Patients with ischemic stroke in the posterior circulation continue to have high rates of mortality and disability, even with aggressive treatment. We wanted to evaluate preoperative imaging to screen patients with a good prognosis from mechanical embolization. We assess the degree of ischemia by defining the pons-midbrain-medulla index (PMMI) and correlate the preoperative PMMI with the clinical prognosis of postoperative patients to verify the validity of PMMI in predicting the clinical prognosis of patients with embolization.