INSERM UMR1106, Institut de Neurosciences des Systèmes, Marseille, France,
Brain Topogr. 2014 Jan;27(1):192-6. doi: 10.1007/s10548-013-0317-7. Epub 2013 Sep 5.
Interictal or ictal events in partial epilepsies may project on scalp EEG contralaterally to the side of the epileptogenic lesion. Such paradoxical lateralization can be observed in case of para-sagittal generators, and is likely due to the spatial orientation of the generator, presenting an oblique projection towards the midline. We present here a case of medial occipital epilepsy investigated using EEG, MEG and stereoelectroencephalography (SEEG). MRI displayed a focal cortical dysplasia in the superior margin of the right calcarine fissure. SEEG demonstrated bilateral medial occipital interictal spikes, with an inversion of polarity at the level of the lesion and a contralateral propagation occurring in 10 ms. Interictal iterative EEG cartographies showed a large posterior field, with a maximum contralateral to the initial generator (EEG paradoxical lateralization). With the same number of channels, interictal iterative MEG cartographies were more precise and more complex than EEG ones, indicating an onset accurately lateralized. A few milliseconds later, MEG cartographies were quadripolar, thus indicating two homotopic active generators. These MEG and EEG cartographies have been reproduced using BESA dipole simulator. Relative merits of MEG and EEG are still debated. With 151 channels, MEG source localizations indicated the right medial occipital area, as demonstrated by SEEG. An investigation with a corresponding number of EEG channels was not performed. After a down sampling to 64 sensors, this precision was lost. MEG and EEG source localization results, both with 64 channels, were quite comparable, indicating both medial occipital areas. However, a careful analysis of MEG/EEG iterative cartographies, performed with the same number of channels in both modalities, demonstrated that, in this configuration, MEG sensitivity was superior to the EEG one, allowing separating two medial occipital sources, characterized in SEEG by a time delay of 10 ms.
部分性癫痫的发作间期或发作期事件可能会向致痫病变对侧的头皮 EEG 投射。这种反常的偏侧化可以在矢状旁发生器的情况下观察到，这可能是由于发生器的空间取向，呈现出向中线的斜向投射。我们在此介绍一个使用 EEG、MEG 和立体脑电图（SEEG）进行研究的内侧枕叶癫痫病例。MRI 显示右侧距状裂上缘有局灶性皮质发育不良。SEEG 显示双侧内侧枕叶发作间期棘波，在病变水平反转极性，对侧在 10 毫秒内传播。发作间期迭代 EEG 图谱显示一个大的后区，最大的位于初始发生器的对侧（EEG 反常偏侧化）。使用相同数量的通道，发作间期迭代 MEG 图谱比 EEG 图谱更精确和复杂，表明起始准确偏侧化。几毫秒后，MEG 图谱为四极，表明有两个同型的活跃发生器。这些 MEG 和 EEG 图谱已使用 BESA 偶极子模拟器进行再现。MEG 和 EEG 的相对优势仍在争论中。使用 151 个通道，MEG 源定位表明右侧内侧枕叶区域，正如 SEEG 所示。未进行相应数量的 EEG 通道的调查。在向下采样至 64 个传感器后，这种精度就丢失了。使用 64 个通道的 MEG 和 EEG 源定位结果相当可比，均表明内侧枕叶区域。然而，通过对 MEG/EEG 迭代图谱进行仔细分析，在两种模式下使用相同数量的通道进行分析，表明在这种配置下，MEG 的灵敏度优于 EEG，允许分离两个内侧枕叶源，在 SEEG 中，这两个源的时间延迟为 10 毫秒。
