MEG evaluation in temporal lobe epilepsy (original) (raw)
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Acta Neurologica Scandinavica, 1994
Is MEG source analysis able to precisely locate the primary focal epileptic activity? 22 patients with pharmacoresistant temporal lobe epilepsy were recorded during presurgical evaluation simultaneously with multichannel MEG/EEG and invasive (subdural) electrodes to evaluate the increase of information gained by MEG concerning the localization of focal epileptic activity and lesions. With this systematic study it should become clearer how often MEG can establish a diagnostic bridge between function and morphology. In addition, MEG localization accuracy of focal epileptic activity was to be validated empirically by invasive EEG recordings and postsurgical outcome. Spikes in the MEG were used for magnetic source localization, and the result was combined with magnetic resonance imaging (MRI). All patients definitely suffered from temporal lobe epilepsy and revealed a structural abnormality in MRI. 17 patients with lesions in the temporal lobe were operated meanwhile and became markedly improved or seizure free. In 7 of 8 patients with a tumor and validated operation outcome, a very close correlation of the 3D-magnetic source localization and the border of the tumor in the brain was found (distance less than 10 mm). In 8 of 9 patients with a temporal/hippocampal atrophy and validated operation outcome, dipoles of epileptiform activity were located within the atrophic lobe.(ABSTRACT TRUNCATED AT 250 WORDS)
Seizure, 2017
In addition to visual analysis digital computerized recording of electrical and magnetic fields by using EEG and MEG opened a new window for research concerning improved understanding of pathophysiology, diagnosis and treatment of epilepsies. In the last 25 years MEG was used more and more in clinical studies concerning localization of focal epileptic activity, functional cortex and network analysis. Simultaneous MEG/EEG recording and analysis offer the use of complimentary information increasing the sensitivity for tracing primary epileptic activity. Combined MEG/Stereo-EEG recordings showed that MEG noninvasively identified regional interictal networks. The current role of MEG for presurgical evaluation with regard to noninvasive localization in MRI normal patients, guiding of invasive electrode implantation and correlation to postoperative outcome after epilepsy surgery is stressed. Challenges and future opportunities for MEG in clinical epileptology are discussed.
Utilization of magnetoencephalography results to obtain favourable outcomes in epilepsy surgery
Brain, 2004
Magnetoencephalography (MEG) is a well-known technique in the presurgical evaluation of epilepsy patients. Like EEG, it can detect and localize epileptic activity. Epilepsy surgery can be used to evaluate MEG source localizations. Resection volumes were determined in 33 epilepsy surgery patients. The resection volume, taken together with the post-operative outcome, was used to evaluate MEG results. The scattering MEG localizations of interictal epileptic activity were represented by an ellipsoidal volume. Using this MEG results ellipsoid, it was demonstrated that a high coverage by the resection volume and a small distance to the resection volume are both correlated to a favourable outcome; in addition, a homogeneous distribution of MEG localizations is correlated to a favourable outcome. This study shows that MEG source localization can help to delineate epileptic activity and, along with other techniques, should be taken into account for epilepsy surgery.
Journal of Clinical Neurophysiology, 2009
States: an estimate from population-based clinical and survey data. Epilepsia. 2000;41:342-351. Bowyer SM, Moran JE, Mason KM, et al. MEG localization of language-specific cortex utilizing MR-FOCUSS. Neurology. 2004;62:2247-2255. Bowyer SM, Moran JE, Weiland BJ, et al. Language laterality determined by MEG mapping with MR-FOCUSS. Epilepsy Behav. 2005;6:235-241. Brenner D, Lipton J, Kaufman L, Williamson SJ. Somatically evoked magnetic fields of the human brain. Science. 1978;199:81-83. Brenner D, Williamson SJ, Kaufman L. Visually evoked magnetic fields of the human brain. Science. 1975;190:480 -482. Brodie MJ. Diagnosing and predicting refractory epilepsy. Acta Neurol Scand Suppl. 2005;181:36 -39. Castillo EM, Simos PG, Wheless JW, et al. Integrating sensory and motor mapping in a comprehensive MEG protocol: clinical validity and replicability. Neuroimage. 2004;21:973-983. Cohen D. Magnetoencephalography: evidence of magnetic fields produced by alpha rhythm currents. Science. 1968;161:784 -786. Cohen D. Magnetoencephalography: detection of the brain's electrical activity with a superconducting magnetometer. Science. 1972;175:664 -666. Duffner F, Freudenstein D, Schiffbauer H, et al. Combining MEG and MRI with neuronavigation for treatment of an epileptiform spike focus in the precentral region: a technical case report. Surg Neurol. 2003;59:40 -45. Ebersole JS. Magnetoencephalography/magnetic source imaging in the assessment of patients with epilepsy. Epilepsia. 