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Morgan VL, Conrad BN, Abou-Khalil B, Rogers BP, Kang H. Increasing structural atrophy and functional isolation of the temporal lobe with duration of disease in temporal lobe epilepsy. Epilepsy Res 2014; 110:171-8. [PMID: 25616470 DOI: 10.1016/j.eplepsyres.2014.12.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 11/21/2014] [Accepted: 12/04/2014] [Indexed: 10/24/2022]
Abstract
BACKGROUND Due to pharmacoresistant seizures and the underutilization of surgical treatments, a large number of temporal lobe epilepsy (TLE) patients experience seizures for years or decades. The goal of this study was to generate a predictive model of duration of disease with the least number of parameters possible in order to identify and quantify the significant volumetric and functional indicators of TLE progression. METHODS Two cohorts of subjects including 12 left TLE, 21 right TLE and 20 healthy controls (duration = 0) were imaged on a 3T MRI scanner using high resolution T1-weighted structural MRI and 20 min of resting functional MRI scanning. Multivariate linear regression methods were used to compute a predictive model of duration of disease using 49 predictors including functional connectivity and gray matter volumes computed from these images. RESULTS No model developed from the full set of data accurately predicted the duration of disease across the entire range from 3 to 50 years. We then performed the regression on 35 subjects with durations of disease in the range 10 to 35 years. The resulting predictive model showed that longer durations were associated with reductions in functional connectivity from the ipsilateral temporal lobe to the contralateral temporal lobe, precuneus and mid cingulate, and with decreases in volume of the ipsilateral hippocampus and pallidum. CONCLUSIONS Functional and volumetric parameters accurately predicted duration of disease in TLE. The findings suggest that TLE is associated with a gradual functional isolation and significant progressive structural atrophy of the ipsilateral temporal lobe over years of duration in the range of 10-35 years. Furthermore, these changes can also be detected in the contralateral hemisphere in these patients, but to a lesser degree.
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Affiliation(s)
- Victoria L Morgan
- Vanderbilt University Institute of Imaging Science, Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA.
| | - Benjamin N Conrad
- Vanderbilt University Institute of Imaging Science, Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | | | - Baxter P Rogers
- Vanderbilt University Institute of Imaging Science, Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN, USA
| | - Hakmook Kang
- Department of Biostatistics, Vanderbilt University, Nashville, TN, USA
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Caciagli L, Bernhardt BC, Hong SJ, Bernasconi A, Bernasconi N. Functional network alterations and their structural substrate in drug-resistant epilepsy. Front Neurosci 2014; 8:411. [PMID: 25565942 PMCID: PMC4263093 DOI: 10.3389/fnins.2014.00411] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/24/2014] [Indexed: 12/24/2022] Open
Abstract
The advent of MRI has revolutionized the evaluation and management of drug-resistant epilepsy by allowing the detection of the lesion associated with the region that gives rise to seizures. Recent evidence indicates marked chronic alterations in the functional organization of lesional tissue and large-scale cortico-subcortical networks. In this review, we focus on recent methodological developments in functional MRI (fMRI) analysis techniques and their application to the two most common drug-resistant focal epilepsies, i.e., temporal lobe epilepsy related to mesial temporal sclerosis and extra-temporal lobe epilepsy related to focal cortical dysplasia. We put particular emphasis on methodological developments in the analysis of task-free or “resting-state” fMRI to probe the integrity of intrinsic networks on a regional, inter-regional, and connectome-wide level. In temporal lobe epilepsy, these techniques have revealed disrupted connectivity of the ipsilateral mesiotemporal lobe, together with contralateral compensatory reorganization and striking reconfigurations of large-scale networks. In cortical dysplasia, initial observations indicate functional alterations in lesional, peri-lesional, and remote neocortical regions. While future research is needed to critically evaluate the reliability, sensitivity, and specificity, fMRI mapping promises to lend distinct biomarkers for diagnosis, presurgical planning, and outcome prediction.
