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Background: Although incidence of HIV -encephalopathy has declined since the introduction of HAART, many patients currently still present cognitive impairement. Proton magnetic resonance spectroscopy (MRS) is a well recognized method to evaluate early brain metabolism impairement in HIV infected patients.

Methods: Retrospective study of metabolic brain profile measured by MRS between 1994-1999 in 39 HIV-infected antiretroviral treated patients (zidovudine: n = 23 and/or lamivudine: n = 28 and /or stavudine: n = 13 and /or didanosine: n = 8 and/or protease inhibitors: n = 17). MRS was performed on a SP63 1.5T Siemens system, 135 ms PRESS single voxel sequence). Results of MRS were expressed as « normal or abnormal proton spectrum » and metabolic brain profile were analyzed according to dementia clinical stage, CD4 cell count, HIV viral load and antiretroviral therapy.

Results: Abnormal proton spectrum profile was observed in 19/39 patients (48.7%).

According to antiretroviral drugs, brain metabolic abnormality was significantly less frequent in patients treated with didanosine -drug regimen (ddI) (1/8 (12%) vs 18/31(58%) (p<0.02 c2 test) whereas these patients were more immunosupressed and have a high viral load.

Conclusions: ddI might have a specific effect on the neurochemical status of HIV-infected patients which allow both normalization of NAA levels (reduction of neuronal suffering), and/or decrease of choline levels (reduction of inflammatory and/or demyelinating processes).This brain metabolic effect of ddI seems not related to its antiretroviral activity. Studies are still required to examine the impact of individual therapeutic agents and differents regimens on HIV-encephalopathy. Particulary in regard of our study, it is necessary to confirm these results and evaluate if didanosine prevents the direct neurotoxic effect of gp120 protein (and/or action on glutamate clearance) or  has an effect on inflammatory processes.

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Keywords: Encephalopathy; HIV