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Shi LJ, Li CC, Zhang XT, Lin YC, Wang YP, Zhang JC. Application of HFO and scaling analysis of neuronal oscillations in the presurgical evaluation of focal epilepsy. Brain Res Bull 2024; 215:111018. [PMID: 38908759 DOI: 10.1016/j.brainresbull.2024.111018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 03/07/2024] [Accepted: 06/19/2024] [Indexed: 06/24/2024]
Abstract
PURPOSE To explore the utility of high frequency oscillations (HFO) and long-range temporal correlations (LRTCs) in preoperative assessment of epilepsy. METHODS MEG ripples were detected in 59 drug-resistant epilepsy patients, comprising 5 with parietal lobe epilepsy (PLE), 21 with frontal lobe epilepsy (FLE), 14 with lateral temporal lobe epilepsy (LTLE), and 19 with mesial temporal lobe epilepsy (MTLE) to identify the epileptogenic zone (EZ). The results were compared with clinical MEG reports and resection area. Subsequently, LRTCs were quantified at the source-level by detrended fluctuation analysis (DFA) and life/waiting -time at 5 bands for 90 cerebral cortex regions. The brain regions with larger DFA exponents and standardized life-waiting biomarkers were compared with the resection results. RESULTS Compared to MEG sensor-level data, ripple sources were more frequently localized within the resection area. Moreover, source-level analysis revealed a higher proportion of DFA exponents and life-waiting biomarkers with relatively higher rankings, primarily distributed within the resection area (p<0.01). Moreover, these two LRCT indices across five distinct frequency bands correlated with EZ. CONCLUSION HFO and source-level LRTCs are correlated with EZ. Integrating HFO and LRTCs may be an effective approach for presurgical evaluation of epilepsy.
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Affiliation(s)
- Li-Juan Shi
- School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Centre for Big Data-Based Precision Medicine, Beihang University, Beijing, China; Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China
| | - Can-Cheng Li
- School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Centre for Big Data-Based Precision Medicine, Beihang University, Beijing, China; Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China
| | - Xia-Ting Zhang
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing 100053, China; Brain Functional Disease and Neuromodulation of Beijing Key Laboratory, Beijing 100053, China
| | - Yi-Cong Lin
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing 100053, China; Brain Functional Disease and Neuromodulation of Beijing Key Laboratory, Beijing 100053, China
| | - Yu-Ping Wang
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing 100053, China; Brain Functional Disease and Neuromodulation of Beijing Key Laboratory, Beijing 100053, China.
| | - Ji-Cong Zhang
- School of Biological Science and Medical Engineering, Beihang University, Beijing 100191, China; Beijing Advanced Innovation Centre for Big Data-Based Precision Medicine, Beihang University, Beijing, China; Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China; Hefei Innovation Research Institute, Beihang University, Hefei, Anhui, China.
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Cuesta P, Bruña R, Shah E, Laohathai C, Garcia-Tarodo S, Funke M, Von Allmen G, Maestú F. An individual data-driven virtual resection model based on epileptic network dynamics in children with intractable epilepsy: a magnetoencephalography interictal activity application. Brain Commun 2023; 5:fcad168. [PMID: 37274829 PMCID: PMC10236945 DOI: 10.1093/braincomms/fcad168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Revised: 01/24/2023] [Accepted: 05/23/2023] [Indexed: 06/07/2023] Open
Abstract
Epilepsy surgery continues to be a recommended treatment for intractable (medication-resistant) epilepsy; however, 30-70% of epilepsy surgery patients can continue to have seizures. Surgical failures are often associated with incomplete resection or inaccurate localization of the epileptogenic zone. This retrospective study aims to improve surgical outcome through in silico testing of surgical hypotheses through a personalized computational neurosurgery model created from individualized patient's magnetoencephalography recording and MRI. The framework assesses the extent of the epileptic network and evaluates underlying spike dynamics, resulting in identification of one single brain volume as a candidate for resection. Dynamic-locked networks were utilized for virtual cortical resection. This in silico protocol was tested in a cohort of 24 paediatric patients with focal drug-resistant epilepsy who underwent epilepsy surgery. Of 24 patients who were included in the analysis, 79% (19 of 24) of the models agreed with the patient's clinical surgery outcome and 21% (5 of 24) were considered as model failures (accuracy 0.79, sensitivity 0.77, specificity 0.82). Patients with unsuccessful surgery outcome typically showed a model cluster outside of the resected cavity, while those with successful surgery showed the cluster model within the cavity. Two of the model failures showed the cluster in the vicinity of the resected tissue and either a functional disconnection or lack of precision of the magnetoencephalography-MRI overlapping could explain the results. Two other cases were seizure free for 1 year but developed late recurrence. This is the first study that provides in silico personalized protocol for epilepsy surgery planning using magnetoencephalography spike network analysis. This model could provide complementary information to the traditional pre-surgical assessment methods and increase the proportion of patients achieving seizure-free outcome from surgery.
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Affiliation(s)
- Pablo Cuesta
- Correspondence to: Pablo Cuesta Pza. Ramón y Cajal, s/n. Ciudad Universitaria 28040 Madrid, Spain E-mail:
| | - Ricardo Bruña
- Department of Radiology, Rehabilitation and Physiotherapy, Universidad Complutense de Madrid, Madrid, 28040, Spain
- Instituto de Investigación Sanitaria San Carlos (IdISSC), Madrid, 28040, Spain
| | - Ekta Shah
- Department of Pediatrics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | | | - Stephanie Garcia-Tarodo
- Département de la femme, de l'enfant et de l'adolescent, Hôpital des Enfants - Hôpitaux Universitaires de Genève, Geneva, 1211 Genève 14, Switzerland
| | - Michael Funke
- Department of Pediatrics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Gretchen Von Allmen
- Department of Pediatrics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Fernando Maestú
- Center for Cognitive and Computational Neuroscience, Complutense University of Madrid, Madrid, 28040, Spain
- Instituto de Investigación Sanitaria San Carlos (IdISSC), Madrid, 28040, Spain
- Department of Pediatrics, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
- Department of Experimental Psychology, Cognitive Processes and Speech Therapy, Universidad Complutense de Madrid, Madrid, 28040, Spain
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Abstract
Pain is an unpleasant sensory and emotional experience. Understanding the neural mechanisms of acute and chronic pain and the brain changes affecting pain factors is important for finding pain treatment methods. The emergence and progress of non-invasive neuroimaging technology can help us better understand pain at the neural level. Recent developments in identifying brain-based biomarkers of pain through advances in advanced imaging can provide some foundations for predicting and detecting pain. For example, a neurologic pain signature (involving brain regions that receive nociceptive afferents) and a stimulus intensity-independent pain signature (involving brain regions that do not show increased activity in proportion to noxious stimulus intensity) were developed based on multivariate modeling to identify processes related to the pain experience. However, an accurate and comprehensive review of common neuroimaging techniques for evaluating pain is lacking. This paper reviews the mechanism, clinical application, reliability, strengths, and limitations of common neuroimaging techniques for assessing pain to promote our further understanding of pain.
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Affiliation(s)
- Jing Luo
- Department of Sport Rehabilitation, Xian Physical Education University, Xian, China
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai, China
| | - Hui-Qi Zhu
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai, China
- Department of Sport Rehabilitation, Shenyang Sport University, Shenyang, China
| | - Bo Gou
- Department of Sport Rehabilitation, Xian Physical Education University, Xian, China.
| | - Xue-Qiang Wang
- Department of Sport Rehabilitation, Shanghai University of Sport, Shanghai, China.
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4
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Ntolkeras G, Tamilia E, AlHilani M, Bolton J, Ellen Grant P, Prabhu SP, Madsen JR, Stufflebeam SM, Pearl PL, Papadelis C. Presurgical accuracy of dipole clustering in MRI-negative pediatric patients with epilepsy: Validation against intracranial EEG and resection. Clin Neurophysiol 2022; 141:126-138. [PMID: 33875376 PMCID: PMC8803140 DOI: 10.1016/j.clinph.2021.01.036] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 01/21/2021] [Accepted: 01/27/2021] [Indexed: 01/24/2023]
Abstract
OBJECTIVE To assess the utility of interictal magnetic and electric source imaging (MSI and ESI) using dipole clustering in magnetic resonance imaging (MRI)-negative patients with drug resistant epilepsy (DRE). METHODS We localized spikes in low-density (LD-EEG) and high-density (HD-EEG) electroencephalography as well as magnetoencephalography (MEG) recordings using dipoles from 11 pediatric patients. We computed each dipole's level of clustering and used it to discriminate between clustered and scattered dipoles. For each dipole, we computed the distance from seizure onset zone (SOZ) and irritative zone (IZ) defined by intracranial EEG. Finally, we assessed whether dipoles proximity to resection was predictive of outcome. RESULTS LD-EEG had lower clusterness compared to HD-EEG and MEG (p < 0.05). For all modalities, clustered dipoles showed higher proximity to SOZ and IZ than scattered (p < 0.001). Resection percentage was higher in optimal vs. suboptimal outcome patients (p < 0.001); their proximity to resection was correlated to outcome (p < 0.001). No difference in resection percentage was seen for scattered dipoles between groups. CONCLUSION MSI and ESI dipole clustering helps to localize the SOZ and IZ and facilitate the prognostic assessment of MRI-negative patients with DRE. SIGNIFICANCE Assessing the MSI and ESI clustering allows recognizing epileptogenic areas whose removal is associated with optimal outcome.
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Affiliation(s)
- Georgios Ntolkeras
- Laboratory of Children's Brain Dynamics, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Eleonora Tamilia
- Laboratory of Children's Brain Dynamics, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Michel AlHilani
- Laboratory of Children's Brain Dynamics, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; The Hillingdon Hospital NHS Foundation Trust, London, United Kingdom
| | - Jeffrey Bolton
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - P Ellen Grant
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Division of Neuroradiology, Department of Radiology, Boston Children's Hospital, Harvard Medical School, MA, USA
| | - Sanjay P Prabhu
- Division of Neuroradiology, Department of Radiology, Boston Children's Hospital, Harvard Medical School, MA, USA
| | - Joseph R Madsen
- Division of Epilepsy Surgery, Department of Neurosurgery, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Steven M Stufflebeam
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Phillip L Pearl
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Christos Papadelis
- Laboratory of Children's Brain Dynamics, Division of Newborn Medicine, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA; Jane and John Justin Neurosciences Center, Cook Children's Health Care System, Fort Worth, TX, USA; School of Medicine, Texas Christian University and University of North Texas Health Science Center, Fort Worth, TX, USA; Department of Bioengineering, University of Texas at Arlington, Arlington, TX, USA.
