High-frequency oscillations of ictal muscle activity and epileptogenic discharges on intracranial EEG in a temporal lobe epilepsy patient

Objective: During seizures, intracranial EEG electrodes can record ictal muscle movements. Our purpose was to differentiate the high-frequency oscillations (HFOs) of extracranial muscle contractions from those of intracranial epileptogenic discharges. Methods: Using intracranial video-EEG (IVEEG), we recorded seizures in a 17-year-old boy with left mesial-temporal lobe epilepsy. We used multiple band frequency analysis (MBFA) to differentiate extracranial HFOs of craniofacial muscle activities from intracranial HFOs recorded ictally and interictally. Results: During I I seizures, IVEEG showed low-amplitude fast waves (similar to 60 Hz) starting at the left mesial-temporal electrodes. Ictal facial grimacing projected low-amplitude (similar to 20 mu V) fast waves (similar to 160 Hz) on inferior lateral-temporal electrodes. Interictal chewing projected medium-amplitude (similar to 100 mu V) fast waves (similar to 140 Hz) correlating to mouth movements. MBFA topographic power spectrograms revealed a sustained, consistent ictal fast-frequency band from electrodes in the seizure-onset zone and randomly scattered HFOs without a specific frequency band from ictal and interictal extracranial muscle contractions. Conclusions: MBFA power spectrograms differentiated randomly scattered muscle HFOs without a specific frequency band at electrodes close to temporal muscles from ictal epileptic HFOs with a sustained, fast-frequency band in the seizure-onset zone. Significance: The pattern and distribution of frequency power spectrograms of extracranial HFOs differ from those of intracranial HFOs. (c) 2008 Published by Elsevier Ireland Ltd. on behalf of International Federation of Clinical Neurophysiology.