Distinct and shared patterns of brain plasticity during electroconvulsive therapy and treatment as usual in depression: an observational multimodal MRI-study

Abstract

Electroconvulsive therapy (ECT) is a highly effective treatment for depression. Previous studies point to ECT-induced volume increase in the hippocampi and amygdalae, and to increase in cortical thickness. However, it is unclear if these neuroplastic changes are associated with treatment response. This observational study aimed to address this research question by comparing neuroplasticity between patients with depression receiving ECT and patients with depression that respond to treatment as usual (TAU-responders). Twenty ECT-patients (16 major depressive disorder (MDD), 4 depressed bipolar disorder), 20 TAU-responders (20 MDD) and 20 healthy controls (HC) were scanned twice with multimodal magnetic resonance imaging (structure: MP2RAGE; perfusion: arterial spin labeling). ECT-patients were scanned before and after an ECT-index series (ECT-group). TAU-responders were scanned during a depressive episode and following remission or treatment response. Volumes and cerebral blood flow (CBF) of the hippocampi and amygdalae, and global mean cortical thickness were compared between groups. There was a significant group × time interaction for hippocampal and amygdalar volumes, CBF in the hippocampi and global mean cortical thickness. Hippocampal and amygdalar enlargements and CBF increase in the hippocampi were observed in the ECT-group but neither in TAU-responders nor in HC. Increase in global mean cortical thickness was observed in the ECT-group and in TAU-responders but not in HC. The co-occurrence of increase in global mean cortical thickness in both TAU-responders and in ECT-patients may point to a shared mechanism of antidepressant response. This was not the case for subcortical volume and CBF increase.

Electroconvulsive therapy induces remodeling of hippocampal co-activation with the default mode network in patients with depression

“…ECT-induces volume increases in the hippocampi ( Gryglewski et al, 2019 , Gryglewski et al, 2021 , Nuninga et al, 2020 , Oltedal et al, 2018 , Takamiya et al, 2018 ), which is also the case for the sample of this study ( Bracht et al, 2023 ). Given that structural and functional alterations of the hippocampus have been linked to the pathophysiology of depression ( Bracht et al, 2022a , Bremner et al, 2000 , Sheline et al, 2019 ), researchers assumed that hippocampal alterations may be a mechanism of ECT-treatment response ( Nordanskog et al, 2010 ).…”

“…In sum, our data suggests ECT-induced remodeling of functional and structural connectivity between the hippocampus and core midline regions of the DMN. Our results suggest that ECT induces plasticity of hippocampal networks that go beyond the frequently reported ECT-induced volumetric changes of the hippocampi ( Bracht et al, 2023 , Ousdal et al, 2020 ). Future studies should extend our findings and link measures of structural and functional connectivity of the hippocampus to specific clinical syndromes associated with the DMN (e.g.…”

“…Our study sample includes participants of previous cross-sectional ( Bracht et al, 2022a , Bracht et al, 2022b , Mertse et al, 2022 ) and longitudinal studies ( Bracht et al, 2023 ). Patients with a current depressive episode that were scheduled for an ECT-index series at the ECT-clinic of the University Hospital of Psychiatry and Psychotherapy Bern were asked if they were interested to participate.…”

“…It is possible, that more subtle changes in hippocampal subfields (e.g. the dentate gyrus) or spatially distributed networks related to anterior or posterior segments of the hippocampi may underlie treatment response ( Bracht et al, 2023 , Leaver et al, 2021 , Nuninga et al, 2020 ). Investigations of extended hippocampal networks may therefore contribute to elucidate the role of the hippocampus in ECT-treatment response.…”

Electroconvulsive therapy increases cortical thickness in depression: A systematic review

“…Gbyl et al (2019) explored CT changes in MDD from baseline to six months after the last ECT, with an intermediate scan after the first ECT. They reported an increase in CT in 26 cortical regions, mainly within the frontal, temporal, and insular cortex immediately after the first series of ECT, which returned to baseline at six months of follow-up (Gbyl et al, 2019).A recent study by Bracht et al (2023) compared longitudinal changes in CT between the ECT-treated group, treatment-as-usual (TAU) responders, and HC. Patients with unipolar and bipolar TRD were scanned twice, at the beginning and at the end of the ECT series, while patients with TAU were scanned at baseline and after achieving remission of depressive symptoms or within 12 weeks after the first MRI scan (Bracht et al, 2023).…”