[Regional effects of age and sex in magnetic resonance spectroscopy].

Objective: To determine the regional effects of age and sex on the metabolic ratios obtained in the medial temporal lobe, the posteromedial region, and the frontal lobe at 1.5 T single-voxel magnetic resonance spectroscopy.

Material And Methods: We used single-voxel magnetic resonance spectroscopy to study the areas of the brain most affected in neurodegenerative disease (the left frontal lobe, the left medial temporal lobe, and the posteromedial region) in 31 healthy subjects older than 55 years of age (group 1) and in 20 healthy subjects under 30 years of age (group 2). We calculated the following ratios for each voxel: N-acetyl-aspartate/creatine-phosphocreatine (NAA/Cr), N-acetyl-aspartate/choline (NAA/Cho), N-acetyl-aspartate /myoinositol (NAA/mI), choline/creatine-phosphocreatine (Cho/Cr), and myoinositol (mI/Cr). We compared the metabolic ratios in each region in each group and the correlation between age and the ratios within age ranges. Finally, we analyzed the differences in the metabolic ratios between groups and between sexes.

Results: In group 1, we found negative correlations between age and Cho/Cr in the frontal region and NAA/mI in the temporal region. In group 2, we found negative correlations between age and mI/Cr and NAA/Cho in the temporal region as well as a positive correlation between age and NAA/mI in the temporal region. In the frontal lobe and the posteromedial region, NAA/Cr, NAA/Cho, and NAA/mI were lower in group 1 (P≤0.003). No differences between groups were seen in Cho/Cr or mI/Cr. The values of the ratios differed regionally in all cases (P<0.001). In the temporal lobe, NAA/Cr and Cho/Cr were higher in women (P≤0.034).

Conclusions: When using single-voxel magnetic resonance spectroscopy, especially in patients with neurodegenerative disease, variations due to region, age, and sex should always be taken into account.