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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: 11] [Impact Index Per Article: 3.7] [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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Tripathi M, Kaur K, Ramanujam B, Viswanathan V, Bharti K, Singh G, Singh V, Garg A, Bal CS, Tripathi M, Sharma MC, Pandey R, Dash D, Mandal P, Chandra PS. Diagnostic added value of interictal magnetic source imaging in presurgical evaluation of persons with epilepsy: A prospective blinded study. Eur J Neurol 2021; 28:2940-2951. [PMID: 34124810 DOI: 10.1111/ene.14935] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/27/2021] [Accepted: 05/06/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE In presurgical evaluation for epilepsy surgery, information is sourced from various imaging modalities to accurately localize the epileptogenic zone. Magnetoencephalography (MEG) is a newer noninvasive technique for localization. However, there is limited literature to evaluate if MEG provides additional advantage over the conventional imaging modalities in clinical decision making. The objective of this study was to assess the diagnostic added value of MEG in decision making before epilepsy surgery. METHOD This was a prospective observational study. Patients underwent 3 h of recording in a MEG scanner, and the resulting localizations were compared with other complimentary investigations. Added value of MEG (considered separately from high-density electroencephalography) was defined as the frequency of cases in which (i) the information provided by magnetic source imaging (MSI) avoided implantation of intracranial electrodes and the patient was directly cleared for surgery, and (ii) MSI indicated additional substrates for implantation of intracranial electrodes. Postoperative seizure freedom was used as the diagnostic reference by which to measure the localizing accuracy of MSI. RESULTS A total of 102 patients underwent epilepsy surgery. MEG provided nonredundant information, which contributed to deciding the course of surgery in 33% of the patients, and prevented intracranial recordings in 19%. A total of 76% of the patients underwent surgical resection in sublobes concordant with MSI localization, and the diagnostic odds ratio for good (Engel I) outcome in these patients was 2.3 (95% confidence interval 0.68, 7.86; p = 0.183) after long-term follow-up of 36 months. CONCLUSION Magnetic source imaging yields additional useful information which can significantly alter as well as improve the surgical strategy for persons with epilepsy.
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Affiliation(s)
- Manjari Tripathi
- Neurology, All India Institute of Medical Sciences, New Delhi, India
| | - Kirandeep Kaur
- Neurology, All India Institute of Medical Sciences, New Delhi, India.,MEG Facility, National Brain Research Institute, Manesar, India
| | | | - Vibhin Viswanathan
- Neurosurgery, All India Institute of Medical Sciences, New Delhi, India.,MEG Resource Facility, Collaborative Project Between AIIMS & NBRC, National Brain Research Center, Manesar, India
| | - Kamal Bharti
- MEG Resource Facility, Collaborative Project Between AIIMS & NBRC, National Brain Research Center, Manesar, India
| | - Gaurav Singh
- MEG Resource Facility, Collaborative Project Between AIIMS & NBRC, National Brain Research Center, Manesar, India
| | - Vivek Singh
- MEG Resource Facility, Collaborative Project Between AIIMS & NBRC, National Brain Research Center, Manesar, India
| | - Ajay Garg
- Neuroradiology, All India Institute of Medical Sciences, New Delhi, India
| | - Chandra Sekhar Bal
- Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India
| | - Madhavi Tripathi
- Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India
| | | | - Ravindra Pandey
- Biostatistics, All India Institute of Medical Sciences, New Delhi, India
| | - Deepa Dash
- Neurology, All India Institute of Medical Sciences, New Delhi, India
| | - Pravat Mandal
- MEG Resource Facility, Collaborative Project Between AIIMS & NBRC, National Brain Research Center, Manesar, India
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Otsubo H, Ogawa H, Pang E, Wong SM, Ibrahim GM, Widjaja E. A review of magnetoencephalography use in pediatric epilepsy: an update on best practice. Expert Rev Neurother 2021; 21:1225-1240. [PMID: 33780318 DOI: 10.1080/14737175.2021.1910024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Introduction: Magnetoencephalography (MEG) is a noninvasive technique that is used for presurgical evaluation of children with drug-resistant epilepsy (DRE).Areas covered: The contributions of MEG for localizing the epileptogenic zone are discussed, in particular in extra-temporal lobe epilepsy and focal cortical dysplasia, which are common in children, as well as in difficult to localize epilepsy such as operculo-insular epilepsy. Further, the authors review current evidence on MEG for mapping eloquent cortex, its performance, application in clinical practice, and potential challenges.Expert opinion: MEG could change the clinical management of children with DRE by directing placement of intracranial electrodes thereby enhancing their yield. With improved identification of a circumscribed epileptogenic zone, MEG could render more patients as suitable candidates for epilepsy surgery and increase utilization of surgery.
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Affiliation(s)
- Hiroshi Otsubo
- Diagnostic Imaging, Hospital for Sick Children, Toronto, Canada
| | - Hiroshi Ogawa
- Diagnostic Imaging, Hospital for Sick Children, Toronto, Canada
| | - Elizabeth Pang
- Diagnostic Imaging, Hospital for Sick Children, Toronto, Canada.,Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Canada
| | - Simeon M Wong
- Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Canada
| | - George M Ibrahim
- Division of Neurosurgery, Hospital for Sick Children, Toronto, Canada.,Diagnostic Imaging, Hospital for Sick Children, Toronto, Canada
| | - Elysa Widjaja
- Diagnostic Imaging, Hospital for Sick Children, Toronto, Canada.,Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Canada.,Diagnostic Imaging, Hospital for Sick Children, Toronto, Canada
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Kuzan-Fischer CM, Parker WE, Schwartz TH, Hoffman CE. Challenges of Epilepsy Surgery. World Neurosurg 2020; 139:762-774. [PMID: 32689697 DOI: 10.1016/j.wneu.2020.03.032] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 03/02/2020] [Indexed: 12/22/2022]
Abstract
Though frequently effective in the management of medically refractory seizures, epilepsy surgery presents numerous challenges. Selection of the appropriate candidate patients who are likely to benefit from surgery is critical to achieving seizure freedom and avoiding neurocognitive morbidity. Identifying the seizure focus and mapping epileptogenic networks involves an interdisciplinary team dedicated to formulating a safe and effective surgical plan. Various strategies can be employed either to eliminate the epileptic focus or to modulate network activity, including resection of the focus with open surgery or laser interstitial thermal therapy; modulation of epileptogenic firing patterns with responsive neurostimulation, deep brain stimulation, or vagus nerve stimulation; or non-invasive disconnection of epileptic circuits with focused ultrasound, which is also discussed in greater detail in the subsequent chapter in our series. We review several challenges of epilepsy surgery that must be thoughtfully addressed in order to ensure its success.
