Temporal trajectory of changes in cerebral volume and diffusion during and after the ECT-course

Objective: Electroconvulsive therapy (ECT) is an effective treatment for major depression, but mechanisms are largely unclear and there are concerns of cognitive side-effects. Insights into the evolution of cerebral changes using repeated magnetic resonance imaging (MRI) may elucidate mechanisms of side-effects and efficacy. We examined the temporal trajectory of changes in cerebral volume and diffusion during and after the ECT-course, including associations with cognitive outcome and efficacy.

Method: Prospective longitudinal data of depressed ECT-patients (n=30) were included. Structural and diffusion tensor imaging (DTI) MRI scans were acquired at baseline, directly after initial ECT-sessions, within two weeks after the course and at three months follow-up. Changes were corrected for test-retest effects by including matched healthy controls (HC, n=26). Linear and nonlinear changes in grey matter (GM) volume, white matter (WM) volume, mean diffusivity (MD) and fractional anisotropy (FA) were assessed. Early brain changes were associated with cognitive and efficacy outcomes.

Results: After the 3rd ECT-session (n=19), GM volumes of amygdala and hippocampus significantly increased accompanied with right lateralized MD decrease in those areas. In contrast, WM MD significantly increased. Within two weeks after the ECT-course (n=30), global cortical GM volume increase was observed, which returned to baseline after three months. In WM, linear increases of MD without widespread changes of FA were found after the ECT-course, which did not return to baseline at three months follow-up (n=30). ECT transiently decreased verbal learning, letter fluency and animal category fluency tests (n=23, pbonferroni = 0.04; n=22, pbonferroni = 0.04; n=62, pbonferroni = 0.02, respectively). Early volume and diffusion changes were not associated with decreases in cognitive performance or efficacy.

Conclusion: ECT seems to induce rapid changes in brain microstructure and macrostructure. But while macroscopic increases appeared temporary, the microscopic changes in brain structure seemed longer-lasting.