P079 Electroconvulsive therapy induced hippocampal electric field strength and structural plasticity

Abstract

Introduction Recent neuroimaging investigations of electroconvulsive therapy (ECT) in patients with severe treatment-resistant depression suggest that ECT-induced neuroplasticity of the hippocampus is related to improved clinical response. The relationship between stimulus dose, particularly the pulse current amplitude, with structural plasticity of the hippocampus induced by ECT remains unknown. Objectives To assess the relationship between ECT induced electric field strength and volumetric changes in the hippocampus. Patients & methods The study was approved by the Human Research Protections Office at the University of New Mexico. Fifteen depressed patients (age 55–78) were referred for ECT. Ultrabrief pulse right unilateral ECT was performed using a Thymatron System IV (n = 10, pulse amplitude = 900 mA, pulse width = 0.25 ms; Somatics LLC, Lake Bluff, IL) or a MECTA Spectrum 5000Q (pulse amplitude = 700 mA (n = 2) and 500 mA (n = 3), pulse width = 0.3 ms; MECTA Corp., Tualatin, OR) both delivering stimulation at six-times seizure threshold. The patients underwent neuroimaging within 2 days of starting ECT, and >5 days after the ECT treatment course. High resolution T1-weighted structural MRI were collected on a 3T Siemens Trio scanner. Baseline MRIs were segmented into white matter, gray matter, cerebrospinal fluid, skull, scalp using SPM 12. The volumes defining the head tissues and the attached electrodes were meshed into finite elements using the Simpleware ScanIP and ScanCAD modules. Tissue electrical conductivity and permittivity values were derived from the literature. The electric field was computed using COMSOL Multiphysics. Hippocampus segmentation and volume changes were computed using FreeSurfer. Results In a generalized linear model, ECT pulse amplitude is correlated with the induced electric field strength in the right hippocampus (p Fig. 1 shows the scatterplot of volume change with mean electric field strength and unadjusted regression lines for the left and right hippocampus. Conclusion ECT elicited structural plasticity is a function of stimulus strength. Computational electric field models can be helpful in guiding stimulus dosing in ECT. Download : Download high-res image (143KB) Download : Download full-size image