Factors to consider when applying transcranial magnetic stimulation of the dorsolateral prefrontal cortex when resting motor threshold is asymmetric: A case study

Research output: Contribution to journalLetterOtherpeer-review

Abstract

Transcranial magnetic stimulation (TMS) is an increasingly popular tool in treating psychiatric conditions. The dorsal lateral prefrontal cortex (DLPFC) is typically targeted for stimulation, with magnetic field intensity being calibrated by establishing resting motor threshold (RMT) at hand region of primary motor cortex (M1 hand). This presumes that scalp-to-cortex distance (SCD) and cortical thickness is similar at both sites. We present data from a patient who had very asymmetrical RMTs (47 and 78). We investigated SCDs in this patient at the M1 hand and DLPFC, and the M1 hand cortical thickness. We also investigated TMS electric field distribution. The M1 hand SCD and cortical thickness of the M1 hand was larger on the side with higher RMT. Electric field finite element modelling demonstrated the focal point did not effectively reach the M1 hand with higher RMT as the postcentral gyrus was shunting it. Hence, successful DLPFC treatment was based upon the side with lower RMT. This study highlights the importance of tailoring DLPFC treatment intensity not only based on RMT at the M1 hand, and upon the degree to which SCD distance differs between sites, but also based upon size, shape, and density of M1 hand, as well as electric field distribution.
Original languageEnglish
Pages (from-to)130 - 135
Number of pages6
JournalBioelectromagnetics
Volume37
Issue number2
DOIs
Publication statusPublished - 2016

Keywords

  • brain stimulation
  • gyrification
  • motor cortex
  • magnetic resonance imaging

Cite this

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title = "Factors to consider when applying transcranial magnetic stimulation of the dorsolateral prefrontal cortex when resting motor threshold is asymmetric: A case study",
abstract = "Transcranial magnetic stimulation (TMS) is an increasingly popular tool in treating psychiatric conditions. The dorsal lateral prefrontal cortex (DLPFC) is typically targeted for stimulation, with magnetic field intensity being calibrated by establishing resting motor threshold (RMT) at hand region of primary motor cortex (M1 hand). This presumes that scalp-to-cortex distance (SCD) and cortical thickness is similar at both sites. We present data from a patient who had very asymmetrical RMTs (47 and 78). We investigated SCDs in this patient at the M1 hand and DLPFC, and the M1 hand cortical thickness. We also investigated TMS electric field distribution. The M1 hand SCD and cortical thickness of the M1 hand was larger on the side with higher RMT. Electric field finite element modelling demonstrated the focal point did not effectively reach the M1 hand with higher RMT as the postcentral gyrus was shunting it. Hence, successful DLPFC treatment was based upon the side with lower RMT. This study highlights the importance of tailoring DLPFC treatment intensity not only based on RMT at the M1 hand, and upon the degree to which SCD distance differs between sites, but also based upon size, shape, and density of M1 hand, as well as electric field distribution.",
keywords = "brain stimulation, gyrification, motor cortex, magnetic resonance imaging",
author = "Maller, {Jerome Joseph} and Thomson, {Richard Hilton Siddall} and McQueen, {Susan Ann} and David Elliott and Fitzgerald, {Paul Bernard}",
year = "2016",
doi = "10.1002/bem.21955",
language = "English",
volume = "37",
pages = "130 -- 135",
journal = "Bioelectromagnetics",
issn = "0197-8462",
publisher = "Wiley-Blackwell",
number = "2",

}

TY - JOUR

T1 - Factors to consider when applying transcranial magnetic stimulation of the dorsolateral prefrontal cortex when resting motor threshold is asymmetric

T2 - A case study

AU - Maller, Jerome Joseph

AU - Thomson, Richard Hilton Siddall

AU - McQueen, Susan Ann

AU - Elliott, David

AU - Fitzgerald, Paul Bernard

PY - 2016

Y1 - 2016

N2 - Transcranial magnetic stimulation (TMS) is an increasingly popular tool in treating psychiatric conditions. The dorsal lateral prefrontal cortex (DLPFC) is typically targeted for stimulation, with magnetic field intensity being calibrated by establishing resting motor threshold (RMT) at hand region of primary motor cortex (M1 hand). This presumes that scalp-to-cortex distance (SCD) and cortical thickness is similar at both sites. We present data from a patient who had very asymmetrical RMTs (47 and 78). We investigated SCDs in this patient at the M1 hand and DLPFC, and the M1 hand cortical thickness. We also investigated TMS electric field distribution. The M1 hand SCD and cortical thickness of the M1 hand was larger on the side with higher RMT. Electric field finite element modelling demonstrated the focal point did not effectively reach the M1 hand with higher RMT as the postcentral gyrus was shunting it. Hence, successful DLPFC treatment was based upon the side with lower RMT. This study highlights the importance of tailoring DLPFC treatment intensity not only based on RMT at the M1 hand, and upon the degree to which SCD distance differs between sites, but also based upon size, shape, and density of M1 hand, as well as electric field distribution.

AB - Transcranial magnetic stimulation (TMS) is an increasingly popular tool in treating psychiatric conditions. The dorsal lateral prefrontal cortex (DLPFC) is typically targeted for stimulation, with magnetic field intensity being calibrated by establishing resting motor threshold (RMT) at hand region of primary motor cortex (M1 hand). This presumes that scalp-to-cortex distance (SCD) and cortical thickness is similar at both sites. We present data from a patient who had very asymmetrical RMTs (47 and 78). We investigated SCDs in this patient at the M1 hand and DLPFC, and the M1 hand cortical thickness. We also investigated TMS electric field distribution. The M1 hand SCD and cortical thickness of the M1 hand was larger on the side with higher RMT. Electric field finite element modelling demonstrated the focal point did not effectively reach the M1 hand with higher RMT as the postcentral gyrus was shunting it. Hence, successful DLPFC treatment was based upon the side with lower RMT. This study highlights the importance of tailoring DLPFC treatment intensity not only based on RMT at the M1 hand, and upon the degree to which SCD distance differs between sites, but also based upon size, shape, and density of M1 hand, as well as electric field distribution.

KW - brain stimulation

KW - gyrification

KW - motor cortex

KW - magnetic resonance imaging

UR - https://www.ncbi.nlm.nih.gov/pubmed/26866631

U2 - 10.1002/bem.21955

DO - 10.1002/bem.21955

M3 - Letter

C2 - 26866631

VL - 37

SP - 130

EP - 135

JO - Bioelectromagnetics

JF - Bioelectromagnetics

SN - 0197-8462

IS - 2

ER -