Danish Epilepsy Centre, Department of Neurophysiology, Dianalund, Denmark.
Epilepsia. 2011 Nov;52(11):2125-32. doi: 10.1111/j.1528-1167.2011.03286.x. Epub 2011 Oct 5.
Tonic seizures and the tonic phase of tonic-clonic epileptic seizures are defined as "sustained tonic" muscle contraction lasting a few seconds to minutes. Visual inspection of the surface electromyogram (EMG) during seizures contributed considerably to a better understanding and accurate diagnosis of several seizure types. However, quantitative analysis of the surface EMG during the epileptic seizures has received surprisingly little attention until now. The aim of our study was to elucidate the pathomechanism of the tonic muscle activation during epileptic seizures.
Surface EMG was recorded from the deltoid muscles, on both sides, during 63 seizures from 20 patients with epilepsy (10 with generalized tonic and 10 with tonic-clonic seizures). Twenty age- and gender-matched normal controls simulated 100 generalized tonic seizures. To characterize the signal properties we calculated the root mean square (RMS) of the amplitudes, the median frequency (MF), and the coherence. Based on the spectrograms of both epileptic and simulated seizures, we chose to determine the relative spectral power (RP) in the higher (100-500 Hz) frequency domain.
During the tonic seizures there was a significant shift toward higher frequencies, expressed by an increase in the MF and the RP (100-500 Hz). The amplitude characteristic of the signal (RMS) was significantly higher during the tonic phase of the tonic-clonic seizures as compared to the simulated ones, whereas the RMS of the tonic seizures was significantly lower than the simulated ones. The EMG-EMG coherence was significantly higher during the epileptic seizures (both types) as compared to the simulated ones.
Our results indicate that the mechanism of muscle activation during epileptic seizures is different from the physiologic one. Furthermore the sustained muscle activation during the tonic phase of tonic-clonic seizures is different from that during tonic seizures: The tonic phase of tonic-clonic seizures is characterized by increased amplitude of the signal, whereas tonic seizures are produced by a significant increase in the frequency of the signal.
痉挛性发作和强直-阵挛性癫痫发作的强直期被定义为持续数秒至数分钟的“强直”肌肉收缩。在发作期间对表面肌电图（EMG）进行视觉检查极大地促进了对几种发作类型的更好理解和准确诊断。然而，直到现在，对癫痫发作期间表面 EMG 的定量分析才受到惊人的关注。我们的研究目的是阐明癫痫发作期间肌肉强直激活的病理机制。
从 20 名癫痫患者（10 名全身性强直和 10 名强直-阵挛性发作）的两侧三角肌记录了 63 次发作期间的表面 EMG。20 名年龄和性别匹配的正常对照者模拟了 100 次全身性强直发作。为了描述信号特性，我们计算了幅度的均方根（RMS）、中值频率（MF）和相干性。基于癫痫发作和模拟发作的频谱图，我们选择确定较高（100-500Hz）频率域中的相对光谱功率（RP）。
在强直发作期间，信号的频率显著升高，表现为 MF 和 RP（100-500Hz）增加。与模拟强直发作相比，强直-阵挛性发作的强直期信号特征（RMS）显著升高，而强直发作的 RMS 显著低于模拟强直发作。与模拟强直发作相比，癫痫发作（两种类型）期间的 EMG-EMG 相干性显著升高。
我们的结果表明，癫痫发作期间肌肉激活的机制与生理机制不同。此外，强直-阵挛性发作的强直期与强直发作期间的肌肉持续激活不同：强直-阵挛性发作的强直期以信号幅度增加为特征，而强直发作则以信号频率显著增加为特征。