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Affiliation(s)
- Claudia M Kuzan-Fischer
- Department of Neurological Surgery, Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, New York, USA
| | - Whitney E Parker
- Department of Neurological Surgery, Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, New York, USA
| | - Theodore H Schwartz
- Department of Neurological Surgery, Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, New York, USA
| | - Caitlin E Hoffman
- Department of Neurological Surgery, Weill Cornell Medical College, NewYork-Presbyterian Hospital, New York, New York, USA.
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Abstract
Magnetoencephalography is the noninvasive measurement of miniscule magnetic fields produced by brain electrical currents, and is used most fruitfully to evaluate epilepsy patients. While other modalities infer brain function indirectly by measuring changes in blood flow, metabolism, and oxygenation, magnetoencephalography measures neuronal and synaptic function directly with submillisecond temporal resolution. The brain's magnetic field is recorded by neuromagnetometers surrounding the head in a helmet-shaped sensor array. Because magnetic signals are not distorted by anatomy, magnetoencephalography allows for a more accurate measurement and localization of brain activities than electroencephalography. Magnetoencephalography has become an indispensable part of the armamentarium at epilepsy centers.
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Affiliation(s)
- Richard C Burgess
- Epilepsy Center, Neurological Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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6
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Gao R, Yu T, Xu C, Zhang X, Yan X, Ni D, Zhang X, Ma K, Qiao L, Zhu J, Wang X, Ren Z, Zhang X, Zhang G, Li Y. The value of magnetoencephalography for stereo-EEG-guided radiofrequency thermocoagulation in MRI-negative epilepsy. Epilepsy Res 2020; 163:106322. [PMID: 32278277 DOI: 10.1016/j.eplepsyres.2020.106322] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 02/24/2020] [Accepted: 03/19/2020] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Magnetoencephalography (MEG) is valuable for guiding resective surgery in patients with epilepsy. However, its value for minimally invasive treatment is still unknown. This study aims to evaluate the value of MEG for stereo-electroencephalogram (EEG)-guided radiofrequency thermocoagulation (SEEG-guided RF-TC) in magnetic resonance imaging (MRI)-negative epilepsies. METHODS An observational cohort study was performed and 19 MRI-negative patients who underwent SEEG-guided RF-TC in our epilepsy center were included. In addition, 16 MRI-positive patients were included as a reference group. Semiology, electrophysiology, and imaging information were collected. To evaluate the value of locating the MEG cluster, the proportion of the RF-TC contacts located in the MEG cluster out of all contacts used to perform RF-TC in each patient was calculated. All patients underwent the standard SEEG-guided RF-TC procedure and were followed up after the treatment. RESULTS Nineteen MRI-negative patients were divided into two groups based on the existence of MEG clusters; 10 patients with MEG clusters were in group I and nine patients without any MEG cluster were in group II. No significant difference was observed in terms of age, sex, type of seizures, or number of SEEG electrodes implanted. The median of the proportion of contacts in the MEG cluster was 77.0 % (IQR 57.7-100.0 %). The follow-up results showed that the probability of being seizure-free at one year after RFTC in MRI-negative patients with an MEG cluster was 30.0 % (95 % CI 11.6-77.3 %), significantly (p = 0.014) higher than that in patients without an MEG cluster; there was no significant difference when compared with MRI-positive patients. CONCLUSION This is the first study to evaluate the value of MEG in SEEG-guided RF-TC in MRI-negative epilepsies. MEG is a useful supplement for patients with MRI-negative epilepsy. MEG can be applied in minimally invasive treatment. MEG clusters can help identify better candidates and provide a valuable target for SEEG-guided RF-TC, which leads to better outcomes.
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Affiliation(s)
- Runshi Gao
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Tao Yu
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Cuiping Xu
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xiating Zhang
- Department of Neurology, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xiaoming Yan
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Duanyu Ni
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xiaohua Zhang
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Kai Ma
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Liang Qiao
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Jin Zhu
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xueyuan Wang
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Zhiwei Ren
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Xi Zhang
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Guojun Zhang
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China
| | - Yongjie Li
- Beijing Institute of Functional Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China.
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Hirata S, Morino M, Nakae S, Matsumoto T. Surgical Technique and Outcome of Extensive Frontal Lobectomy for Treatment of Intracable Non-lesional Frontal Lobe Epilepsy. Neurol Med Chir (Tokyo) 2020; 60:17-25. [PMID: 31801933 PMCID: PMC6970070 DOI: 10.2176/nmc.oa.2018-0286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Although extensive frontal lobectomy (eFL) is a common surgical procedure for intractable frontal lobe epilepsy (FLE), there have been very few reports regarding surgical techniques for eFL. This article provides step-by-step descriptions of our surgical technique for non-lesional FLE. Sixteen patients undergoing eFL were included in this study. The goals were to maximize gray matter removal, including the orbital gyrus and subcallosal area, and to spare the primary motor and premotor cortexes and anterior perforated substance. The eFL consists of three steps: (1) positioning, craniotomy, and exposure; (2) lateral frontal lobe resection; and (3), resection of the rectus gyrus and orbital gyrus. Resection ahead of bregma allows preservation of motor and premotor area function. To remove the orbital gyrus preserving anterior perforated substance, it is essential to visualize the olfactory trigone beneath the pia. It is important to observe the surface of the contralateral medial frontal lobe for complete removal of the subcallosal area of the frontal lobe. Thirteen patients (81.25%) became seizure-free and three patients (18.75%) continued to have seizures. None of the patients showed any complications. The eFL is a good surgical technique for the treatment of intractable non-lesional FLE. For treatment of epilepsy by eFL, it is important to resect the non-eloquent area of the frontal lobe as much as possible with preservation of the eloquent cortex.
