Systematic Review of the Neural Effect of Electroconvulsive Therapy in Patients with Schizophrenia: Hippocampus and Insula as the Key Regions of Modulation

Abstract

Objective Electroconvulsive therapy (ECT) has been the most potent treatment option for treatment-resistant schizophrenia (TRS). However, the underlying neural mechanisms of ECT in schizophrenia remain largely unclear. This paper examines studies that investigated structural and functional changes after ECT in patients with schizophrenia. Methods We carried out a systematic review with following terms: ‘ECT’, ‘schizophrenia’, and the terms of various neuroimaging modalities. Results Among the 325 records available from the initial search in May 2020, 17 studies were included. Cerebral blood flow in the frontal, temporal, and striatal structures was shown to be modulated (n=3), although the results were divergent. Magnetic resonance spectroscopy (MRS) studies suggested that the ratio of N-acetyl-aspartate/creatinine was increased in the left prefrontal cortex (PFC; n=2) and left thalamus (n=1). The hippocampus and insula (n=6, respectively) were the most common regions of structural/functional modulation, which also showed symptom associations. Functional connectivity of the default mode network (DMN; n=5), PFC (n=4), and thalamostriatal system (n=2) were also commonly modulated. Conclusion Despite proven effectiveness, there has been a dearth of studies investigating the neurobiological mechanisms underlying ECT. There is preliminary evidence of structural and functional modulation of the hippocampus and insula, functional changes in the DMN, PFC, and thalamostriatal system after ECT in patients with schizophrenia. We discuss the rationale and implications of these findings and the potential mechanism of action of ECT. More studies evaluating the mechanisms of ECT are needed, which could provide a unique window into what leads to treatment response in the otherwise refractory TRS population.

Effects of electroconvulsive therapy on functional brain networks in patients with schizophrenia

“…Previous studies have also pointed out that patients with SZ exhibit decreased nodal local efficiency in the superior frontal gyrus [ 36 ]. It is known that ECT can cause some cognitive side effects [ 40 ]. This may explain the difference in nodal local efficiency of the superior frontal gyrus between SZ patients and healthy controls even after ECT.…”

Sex differences in factors influencing hospital-acquired pneumonia in schizophrenia patients receiving modified electroconvulsive therapy

“…ECT treatment improves the structure and function of the hippocampus and insula in SCZ patients and regulates the function of the prefrontal and thalamic striatum of the default network ( 40 , 41 ). Animal experiments have also shown that ECT attenuates microglia and astrocyte proliferation, thus improving schizophrenic behavior ( 42 ).…”

Driving brain state transitions in major depressive disorder through external stimulation

“…Numerous evidence has shown that structural and functional abnormalities in the insula are widely observed in patients with MDD. Meanwhile, an increasing number of MRI studies have also found that structural and functional abnormalities in the insula can be normalized after optimizing treatments, including modified electroconvulsive therapy (mECT) (Dichter et al, 2015 ; Moon et al, 2021 ; Wang, Wei, et al, 2020 ), transcranial magnetic stimulation (Fu et al, 2021 ), transcranial direct current stimulation (Sagliano et al, 2019 ; Sankarasubramanian et al, 2017 ). For example, a recent study found that pretreatment decreased FC with the insula and normalization of this area's function after mECT (Wang, Wei, et al, 2020 ).…”