Clinical Motor Mapping with Magnetoencephalography

2020 ◽  
pp. 211-224
Author(s):  
William Gaetz ◽  
Christos Papadelis ◽  
Tony W. Wilson
Keyword(s):  
Source Localization ◽  
Magnetic Stimulation ◽  
Functional Mapping ◽  
The Body ◽  
Current Dipole ◽  
Spatial Filters ◽  
Motor Mapping ◽  
Cortical Oscillations ◽  
Mapping Techniques ◽  
Motor Representations

This chapter examines clinical motor mapping with magnetoencephalography (MEG). Motor cortex functional mapping procedures were first conducted by neurosurgeons who famously stimulated their patient’s exposed brain during surgery and then systematically documented the responses observed from the activated muscles of the body. Numerous neuroimaging-based functional mapping techniques followed, such as functional magnetic resonance imaging (fMRI), transcranial magnetic stimulation (TMS), high-density electroencephalography (HD-EEG), and MEG, which are currently used to map the motor areas in relation to isolated volitional movements. The use of MEG for presurgical functional mapping has become a standard component of clinical MEG practice. Indeed, knowledge regarding the location of eloquent MEG motor representations is valuable for presurgical planning and can improve outcomes by limiting the production of postsurgical deficits of motor function. Meanwhile, source localization challenges using equivalent current dipole (ECD) models have given way to newer methods, such as beamformer spatial filters, which have been validated clinically using electrical stimulation. It should also be noted that it is becoming increasingly evident that motor cortical oscillations are changing consistently over the life span, and thus consideration of the patient’s age will likely aid the interpretation of results.

Surgery for a giant arteriovenous malformation without motor deterioration: preoperative transcranial magnetic stimulation in a non-cooperative patient

2014 ◽  
Vol 14 (1) ◽  
pp. 38-42 ◽  
Author(s):  
Annick Kronenburg ◽  
Tristan van Doormaal ◽  
Pieter van Eijsden ◽  
Albert van der Zwan ◽  
Frans Leijten ◽  
...  
Keyword(s):  
Decision Making ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
The Body ◽  
Motor Functions ◽  
Motor Mapping ◽  
The Past ◽  
Martin Grade ◽  
Patient’S History ◽  
Support Decision Making

Transcranial magnetic stimulation (TMS) is a noninvasive activation method that is increasingly used for motor mapping. Preoperative functional mapping in vascular surgery is not routinely performed; however, in cases of high-grade arteriovenous malformations (AVMs), it could play a role in preoperative decision making. A 16-year-old male was suffering from a giant, right-sided insular, Spetzler-Martin Grade V AVM. This patient's history included 3 hemorrhagic strokes in the past 3 years, resulting in Medical Research Council Grade 2–3 (proximal) and 2–4 (distal) paresis of the left side of the body and hydrocephalus requiring a ventriculoperitoneal shunt. Preoperative TMS showed absent contralateral innervation of the remaining left-sided motor functions. Subsequently, the AVM was completely resected without any postoperative increase of the left-sided paresis. This case shows that TMS can support decision making in AVM treatment by mapping motor functions.

scholarly journals Clinical Validation of the Champagne Algorithm for Evoked Response Source Localization in Magnetoencephalography

2021 ◽  
Author(s):  
Abhishek S. Bhutada ◽  
Chang Cai ◽  
Danielle Mizuiri ◽  
Anne Findlay ◽  
Jessie Chen ◽  
...  
Keyword(s):  
Evoked Potentials ◽  
Source Localization ◽  
Clinical Population ◽  
Evoked Responses ◽  
Localization Algorithm ◽  
Equivalent Current Dipole ◽  
Current Dipole ◽  
Tumor Patients ◽  
Equivalent Current ◽  
Sensory Evoked

AbstractMagnetoencephalography (MEG) is a robust method for non-invasive functional brain mapping of sensory cortices due to its exceptional spatial and temporal resolution. The clinical standard for MEG source localization of functional landmarks from sensory evoked responses is the equivalent current dipole (ECD) localization algorithm, known to be sensitive to initialization, noise, and manual choice of the number of dipoles. Recently many automated and robust algorithms have been developed, including the Champagne algorithm, an empirical Bayesian algorithm, with powerful abilities for MEG source reconstruction and time course estimation (Wipf et al. 2010; Owen et al. 2012). Here, we evaluate automated Champagne performance in a clinical population of tumor patients where there was minimal failure in localizing sensory evoked responses using the clinical standard, ECD localization algorithm. MEG data of auditory evoked potentials and somatosensory evoked potentials from 21 brain tumor patients were analyzed using Champagne, and these results were compared with equivalent current dipole (ECD) fit. Across both somatosensory and auditory evoked field localization, we found there was a strong agreement between Champagne and ECD localizations in all cases. Given resolution of 8mm voxel size, peak source localizations from Champagne were below 10mm of ECD peak source localization. The Champagne algorithm provides a robust and automated alternative to manual ECD fits for clinical localization of sensory evoked potentials and can contribute to improved clinical MEG data processing workflows.