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5
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Sasaki R, Watanabe H, Onishi H. Therapeutic benefits of noninvasive somatosensory cortex stimulation on cortical plasticity and somatosensory function: a systematic review. Eur J Neurosci 2022; 56:4669-4698. [PMID: 35804487 DOI: 10.1111/ejn.15767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 05/23/2022] [Accepted: 06/09/2022] [Indexed: 11/28/2022]
Abstract
Optimal limb coordination requires efficient transmission of somatosensory information to the sensorimotor cortex. The primary somatosensory cortex (S1) is frequently damaged by stroke, resulting in both somatosensory and motor impairments. Noninvasive brain stimulation (NIBS) to the primary motor cortex is thought to induce neural plasticity that facilitates neurorehabilitation. Several studies have also examined if NIBS to the S1 can enhance somatosensory processing as assessed by somatosensory-evoked potentials (SEPs) and improve behavioral task performance, but it remains uncertain if NIBS can reliably modulate S1 plasticity or even whether SEPs can reflect this plasticity. This systematic review revealed that NIBS has relatively minor effects on SEPs or somatosensory task performance, but larger early SEP changes after NIBS can still predict improved performance. Similarly, decreased paired-pulse inhibition in S1 post-NIBS is associated with improved somatosensory performance. However, several studies still debate the role of inhibitory function in somatosensory performance after NIBS in terms of the direction of the change (that, disinhibition or inhibition). Altogether, early SEP and paired-pulse inhibition (particularly inter-stimulus intervals of 30-100 ms) may become useful biomarkers for somatosensory deficits, but improved NIBS protocols are required for therapeutic applications.
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Affiliation(s)
- Ryoki Sasaki
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan.,Discipline of Physiology, School of Biomedicine, The University of Adelaide, Adelaide, Australia
| | - Hiraku Watanabe
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan.,Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan
| | - Hideaki Onishi
- Institute for Human Movement and Medical Sciences, Niigata University of Health and Welfare, Niigata, Japan.,Department of Physical Therapy, Niigata University of Health and Welfare, Niigata, Japan
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Jiang X, Ye S, Sohrabpour A, Bagić A, He B. Imaging the extent and location of spatiotemporally distributed epileptiform sources from MEG measurements. Neuroimage Clin 2021; 33:102903. [PMID: 34864288 PMCID: PMC8648830 DOI: 10.1016/j.nicl.2021.102903] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 11/26/2021] [Accepted: 11/27/2021] [Indexed: 11/23/2022]
Abstract
Non-invasive MEG/EEG source imaging provides valuable information about the epileptogenic brain areas which can be used to aid presurgical planning in focal epilepsy patients suffering from drug-resistant seizures. However, the source extent estimation for electrophysiological source imaging remains to be a challenge and is usually largely dependent on subjective choice. Our recently developed algorithm, fast spatiotemporal iteratively reweighted edge sparsity minimization (FAST-IRES) strategy, has been shown to objectively estimate extended sources from EEG recording, while it has not been applied to MEG recordings. In this work, through extensive numerical experiments and real data analysis in a group of focal drug-resistant epilepsy patients' interictal spikes, we demonstrated the ability of FAST-IRES algorithm to image the location and extent of underlying epilepsy sources from MEG measurements. Our results indicate the merits of FAST-IRES in imaging the location and extent of epilepsy sources for pre-surgical evaluation from MEG measurements.
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Affiliation(s)
- Xiyuan Jiang
- Department of Biomedical Engineering, Carnegie Mellon University, USA
| | - Shuai Ye
- Department of Biomedical Engineering, Carnegie Mellon University, USA
| | - Abbas Sohrabpour
- Department of Biomedical Engineering, Carnegie Mellon University, USA
| | - Anto Bagić
- University of Pittsburgh Comprehensive Epilepsy Center (UPCEC), University of Pittsburgh Medical School, USA
| | - Bin He
- Department of Biomedical Engineering, Carnegie Mellon University, USA.
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7
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Laohathai C, Ebersole JS, Mosher JC, Bagić AI, Sumida A, Von Allmen G, Funke ME. Practical Fundamentals of Clinical MEG Interpretation in Epilepsy. Front Neurol 2021; 12:722986. [PMID: 34721261 PMCID: PMC8551575 DOI: 10.3389/fneur.2021.722986] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 09/06/2021] [Indexed: 11/29/2022] Open
Abstract
Magnetoencephalography (MEG) is a neurophysiologic test that offers a functional localization of epileptic sources in patients considered for epilepsy surgery. The understanding of clinical MEG concepts, and the interpretation of these clinical studies, are very involving processes that demand both clinical and procedural expertise. One of the major obstacles in acquiring necessary proficiency is the scarcity of fundamental clinical literature. To fill this knowledge gap, this review aims to explain the basic practical concepts of clinical MEG relevant to epilepsy with an emphasis on single equivalent dipole (sECD), which is one the most clinically validated and ubiquitously used source localization method, and illustrate and explain the regional topology and source dynamics relevant for clinical interpretation of MEG-EEG.
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Affiliation(s)
- Christopher Laohathai
- Division of Child Neurology, Department of Pediatrics, McGovern Medical School at UTHealth, Houston, TX, United States
- Department of Neurology, Saint Louis University, Saint Louis, MO, United States
| | - John S. Ebersole
- Northeast Regional Epilepsy Group, Atlantic Health Neuroscience Institute, Summit, NJ, United States
| | - John C. Mosher
- Department of Neurology, McGovern Medical School at UTHealth, Houston, TX, United States
| | - Anto I. Bagić
- University of Pittsburgh Comprehensive Epilepsy Center (UPCEC), Department of Neurology, University of Pittsburgh Medical Center, Pittsburg, PA, United States
| | - Ai Sumida
- Department of Neurology, McGovern Medical School at UTHealth, Houston, TX, United States
| | - Gretchen Von Allmen
- Division of Child Neurology, Department of Pediatrics, McGovern Medical School at UTHealth, Houston, TX, United States
| | - Michael E. Funke
- Division of Child Neurology, Department of Pediatrics, McGovern Medical School at UTHealth, Houston, TX, United States
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Velmurugan J, Nagarajan SS, Mariyappa N, Mundlamuri RC, Raghavendra K, Bharath RD, Saini J, Arivazhagan A, Rajeswaran J, Mahadevan A, Malla BR, Satishchandra P, Sinha S. Magnetoencephalography imaging of high frequency oscillations strengthens presurgical localization and outcome prediction. Brain 2019; 142:3514-3529. [PMID: 31553044 PMCID: PMC6892422 DOI: 10.1093/brain/awz284] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 06/12/2019] [Accepted: 07/11/2019] [Indexed: 11/13/2022] Open
Abstract
In patients with medically refractory epilepsy, resective surgery is the mainstay of therapy to achieve seizure freedom. However, ∼20-50% of cases have intractable seizures post-surgery due to the imprecise determination of epileptogenic zone. Recent intracranial studies suggest that high frequency oscillations between 80 and 200 Hz could serve as one of the consistent epileptogenicity biomarkers for localization of the epileptogenic zone. However, these high frequency oscillations are not adopted in the clinical setting because of difficult non-invasive detection. Here, we investigated non-invasive detection and localization of high frequency oscillations and its clinical utility in accurate pre-surgical assessment and post-surgical outcome prediction. We prospectively recruited 52 patients with medically refractory epilepsy who underwent standard pre-surgical workup including magnetoencephalography (MEG) followed by resective surgery after determination of the epileptogenic zone. The post-surgical outcome was assessed after 22.14 ± 10.05 months. Interictal epileptic spikes were expertly identified, and interictal epileptic oscillations across the neural activity frequency spectrum from 8 to 200 Hz were localized using adaptive spatial filtering methods. Localization results were compared with epileptogenic zone and resected cortex for congruence assessment and validated against the clinical outcome. The concordance rate of high frequency oscillations sources (80-200 Hz) with the presumed epileptogenic zone and the resected cortex were 75.0% and 78.8%, respectively, which is superior to that of other frequency bands and standard dipole fitting methods. High frequency oscillation sources corresponding with the resected cortex, had the best sensitivity of 78.0%, positive predictive value of 100% and an accuracy of 78.84% to predict the patient's surgical outcome, among all other frequency bands. If high frequency oscillation sources were spatially congruent with resected cortex, patients had an odds ratio of 5.67 and 82.4% probability of achieving a favourable surgical outcome. If high frequency oscillations sources were discordant with the epileptogenic zone or resection area, patient has an odds ratio of 0.18 and only 14.3% probability of achieving good outcome, and mostly tended to have an unfavourable outcome (χ2 = 5.22; P = 0.02; φ = -0.317). In receiver operating characteristic curve analyses, only sources of high-frequency oscillations demonstrated the best sensitivity and specificity profile in determining the patient's surgical outcome with area under the curve of 0.76, whereas other frequency bands indicate a poor predictive performance. Our study is the first non-invasive study to detect high frequency oscillations, address the efficacy of high frequency oscillations over the different neural oscillatory frequencies, localize them and clinically validate them with the post-surgical outcome in patients with medically refractory epilepsy. The evidence presented in the current study supports the fact that HFOs might significantly improve the presurgical assessment, and post-surgical outcome prediction, where it could widely be used in a clinical setting as a non-invasive biomarker.