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Burgess RC. Magnetoencephalography for localizing and characterizing the epileptic focus. HANDBOOK OF CLINICAL NEUROLOGY 2019; 160:203-214. [PMID: 31277848 DOI: 10.1016/b978-0-444-64032-1.00013-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Magnetoencephalography (MEG) is the noninvasive measurement of the miniscule magnetic fields produced by electrical currents flowing in the brain-the same neuroelectric activity that produces the EEG. MEG is one of several diagnostic tests employed in the evaluation of patients with epilepsy, but without the need to expose the patient to any potentially harmful agents. MEG is especially important in those being considered for epilepsy surgery, in whom accurate localization of the epileptic focus is paramount. While other modalities infer brain function indirectly by measuring changes in blood flow, metabolism, oxygenation, etc., MEG, as well as EEG, measures neuronal and synaptic function directly and, like EEG, MEG enjoys submillisecond temporal resolution. The measurement of magnetic fields provides information not only about the amplitude of the current but also its orientation. MEG picks up the magnetic field from neuromagnetometers surrounding the head in a helmet-shaped array of sensors. Clinical whole-head systems currently have 200-300 magnetic sensors, thereby offering very high resolution. The magnetic signals are not distorted by anatomy, because magnetic susceptibility is the same for all tissues, including the skull. Hence, MEG allows for a more accurate measurement and localization of brain activities than does EEG. Because one of its primary strengths is the ability to precisely localize electromagnetic activity within brain areas, MEG results are always coregistered to the patient's MRI. When combined in this way with structural imaging, it has been called magnetic source imaging (MSI), but MEG is properly understood as a clinical neurophysiologic diagnostic test. Signal processing and clinical interpretation in magnetoencephalography require sophisticated noise reduction and computerized mathematical modeling. Technological advances in these areas have brought MEG to the point where it is now part of routine clinical practice. MEG has become an indispensable part of the armamentarium at epilepsy centers where MEG laboratories are located, especially when patients are MRI-negative or where results of other structural and functional tests are not entirely concordant.
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Affiliation(s)
- Richard C Burgess
- Department of Neurology, Cleveland Clinic Foundation, Cleveland, OH, United States.
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9
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Magnetoencephalography and ictal SPECT in patients with failed epilepsy surgery. Clin Neurophysiol 2018; 129:1651-1657. [DOI: 10.1016/j.clinph.2018.05.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 04/30/2018] [Accepted: 05/03/2018] [Indexed: 11/17/2022]
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Mohamed IS, Bouthillier A, Bérubé A, Cossette P, Finet P, Saint-Hilaire JM, Robert M, Nguyen DK. The clinical impact of integration of magnetoencephalography in the presurgical workup for refractory nonlesional epilepsy. Epilepsy Behav 2018; 79:34-41. [PMID: 29253675 DOI: 10.1016/j.yebeh.2017.10.036] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Revised: 10/11/2017] [Accepted: 10/27/2017] [Indexed: 11/28/2022]
Abstract
OBJECTIVE For patients with nonlesional refractory focal epilepsy (NLRFE), localization of the epileptogenic zone is more arduous, and intracranial electroencephalography (EEG) (icEEG) is frequently required. Planning for icEEG is dependent on combined data from multiple noninvasive modalities. We report the negative impact of lack of integration of magnetoencephalography (MEG) in the presurgical workup in NLRFE. METHODS Observational MEG case series involving 31 consecutive patients with NLRFE in an academic epilepsy center. For various reasons, MEG data were not analyzed in a timely manner to be included in the decision-making process. The presumed impact of MEG was assessed retrospectively. RESULTS Magnetoencephalography would have changed the initial management in 21/31 (68%) had MEG results been available by reducing the number of intracranial electrodes, modifying their position, allowing for direct surgery, canceling the intracranial study, or providing enough evidence to justify one. Good surgical outcome was achieved in 11 out of 17 patients who proceeded to epilepsy surgery. Nine out of eleven had MEG clusters corresponding to the resection area, and MEG findings would have allowed for direct surgery (avoiding icEEG) in 2/11. Six patients had poor outcome including three patients where MEG would have significantly changed the outcome by modifying the resection margin. Magnetoencephalography provided superior information in 3 patients where inadequate coverage precluded accurate mapping of the epileptogenic zone. CONCLUSION In this single center retrospective study, MEG would have changed patient management, icEEG planning, and surgical outcome in a significant percentage of patients with NLRFE and should be considered in the presurgical workup in those patients.
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Affiliation(s)
- Ismail S Mohamed
- IWK Health Center, Department of Pediatrics, Division of Neurology, Halifax, Canada; University of Alabama, Department of Pediatrics, Division of Neurology, Birmingham, AL, USA
| | - Alain Bouthillier
- Division of Neurosurgery, Notre-Dame Hospital (CHUM), University of Montreal, Canada
| | - Arline Bérubé
- Division of Neurology, Notre-Dame Hospital (CHUM), University of Montréal, Canada
| | - Patrick Cossette
- Division of Neurology, Notre-Dame Hospital (CHUM), University of Montréal, Canada
| | - Patrice Finet
- Division of Neurosurgery, Notre-Dame Hospital (CHUM), University of Montreal, Canada
| | | | - Manon Robert
- Neuropsychology and Cognition Research Center, Psychology Department, University of Montreal, Canada
| | - Dang Khoa Nguyen
- Division of Neurology, Notre-Dame Hospital (CHUM), University of Montréal, Canada.
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Velmurugan J, Nagarajan SS, Mariyappa N, Ravi SG, Thennarasu K, Mundlamuri RC, Raghavendra K, Bharath RD, Saini J, Arivazhagan A, Rajan J, Mahadevan A, Rao MB, Satishchandra P, Sinha S. Magnetoencephalographic imaging of ictal high-frequency oscillations (80-200 Hz) in pharmacologically resistant focal epilepsy. Epilepsia 2017; 59:190-202. [PMID: 29111591 DOI: 10.1111/epi.13940] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/07/2017] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Specificity of ictal high-frequency oscillations (HFOs) in identifying epileptogenic abnormality is significant, compared to the spikes and interictal HFOs. The objectives of the study were to detect and to localize ictal HFOs by magnetoencephalography (MEG) for identifying the seizure onset zone (SOZ), evaluate the cortical excitability from preictal to ictal transition, and establish HFO concordance rates with other modalities and postsurgical resection. METHODS Sixty-seven patients with drug-resistant epilepsy had at least 1 spontaneous seizure each during MEG acquisition, and analysis was carried out on 20 seizures from 20 patients. Ictal MEG data were bandpass filtered (80-200 Hz) to visualize, review, and analyze the HFOs co-occurring with ictal spikes. Source montages were generated on both hemispheres, mean fast Fourier transform was computed on virtual time series for determining the preictal to ictal spectral power transition, and source reconstruction was performed with sLORETA and beamformers. The concordance rates of ictal MEG HFOs (SOZ) was estimated with 4 reference epileptogenic regions. RESULTS In each subject, transient bursts of high-frequency oscillatory cycles, distinct from the background activity, were observed in the periictal continuum. Time-frequency analysis showed significant spectral power surge (85-160 Hz) during ictal state (P < .05) compared to preictal state, but there was no variation in the peak HFO frequencies (P > .05) for each subgroup and at each source montage. HFO source localization was consistent between algorithms (k = 0.857 ± 0.138), with presumed epileptogenic zone (EZ) comparable to other modalities. In patients who underwent surgery (n = 6), MEG HFO SOZ was concordant with the presumed EZ and the surgical resection site (100%), and all were seizure-free during follow-up. SIGNIFICANCE HFOs could be detected in the MEG periictal state, and its sources were accurately localized. During preictal to ictal transition, HFOs exhibited dynamic augmentation in intrinsic epileptogenicity. Spatial overlap of ictal HFO sources was consistent with EZ determinants and the surgical resection area.
