The Relationship Between Cortical Inhibition and Electroconvulsive Therapy in the Treatment of Major Depressive Disorder

Abstract

Dysfunctional cortical inhibition (CI) is postulated as a key neurophysiological mechanism in major depressive disorder. Electroconvulsive therapy (ECT) is the treatment of choice for resistant depression and ECT has been associated with enhanced CI. The objective of this study was to evaluate the relationship between CI and ECT response in resistant depression. Twenty-five patients with treatment resistant depression underwent an acute course of ECT. CI was indexed by the cortical silent period (CSP) and short-interval cortical inhibition (SICI), through TMS-EMG. CI and clinical response was measured prior to beginning an acute ECT course and within 48 hours of the last ECT treatment in the course. Clinical response to ECT was assessed by HDRS-17 before and after an acute course of ECT. We found that there was a significant difference in CSP at baseline between responder and non-responder groups (p = 0.044). Baseline CSP predicted therapeutic response to ECT with sensitivity of 80% and specificity of 60%. There were no changes in CSP or SICI after administration of the ECT course. Our findings suggest that duration of pre-treatment CSP may be a useful predictor of therapeutic response to ECT in patients with TRD.

Modulation of functional network properties in major depressive disorder following electroconvulsive therapy (ECT): a resting-state EEG analysis

“…The study methods were carried out in accordance with the ethics committee regulations of CAMH. A comprehensive list of inclusion/exclusion criteria is provided in Voineskos et al 37 .…”

“…The primary measure of clinical response was the 17-item Hamilton Depression Rating Scale (HDRS-17) which was completed at baseline and within 48 h following the ECT treatment course. Treatment response was defined as ≥ 50% reduction in HDRS-17 score following treatment 37 .…”

“…Anaesthesia was achieved using methohexital for sedation and succinylcholine for muscle relaxation. Cessation of the ECT course was based on patient response, clinical factors, the patient's desire to discontinue treatment, or the most responsible physician's clinical judgement 37 . A detailed overview of the ECT administration procedure is provided in Voineskos et al 37 .…”

Neural excitation/inhibition imbalance and the treatment of severe depression

“…Similar to pharmacotherapy, the effectiveness of ECT may also depend on mechanisms that are closely related to the neural excitation/inhibition balance 16 . ECT uses a brief electrical stimulus to the cranium in order to elicit seizure activity which propagates throughout the brain 17 .…”

Efficacy, tolerability, and cognitive effects of deep transcranial magnetic stimulation for late-life depression: a prospective randomized controlled trial

“…There is both neurophysiological and clinical evidence to suggest that increasing the number of daily pulses may increase response rates. First, neurophysiological data suggest that a single session of 6000 pulses of rTMS delivered at 20 Hz increases cortical inhibition-a marker of treatment response for brain stimulation treatments [29,30]-compared to 1200 or 3600 pulses [31). Second, clinical trials using accelerated rTMS treatment protocols that delivered 15 sessions of 1000 pulses of rTMS over 2 days resulted in rapid treatment response [32].…”