Manoochehri Mana, Mahmoudzadeh Mahdi, Bourel-Ponchel Emilie, Wallois Fabrice
National Institute of Health and Medical Research Unit 1105, Research Group on Multimodal Analysis of Brain Function, University of Picardie Jules Verne, University Hospital Center South, Amiens, France.
Epilepsia. 2017 Dec;58(12):2064-2072. doi: 10.1111/epi.13926. Epub 2017 Oct 16.
Interictal epileptic spikes (IES) represent a signature of the transient synchronous and excessive discharge of a large ensemble of cortical heterogeneous neurons. Epilepsy cannot be reduced to a hypersynchronous activation of neurons whose functioning is impaired, resulting on electroencephalogram (EEG) in epileptic seizures or IES. The complex pathophysiological mechanisms require a global approach to the interactions between neural synaptic and nonsynaptic, vascular, and metabolic systems. In the present study, we focused on the interaction between synaptic and nonsynaptic mechanisms through the simultaneous noninvasive multimodal multiscale recording of high-density EEG (HD-EEG; synaptic) and fast optical signal (FOS; nonsynaptic), which evaluate rapid changes in light scattering related to changes in membrane configuration occurring during neuronal activation of IES.
To evaluate changes in light scattering occurring around IES, three children with frontal IES were simultaneously recorded with HD-EEG and FOS. To evaluate change in synchronization, time-frequency representation analysis of the HD-EEG was performed simultaneously around the IES. To independently evaluate our multimodal method, a control experiment with somatosensory stimuli was designed and applied to five healthy volunteers.
Alternating increase-decrease-increase in optical signals occurred 200 ms before to 180 ms after the IES peak. These changes started before any changes in EEG signal. In addition, time-frequency domain EEG analysis revealed alternating decrease-increase-decrease in the EEG spectral power concomitantly with changes in the optical signal during IES. These results suggest a relationship between (de)synchronization and neuronal volume changes in frontal lobe epilepsy during IES.
These changes in the neuronal environment around IES in frontal lobe epilepsy observed in children, as they have been in rats, raise new questions about the synaptic/nonsynaptic mechanisms that propel the neurons to hypersynchronization, as occurs during IES. We further demonstrate that this noninvasive multiscale multimodal approach is suitable for studying the pathophysiology of the IES in patients.
发作间期癫痫样放电（IES）代表大量皮质异质性神经元短暂同步且过度放电的特征。癫痫不能简单归结为功能受损神经元的超同步激活，这种激活在脑电图（EEG）上表现为癫痫发作或IES。复杂的病理生理机制需要对神经突触和非突触、血管及代谢系统之间的相互作用采用整体研究方法。在本研究中，我们通过同时进行高密度脑电图（HD - EEG；突触）和快速光信号（FOS；非突触）的非侵入性多模态多尺度记录，聚焦于突触和非突触机制之间的相互作用，HD - EEG和FOS可评估与IES神经元激活期间膜结构变化相关的光散射快速变化。
为评估IES周围发生的光散射变化，对三名患有额叶IES的儿童同时进行HD - EEG和FOS记录。为评估同步性变化，在IES周围同时对HD - EEG进行时频表征分析。为独立评估我们的多模态方法，设计了体感刺激对照实验并应用于五名健康志愿者。
在IES峰值前200毫秒至峰值后180毫秒期间，光信号出现交替的增减变化。这些变化在EEG信号出现任何变化之前就已开始。此外，时频域EEG分析显示，在IES期间，EEG频谱功率伴随光信号变化出现交替的增减变化。这些结果表明，在额叶癫痫发作间期，同步化（去同步化）与神经元体积变化之间存在关联。
在儿童中观察到的额叶癫痫发作间期IES周围神经元环境的这些变化，与在大鼠中观察到的情况一样，引发了关于促使神经元进入超同步化（如在IES期间发生的那样）的突触/非突触机制的新问题。我们进一步证明，这种非侵入性多尺度多模态方法适用于研究患者IES的病理生理学。
