1H MR spectroscopy of the brain in HIV-1-seropositive subjects: evidence for diffuse metabolic abnormalities

To analyze brain metabolite changes in HIV-1-seropositive subjects in order to define whether the neuronal impairment is a localized or more diffuse process.

15 patients and 18 volunteers underwent multivoxel proton magnetic resonance (MR) spectroscopy at 1.5T. Nine patients were classified as being neuropsychiatrically unimpaired and six as having HIV-1-associated dementia on the basis of a full neuropsychological examination. Spectra were analysed from multiple voxels located in the fronto-parietal cortex and white matter at the level of centrum semiovale.

A significant reduction in mean peak area ratios of NAA/Cr (p<0.005 in the grey matter, p<0.01 in the white matter) and an elevation in mean Cho/Cr (p<0.005 in both grey matter and white matter) were observed in patients with HIV-1-associated dementia when compared to healthy volunteers. No significant metabolite abnormalities were detected in the neuropsychiatrically unimpaired group, although there was a similar trend in the metabolite ratios. The changes in metabolite ratios were of the same order of magnitude in the cortical grey matter and subcortical white matter as in the deeper white matter in all patients. There were also no significant regional variations in mean metabolite ratios between right and left hemispheres or anterior and posterior voxels at the level of the brain studied. There were no abnormalities in Glx/Cr in any spectra analysed from either patient group.

The absence of significant regional variation in metabolite ratios at the level of the centrum semiovale provides some evidence that abnormalities of cerebral metabolites in HIV-infected patients may be part of a diffuse process.