Proton magnetic resonance spectroscopy (1HMRS) in HIV infection

Combined study of magnetic resonance imaging (MRI) and proton resonance spectroscopy (1II-MRS) ( Magnetron Siemens 1.5 tesla) was performed in 60 HIV seropositive patients and in 22 HIV seronegative neurological controls. Brain MRI showed focal lesions suggestive of toxoplasmosis in n. 20 patients, PML in n. 8 and lymphomas in n. 7 patients; in n. 25 patients diffuse white matter abnormalities and atrophy on MRI were related to HIV-encephalopathies. Spectra were aquired on a single volume of interest localized on focal or diffuse brain lesions. Choline, creatine, N-acetyl aspartate and lactate were evaluated in each spectrum and NAA/Cr and Cho/Cr were calculated. In comparison to neurological controls a significant decrease in NAA/Cr ratio was found in each HIV subgroup, suggesting neuronal and/or axonal damage independently of brain lesions aetiology. However NAA/Cr was significantly lower in PML and in lymphomas than in other HIV subgroups. A significant increase was associated with the presence of the lipid signal, both constituents of cell membranes, and markers of increased membrane turnover. Lactate signal was found with a significant high frequency in PML lesions. These data suggest that 1H-MRS may be considered a sensitive means to evaluate brain metabolic involvement during HIV infection. Although the overall specificity appears to be poor in defining the aetiology of different brain lesions, homogenous biochemical patterns could support MRI in the differential diagnosis of some lesions such as PML.