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Affiliation(s)
- Jayabal Velmurugan
- Department of Clinical Neurosciences, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
- MEG Research Center, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
- Department of Radiology and Biomedical Imaging, University of California San Francisco (UCSF), San Francisco, USA
| | - Srikantan S Nagarajan
- Department of Radiology and Biomedical Imaging, University of California San Francisco (UCSF), San Francisco, USA
| | - Narayanan Mariyappa
- MEG Research Center, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Ravindranadh C Mundlamuri
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Kenchaiah Raghavendra
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Rose Dawn Bharath
- Department of NIIR, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Jitender Saini
- Department of NIIR, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Arimappamagan Arivazhagan
- Department of Neurosurgery, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Jamuna Rajeswaran
- Department of Neuropsychology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Anita Mahadevan
- Department of Pathology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Bhaskara Rao Malla
- Department of Neurosurgery, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Parthasarathy Satishchandra
- MEG Research Center, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
| | - Sanjib Sinha
- MEG Research Center, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
- Department of Neurology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India
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9
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Shirozu H, Hashizume A, Masuda H, Kakita A, Otsubo H, Kameyama S. Surgical strategy for focal cortical dysplasia based on the analysis of the spike onset and peak zones on magnetoencephalography. J Neurosurg 2019; 133:1850-1862. [PMID: 31585422 DOI: 10.3171/2019.6.jns191058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 06/24/2019] [Indexed: 11/06/2022]
Abstract
OBJECTIVE The aim of this study was to elucidate the surgical strategy for focal cortical dysplasia (FCD) based on the interictal analysis on magnetoencephalography (MEG). For this purpose, the correlation between the spike onset zone (Sp-OZ) and the spike peak zone (Sp-PZ) on MEG was evaluated to clarify the differences in the Sp-OZ and its correlation with Sp-PZ in FCD subtypes to develop an appropriate surgical strategy. METHODS Forty-one FCD patients (n = 17 type I, n = 13 type IIa, and n = 11 type IIb) were included. The Sp-OZ was identified by the summation of gradient magnetic-field topography (GMFT) magnitudes at interictal MEG spike onset, and Sp-PZ was defined as the distribution of the equivalent current dipole (ECD) at spike peak. Correlations between Sp-OZ and Sp-PZ distributions were evaluated and compared with clinical factors and seizure outcomes retrospectively. RESULTS Good seizure outcomes (Engel class I) were obtained significantly more often in patients with FCD type IIb (10/11, 90.9%) than those with type IIa (4/13, 30.8%; p = 0.003) and type I (6/17, 35.3%; p = 0.004). The Sp-OZ was significantly smaller (1 or 2 gyri) in type IIb (10, 90.9%) than in type IIa (4, 30.8%; p = 0.003) or type I (9, 53.0%; p = 0.036). Concordant correlations between the Sp-OZ and Sp-PZ were significantly more frequent in type IIb (7, 63.6%) than in type IIa (1, 7.7%; p = 0.015) or type I (1, 5.8%; p = 0.004). Complete resection of the Sp-OZ achieved significantly better seizure outcomes (Engel class I: 9/10, 90%) than incomplete resection (11/31, 35.5%) (p = 0.003). In contrast, complete resection of the Sp-PZ showed no significant difference in good seizure outcomes (9/13, 69.2%) compared with incomplete resection (11/28, 39.3%). CONCLUSIONS The Sp-OZ detected by MEG using GMFT and its correlation with Sp-PZ were related to FCD subtypes. A discordant distribution between Sp-OZ and Sp-PZ in type I and IIa FCD indicated an extensive epileptogenic zone and a complex epileptic network. Type IIb showed a restricted epileptogenic zone with the smaller Sp-OZ and concordance between Sp-OZ and Sp-PZ. Complete resection of the Sp-OZ provided significantly better seizure outcomes than incomplete resection. Complete resection of the Sp-PZ was not related to seizure outcomes. There was a definite difference in the epileptogenic zone among FCD subtypes; hence, an individual surgical strategy taking into account the correlation between the Sp-OZ and Sp-PZ should be considered.
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Affiliation(s)
- Hiroshi Shirozu
- 1Department of Functional Neurosurgery, National Hospital Organization, Nishiniigata Chuo Hospital, Niigata
| | - Akira Hashizume
- 2Department of Neurosurgery, Takanobashi Central Hospital, Hiroshima
| | - Hiroshi Masuda
- 1Department of Functional Neurosurgery, National Hospital Organization, Nishiniigata Chuo Hospital, Niigata
| | - Akiyoshi Kakita
- 3Department of Pathology, Brain Research Institute, Niigata University, Niigata, Japan; and
| | - Hiroshi Otsubo
- 4Division of Neurology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Shigeki Kameyama
- 1Department of Functional Neurosurgery, National Hospital Organization, Nishiniigata Chuo Hospital, Niigata
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Sachdev HS, Patel B, McManis M, Lee M, Clarke DF. Comparing Single-Photon Emission Computed Tomography (SPECT), Electroencephalography (EEG), and Magneto-encephalography (MEG) Seizure Localizations in Pediatric Cases of Laser Ablation. J Child Neurol 2019; 34:303-308. [PMID: 30755065 DOI: 10.1177/0883073818822353] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Intractable epilepsy may have a more severe effect on children in comparison to adults because the motor, sensorial, and cognitive functions of children are still undergoing development. For this same reason, however, children maintain a greater potential for recovery from intractable epilepsy because of the remaining cerebral plasticity. Thus, after 2 unsuccessful antiepileptic medications, surgical intervention is recommended. Pre-surgical localization of the epileptogenic zone increases seizure-freedom post-surgery by 200% to 300%. Single-photon emission computed tomography (SPECT) is commonly used, with magneto-encephalography (MEG) and electroencephalography (EEG), to localize the epileptogenic zone, because it localizes cerebral blood flow. There is limited research in the efficacy of SPECT localization in pediatric pharmacoresistant epilepsy. Therefore, the objective of this study was to determine the efficacy of SPECT in it's ability to localize the epileptogenic zone in laser ablation cases of pediatric pharmacoresistant epilepsy. Out of 122 SPECTs conducted at Dell Children's Medical Center from July 2010 to January 2015, 12 underwent laser ablation. In the 12 cases of laser ablation, SPECT displayed more sensitivity and specificity than EEG and more specificity than MEG when held against the laser ablation outcomes. This study further proves that SPECT is efficacious in epileptogenic zone localization of pediatric pharmacoresistant epilepsy.
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Affiliation(s)
- Harikrishan S Sachdev
- 1 Dell Children's Medical Center of Central Texas, Austin, TX, USA.,2 University of Texas at Austin, Austin, TX, USA
| | - Bhairav Patel
- 1 Dell Children's Medical Center of Central Texas, Austin, TX, USA
| | - Mark McManis
- 1 Dell Children's Medical Center of Central Texas, Austin, TX, USA
| | - Mark Lee
- 1 Dell Children's Medical Center of Central Texas, Austin, TX, USA.,3 University of Texas Dell Medical School, Austin, TX, USA
| | - Dave F Clarke
- 3 University of Texas Dell Medical School, Austin, TX, USA.,4 Texas Children's Hospital/ Baylor College of Medicine, Houston, TX, USA
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11
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van Klink N, Mooij A, Huiskamp G, Ferrier C, Braun K, Hillebrand A, Zijlmans M. Simultaneous MEG and EEG to detect ripples in people with focal epilepsy. Clin Neurophysiol 2019; 130:1175-1183. [PMID: 30871799 DOI: 10.1016/j.clinph.2019.01.027] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 01/14/2019] [Accepted: 01/31/2019] [Indexed: 01/07/2023]
Abstract
OBJECTIVE We studied ripples (80-250 Hz) simultaneously recorded in electroencephalography (EEG) and magnetoencephalography (MEG) to evaluate the differences. METHODS Simultaneous EEG and MEG were recorded in 30 patients with drug resistant focal epilepsy. Ripples were automatically detected and visually checked in virtual channels throughout the cortex. The number and location of ripples in EEG and MEG were compared to each other and to a region of interest (ROI) defined by clinically available information. RESULTS Eleven patients showed ripples in both MEG and EEG, 11 only in EEG and one only in MEG. Twenty-four percent of the ripples occurred simultaneously in EEG and MEG, 71% only in EEG, and 5% only in MEG. Three patients without spikes in EEG showed EEG ripples. Ripple localization was concordant with the ROI in 80% of patients with MEG ripples, as opposed to 62% full or partial concordance for EEG ripples. With the optimal threshold for localizing the ROI, sensitivity and specificity were more than 80%. CONCLUSIONS Ripples in MEG are less frequent but more specific and sensitive for the region of interest than ripples in EEG. Ripples in EEG can exist without spikes in the EEG. SIGNIFICANCE Ripples in MEG and EEG provide complementary information.
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Affiliation(s)
- Nicole van Klink
- Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, the Netherlands; SEIN - Stichting Epilepsie Instellingen Nederland, Heemstede, the Netherlands.
| | - Anne Mooij
- Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, the Netherlands
| | - Geertjan Huiskamp
- Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, the Netherlands
| | - Cyrille Ferrier
- Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, the Netherlands
| | - Kees Braun
- Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, the Netherlands
| | - Arjan Hillebrand
- Department of Clinical Neurophysiology and Magnetoencephalography Center, VU University Medical Center, Amsterdam, the Netherlands
| | - Maeike Zijlmans
- Brain Center Rudolf Magnus, Department of Neurology and Neurosurgery, UMC Utrecht, the Netherlands; SEIN - Stichting Epilepsie Instellingen Nederland, Heemstede, the Netherlands
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12
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Stropahl M, Bauer AKR, Debener S, Bleichner MG. Source-Modeling Auditory Processes of EEG Data Using EEGLAB and Brainstorm. Front Neurosci 2018; 12:309. [PMID: 29867321 PMCID: PMC5952032 DOI: 10.3389/fnins.2018.00309] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/20/2018] [Indexed: 11/25/2022] Open
Abstract
Electroencephalography (EEG) source localization approaches are often used to disentangle the spatial patterns mixed up in scalp EEG recordings. However, approaches differ substantially between experiments, may be strongly parameter-dependent, and results are not necessarily meaningful. In this paper we provide a pipeline for EEG source estimation, from raw EEG data pre-processing using EEGLAB functions up to source-level analysis as implemented in Brainstorm. The pipeline is tested using a data set of 10 individuals performing an auditory attention task. The analysis approach estimates sources of 64-channel EEG data without the prerequisite of individual anatomies or individually digitized sensor positions. First, we show advanced EEG pre-processing using EEGLAB, which includes artifact attenuation using independent component analysis (ICA). ICA is a linear decomposition technique that aims to reveal the underlying statistical sources of mixed signals and is further a powerful tool to attenuate stereotypical artifacts (e.g., eye movements or heartbeat). Data submitted to ICA are pre-processed to facilitate good-quality decompositions. Aiming toward an objective approach on component identification, the semi-automatic CORRMAP algorithm is applied for the identification of components representing prominent and stereotypic artifacts. Second, we present a step-wise approach to estimate active sources of auditory cortex event-related processing, on a single subject level. The presented approach assumes that no individual anatomy is available and therefore the default anatomy ICBM152, as implemented in Brainstorm, is used for all individuals. Individual noise modeling in this dataset is based on the pre-stimulus baseline period. For EEG source modeling we use the OpenMEEG algorithm as the underlying forward model based on the symmetric Boundary Element Method (BEM). We then apply the method of dynamical statistical parametric mapping (dSPM) to obtain physiologically plausible EEG source estimates. Finally, we show how to perform group level analysis in the time domain on anatomically defined regions of interest (auditory scout). The proposed pipeline needs to be tailored to the specific datasets and paradigms. However, the straightforward combination of EEGLAB and Brainstorm analysis tools may be of interest to others performing EEG source localization.
