Patterns of muscle activation during generalized tonic and tonic-clonic epileptic seizures

Abstract

Summary Purpose: 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. Methods: 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. Key Findings: 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. Significance: 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.

Automated seizure detection systems and their effectiveness for each type of seizure

“…sEMG helps differentiate epileptic seizures from non-epileptic seizures: epileptic seizures have a large proportion of EMG activity in the frequency band above 100-150 Hz [55,56]. sEMG detects muscle activity with as few as one channel; deltoid and anterior tibialis muscles are the preferred placement sites [55][56][57].…”

Detection of tonic epileptic seizures based on surface electromyography

“…The difference between the false alarm and the seizure shown in Fig. 3 is, however, very small, unlike the example with a tonic seizure and a simulated seizure in [8]. An explanation could be that the simulated seizures consist of maximal voluntary contractions (MVC).…”

“…They were chosen as it was observed in a study by Conradsen et. al [8] that tonic seizures contained relatively more power in the higher frequencies compared to simulated seizures. 1 20th Daubechies as mother wavelet…”

Concussive convulsions: A YouTube video analysis

“…Although the hypothesis about CC being a “benign” symptomatic epileptic seizure has already been raised, our data do not confirm this. Evolution of seizure semiology during CCs either was not present or was strongly atypical to grand mal: (1) separate tonic phase could be observed neither in bilateral nor in focally evolving bilateral CCs; (2) in some cases tonic posturing occurred after and superimposed the clonic movement; and (3) Jacksonian march (or other focal seizure evolution) could not be detected. The big variability of clonus duration in CCs also goes against the theory of grand mal similarity (Fig.…”