1
|
Vogrin SJ, Plummer C. EEG Source Imaging-Clinical Considerations for EEG Acquisition and Signal Processing for Improved Temporo-Spatial Resolution. J Clin Neurophysiol 2024; 41:8-18. [PMID: 38181383 DOI: 10.1097/wnp.0000000000001023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2024] Open
Abstract
SUMMARY EEG source imaging (ESI) has gained traction in recent years as a useful clinical tool for the noninvasive surgical work-up of patients with drug-resistant focal epilepsy. Despite its proven benefits for the temporo-spatial modeling of spike and seizure sources, ESI remains widely underused in clinical practice. This partly relates to a lack of clarity around an optimal approach to the acquisition and processing of scalp EEG data for the purpose of ESI. Here, we describe some of the practical considerations for the clinical application of ESI. We focus on patient preparation, the impact of electrode number and distribution across the scalp, the benefit of averaging raw data for signal analysis, and the relevance of modeling different phases of the interictal discharge as it evolves from take-off to peak. We emphasize the importance of recording high signal-to-noise ratio data for reliable source analysis. We argue that the accuracy of modeling cortical sources can be improved using higher electrode counts that include an inferior temporal array, by averaging interictal waveforms rather than limiting ESI to single spike analysis, and by careful interrogation of earlier phase components of these waveforms. No amount of postacquisition signal processing or source modeling sophistication, however, can make up for suboptimally recorded scalp EEG data in a poorly prepared patient.
Collapse
Affiliation(s)
- Simon J Vogrin
- Centre for Mental Health and Brain Sciences, Swinburne University of Technology, Melbourne, Victoria, Australia
- Department of Neurosciences, St Vincent's Hospital, Melbourne, Victoria, Australia; and
- Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
| | - Chris Plummer
- Centre for Mental Health and Brain Sciences, Swinburne University of Technology, Melbourne, Victoria, Australia
- Department of Neurosciences, St Vincent's Hospital, Melbourne, Victoria, Australia; and
- Department of Medicine, University of Melbourne, Melbourne, Victoria, Australia
| |
Collapse
|
2
|
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.
Collapse
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
| |
Collapse
|
3
|
Gautham B, Abdulhak A, Mundlamuri RC, Narayanan M, Jayabal V, Kenchaiah R, Asranna A, Dawn BR, Jitender S, Nagaraj C, Mangalore S, Karthik K, Sadashiva N, Mahadevan A, Rajeswaran J, Kumar K, Arivazhagan A, Rao MB, Sinha S. Magnetic source imaging in presurgical evaluation of paediatric focal drug-resistant epilepsy and its predictive value of surgical outcome in lesional cases: A single-centre experience from South India. Seizure 2021; 91:22-28. [PMID: 34058605 DOI: 10.1016/j.seizure.2021.05.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 05/14/2021] [Accepted: 05/16/2021] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVE This study aims to evaluate the utility of magnetoencephalography in presurgical planning and in predicting post-surgical seizure outcome. METHODS This study included a cohort of 231 children (1-18 years) with focal drug-resistant epilepsy who underwent MEG as a part of their presurgical workup. Characteristics of MEG observations were described in all children. The concordance and agreement of Magnetic Source Imaging (MSI) of interictal discharges (IED) was estimated with either of the 3 subgroups - MRI lesion; presumed epileptogenic zone (EZ); or resection cavity. In operated children group, MEG dipole characteristics between good and poor outcome groups were assessed. RESULTS A total of 153 cases (66.2%) showed frequent IEDs (60 spikes/60 min). Of the 173 cases where MSI showed clusters (74.9%), 151 had lesions and 22 were non-lesional. amongst patients with lesional epilepsy and MEG clusters, class I concordance (MEG localization either completely included or overlapped at least 60% with the MRI lesion) was seen in 60.92% with a Cohen's kappa of 0.608. In non-lesional epilepsy, class I concordance of MEG with presumed EZ was found in (81.81%) with an agreement of 0.317. Fifty-three children underwent surgery of whom 39 (73.58%) showed a good outcome (Engel I). In operated children, concordance between MEG focus and resection cavity was observed in 23 (58.97%) with good outcome and in 12 (86.72%) with poor outcome with no significant difference (p>0.05). However, MEG cluster regular organization and clusterectomy are associated with good seizure outcome postoperatively (p< 0.05). Presence of scatters were associated with poor outcome (p<0.05) in children with focal cortical dysplasia. CONCLUSIONS MEG provides useful information that can serve as a biomarker for prognosticating the surgical outcome in paediatric epilepsy. Cluster removal and regular cluster organization shows predictive power in post-surgical prognostication in children and the presence of scatters predicts poor outcome in children with focal cortical dysplasia.
