Zijlmans Maeike, Huiskamp Geertjan M, Leijten Frans S S, Van Der Meij Wil M, Wieneke George, Van Huffelen Alexander C
Department of Clinical Neurophysiology, University Medical Centre, Utrecht, The Netherlands.
J Clin Neurophysiol. 2002 Jun;19(3):183-91. doi: 10.1097/00004691-200206000-00001.
Epileptiform spikes may have a different morphology and signal-to-noise ratio in simultaneously recorded EEGs and magnetoencephalograms (MEGs) that may lead to differences in the identification of spikes if both the modalities are presented separately. Moreover, there are no criteria for MEG spikes. It is unknown to which extent the visual assessment of MEG data yields consistent and meaningful results. Nineteen patients were selected with mesial temporal lobe epilepsy who underwent whole-head simultaneous MEG/EEG. These data were split into MEG and EEG files and were assessed independently by three observers for the occurrence of spikes. Interobserver kappa values were calculated. A mean kappa value greater than 0.5 was taken as a criterion for the presence of unequivocal spikes. Index cases from the resulting four subgroups were studied further. One patient had unequivocal spikes in both modalities, one in EEG only, one in MEG only, and one did not show any unequivocal spike. Spikes on which at least two observers agreed were then subjected to a template match algorithm to test for equal morphology and distribution. Equal spikes were averaged and electrical and magnetic field maps were plotted. Unequivocal spikes were found in both MEG and EEG in one patient, in MEG only in two patients, in EEG only in two patients, and no spikes in either modality were seen in 14 patients. In the four index patients, MEG showed 50 to 80% more spikes than EEG. After averaging identical consensus spikes, MEG spikes revealed a concomitant spike in the EEG, but the reverse was not always true. Even in the patient with MEG and EEG spikes that met all selection criteria, simultaneous field maps showed unexpected inconsistencies. In most patients with mesial temporal lobe epilepsy, there are no unequivocal spikes during MEG/EEG. In some cases, however, experienced electroencephalographers can identify MEG spikes reliably. Because of a better signal-to-noise ratio, more spikes could be identified in MEG than in EEG. Simultaneous MEG/EEG recordings do not simply ensure the best of both, but one modality may improve the identification of spikes in the other. In addition, different aspects of a complex source can be revealed. Our three-step approach to combined data ensures a reproducible selection of spikes for source modeling.
在同步记录的脑电图（EEG）和脑磁图（MEG）中，癫痫样棘波可能具有不同的形态和信噪比，如果分别呈现这两种模态，可能会导致棘波识别上的差异。此外，对于MEG棘波尚无标准。尚不清楚对MEG数据的视觉评估在多大程度上能产生一致且有意义的结果。选择了19例患有内侧颞叶癫痫的患者，他们接受了全脑同步MEG/EEG检查。这些数据被拆分为MEG和EEG文件，并由三名观察者独立评估棘波的出现情况。计算观察者间的kappa值。kappa均值大于0.5被作为明确棘波存在的标准。对所得四个亚组中的索引病例进行了进一步研究。一名患者在两种模态中均有明确的棘波，一名仅在EEG中有，一名仅在MEG中有，一名未显示任何明确的棘波。然后，对至少两名观察者一致认可的棘波应用模板匹配算法，以测试形态和分布是否相同。相同的棘波进行平均，并绘制电场和磁场图。一名患者的MEG和EEG中均发现明确的棘波，两名患者仅在MEG中有，两名患者仅在EEG中有，14名患者在两种模态中均未发现棘波。在这四名索引患者中，MEG显示的棘波比EEG多50%至80%。对相同的一致认可的棘波进行平均后，MEG棘波在EEG中显示出伴随的棘波，但反之并不总是成立。即使在符合所有选择标准的MEG和EEG均有棘波的患者中，同步场图也显示出意外的不一致。在大多数内侧颞叶癫痫患者中，MEG/EEG期间没有明确的棘波。然而，在某些情况下，经验丰富的脑电图专家可以可靠地识别MEG棘波。由于信噪比更好，MEG中可识别的棘波比EEG中更多。同步MEG/EEG记录并非简单地保证两者的最佳效果，而是一种模态可能会改善另一种模态中棘波的识别。此外，可以揭示复杂源的不同方面。我们对组合数据的三步法确保了为源建模可重复地选择棘波。
