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Spooner RK, Madhavan D, Aizenberg MR, Wilson TW. Retrospective comparison of motor and somatosensory MEG mapping-Considerations for better clinical applications. Neuroimage Clin 2022; 35:103045. [PMID: 35597033 PMCID: PMC9123261 DOI: 10.1016/j.nicl.2022.103045] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 04/29/2022] [Accepted: 05/09/2022] [Indexed: 11/17/2022]
Abstract
MEG is a clinically validated tool for presurgical functional mapping. The success rate for MEG somatosensory and motor mapping is not fully known. Comprehensive mapping protocols increase the accuracy of sensorimotor mapping. Major sources of mapping failures include low SNR, magnetic artifacts, and motion. Recommendations for improving mapping success rates in the future are discussed.
While magnetoencephalography (MEG) has proven to be a valuable and reliable tool for presurgical functional mapping of eloquent cortices for at least two decades, widespread use of this technique by clinicians has remained elusive. This modest application may be attributable, at least in part, to misunderstandings regarding the success rate of such mapping procedures, as well as the primary sources contributing to mapping failures. To address this, we conducted a retrospective comparison of sensorimotor functional mapping success rates in 141 patients with epilepsy and 75 tumor patients from the Center for MEG in Omaha, NE. Neurosurgical candidates either completed motor mapping (i.e., finger tapping paradigm), somatosensory mapping (i.e., peripheral stimulation paradigm), or both motor and somatosensory protocols during MEG. All MEG data underwent subsequent time-domain averaging and source localization of left and right primary motor (M1) and somatosensory (S1) cortices was conducted using a single equivalent dipole model. Successful mapping was determined based on dipole goodness of fit metrics ∼ 95%, as well as an accurate and conceivable spatial correspondence to precentral and postcentral gyri for M1 and S1, respectively. Our results suggest that mapping M1 in epilepsy and tumor patients was on average 94.5% successful, when patients only completed motor mapping protocols. In contrast, mapping S1 was successful 45–100% of the time in these patient groups when they only completed somatosensory mapping paradigms. Importantly, Z-tests for independent proportions revealed that the percentage of successful S1 mappings significantly increased to ∼ 94% in epilepsy patients who completed both motor/somatosensory mapping protocols during MEG. Together, these data suggest that ordering more comprehensive mapping procedures (e.g., both motor and somatosensory protocols for a collective sensorimotor network) may substantially increase the accuracy of presurgical functional mapping by providing more extensive data from which to base interpretations. Moreover, clinicians and magnetoencephalographers should be considerate of the major contributors to mapping failures (i.e., low SNR, excessive motion and magnetic artifacts) in order to further increase the percentage of cases achieving successful mapping of eloquent cortices.
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Affiliation(s)
- Rachel K Spooner
- Institute for Human Neuroscience, Boys Town National Research Hospital, Omaha, NE, USA; College of Medicine, University of Nebraska Medical Center, Omaha, NE, USA; Institute of Clinical Neuroscience and Medical Psychology, Heinrich-Heine University, Düsseldorf, Germany.
| | - Deepak Madhavan
- Institute for Human Neuroscience, Boys Town National Research Hospital, Omaha, NE, USA
| | | | - Tony W Wilson
- Institute for Human Neuroscience, Boys Town National Research Hospital, Omaha, NE, USA; College of Medicine, University of Nebraska Medical Center, Omaha, NE, USA; Department of Pharmacology & Neuroscience, Creighton University, Omaha, NE, USA
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Nagarajan S, Kirsch H, Lin P, Findlay A, Honma S, Berger MS. Preoperative localization of hand motor cortex by adaptive spatial filtering of magnetoencephalography data. J Neurosurg 2008; 109:228-37. [PMID: 18671634 DOI: 10.3171/jns/2008/109/8/0228] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
The goal of this study was to examine the sensitivity and specificity in preoperative localization of hand motor cortex by imaging regional event-related desynchronization (ERD) of brainwaves in the β frequency band (15–25 Hz) involved in self-paced movement.
Methods
Using magnetoencephalography (MEG), the authors measured ERD that occurred before self-paced unilateral index finger flexion in 66 patients with brain tumors, epilepsy, and arteriovenous malformations.
Results
The authors applied an adaptive spatial filtering algorithm to MEG data and found that peaks of the tomographic distribution of β-band ERD sources reliably localized hand motor cortex compared with electrical cortical stimulation. They also observed high specificity in estimating contralateral hand motor cortical representations relative to somatosensory cortex. Neither presence nor location of tumor changed the qualitative or quantitative location of motor cortex relative to somatosensory cortex.