Collapse
Affiliation(s)
- Bhargava Gautham
- MEG research Centre, NIMHANS, Hosur Road, Bangalore, India; Department of Neurology, NIMHANS, Hosur Road, Bangalore, India
| | - Asheeb Abdulhak
- Department of Neurology, NIMHANS, Hosur Road, Bangalore, India
| | | | - Mariyappa Narayanan
- MEG research Centre, NIMHANS, Hosur Road, Bangalore, India; Department of Neurology, NIMHANS, Hosur Road, Bangalore, India
| | | | | | - Ajay Asranna
- Department of Neurology, NIMHANS, Hosur Road, Bangalore, India
| | - Bharath Rose Dawn
- Department of Neuroimaging and Interventional Radiology, NIMHANS, Hosur Road, Bangalore, India
| | - Saini Jitender
- Department of Neuroimaging and Interventional Radiology, NIMHANS, Hosur Road, Bangalore, India
| | - Chandana Nagaraj
- Department of Neuroimaging and Interventional Radiology, NIMHANS, Hosur Road, Bangalore, India
| | - Sandhya Mangalore
- Department of Neuroimaging and Interventional Radiology, NIMHANS, Hosur Road, Bangalore, India
| | - Kulanthaivelu Karthik
- Department of Neuroimaging and Interventional Radiology, NIMHANS, Hosur Road, Bangalore, India
| | | | - Anita Mahadevan
- Department of Neuropathology, NIMHANS, Hosur Road, Bangalore, India
| | - Jamuna Rajeswaran
- Department of Clinical Psychology, NIMHANS, Hosur Road, Bangalore, India
| | - Keshav Kumar
- Department of Clinical Psychology, NIMHANS, Hosur Road, Bangalore, India
| | | | | | - Sanjib Sinha
- MEG research Centre, NIMHANS, Hosur Road, Bangalore, India; Department of Neurology, NIMHANS, Hosur Road, Bangalore, India.
| |
Collapse
|
4
|
Habib MA, Ibrahim F, Mohktar MS, Kamaruzzaman SB, Lim KS. Recursive independent component analysis (ICA)-decomposition of ictal EEG to select the best ictal component for EEG source imaging. Clin Neurophysiol 2020; 131:642-654. [DOI: 10.1016/j.clinph.2019.11.058] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 11/25/2019] [Accepted: 11/30/2019] [Indexed: 11/28/2022]
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
Murakami H, Wang ZI, Marashly A, Krishnan B, Prayson RA, Kakisaka Y, Mosher JC, Bulacio J, Gonzalez-Martinez JA, Bingaman WE, Najm IM, Burgess RC, Alexopoulos AV. Correlating magnetoencephalography to stereo-electroencephalography in patients undergoing epilepsy surgery. Brain 2018; 139:2935-2947. [PMID: 27567464 DOI: 10.1093/brain/aww215] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 07/06/2016] [Indexed: 11/15/2022] Open
Affiliation(s)
- Hiroatsu Murakami
- Department of Neurosurgery, Brain Research Institute, Niigata University, Niigata, Japan.,Epilepsy Center, Cleveland Clinic, Cleveland, OH, USA
| | - Zhong I Wang
- Epilepsy Center, Cleveland Clinic, Cleveland, OH, USA
| | - Ahmad Marashly
- Department of Child Neurology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Balu Krishnan
- Epilepsy Center, Cleveland Clinic, Cleveland, OH, USA
| | - Richard A Prayson
- Department of Anatomic Pathology, Cleveland Clinic, Cleveland, OH, USA
| | - Yosuke Kakisaka
- Department of Epileptology, Tohoku University School of Medicine, Sendai, Japan
| | - John C Mosher
- Epilepsy Center, Cleveland Clinic, Cleveland, OH, USA
| | - Juan Bulacio
- Epilepsy Center, Cleveland Clinic, Cleveland, OH, USA
| | | | | | - Imad M Najm
- Epilepsy Center, Cleveland Clinic, Cleveland, OH, USA
| | | | | |
Collapse
|
7
|
Montes-Restrepo V, Carrette E, Strobbe G, Gadeyne S, Vandenberghe S, Boon P, Vonck K, Mierlo PV. The Role of Skull Modeling in EEG Source Imaging for Patients with Refractory Temporal Lobe Epilepsy. Brain Topogr 2016; 29:572-89. [PMID: 26936594 DOI: 10.1007/s10548-016-0482-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 02/19/2016] [Indexed: 11/26/2022]
Abstract