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Affiliation(s)
- Jayabal Velmurugan
- Department of Clinical Neurosciences, National Institute of Mental Health and Neurosciences, Bangalore, India.,MEG Research Center, National Institute of Mental Health and Neurosciences, Bangalore, India.,Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore, India.,Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - Srikantan S Nagarajan
- Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA
| | - Narayanan Mariyappa
- MEG Research Center, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Shankar G Ravi
- Department of Biostatistics, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Kandavel Thennarasu
- Department of Biostatistics, National Institute of Mental Health and Neurosciences, Bangalore, India
| | | | - Kenchaiah Raghavendra
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Rose Dawn Bharath
- Department of Neuroimaging & interventional radiology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Jitender Saini
- Department of Neuroimaging & interventional radiology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | | | - Jamuna Rajan
- Department of Clinical Psychology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Anita Mahadevan
- Department of Neuropathology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Malla B Rao
- Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Parthasarathy Satishchandra
- MEG Research Center, National Institute of Mental Health and Neurosciences, Bangalore, India.,Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore, India
| | - Sanjib Sinha
- MEG Research Center, National Institute of Mental Health and Neurosciences, Bangalore, India.,Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore, India
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Muthaffar O, Puka K, Rubinger L, Go C, Snead OC, Rutka JT, Widjaja E. Reoperation after failed resective epilepsy surgery in children. J Neurosurg Pediatr 2017; 20:134-140. [PMID: 28574317 DOI: 10.3171/2017.3.peds16722] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECTIVE Although epilepsy surgery is an effective treatment option, at least 20%-40% of patients can continue to experience uncontrolled seizures resulting from incomplete resection of the lesion, epileptogenic zone, or secondary epileptogenesis. Reoperation could eliminate or improve seizures. Authors of this study evaluated outcomes following reoperation in a pediatric population. METHODS A retrospective single-center analysis of all patients who had undergone resective epilepsy surgery in the period from 2001 to 2013 was performed. After excluding children who had repeat hemispherotomy, there were 24 children who had undergone a second surgery and 2 children who had undergone a third surgery. All patients underwent MRI and video electroencephalography (VEEG) and 21 underwent magnetoencephalography (MEG) prior to reoperation. RESULTS The mean age at the first and second surgery was 7.66 (SD 4.11) and 10.67 (SD 4.02) years, respectively. The time between operations ranged from 0.03 to 9 years. At reoperation, 8 patients underwent extended cortical resection; 8, lobectomy; 5, lesionectomy; and 3, functional hemispherotomy. One year after reoperation, 58% of the children were completely seizure free (International League Against Epilepsy [ILAE] Class 1) and 75% had a reduction in seizures (ILAE Classes 1-4). Patients with MEG clustered dipoles were more likely to be seizure free than to have persistent seizures (71% vs 40%, p = 0.08). CONCLUSIONS Reoperation in children with recurrent seizures after the first epilepsy surgery could result in favorable seizure outcomes. Those with residual lesion after the first surgery should undergo complete resection of the lesion to improve seizure outcome. In addition to MRI and VEEG, MEG should be considered as part of the reevaluation prior to reoperation.
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Affiliation(s)
- Osama Muthaffar
- Division of Neurology.,Division of Pediatrics, King Abdulaziz University Hospital, Jeddah, Saudi Arabia
| | | | - Luc Rubinger
- Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada; and
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El Tahry R, Wang IZ. Failed epilepsy surgery: is this the end? Acta Neurol Belg 2017; 117:433-440. [PMID: 28303525 DOI: 10.1007/s13760-017-0769-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 03/07/2017] [Indexed: 12/14/2022]
Abstract
Resective epilepsy surgery can lead to sustained seizure control in 70-80% of patients evaluated for epilepsy surgery, indicating that up to 30% of patients still have recurrent seizures after surgery. Definitions of failed epilepsy surgery vary amongst studies. This review focuses on seizure outcome predictors after reoperation, possible mechanisms of failure and best management for this difficult patient population.
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Affiliation(s)
- Riëm El Tahry
- Department of Neurology, Center for Refractory Epilepsy, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Av. Hippocrate 10, 1200, Brussels, Belgium.
- Department of Pneumology, Sleep Laboratory, Cliniques Universitaires Saint Luc, Université Catholique de Louvain, Av Hippocrate 10, 1200, Brussels, Belgium.
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Schönherr M, Stefan H, Hamer HM, Rössler K, Buchfelder M, Rampp S. The delta between postoperative seizure freedom and persistence: Automatically detected focal slow waves after epilepsy surgery. Neuroimage Clin 2016; 13:256-263. [PMID: 28018852 PMCID: PMC5167245 DOI: 10.1016/j.nicl.2016.12.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 11/03/2016] [Accepted: 12/01/2016] [Indexed: 11/09/2022]
Abstract
OBJECTIVE In this study, we use a novel automated method for localization and quantitative comparison of magnetoencephalographic (MEG) delta activity in patients with and without recurrent seizures after epilepsy surgery as well as healthy controls. METHODS We identified the generators of delta activity by source location in frequency domain between 1 and 4 Hz in spontaneous MEG data. Comparison with healthy control subjects by z-transform emphasized relative changes of activation in patients. The individual results were compared to spike localizations and statistical group analysis was performed. Additionally, MEG results were compared to 1-4 Hz activity in invasive EEG (iEEG) in two patients, in whom this data was available. RESULTS Patients with recurrent seizures exhibited significantly increased focal MEG delta activity both in comparison to healthy controls and seizure free patients. This slow activity showed a correlation to interictal epileptic activity and was not explained by consequences of the resection alone. In two patients with iEEG, iEEG analysis was concordant with the MEG findings. SIGNIFICANCE The quantity of delta activity could be used as a diagnostic marker for recurrent seizures. The close relation to epileptic spike localizations and the resection volume of patients with successful second surgery imply involvement in seizure recurrence. This initial evidence suggests a potential application in the planning of second epilepsy surgery.
