Badier Jean-Michel, Bénar Christian-George, Woodman Michael, Cruto Catarina, Chauvel Patrick, Bartolomei Fabrice, Gavaret Martine
Institut de Neurosciences des Systèmes, INSERM UMR 1106, 13005, Marseille, France.
Faculté de Médecine, Aix Marseille Université, 13005, Marseille, France.
Brain Topogr. 2016 Jan;29(1):182-92. doi: 10.1007/s10548-015-0445-3. Epub 2015 Aug 12.
Ictal MEG recordings constitute rare data. The objective of this study was to evaluate ictal magnetic source localization (MSI), using two algorithms: linearly constrained minimum variance (LCMV), a beamforming technique and equivalent current dipole (ECD). Ictal MSI was studied in six patients. Three of them were undergoing post-operative re-evaluation. For all patients, results were validated by the stereoelectroencephalographic (SEEG) definition of the epileptogenic zone (EZ). EZ was quantified using the epileptogenicity index (EI) method, which accounts for both the propensity of a brain area to generate rapid discharges and the time for this area to become involved in the seizure. EI values range from 0 (no epileptogenicity) to 1 (maximal epileptogenicity). Levels of concordance between ictal MSI and EZ were determined as follows: A: ictal MSI localized the site whose value EI = 1, B: MSI localized a part of the EZ (not corresponding to the maximal value of EI = 1), C: a region could be identified on ictal MSI but not on SEEG, D: a region could be identified on SEEG but not on MSI, E: different regions were localized on MSI and SEEG. Ictal MEG pattern consisted of rhythmic activities between 10 and 20 Hz for all patients. For LCMV (first maxima), levels of concordance were A (two cases), B (two cases) and E (two cases). For ECD fitted on each time point separately (location characterized by the best goodness-of-fit value), levels of concordance were A (one case), B (one case), D (three cases) and E (one case). For ECD calculated for the whole time window, levels of concordance were A (two cases) and D (four cases). Source localization methods performed on rhythmic patterns can localize the EZ as validated by SEEG. In terms of concordance, LCMV was superior to ECD. In some cases, LCMV allows extraction of several maxima that could reflect ictal dynamics. In a medial temporal lobe epilepsy case, ictal MSI indicated an area of delayed propagation and was non-contributory to the presurgical assessment.
发作期脑磁图记录构成了罕见的数据。本研究的目的是使用两种算法评估发作期磁源定位（MSI）：线性约束最小方差（LCMV），一种波束形成技术和等效电流偶极子（ECD）。对6例患者进行了发作期MSI研究。其中3例正在接受术后重新评估。对于所有患者，结果均通过癫痫发作起源区（EZ）的立体脑电图（SEEG）定义进行验证。使用癫痫发作指数（EI）方法对EZ进行量化，该方法既考虑了脑区产生快速放电的倾向，也考虑了该区域参与癫痫发作的时间。EI值范围从0（无癫痫发作性）到1（最大癫痫发作性）。发作期MSI与EZ之间的一致性水平确定如下：A：发作期MSI定位了EI值=1的部位；B：MSI定位了EZ的一部分（不对应于EI=1的最大值）；C：在发作期MSI上可以识别出一个区域，但在SEEG上不能识别；D：在SEEG上可以识别出一个区域，但在MSI上不能识别；E：在MSI和SEEG上定位的区域不同。所有患者的发作期脑磁图模式均由10至20赫兹的节律性活动组成。对于LCMV（第一个最大值），一致性水平为A（2例）、B（2例）和E（2例）。对于在每个时间点单独拟合的ECD（以最佳拟合值表征的位置），一致性水平为A（1例）、B（1例）、D（3例）和E（1例）。对于在整个时间窗口计算的ECD，一致性水平为A（2例）和D（4例）。对节律性模式进行的源定位方法可以定位经SEEG验证的EZ。在一致性方面，LCMV优于ECD。在某些情况下，LCMV允许提取几个最大值，这些最大值可以反映发作期动力学。在一例内侧颞叶癫痫病例中，发作期MSI显示出一个延迟传播区域，对术前评估没有帮助。
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