We investigated the influence of different skull modeling approaches on EEG source imaging (ESI), using data of six patients with refractory temporal lobe epilepsy who later underwent successful epilepsy surgery. Four realistic head models with different skull compartments, based on finite difference methods, were constructed for each patient: (i) Three models had skulls with compact and spongy bone compartments as well as air-filled cavities, segmented from either computed tomography (CT), magnetic resonance imaging (MRI) or a CT-template and (ii) one model included a MRI-based skull with a single compact bone compartment. In all patients we performed ESI of single and averaged spikes marked in the clinical 27-channel EEG by the epileptologist. To analyze at which time point the dipole estimations were closer to the resected zone, ESI was performed at two time instants: the half-rising phase and peak of the spike. The estimated sources for each model were validated against the resected area, as indicated by the postoperative MRI. Our results showed that single spike analysis was highly influenced by the signal-to-noise ratio (SNR), yielding estimations with smaller distances to the resected volume at the peak of the spike. Although averaging reduced the SNR effects, it did not always result in dipole estimations lying closer to the resection. The proposed skull modeling approaches did not lead to significant differences in the localization of the irritative zone from clinical EEG data with low spatial sampling density. Furthermore, we showed that a simple skull model (MRI-based) resulted in similar accuracy in dipole estimation compared to more complex head models (based on CT- or CT-template). Therefore, all the considered head models can be used in the presurgical evaluation of patients with temporal lobe epilepsy to localize the irritative zone from low-density clinical EEG recordings.
Collapse
Affiliation(s)
- Victoria Montes-Restrepo
- Medical Image and Signal Processing (MEDISIP), Ghent University-iMinds Medical IT Department, De Pintelaan 185, 9000, Ghent, Belgium.
| | - Evelien Carrette
- Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology, Ghent University Hospital, De Pintelaan 185, 9000, Ghent, Belgium
| | - Gregor Strobbe
- Medical Image and Signal Processing (MEDISIP), Ghent University-iMinds Medical IT Department, De Pintelaan 185, 9000, Ghent, Belgium
| | - Stefanie Gadeyne
- Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology, Ghent University Hospital, De Pintelaan 185, 9000, Ghent, Belgium
| | - Stefaan Vandenberghe
- Medical Image and Signal Processing (MEDISIP), Ghent University-iMinds Medical IT Department, De Pintelaan 185, 9000, Ghent, Belgium
| | - Paul Boon
- Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology, Ghent University Hospital, De Pintelaan 185, 9000, Ghent, Belgium
| | - Kristl Vonck
- Laboratory for Clinical and Experimental Neurophysiology, Neurobiology and Neuropsychology, Ghent University Hospital, De Pintelaan 185, 9000, Ghent, Belgium
| | - Pieter van Mierlo
- Medical Image and Signal Processing (MEDISIP), Ghent University-iMinds Medical IT Department, De Pintelaan 185, 9000, Ghent, Belgium
| |
Collapse
|
8
|
Bagić A, Ebersole JS. Does MEG/MSI dipole variability mean unreliability? Clin Neurophysiol 2015; 126:209-11. [DOI: 10.1016/j.clinph.2014.01.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 01/20/2014] [Accepted: 01/23/2014] [Indexed: 11/28/2022]
|
9
|
Aydin Ü, Vorwerk J, Küpper P, Heers M, Kugel H, Galka A, Hamid L, Wellmer J, Kellinghaus C, Rampp S, Wolters CH. Combining EEG and MEG for the reconstruction of epileptic activity using a calibrated realistic volume conductor model. PLoS One 2014; 9:e93154. [PMID: 24671208 PMCID: PMC3966892 DOI: 10.1371/journal.pone.0093154] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 02/28/2014] [Indexed: 11/18/2022] Open
Abstract