1997;38:S1-S5. Engel J Jr. A greater role for surgical treatment of epilepsy: why and when? Epilepsy Curr. 2003;3:37-40. Engel J Jr. Surgical treatment for epilepsy: too little, too late? JAMA. 2008;300: 2548 -2550. Engel J Jr, Shewmon DA. Overview: who should be considered a surgical candidate? In: Engel J Jr, ed. Surgical Treatment of the Epilepsies. 2nd ed. New York: Raven Press; 1993:23-34. Engel J Jr, Wiebe S, French J, et al. Practice parameter: temporal lobe and localized neocortical resections for epilepsy. Epilepsia. 2003;44:741-751. Firsching R, Bondar I, Heinze HJ, et al. Practicability of magnetoencephalography-guided neuronavigation. Neurosurg Rev. 2002;25:73-78. Fischer MJ, Scheler G, Stefan H. Utilization of magnetoencephalography results to obtain favourable outcomes in epilepsy surgery. Brain. 2005;128(Pt 1):153-157. Flagg EJ, Cardy JE, Roberts W, Roberts TP. Language lateralization development in children with autism: insights from the late field magnetoencephalogram. Neurosci Lett. 2005;386:82-87. Ganslandt O, Buchfelder M, Hastreiter P, et al. Magnetic source imaging supports clinical decision making in glioma patients. Clin Neurol Neurosurg. 2004;107:20 -26. Ganslandt O, Fahlbusch R, Nimsky C, et al. Functional neuronavigation with magnetoencephalography: outcome in 50 patients with lesions around the motor cortex. J Neurosurg. 1999;91:73-79. Godey B, Schwartz D, de Graaf JB, et al. Neuromagnetic source localization of auditory evoked fields and intracerebral evoked potentials: a comparison of data in the same patients. Clin Neurophysiol. 2001;112:1850 -1859. Grover KM, Bowyer SM, Rock J, et al. Retrospective review of MEG visual evoked hemifield responses prior to resection of temporo-parieto-occipital lesions. J Neurooncol. 2006;77:161-166. Grummich P, Nimsky C, Pauli E, et al. Combining fMRI and MEG increases the reliability of presurgical language localization: a clinical study on the difference between and congruence of both modalities. Neuroimage. 2006; 32:1793-1803. Hamalainen M, Hari R, Ilmoniemi RJ, et al. Magnetoencephalography-theory, instrumentation, and applications to noninvasive studies of the working humans brain. Rev Mod Phys. 1993;65:413-497. Hari R, Joutsiniemi SL, Sarvas J. Spatial resolution of neuromagnetic records: theoretical calculations in a spherical model.
Magnetoencephalography in Focal Epilepsy
Epilepsia, 2000
The introduction of whole-head magnetoencephalographic (MEG) systems facilitating simultaneous recording from the entire brain surface has led to a major breakthrough in the MEG evaluation of epilepsy patients. MEG localizations estimates of the interictal spike zone showed excellent agreement with invasive electrical recordings and were useful to clarify the spatial relationship of the irritative zone and structural lesions. MEG appears to be especially useful for study of patients with neocortical epilepsy, and helped to guide the placement of subdural grid electrodes in patients with nonlesional epilepsies. MEG could differentiate between patients with mesial and lateral temporal seizure onset. Spike propagation in the temporal lobe and the spatio-temporal organization of the interictal spike complex could be studied noninvasively. MEG was useful to delineate essential brain regions before surgical procedures adjacent to the central fissure. MEG appears to be more sensitive than scalp EEG for detection of epileptic discharges arising from the lateral neocortex, whereas only highly synchronized discharges arising from mesial temporal structures could be recorded. A major limitation of MEG has been the recording of seizures because long-term recordings cannot be performed on a routine basis with the available technology. Because MEG and EEG yield both complementary and confirmatory information, combined MEG-EEG recordings in conjunction with advanced source modeling techniques should improve the noninvasive evaluation of epilepsy patients and further reduce the need for invasive procedures.
Does magnetoencephalography add to scalp video-EEG as a diagnostic tool in epilepsy surgery?
Neurology, 2004
Objective:The authors evaluated the sensitivity and selectivity of interictal magnetoencephalography (MEG) versus prolonged ictal and interictal scalp video-electroencephalography (V-EEG) in order to identify patient groups that would benefit from preoperative MEG testing.Methods:The authors evaluated 113 consecutive patients with medically refractory epilepsy who underwent surgery. The epileptogenic region predicted by interictal and ictal V-EEG and MEG was defined in relation to the resected area as perfectly overlapping with the resected area, partially overlapping, or nonoverlapping.Results:The sensitivity of a 30-minute interictal MEG study for detecting clinically significant epileptiform activity was 79.2%. Using MEG, we were able to localize the resected region in a greater proportion of patients (72.3%) than with noninvasive V-EEG (40%). MEG contributed to the localization of the resected region in 58.8% of the patients with a nonlocalizing V-EEG study and 72.8% of the pati...