Magnetoencephalography Mislocalizes Interictal Epileptogenic Activity in Mesial Temporal Epilepsy.
Abstract number :
B.02
Submission category :
Year :
2001
Submission ID :
2301
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
A.M. Goldman, MD,PhD, Neurology, University of Texas, Houston, TX; J.W. Wheless, MD, Neurology and Pediatrics, University of Texas, Houston, TX; V. Venkataraman, MD, Neurology, University of Texas, Houston, TX; H.L. Kim, MD, Neurology, University of Texas
RATIONALE: Temporal lobe epilepsy (TLE) is frequently amenable to surgical treatment that may be curative. Noninvasive methods capable of a reliable localization of seizure foci are highly desirable. Magnetoencephalography (MEG) is being used as a promising tool towards definition of the epileptogenic zone. The purpose of this study was to evaluate the accuracy of MEG in localizing epileptogenic foci in patients with documented mesial TLE(MTLE).
METHODS: We reviewed charts of all patients that underwent presurgical evaluation in our Epilepsy Monitoring Unit between January 1997 and January 2000. Selected patients had unequivocal mesial temporal lobe seizure onset as detected by subdural strips(6), depth electrodes(11),sphenoidal (2),and T1,T2 electrodes(2). All of the selected patients underwent preoperative interictal MEG evaluation using 148 channel whole head magnetometer with simultaneous EEG recording.
RESULTS: We identified 21 MTLE patients who underwent temporal lobectomy. No interictal sources were detected in 2 patients. MEG was not lateralizing in 1 and was lateralizing but not localizing in 2 cases.Well defined MEG sources were identified and correctly lateralized to the affected hemisphere in 16 patients.In 14 with mesial temporal lobe origin of seizures all of the interictal source dipoles were mislocalized by MEG, most frequently to the superior temporal gyrus. 2 patients had lateral temporal seizure onset. Location of their interictal source dipoles was also in the superior temporal gyrus.
CONCLUSIONS: Our results indicate that MEG may falsely localize MTLE, usually showing a dipole over the superior temporal gyrus. MEG may show better localization of epileptogenic sources originating from lateral neocortex. The epileptologist must understand this and not be discouraged from continuing the surgical evaluation.