To increase the reliability for the non-invasive determination of the irritative zone in presurgical epilepsy diagnosis, we introduce here a new experimental and methodological source analysis pipeline that combines the complementary information in EEG and MEG, and apply it to data from a patient, suffering from refractory focal epilepsy. Skull conductivity parameters in a six compartment finite element head model with brain anisotropy, constructed from individual MRI data, are estimated in a calibration procedure using somatosensory evoked potential (SEP) and field (SEF) data. These data are measured in a single run before acquisition of further runs of spontaneous epileptic activity. Our results show that even for single interictal spikes, volume conduction effects dominate over noise and need to be taken into account for accurate source analysis. While cerebrospinal fluid and brain anisotropy influence both modalities, only EEG is sensitive to skull conductivity and conductivity calibration significantly reduces the difference in especially depth localization of both modalities, emphasizing its importance for combining EEG and MEG source analysis. On the other hand, localization differences which are due to the distinct sensitivity profiles of EEG and MEG persist. In case of a moderate error in skull conductivity, combined source analysis results can still profit from the different sensitivity profiles of EEG and MEG to accurately determine location, orientation and strength of the underlying sources. On the other side, significant errors in skull modeling are reflected in EEG reconstruction errors and could reduce the goodness of fit to combined datasets. For combined EEG and MEG source analysis, we therefore recommend calibrating skull conductivity using additionally acquired SEP/SEF data.
Collapse
Affiliation(s)
- Ümit Aydin
- Institute for Biomagnetism and Biosignalanalysis, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Johannes Vorwerk
- Institute for Biomagnetism and Biosignalanalysis, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Philipp Küpper
- Institute for Biomagnetism and Biosignalanalysis, Westfälische Wilhelms-Universität Münster, Münster, Germany
- Department of Neurology, Klinikum Osnabrück, Osnabrück, Germany
| | - Marcel Heers
- Ruhr-Epileptology Department of Neurology, Universitätsklinikum Knappschaftskrankenhaus Bochum, Bochum, Germany
| | - Harald Kugel
- Department of Clinical Radiology, Universitätsklinikum Münster, Münster, Germany
| | - Andreas Galka
- Department of Neuropediatrics, Universitätsklinikum Schleswig-Holstein, Kiel, Germany
| | - Laith Hamid
- Department of Neuropediatrics, Universitätsklinikum Schleswig-Holstein, Kiel, Germany
| | - Jörg Wellmer
- Ruhr-Epileptology Department of Neurology, Universitätsklinikum Knappschaftskrankenhaus Bochum, Bochum, Germany
| | | | - Stefan Rampp
- Epilepsy Center, Department of Neurology, Universitätsklinikum Erlangen, Erlangen, Germany
| | - Carsten Hermann Wolters
- Institute for Biomagnetism and Biosignalanalysis, Westfälische Wilhelms-Universität Münster, Münster, Germany
| |
Collapse
|
10
|
Yoshinaga H, Kobayashi K, Akiyama T, Shibata T, Endoh F, Ohtsuka Y. Clinical implications of preceding positive spikes in patients with benign partial epilepsy and febrile seizures. Brain Dev 2013; 35:299-306. [PMID: 22800933 DOI: 10.1016/j.braindev.2012.06.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 06/21/2012] [Accepted: 06/22/2012] [Indexed: 10/28/2022]
Abstract