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Affiliation(s)
- Maren Stropahl
- Neuropsychology Lab, Department of Psychology, European Medical School, University of Oldenburg, Oldenburg, Germany
| | - Anna-Katharina R Bauer
- Neuropsychology Lab, Department of Psychology, European Medical School, University of Oldenburg, Oldenburg, Germany
| | - Stefan Debener
- Neuropsychology Lab, Department of Psychology, European Medical School, University of Oldenburg, Oldenburg, Germany.,Cluster of Excellence Hearing4all, University of Oldenburg, Oldenburg, Germany
| | - Martin G Bleichner
- Neuropsychology Lab, Department of Psychology, European Medical School, University of Oldenburg, Oldenburg, Germany.,Cluster of Excellence Hearing4all, University of Oldenburg, Oldenburg, Germany
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13
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Reichert C, Dürschmid S, Heinze HJ, Hinrichs H. A Comparative Study on the Detection of Covert Attention in Event-Related EEG and MEG Signals to Control a BCI. Front Neurosci 2017; 11:575. [PMID: 29085279 PMCID: PMC5650628 DOI: 10.3389/fnins.2017.00575] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 10/02/2017] [Indexed: 11/25/2022] Open
Abstract
In brain-computer interface (BCI) applications the detection of neural processing as revealed by event-related potentials (ERPs) is a frequently used approach to regain communication for people unable to interact through any peripheral muscle control. However, the commonly used electroencephalography (EEG) provides signals of low signal-to-noise ratio, making the systems slow and inaccurate. As an alternative noninvasive recording technique, the magnetoencephalography (MEG) could provide more advantageous electrophysiological signals due to a higher number of sensors and the magnetic fields not being influenced by volume conduction. We investigated whether MEG provides higher accuracy in detecting event-related fields (ERFs) compared to detecting ERPs in simultaneously recorded EEG, both evoked by a covert attention task, and whether a combination of the modalities is advantageous. In our approach, a detection algorithm based on spatial filtering is used to identify ERP/ERF components in a data-driven manner. We found that MEG achieves higher decoding accuracy (DA) compared to EEG and that the combination of both further improves the performance significantly. However, MEG data showed poor performance in cross-subject classification, indicating that the algorithm's ability for transfer learning across subjects is better in EEG. Here we show that BCI control by covert attention is feasible with EEG and MEG using a data-driven spatial filter approach with a clear advantage of the MEG regarding DA but with a better transfer learning in EEG.
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Affiliation(s)
- Christoph Reichert
- Department of Behavioral Neurology, Leibniz Institute for Neurobiology, Magdeburg, Germany
| | - Stefan Dürschmid
- Department of Behavioral Neurology, Leibniz Institute for Neurobiology, Magdeburg, Germany.,Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany
| | - Hans-Jochen Heinze
- Department of Behavioral Neurology, Leibniz Institute for Neurobiology, Magdeburg, Germany.,Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany.,German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
| | - Hermann Hinrichs
- Department of Behavioral Neurology, Leibniz Institute for Neurobiology, Magdeburg, Germany.,Department of Neurology, Otto-von-Guericke University, Magdeburg, Germany.,German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Germany.,Center for Behavioral Brain Sciences, Magdeburg, Germany
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14
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Yu M, Engels MMA, Hillebrand A, van Straaten ECW, Gouw AA, Teunissen C, van der Flier WM, Scheltens P, Stam CJ. Selective impairment of hippocampus and posterior hub areas in Alzheimer’s disease: an MEG-based multiplex network study. Brain 2017; 140:1466-1485. [PMID: 28334883 DOI: 10.1093/brain/awx050] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 01/14/2017] [Indexed: 12/11/2022] Open
Affiliation(s)
- Meichen Yu
- Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Marjolein M A Engels
- Alzheimer Center and Department of Neurology, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Arjan Hillebrand
- Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Elisabeth C W van Straaten
- Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
- Nutricia Advanced Medical Nutrition, Nutricia Research, Utrecht, The Netherlands
| | - Alida A Gouw
- Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
- Alzheimer Center and Department of Neurology, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Charlotte Teunissen
- Neurochemistry lab and Biobank, Department of Clinical Chemistry, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Wiesje M van der Flier
- Alzheimer Center and Department of Neurology, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
- Department of Epidemiology and Biostatistics, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Philip Scheltens
- Alzheimer Center and Department of Neurology, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Cornelis J Stam
- Department of Clinical Neurophysiology and MEG Center, Neuroscience Campus Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
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15
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Magnetoencephalography for brain electrophysiology and imaging. Nat Neurosci 2017; 20:327-339. [DOI: 10.1038/nn.4504] [Citation(s) in RCA: 418] [Impact Index Per Article: 59.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Accepted: 01/17/2017] [Indexed: 12/18/2022]
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16
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Tamilia E, Madsen JR, Grant PE, Pearl PL, Papadelis C. Current and Emerging Potential of Magnetoencephalography in the Detection and Localization of High-Frequency Oscillations in Epilepsy. Front Neurol 2017; 8:14. [PMID: 28194133 PMCID: PMC5276819 DOI: 10.3389/fneur.2017.00014] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 01/11/2017] [Indexed: 01/19/2023] Open
Abstract
Up to one-third of patients with epilepsy are medically intractable and need resective surgery. To be successful, epilepsy surgery requires a comprehensive preoperative evaluation to define the epileptogenic zone (EZ), the brain area that should be resected to achieve seizure freedom. Due to lack of tools and methods that measure the EZ directly, this area is defined indirectly based on concordant data from a multitude of presurgical non-invasive tests and intracranial recordings. However, the results of these tests are often insufficiently concordant or inconclusive. Thus, the presurgical evaluation of surgical candidates is frequently challenging or unsuccessful. To improve the efficacy of the surgical treatment, there is an overriding need for reliable biomarkers that can delineate the EZ. High-frequency oscillations (HFOs) have emerged over the last decade as new potential biomarkers for the delineation of the EZ. Multiple studies have shown that HFOs are spatially associated with the EZ. Despite the encouraging findings, there are still significant challenges for the translation of HFOs as epileptogenic biomarkers to the clinical practice. One of the major barriers is the difficulty to detect and localize them with non-invasive techniques, such as magnetoencephalography (MEG) or scalp electroencephalography (EEG). Although most literature has studied HFOs using invasive recordings, recent studies have reported the detection and localization of HFOs using MEG or scalp EEG. MEG seems to be particularly advantageous compared to scalp EEG due to its inherent advantages of being less affected by skull conductivity and less susceptible to contamination from muscular activity. The detection and localization of HFOs with MEG would largely expand the clinical utility of these new promising biomarkers to an earlier stage in the diagnostic process and to a wider range of patients with epilepsy. Here, we conduct a thorough critical review of the recent MEG literature that investigates HFOs in patients with epilepsy, summarizing the different methodological approaches and the main findings. Our goal is to highlight the emerging potential of MEG in the non-invasive detection and localization of HFOs for the presurgical evaluation of patients with medically refractory epilepsy (MRE).
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Affiliation(s)
- Eleonora Tamilia
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Joseph R. Madsen
- Division of Epilepsy Surgery, Department of Neurosurgery, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Patricia Ellen Grant
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Phillip L. Pearl
- Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Christos Papadelis
- Fetal-Neonatal Neuroimaging and Developmental Science Center, Division of Newborn Medicine, Department of Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA
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17
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Nissen IA, Stam CJ, Reijneveld JC, van Straaten IECW, Hendriks EJ, Baayen JC, De Witt Hamer PC, Idema S, Hillebrand A. Identifying the epileptogenic zone in interictal resting-state MEG source-space networks. Epilepsia 2016; 58:137-148. [PMID: 27888520 DOI: 10.1111/epi.13622] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2016] [Indexed: 01/07/2023]
Abstract
OBJECTIVE In one third of patients, seizures remain after epilepsy surgery, meaning that improved preoperative evaluation methods are needed to identify the epileptogenic zone. A potential framework for such a method is network theory, as it can be applied to noninvasive recordings, even in the absence of epileptiform activity. Our aim was to identify the epileptogenic zone on the basis of hub status of local brain areas in interictal magnetoencephalography (MEG) networks. METHODS Preoperative eyes-closed resting-state MEG recordings were retrospectively analyzed in 22 patients with refractory epilepsy, of whom 14 were seizure-free 1 year after surgery. Beamformer-based time series were reconstructed for 90 cortical and subcortical automated anatomic labeling (AAL) regions of interest (ROIs). Broadband functional connectivity was estimated using the phase lag index in artifact-free epochs without interictal epileptiform abnormalities. A minimum spanning tree was generated to represent the network, and the hub status of each ROI was calculated using betweenness centrality, which indicates the centrality of a node in a network. The correspondence of resection cavity to hub values was evaluated on four levels: resection cavity, lobar, hemisphere, and temporal versus extratemporal areas. RESULTS Hubs were localized within the resection cavity in 8 of 14 seizure-free patients and in zero of 8 patients who were not seizure-free (57% sensitivity, 100% specificity, 73% accuracy). Hubs were localized in the lobe of resection in 9 of 14 seizure-free patients and in zero of 8 patients who were not seizure-free (64% sensitivity, 100% specificity, 77% accuracy). For the other two levels, the true negatives are unknown; hence, only sensitivity could be determined: hubs coincided with both the resection hemisphere and the resection location (temporal versus extratemporal) in 11 of 14 seizure-free patients (79% sensitivity). SIGNIFICANCE Identifying hubs noninvasively before surgery is a valuable approach with the potential of indicating the epileptogenic zone in patients without interictal abnormalities.