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Affiliation(s)
- Lorenzo Caciagli
- Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Center, Montreal Neurological Institute and Hospital, McGill University Montreal, QC, Canada
| | - Boris C Bernhardt
- Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Center, Montreal Neurological Institute and Hospital, McGill University Montreal, QC, Canada
| | - Seok-Jun Hong
- Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Center, Montreal Neurological Institute and Hospital, McGill University Montreal, QC, Canada
| | - Andrea Bernasconi
- Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Center, Montreal Neurological Institute and Hospital, McGill University Montreal, QC, Canada
| | - Neda Bernasconi
- Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Center, Montreal Neurological Institute and Hospital, McGill University Montreal, QC, Canada
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Lee HW, Arora J, Papademetris X, Tokoglu F, Negishi M, Scheinost D, Farooque P, Blumenfeld H, Spencer DD, Constable RT. Altered functional connectivity in seizure onset zones revealed by fMRI intrinsic connectivity. Neurology 2014; 83:2269-77. [PMID: 25391304 PMCID: PMC4277677 DOI: 10.1212/wnl.0000000000001068] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Objective: The purpose of this study was to investigate functional connectivity (FC) changes in epileptogenic networks in intractable partial epilepsy obtained from resting-state fMRI by using intrinsic connectivity contrast (ICC), a voxel-based network measure of degree that reflects the number of connections to each voxel. Methods: We measured differences between intrahemispheric- and interhemispheric-ICC (ICCintra−inter) that could reveal localized connectivity abnormalities in epileptogenic zones while more global network changes would be eliminated when subtracting these values. The ICCintra−inter map was compared with the seizure onset zone (SOZ) based on intracranial EEG (icEEG) recordings in 29 patients with at least 1 year of postsurgical follow-up. Two independent reviewers blindly interpreted the icEEG and fMRI data, and the concordance rates were compared for various clinical factors. Results: Concordance between the icEEG SOZ and ICCintra−inter map was observed in 72.4% (21/29) of the patients, which was higher in patients with good surgical outcome, especially in those patients with temporal lobe epilepsy (TLE) or lateral temporal seizure localization. Concordance was also better in the extratemporal lobe epilepsy than the TLE group. In 85.7% (18/21) of the cases, the ICCintra−inter values were negative in the SOZ, indicating decreased FC within the epileptic hemisphere relative to between hemispheres. Conclusions: Assessing alterations in FC using fMRI-ICC map can help localize the SOZ, which has potential as a noninvasive presurgical diagnostic tool to improve surgical outcome. In addition, the method reveals that, in focal epilepsy, both intrahemispheric- and interhemispheric-FC may be altered, in the presence of both regional as well as global network abnormalities.
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Affiliation(s)
- Hyang Woon Lee
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT.
| | - Jagriti Arora
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - Xenophon Papademetris
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - Fuyuze Tokoglu
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - Michiro Negishi
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - Dustin Scheinost
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - Pue Farooque
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - Hal Blumenfeld
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - Dennis D Spencer
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
| | - R Todd Constable
- From the Department of Neurology (H.W.L.), Ewha Womans University School of Medicine and Ewha Medical Research Institute, Seoul, Korea; and Departments of Neurology (H.W.L., P.F., H.B.), Diagnostic Radiology (H.W.L., J.A., X.P., F.T., M.N., R.T.C.), Biomedical Engineering (X.P., D.S., R.T.C.), Neurosurgery (H.B., D.D.S., R.T.C.), and Neurobiology (H.B.), Yale University School of Medicine, New Haven, CT
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57
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Centeno M, Carmichael DW. Network Connectivity in Epilepsy: Resting State fMRI and EEG-fMRI Contributions. Front Neurol 2014; 5:93. [PMID: 25071695 PMCID: PMC4081640 DOI: 10.3389/fneur.2014.00093] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Accepted: 05/25/2014] [Indexed: 12/18/2022] Open
Abstract
There is a growing body of evidence pointing toward large-scale networks underlying the core phenomena in epilepsy, from seizure generation to cognitive dysfunction or response to treatment. The investigation of networks in epilepsy has become a key concept to unlock a deeper understanding of the disease. Functional imaging can provide valuable information to characterize network dysfunction; in particular resting state fMRI (RS-fMRI), which is increasingly being applied to study brain networks in a number of diseases. In patients with epilepsy, network connectivity derived from RS-fMRI has found connectivity abnormalities in a number of networks; these include the epileptogenic, cognitive and sensory processing networks. However, in majority of these studies, the effect of epileptic transients in the connectivity of networks has been neglected. EEG–fMRI has frequently shown networks related to epileptic transients that in many cases are concordant with the abnormalities shown in RS studies. This points toward a relevant role of epileptic transients in the network abnormalities detected in RS-fMRI studies. In this review, we summarize the network abnormalities reported by these two techniques side by side, provide evidence of their overlapping findings, and discuss their significance in the context of the methodology of each technique. A number of clinically relevant factors that have been associated with connectivity changes are in turn associated with changes in the frequency of epileptic transients. These factors include different aspects of epilepsy ranging from treatment effects, cognitive processes, or transition between different alertness states (i.e., awake–sleep transition). For RS-fMRI to become a more effective tool to investigate clinically relevant aspects of epilepsy it is necessary to understand connectivity changes associated with epileptic transients, those associated with other clinically relevant factors and the interaction between them, which represents a gap in the current literature. We propose a framework for the investigation of network connectivity in patients with epilepsy that can integrate epileptic processes that occur across different time scales such as epileptic transients and disease duration and the implications of this approach are discussed.
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Affiliation(s)
- Maria Centeno
- Imaging and Biophysics Unit, Institute of Child Health, University College London , London , UK ; Epilepsy Unit, Great Ormond Street Hospital , London , UK
| | - David W Carmichael
- Imaging and Biophysics Unit, Institute of Child Health, University College London , London , UK ; Epilepsy Unit, Great Ormond Street Hospital , London , UK
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