PURPOSE To clarify the clinical implications of the preceding positive spikes (PPSs) observed primarily in rolandic spikes, we analyzed PPSs in the rolandic and occipital spikes observed in the electroencephalograms (EEGs) of patients with two types of benign partial epilepsies (benign childhood epilepsy with centro-temporal spikes [BECT] and Panayiotopoulos syndrome [PS]) and febrile seizures (FS). SUBJECTS AND METHODS We identified patients from our outpatient EEG database that were seen between 2006 and 2008 that had BECT, PS, and FS with rolandic or occipital spikes. We generated an averaged spike for each patient from the rolandic and occipital spikes that were detected using an automatic spike detection and clustering system. We compared the presence rate of the averaged spikes with the PPS among the three groups (BECT vs. PS vs. FS) using sequential mapping. RESULTS We identified 25 BECT, 18 PS, and 15 FS patients with rolandic spikes. Fifteen BECT and nine PS patients exhibited a PPS in their averaged rolandic spikes, whereas only four FS patients did. Three of these four FS patients later developed afebrile seizures, and one of them was diagnosed as having PS. We analyzed eight PS and six FS patients with occipital spikes. Five PS patients exhibited a PPS in their averaged occipital spikes, whereas only one FS patient did. This FS patient later developed prolonged autonomic febrile seizures. CONCLUSION PPSs are observed not only in rolandic spikes associated with BECT that is related strictly to sylvian seizures, but also in rolandic and occipital spikes associated with PS. Although PPSs are rare in such spikes observed in FS, patients with FS and PPSs may have an increased risk of developing afebrile seizures or prolonged autonomic febrile seizures. Further studies are warranted to determine the diagnostic utility of PPSs as a marker of the future development of epilepsy when they are observed in FS patients.
Collapse
Affiliation(s)
- Harumi Yoshinaga
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Japan.
| | | | | | | | | | | |
Collapse
|
11
|
Kaiboriboon K, Lüders HO, Hamaneh M, Turnbull J, Lhatoo SD. EEG source imaging in epilepsy--practicalities and pitfalls. Nat Rev Neurol 2012; 8:498-507. [PMID: 22868868 DOI: 10.1038/nrneurol.2012.150] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
EEG source imaging (ESI) is a model-based imaging technique that integrates temporal and spatial components of EEG to identify the generating source of electrical potentials recorded on the scalp. Recent advances in computer technologies have made the analysis of ESI data less time-consuming, and have rekindled interest in this technique as a clinical diagnostic tool. On the basis of the available body of evidence, ESI seems to be a promising tool for epilepsy evaluation; however, the precise clinical value of ESI in presurgical evaluation of epilepsy and in localization of eloquent cortex remains to be investigated. In this Review, we describe two fundamental issues in ESI; namely, the forward and inverse problems, and their solutions. The clinical application of ESI in surgical planning for patients with medically refractory focal epilepsy, and its use in source reconstruction together with invasive recordings, is also discussed. As ESI can be used to map evoked responses, we discuss the clinical utility of this technique in cortical mapping-an essential process when planning resective surgery for brain regions that are in close proximity to eloquent cortex.
Collapse
Affiliation(s)
- Kitti Kaiboriboon
- Epilepsy Center, Neurological Institute, University Hospitals Case Medical Center, Case Western Reserve University School of Medicine, 11100 Euclid Avenue, Lakeside 3200, Cleveland, OH 44106, USA. kitti.kaiboriboon@ uhhospitals.org
| | | | | | | | | |
Collapse
|
12
|
Shirozu H, Iida K, Hashizume A, Hanaya R, Kiura Y, Kurisu K, Arita K, Otsubo H. Gradient magnetic-field topography reflecting cortical activities of neocortical epilepsy spikes. Epilepsy Res 2010; 90:121-31. [DOI: 10.1016/j.eplepsyres.2010.04.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2009] [Revised: 04/01/2010] [Accepted: 04/08/2010] [Indexed: 10/19/2022]
|
13
|
|
14
|
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.