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Affiliation(s)
- Margit Schönherr
- Epilepsy Center, Department of Neurology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Hermann Stefan
- Epilepsy Center, Department of Neurology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Hajo M. Hamer
- Epilepsy Center, Department of Neurology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Karl Rössler
- Department of Neurosurgery, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Michael Buchfelder
- Department of Neurosurgery, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
| | - Stefan Rampp
- Department of Neurosurgery, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen, Germany
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Englot DJ, Nagarajan SS, Imber BS, Raygor KP, Honma SM, Mizuiri D, Mantle M, Knowlton RC, Kirsch HE, Chang EF. Epileptogenic zone localization using magnetoencephalography predicts seizure freedom in epilepsy surgery. Epilepsia 2015; 56:949-58. [PMID: 25921215 DOI: 10.1111/epi.13002] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/18/2015] [Indexed: 12/01/2022]
Abstract
OBJECTIVE The efficacy of epilepsy surgery depends critically upon successful localization of the epileptogenic zone. Magnetoencephalography (MEG) enables noninvasive detection of interictal spike activity in epilepsy, which can then be localized in three dimensions using magnetic source imaging (MSI) techniques. However, the clinical value of MEG in the presurgical epilepsy evaluation is not fully understood, as studies to date are limited by either a lack of long-term seizure outcomes or small sample size. METHODS We performed a retrospective cohort study of patients with focal epilepsy who received MEG for interictal spike mapping followed by surgical resection at our institution. RESULTS We studied 132 surgical patients, with mean postoperative follow-up of 3.6 years (minimum 1 year). Dipole source modeling was successful in 103 patients (78%), whereas no interictal spikes were seen in others. Among patients with successful dipole modeling, MEG findings were concordant with and specific to the following: (1) the region of resection in 66% of patients, (2) invasive electrocorticography (ECoG) findings in 67% of individuals, and (3) the magnetic resonance imaging (MRI) abnormality in 74% of cases. MEG showed discordant lateralization in ~5% of cases. After surgery, 70% of all patients achieved seizure freedom (Engel class I outcome). Whereas 85% of patients with concordant and specific MEG findings became seizure-free, this outcome was achieved by only 37% of individuals with MEG findings that were nonspecific to or discordant with the region of resection (χ(2) = 26.4, p < 0.001). MEG reliability was comparable in patients with or without localized scalp electroencephalography (EEG), and overall, localizing MEG findings predicted seizure freedom with an odds ratio of 5.11 (95% confidence interval [CI] 2.23-11.8). SIGNIFICANCE MEG is a valuable tool for noninvasive interictal spike mapping in epilepsy surgery, including patients with nonlocalized findings receiving long-term EEG monitoring, and localization of the epileptogenic zone using MEG is associated with improved seizure outcomes.
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Affiliation(s)
- Dario J Englot
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, U.S.A.,Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A
| | - Srikantan S Nagarajan
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A
| | - Brandon S Imber
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, U.S.A
| | - Kunal P Raygor
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, U.S.A
| | - Susanne M Honma
- Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A
| | - Danielle Mizuiri
- Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A
| | - Mary Mantle
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A
| | - Robert C Knowlton
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A.,Department of Neurology, University of California, San Francisco, San Francisco, California, U.S.A
| | - Heidi E Kirsch
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A.,Department of Neurology, University of California, San Francisco, San Francisco, California, U.S.A
| | - Edward F Chang
- UCSF Comprehensive Epilepsy Center, University of California, San Francisco, San Francisco, California, U.S.A.,Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, U.S.A.,Biomagnetic Imaging Lab, Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California, U.S.A
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Albert GW, Ibrahim GM, Otsubo H, Ochi A, Go CY, Snead OC, Drake JM, Rutka JT. Magnetoencephalography-guided resection of epileptogenic foci in children. J Neurosurg Pediatr 2014; 14:532-7. [PMID: 25238627 DOI: 10.3171/2014.8.peds13640] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Resective surgery is increasingly used in the management of pediatric epilepsy. Frequently, invasive monitoring with subdural electrodes is required to adequately map the epileptogenic focus. The risks of invasive monitoring include the need for 2 operations, infection, and CSF leak. The aim of this study was to evaluate the feasibility and outcomes of resective epilepsy surgery guided by magnetoencephalography (MEG) in children who would have otherwise been candidates for electrode implantation. METHODS The authors reviewed the records of patients undergoing resective epilepsy surgery at the Hospital for Sick Children between 2001 and 2010. They identified cases in which resections were based on MEG data and no intracranial recordings were performed. Each patient's chart was reviewed for presentation, MRI findings, MEG findings, surgical procedure, pathology, and surgical outcome. RESULTS Sixteen patients qualified for the study. All patients had localized spike clusters on MEG and most had abnormal findings on MRI. Resection was carried out in each case based on the MEG data linked to neuronavigation and supplemented with intraoperative neuromonitoring. Overall, 62.5% of patients were seizure free following surgery, and 20% of patients experienced an improvement in seizures without attaining seizure freedom. In 2 cases, additional surgery was performed subsequently with intracranial monitoring in attempts to obtain seizure control. CONCLUSIONS MEG is a viable alternative to invasive monitoring with intracranial electrodes for planning of resective surgery in carefully selected pediatric patients with localization-related epilepsy. Good candidates for this approach include patients who have a well-delineated, localized spike cluster on MEG that is concordant with findings of other preoperative evaluations and patients with prior brain pathologies that make the implantation of subdural and depth electrodes somewhat problematic.
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Bennett-Back O, Ochi A, Widjaja E, Nambu S, Kamiya A, Go C, Chuang S, Rutka JT, Drake J, Snead OC, Otsubo H. Magnetoencephalography helps delineate the extent of the epileptogenic zone for surgical planning in children with intractable epilepsy due to porencephalic cyst/encephalomalacia. J Neurosurg Pediatr 2014; 14:271-8. [PMID: 25014323 DOI: 10.3171/2014.6.peds13415] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Porencephalic cyst/encephalomalacia (PC/E) is a brain lesion caused by ischemic insult or hemorrhage. The authors evaluated magnetoencephalography (MEG) spike sources (MEGSS) to localize the epileptogenic zone in children with intractable epilepsy secondary to PC/E. METHODS The authors retrospectively studied 13 children with intractable epilepsy secondary to PC/E (5 girls and 8 boys, age range 1.8-15 years), who underwent prolonged scalp video-electroencephalography (EEG), MRI, and MEG. Interictal MEGSS locations were compared with the ictal and interictal zones as determined from scalp video-EEG. RESULTS Magnetic resonance imaging showed PC/E in extratemporal lobes in 3 patients, within the temporal lobe in 2 patients, and in both temporal and extratemporal lobes in 8 patients. Magnetoencephalographic spike sources were asymmetrically clustered at the margin of PC/E in all 13 patients. One cluster of MEGSS was observed in 11 patients, 2 clusters in 1 patient, and 3 clusters in 1 patient. Ictal EEG discharges were lateralized and concordant with MEGSS in 8 patients (62%). Interictal EEG discharges were lateralized and concordant with MEGSS hemisphere in 9 patients (69%). Seven patients underwent lesionectomy in addition to MEGSS clusterectomy with (2 patients) and without (5 patients) intracranial video-EEG. Temporal lobectomy was performed in 1 patient and hemispherectomy in another. Eight of 9 patients achieved seizure freedom following surgery. CONCLUSIONS Magnetoencephalography delineated the extent of the epileptogenic zone adjacent to PC/E in patients with intractable epilepsy. Complete resection of the MEGSS cluster along with PC/E can provide favorable seizure outcomes.
