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Abstract Details

A simultaneous intracranial EEG- surface EMG analysis of generalized tonic-clonic seizures
Epilepsy/Clinical Neurophysiology (EEG)
P10 - Poster Session 10 (8:00 AM-9:00 AM)
9-004
The precise mechanism of a GTC seizure is not well understood. A polygraphic analysis with intracranial-EEG (iEEG) and surface-EMG (sEMG) offers a unique opportunity to study this mechanism from a neurophysiological standpoint.
To analyze the neurophysiology of generalized tonic-clonic (GTC) seizures using intracranial-EEG and surface-EMG data.
We studied two patients with refractory focal epilepsy, admitted to the epilepsy-monitoring unit with iEEG and sEMG. Both patients underwent direct electrical cortical stimulation for cortical mapping. iEEG and EMG signals were recorded using Nihon-Kohden’s JE-120 256-channel amplifier with a sampling rate of 2000Hz. A GTC seizure was provoked in both patients during their respective stimulation sessions.

The tonic phase demonstrated continuous spike activity in iEEG with highest power in 50-100Hz range. The sEMG activity demonstrated an interference pattern in both agonists and antagonists, consistent with a tetanic contraction with a very similar power spectrum as the iEEG.

The clonic phase was characterized by polyspike and slow-wave pattern. The polyspikes and slow-waves were time-locked with synchronized tetanic sEMG bursts and silent-periods in agonists and antagonists, respectively. The polyspikes were superimposed with ~400-600Hz high-frequency oscillations (HFOs). The frequency of the serrations of the motor unit potentials in the sEMG bursts was a subharmonic of the HFOs. The iEEG-sEMG latency was ~17-21ms, consistent with corticospinal conduction. There was a progressive increase of the sEMG burst and silent-period duration during the clonic phase, associated with corresponding increases in the polyspike and slow-wave durations.

This study shows a very close relationship between iEEG and sEMG activity in a GTC seizure. The very similar power spectra of the iEEG and sEMG activities indicate that a GTC seizure is a direct result of cortical electrical activity varying in a crescendo-decrescendo manner. The transition from tonic to clonic phase is due to the “weakening” of the seizure discharge intensity.  
Authors/Disclosures
Aybuke Acar, MD (University Hospitals Cleveland Medical Center)
PRESENTER
Dr. Acar has nothing to disclose.
Hemani Ticku, MD Dr. Ticku has nothing to disclose.
Neel Fotedar, MD (University Hospitals Cleveland Medical Center) Dr. Fotedar has nothing to disclose.