Collapse
|
15
|
Bast T, Boppel T, Rupp A, Harting I, Hoechstetter K, Fauser S, Schulze-Bonhage A, Rating D, Scherg M. Noninvasive source localization of interictal EEG spikes: effects of signal-to-noise ratio and averaging. J Clin Neurophysiol 2007; 23:487-97. [PMID: 17143137 DOI: 10.1097/01.wnp.0000232208.14060.c7] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Source localization using single current dipoles estimates equivalent centers of the spiking gray matter. The extent of the active cortex, however, is difficult to assess from scalp EEG because of the unknown individual volume conduction. The spatial scatter of dipole localizations of single spikes has been proposed as a measure of extent. Single spike localization, however, is strongly dependent on the signal-to-noise ratio (SNR), that is, the ratio of spike and background EEG amplitudes. On the other hand, averaging of all spikes yields only the localization of equivalent centers of activity. We investigated the influence of SNR and multiple subaverages on the estimation of spatial extent by comparing the localization scatter of 100 single spikes in 27 spike types of 25 epilepsy patients with 1000 different subaverages computed by random sampling and bootstrapping. Averaging increased SNR and therefore allowed for localization not only at the spike peak but also during spike onset when less cortex is active. In several subjects with known cortical lesions, the single spike scatter considerably exceeded the lesion. Single dipole scatter was highly correlated with SNR (r = -0.83, P < 0.0001) and was greatly reduced when analyzing multiple subaverages of 10, 25, 50, and 100 spikes. Thus, we found a dominant role of the SNR on the estimated extent and improvement by scatterplots based on the dipole localization of randomly sampled subaverages.
Collapse
Affiliation(s)
- Thomas Bast
- Department of Pediatric Neurology, University Hospital Heidelberg, Germany.
| | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Yoshinaga H, Koutroumanidis M, Kobayashi K, Shirasawa A, Kikumoto K, Inoue T, Oka M, Ohtsuka Y. EEG Dipole Characteristics in Panayiotopoulos Syndrome. Epilepsia 2006; 47:781-7. [PMID: 16650145 DOI: 10.1111/j.1528-1167.2006.00519.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
PURPOSE Panayiotopoulos syndrome (PS) is a type of benign childhood partial epilepsy that is frequently associated with abundant multifocal spikes other than main occipital spikes on the EEG. In this study, we investigated the characteristic features of dipoles in PS. METHODS We performed dipole analysis of the interictal occipital spike discharges seen in 10 children with PS (group A) and in 10 children with other types of symptomatic localization-related epilepsy (group B). We analyzed the dipoles of the averaged spike in each patient. RESULTS In group A, the averaged occipital spikes in each patient showed dense dipole locations in the mesial occipital area; in group B, widely scattered dipole locations were observed. In Group A, the geometric centers of the dipoles at each time point (such as at the main negative peak and before or after the main peak) were estimated in the neighboring locations. In contrast, they tended to be scattered in group B. CONCLUSIONS Our study reveals that PS has high dipole stability, similar to that of rolandic epilepsy. From the electroencephalographic view, this seems to indicate a close link between these two syndromes.
Collapse
Affiliation(s)
- Harumi Yoshinaga
- Department of Child Neurology, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Oishi M, Kameyama S, Masuda H, Tohyama J, Kanazawa O, Sasagawa M, Otsubo H. Single and Multiple Clusters of Magnetoencephalographic Dipoles in Neocortical Epilepsy: Significance in Characterizing the Epileptogenic Zone. Epilepsia 2006; 47:355-64. [PMID: 16499760 DOI: 10.1111/j.1528-1167.2006.00428.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE To characterize the epileptogenic zone in neocortical epilepsy (NE) by using magnetoencephalography (MEG). METHODS We defined and compared locations of single and multiple clusters of equivalent current dipoles (ECDs) for interictal spikes with MRI findings, ictal-onset zones (IOZs) from subdural electroencephalography (SDEEG), resected areas, and postsurgical outcomes of 20 patients who underwent cortical resection for medically intractable NE. RESULTS Fourteen patients had single clusters; six had multiple clusters. Overlap of clusters and IOZs defined group A (nine patients), in which a single cluster coincided with the IOZ; group B1 (four patients), in which a single cluster was within or partially overlapped the IOZ; group B2 (five patients), in which multiple-cluster sections overlapped IOZs; group C (two patients; one single; one multiple), in which no overlap was seen. More single clusters (nine of 14) than multiple clusters (none of six) coincided with the IOZ (p = 0.014). More patients with single clusters (10 of 14) than patients with multiple clusters (one of six) had seizure-free outcomes (p = 0.049). Eight of nine patients in group A, versus three of 11 in groups B1, B2, and C, achieved seizure-free outcomes (p = 0.0098). Correlations between MRI findings and postsurgical outcomes were not statistically significant; eight of 13 patients with single lesions, one of four with no lesions, and two of three with multifocal lesions had seizure-free outcomes. CONCLUSIONS In neocortical epilepsy, MEG ECD clusters correlated with SDEEG IOZs. Single clusters indicated discrete epileptogenic zones that required complete resection for seizure-free outcome. Multiple clusters necessitated that the multiple or extensive epileptogenic zones be completely identified and delineated by SDEEG.