Conclusions
An imaging protocol using ERD obtained by adaptive spatial filtering of MEG data can be used for extremely reliable preoperative localization of hand motor cortex.
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Affiliation(s)
| | | | - Peter Lin
- 1Biomagnetic Imaging Laboratory, Department of Radiology, and
- 3Department of Neurology, Stanford University School of Medicine, Stanford, California
| | - Anne Findlay
- 1Biomagnetic Imaging Laboratory, Department of Radiology, and
| | - Susanne Honma
- 1Biomagnetic Imaging Laboratory, Department of Radiology, and
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Abstract
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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Affiliation(s)
- Peter T Lin
- Department of Neurology, Stanford Hospital and Clinics, Stanford, California, USA
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Billingsley RL, Simos PG, Castillo EM, Sarkari S, Breier JI, Pataraia E, Papanicolaou AC. Spatio-temporal cortical dynamics of phonemic and semantic fluency. J Clin Exp Neuropsychol 2005; 26:1031-43. [PMID: 15590459 DOI: 10.1080/13803390490515333] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Hemodynamic brain imaging and lesion studies have suggested differential involvement of expressive language-related cortical regions based on the phonemic versus semantic characteristics of verbal cues. The aims of this study were: 1) to elucidate the relative timing of the activity of inferior frontal and anterior insular versus motor and supplementary motor cortex during a fluency task and 2) to assess potential differences in the location or timing of activity in anterior and posterior language areas based on letter versus category cues. Using magnetic source imaging (MSI), we found significantly earlier onset latencies and a greater number of activity sources in motor and supplementary motor compared with inferior frontal and anterior insular regions. We also observed greater left versus right hemispheric asymmetry of activation for letter compared with category cues. This study provides new insights into cortico-cortical interactions during expressive language tasks.
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Affiliation(s)
- R L Billingsley
- Vivian L. Smith Center for Neurologic Research, Department of Neurosurgery and Division of Clinical Neurosciences, University of Texas-Houston Medical School, Houston, TX 77030, USA.
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Papanicolaou AC, Castillo EM, Billingsley-Marshall R, Pataraia E, Simos PG. A Review of Clinical Applications of Magnetoencephalography. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2005; 68:223-47. [PMID: 16443016 DOI: 10.1016/s0074-7742(05)68009-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
Affiliation(s)
- Andrew C Papanicolaou
- Department of Neurosurgery, Vivian L. Smith Center for Neurologic Research, University of Texas - Health Science Center at Houston, Houston, Texas 77030, USA
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Ishibashi H, Simos PG, Wheless JW, Baumgartner JE, Kim HL, Castillo EM, Davis RN, Papanicolaou AC. Localization of ictal and interictal bursting epileptogenic activity in focal cortical dysplasia: agreement of magnetoencephalography and electrocorticography. Neurol Res 2002; 24:525-30. [PMID: 12238616 DOI: 10.1179/016164102101200483] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Focal cortical dysplasia (FCD) is often associated with severe partial epilepsy. In such cases, interictal frequent rhythmic bursting epileptiform activity (FBREA) on both scalp electroencephalography (EEG) and electrocorticography (ECoG) is generally accepted to be identical to the ictal epileptiform activity. We used magnetoencephalography (or Magnetic Source Imaging (MSI)) to determine the epileptogenic zone in a 6-year-old patient with histopathologically proven FCD and normal magnetic resonance imaging (MRI). MSI was used to localize the sources of both ictal activity and FRBEA, which was then compared with ECoG findings. The intracranial sources of both types of activity co-localized in the left inferior frontal and superior temporal gyri. The location and extent of the epileptogenic area determined by MSI was essentially identical to that determined directly through extra-operative ECoG. In the absence of structural abnormalities detectable on MRI, the noninvasive method of MSI provided valuable information regarding the location and extent of the primary epileptogenic area. This was critical for pre-surgical planning regarding placement of intracranial electrodes and for risk-benefit evaluation.
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Affiliation(s)
- Hideaki Ishibashi
- Department of Neurosurgery, Vivian L Smith Center for Neurologic Research, The University of Texas Health Science Center at Houston, 77030, USA.
