Dataset Information

Neurophysics Assessment of the Muscle Bioenergy Generated by Transcranial Magnetic Stimulation.

ABSTRACT: The content of the rectified motor evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) has ambiguously been assessed without the precision that energy calculation deserves. This fact has misled data interpretation and misguided biomedical interventions. To definitively fill the gap that exits in the neurophysics processing of these signals, we computed, in Walls ( W^ ), the bioenergy within the rectified MEP recorded from the human first digitorum index (FDI) muscle at rest and under isometric contraction. We also gauged the biowork exerted by this muscle. Here we show that bioenergy and biowork can accurately and successfully be assessed, validated, and determined in W^ from MEP signals induced by TMS, regardless of knowing the mathematical expression of the function of the signal. Our novel neurophysics approach represents a dramatic paradigm shift in analysis and interpretation of the content of the MEP and will give a true meaning to the content of rectified signals. Importantly, this innovative approach allowed unveiling that women exerted more bioenergy than men at the magnetic stimulations used in this study. Revisitation of conclusions drawn from studies published elsewhere assessing rectified EMG signals that have used ambiguous units is strongly recommended.

SUBMITTER: Leon-Sarmiento FE

PROVIDER: S-EPMC6750091 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Neurophysics Assessment of the Muscle Bioenergy Generated by Transcranial Magnetic Stimulation.

Leon-Sarmiento Fidias E FE Gonzalez-Castaño Alexander A Rizzo-Sierra Carlos V CV Aceros Juan J Leon-Ariza Daniel S DS Leon-Ariza Juan S JS Prada Diddier G DG Bara-Jimenez William W Wang Zeng Y ZY

Research (Washington, D.C.) 20190326

The content of the rectified motor evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) has ambiguously been assessed without the precision that energy calculation deserves. This fact has misled data interpretation and misguided biomedical interventions. To definitively fill the gap that exits in the neurophysics processing of these signals, we computed, in Walls ( W ^ ), the bioenergy within the rectified MEP recorded from the human first digitorum ...[more]

PMID: 31549082

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Project description:PurposeThis study aims to perform a classification and rigorous numerical evaluation of the risks of occupational exposure in the health environment related to the administration of transcranial magnetic stimulation (TMS) treatment. The study investigates the numerically estimated induced electric field that occurs in the human tissues of an operator caused by exposure to the variable magnetic field produced by TMS during treatments. This could be a useful starting point for future risk assessment studies and safety indications in this context.MethodsWe performed a review of the actual positions assumed by clinicians during TMS treatments. Three different TMS coils (two circular and one figure-of-eight) were modeled and characterized numerically. Different orientations and positions of each coil with respect to the body of the operator were investigated to evaluate the induced electric (-E) field in the body tissues. The collected data were processed to allow comparison with the safety standards for occupational exposure, as suggested by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) 2010 guidelines.ResultsUnder the investigated conditions, exposure to TMS shows some criticalities for the operator performing the treatment. Depending on the model of the TMS coil and its relative position with respect to the operator's body, the numerically estimated E-field could exceed the limits suggested by the ICNIRP 2010 guidelines. We established that the worst-case scenario for the three coils occurs when they are placed in correspondence of the abdomen, with the handle oriented parallel to the body (II orientation). Working at a maximum TMS stimulator output (MSO), the induced E-field is up to 7.32 V/m (circular coil) and up to 1.34 V/m (figure-of-eight coil). The induced E-field can be modulated by the TMS percentage of MSO (%MSO) and by the distance between the source and the operator. At %MSO equal to or below 80%, the figure-of-eight coil was compliant with the ICNIRP limit (1.13 V/m). Conversely, the circular coil causes an induced E-field above the limits, even when powered at a %MSO of 30%. Thus, in the investigated worst-case conditions, an operator working with a circular coil should keep a distance from its edge to be compliant with the guidelines limit, which depends on the selected %MSO: 38 cm at 100%, 32 cm at 80%, 26.8 cm at 50%, and 19.8 cm at 30%. Furthermore, attention should be paid to the induced E-field reached in the operator's hand as the operator typically holds the coil by hand. In fact in the hand, we estimated an induced E-field up to 10 times higher than the limits.ConclusionsOur numerical results indicate that coil positions, orientations, and distances with respect to the operator's body can determine the levels of induced E-field that exceed the ICNIRP limits. The induced E-field is also modulated by the choice of %MSO, which is related to the TMS application. Even under the best exposure conditions, attention should be paid to the exposure of the hand. These findings highlight the need for future risk assessment studies to provide more safety information for the correct and safe use of TMS devices.

Dataset Information

Neurophysics Assessment of the Muscle Bioenergy Generated by Transcranial Magnetic Stimulation.

Publications

Neurophysics Assessment of the Muscle Bioenergy Generated by Transcranial Magnetic Stimulation.

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