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Affiliation(s)
- Ida A Nissen
- Department of Clinical Neurophysiology and MEG Center, VU University Medical Center, Amsterdam, The Netherlands
| | - Cornelis J Stam
- Department of Clinical Neurophysiology and MEG Center, VU University Medical Center, Amsterdam, The Netherlands
| | - Jaap C Reijneveld
- Brain Tumor Center Amsterdam & Department of Neurology, VU University Medical Center, Amsterdam, The Netherlands
| | - Ilse E C W van Straaten
- Department of Clinical Neurophysiology and MEG Center, VU University Medical Center, Amsterdam, The Netherlands
| | - Eef J Hendriks
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Johannes C Baayen
- Neurosurgical Center Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Philip C De Witt Hamer
- Neurosurgical Center Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Sander Idema
- Neurosurgical Center Amsterdam, VU University Medical Center, Amsterdam, The Netherlands
| | - Arjan Hillebrand
- Department of Clinical Neurophysiology and MEG Center, VU University Medical Center, Amsterdam, The Netherlands
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18
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Kim D, Joo EY, Seo DW, Kim MY, Lee YH, Kwon HC, Kim JM, Hong SB. Accuracy of MEG in localizing irritative zone and seizure onset zone: Quantitative comparison between MEG and intracranial EEG. Epilepsy Res 2016; 127:291-301. [PMID: 27693985 DOI: 10.1016/j.eplepsyres.2016.08.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 07/25/2016] [Accepted: 08/14/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND We conducted the study to examine accuracy of the magnetoencephalography (MEG) spike source localization in presurgical evaluation of patients with medically refractory focal epilepsy. METHODS Ten consecutive patients with refractory focal epilepsy who were candidates for two-stage surgery with long-term intracranial electroencephalography (ICEEG) monitoring were enrolled. Interictal MEG recordings with simultaneous scalp EEG were obtained within 7days before the ICEEG electrode implantation. The location of each MEG spike source was quantitatively compared with ICEEG spike foci (focal area of interictal spikes) and ICEEG ictal foci (earliest cortical origin of seizures). Gyral-width concordance and sublobar concordance were also determined for all MEG spike sources. Gyral-width concordance was defined by distance of 15mm or less between MEG spike sources and ICEEG spike foci or ICEEG ictal foci. RESULTS Visual analyses of the MEG traces of all 10 patients revealed 292 spikes (29.2±24.0 per patient). Spike yield of the MEG was similar to the simultaneously recorded scalp EEG. MEG spike sources were closely located with ICEEG spike foci (distance: 9.3±10.8mm). Clustered MEG spike sources were even closer to ICEEG spike foci (distance: 7.3±6.4mm). MEG spike sources, even clustered ones, were less concordant with ICEEG ictal foci and had significant longer distance from ICEEG ictal foci (distance: 21.5±15.6mm for all sources, 19.7±13.7mm for clustered sources). Gyral-width concordance rate and sublobar concordance rate were also higher with ICEEG interictal spike foci than with ICEEG ictal foci. On the other hand, 53.4% of interictal spike foci from ICEEG were not detected by interictal MEG recordings. CONCLUSIONS MEG spike sources, especially clustered ones, from interictal recording could localize the irritative zone of ICEEG with a high accuracy. However, MEG spike sources have relatively poor correlation with seizure onset zone and lower sensitivity in identifying all irritative zones of ICEEG. This limitation should be considered in the interpretation of MEG results.
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Affiliation(s)
- Daeyoung Kim
- Department of Neurology, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Republic of Korea
| | - Eun Yeon Joo
- Department of Neurology, Samsung Medical Center, Samsung Advanced Institute for Health Sciences & Technology (SAIHST), Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Dae-Won Seo
- Department of Neurology, Samsung Medical Center, Samsung Advanced Institute for Health Sciences & Technology (SAIHST), Sungkyunkwan University School of Medicine, Seoul, Republic of Korea
| | - Min-Young Kim
- Center for Biosignals, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea
| | - Yong-Ho Lee
- Center for Biosignals, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea
| | - Hyuk Chan Kwon
- Center for Biosignals, Korea Research Institute of Standards and Science, Daejeon, Republic of Korea
| | - Jae-Moon Kim
- Department of Neurology, Chungnam National University Hospital, Chungnam National University School of Medicine, Daejeon, Republic of Korea.
| | - Seung Bong Hong
- Department of Neurology, Samsung Medical Center, Samsung Advanced Institute for Health Sciences & Technology (SAIHST), Sungkyunkwan University School of Medicine, Seoul, Republic of Korea; Samsung Biomedical Research Institute, Seoul, Republic of Korea.
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19
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Duez L, Beniczky S, Tankisi H, Hansen PO, Sidenius P, Sabers A, Fuglsang-Frederiksen A. Added diagnostic value of magnetoencephalography (MEG) in patients suspected for epilepsy, where previous, extensive EEG workup was unrevealing. Clin Neurophysiol 2016; 127:3301-5. [PMID: 27573996 DOI: 10.1016/j.clinph.2016.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 08/04/2016] [Accepted: 08/07/2016] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To elucidate the possible additional diagnostic yield of MEG in the workup of patients with suspected epilepsy, where repeated EEGs, including sleep-recordings failed to identify abnormalities. METHODS Fifty-two consecutive patients with clinical suspicion of epilepsy and at least three normal EEGs, including sleep-EEG, were prospectively analyzed. The reference standard was inferred from the diagnosis obtained from the medical charts, after at least one-year follow-up. MEG (306-channel, whole-head) and simultaneous EEG (MEG-EEG) was recorded for one hour. The added sensitivity of MEG was calculated from the cases where abnormalities were seen in MEG but not EEG. RESULTS Twenty-two patients had the diagnosis epilepsy according to the reference standard. MEG-EEG detected abnormalities, and supported the diagnosis in nine of the 22 patients with the diagnosis epilepsy at one-year follow-up. Sensitivity of MEG-EEG was 41%. The added sensitivity of MEG was 18%. MEG-EEG was normal in 28 of the 30 patients categorized as 'not epilepsy' at one year follow-up, yielding a specificity of 93%. CONCLUSIONS MEG provides additional diagnostic information in patients suspected for epilepsy, where repeated EEG recordings fail to demonstrate abnormality. SIGNIFICANCE MEG should be included in the diagnostic workup of patients where the conventional, widely available methods are unrevealing.
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Affiliation(s)
- Lene Duez
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark.
| | - Sándor Beniczky
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark; Department of Clinical Neurophysiology, Danish Epilepsy Centre, Dianalund, Denmark
| | - Hatice Tankisi
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Peter Orm Hansen
- Department of Clinical Neurophysiology, Aarhus University Hospital, Aarhus, Denmark
| | - Per Sidenius
- Department of Neurology, Aarhus University Hospital, Aarhus, Denmark
| | - Anne Sabers
- Department of Neurology, Copenhagen University Hospital, Rigshospitalet-Blegdamsvej, Copenhagen, Denmark
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20
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Mapping cortical responses to speech using high-density diffuse optical tomography. Neuroimage 2015; 117:319-26. [PMID: 26026816 DOI: 10.1016/j.neuroimage.2015.05.058] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Revised: 04/16/2015] [Accepted: 05/20/2015] [Indexed: 11/21/2022] Open
Abstract
The functional neuroanatomy of speech processing has been investigated using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) for more than 20years. However, these approaches have relatively poor temporal resolution and/or challenges of acoustic contamination due to the constraints of echoplanar fMRI. Furthermore, these methods are contraindicated because of safety concerns in longitudinal studies and research with children (PET) or in studies of patients with metal implants (fMRI). High-density diffuse optical tomography (HD-DOT) permits presenting speech in a quiet acoustic environment, has excellent temporal resolution relative to the hemodynamic response, and provides noninvasive and metal-compatible imaging. However, the performance of HD-DOT in imaging the brain regions involved in speech processing is not fully established. In the current study, we use an auditory sentence comprehension task to evaluate the ability of HD-DOT to map the cortical networks supporting speech processing. Using sentences with two levels of linguistic complexity, along with a control condition consisting of unintelligible noise-vocoded speech, we recovered a hierarchically organized speech network that matches the results of previous fMRI studies. Specifically, hearing intelligible speech resulted in increased activity in bilateral temporal cortex and left frontal cortex, with syntactically complex speech leading to additional activity in left posterior temporal cortex and left inferior frontal gyrus. These results demonstrate the feasibility of using HD-DOT to map spatially distributed brain networks supporting higher-order cognitive faculties such as spoken language.
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21
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Kharkar S, Knowlton R. Magnetoencephalography in the presurgical evaluation of epilepsy. Epilepsy Behav 2015; 46:19-26. [PMID: 25555504 DOI: 10.1016/j.yebeh.2014.11.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Revised: 11/24/2014] [Accepted: 11/27/2014] [Indexed: 11/27/2022]
Abstract
Magnetoencephalography (MEG) is an important tool in the presurgical evaluation of patients with medically refractory epilepsy. The appropriate utilization and interpretation of MEG studies can increase the proportion of patients who may be able to further pursue surgical evaluation, refine surgical planning, and potentially increase the probability of seizure freedom after surgery. The aim of this paper is to provide the reader with a comprehensive but accessible guide to MEG, with particular emphasis on acquiring a working knowledge of MEG analysis, identifying patient groups that are most likely to benefit, and clarifying the limitations of this technology.
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Affiliation(s)
| | - Robert Knowlton
- Department of Neurology, University of California at San Francisco, USA; Department of Radiology, University of California at San Francisco, USA; Department of Neurological Surgery, University of California at San Francisco, USA
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Gavaret M, Maillard L, Jung J. High-resolution EEG (HR-EEG) and magnetoencephalography (MEG). Neurophysiol Clin 2015; 45:105-11. [DOI: 10.1016/j.neucli.2014.11.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 11/09/2014] [Indexed: 10/24/2022] Open
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Adjamian P. The application of electro- and magneto-encephalography in tinnitus research - methods and interpretations. Front Neurol 2014; 5:228. [PMID: 25431567 PMCID: PMC4230045 DOI: 10.3389/fneur.2014.00228] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Accepted: 10/22/2014] [Indexed: 12/11/2022] Open
Abstract
In recent years, there has been a significant increase in the use of electroencephalography (EEG) and magnetoencephalography (MEG) to investigate changes in oscillatory brain activity associated with tinnitus with many conflicting results. Current view of the underlying mechanism of tinnitus is that it results from changes in brain activity in various structures of the brain as a consequence of sensory deprivation. This in turn gives rise to increased spontaneous activity and/or synchrony in the auditory centers but also involves modulation from non-auditory processes from structures of the limbic and paralimbic system. Some of the neural changes associated with tinnitus may be assessed non-invasively in human beings with MEG and EEG (M/EEG) in ways, which are superior to animal studies and other non-invasive imaging techniques. However, both MEG and EEG have their limitations and research results can be misinterpreted without appropriate consideration of these limitations. In this article, I intend to provide a brief review of these techniques, describe what the recorded signals reflect in terms of the underlying neural activity, and their strengths and limitations. I also discuss some pertinent methodological issues involved in tinnitus-related studies and conclude with suggestions to minimize possible discrepancies between results. The overall message is that while MEG and EEG are extremely useful techniques, the interpretation of results from tinnitus studies requires much caution given the individual variability in oscillatory activity and the limits of these techniques.
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[French guidelines on electroencephalogram]. Neurophysiol Clin 2014; 44:515-612. [PMID: 25435392 DOI: 10.1016/j.neucli.2014.10.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2014] [Accepted: 10/07/2014] [Indexed: 12/11/2022] Open
Abstract
Electroencephalography allows the functional analysis of electrical brain cortical activity and is the gold standard for analyzing electrophysiological processes involved in epilepsy but also in several other dysfunctions of the central nervous system. Morphological imaging yields complementary data, yet it cannot replace the essential functional analysis tool that is EEG. Furthermore, EEG has the great advantage of being non-invasive, easy to perform and allows control tests when follow-up is necessary, even at the patient's bedside. Faced with the advances in knowledge, techniques and indications, the Société de Neurophysiologie Clinique de Langue Française (SNCLF) and the Ligue Française Contre l'Épilepsie (LFCE) found it necessary to provide an update on EEG recommendations. This article will review the methodology applied to this work, refine the various topics detailed in the following chapters. It will go over the summary of recommendations for each of these chapters and underline proposals for writing an EEG report. Some questions could not be answered by the review of the literature; in those cases, an expert advice was given by the working and reading groups in addition to the guidelines.
