Tangential and Radial Epileptic Spike Activity: Different Sensitivity in EEG and MEG
Tangential and Radial Epileptic Spike Activity: Different Sensitivity in EEG and MEG
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DOI：
10.1097/wnp.0b013e3182624491
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发表时间：
2012-08-01
影响因子：
2.4
通讯作者：
Eichardt, Roland
中科院分区：
文献类型：
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作者：
Haueisen, Jens;Funke, Michael;Eichardt, Roland
目的：对癫痫患者的观察表明，间隔期峰有时仅在脑电图（EEG）中可见，有时仅在脑磁图（MEG）中可见。基于分析模型的脑电图和脑磁图的理论灵敏度不能很容易地解释这一观察结果。在这种情况下，我们的目的是研究径向和切向尖峰活动的方向敏感性在数值模拟中使用真实的头部模型。方法：对4名志愿者的12个脑区在不同方向和背景活动下的模拟峰值进行信噪比（SNR）计算。通过调整分布在大脑皮层的几千个偶极子的振幅，模拟了不同水平的背景活动。结果：对于一个固定的现实背景活动，我们发现，当脉冲方向偏离切线方向不超过bbb30度时，MEG峰值的信噪比更高。相比之下，我们发现脑电图峰值偏离径向不超过45度的信噪比更高。选择性地增加径向背景活动，脑电图对径向定向峰的敏感性降低；当切向背景活动选择性增加时，脑磁图对切向定向峰的敏感性降低。结论：我们的模拟为脑电图和脑磁图在癫痫峰检测方面的临床观察差异提供了可能的解释。通过结合分析脑电图和脑磁图数据，可以改进癫痫峰检测。
Objective: Observations in epileptic patients show that interictal spikes are sometimes only visible in electroencephalography (EEG) and sometimes only in magnetoencephalography (MEG). This observation cannot readily be explained by the theoretical sensitivities of EEG and MEG based on analytical models. In this context, we aimed to study the directional sensitivity of radial and tangential spike activity in numerical simulations using realistic head models.Methods: We calculated the signal-to-noise ratio (SNR) of simulated spikes at varying orientations and with varying background activity in 12 brain regions in 4 volunteers. Different levels of background activity were modeled by adjusting the amplitudes of several thousand dipoles distributed in the cortex.Results: For a fixed realistic background activity, we found a higher SNR for MEG spikes for spike orientations that deviated not >30 degrees from the tangential direction. In contrast, we found a higher SNR for EEG spikes that deviated not >45 degrees from the radial direction. When the radial background activity was selectively increased, the sensitivity of EEG for radially oriented spikes decreased; when the tangential background activity selectively increased, the sensitivity of MEG for tangentially oriented spikes was decreased.Conclusions: Our simulations provide a possible explanation for the clinically observed differences in epileptic spike detection between EEG and MEG. Epileptic spike detection can be improved by analyzing a combination of EEG and MEG data.