Analysis of the effects of injecting drug use and HIV-1 infection on ¹⁸F-FDG PET brain metabolism

Injecting drug use (IDU) is a major risk factor for contracting HIV-1 infection. Both HIV and IDU are neurotoxic, and their coexistence may lead to increased dysfunction of brain metabolic processes. The objective of this research was to investigate the effects of HIV-1 infection and IDU on ¹⁸F-FDG PET brain metabolism. Methods: ¹⁸F-FDG PET brain imaging, with a standard clinical protocol, was performed on 59 subjects who belonged to 3 groups: HIV-positive/IDU-positive (n = 17), HIV-negative/IDU- positive (n = 13), and HIV-negative/IDU-negative controls (n = 29). A voxel-based analysis of the ¹⁸F-FDG PET brain images was performed using statistical parametric mapping. The imageswere spatially normalized to a standard ¹⁸F-FDG template, proportionally scaled to compensate for count differences, and then appropriately smoothed. Statistical 2-sample t tests were performed to determine regional metabolic distribution differences in the 3 groups. Results: Diffuse hypermetabolism in the subcortical and deep white matter, the basal ganglia, and the thalami was observed in HIV-1 infection. IDU resulted in increased brainstem metabolism and decreased activity in cortical structures including bilateral medial frontal lobes and the right inferior frontal and temporal cortices. The cortical hypometabolism was more extensive in HIV-1-infected subjects, involving the left temporoparietal and right parietal cortices and bilateral medial frontal lobes. Conclusion: Voxel-based analysis of ¹⁸F-FDG PET brain images demonstrated statistically significant differences in regional metabolism for the 3 studied groups. It also showed that HIV-1 infection may have a synergistic effect with IDU, resulting in more extensive cortical hypometabolism. Correlation of these findings with other quantitative approaches and neurocognitive functioning is warranted.