Role of neuroimaging in HIV-associated neurocognitive disorders

Abstract

Human immunodeficiency virus (HIV) enters the brain soon after seroconversion and can cause HIV-associated neurocognitive disorders (HAND). Although the more severe and progressive forms of HAND are less prevalent due to combination antiretroviral therapy (cART), ∼ 40% of HIV-infected (HIV+) patients continue to have cognitive impairment. Some HIV+ individuals who have effective plasma HIV-1 RNA suppression with cART still develop HAND. It is often difficult to diagnose HAND in the outpatient setting as detailed neuropsychological performance testing is required. Additional biomarkers that are relatively easy to obtain and clinically relevant are needed for assessing HIV-associated neuropathologic changes. Recently developed noninvasive magnetic resonance imaging (MRI) techniques have great potential to serve as biomarkers. The authors review the application of some of these neuroimaging techniques, magnetic resonance spectroscopy (MRS), volumetric MRI, diffusion tensor imaging (DTI), functional MRI (fMRI), in HIV+ individuals. Each of the neuroimaging methods offers unique insight into mechanisms underlying neuroHIV, could monitor disease progression, and may assist in evaluating the efficacy of particular cART regimens. It is hoped that considerable progress will continue to occur such that some of these neuroimaging methods will be incorporated across multiple sites and included in future HAND guidelines.

Figure 1

Freesurfer segmentation of cortical (A) and subcortical (B) regions of the brain. (C) Comparison of volumes from the right caudate for HIV− controls and HIV+ patients. Overall, HIV+ patients had significantly smaller volumes (p < 0.05)

Figure 2

Voxelwise comparisons for fractional anisotropy (FA) (A) and mean diffusivity (MD) (B) between HIV− controls and HIV+ patients using Tract-Based Spatial Statistics (TBSS). Red: p=0.05; Orange: p=0.03; Yellow: p=0.01.