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Mu J, Rampp S, Carrette E, Roessler K, Sommer B, Schmitt FC, De Tiège X, Hamer H, Boon P, Pauli E, Bluemcke I, Zhou D, Buchfelder M, Stefan H. Clinical relevance of source location in frontal lobe epilepsy and prediction of postoperative long-term outcome. Seizure 2014; 23:553-9. [DOI: 10.1016/j.seizure.2014.04.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 03/04/2014] [Accepted: 04/10/2014] [Indexed: 11/26/2022] Open
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Mohamed IS, Gibbs SA, Robert M, Bouthillier A, Leroux JM, Khoa Nguyen D. The utility of magnetoencephalography in the presurgical evaluation of refractory insular epilepsy. Epilepsia 2013; 54:1950-9. [DOI: 10.1111/epi.12376] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/13/2013] [Indexed: 11/28/2022]
Affiliation(s)
- Ismail S. Mohamed
- Division of Neurology; Department of Pediatrics; IIWK Health Center; Halifax NS Canada
| | - Steve A. Gibbs
- Division of Neurology; Notre-Dame Hospital (CHUM); University of Montreal; Montreal QC Canada
| | - Manon Robert
- Department of Psychology; Neuropsychology and Cognition Research Center; University of Montreal, Montreal; QC Canada
| | - Alain Bouthillier
- Division of Neurosurgery; Notre-Dame Hospital (CHUM); University of Montreal, Montreal; QC Canada
| | - Jean-Maxime Leroux
- Department of Radiology; Notre-Dame Hospital (CHUM); University of Montreal, Montreal; QC Canada
| | - Dang Khoa Nguyen
- Division of Neurology; Notre-Dame Hospital (CHUM); University of Montreal; Montreal QC Canada
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Vadera S, Jehi L, Burgess RC, Shea K, Alexopoulos AV, Mosher J, Gonzalez-Martinez J, Bingaman W. Correlation between magnetoencephalography-based “clusterectomy” and postoperative seizure freedom. Neurosurg Focus 2013; 34:E9. [DOI: 10.3171/2013.4.focus1357] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
During the presurgical evaluation of patients with medically intractable focal epilepsy, a variety of noninvasive studies are performed to localize the hypothetical epileptogenic zone and guide the resection. Magnetoencephalography (MEG) is becoming increasingly used in the clinical realm for this purpose. No investigators have previously reported on coregisteration of MEG clusters with postoperative resection cavities to evaluate whether complete “clusterectomy” (resection of the area associated with MEG clusters) was performed or to compare these findings with postoperative seizure-free outcomes.
Methods
The authors retrospectively reviewed the charts and imaging studies of 65 patients undergoing MEG followed by resective epilepsy surgery from 2009 until 2012 at the Cleveland Clinic. Preoperative MEG studies were fused with postoperative MRI studies to evaluate whether clusters were within the resected area. These data were then correlated with postoperative seizure freedom.
Results
Sixty-five patients were included in this study. The average duration of follow-up was 13.9 months, the mean age at surgery was 23.1 years, and the mean duration of epilepsy was 13.7 years. In 30 patients, the main cluster was located completely within the resection cavity, in 28 it was completely outside the resection cavity, and in 7 it was partially within the resection cavity. Seventy-four percent of patients were seizure free at 12 months after surgery, and this rate decreased to 60% at 24 months. Improved likelihood of seizure freedom was seen with complete clusterectomy in patients with localization outside the temporal lobe (extra–temporal lobe epilepsy) (p = 0.04).
Conclusions
In patients with preoperative MEG studies that show clusters in surgically accessible areas outside the temporal lobe, we suggest aggressive resection to improve the chances for seizure freedom. When the cluster is found within the temporal lobe, further diagnostic testing may be required to better localize the epileptogenic zone.
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Affiliation(s)
| | - Lara Jehi
- 2Epilepsy Center, Cleveland Clinic Foundation, Cleveland, Ohio
| | | | - Katherine Shea
- 2Epilepsy Center, Cleveland Clinic Foundation, Cleveland, Ohio
| | | | - John Mosher
- 2Epilepsy Center, Cleveland Clinic Foundation, Cleveland, Ohio
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Alkawadri R, Burgess R, Isitan C, Wang IZ, Kakisaka Y, Alexopoulos AV. Yield of repeat routine MEG recordings in clinical practice. Epilepsy Behav 2013; 27:416-9. [PMID: 23541858 DOI: 10.1016/j.yebeh.2013.02.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Revised: 02/18/2013] [Accepted: 02/26/2013] [Indexed: 11/28/2022]
Abstract
From 377 consecutive MEG studies for patients with intractable epilepsy performed at the Cleveland Clinic between 2008 and 2011, 19 patients were referred for a repeat MEG. Source localization was done using a single equivalent current dipole (ECD) model on identified interictal spike activity. Clinical, neuroimaging, and concurrent EEG and MEG findings were reviewed. The most common reasons for repeating MEG were as follows: negative initial study in 6 patients, paucity of recorded interictal discharges in 4, failed surgeries in 3, uncertain findings in the first study in 2, and research-related reasons in 4. Repeat MEG provided new localizing findings in 11/19 patients (58%), of whom 6 had negative or rare interictal findings in the first study. Lobar concordance of dipoles was present in 6 (85%) of the 7 patients with positive findings in both MEG studies. This study demonstrates that a repeat MEG may provide new localization data when a previous recording shows limited or no interictal abnormalities.
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Affiliation(s)
- Rafeed Alkawadri
- Cleveland Clinic Epilepsy Center, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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Wang ZI, Alexopoulos AV, Nair D, Krishnan B, Mosher JC, Burgess RC, Kakisaka Y. Feasibility of magnetoencephalography recording in an epilepsy patient with implanted responsive cortical stimulation device. Clin Neurophysiol 2013; 124:1705-6. [PMID: 23474057 DOI: 10.1016/j.clinph.2013.01.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 01/24/2013] [Accepted: 01/31/2013] [Indexed: 11/15/2022]
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Paetau R, Mohamed IS. Magnetoencephalography (MEG) and other neurophysiological investigations. HANDBOOK OF CLINICAL NEUROLOGY 2013; 111:461-5. [DOI: 10.1016/b978-0-444-52891-9.00050-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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American Clinical Magnetoencephalography Society Clinical Practice Guideline 1: recording and analysis of spontaneous cerebral activity. J Clin Neurophysiol 2012; 28:348-54. [PMID: 21811121 DOI: 10.1097/wnp.0b013e3182272fed] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Vale FL, Pollock G, Benbadis SR. Failed epilepsy surgery for mesial temporal lobe sclerosis: a review of the pathophysiology. Neurosurg Focus 2012; 32:E9. [DOI: 10.3171/2011.12.focus11318] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
The object of the current study was to review the electrophysiology and pathological substrate of failed temporal lobe surgery in patients with mesial temporal sclerosis.