Collapse
Affiliation(s)
- Makoto Oishi
- Department of Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, 1-14-1 Masago, Niigata City, Niigata 950-2085, Japan
| | | | | | | | | | | | | |
Collapse
|
18
|
Im CH, Jung HK, Fujimaki N. Anatomically constrained dipole adjustment (ANACONDA) for accurate MEG/EEG focal source localizations. Phys Med Biol 2005; 50:4931-53. [PMID: 16204881 DOI: 10.1088/0031-9155/50/20/012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This paper proposes an alternative approach to enhance localization accuracy of MEG and EEG focal sources. The proposed approach assumes anatomically constrained spatio-temporal dipoles, initial positions of which are estimated from local peak positions of distributed sources obtained from a pre-execution of distributed source reconstruction. The positions of the dipoles are then adjusted on the cortical surface using a novel updating scheme named cortical surface scanning. The proposed approach has many advantages over the conventional ones: (1) as the cortical surface scanning algorithm uses spatio-temporal dipoles, it is robust with respect to noise; (2) it requires no a priori information on the numbers and initial locations of the activations; (3) as the locations of dipoles are restricted only on a tessellated cortical surface, it is physiologically more plausible than the conventional ECD model. To verify the proposed approach, it was applied to several realistic MEG/EEG simulations and practical experiments. From the several case studies, it is concluded that the anatomically constrained dipole adjustment (ANACONDA) approach will be a very promising technique to enhance accuracy of focal source localization which is essential in many clinical and neurological applications of MEG and EEG.
Collapse
Affiliation(s)
- Chang-Hwan Im
- Department of Biomedical Engineering, University of Minnesota, 7-105 BSBE, 312 Church Street SE, Minneapolis, MN 55455, USA.
| | | | | |
Collapse
|
19
|
Kobayashi K, Yoshinaga H, Ohtsuka Y, Gotman J. Dipole Modeling of Epileptic Spikes Can Be Accurate or Misleading. Epilepsia 2005; 46:397-408. [PMID: 15730537 DOI: 10.1111/j.0013-9580.2005.31404.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE We investigated the accuracy and potential for serious error when representing cortical generators of epileptic spikes with the common single-dipole model. Spike generators were realistically simulated with cortical areas of different extents. METHODS The source was simulated by using a patch that comprised small triangles on the cortical surface, each triangle having an elementary dipole generator with a moment corresponding to real intracerebral fields of spikes. The source-patch covered various clinically important parts of the temporal and frontal lobes, with an area ranging from 6 to 120 cm2. The scalp field was computed for each source-patch by using a realistic head model and was fitted by the single-dipole model to determine the best-fit dipole and the intracerebral distribution of residual variance (RV). Dipole modeling also was performed for the simulated scalp field with additional real EEG background. RESULTS The RV after fitting a dipole to the scalp field without noise was at most 1.34%. Scalp spikes arising from sources of 6 cm2 were of small amplitude, and the dipoles estimated for these spikes were inconsistent. Extension of the source area was associated with increase of scalp potential amplitude, only very small increase of RV, and increased consistency of the estimated dipoles. When the source was very large, the dipoles clustered at very misleading locations. CONCLUSIONS Pitfalls in dipole source localization are caused by the procedure of fitting the simplistic dipole model to real cortical sources with spatial extent and complex configuration.
