Abstract
Major depressive disorder is a common mental disorder and is characterized by experiencing
a depressed mood and thoughts of hopelessness or suicide. Bipolar disorder is a mental illness that causes changes in a person’s mood, energy, and activity levels. Electroconvulsive Therapy (ECT) and Transcranial Magnetic Stimulation (TMS) are treatment options for treatment-resistant depression and bipolar disorder. Volume changes in areas like the hippocampus are common findings in ECT studies. There are fewer studies of volume change after TMS, but volume changes in the hippocampus have been found. Studies on brain perfusion, or Cerebral Blood Flow (CBF), after ECT are sparse and primarily focus on how perfusion correlates with clinical outcome.
This study aims to investigate if there is a connection between changes in brain perfusion and volume changes in areas of the brain. The hypothesis is that the ECT and TMS treatment will increase volume in specific brain regions and that these areas will experience a change in perfusion.
FreeSurfer and FSL BASIL were used to analyze the images. FreeSurfer was used for image segmentation and volume quantification, while FreeSurfer and FSL BASIL were used for perfusion quantification. A pipeline was established to analyze the data, and statistical analyses were performed to find statistically significant changes.
The results showed a statistically significant volumetric increase in the left (2.8%, p=0.0043) and right hippocampus (4.3%, p=0.0001), right amygdala (4.3%, p=0.0002), and right thalamus (1.8%, p=0.0202) for the ECT group. However, only the right hippocampus and right amygdala passed a Bonferroni correction (p<0.0026). The TMS group showed a statistically significant volumetric increase in the right hippocampus (1.8%, p=0.0342) and right thalamus (1.5%, p=0.0482), but none of the areas passed the Bonferroni correction. The perfusion analyses were combined for the Hippocampus, Amygdala, and Thalamus (HAT), because more gross changes were assumed compared to the volumetric changes. Still, the analyses were preformed separately for the two hemispheres. There were no statistically significant changes between the groups at baseline perfusion, and none of the groups showed a statistically significant longitudinal increase or decrease. There were also no statistically significant differences across the hemispheres. Although not significant, there were trends showing a decrease in perfusion in the ECT group when investigating the rate of change in percent (%). Similarly, in the TMS group, trends showing a slight decrease followed by an increase were seen for the percent changes (%). There were also trends showing an increased baseline perfusion for the ECT group in both hemispheres. When more participants are included in the overall study, it can be verified whether these trends are true or random variations, as there were few participants at the time of the analysis and the perfusion data have larger variations than the volumetric data. The established pipeline can process image data from new participants as they join the study.
