TMS coil orientation and muscle activation influence lower limb intracortical excitability

Hand, Brodie J; Opie, George M.; Sidhu, Simranjit K.; Semmler, John G.

doi:10.1016/j.brainres.2020.147027

Cited by 11 publications

(12 citation statements)

References 63 publications

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“…Accordingly, SICI and SICF were demonstrated in a few studies for the leg representation before (e.g. 15 – 18 )but these findings were not directly compared to measurements in the hand representation with a few exceptions 19 , 20 . However, the study of Chen et al 20 did not include the TA muscle but other leg muscles with probably less direct corticospinal projections, and SICF was not tested.…”

Section: Discussionmentioning

confidence: 95%

“…For ADM, the starting position was approximately 5.5 cm lateral to the vertex and 0.5 cm anterior to the interaural line with the coil handle pointing backward and rotated 45° away from midline, i.e., the induced current in motor cortex was oriented from lateral-posterior to medial-anterior, an orientation that is optimal for indirect activation of corticospinal neurons 23 . For TA, the coil was initially placed over the vertex such that the induced current direction in the targeted left hemisphere was from medial to lateral, i.e., the optimal orientation for eliciting MEPs 24 and SICI 15 in the leg representation. Three consecutive stimuli were applied and the peak-to-peak amplitude of the MEP in the target muscle monitored online.…”

Section: Methodsmentioning

confidence: 99%

“…In contrast, the literature on SICI and SICF measured in leg muscles is scarce (e.g. 15 – 18 ). Furthermore, the expression of SICI and SICF in hand vs. leg muscles has not been compared in the same individuals with very few exceptions 19 , 20 .…”

Section: Introductionmentioning

confidence: 99%

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Short-interval intracortical inhibition and facilitation targeting upper and lower limb muscles

Mrachacz-Kersting¹,

Stevenson

Ziemann

2021

Sci Rep

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Transcranial magnetic stimulation (TMS) can be used to study excitability of corticospinal neurons in human motor cortex. It is currently not fully elucidated if corticospinal neurons in the hand vs. leg representation show the same or different regulation of their excitability by GABAAergic and glutamatergic interneuronal circuitry. Using a paired-pulse TMS protocol we tested short-interval intracortical inhibition (SICI) and short-interval intracortical facilitation (SICF) in 18 healthy participants. Motor evoked potentials were evoked in one hand (abductor digiti minimi) and one leg muscle (tibialis anterior), with systematic variation of the intensities of the first (S1) and second (S2) pulse between 60 and 140% resting motor threshold (RMT) in 10% steps, at two interstimulus intervals of 1.5 and 2.1 ms. For the hand and leg motor representations and for both interstimulus intervals, SICI occurred if the intensities of S1 < RMT and S2 > RMT, while SICF predominated if S1 = S2 ≤ RMT, or S1 > RMT and S2 < RMT. Findings confirm and extend previous evidence that the regulation of excitability of corticospinal neurons of the hand versus leg representation in human primary cortex through GABAAergic and glutamatergic interneuronal circuits is highly similar, and that corticospinal neurons of both representations are activated by TMS transsynaptically in largely identical ways.

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Section: Discussionmentioning

confidence: 95%

Section: Methodsmentioning

confidence: 99%

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Short-interval intracortical inhibition and facilitation targeting upper and lower limb muscles

Mrachacz-Kersting¹,

Stevenson

Ziemann

2021

Sci Rep

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“…Several clinical circumstances and nTMS examination parameters which influence the results of nTMS examinations of the upper extremity muscles have been investigated and reported 5 , 6 , 8 , 18 , 19 .…”

Section: Introductionmentioning

confidence: 99%

Assessing the feasibility of mapping the tibialis anterior muscle with navigated transcranial magnetic stimulation in neuro-oncologic patients

