Structural and metabolic changes in the anterior cingulate cortex (ACC) after treatment with repetitive transcranial magnetic stimulation (rTMS) in patients with treatment-resistant unipolar depression (TRD)

Morphological & biochemical alterations of the ACC have been reported in depressive disorders. Application of rTMS may reduce depressive symptoms & seems to have an effect on brain structure. Objective of the study was to investigate metabolic & structural effects of rTMS on the ACC in TRD patients. 33TRD patients were scanned (3T-MRI) prior (T1) & after 20 active (n = 17) or sham-rTMS-sessions (n = 16) during 4 weeks (T2). MRI data contains 1 H-MRS to determine NAA/Creatin ratio, DWI to assess WM integrity by mean FA, & structural images to assess GMV changes. Results were compared with 12HC. Depressive symptoms were assessed by means of clinical scales (CGI, BDI, HAMD). Patients (active/sham) did not differ in clinical outcome or MRI measures at T1. Clinical improvement was found in both groups (T2; p>.01). The mean GMV was sig. lower for the left ACC in patients as compared to HC (T1; p = 0.001). An increase of the left ACC GMV was only found for the active group at trend level (T2; p = 0.09). Patients' ACC NAA/Cr ratio was marginally lower as compared to HC (T1; p = 0.09). No sig. changes of the ACC NAA/Cr ratio were found in both treatment groups at T2. The mean FA did not differ between patients and HC at T1. There was a marginal increase of the ACC mean FA in the sham group (T2; p = 0.07). GMV & metabolites were found to be altered in patients as compared to HC. GMV & WM integrity were modified by rTMS at trend level, suggesting a possible mechanism of antidepressant action of rTMS in TRD.

This study was supported by the University Medical Center Gießen and Marburg (UKGM) grant 27/2015 MR, the Von Behring-Roentgen-Foundation grant 64 – 0016, and the Medical Center Rhoen AG grant FI22.