Analysis of Epileptic Discharges from Implanted Subdural Electrodes in Patients with Sturge-Weber Syndrome

Objective
Almost two-thirds of patients with Sturge-Weber syndrome (SWS) have epilepsy, and half of them require surgery for it. However, it is well known that scalp electroencephalography (EEG) does not demonstrate unequivocal epileptic discharges in patients with SWS. Therefore, we analyzed interictal and ictal discharges from intracranial subdural EEG recordings in patients treated surgically for SWS to elucidate epileptogenicity in this disorder.
Methods
Five intractable epileptic patients with SWS who were implanted with subdural electrodes for presurgical evaluation were enrolled in this study. We examined the following seizure parameters: seizure onset zone (SOZ), propagation speed of seizure discharges, and seizure duration by visual inspection. Additionally, power spectrogram analysis on some frequency bands at SOZ was performed from 60 s before the visually detected seizure onset using the EEG Complex Demodulation Method (CDM).
Results
We obtained 21 seizures from five patients for evaluation, and all seizures initiated from the cortex under the leptomeningeal angioma. Most of the patients presented with motionless staring and respiratory distress as seizure symptoms. The average seizure propagation speed and duration were 3.1 ± 3.6 cm/min and 19.4 ± 33.6 min, respectively. Significant power spectrogram changes at the SOZ were detected at 10–30 Hz from 15 s before seizure onset, and at 30–80 Hz from 5 s before seizure onset.
Significance
In patients with SWS, seizures initiate from the cortex under the leptomeningeal angioma, and seizure propagation is slow and persists for a longer period. CDM indicated beta to low gamma-ranged seizure discharges starting from shortly before the visually detected seizure onset. Our ECoG findings indicate that ischemia is a principal mechanism underlying ictogenesis and epileptogenesis in SWS.

研究目的：约三分之二的斯特奇-韦伯综合征（Sturge-Weber syndrome, SWS）患者会罹患癫痫，其中半数需通过手术治疗。但学界已知，头皮脑电图（scalp electroencephalography, EEG）无法明确检出SWS患者的癫痫样放电。为此，本研究针对接受手术治疗的SWS癫痫患者，分析其颅内硬膜下脑电图记录中的发作间期与发作期放电，以阐明该疾病的致痫机制。

研究方法：本研究纳入5例因难治性癫痫接受术前评估并植入硬膜下电极的SWS患者。通过人工目视分析，我们提取了以下癫痫发作参数：发作起始区（seizure onset zone, SOZ）、痫样放电传播速度以及发作持续时间。此外，采用脑电图复解调法（EEG Complex Demodulation Method, CDM），对目视检测到发作前60秒内SOZ区域的部分频段进行功率谱分析。

研究结果：本研究从5例患者中获取了21次发作用于分析，所有发作均起始于软脑膜血管瘤（leptomeningeal angioma）下方的皮层。多数患者的发作症状表现为不动性凝视与呼吸窘迫。发作传播的平均速度与持续时间分别为3.1±3.6 cm/min与19.4±33.6 min。在发作前15秒起，SOZ区域的10~30 Hz频段出现显著功率谱变化；发作前5秒起，30~80 Hz频段亦出现显著功率谱改变。

研究意义：SWS患者的癫痫发作均起源于软脑膜血管瘤下方的皮层，且发作传播速度缓慢、持续时间较长。复解调法检测显示，β到低γ频段的痫样放电在目视检测到发作前不久即已出现。本研究的脑皮层电图（electrocorticography, ECoG）结果表明，缺血是SWS患者发作发生与致痫的核心机制。