Analysis of magnetic resonance spectroscopy relative metabolite ratios in mild traumatic brain injury and normative controls.

Introduction: We evaluated magnetic resonance spectroscopy (MRS) in United States military personnel with persistent symptoms after mild traumatic brain injury (mTBI), comparing over time two groups randomized to receive hyperbaric oxygen or sham chamber sessions and a third group of normative controls.

Methods: Active-duty or veteran military personnel and normative controls underwent MRS outcome measures at baseline, 13 weeks (mTBI group only), and six months. Participants received 3.0 Tesla brain MRS for analysis of water-suppressed two-dimensional (2D) multivoxel 1H-MRS of the brain using point resolved spectroscopy (PRESS) with volume selection localized above the lateral ventricles and within the brain parenchyma, of which one voxel was chosen in each hemisphere without artifact. Script-based automatic data processing was used to assess N-acetylaspartate (NAA), creatine (Cr), and choline (Cho). Metabolite ratios for white matter were then calculated for NAA/Cr (Area), Cho/Cr (Area), and Cho/NAA (Area). These ratios were compared using standard analysis methodology.

Results: There were no observable differences between participants with mTBI and normative controls nor any observable changes over time in the NAA/Cr (area), Cho/Cr (area), and Cho/NAA (area) ratios. Similarly, the control and injured participants were indistinguishable.

Discussion: While participants with mild TBI showed no difference in MRS compared to normative controls, our results are limited by the few voxels chosen and potentially by less sensitive MRS markers.