Bénar Christian G, Gross Donald W, Wang Yunhua, Petre Valentina, Pike Bruce, Dubeau François, Gotman Jean
Montreal Neurological Institute, McGill University, Montréal, Québec, H3A 2B4, Canada.
Neuroimage. 2002 Nov;17(3):1182-92. doi: 10.1006/nimg.2002.1164.
We studied single-event and average BOLD responses to EEG interictal epileptic discharges (IEDs) in four patients with focal epilepsy, using continuous EEG-fMRI during 80-min sessions. The detection of activated areas was performed by comparing the BOLD signal at each voxel to a model of the expected signal. Since little is known about the BOLD response to IEDs, we modeled it with the response to brief auditory events (G. H., NeuroImage 9, 416-429). For each activated area, we then obtained the time course of the BOLD signal for the complete session and computed the actual average hemodynamic response function (HRF) to IEDs. In two of four patients, we observed clear BOLD responses to single IEDs. The average response was composed of a positive lobe peaking between 6 and 7 s in all patients and a negative undershoot in three patients. There were important variations in amplitude and shape between average HRFs across patients. The average HRF presented a wider positive lobe than the Glover model in three patients and a longer undershoot in two. There was a remarkable similarity in the shape of the HRF across areas for patients presenting multiple activation sites. There was no clear correlation between the amplitude of individual BOLD responses and the amplitude of the corresponding EEG spike. The possibility of a longer HRF could be used to improve statistical detection of activation in simultaneous EEG-fMRI. The variability in average HRFs across patients could reflect in part different pathophysiological mechanisms.
我们对4例局灶性癫痫患者进行了研究，在80分钟的监测过程中采用连续脑电图-功能磁共振成像（EEG-fMRI）技术，观察单次事件及平均血氧水平依赖（BOLD）反应对脑电图发作间期癫痫样放电（IEDs）的情况。通过将每个体素处的BOLD信号与预期信号模型进行比较来检测激活区域。由于对IEDs的BOLD反应了解甚少，我们用对短暂听觉事件的反应来对其进行建模（G. H.，《神经影像学》9，416 - 429）。对于每个激活区域，我们随后获取了整个监测过程中BOLD信号的时间进程，并计算了对IEDs的实际平均血液动力学反应函数（HRF）。在4例患者中的2例，我们观察到了对单个IEDs的明显BOLD反应。所有患者的平均反应均由一个在6至7秒达到峰值的正波峰以及3例患者出现的负向波谷组成。不同患者的平均HRF在幅度和形状上存在重要差异。3例患者的平均HRF呈现出比Glover模型更宽的正波峰，2例患者的负向波谷更长。对于存在多个激活位点的患者，不同区域的HRF形状具有显著相似性。单个BOLD反应的幅度与相应脑电图棘波的幅度之间没有明显的相关性。较长的HRF有可能用于改善同步EEG-fMRI中激活的统计检测。不同患者平均HRF的变异性可能部分反映了不同的病理生理机制。
