Objective:To explore the clinical application value of diffusion tensor image analysis along the perivascular space(DTI-ALPS)to assess the changes in the function of the glymphatic system(GS)in patients with intracranial large vessel stenosis or occlusion(LVSO).Methods:The clinical and imaging data of 45 patients with unilateral type LVSO and 45 healthy controls(HCs)were retrospectively analyzed.The ABCD2 scores were assessed for the 45 patients with LVSO,and diffusion tensor imaging(DTI)pa-rameters were utilized to calculate the DTI-ALPS indices for both groups.Additionally,the DTI-ALPS indices of both cerebral hemi-spheres in all subjects were computed to evaluate glymphatic system function changes in LVSO patients.Results:The DTI-ALPS index of the cerebral hemisphere on the lesion side of the LVSO group was lower than that on the healthy side and the healthy control group(P<0.001),and there was a negative correlation between the DTI-ALPS index of the cerebral hemisphere on the lesion side of the LV-SO group and the ABCD2 score(r=-0.69,P<0.001).Conclusion:The DTI-ALPS index can evaluate the changes in the function of the glial and lymphatic system in LVSO patients,and it is expected to become a new neuroimaging biomarker and evaluation tool for early risk assessment,diagnosis,treatment planning,and prognosis assessment of LVSO.It has important value in improving patients'quality of life,optimizing clinical outcomes,and saving medical resources.