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Almubarak S, Alexopoulos A, Von-Podewils F, Wang ZI, Kakisaka Y, Mosher JC, Bulacio J, González-Martínez J, Bingaman W, Burgess RC. The correlation of magnetoencephalography to intracranial EEG in localizing the epileptogenic zone: A study of the surgical resection outcome. Epilepsy Res 2014; 108:1581-90. [DOI: 10.1016/j.eplepsyres.2014.08.016] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2014] [Revised: 07/20/2014] [Accepted: 08/21/2014] [Indexed: 11/27/2022]
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Abstract
Magnetoencephalography (MEG) is a functional modality to register magnetic brain activity with high spatiotemporal resolution. Since distortion of magnetic fields by the skin, skull and cerebrospinal fluids is negligible, the technique offers an almost undistorted view on brain activity. While MEG systems are still expensive and complex, the technique's characteristics offer promising possibilities for the investigation of epilepsy patients, for example, for focus localization and presurgical functional mapping. This review gives an overview of the method and discusses advantages and limitations in the clinical context of presurgical epilepsy diagnosis.
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Affiliation(s)
- Stefan Rampp
- Epilepsy Center (ZEE), Department of Neurology, University Hospital, Schwabachanlage 6, 91054 Erlangen, Germany.
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Gavaret M, Badier JM, Bartolomei F, Bénar CG, Chauvel P. MEG and EEG Sensitivity in a Case of Medial Occipital Epilepsy. Brain Topogr 2013; 27:192-6. [DOI: 10.1007/s10548-013-0317-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 08/31/2013] [Indexed: 11/24/2022]
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Yamazaki M, Tucker DM, Terrill M, Fujimoto A, Yamamoto T. Dense array EEG source estimation in neocortical epilepsy. Front Neurol 2013; 4:42. [PMID: 23717298 PMCID: PMC3652005 DOI: 10.3389/fneur.2013.00042] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Accepted: 04/15/2013] [Indexed: 11/13/2022] Open
Abstract
RATIONALE Dense array EEG (dEEG) evenly covers the whole head surface with over 100 channels contributing to more accurate electrical source imaging due to the higher spatial and temporal resolution. Several studies have shown the clinical utility of dEEG in presurgical clinical evaluation of epilepsy. However validation studies measuring the accuracy of dEEG source imaging are still needed. This can be achieved through simultaneously recording both scalp dEEG with intracranial electrodes (icEEG), which is considered as the true measure of cortical activity at the source. The purpose of this study is to evaluate the accuracy of 256-channel dEEG electrical source estimation for interictal spikes. METHODS Four patients with medically refractory neocortical epilepsy, all surgical candidates, underwent subdural electrode implantation to determine ictal onset and define functional areas. One patient showed a lesion on the magnetic resonance imaging in the right parietal lobe. The patient underwent simultaneous recording of interictal spikes by both scalp 256-channelsvdEEG and icEEG. The dEEG was used to non-invasively estimate the source of the interictal spikes detected by the 256-channel dEEG array, which was then compared to the activity measured directly at the source by the icEEG. RESULTS From the four patients, a total of 287 interictal spikes were measured with the icEEG. One hundred fifty-five of the 287 spikes (54%) were visually detected by the dEEG upon examination of the 256 channel head surface array. The spike amplitudes detected by the 256-channel dEEG correlated with icEEG spike amplitudes (p < 0.01). All spikes detected in dEEG were localized to the same lobe correctly. CONCLUSION Our study demonstrates that 256-channel dEEG can reliably detect interictal spikes and localize them with reasonable accuracy. Two hundred fifty-six-channel dEEG may be clinically useful in the presurgical workup for epilepsy and also reduce the need for invasive EEG evaluation.
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Affiliation(s)
- Madoka Yamazaki
- Department of Health Science, Daito Bunka UniversitySaitama, Japan
- Comprehensive Epilepsy Center, Seirei Hamamatsu General HospitalShizuoka, Japan
| | - Don M. Tucker
- Department of Psychology, University of OregonEugene, OR, USA
- Electrical Geodesics, Inc.Eugene, OR, USA
| | | | - Ayataka Fujimoto
- Comprehensive Epilepsy Center, Seirei Hamamatsu General HospitalShizuoka, Japan
| | - Takamichi Yamamoto
- Comprehensive Epilepsy Center, Seirei Hamamatsu General HospitalShizuoka, Japan
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Schneider F, Irene Wang Z, Alexopoulos AV, Almubarak S, Kakisaka Y, Jin K, Nair D, Mosher JC, Najm IM, Burgess RC. Magnetic source imaging and ictal SPECT in MRI-negative neocortical epilepsies: Additional value and comparison with intracranial EEG. Epilepsia 2012; 54:359-69. [DOI: 10.1111/epi.12004] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Lopes da Silva FH. The impact of EEG/MEG signal processing and modeling in the diagnostic and management of epilepsy. IEEE Rev Biomed Eng 2012; 1:143-56. [PMID: 22274902 DOI: 10.1109/rbme.2008.2008246] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This overview covers recent advances in the field of EEG/MEG signal processing and modeling in epilepsy regarding both interictal and ictal phenomena. In the first part, the main methods used in the analysis of interictal EEG/MEG epileptiform spikes are presented and discussed. Source and volume conductor models are passed in review, namely the equivalent dipole source concept, the requirements for adequate time and spatial sampling, the question of how to validate source solutions, particularly by comparing solutions obtained using scalp and intracranial EEG signals, EEG & MEG data, or EEG simultaneously recorded with fMRI (BOLD signals). In the second part, methods used for the characterization of seizures are considered, namely dipolar modeling of spikes at seizure onset, decomposition of seizure EEG signals into sets of orthogonal spatio-temporal components, and also methods (linear and nonlinear) of estimating seizure propagation. In the third part, the crucial issue of how the transition between interictal and seizure activity takes place is examined. In particular the vicissitudes of the efforts along the road to seizure prediction are shortly reviewed. It is argued that this question can be reduced to the problem of estimating the excitability state of neuronal populations in the course of time as a seizure approaches. The value of active probing methods in contrast with passive analytical methods is emphasized. In the fourth part modeling aspects are considered in the light of two special kinds of epilepsies, absences characterized by spike-and-wave discharges and mesial temporal lobe epilepsy. These two types correspond to different scenarios regarding the transition to epileptic seizures, namely the former is a case of a jump transition and the latter is a typical case of gradual transition. In conclusion, the necessity of developing comprehensive computational models of epileptic seizures is emphasized.
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Affiliation(s)
- Fernando H Lopes da Silva
- Center of Neurosciences, Swammerdam Institute for Life Sciences, University of Amsterdam, 1098 SM Amsterdam, The Netherlands.
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Wu XT, Rampp S, Hopfengärtner R, Buchfelder M, Zhou D, Stefan H. Complementary use of video-electroencephalography and magnetoencephalography in frontal lobe epilepsy. Seizure 2012; 21:426-30. [DOI: 10.1016/j.seizure.2012.04.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 04/19/2012] [Accepted: 04/20/2012] [Indexed: 11/28/2022] Open
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Schneider F, Alexopoulos AV, Wang Z, Almubarak S, Kakisaka Y, Jin K, Nair D, Mosher JC, Najm IM, Burgess RC. Magnetic source imaging in non-lesional neocortical epilepsy: additional value and comparison with ICEEG. Epilepsy Behav 2012; 24:234-40. [PMID: 22542998 DOI: 10.1016/j.yebeh.2012.03.029] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 03/19/2012] [Accepted: 03/21/2012] [Indexed: 10/28/2022]
Abstract
OBJECTIVE To investigate the utility of magnetic source imaging (MSI) for localizing the epileptogenic zone (EZ) and predicting epilepsy surgery outcome in non-lesional neocortical focal epilepsy (NLNE) patients. METHODS Data from 18 consecutive patients with NLNE who underwent presurgical evaluation including intracranial electroencephalography (ICEEG) and MSI were studied. Follow-up after epilepsy surgery was ≥24 months. Intracranial electroencephalography and MSI results were classified using a sublobar classification. RESULTS Sublobar ICEEG focus was completely resected in 15 patients; seizure-free rate was 60%. Eight patients showed sublobar-concordant ICEEG/MSI results and complete resection of both regions; seizure-free rate was 87.5%. Seizure-free rate in cases not matching these criteria was only 30% (p=0.013). CONCLUSIONS Magnetoencephalography is a useful tool to localize the EZ and determine the site of surgical resection in NLNE patients. When sublobar concordance with ICEEG is observed, MSI increases the predictive value for a seizure-free epilepsy surgery outcome in these patients.
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Affiliation(s)
- Felix Schneider
- Cleveland Clinic Epilepsy Center, Neurological Institute, 9500 Euclid Avenue, Desk S-51, Cleveland, OH 44195, USA.
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Wu X, Rampp S, Weigel D, Kasper B, Zhou D, Stefan H. The correlation between ictal semiology and magnetoencephalographic localization in frontal lobe epilepsy. Epilepsy Behav 2011; 22:587-91. [PMID: 21908236 DOI: 10.1016/j.yebeh.2011.08.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 07/26/2011] [Accepted: 08/07/2011] [Indexed: 11/15/2022]
Abstract
OBJECTIVE The aim of this study was to investigate the correlation of ictal semiology with localization and/or lateralization by magnetoencephalography (MEG). METHODS Seven patients from the Neurology Department of the University Hospital Erlangen who underwent resective surgery for frontal lobe epilepsy (FLE) with an Engel 1a outcome were investigated retrospectively. MEG localizations were classified according to five compartments (separate or combined) of the frontal lobe: frontal basal (FB), frontal lateral (FL), frontal polar (FP), frontal mesial (FM), and frontal precentral (FPr). On the basis of previous studies that investigated the value of ictal semiology in localization and lateralization, we compared the experiential localization and/or lateralization of the epileptogenic region deduced from ictal semiology, that is, both seizure history and ictal video/EEG monitoring, with MEG localization. RESULTS It is easier to determine lateralization than localization from ictal semiology because of the variety of signs and fast propagation in FLE. All of the patients had specific MEG localizations according to favorable postoperative outcome. Three patients had MEG foci associated with ictal semiology; in another four, the MEG localization was adjacent to the estimated area suggested by ictal semiology. Head version signs could be observed in all compartments of the frontal lobe: clonic in FB and FP areas; postural in FPr, FL, and FM areas; hypermotor in FB, FP, FPr, and FM areas; sensation aura in FB, FL, and FM areas; and automatisms in FP, FPr, and FL areas. All patients had concordant lateralizing and limited valuable locating information from ictal semiology, but no complete correlation with MEG foci. CONCLUSION Ictal semiology may indicate the involvement of a symptomatogenic brain region during a seizure, but extent of seizure onset in central motor or sensorimotor area is not reliable enough to indicate the seizure onset zone and favorable postoperative outcome in FLE. MEG provided specific localization of epileptic activity in a FLE compartment, and indicated the relationship between epileptogenic region and lesion. MEG can complement ictal semiology in establishing a noninvasive focal localization hypothesis.