Eibl

Schrey

Weigel

et al. 2022

Sci Rep

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Mapping the lower extremity with navigated transcranial magnetic stimulation (nTMS) still remains challenging for the investigator. Clinical factors influencing leg mapping with nTMS have not been fully investigated yet. The aim of the study was to identify factors which influence the possibility of eliciting motor evoked potentials (MEPs) from the tibialis anterior muscle (TA). Patient records, imaging, nTMS examinations and tractography were retrospectively evaluated. 48 nTMS examinations were performed in 46 brain tumor patients. Reproducible MEPs were recorded in 20 patients (41.67%). Younger age (p = 0.044) and absence of perifocal edema (p = 0.035, Cramer’s V = 0.34, OR = 0.22, 95% CI = 0.06–0.81) facilitated mapping the TA muscle. Leg motor deficit (p = 0.49, Cramer’s V = 0.12, OR = 0.53, 95%CI = 0.12–2.36), tumor entity (p = 0.36, Cramer’s V = 0.22), tumor location (p = 0.52, Cramer’s V = 0.26) and stimulation intensity (p = 0.158) were no significant factors. The distance between the tumor and the pyramidal tract was higher (p = 0.005) in patients with successful mapping of the TA. The possibility to stimulate the leg motor area was associated with no postoperative aggravation of motor deficits in general (p = 0.005, Cramer’s V = 0.45, OR = 0.63, 95%CI = 0.46–0.85) but could not serve as a specific predictor of postoperative lower extremity function. In conclusion, successful mapping of the TA muscle for neurosurgical planning is influenced by young patient age, absence of edema and greater distance to the CST, whereas tumor entity and stimulation intensity were non-significant.

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“…As an emerging neuromodulation method, transcranial magnetic stimulation (TMS) has been proved to be an effective tool in medical research and clinical application [1,2]. During the treatment, TMS coil is usually placed near the human head, and the time-varying current applied in the coil generates a spatial electromagnetic field within the interested brain tissues to change the membrane potential of intracranial neurons [3,4].…”

Section: Introductionmentioning

confidence: 99%

Focalized Brain Transcranial Magnetic Stimulation With the Utilization of a Field Shaper and a Crescent Ferromagnetic Core

Xiao¹,

Liu²,

Luo³

et al. 2021

PIER M

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Transcranial magnetic stimulation (TMS) has been widely used in the treatment of varied physical and neuropsychiatric disorders, especially in major depression. The intracranial electromagnetic field is generated by the the time-varying current in the stimulation coil to change the potential of targeted neurons during the treatment. Since different mental disorders correspond to specific stimulation targets and broad stimulation range might raise serious side effects, stimulation focalization is very important in TMS. To achieve focalized stimulation, a novel magnetic stimulation coil with the field shaper and crescent ferromagnetic core (the FSMC coil) is proposed and optimized in this study. The Finite-Element Method (FEM) is adopted to analyze the relationships between the design parameters of the field shaper and crescent ferromagnetic core and the characteristics of the intracranial electromagnetic field. Compared to traditional single circular coil, the focalization of the intracranial electromagnetic field generated by the optimized FSMC coil can be significantly improved both from 2D and 3D levels. To verify our method, an anatomically realistic human head model with different electrical properties assigned to each tissue of the brain is employed in this paper. We also checked the maximum induced charge density on the targeted plane generated by the optimized coil to make sure that it will not cause any induced neurologic damage.

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TMS coil orientation and muscle activation influence lower limb intracortical excitability

Cited by 11 publications

References 63 publications

Short-interval intracortical inhibition and facilitation targeting upper and lower limb muscles

Short-interval intracortical inhibition and facilitation targeting upper and lower limb muscles

Assessing the feasibility of mapping the tibialis anterior muscle with navigated transcranial magnetic stimulation in neuro-oncologic patients

Focalized Brain Transcranial Magnetic Stimulation With the Utilization of a Field Shaper and a Crescent Ferromagnetic Core

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