A MRS study of metabolic alterations in the frontal white matter of major depressive disorder patients with the treatment of SSRIs

Abstract

Background: Proton magnetic resonance spectroscopy provides a non-invasive technology to study brain metabolite levels in vivo, which can be used to measure biochemical compounds or metabolite concentrations in circumscribed brain regions. Previous research has highlighted the role of glial cells in brain white matter. It has been assumed that antidepressant treatment with SSRIs not only affects neurons, but also activates glial cells. This study focused on the observation of any potential changes in the metabolite levels of the ventral prefrontal white matter in major depressive disorder (MDD) patients who have received antidepressant treatment.

Methods: 17 female patients diagnosed as MDD according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria with the scores of 18 and above on the 24-item Hamilton Depression Rating Scale (HDRS) were recruited. MRS studies were performed on a 3.0 T MR system, single voxel PRESS spectroscopy with chemical-shift selective saturation water suppression. The volume of interest was localized at the bilateral ventral prefrontal white matter regions (voxel size: 2 × 2 × 2 mm(3)). The spectral data analysis was performed by using the instrument manufacturer supplied software.

Results: The bilateral ventral prefrontal white matter of MDD patients showed significantly lower Cho/Cr (p < 0.05) before receiving treatment. The HDRS, as the indicator of treatment response, showed a significant decrease in patients who had gone through 12 weeks treatment (p < 0.01). The bilateral Cho/Cr values of post-treatment patients were increased significantly compared to that of pre-treatment (p < 0.05).

Conclusion: The alteration of ventral prefrontal white matter metabolite levels are likely involved in MDD pathophysiology and imply a crucial role of white matter in MDD.

Figure 1

Sagittal, coronal and axial scout MR images showing an 8-cm³ voxel predominantly centered white matter of the bilateral ventral prefrontal lobe.

Figure 2

Comparison of the same patient’s pre- (left) and post- (right) treatment Cho/Cr level.