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Affiliation(s)
- Xintong Wu
- Neurological Clinic, University Hospital Erlangen, Erlangen, Germany
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Stefan H, Wu X, Buchfelder M, Rampp S, Kasper B, Hopfengärtner R, Schmitt F, Dörfler A, Blümcke I, Zhou D, Weigel D. MEG in frontal lobe epilepsies: Localization and postoperative outcome. Epilepsia 2011; 52:2233-8. [DOI: 10.1111/j.1528-1167.2011.03265.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Increased spike frequency during general anesthesia with etomidate for magnetoencephalography in patients with focal epilepsies. Clin Neurophysiol 2010; 121:1220-6. [DOI: 10.1016/j.clinph.2010.02.161] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 12/30/2009] [Accepted: 02/16/2010] [Indexed: 10/19/2022]
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Cecchin T, Ranta R, Koessler L, Caspary O, Vespignani H, Maillard L. Seizure lateralization in scalp EEG using Hjorth parameters. Clin Neurophysiol 2010; 121:290-300. [DOI: 10.1016/j.clinph.2009.10.033] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2009] [Revised: 09/23/2009] [Accepted: 10/24/2009] [Indexed: 11/28/2022]
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Funke M, Constantino T, Van Orman C, Rodin E. Magnetoencephalography and magnetic source imaging in epilepsy. Clin EEG Neurosci 2009; 40:271-80. [PMID: 19780348 DOI: 10.1177/155005940904000409] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Magnetoencephalograpy (MEG) and Electroencephalography (EEG) provide physicians with complementary data and should not be regarded as mutually exclusive evaluative methods of cerebral activity. Relevant to this edition, MEG applications related to the surgical treatment of epilepsy will be discussed exclusively. Combined MEG/EEG data collection and analysis should be a routine diagnostic practice for patients who are still suffering seizures due to the failure of drug therapy. Clinicians in the field of epilepsy agree that a greater number of patients would benefit from surgery than are currently referred for pre-surgical evaluation. Regardless of age or presumed epilepsy syndrome, all patients deserve the possibility of living seizure-free through surgery. Technological advances in superconducting elements as well as the digital revolution were necessary for the development of MEG into a clinically valuable diagnostic tool. Compared to the examination of electrical activity of the brain, investigation into its magnetic concomitant is a more recent development. In MEG, cerebral magnetic activity is recorded using magnetometer or gradiometer whole-head systems. MEG spikes usually have a shorter duration and a steeper ascending slope than EEG spikes, and variable phase relationships to EEG. When co-registered spikes are compared, it is apparent that EEG and MEG spikes differ. There is agreement among investigators that more interictal epileptiform spikes are seen in MEG than EEG. When MEG is co-registered with invasive intracranial EEG data, the detection rate of interictal epileptiform discharges depends on the number of electrocorticographic channels that record a spike. When patients have a non-localizing video-EEG recording, MEG pinpoints the resected area in 58-72% of the cases.
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Affiliation(s)
- M Funke
- Department of Neurology, Primary Childrens Medical Center, Salt Lake City, Utah, USA.
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Bhagat M, Bhushan C, Saha G, Shimjo S, Watanabe K, Bhattacharya J. Investigating neuromagnetic brain responses against chromatic flickering stimuli by wavelet entropies. PLoS One 2009; 4:e7173. [PMID: 19779630 PMCID: PMC2747006 DOI: 10.1371/journal.pone.0007173] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2009] [Accepted: 08/23/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Photosensitive epilepsy is a type of reflexive epilepsy triggered by various visual stimuli including colourful ones. Despite the ubiquitous presence of colorful displays, brain responses against different colour combinations are not properly studied. METHODOLOGY/PRINCIPAL FINDINGS Here, we studied the photosensitivity of the human brain against three types of chromatic flickering stimuli by recording neuromagnetic brain responses (magnetoencephalogram, MEG) from nine adult controls, an unmedicated patient, a medicated patient, and two controls age-matched with patients. Dynamical complexities of MEG signals were investigated by a family of wavelet entropies. Wavelet entropy is a newly proposed measure to characterize large scale brain responses, which quantifies the degree of order/disorder associated with a multi-frequency signal response. In particular, we found that as compared to the unmedicated patient, controls showed significantly larger wavelet entropy values. We also found that Renyi entropy is the most powerful feature for the participant classification. Finally, we also demonstrated the effect of combinational chromatic sensitivity on the underlying order/disorder in MEG signals. CONCLUSIONS/SIGNIFICANCE Our results suggest that when perturbed by potentially epileptic-triggering stimulus, healthy human brain manages to maintain a non-deterministic, possibly nonlinear state, with high degree of disorder, but an epileptic brain represents a highly ordered state which making it prone to hyper-excitation. Further, certain colour combination was found to be more threatening than other combinations.
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Affiliation(s)
- Mayank Bhagat
- Department of Electrical Engineering, Indian Institute of Technology, Kharagpur, India
| | - Chitresh Bhushan
- Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur, India
| | - Goutam Saha
- Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur, India
| | - Shinsuke Shimjo
- Department of Biology, California Institute of Technology, Pasadena, California, United States of America
- NTT Communication Sciences Laboratories, Atsugi, Kanagawa, Japan
- Exploratory Research for Advanced Technology (ERATO), Japan Science & Technology Agency, Atsugi, Kanagawa, Japan
| | - Katsumi Watanabe
- Exploratory Research for Advanced Technology (ERATO), Japan Science & Technology Agency, Atsugi, Kanagawa, Japan
- Research Center of Advanced Science and Technology, University of Tokyo, Tokyo, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
| | - Joydeep Bhattacharya
- Department of Psychology, Goldsmiths College, University of London, London, United Kingdom
- Commission for Scientific Visualization, Austrian Academy of Sciences, Vienna, Austria
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García-Morales I, Maestú F, Pérez-Jiménez MA, Elices E, Ortiz T, Alvarez-Linera J, Gil-Nagel A. A clinical and magnetoencephalography study of MRI-negative startle epilepsy. Epilepsy Behav 2009; 16:166-71. [PMID: 19635686 DOI: 10.1016/j.yebeh.2009.06.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2009] [Revised: 06/08/2009] [Accepted: 06/13/2009] [Indexed: 12/21/2022]
Abstract
OBJECTIVE The goal of this study was to investigate clinical findings, ictal semiology, and results of video/electroencephalography (video/EEG), and magnetoencephalography (MEG) in patients with startle epilepsy and normal brain MRI. METHODS Four patients (mean age 12.5 years) with startle epilepsy were investigated with MRI, video/EEG, and MEG. RESULTS Epilepsy diagnosis was established in childhood, and all had spontaneous and reflex seizures. Reflex seizures were triggered by sudden, unexpected sounds and tactile stimuli. The neurological examinations and MRIs were normal. MEG recordings showed focal epileptiform activity. An ictal MEG was obtained in one patient. Source modeling yielded dipole sources in right central frontal region. CONCLUSION The present study demonstrates that the origin of epileptiform activity in startle epilepsy can be localized in brain areas associated with supplementary motor seizures, even in patients with normal brain MRI. MEG adds complementary information to the localization of epileptiform activity and can be useful in planning invasive studies in cases evaluated for epilepsy surgery.
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Affiliation(s)
- Irene García-Morales
- Epilepsy Unit, Department of Neurology, Hospital Clínico San Carlos, Madrid, Spain.
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Goldenholz DM, Ahlfors SP, Hämäläinen MS, Sharon D, Ishitobi M, Vaina LM, Stufflebeam SM. Mapping the signal-to-noise-ratios of cortical sources in magnetoencephalography and electroencephalography. Hum Brain Mapp 2009; 30:1077-86. [PMID: 18465745 DOI: 10.1002/hbm.20571] [Citation(s) in RCA: 165] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Although magnetoencephalography (MEG) and electroencephalography (EEG) have been available for decades, their relative merits are still debated. We examined regional differences in signal-to-noise-ratios (SNRs) of cortical sources in MEG and EEG. Data from four subjects were used to simulate focal and extended sources located on the cortical surface reconstructed from high-resolution magnetic resonance images. The SNR maps for MEG and EEG were found to be complementary. The SNR of deep sources was larger in EEG than in MEG, whereas the opposite was typically the case for superficial sources. Overall, the SNR maps were more uniform for EEG than for MEG. When using a noise model based on uniformly distributed random sources on the cortex, the SNR in MEG was found to be underestimated, compared with the maps obtained with noise estimated from actual recorded MEG and EEG data. With extended sources, the total area of cortex in which the SNR was higher in EEG than in MEG was larger than with focal sources. Clinically, SNR maps in a patient explained differential sensitivity of MEG and EEG in detecting epileptic activity. Our results emphasize the benefits of recording MEG and EEG simultaneously.
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Affiliation(s)
- Daniel M Goldenholz
- Athinoula A. Martinos Center For Biomedical Imaging, Massachusetts General Hospital, Charlestown, USA.
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Westmijse I, Ossenblok P, Gunning B, van Luijtelaar G. Onset and propagation of spike and slow wave discharges in human absence epilepsy: A MEG study. Epilepsia 2009; 50:2538-48. [PMID: 19519798 DOI: 10.1111/j.1528-1167.2009.02162.x] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE A nonlinear association and a source localization technique were used to describe the onset and propagation of spike-and-slow-wave discharges (SWDs) in children with absence seizures. Previous studies have emphasized a leading cortical role in the generation of absence seizures in genetic epileptic rats. METHODS Synchronization between all magnetoencephalography (MEG) sensor-couples before and during SWDs in five patients was investigated over time. A source localization [beamformer, SAM(g(2))] technique was used to find brain regions associated with the origin of the spikes of the SWDs. RESULTS The onset of SWDs was characterized by high associations at left and right frontal regions. An alternating pattern of high synchronization was found during trains of SWDs: generalized during the wave and localized during the spike; the origin of the spike was different from the onset of SWDs, more frontal lateral and medial parietal. The localization of this latter region was confirmed with SAM(g(2)). DISCUSSION The outcome of the nonlinear association techniques demonstrated that SWDs have a local cortical onset, whereas the association and beamformer technique support a local or even a focal cortical involvement in the occurrence of the spike in a train of SWDs. In all, the cortex contains local frontal and parietal sites relevant before the onset of the generalized pattern of SWDs and other ones that might contain the driving force behind the spike in trains of 3-4 Hz SWDs.
