Functional Neuroimaging Changes Subsequent to Electroconvulsive Therapy in Unipolar Depression

Abstract

Electroconvulsive therapy (ECT) is an effective treatment for major depressive episodes; however, the neural mechanisms underlying its therapeutic effects remain largely unknown. This review summarizes the findings of functional neuroimaging studies on the effects of the ECT treatment in patients with unipolar depression. Functional neuroimaging studies show that ECT induces changes in cerebral metabolism, blood flow, neurotransmitter activity, neuronal metabolites, and brain functional connectivity. Nevertheless, most of these studies are cross-sectional, with small sample sizes, and the findings across these studies are inconsistent and often contradictory. The levels of brain functional changes are seldom correlated with alleviation of depressive symptoms. Based on the results of current functional neuroimaging studies, one cannot draw any conclusions about the exact neural mechanisms of the antidepressant effect of ECT. Additional multicenter, large-sample, unified-protocol studies with long-term follow-up and multiple observational markers are needed to clarify and cross-validate the neural mechanisms of the antidepressant effect of ECT and to explore validated neuroimaging markers for predicting and evaluating the clinical efficacy of ECT treatment.

Reversal of cerebral glucose hypometabolism on positron emission tomography with electroconvulsive therapy in an elderly patient with a psychotic episode

“…ECT‐induced seizures spread from the initiation site to other brain regions and decrease cerebral blood flow (CBF) to the left dorsolateral frontal cortex and bilateral cingulate gyrus, which suggests that this propagation occurs through cortical‐cortical or cortico‐thalamo‐cortical networks . Although, the precise mechanisms of action are unknown, PET and single‐photon emission computed tomography studies have shown that ECT changes neurotransmitter activity, brain functional connectivity, CBF, and cerebral metabolism . PET uses positron‐emitting radiotracers such as 18 F‐2‐fluoro‐2‐deoxy‐d‐glucose, a glucose analogue, and [ 15 O]H 2 O to measure cerebral glucose metabolism (CMRglu) and CBF, respectively .…”

“…[3][4][5] Although, the precise mechanisms of action are unknown, PET and single-photon emission computed tomography studies have shown that ECT changes neurotransmitter activity, brain functional connectivity, CBF, and cerebral metabolism. 6,7 PET uses positronemitting radiotracers such as 18 F-2-fluoro-2-deoxy-dglucose, a glucose analogue, and [ 15 O]H2O to measure cerebral glucose metabolism (CMRglu) and CBF, respectively. 8,9 Changes in CMRglu and CBF after a course of ECT have been inconsistent between studies, primarily due to methodological limitations and the heterogeneity of disorders.…”

Effect of electroconvulsive therapy on hippocampal and amygdala volumes: systematic review and meta-analysis

“…13 Therefore, it is necessary to conduct systematic review and meta-analysis for ECT-related effects on brain structures. Currently there are several narrative or systematic reviews of neuroimaging studies related to ECT, [13][14][15][16] but only one metaanalysis has been published so far, that by Wilkinson et al who reported that ECT increased bilateral hippocampal volume. 17 Unfortunately, they did not include the largest study currently available, 18 and focused only on hippocampal volume.…”

On electroconvulsive therapy in depression : Clinical, cognitive and neurobiological aspects

“…In studies of changes in blood flow after ECT, findings are, however, even more divergent and inconsistent (Zhuo and Yu 2014). There are several suggested explanations for this, besides the impact of timing of post-ECT scanning discussed above.…”