Neuromagnetic Characterization of the Interictal Spike Complex in Mesial Temporal Lobe Epilepsy
Abstract number :
1.236
Submission category :
Year :
2001
Submission ID :
2971
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
E. Pataraia, MD, University Clinic of Neurology, Vienna, Austria; G. Lindinger, PHD, University Clinic of Neurology, Vienna, Austria; L. Deecke, MD, University Clinic of Neurology, Vienna, Austria; C. Baumgartner, MD, University Clinic of Neurology, Vienn
RATIONALE: The syndrome of mesial temporal lobe epilepsy (MTLE) represents the most frequent form of therapy resistant focal epilepsy. We assessed the value of combined MEG and EEG in patients with clearly defined MTLE to better characterize the epileptogenic zone.
METHODS: Simultaneous MEG and scalp-EEG recordings were performed in 30 patients with MTLE for a duration of 2-3 hours. MEG was performed with a 143 channel whole-head MEG (CTF Systems Inc., Port Coquitlam, B.C. Canada) in a large magnetically shielded room (Vacuumschmelze GmbH, Hanau, Germany). Scalp-EEG was recorded from 23 - 26 gold-disk electrodes placed according the International 10-20 System with additional basal temporal electrodes. We calculated isopotential and isofield maps using spherical spline interpolation. EEG and MEG spikes were subjected to a separate dipole source analysis. We calculated single equivalent dipoles at the peak of the interictal spike complex using the BESA software for the EEG data (Megis, Munich, Germany) and the CTF Systems software for the MEG data. Finally we imaged the best fitting dipoles on MRI.
RESULTS: During the combined scalp-EEG/MEG recording session interictal spikes could be recorded in 14 out of the 30 patients (= 47%). All spike dipoles could be localized to the temporal lobe. We observed two types of dipole orientations: 8 patients showed so-called [soquote]anterior (oblique) vertical dipoles[scquote] and in the other 6 patients so-called [soquote]mesial (oblique) horizontal dipoles[scquote] were recorded. Dipole orientation was consistent within a given patient across different spikes in both MEG and in EEG. 9 of 14 patients (64%) with spikes during the MEG-sessions underwent surgical treatment and have been seizure-free for an average of 20 months (range: 4-40 months).
CONCLUSIONS: MEG and EEG dipole modeling could provide a noninvasive method to better characterize the epileptogenic zone in patients with MTLE and could successfully differentiate between patients with regional mesial and more diffuse seizure onset zones. Because MEG and EEG yield both complementary and confirmatory information, combined MEG-EEG recordings in conjunction with advanced source modeling techniques improve the non-invasive evaluation of epilepsy patients.
Support: Supported by the Fonds zur Förderung der wissenschaftlichen Forschung österreichs (project 12697-MED).