Motor field sensitivity for preoperative localization of motor cortex

Object In this study the role of magnetic source imaging for preoperative motor mapping was evaluated by using a single-dipole localization method to analyze motor field data in 41 patients. Methods Data from affected and unaffected hemispheres were collected in patients performing voluntary finger flexion movements. Somatosensory evoked field (SSEF) data were also obtained using tactile stimulation. Dipole localization using motor field (MF) data was successful in only 49% of patients, whereas localization with movement-evoked field (MEF) data was successful in 66% of patients. When the spatial distribution of MF and MEF dipoles in relation to SSEF dipoles was analyzed, the motor dipoles were not spatially distinct from somatosensory dipoles. Conclusions The findings in this study suggest that single-dipole localization for the analysis of motor data is not sufficiently sensitive and is nonspecific, and thus not clinically useful.

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

Neurosurgical FOCUS ◽

10.3171/foc.2003.15.1.7 ◽

2003 ◽

Vol 15 (1) ◽

pp. 1-10 ◽

Cited By ~ 26

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.

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Evidence for the Role of Magnetic Source Imaging in the Presurgical Evaluation of Refractory Epilepsy Patients

Frontiers in Neurology ◽

10.3389/fneur.2019.00933 ◽

2019 ◽

Vol 10 ◽

Cited By ~ 1

Author(s):

Evelien Carrette ◽

Hermann Stefan

Keyword(s):

Refractory Epilepsy ◽

Presurgical Evaluation ◽

Source Imaging ◽

Magnetic Source Imaging ◽

Magnetic Source

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Accuracy of diffusion tensor magnetic resonance imaging tractography assessed using intraoperative subcortical stimulation mapping and magnetic source imaging

Journal of Neurosurgery ◽

10.3171/jns-07/09/0488 ◽

2007 ◽

Vol 107 (3) ◽

pp. 488-494 ◽

Cited By ~ 158

Author(s):

Jeffrey I. Berman ◽

Mitchel S. Berger ◽

Sungwon Chung ◽

Srikantan S. Nagarajan ◽

Roland G. Henry

Keyword(s):

White Matter ◽

Magnetic Resonance ◽

Diffusion Tensor ◽

Fiber Tracking ◽

Bipolar Electrode ◽

Source Imaging ◽

Magnetic Source Imaging ◽

Motor Pathway ◽

Magnetic Source ◽

Subcortical Stimulation

Object Resecting brain tumors involves the risk of damaging the descending motor pathway. Diffusion tensor (DT)–imaged fiber tracking is a noninvasive magnetic resonance (MR) technique that can delineate the subcortical course of the motor pathway. The goal of this study was to use intraoperative subcortical stimulation mapping of the motor tract and magnetic source imaging to validate the utility of DT-imaged fiber tracking as a tool for presurgical planning. Methods Diffusion tensor-imaged fiber tracks of the motor tract were generated preoperatively in nine patients with gliomas. A mask of the resultant fiber tracks was overlaid on high-resolution T1- and T2-weighted anatomical MR images and used for stereotactic surgical navigation. Magnetic source imaging was performed in seven of the patients to identify functional somatosensory cortices. During resection, subcortical stimulation mapping of the motor pathway was performed within the white matter using a bipolar electrode. Results A total of 16 subcortical motor stimulations were stereotactically identified in nine patients. The mean distance between the stimulation sites and the DT-imaged fiber tracks was 8.7 ±3.1 mm (±standard deviation). The measured distance between subcortical stimulation sites and DT-imaged fiber tracks combines tracking technique errors and all errors encountered with stereotactic navigation. Conclusions Fiber tracks delineated using DT imaging can be used to identify the motor tract in deep white matter and define a safety margin around the tract.

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“Magnetic source imaging in presurgical evaluation of paediatric focal drug-resistant epilepsy and its predictive value of surgical outcome in lesional cases: A single-centre experience from South India”.

Seizure ◽

10.1016/j.seizure.2021.05.015 ◽

2021 ◽

Author(s):

Bhargava Gautham ◽

Asheeb Ahmed ◽

Ravindranadh Chowdary Mundlamuri ◽

Mariyappa Narayanan ◽

Velmurugan Jayabal ◽

...

Keyword(s):

Predictive Value ◽

Surgical Outcome ◽

South India ◽

Drug Resistant ◽

Presurgical Evaluation ◽

Single Centre ◽

Source Imaging ◽

Magnetic Source Imaging ◽

Single Centre Experience ◽

Drug Resistant Epilepsy

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Magnetic source imaging for the surgical evaluation of electroencephalography-confirmed secondary bilateral synchrony in intractable epilepsy

Journal of Neurosurgery ◽

10.3171/2009.6.jns081376 ◽

2009 ◽

Vol 111 (6) ◽

pp. 1248-1256 ◽

Cited By ~ 26

Author(s):

Edward F. Chang ◽

Srikantan S. Nagarajan ◽

Mary Mantle ◽

Nicholas M. Barbaro ◽

Heidi E. Kirsch

Keyword(s):

Mr Imaging ◽

Intractable Epilepsy ◽

Focal Lesion ◽

Seizure Type ◽

Source Imaging ◽

Magnetic Source Imaging ◽

Ms Imaging ◽

Epileptiform Discharges ◽

Magnetic Source ◽

Imaging Results

Object Routine scalp electroencephalography (EEG) cannot always distinguish whether generalized epileptiform discharges are the result of primary bilateral synchrony or secondary bilateral synchrony (SBS) from a focal origin; this is an important distinction because the latter may be amenable to resection. Whole-head magnetoencephalography (MEG) has superior spatial resolution compared with traditional EEG, and can potentially elucidate seizure foci in challenging epilepsy cases in which patients are undergoing evaluation for surgery. Methods Sixteen patients with medically intractable epilepsy in whom SBS was suspected were referred for magnetic source (MS) imaging. All patients had bilateral, synchronous, widespread, and most often generalized spike-wave discharges on scalp EEG studies, plus some other clinical (for example, seizure semiology) or MR imaging feature (for example, focal lesion) suggesting focal onset and hence possible surgical candidacy. The MS imaging modality is the combination of whole-head MEG and parametric reconstruction of corresponding electrical brain sources. An MEG and simultaneous EEG studies were recorded with a 275-channel whole-head system. Single-equivalent current dipoles were estimated from the MEG data, and dipole locations and orientations were superimposed on patients' MR images. Results The MS imaging studies revealed focal dipole clusters in 12 (75%) of the 16 patients, of which a single dipole cluster was identified in 7 patients (44%). Patient age, seizure type, duration of disease, video-EEG telemetry, and MR imaging results were analyzed to determine factors predictive of having clusters revealed on MS imaging. Of these factors, only focal MR imaging anatomical abnormalities were associated with dipole clusters (chi-square test, p = 0.03). Selective resections (including the dipole cluster) in 7 (87%) of 8 patients resulted in seizure-free or rare seizure outcomes (Engel Classes I and II). Conclusions Magnetic source imaging may provide noninvasive anatomical and neurophysiological confirmation of localization in patients in whom there is a suspicion of SBS (based on clinical or MR imaging data), especially in those with an anatomical lesion. Identification of a focal seizure origin has significant implications for both resective and nonresective treatment of intractable epilepsy.

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