scholarly journals B-PO03-139 AN EVALUATION OF FUNCTIONAL MAPPING TECHNIQUES FOR AVNRT

Heart Rhythm ◽  
2021 ◽  
Vol 18 (8) ◽  
pp. S246
Author(s):  
Christopher Purtell ◽  
Ryan Kipp ◽  
Christina Healy
Keyword(s):  
Functional Mapping ◽  
Mapping Techniques

Successful motor mapping with transcranial magnetic stimulation in an infant: A case report

Neurology ◽  
2017 ◽  
Vol 89 (20) ◽  
pp. 2115-2117 ◽  
Author(s):  
Shalini Narayana ◽  
Basanagoud Mudigoudar ◽  
Abbas Babajani-Feremi ◽  
Asim F. Choudhri ◽  
Frederick A. Boop
Keyword(s):  
Case Report ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Motor Mapping

scholarly journals Preoperative magnetic source imaging for brain tumor surgery: a quantitative comparison with intraoperative sensory and motor mapping

2003 ◽  
Vol 15 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Hagen Schiffbauer ◽  
Mitchel S. Berger ◽  
Paul Ferrari ◽  
Dirk Freudenstein ◽  
Howard A. Rowley ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Cortical Mapping ◽  
Volume Data ◽  
Current Dipole ◽  
Source Imaging ◽  
Magnetic Source Imaging ◽  
Somatosensory Stimulation ◽  
Motor Mapping ◽  
Ms Imaging ◽  
Magnetic Source

Object The aim of this study was to compare quantitatively the methods of preoperative magnetic source (MS) imaging and intraoperative electrophysiological cortical mapping (ECM) in the localization of sensorimotor cortex in patients with intraaxial brain tumors. Methods Preoperative magnetoencephalography (MEG) was performed while patients received painless tactile somatosensory stimulation of the lip, hand, and foot. The early somatosensory evoked field was modeled using a single equivalent current dipole approach to estimate the spatial source of the response. Three-dimensional magnetic resonance image volume data sets with fiducials were coregistered with the MEG recordings to form the MS image. These individualized functional brain maps were integrated into a neuronavigation system. Intraoperative mapping of somatosensory and/or motor cortex was performed and sites were compared. In two subgroups of patients we compared intraoperative somatosensory and motor stimulation sites with MS imaging–based somatosensory localizations. Mediolateral projection of the MS imaging source localizations to the cortical surface reduced systematic intermodality discrepancies. The distance between two corresponding points determined using MS imaging and ECM was 12.5 ± 1.3 mm for somatosensory–somatosensory and 19 ± 1.3 mm for somatosensory–motor comparisons. The observed 6.5 mm increase in site separation was systematically demonstrated in the anteroposterior direction, as expected from actual anatomy. In fact, intraoperative sites at which stimulation evoked the same patient response exhibited a spatial variation of 10.7 ± 0.7 mm. Conclusions Preoperative MS imaging and intraoperative ECM show a favorable degree of quantitative correlation. Thus, MS imaging can be considered a valuable and accurate planning adjunct in the treatment of patients with intraaxial brain tumors.

scholarly journals Transcranial Magnetic Stimulation Over the Human Medial Posterior Parietal Cortex Disrupts Depth Encoding During Reach Planning

2020 ◽  
Vol 31 (1) ◽  
pp. 267-280
Author(s):  
Rossella Breveglieri ◽  
Annalisa Bosco ◽  
Sara Borgomaneri ◽  
Alessia Tessari ◽  
Claudio Galletti ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Parietal Cortex ◽  
Magnetic Stimulation ◽  
Posterior Parietal Cortex ◽  
Critical Role ◽  
The Body ◽  
Visually Guided ◽  
Visually Guided Reaching ◽  
Posterior Parietal

Abstract Accumulating evidence supports the view that the medial part of the posterior parietal cortex (mPPC) is involved in the planning of reaching, but while plenty of studies investigated reaching performed toward different directions, only a few studied different depths. Here, we investigated the causal role of mPPC (putatively, human area V6A–hV6A) in encoding depth and direction of reaching. Specifically, we applied single-pulse transcranial magnetic stimulation (TMS) over the left hV6A at different time points while 15 participants were planning immediate, visually guided reaching by using different eye-hand configurations. We found that TMS delivered over hV6A 200 ms after the Go signal affected the encoding of the depth of reaching by decreasing the accuracy of movements toward targets located farther with respect to the gazed position, but only when they were also far from the body. The effectiveness of both retinotopic (farther with respect to the gaze) and spatial position (far from the body) is in agreement with the presence in the monkey V6A of neurons employing either retinotopic, spatial, or mixed reference frames during reach plan. This work provides the first causal evidence of the critical role of hV6A in the planning of visually guided reaching movements in depth.

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