Methods
A systematic review of the literature was performed for the years 1999–2010 to assess the cause of failure and to identify potential reoperation candidates.
Results
Repeat electroencephalographic evaluation documenting ipsilateral temporal lobe onset was the most frequent cause for recurrent epileptogenesis, followed by contralateral temporal lobe seizures. Less frequently, surgical failures demonstrated an electroencephalogram that was compatible with extratemporal localization. The generation of occult or new epileptogenic zones as well as residual epileptogenic tissue could explain these findings.
Conclusions
The outcome of temporal lobe surgery for epilepsy is challenged by a somewhat consistent failure rate. Reoperation results in improved seizure control in properly selected patients. A detailed knowledge of the pathophysiology is beneficial for the reevaluation of these patients.
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Duchowny M, Cross JH. Preoperative evaluation in children for epilepsy surgery. HANDBOOK OF CLINICAL NEUROLOGY 2012; 108:829-839. [PMID: 22939069 DOI: 10.1016/b978-0-444-52899-5.00031-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Affiliation(s)
- Michael Duchowny
- University of Miami Leonard Miller School of Medicine, Miami, FL, USA.
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Vale FL, Effio E, Arredondo N, Bozorg A, Wong K, Martinez C, Downes K, Tatum WO, Benbadis SR. Efficacy of temporal lobe surgery for epilepsy in patients with negative MRI for mesial temporal lobe sclerosis. J Clin Neurosci 2012; 19:101-6. [DOI: 10.1016/j.jocn.2011.08.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 08/01/2011] [Accepted: 08/13/2011] [Indexed: 10/14/2022]
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High kurtosis of intracranial electroencephalogram as a marker of ictogenicity in pediatric epilepsy surgery. Clin Neurophysiol 2012; 123:93-9. [DOI: 10.1016/j.clinph.2011.05.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Revised: 05/05/2011] [Accepted: 05/24/2011] [Indexed: 11/21/2022]
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Sugiyama I, Imai K, Yamaguchi Y, Ochi A, Akizuki Y, Go C, Akiyama T, Snead OC, Rutka JT, Drake JM, Widjaja E, Chuang SH, Cheyne D, Otsubo H. Localization of epileptic foci in children with intractable epilepsy secondary to multiple cortical tubers by using synthetic aperture magnetometry kurtosis. J Neurosurg Pediatr 2009; 4:515-22. [PMID: 19951036 DOI: 10.3171/2009.7.peds09198] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT Magnetoencephalography (MEG) has been typically used to localize epileptic activity by modeling interictal activity as equivalent current dipoles (ECDs). Synthetic aperture magnetometry (SAM) is a recently developed adaptive spatial filtering algorithm for MEG that provides some advantages over the ECD approach. The SAM-kurtosis algorithm (also known as SAM[g2]) additionally provides automated temporal detection of spike sources by using excess kurtosis value (steepness of epileptic spike on virtual sensors). To evaluate the efficacy of the SAM(g2) method, the authors applied it to readings obtained in children with intractable epilepsy secondary to tuberous sclerosis complex (TSC), and compared them to localizations obtained with ECDs. METHODS The authors studied 13 children with TSC (7 girls) whose ages ranged from 13 months to 16.3 years (mean 7.3 years). Video electroencephalography, MR imaging, and MEG studies were analyzed. A single ECD model was applied to localize ECD clusters. The SAM(g2) value was calculated at each SAM(g2) virtual voxel in the patient's MR imaging-defined brain volume. The authors defined the epileptic voxels of SAM(g2) (evSAM[g2]) as those with local peak kurtosis values higher than half of the maximum. A clustering of ECDs had to contain > or = 6 ECDs within 1 cm of each other, and a grouping of evSAM(g2)s had to contain > or = 3 evSAM(g2)s within 1 cm of each other. The authors then compared both ECD clusters and evSAM(g2) groups with the resection area and correlated these data with seizure outcome. RESULTS Seizures started when patients were between 6 weeks and 8 years of age (median 6 months), and became intractable secondary to multiple tubers in all cases. Ictal onset on scalp video electroencephalography was lateralized in 8 patients (62%). The MEG studies showed multiple ECD clusters in 7 patients (54%). The SAM(g2) method showed multiple groups of epileptic voxels in 8 patients (62%). Colocalization of grouped evSAM(g2) with ECD clusters ranged from 20 to 100%, with a mean of 82%. Eight patients underwent resection of single (1 patient) and multiple (7 patients) lobes, with 6 patients achieving freedom from seizures. Of 8 patients who underwent surgery, in 7 the resection area covered ECD clusters and grouped evSAM(g2)s. In the remaining patient the resection area partially included the ECD cluster and grouped evSAM(g2)s. Six of the 7 patients became seizure free. CONCLUSIONS The combination of SAM(g2) and ECD analyses succeeded in localizing the complex epileptic zones in children with TSC who had intractable epilepsy secondary to multiple cortical tubers. For the subset of children with TSC who present with early-onset and nonlateralized seizures, MEG studies in which SAM(g2) and ECD are used might identify suitable candidates for resection to control seizures.
