Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia.
Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia; ARC Training Centre for Innovation in Biomedical Imaging Technology, The University of Queensland, Brisbane, Australia.
Neuroimage Clin. 2020;28:102440. doi: 10.1016/j.nicl.2020.102440. Epub 2020 Sep 18.
The irritative zone - the area generating epileptic spikes - can be studied non-invasively during the interictal period using Electrical Source Imaging (ESI) and simultaneous electroencephalography-functional magnetic resonance imaging (EEG-fMRI). Although the techniques yield results which may overlap spatially, differences in spatial localization of the irritative zone within the same patient are consistently observed. To investigate this discrepancy, we used Blood Oxygenation Level Dependent (BOLD) functional connectivity measures to examine the underlying relationship between ESI and EEG-fMRI findings.
Fifteen patients (age 20-54), who underwent presurgical epilepsy investigation, were scanned using a single-session resting-state EEG-fMRI protocol. Structural MRI was used to obtain the electrode localisation of a high-density 64-channel EEG cap. Electrical generators of interictal epileptiform discharges were obtained using a distributed local autoregressive average (LAURA) algorithm as implemented in Cartool EEG software. BOLD activations were obtained using both spike-related and voltage-map EEG-fMRI analysis. The global maxima of each method were used to investigate the temporal relationship of BOLD time courses and to assess the spatial similarity using the Dice similarity index between functional connectivity maps.
ESI, voltage-map and spike-related EEG-fMRI methods identified peaks in 15 (100%), 13 (67%) and 8 (53%) of the 15 patients, respectively. For all methods, maxima were localised within the same lobe, but differed in sub-lobar localisation, with a median distance of 22.8 mm between the highest peak for each method. The functional connectivity analysis showed that the temporal correlation between maxima only explained 38% of the variance between the time course of the BOLD response at the maxima. The mean Dice similarity index between seed-voxel functional connectivity maps showed poor spatial agreement.
Non-invasive methods for the localisation of the irritative zone have distinct spatial and temporal sensitivity to different aspects of the local cortical network involved in the generation of interictal epileptiform discharges.
利用电源成像（ESI）和同步脑电图-功能磁共振成像（EEG-fMRI），在发作间期对致痫区（产生癫痫棘波的区域）进行非侵入性研究。尽管这些技术的结果可能在空间上重叠，但在同一患者中，致痫区的空间定位差异是一致观察到的。为了研究这种差异，我们使用血氧水平依赖（BOLD）功能连接测量来检查 ESI 和 EEG-fMRI 结果之间的潜在关系。
15 名（年龄 20-54 岁）接受术前癫痫研究的患者接受了单次静息状态 EEG-fMRI 方案扫描。结构 MRI 用于获取高密度 64 通道 EEG 帽的电极定位。使用分布式局部自回归平均（LAURA）算法（如 Cartool EEG 软件中实现的）获取间歇性癫痫样放电的电发生器。使用与棘波相关和电压图 EEG-fMRI 分析获得 BOLD 激活。使用每种方法的全局最大值来研究 BOLD 时程的时间关系，并使用功能连接图之间的 Dice 相似性指数评估空间相似性。
ESI、电压图和与棘波相关的 EEG-fMRI 方法分别在 15 名（100%）、13 名（67%）和 8 名（53%）患者中识别出峰值。对于所有方法，最大值均位于同一叶内，但在亚叶定位上存在差异，每种方法的最高峰值之间的中位数距离为 22.8mm。功能连接分析表明，最大值之间的时间相关性仅解释了 BOLD 响应时程之间方差的 38%。种子体素功能连接图之间的平均 Dice 相似性指数显示出较差的空间一致性。
用于致痫区定位的非侵入性方法对涉及产生间歇性癫痫样放电的局部皮质网络的不同方面具有不同的空间和时间敏感性。
