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 11 seizures, IVEEG showed low-amplitude fast waves (∼60 Hz) starting at the left mesial-temporal electrodes. Ictal facial grimacing projected low-amplitude (∼20 μV) fast waves (∼160 Hz) on inferior lateral-temporal electrodes. Interictal chewing projected medium-amplitude (∼100 μV) fast waves (∼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.