PURPOSE: To test the sensitivity of extracranial magnetoencephalography (MEG) for epileptic spikes in different cerebral sites. METHODS: We simultaneously recorded MEG and electrocorticography (ECoG) by using subdural electrodes with 1-cm interelectrode distances for one patient with lateral frontal epilepsy and one patient with basal temporal epilepsy. We analyzed MEG spikes associated with ECoG spikes and compared the maximal amplitude and number of electrodes involved. We estimated and evaluated the locations and moments of the equivalent current dipoles (ECDs) of MEG spikes. RESULTS: In patient 1, MEG detected 100 (53%) of 188 ECoG lateral frontal spikes, including 31 (46%) of 67 spikes that activated three subdural electrodes. MEG spike amplitudes correlated with ECoG spike amplitudes and the number of electrodes activated (p < 0.01). ECDs were perpendicular to the superior frontal sulcus. In patient 2, MEG detected 31 (26%) of 121 ECoG basal temporal spikes, but none that activated only three subdural electrodes. ECDs were localized in the entorhinal and parahippocampal gyri, oriented perpendicular to those basal temporal cortical surfaces. The ECD strength was 136.6 +/- 71.5 nAm in the frontal region, but 274.5 +/- 150.6 nAm in the temporal region (p < 0.01). CONCLUSIONS: When lateral frontal ECoG spikes extend >3 cm2 across the fissure, MEG can detect >50%, correlating with spatial activation and voltage. In the basal temporal region, MEG requires higher-amplitude discharges over a more extensive area. MEG shows a significantly higher sensitivity to lateral convexity epileptic discharges than to discharges in isolated deep basal temporal regions.
PURPOSE: To test the sensitivity of extracranial magnetoencephalography (MEG) for epileptic spikes in different cerebral sites. METHODS: We simultaneously recorded MEG and electrocorticography (ECoG) by using subdural electrodes with 1-cm interelectrode distances for one patient with lateral frontal epilepsy and one patient with basal temporal epilepsy. We analyzed MEG spikes associated with ECoG spikes and compared the maximal amplitude and number of electrodes involved. We estimated and evaluated the locations and moments of the equivalent current dipoles (ECDs) of MEG spikes. RESULTS: In patient 1, MEG detected 100 (53%) of 188 ECoG lateral frontal spikes, including 31 (46%) of 67 spikes that activated three subdural electrodes. MEG spike amplitudes correlated with ECoG spike amplitudes and the number of electrodes activated (p < 0.01). ECDs were perpendicular to the superior frontal sulcus. In patient 2, MEG detected 31 (26%) of 121 ECoG basal temporal spikes, but none that activated only three subdural electrodes. ECDs were localized in the entorhinal and parahippocampal gyri, oriented perpendicular to those basal temporal cortical surfaces. The ECD strength was 136.6 +/- 71.5 nAm in the frontal region, but 274.5 +/- 150.6 nAm in the temporal region (p < 0.01). CONCLUSIONS: When lateral frontal ECoG spikes extend >3 cm2 across the fissure, MEG can detect >50%, correlating with spatial activation and voltage. In the basal temporal region, MEG requires higher-amplitude discharges over a more extensive area. MEG shows a significantly higher sensitivity to lateral convexity epileptic discharges than to discharges in isolated deep basal temporal regions.
Authors: Hiroatsu Murakami; Zhong I Wang; Ahmad Marashly; Balu Krishnan; Richard A Prayson; Yosuke Kakisaka; John C Mosher; Juan Bulacio; Jorge A Gonzalez-Martinez; William E Bingaman; Imad M Najm; Richard C Burgess; Andreas V Alexopoulos Journal: Brain Date: 2016-11-01 Impact factor: 13.501
Authors: Karin L de Gooijer-van de Groep; Frans S S Leijten; Cyrille H Ferrier; Geertjan J M Huiskamp Journal: Hum Brain Mapp Date: 2012-03-19 Impact factor: 5.038
Authors: Z I Wang; S E Jones; A J Ristic; C Wong; Y Kakisaka; K Jin; F Schneider; J A Gonzalez-Martinez; J C Mosher; D Nair; R C Burgess; I M Najm; A V Alexopoulos Journal: Epilepsy Res Date: 2012-03-04 Impact factor: 3.045
Authors: Naoaki Tanaka; Matti S Hämäläinen; Seppo P Ahlfors; Hesheng Liu; Joseph R Madsen; Blaise F Bourgeois; Jong Woo Lee; Barbara A Dworetzky; John W Belliveau; Steven M Stufflebeam Journal: Neuroimage Date: 2009-12-16 Impact factor: 6.556
Authors: Yosuke Kakisaka; Rafeed Alkawadri; Zhong I Wang; Rei Enatsu; John C Mosher; Anne-Sophie Dubarry; Andreas V Alexopoulos; Richard C Burgess Journal: Epileptic Disord Date: 2013-03 Impact factor: 1.819