脑电图动态非线性分析对癫痫发作预报的评估意义

目的:从非线性动力学角度探索在癫痫发作间期、发作期及发作前期脑电图活动的动态非线性变化特征,以期为癫痫发作的短期预报提供临床实验依据。方法:于2004-10选取天津医科大学总医院癫痫专科门诊男性癫痫患者1例,连续记录其在发作前、发作中及发作后的脑电图,选择其中异常度较高,伪差较少的导联(前额FP2导联)的脑电图进行2048点的相关维数计算(窗口移动2s/次,窗口长度8s),相关维数嵌入维为12,采用时间延迟重构相空间技术,延迟时间τ选用自相关函数第1个过零点时的时移量。对其癫痫发作间期、发作前期、发作期及发作后期脑电图进行连续动态非线性分析。结果:从发作间期至发作前期、发作期相关维数依次显著下降,与发作间期比较,发作前期与发作期的平均相关维数明显降低[(5.501±0.602),(4.602±0.517),(3.640±0.345),P<0.01]。至发作后期(5.229±0.364)又升高至接近发作间期水平,即癫痫发作时脑电图相关维数最低,且发作前约120s处,脑电图相关维数已开始呈波动性下降。至发作开始,下降更为迅速,相关维数最低处仅为2.52,低于发作间期的平均值5.501。此后在脑电波幅下降至间期二分之一前约60～70s,相关维数再次上升至接近发作间期水平,并保持相对稳定。结论:癫痫发作的不同时期其脑电图的相关维数不同,以发作期最低。并且在临床尚无发作表现时脑电图的相关维数已呈波动性下降,即采用脑电图动态非线性分析可能在癫痫发作前至少120s进行预报。

Changes of serum adrenocorticotropic hormone and cortisol levels during sleep seizures

Objective Measuring the serum concentrations of adrenocorticotropic hormone （ACTH） and cortisol in epileptic seizures during sleep to investigate their link to the EEG changes. Methods Pre-surgical evaluation was performed by videoEEG monitoring using 24 channel recording. Thirty six epilepsy patients could be attributed to two groups： 28 patients had spontaneous seizures, and the other 8 patients whose seizures were induced by bemegride. Another 11 persons with confirmed psychogenic non-epileptic seizures （PNES） served as control group. Blood samples were obtained at five points： wake （08：00 a.m.）, sleep （00：00 a.m.）, and shortly before, during and after an epileptic seizure. The serum ACTH and cortisol were measured and analyzed by chemiluminescent immunoassay. Results The levels of ACTH and cortisol in serum underwent significant changes： declining below the average sleep-level shortly before seizures, increasing during seizures, and far above the average wake-level after seizures （P 〈 0.001）. Such changes did not occur in the control group （P 〉 0.05）. The ACTH and cortisol levels had no significant difference between spontaneous group and bemegride-induced group （P 〉 0.05）. Conclusion The serum concentrations of ACTH and cortisol during sleep seizures are linked with pre-ictal and ictal EEG changes in epilepsy patients.

Physical activity in sudden unexpected death in epilepsy: much more than a simple sport

Sudden unexpected death in epilepsy （SUDEP） is the most important direct epilepsy-related cause of death. Additionally, potential pathomechanisms for SUDEP is unknown, but it is very probable that cardiac arrhythmia during and between seizures, electrolyte disturbances, arrhythmogenic drugs or transmission of epileptic activity via the autonomic nervous system to the heart may play a potential role. Quite interestingly, clinical and experimental data have shown that physical activity can decrease seizure frequency, as well as lead to improved cardiovascular health in patients with epilepsy. Based on these facts, the purpose of this article is to review the body of literature of the possible contribution of physical exercise to the SUDEP prevention in a comprehensive manner.

Localizing epileptic focus and assessing electrical stimulus effects on epilepsy in rats using stretchable micro electrocorticogram electrodes

Epilepsy is a chronic nervous disease with increasing incidence worldwide,while the accurate localization of epileptic focus and the corresponding treatment are still challenging due to the lack of effective tools to monitor and modulate the related brain neurological activities.In this work,stretchable micro electrocorticogram(mECoG)electrodes are developed and used to investigate penicillininduced epilepsy in rats.The electrodes possess excellent stretchability,conformality,anti-interference ability and sufficient resolution to successfully monitor electroencephalogram(EEG)signals,which is superior to traditional rigid polyimide-based electrodes.Characteristic epileptic spike waves are detected and analyzed to study the epileptic focus and electrical stimulus effects during epileptic seizures.It is found that the spike waves occur first in the visual cortex which is likely to be the epileptic focus.Epileptic spike wave frequency quickly increases to 1.07 Hz where it reaches a plateau and remains stable.There is no dominant brain hemisphere that would show early warning of epileptic seizures.Electrical stimuli for various times are applied after administering penicillin.It is found that 15 min of electrical stimulus has the best restraining effect on epileptic seizures.The mECoG electrodes developed in this study show potentials for applications in stretchable biomedical devices.

Stochastic fluctuations of permittivity coupling regulate seizure dynamics in partial epilepsy

Partial epilepsy is characterized by recurrent seizures that arise from a localized pathological brain region. During the onset of partial epilepsy, the seizure evolution commonly exhibits typical timescale separation phenomenon. This timescale separation behavior can be mimicked by a paradigmatic model termed as Epileptor, which consists of coupled fast-slow neural populations via a permittivity variable. By incorporating permittivity noise into the Epileptor model, we show here that stochastic fluctuations of permittivity coupling participate in the modulation of seizure dynamics in partial epilepsy. In particular, introducing a certain level of permittivity noise can make the model produce more comparable seizure-like events that capture the temporal variability in realistic partial seizures. Furthermore, we observe that with the help of permittivity noise our stochastic Epileptor model can trigger the seizure dynamics even when it operates in the theoretical nonepileptogenic regime. These findings establish a deep mechanistic understanding on how stochastic fluctuations of permittivity coupling shape the seizure dynamics in partial epilepsy,and provide insightful biological implications.