Simultaneous scalp EEG/functional MRI measures non-invasively haemodynamic responses to interictal epileptic discharges, which are related to the epileptogenic zone. High frequency oscillations are also an excellent indicator of this zone, but are primarily recorded from intracerebral EEG. We studied the spatial overlap of these two important markers in patients with drug-resistant epilepsy to assess if their combination could help better define the extent of the epileptogenic zone. We included patients who underwent EEG-functional MRI and later intracerebral EEG. Based on intracerebral EEG findings, we separated patients with unifocal seizures from patients with multifocal or unknown onset seizures. Haemodynamic t-maps were coregistered with the intracerebral electrode positions. Each EEG channel was classified as pertaining to one of the following categories: primary haemodynamic cluster (maximum t-value), secondary cluster (t-value > 90% of the primary cluster) or outside the primary and secondary clusters. We marked high frequency oscillations (ripples: 80–250 Hz; fast ripples: 250–500 Hz) during 1 h of slow wave sleep, and compared their rates in each haemodynamic category. After classifying channels as high- or low-rate, the proportion of high-rate channels within the primary or primary plus secondary clusters was compared to the proportion expected by chance. Twenty-five patients, 11 with unifocal and 14 with multifocal/unknown seizure onsets, were studied. We found a significantly higher median high frequency oscillation rate in the primary cluster compared to secondary cluster and outside these two clusters for the unifocal group (P < 0.0001), but not for the multifocal/unknown group. For the unifocal group, the number of high-rate channels within the primary or primary plus secondary clusters was significantly higher than expected by chance. This held only for the high-ripple-rate channels in the multifocal/unknown group. At the patient level, most patients (18/25, or 72%) had at least one high-rate channel within a primary cluster. In patients with unifocal epilepsy, the maximum haemodynamic response (primary cluster) related to scalp interictal discharges overlaps with the tissue generating high frequency oscillations at high rates. If intracranial EEG is warranted, this response should be explored. As a tentative clinical use of the combination of these techniques we propose that higher high frequency oscillation rates inside than outside the maximum response indicates that the patient has indeed a focal epileptogenic zone demarcated by this response, whereas similar rates inside and outside may indicate a widespread epileptogenic zone or an epileptogenic zone not covered by the implantation.

中文翻译：

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病灶性癫痫患者中与峰值相关的血液动力学反应与高频振荡重叠

同时头皮脑电图/功能磁共振成像测量非侵入性血液动力学对发作间期癫痫放电的反应，与癫痫发作区有关。高频振荡也是该区域的绝佳指标，但主要是从脑内脑电图记录的。我们研究了耐药性癫痫患者这两个重要标志物的空间重叠，以评估它们的组合是否可以帮助更好地定义癫痫发生区的范围。我们纳入了接受脑电图功能MRI和脑后脑电图检查的患者。基于脑电图的发现，我们将单灶性癫痫患者与多灶性或未知发作性癫痫患者分开。血流动力学t-图与脑内电极位置共配准。每个EEG通道被归类为以下类别之一：主要血流动力学群集（最大t值），次要群集（t值>占主要群集的90％）或在主要和次要群集之外。我们标记了慢波睡眠1 h期间的高频振荡（波纹：80–250 Hz；快速波动：250–500 Hz），并比较了每种血流动力学类别的频率。在将频道分为高速率或低速率分类之后，将主要或初级和次级集群中高速率通道的比例与偶然预期的比例进行了比较。研究对象为25例患者，其中11例为单灶性发作，14例为多灶性/未知癫痫发作。P <0.0001），但不适用于多焦点/未知组。对于单焦点组，主要群集或主要群集和次要群集中的高速率通道数量显着高于偶然的预期。这仅适用于多焦点/未知组中的高波动率通道。在患者水平上，大多数患者（18/25或72％）在一个主要簇中具有至少一个高速率通道。在患有单灶性癫痫的患者中，与头皮间质放电相关的最大血流动力学反应（主要簇）与组织重叠，并以高频率产生高频振荡。如果有必要进行颅内脑电图检查，则应探讨这种反应。