Diffusion Tensor Imaging for Interpreting Fractional Anisotropy and Mean Diffusivity in Normal-appearing White Matter of Patients with HIV-associated Neurocognitive Disorders: A Case-control Study

Abstract

Introduction: {Human Immunodeficiency Virus (HIV)-associated Neurocognitive Disorder (HAND)} affects the everyday functioning of patients. It is usually difficult to diagnose HAND in the outpatient setting as detailed neuropsychological performance testing, such as the International HIV Dementia Scale (IHDS), is required. Neuroimaging techniques hold great promise in the early diagnosis and management of HAND, but there is a paucity of studies on the evaluation of HAND using Diffusion Tensor Imaging (DTI) in the Indian population. Aim: To investigate DTI and interpret Fractional Anisotropy (FA) and Mean Diffusivity (MD) values in the White Matter (WM) of patients with HAND and compare them with age and sex- matched controls. Materials and Methods: A case-control study was conducted at the Department of Radiodiagnosis, ABVIMS and Dr. RML Hospital, New Delhi, India, from January 2021 to May 2022. Thirty subjects (15 cases and 15 controls) were included. HIV-positive patients underwent the IHDS to assess cognitive impairment. Magnetic Resonance Imaging (MRI) examination was performed at three tesla using conventional sequences, and DTI was applied. Maps of FA and MD values were generated. Mean FA and MD values of normal-appearing white matter tracts between cases and controls were compared using a t-test. Spearman's correlation test was applied to assess the correlation between IHDS scores and DTI parameters. Results: The majority of cases in the study were in the age group of 31-40 years, and the mean age of cases was 41.27±11.16 years. The present study revealed significantly lower FA values compared to controls in bilateral Frontal WM, Parieto-occipital WM, genu of the Corpus Callosum (CC), right hippocampal WM, and right corona radiata. The mean MD of bilateral Frontal WM, Parieto-occipital WM, corona radiata, and Hippocampal WM was significantly increased in cases compared to healthy controls. A significant association was found between the IHDS score and FA values of the genu of the CC (rho= 0.7), right corona radiata (rho= 0.7), right Hippocampal WM (rho= 0.9), and MD of the left Parieto-occipital WM (rho= -0.6), and left hippocampal WM (rho= -0.5). Conclusion: Diffusion tensor MR imaging can detect abnormalities that are missed by routine MR imaging. DTI provides a valuable marker to monitor HIV-associated Central Nervous System (CNS) injury, which can lead to neurocognitive impairment.