Vlachos Ioannis, Krishnan Balu, Treiman David M, Tsakalis Konstantinos, Kugiumtzis Dimitris, Iasemidis Leon D
IEEE Trans Biomed Eng. 2017 Sep;64(9):2241-2252. doi: 10.1109/TBME.2016.2633200. Epub 2016 Nov 29.
Accurate determination of the epileptogenic focus is of paramount diagnostic and therapeutic importance in epilepsy. The current gold standard for focus localization is from ictal (seizure) onset and thus requires the occurrence and recording of multiple typical seizures of a patient. Localization of the focus from seizure-free (interictal) periods remains a challenging problem, especially in the absence of interictal epileptiform activity.
By exploring the concept of effective inflow, we developed a focus localization algorithm (FLA) based on directed connectivity between brain sites. Subsequently, using the measure of generalized partial directed coherence over a broad frequency band in FLA for the analysis of interictal periods from long-term (days) intracranial electroencephalographic signals, we identified the brain region that is the most frequent receiver of maximal effective inflow from other brain regions.
In six out of nine patients with temporal lobe epilepsy, the thus identified brain region was a statistically significant outlier (p < 0.01) and coincided with the clinically assessed epileptogenic focus. In the remaining three patients, the clinically assessed focus still exhibited the highest inflow, but it was not deemed an outlier (p > 0.01).
These findings suggest that the epileptogenic focus is a region of intense influence from other regions interictally, possibly as a mechanism to keep it under control in seizure-free periods.
The developed framework is expected to assist with the accurate epileptogenic focus localization, reduce hospital stay and healthcare cost, and provide guidance to treatment of epilepsy via resective surgery or neuromodulation.
准确确定癫痫病灶在癫痫的诊断和治疗中具有至关重要的意义。目前确定病灶位置的金标准是基于发作期（癫痫发作时）的起始点，因此需要患者出现并记录多次典型发作。从发作间期（无发作期）确定病灶位置仍然是一个具有挑战性的问题，尤其是在没有发作间期癫痫样活动的情况下。
通过探索有效流入的概念，我们开发了一种基于脑区之间定向连接性的病灶定位算法（FLA）。随后，在FLA中使用广义偏相干测量法，对来自长期（数天）颅内脑电图信号的发作间期进行宽频带分析，我们确定了从其他脑区接收最大有效流入的频率最高的脑区。
在9例颞叶癫痫患者中，有6例通过这种方法确定的脑区在统计学上是显著的异常值（p < 0.01），并且与临床评估的癫痫病灶一致。在其余3例患者中，临床评估的病灶仍然表现出最高的流入，但未被视为异常值（p > 0.01）。
这些发现表明，癫痫病灶在发作间期是受其他区域强烈影响的区域，这可能是在无发作期对其进行控制的一种机制。
所开发的框架有望有助于准确进行癫痫病灶定位，减少住院时间和医疗成本，并为通过切除手术或神经调节治疗癫痫提供指导。
