Diffusion Tensor Imaging Analysis Along the Perivascular Space (DTI-ALPS) in Normal Pressure Hydrocephalus: A Review of Recent Advances

Abstract

Glymphatic dysfunction is linked to neurodegenerative diseases, and imaging markers of this dysfunction may aid in diagnosis and prognosis. Glymphatic dysfunction has been proposed as a key mechanism in the pathogenesis of normal pressure hydrocephalus (NPH). Advanced magnetic resonance techniques, especially diffusion tensor imaging, have been used to evaluate glymphatic function. Diffusion tensor imaging analysis along the perivascular space (DTI-ALPS) is a noninvasive metric that correlates with glymphatic function and has been recently studied in a variety of neurodegenerative diseases. We aim to summarize studies evaluating the association between DTI-ALPS index values and NPH diagnosis and outcomes. Current studies suggest lower DTI-ALPS index values in NPH patients compared to healthy controls. The DTI-ALPS index correlated with other imaging-based markers of NPH and clinical endpoints. However, limitations of the current literature include small cohort sizes; future studies are needed in larger, heterogeneous cohorts to validate these trends. Thus, the DTI-ALPS index shows promise as a valuable tool for diagnosing NPH, predicting treatment response, and assessing disease progression.

Keywords: biomarkers; brain; diffusion tensor imaging; neuroimaging; normal pressure hydrocephalus.

Figure 1. ROI placement for DTI analysis

Axial MRI of the head demonstrating diffusion tensor tracks. ROIs are placed in the left and right hemispheres in the projection and association areas for DTI-ALPS index calculation. DTI, diffusion tensor imaging; DTI-ALPS, diffusion tensor imaging analysis along the perivascular space; ROI, region of interest The image was generated using 3D Slicer software, Version 5.8.1 (3D Slicer, Earth, TX, USA).