Mona Adel Mohamed MD,PHD, Presenter: Nothing to Disclose

Richard Skolasky MA, Abstract Co-Author: Nothing to Disclose

Richard T Moxley BA, Abstract Co-Author: Nothing to Disclose

Martin Gilbert Pomper MD, PhD, Abstract Co-Author: Nothing to Disclose

Peter Blakeley Barker DPhil, Abstract Co-Author: Nothing to Disclose

Ned C Sacktor MD, Abstract Co-Author: Nothing to Disclose

The pathophysiology of HIV-associated dementia has been extensively studied using Magnetic Resonance Spectroscopy(MRS) at field strengths of 1.5 Tesla. At higher magnetic field strengths (such as 3.0T), increased sensitivity and chemical shift dispersion allow for more reliable determination of compounds such as glutamate and glutamine compared to 1.5T. Reduced glutamate uptake has been demonstrated in astrocytes exposed to HIV and postulated to be a contributory factor to the development of neurological involvement. This study was therefore undertaken to determine 3.0T brain glutamate and glutamine levels in HIV patients with different degrees of neurocognitive impairment.

Twenty five HIV+ subjects(19 males,6 females;34-54 years) were stratified into 3 groups according to their cognitive status:9 with normal cognitive function, 8 with minor cognitive motor disorder (MC/MD), and 8 with HIV-associated dementia(HAD). Short TE Single voxel MRS was acquired from the left frontal white matter (FRWM) and the left basal ganglia (BG) with and without water suppression using a 3.0T Philips scanner and SENSE-head coil. Voxel size was 22x22x22 mm3. Spectra were analyzed using the LCModel and quantified (in mM concentrations) relative to the unsuppressed water signal. Between group differences in metabolite concentrations and ratios (relative to creatine) were evaluated using ANOVA.

Combined glutamate and glutamine (Glx) was significantly lower in FRWM in HAD (8.0±3.47 mM) and MC/MD (10.4±1.5 mM) as compared to the subjects with normal cognitive status (11.0±0.7 mM) (p=0.027). In addition, consistent with prior 1.5T studies, there was a significant decrease in the concentration of FRWM N-acetyl aspartate, and increase in the BG myo-inositol/creatine ratio, in the HAD group.

This study shows that in patients with HIV, as cognitive impairment advances, FRWM Glx (predominantly due to glutamate) decreases. The underlying cause of decreased Glx is uncertain, but it may reflect neuroaxonal loss or dysfunction.

MRS using 3T allows better metabolites dispersion and thus is better in detecting glutamate/glutamine which could be a useful marker in evaluating AIDS dementia.

Mohamed, M, Skolasky, R, Moxley, R, Pomper, M, Barker, P, Sacktor, N, Abnormal Glutamate and Glutamine Levels in HIV Associated Dementia: A 3-Tesla Magnetic Resonance Spectroscopy Study.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4428078.html