1 Aix-Marseille Université, INSERM, Institut de Neurosciences des Systèmes , Marseille, France .
2 AP-HM, Hôpital de la Timone, Service de Neurophysiologie Clinique, Marseille, France .
Brain Connect. 2016 Sep;6(7):530-9. doi: 10.1089/brain.2015.0397. Epub 2016 Jul 22.
The reference electrophysiological pattern at seizure onset is the "rapid discharge," as visible on intracerebral electroencephalography (EEG). This discharge typically corresponds to a decrease of synchrony across brain areas. In contrast, the preictal period can exhibit patterns of increased synchrony, which can be quantified by network measures. Our objective was to compare preictal synchrony with a quantification of the rapid discharge as provided by the epileptogenicity index (EI). We investigated 24 seizures from 12 patients recorded by stereotaxic EEG (SEEG). Seizures were classified visually as containing preictal synchrony or not. We computed pairwise nonlinear correlation (h(2)) across channels in the 8 sec preceding the rapid discharge. The sum of ingoing and outgoing links (IN and OUT node strength), as well as the sum of all links (total strength, TOT) were computed for each region. We tested several filtering schemes, and quantified the capacity of each strength measure to serve as a detector of regions with high EI values using a receiver operating characteristic (ROC) analysis. We found that the best correspondence between node strength and EI was obtained for the OUT and TOT measures, for signals filtered in the 15-40 Hz band-that is, for the band corresponding to the spiky part of epileptic discharges. In agreement with these results, we also found that the ROC results were improved when considering only seizures with visible synchronous patterns in the preictal period. Our results suggest that measuring strength of preictal connectivity graphs can bring useful clinical information on the epileptogenic zone.
发作起始时的参考电生理模式是“快速放电”，在颅内脑电图（EEG）上可见。这种放电通常对应于大脑区域之间同步性的降低。相比之下，发作前期可能表现出同步性增加的模式，可以通过网络测量来量化。我们的目标是比较发作前期的同步性与癫痫发作指数（EI）提供的快速放电的量化。我们研究了 12 名患者的 24 次立体定向脑电图（SEEG）记录的发作。发作通过视觉分类为包含或不包含发作前期同步性。我们计算了在快速放电前 8 秒内通道之间的成对非线性相关（h(2)）。对于每个区域，计算传入和传出链路的总和（IN 和 OUT 节点强度）以及所有链路的总和（总强度，TOT）。我们测试了几种滤波方案，并使用接收者操作特征（ROC）分析量化了每种强度测量作为高 EI 值区域的检测器的能力。我们发现，在 OUT 和 TOT 测量中，节点强度与 EI 之间的最佳对应关系是在 15-40 Hz 频段滤波的信号中获得的，即与癫痫放电的尖峰部分相对应的频段。与这些结果一致，我们还发现，当仅考虑发作前期有可见同步模式的发作时，ROC 结果得到了改善。我们的结果表明，测量发作前期连接图的强度可以为致痫区提供有用的临床信息。
