Cervicothoracic trans-spinal magnetic stimulation: effect of coil position and orientation on spinal motor evoked potentials

Lei Zhu; Sophia G. Nopoulos; Kesten M. Anderson; Richard K. Shields; Stacey L. DeJong

doi:10.1007/s00221-026-07390-y

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Cervicothoracic trans-spinal magnetic stimulation: effect of coil position and orientation on spinal motor evoked potentials

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Cervicothoracic trans-spinal magnetic stimulation: effect of coil position and orientation on spinal motor evoked potentials

Lei Zhu, Sophia G. Nopoulos, Kesten M. Anderson, Richard K. Shields and Stacey L. DeJong

Experimental brain research, Vol.244(10), 189

08/31/2026

DOI: 10.1007/s00221-026-07390-y

PMCID: PMC13529895

PMID: 42671606

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Abstract

Stroke is a leading cause of long-term adult disability, and over 80% of survivors have persistent upper limb motor impairment. Spinal electrical stimulation has shown therapeutic potential after neurological disorders. Post-stroke applications have largely relied on invasive implants that limit clinical adoption, and non-invasive high intensity electrical stimulation may be intolerable for those with residual sensory function. Trans-spinal magnetic stimulation offers a non-invasive alternative capable of modulating residual sensorimotor pathways. Fundamental parameters, such as coil position and orientation, remain under-investigated. Two experiments were conducted to fill this gap. Experiment 1: 19 healthy adults underwent spinal mapping involving 30 cervicothoracic sites (3×10 grid). Responses were recorded from 6 upper limb muscles bilaterally at suprathreshold intensity using a rostral-left induced current direction. Friedman ANOVAs revealed significant medial–lateral and rostral–caudal variation in amplitude of spinal motor evoked potentials (sMEPs): ipsilateral>midline>contralateral, with arm responses peaking rostrally, wrist at mid-rows, and hand caudally. Experiment 2: 20 healthy adults received stimulation at three horizontal cervicothoracic sites using eight current directions spaced 45° apart. Friedman ANOVAs indicated a bilateral mirror-symmetrical pattern. The largest responses from left-sided muscles were elicited with a rostral-left current direction achieved by rotating the coil handle 45° counterclockwise from the caudal direction. Likewise, the largest right-sided muscle responses were elicited with a rostral-right current direction achieved by rotating the coil handle 315° counterclockwise. Coil position and orientation are critical determinants of sMEP amplitude. These results provide a foundational framework to further investigate cervicothoracic magnetic stimulation as a potential non-invasive neuromodulatory intervention.

Spinal stimulation

Magnetic stimulation

Induced current direction

Motor evoked potentials

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Details

Title: Subtitle: Cervicothoracic trans-spinal magnetic stimulation: effect of coil position and orientation on spinal motor evoked potentials
Creators: Lei Zhu - University of Iowa
Sophia G. Nopoulos - University of Iowa
Kesten M. Anderson - University of Iowa
Richard K. Shields - University of Iowa
Stacey L. DeJong - University of Iowa
Resource Type: Journal article
Publication Details: Experimental brain research, Vol.244(10), 189
DOI: 10.1007/s00221-026-07390-y
PMID: 42671606
PMCID: PMC13529895
NLM abbreviation: Exp Brain Res
ISSN: 0014-4819
eISSN: 1432-1106
Publisher: Springer Nature
Grant note: StrokeNet Pilot project grant from the Institute for Clinical and Translational Science / Roy J. and Lucille A. Carver College of Medicine, University of Iowa (https://doi.org/10.13039/100015515)
Language: English
Date published: 08/31/2026
Academic Unit: Orthopedics and Rehabilitation; Physical Therapy and Rehabilitation Science; Internal Medicine
Record Identifier: 9985222740202771

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