Neurophysiology of Epilepsy Unit, NINDS, National Institutes of Health, Bethesda, MD 20892, USA.
Surgical Neurology Branch, NINDS, National Institutes of Health, Bethesda, MD 20892, USA.
Brain. 2023 Dec 1;146(12):5168-5181. doi: 10.1093/brain/awad259.
Interictal epileptiform discharges have been shown to propagate from focal epileptogenic sources as travelling waves or through more rapid white matter conduction. We hypothesize that both modes of propagation are necessary to explain interictal discharge timing delays. We propose a method that, for the first time, incorporates both propagation modes to identify unique potential sources of interictal activity. We retrospectively analysed 38 focal epilepsy patients who underwent intracranial EEG recordings and diffusion-weighted imaging for epilepsy surgery evaluation. Interictal discharges were detected and localized to the most likely source based on relative delays in time of arrival across electrodes, incorporating travelling waves and white matter propagation. We assessed the influence of white matter propagation on distance of spread, timing and clinical interpretation of interictal activity. To evaluate accuracy, we compared our source localization results to earliest spiking regions to predict seizure outcomes. White matter propagation helps to explain the timing delays observed in interictal discharge sequences, underlying rapid and distant propagation. Sources identified based on differences in time of receipt of interictal discharges are often distinct from the leading electrode location. Receipt of activity propagating rapidly via white matter can occur earlier than more local activity propagating via slower cortical travelling waves. In our cohort, our source localization approach was more accurate in predicting seizure outcomes than the leading electrode location. Inclusion of white matter in addition to travelling wave propagation in our model of discharge spread did not improve overall accuracy but allowed for identification of unique and at times distant potential sources of activity, particularly in patients with persistent postoperative seizures. Since distant white matter propagation can occur more rapidly than local travelling wave propagation, combined modes of propagation within an interictal discharge sequence can decouple the commonly assumed relationship between spike timing and distance from the source. Our findings thus highlight the clinical importance of recognizing the presence of dual modes of propagation during interictal discharges, as this may be a cause of clinical mislocalization.
发作间期癫痫样放电已被证明可以从局灶性致痫源以游走波的形式传播，或者通过更快的白质传导传播。我们假设这两种传播模式都是解释发作间期放电时程延迟所必需的。我们提出了一种方法，首次将这两种传播模式结合起来，以确定发作间期活动的独特潜在源。我们回顾性分析了 38 例接受颅内脑电图记录和弥散加权成像评估癫痫手术的局灶性癫痫患者。根据电极间到达时间的相对延迟，检测到发作间期放电并将其定位到最可能的源，包括游走波和白质传播。我们评估了白质传播对传播距离、发作间期活动的时间和临床解释的影响。为了评估准确性，我们将源定位结果与最早的放电区域进行比较，以预测癫痫发作的结果。白质传播有助于解释发作间期放电序列中观察到的时程延迟，这是快速和远距离传播的基础。根据发作间期放电接收时间的差异确定的源通常与主导电极的位置不同。通过白质快速传播的活动接收可以早于通过较慢的皮质游走波传播的更局部活动。在我们的队列中，我们的源定位方法在预测癫痫发作结果方面比主导电极位置更准确。在我们的放电传播模型中，除了游走波传播外，还包括白质传播，这并没有提高整体准确性，但允许识别独特的和有时是遥远的潜在活动源，特别是在术后持续癫痫发作的患者中。由于远距离白质传播可以比局部游走波传播更快，因此发作间期放电序列中联合传播模式可以解耦通常假定的尖峰时间和距源距离之间的关系。因此，我们的研究结果强调了在发作间期放电期间识别存在两种传播模式的临床重要性，因为这可能是导致临床定位错误的原因。