Collapse
Affiliation(s)
- Katsuhiro Kobayashi
- Department of Child Neurology, Okayama University Graduate School of Medicine and Dentistry, and Okayama University Hospital, Okayama, Japan.
| | | | | | | |
Collapse
|
20
|
Bast T, Oezkan O, Rona S, Stippich C, Seitz A, Rupp A, Fauser S, Zentner J, Rating D, Scherg M. EEG and MEG source analysis of single and averaged interictal spikes reveals intrinsic epileptogenicity in focal cortical dysplasia. Epilepsia 2004; 45:621-31. [PMID: 15144427 DOI: 10.1111/j.0013-9580.2004.56503.x] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE Simultaneous interictal EEG and magnetoencephalography (MEG) recordings were used for noninvasive analysis of epileptogenicity in focal cortical dysplasia (FCD). The results of two different approach methods (multiple source analysis of averaged spikes and single dipole peak localization of single spikes) were compared with pre- and postoperative anatomic magnetic resonance imaging (MRI). PATIENTS We studied nine children and adolescents (age, 3.5-15.9 years) with localization-related epilepsy and FCD diagnosis based on MRI. Five patients underwent epilepsy surgery, two of them after long-term recording with subdural grid electrodes, and one after intraoperative electrocorticography. METHODS The 122-channel whole-head MEGs and 33-channel EEGs were recorded simultaneously for 25 to 40 min. Interictal spikes were identified visually and used as templates to search for similar spatiotemporal spike patterns throughout the recording. With the BESA program, similar spikes (r > 0.85) were detected, averaged, high-pass filtered (5 Hz) to enhance spike onset, and subjected to multiple spatiotemporal source analysis with a multishell spherical head model. Peak activity from single spikes was modeled by single dipoles for the same subset of spikes. Source localization was visualized by superposition on T1-weighted MRI and compared with the lesion identified in T1- and T2-weighted MRI. In the five cases undergoing epilepsy surgery, the results were correlated with invasive recordings, postoperative MRI, and outcome. RESULTS In all cases, the analysis of averaged spikes showed a localization of onset- and peak-related sources within the visible lesion for both EEG and MEG. Of the single spikes, 128 (45%; total 284) were localizable at the peak in MEG, and 170 (60%) in EEG. Of these, 91% localized within the lesion with MEG, and 93.5% with EEG. In three of five patients operated on, the resected area included the onset zones of averaged EEG and MEG spike activity. These patients had excellent postoperative outcome, whereas the others did not become seizure free. CONCLUSIONS Consistent MEG and EEG spike localization in the lesional zone confirmed the hypothesis of intrinsic epileptogenicity in FCD.
Collapse
Affiliation(s)
- Thomas Bast
- Department of Child Neurology, University of Heidelberg, Heidelberg, Germany.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Fernández A, de Sola RG, Amo C, Turrero A, Zuluaga P, Maestú F, Campo P, Ortiz T. Dipole Density of Low-Frequency and Spike Magnetic Activity: A Reliable Procedure in Presurgical Evaluation of Temporal Lobe Epilepsy. J Clin Neurophysiol 2004; 21:254-66. [PMID: 15509915 DOI: 10.1097/00004691-200407000-00004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Conventional visual analysis and dipole density analysis of magnetoencephalographic data for both spike and low-frequency magnetic activity were compared for presurgical evaluation in temporal lobe epilepsy (TLE) in a sample of 26 drug-resistant operated TLE patients. A series of logistic regression analyses were performed. Dipole density sensitivity was superior to visual localization analysis. Three separated logistic models were calculated for interictal spikes, low-frequency magnetic activity, and the combination of both measures. A combined interictal spike/low-frequency magnetic activity model predicted correctly the operated temporal lobe in all patients. Clear-cut criteria for the probability model are proposed that are valid for 92.3% of cases in the sample. The quantitative approach proposed by this study is an evidence-based model for presurgical evaluation of temporal lobe epilepsy, which improves previous magnetoencephalographic investigations and establishes working clinical criteria for patient evaluation in TLE.
Collapse
Affiliation(s)
- Alberto Fernández
- Centro MEG Dr. Pérez Modrego, Universidad Complutense de Madrid, Madrid, Spain
| | | | | | | | | | | | | | | |
Collapse
|