Minimum Electric Field Exposure for Seizure Induction with Electroconvulsive Therapy and Magnetic Seizure Therapy

Abstract

Lowering and individualizing the current amplitude in electroconvulsive therapy (ECT) has been proposed as a means to produce stimulation closer to the neural activation threshold and more focal seizure induction, which could potentially reduce cognitive side effects. However, the effect of current amplitude on the electric field (E-field) in the brain has not been previously linked to the current amplitude threshold for seizure induction. We coupled MRI-based E-field models with amplitude titrations of motor threshold (MT) and seizure threshold (ST) in four nonhuman primates (NHPs) to determine the strength, distribution, and focality of stimulation in the brain for four ECT electrode configurations (bilateral, bifrontal, right-unilateral, and frontomedial) and magnetic seizure therapy (MST) with cap coil on vertex. At the amplitude-titrated ST, the stimulated brain subvolume (23-63%) was significantly less than for conventional ECT with high, fixed current (94-99%). The focality of amplitude-titrated right-unilateral ECT (25%) was comparable to cap coil MST (23%), demonstrating that ECT with a low current amplitude and focal electrode placement can induce seizures with E-field as focal as MST, although these electrode and coil configurations affect differently specific brain regions. Individualizing the current amplitude reduced interindividual variation in the stimulation focality by 40-53% for ECT and 26% for MST, supporting amplitude individualization as a means of dosing especially for ECT. There was an overall significant correlation between the measured amplitude-titrated ST and the prediction of the E-field models, supporting a potential role of these models in dosing of ECT and MST. These findings may guide the development of seizure therapy dosing paradigms with improved risk/benefit ratio.

A Computational Assessment of Target Engagement in the Treatment of Auditory Hallucinations with Transcranial Direct Current Stimulation

“…For each montage, the complete 3D head models incorporating the tDCS electrodes were adaptively tessellated to produce finite element models using the restricted Delaunay triangulation algorithm ( 32 ). The electric conductivities used for each tissue type across all five head models were as follows: gray matter = 0.33 S/m, white matter = 0.14 S/m, CSF = 1.79 S/m, skin = 0.43 S/m, skull = 0.0132 S/m, and air = 0 S/m ( 21 , 23 , 27 , 33 , 34 ). The electrodes were assumed to have the conductivity of saline (1.4 S/m) ( 22 ).…”

“…We computed the electric field magnitude ( E ) and the percentage modulated volume for each AVH-ROI. The modulated brain volume was defined as the percentage of the brain volume (within the left or right AVH networks) exposed to electric field magnitude ( E ) stronger than the modulation threshold ( E th ), i.e., the volume where E / E th ≥ 1 ( 21 , 34 ). We acknowledge that the modulation threshold in living humans is yet to be conclusively determined.…”

Shorter recovery times and better cognitive function—A comparative pilot study of magnetic seizure therapy and electroconvulsive therapy in patients with depressive episodes

“…Since there was no significant difference in antidepressant efficacy between MST and ECT, the improvements in cognitive function were less likely due to the improvement of depressive symptoms. The differences in the effect of cognitive function between MST and ECT may be related to their different mechanisms on brain function (Lee et al., 2017).…”

Innate Immune Regulation Under Magnetic Fields With Possible Mechanisms and Therapeutic Applications

“…Some researchers have also tried magnetic-assisted treatment for liver fibrosis and rheumatoid arthritis (14,36,38,76). Magnetic seizure therapy (MST) is the use of transcranial magnetic stimulation to induce seizures for the treatment of neurological disorders (77)(78)(79)(80)(81)(82). Moreover, magnetic-assisted treatment for inflammatory diseases varies depending on the MF dosing parameters.…”