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Affiliation(s)
- Inge Westmijse
- Donders Centre for Cognition, Radboud University Nijmegen, The Netherlands
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Interictal electromagnetic source imaging in focal epilepsy: practices, results and recommendations. Curr Opin Neurol 2008; 21:437-45. [DOI: 10.1097/wco.0b013e3283081e23] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Enatsu R, Mikuni N, Usui K, Matsubayashi J, Taki J, Begum T, Matsumoto R, Ikeda A, Nagamine T, Fukuyama H, Hashimoto N. Usefulness of MEG magnetometer for spike detection in patients with mesial temporal epileptic focus. Neuroimage 2008; 41:1206-19. [DOI: 10.1016/j.neuroimage.2008.03.038] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 03/09/2008] [Accepted: 03/26/2008] [Indexed: 11/16/2022] Open
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Gavaret M, Badier JM, Chauvel P. EEG haute résolution (EEG-HR) et magnétoencéphalographie (MEG). Neurochirurgie 2008; 54:185-90. [DOI: 10.1016/j.neuchi.2008.02.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2008] [Accepted: 02/13/2008] [Indexed: 11/29/2022]
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Perkins FF, Breier J, McManis MH, Castillo E, Wheless J, McGregor AL, Chacon M, Clarke DF. Benign rolandic epilepsy -- perhaps not so benign: use of magnetic source imaging as a predictor of outcome. J Child Neurol 2008; 23:389-93. [PMID: 18401032 DOI: 10.1177/0883073807309239] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The purpose of this study was to evaluate children with benign rolandic epilepsy, a childhood epilepsy characterized by centrotemporal/rolandic spike-wave discharges with infrequent partial seizures that may secondarily generalize. Recently, some investigators have questioned whether benign rolandic epilepsy is indeed "benign" or whether long-term cognitive outcome may be adversely affected. We initiated an ongoing study to identify children with benign rolandic epilepsy. The children were evaluated in the Texas Comprehensive Epilepsy Program using outpatient or continuous video-electroencephalographic monitoring, brain magnetic resonance imaging, magnetoencephalography, and neuropsychological testing. Neuropsychological testing revealed fine motor dysfunction, visuomotor integration deficits, dyscalculia, and/or expressive language deficits in all of the 9 patients evaluated, reaffirming that benign rolandic epilepsy is not necessarily a benign disorder. Our study shows a high concordance of motor and cognitive deficits in benign rolandic epilepsy, as others have previously suggested. Furthermore, magnetic source imaging shows a higher resolution of dipole localization compared with conventional electroencephalography, which may ultimately improve prediction of deficits. This reaffirms that magnetoencephalography is a valuable diagnostic tool in the evaluation of children with benign rolandic epilepsy.
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Affiliation(s)
- F Frederick Perkins
- Department of Pediatrics, Division of Child Neurology, University of Tennessee Health Science Center at Memphis/Le Bonheur Comprehensive Epilepsy Program, Memphis, TN 38105, USA.
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Schwartz ES, Dlugos DJ, Storm PB, Dell J, Magee R, Flynn TP, Zarnow DM, Zimmerman RA, Roberts TPL. Magnetoencephalography for pediatric epilepsy: how we do it. AJNR Am J Neuroradiol 2008; 29:832-7. [PMID: 18272549 DOI: 10.3174/ajnr.a1029] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Magnetoencephalography (MEG) is increasingly being used in the preoperative evaluation of pediatric patients with epilepsy. The ability to noninvasively localize ictal onset zones (IOZ) and their relationships to eloquent functional cortex allows the pediatric epilepsy team to more accurately assess the likelihood of postoperative seizure freedom, while more precisely prognosticating the potential functional deficits that may be expected from resective surgery. Confirmation of clinically suggested multifocality may result in a recommendation against resective surgery because the probability of seizure freedom will be low. Current paradigms for motor and somatosensory testing are robust. Paradigms allowing localization of those regions necessary for competent language function, though promising, are under continuous optimization. MR imaging white matter trajectory data, created from diffusion tensor imaging obtained in the same setting as the localization brain MR imaging, provide ancillary information regarding connectivity of the IOZ to sites of rapid secondary spread and the spatial relationship of the IOZ to functionally important white matter bundles, such as the corticospinal tracts. A collaborative effort between neuroradiology, neurology, neurosurgery, neuropsychology, technology, and physics ensures successful implementation of MEG within a pediatric epilepsy program.
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Affiliation(s)
- E S Schwartz
- Divisions of Neuroradiology, The Children's Hospital of Philadelphia, Philadelphia, PA, USA
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Optimized mismatch negativity paradigm reflects deficits in schizophrenia patients. Biol Psychol 2008; 77:205-16. [DOI: 10.1016/j.biopsycho.2007.10.009] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2007] [Revised: 10/10/2007] [Accepted: 10/10/2007] [Indexed: 11/21/2022]
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Ossenblok P, de Munck JC, Colon A, Drolsbach W, Boon P. Magnetoencephalography Is More Successful for Screening and Localizing Frontal Lobe Epilepsy than Electroencephalography. Epilepsia 2007; 48:2139-49. [PMID: 17662061 DOI: 10.1111/j.1528-1167.2007.01223.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE The diagnosis of frontal lobe epilepsy may be compounded by poor electroclinical localization, due to distributed or rapidly propagating epileptiform activity. This study aimed at developing optimal procedures for localizing interictal epileptiform discharges (IEDs) of patients with localization related epilepsy in the frontal lobe. To this end the localization results obtained for magnetoencephalography (MEG) and electroencephalography (EEG) were compared systematically using automated analysis procedures. METHODS Simultaneous recording of interictal EEG and MEG was successful for 18 out of the 24 patients studied. Visual inspection of these recordings revealed IEDs with varying morphology and topography. Cluster analysis was used to classify these discharges on the basis of their spatial distribution followed by equivalent dipole analysis of the cluster averages. The locations of the equivalent dipoles were compared with the location of the epileptogenic lesions of the patient or, if these were not visible at MRI with the location of the interictal onset zones identified by subdural electroencephalography. RESULTS Generally IEDs were more abundantly in MEG than in the EEG recordings. Furthermore, the duration of the MEG spikes, measured from the onset till the spike maximum, was in most patients shorter than the EEG spikes. In most patients, distinct spike subpopulations were found with clearly different topographical field maps. Cluster analysis of MEG spikes followed by dipole localization was successful (n = 14) for twice as many patients as for EEG source analysis (n = 7), indicating that the localizability of interictal MEG is much better than of interictal EEG. CONCLUSIONS The automated procedures developed in this study provide a fast screening method for identifying the distinct categories of spikes and the brain areas responsible for these spikes. The results show that MEG spike yield and localization is superior compared with EEG. This finding is of importance for the diagnosis and preoperative evaluation of patients with frontal lobe epilepsy.
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Shahin AJ, Roberts LE, Miller LM, McDonald KL, Alain C. Sensitivity of EEG and MEG to the N1 and P2 auditory evoked responses modulated by spectral complexity of sounds. Brain Topogr 2007; 20:55-61. [PMID: 17899352 PMCID: PMC4373076 DOI: 10.1007/s10548-007-0031-4] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/08/2007] [Indexed: 11/29/2022]
Abstract
Acoustic complexity of a stimulus has been shown to modulate the electromagnetic N1 (latency approximately 110 ms) and P2 (latency 190 ms) auditory evoked responses. We compared the relative sensitivity of electroencephalography (EEG) and magnetoencephalography (MEG) to these neural correlates of sensation. Simultaneous EEG and MEG were recorded while participants listened to three variants of a piano tone. The piano stimuli differed in their number of harmonics: the fundamental frequency (f ( 0 )), only, or f ( 0 ) and the first two or eight harmonics. The root mean square (RMS) of the amplitude of P2 but not N1 increased with spectral complexity of the piano tones in EEG and MEG. The RMS increase for P2 was more prominent in EEG than MEG, suggesting important radial sources contributing to the P2 only in EEG. Source analysis revealing contributions from radial and tangential sources was conducted to test this hypothesis. Source waveforms revealed a significant increase in the P2 radial source amplitude in EEG with increased spectral complexity of piano tones. The P2 of the tangential source waveforms also increased in amplitude with increased spectral complexity in EEG and MEG. The P2 auditory evoked response is thus represented by both tangential (gyri) and radial (sulci) activities. The radial contribution is expressed preferentially in EEG, highlighting the importance of combining EEG with MEG where complex source configurations are suspected.
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Affiliation(s)
- Antoine J Shahin
- UC Davis Center for Mind and Brain, University of California-Davis, 267 Cousteau Place, Davis, CA 95618, USA.
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Paulini A, Fischer M, Rampp S, Scheler G, Hopfengärtner R, Kaltenhäuser M, Dörfler A, Buchfelder M, Stefan H. Lobar localization information in epilepsy patients: MEG—A useful tool in routine presurgical diagnosis. Epilepsy Res 2007; 76:124-30. [PMID: 17719204 DOI: 10.1016/j.eplepsyres.2007.07.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Revised: 05/25/2007] [Accepted: 07/14/2007] [Indexed: 11/26/2022]
Abstract
Epilepsy surgery is an established therapy for pharmacoresistant focal epilepsy. This study investigated the contribution of routinely used magnetoencepahlography (MEG) in addition to long term video-EEG-monitoring in presurgical evaluation. The distribution of localization results to anatomical lobes was compared with special focus to MEG spike localization results in cases without or with ambiguous EEG findings. A total of 105 consecutive patients with intractable focal epilepsy and epilepsy surgery after investigation by video-EEG-monitoring and MEG were included. The percentages of monolobar results were analysed and compared, especially with respect to the resection lobe. Postoperative outcome was used for further validation. No spikes were recorded on MEG in 30% (32 of 105). In cases with a diagnostic finding by the respective method, MEG localized in 82% (60 of 73 patients) within one anatomical lobe. Ictal EEG localized within one lobe in 72% (66 of 92 patients), interictal EEG in 60% (59 of 98 patients). In 25 of 105 patients (24%) no clear localization within one lobe was found either in interictal or in ictal EEG. In 11 of these cases MEG localized within the resection lobe. Six patients of these became seizure free, the other five had at least 50% reduction of their seizure rate 1 year after surgery. In summary MEG is a useful tool in the routine workup for epilepsy surgery contributing information to focus hypothesis in addition to video-EEG.
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Affiliation(s)
- Andrea Paulini
- Epilepsy Center (ZEE), Department of Neurology, University of Erlangen-Nürnberg, Erlangen, Germany.
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