Abstracts

Rationale: The purpose of this study was to differentiate ictal muscle contraction high-frequency oscillations (HFOs) from epileptogenic HFOs recorded on intracranial video EEG.Methods: We collected patients with muscle activities recorded on the intracranial electrodes during intracranial video EEG (1000Hz sampling rate). We used multiple band frequency analysis (MBFA) to differentiate the intracranial epileptogenic HFOs from the extracranial nonepileptogenic HFOs of craniofacial muscle activities recorded ictally and interictally by intracranial video EEG.Results: We found two patients with intracranial electrodes recording muscle activities. A 17-year-old boy with a recurrent temporal lobe epilepsy secondary to residual tumor showed both interictal and ictal muscle activities on temporal lobe cortical and depth electrodes. Five year old girl with tuberous sclerosis showed interictal muscle activities on temporal lobe cortical electrodes. Four-year-old boy with left parietal microdysgenesis presented tonic seizures without muscle activities on subdural grid. During 11 seizures in the big adolescent boy (weight, 83.1 kg; height, 175.5 cm), EEG showed low-amplitude fast waves (~60 Hz) starting at the left mesial-temporal electrodes. Ictal facial grimacing projected intermittent low-amplitude (~20 uV) fast waves (~160 Hz). When the patient ate, rhythmic chewing projected medium-amplitude (~100 uV) fast waves (~140 Hz) lasting 400 milliseconds to the inferior lateral-temporal electrodes. MBFA revealed sustained and consistent high-power HFOs at the beginning of seizures in the epileptogenic zone; ictal and interictal extracranial HFOs projected by muscle contractions had nonsustained, randomly scattered, medium-power spectrograms. MBFA showed scattered spectrogram on the only temporal electrodes during interictal chewing periods or during tonic posturing in the other two patients.Conclusions: MBFA differentiated ictal intracranial epileptogenic HFOs in the ictal-onset zone from extracranial nonepileptogenic HFOs caused by muscles responsible for ictal facial grimacing. MBFA provided valuable information about ictal HFOs of intracranial video EEG.