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Ishibashi H, Simos PG, Wheless JE, Zhang W, Baumgartner JE, Castillo EM, Papanicolaou AC. Somatosensory evoked magnetic fields in hemimegalencephaly. Neurol Res 2002; 24:459-62. [PMID: 12117314 DOI: 10.1179/016164102101200339] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Somatosensory maps were determined in three patients with hemimegalencephaly using magnetic resonance imaging (MRI) and magnetoencephalography (MEG). MRIs were characterized by thickened gray matter with clearly aberrant lamination patterns. Somatosensory Evoked Fields (SEFs), as measured by MEG, were absent from the affected hemisphere in the two patients with severe cortical lamination defects. The third patient presented with relatively preserved cortical lamination in the frontal lobe and clear cortical SEFs in this region, indicating somatotopical reorganization. These findings suggest that the presence and location of MEG-derived somatosensory maps reflect the severity of the cortical lamination defects in hemimegalencephaly.
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Affiliation(s)
- Hideaki Ishibashi
- Department of Neurosurgery, Vivian L Smith Center for Neurologic Research, The University of Texas Health Science Center at Houston, 77030, USA.
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Ishibashi H, Simos PG, Wheless JW, Baumgartner JE, Kim HL, Davis RN, Zhang W, Papanicolaou AC. Multimodality functional imaging evaluation in a patient with Rasmussen's encephalitis. Brain Dev 2002; 24:239-44. [PMID: 12015167 DOI: 10.1016/s0387-7604(02)00036-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Rasmussen's encephalitis (RE) is a cryptogenic progressive inflammatory disorder of the brain that causes severe neurological problems, including intractable focal epilepsy. In select patients, aggressive treatment using cerebral hemispherectomy may ameliorate the devastating cognitive decline that accompanies this disease, even if the epileptic focus appears broadly distributed. We present a case of histopathologically-confirmed RE evaluated using a multimodal process that explored the physical and functional aspects of the associated epilepsy. This process included magnetic resonance imaging, single photo emission computed tomography, electroencephalography, and magnetoencephalography (MEG). The findings indicate that functional brain imaging data may greatly assist the surgical treatment decision-making process in RE, especially when structural imaging fails to reveal definitive localizing information. In addition, MEG may provide insights about the cortical reorganization of somatosensory cortex following hemispherectomy.
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Affiliation(s)
- Hideaki Ishibashi
- Department of Neurosurgery, Vivian L Smith Center for Neurologic Research, Division of Clinical Neurosciences, The University of Texas Health Science Center at Houston, USA.
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Ishibashi H, Simos PG, Castillo EM, Maggio WW, Wheless JW, Kim HL, Venkataraman V, Sanders DK, Breier JI, Zhang W, Davis RN, Papanicolaou AC. Detection and significance of focal, interictal, slow-wave activity visualized by magnetoencephalography for localization of a primary epileptogenic region. J Neurosurg 2002; 96:724-30. [PMID: 11990813 DOI: 10.3171/jns.2002.96.4.0724] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Magnetoencephalography (MEG) is a novel noninvasive diagnostic tool used to determine preoperatively the location of the epileptogenic zone in patients with epilepsy. The presence of focal slowing of activity recorded by electroencephalography (EEG) is an additional indicator of an underlying pathological condition in cases of intractable mesial temporal lobe epilepsy (MTLE). In the present study the authors examined the significance of focal, slow-wave and interictal spike activity detected using MEG in 29 patients who suffered from MTLE that was not associated with structural brain lesions. METHODS All patients underwent resective surgery after MEG and EEG monitoring. Equivalent single-dipole modeling was applied to focal low-frequency magnetic activity (LFMA) and interictal paroxysmal activity. Lateralized LFMA was defined as trains of rhythmic activity over the temporal area, with frequencies lower than 7 Hz, which were easily distinguished from background activity. Lateralized LFMA was found in 17 patients (58.6%); it always occurred on the side ipsilateral to the side of resection and displayed a maximum amplitude over the temporal area. Dipolar sources of magnetic flux computed during slow-wave trains were found in the majority of cases in the posterior superior temporal region and, occasionally, in mesial temporal structures that were subsequently resected. With respect to lateralization there was never disagreement between LFMA and MEG interictal spike sources. Thus, in patients with MTLE that is not associated with a mass lesion LFMA is topographically related to the epileptogenic area and, therefore, has value for reliable determination of the side and, possibly, the location of this area. CONCLUSIONS Although focal slowing of EEG background activity is generally considered to be a nonspecific sign of functional disturbance, interictal LFMA in patients with MTLE should be conceptualized as a distinct electrographic phenomenon that is directly related to the epileptogenic abnormality. Analyzing the interictal MEG distribution of LFMA and sharp activity improves the diagnostic utility of MEG in patients with suspected TLE who are undergoing surgical evaluation.
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Affiliation(s)
- Hideaki Ishibashi
- Vivian L. Smith Foundation for Neurological Research, Department of Neurosurgery, The University of Texas Houston Health Science Center, Houston 77030, USA.
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