Diffusion Tensor Imaging Analysis Along the Perivascular Space (DTI-ALPS) as an Imaging Biomarker of Glymphatic Dysfunction in Gliomas: A Systematic Review and Meta-Analysis

BACKGROUND: Diffusion tensor imaging analysis along the perivascular space (DTI-ALPS) is an noninvasive MRI biomarker of perivascular/glymphatic diffusivity. Although individual studies suggest that gliomas are associated with disrupted glymphatic function, the magnitude and consistency of DTI-ALPS alterations have not been systematically evaluated. PURPOSE: To systematically evaluate DTI-ALPS-index differences between glioma patients and healthy controls and to investigate associations with tumor grade, Isocitrate Dehydrogenase(IDH) mutation status, and tumor laterality. DATA SOURCES: PubMed, Embase, and Scopus were searched from database inception through May 2026. STUDY SELECTION: Human studies reporting DTI-ALPS-index values in glioma patients and healthy controls were included. DATA ANALYSIS: Mean differences(MDs) were pooled using random-effects inverse-variance meta-analysis. DATA SYNTHESIS: =78%) were not statistically significant. Exploratory sensitivity analyses excluding one influential cohort yielded statistically significant grade-, IDH-, and laterality-based differences with reduced heterogeneity; however, these findings were dependent on cohort exclusion and should be considered hypothesis-generating. LIMITATIONS: The evidence is limited by few studies, high heterogeneity, methodological differences in DTI-ALPS measurement, and observational study designs, with some subgroup results changing when individual cohorts are excluded. CONCLUSIONS: Gliomas are associated with reduced DTI-ALPS-index values compared with healthy controls, indicating impaired perivascular/glymphatic diffusivity. However, associations with tumor grade, IDH status, and laterality remain uncertain due to heterogeneity and sensitivity to individual studies. DTI-ALPS is a promising noninvasive biomarker of disease-associated brain-fluid transport dysfunction, but requires prospective validation, including in studies of transport-modulating interventions.