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Affiliation(s)
- Ichiro Sugiyama
- Divisions of Neurology, The Hospital for Sick Children, University of Toronto, Ontario, Canada
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American Clinical MEG Society (ACMEGS) Position Statement: The Value of Magnetoencephalography (MEG)/Magnetic Source Imaging (MSI) in Noninvasive Presurgical Evaluation of Patients With Medically Intractable Localization-related Epilepsy. J Clin Neurophysiol 2009; 26:290-3. [DOI: 10.1097/wnp.0b013e3181b49d50] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Ramos E, Benbadis S, Vale FL. Failure of temporal lobe resection for epilepsy in patients with mesial temporal sclerosis: results and treatment options. J Neurosurg 2009; 110:1127-34. [PMID: 19249930 DOI: 10.3171/2009.1.jns08638] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT The purpose of this study was to identify the causes of failed temporal lobe resection in patients with mesial temporal sclerosis (MTS) and the role of repeat surgery for seizure control. METHODS This is a retrospective study of 105 patients who underwent temporal lobe resection for MTS with unilateral electroencephalographic findings. The mean follow-up duration was 36 months (range 24-84 months). Surgeries were all performed by the senior author (F.L.V.). RESULTS Following initial surgical intervention, 97 patients (92%) improved to Engel Class I or II (Group A), and 8 (8%) did not have significant improvement (Engel Class III or IV; Group B). These 8 patients were restudied using video-electroencephalography (EEG) and MR imaging. All major surgical failures occurred within 1 year after initial intervention. Reevaluation demonstrated 3 patients (37.5%) with contralateral temporal EEG findings. Five patients (62.5%) had evidence of ipsilateral recurrent discharges. Four patients underwent extended neocortical resection along the previous resection cavity. Their outcomes ranged from Engel Class I to Class III. Only 1 patient (12.5%) who failed to improve after initial surgery was found to have incomplete resection of mesial structures. This last patient underwent reoperation to complete the resection and improved to Engel Class I. CONCLUSIONS Failure of temporal lobe resection for MTS is multifactorial. The cause of failure lies in the pathological substrate of the epileptogenic area. Complete seizure control cannot be predicted solely by conventional preoperative workup. Initial surgical failures from temporal lobe resection often benefit from reevaluation, because reoperation may be beneficial in selected patients. Based on this work, the authors have proposed a management and treatment algorithm for these patients.
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Affiliation(s)
- Edwin Ramos
- Department of Neurological Surgery, University of South Florida College of Medicine, Tampa, Florida, USA
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Agirre-Arrizubieta Z, Huiskamp GJM, Ferrier CH, van Huffelen AC, Leijten FSS. Interictal magnetoencephalography and the irritative zone in the electrocorticogram. Brain 2009; 132:3060-71. [DOI: 10.1093/brain/awp137] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Nakayama T, Otsuki T, Kaneko Y, Nakama H, Kaido T, Otsubo H, Nakagawa E, Sasaki M, Sugai K. Repeat magnetoencephalography and surgeries to eliminate atonic seizures of non-lesional frontal lobe epilepsy. Epilepsy Res 2009; 84:263-7. [DOI: 10.1016/j.eplepsyres.2009.02.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2008] [Revised: 12/23/2008] [Accepted: 02/01/2009] [Indexed: 12/01/2022]
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Tovar-Spinoza ZS, Ochi A, Rutka JT, Go C, Otsubo H. The role of magnetoencephalography in epilepsy surgery. Neurosurg Focus 2008; 25:E16. [DOI: 10.3171/foc/2008/25/9/e16] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Epilepsy surgery requires the precise localization of the epileptogenic zone and the anatomical localization of eloquent cortex so that these areas can be preserved during cortical resection. Magnetoencephalography (MEG) is a technique that maps interictal magnetic dipole sources onto MR imaging to produce a magnetic source image. Magneto-encephalographic spike sources can be used to localize the epileptogenic zone and be part of the workup of the patient for epilepsy surgery in conjunction with data derived from an analysis of seizure semiology, scalp video electroencephalography, PET, functional MR imaging, and neuropsychological testing. In addition, magnetoencephalographic spike sources can be linked to neuronavigation platforms for use in the neurosurgical field. Finally, paradigms have been developed so that MEG can be used to identify functional areas of the cerebral cortex including the somatosensory, motor, language, and visual evoked fields.
The authors review the basic principles of MEG and the utility of MEG for presurgical planning as well as intra-operative mapping and discuss future applications of MEG technology.
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Affiliation(s)
| | - Ayako Ochi
- 2Neurology, The Hospital for Sick Children, University of Toronto, Ontario, Canada
| | | | - Cristina Go
- 2Neurology, The Hospital for Sick Children, University of Toronto, Ontario, Canada
| | - Hiroshi Otsubo
- 2Neurology, The Hospital for Sick Children, University of Toronto, Ontario, Canada
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Stone SSD, Rutka JT. Utility of neuronavigation and neuromonitoring in epilepsy surgery. Neurosurg Focus 2008; 25:E17. [DOI: 10.3171/foc/2008/25/9/e17] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The management of medically refractory epilepsy poses both a valuable therapeutic opportunity and a formidable technical challenge to epilepsy surgeons. Recent decades have produced significant advancements in the capabilities and availability of adjunctive tools in epilepsy surgery. In particular, image-based neuronavigation and electrophysiological neuromonitoring represent versatile and informative modalities that can assist a surgeon in performing safe and effective resections. In the present article the authors discuss these 2 subjects with reference to how they can be applied and what evidence supports their use. As technologies evolve with demonstrated and potential utility, it is important for all clinicians who deal with epilepsy to understand where neuronavigation and neuromonitoring stand in the present and what avenues for improvement exist for the future.
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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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Yoshinaga H, Kobayashi K, Hoshida T, Kinugasa K, Ohtuska Y. Magnetoencephalogram in a postoperative case with a large skull defect. Pediatr Neurol 2008; 39:48-51. [PMID: 18555173 DOI: 10.1016/j.pediatrneurol.2008.03.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2007] [Revised: 01/30/2008] [Accepted: 03/10/2008] [Indexed: 10/22/2022]
Abstract
We present a patient in whom magnetoencephalograms were successfully performed in presurgical and postsurgical evaluations. A 12-year-old boy with congenital porencephaly was admitted with refractory adversive seizures and frontal absence seizures. Ictal magnetoencephalographic dipoles with frontal absence seizures were located in the left frontal lobe, anterior to the porencephalic cyst, and concordant with the same area detected by intraoperative electrocorticography. A partial cortical excision was performed, and the patient's cranial bone flap was removed because of an epidural abscess. The frontal absences then disappeared. The magnetoencephalogram revealed that secondary bilateral synchrony of focal discharges from the lesion may have caused the generalized seizures in this patient. Because of residual partial seizures, second and third magnetoencephalograms were performed, and we detected residual spike dipoles clustering in the area posterior to the cavity of cortical excision and anterior to the porencephalic cyst. Another excision of the area between the cavity and frontal edge of the cyst was performed, and seizure frequency diminished dramatically. In this case, despite the failure of dipole estimation by electroencephalogram in the context of a large bone defect, the magnetoencephalogram was useful in detecting the residual epileptogenic zone after failed epilepsy surgery.
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Affiliation(s)
- Harumi Yoshinaga
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan.
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Ochi A, Otsubo H. Magnetoencephalography-guided epilepsy surgery for children with intractable focal epilepsy: SickKids experience. Int J Psychophysiol 2008; 68:104-10. [DOI: 10.1016/j.ijpsycho.2007.12.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 11/30/2007] [Accepted: 12/12/2007] [Indexed: 11/28/2022]
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