Detection and Significance of Focal, Interictal Slow Wave Activity for Localization of the Primary Epileptogenic Region Using Magnetoencephalography.
Abstract number :
3.172
Submission category :
Year :
2001
Submission ID :
191
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
H. Ishibashi, M.D.,Ph.D; P.G. Simos, Ph.D; E.M. Castillo, Ph.D; W.W. Maggio, MD; J.W. Wheless, MD; H.L. Kim, MD; V. Venkataraman, MD; D.K. Sanders, Ph.D; J.I. Breier, Ph.D; W. Zhang, M.D.,Ph.D; R.N. Davis, M.A; A.C. Papanicolaou, Ph.D
RATIONALE: Magnetoencephalography (MEG) is a novel noninvasive technique for presurgical localization of the epileptogenic zone in patients with epilepsy. The presence of focal slowing on the electroencephalography is an additional indicator of underlying pathology in intractable mesial temporal lobe epilepsy (MTLE). The present study was aimed at investigating the significance of focal slow wave and interictal spike activity detected by MEG in 29 patients with MTLE, not associated with structural brain lesions. All of the patients subsequently underwent resective surgery.
METHODS: Equivalent single dipole modeling was applied to focal low frequency magnetic activity (LFMA) and interictal paroxysmal activity. We defined lateralized LFMA as runs of rhythmic activity with frequencies lower than 7-Hz over the temporal area, which were easily distinguished from background rhythm.
RESULTS: Seventeen patients (58.6%) had lateralized LFMA, which was always ipsilateral to the resection and of maximal amplitude over the temporal area. Dipolar sources of magnetic flux computed during the slow wave trains were found in the majority of cases to localize to the posterior superior temporal region, and occasionally, over the mesial temporal structures that were subsequently resected. LFMA and interictal MEG spike sources were never in disagreement with respect to lateralization.
CONCLUSIONS: LFMA in patients with MTLE, not associated with a mass lesion, is topographically related to the epileptogenic area and therefore has a reliable lateralizing, and possibly localizing value. Although focal slowing of the EEG background activity is generally considered to be a non-specific sign of functional disturbance, interictal LFMA in MTLE should be conceptualized as a distinct electrographic phenomenon that is directly related to the epileptogenic abnormality. Analyzing the interictal MEG distribution of LFMA and sharp activity improves the diagnostic utility of MEG in patients with suspected temporal lobe epilepsy who are undergoing surgical evaluation.
Support: This work was partly supported by NIH grant RO1 NS37941 to Andrew C. Papanicolaou.