Depression and somatic improvement following rTMS therapy may be predicted by Glx/tCr ratio – preliminary findings

Motivation: Recently Glx (glutamate+glutamine)/ tCr (total creatine) ratio at dorsolateral prefrontal cortex (DLPFC), target of repetitive transcranial magnetic stimulation (rTMS), has been suggested to be a biomarker in predicting efficacy of clinically standard rTMS treatment in adults with inadequately treatment responsive major depressive disorder. The improvement was assessed based upon composite Hamilton depression (HAMD) scale but a symptom-based analysis was lacking. Goal(s): To identify HAMD components whose changes can be predicted by Glx/tCr ratio. Approach: Glx/tCr obtained from single voxel MRS using MEGA-PRESS at 3-tesla was correlated with symptom-based components. Results: Improvements of depression and somatic components were associated with Glx/tCr ratio. Impact: Hamilton depression (HAMD) scale is a composite measure. Findings from this study identified specific symptom-based components of HAMD that are specifically changed depending on dorsolateral prefrontal cortex (glutamate+glutamine)/creatine ratio. This may help in mechanistic understanding of rTMS therapy.