Effect of TMS coil orientation on the spatial distribution of motor evoked potentials in an intrinsic hand muscle

Victor Hugo Souza*, Taian Martins Vieira, André Salles Cunha Peres, Marco Antonio Cavalcanti Garcia, Claudia Domingues Vargas, Oswaldo Baffa

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

5 Citations (Scopus)

Abstract

Previous reports on the relationship between coil orientation and amplitude of motor evoked potential (MEP) in transcranial magnetic stimulation (TMS) did not consider the effect of electrode arrangement. Here we explore this open issue by investigating whether TMS coil orientation affects the amplitude distribution of MEPs recorded from the abductor pollicis brevis (APB) muscle with a bi-dimensional grid of 61 electrodes. Moreover, we test whether conventional mono- and bipolar montages provide representative MEPs compared to those from the grid of electrodes. Our results show that MEPs with the greatest amplitudes were elicited for 45° and 90° coil orientations, i.e. perpendicular to the central sulcus, for all electrode montages. Stimulation with the coil oriented at 135° and 315°, i.e. parallel to the central sulcus, elicited the smallest MEP amplitudes. Additionally, changes in coil orientation did not affect the spatial distribution of MEPs over the muscle extent. It has been shown that conventional electrodes with detection volume encompassing the APB belly may detect representative MEPs for optimal coil orientations. In turn, non-optimal orientations were identified only with the grid of electrodes. High-density electromyography may therefore provide new insights into the effect of coil orientation on MEPs from the APB muscle.

Original languageEnglish
Pages (from-to)635-645
Number of pages11
JournalBiomedizinische Technik
Volume63
Issue number6
DOIs
Publication statusPublished - 1 Dec 2018
MoE publication typeA1 Journal article-refereed

Keywords

  • brain stimulation
  • conventional electrodes
  • electric field direction
  • high-density electromyography
  • muscle imaging
  • transcranial magnetic stimulation

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