90-day mRS), based on the Tmax > 4s volume and adjusting for age, admission NIHSS, ASPECTS, intravenous thrombolysis (IVT), and modified thrombolysis in cerebral infarction grading (mTICI). RESULTS: 130 M2 AIS patients were included, with a median age of 75.5 (65-81.75). The model based on Tmax > 4s volume had an area under the curve (AUC) of 0.81 (95% CI, 0.73-0.88). The optimal Tmax >4s volume threshold was 113 mL, which demonstrated the highest performance for discriminating between outcomes. Among the participants, ASPECTS (p = 0.03) was significantly lower and 90-day mRS (p = 0.05) was significantly higher in the Tmax > 4s greater than 113 ml volume patient cohort. In the multivariable logistic regression analysis, higher Tmax > 4s volume (OR: 0.24; 95% CI: 0.08-0.70) and higher admission NIHSS (OR: 0.88; 95% CI: 0.81-0.96) were independently associated with lower odds of favorable outcome (mRS 0-2), while successful EVT was a protective factor (OR: 6.10; 95% CI: 1.80-20.64). CONCLUSIONS: Our results demonstrate that Tmax > 4s serves as a quantitative marker for predicting mRS outcomes in M2 AIS patients who underwent EVT. When considered alongside established clinical variables, this metric may provide complementary prognostic information.