Abstracts

Rationale: Previous human studies of adults and children using intracranial electrocorticography (ECoG) recording reported that spindle activity consisting of sigma-range oscillations showing a waxing and waning pattern can be seen in the medial temporal region. It remains uncertain whether such medial temporal spindles represent a physiological activity or an epileptogenic activity triggering epileptic seizures. In the present study, we determined how medial temporal spindles were altered by intravenous administration of an antiepileptic agent, midazolam in children with focal epilepsy. Methods: We studied three children with focal epilepsy, who underwent subdural electrode placement and extraoperative ECoG recording for subsequent resection of the seizure focus; an intravenous bolus of midazolam was given to abort ongoing simple-partial seizures or to provide sedation prior to induction of general anesthesia. ‘Midazolam-induced ECoG frequency alteration’ in sites distant from the seizure focus as well as ‘seizure-related ECoG frequency alteration’ in and around the seizure focus were sequentially animated on their individual three-dimensional MR images. The frequency bands of interest in the present study ranged from 0.5 to 200 Hz. Results: The common ECoG changes induced by midazolam included gradual augmentation of spindle oscillations at 12-16 Hz and beta oscillations at 16-32 Hz in the widespread non-epileptic regions including the medial temporal regions. Significant increase in the amplitudes of wide frequency bands was noted in the seizure focus during the active seizure period. Conclusions: The observation that administration of an antiepileptic agent resulted in augmentation of medial temporal spindles supports the hypothesis that medial temporal spindles may be of physiological rather than epileptogenic nature. (Supported by NIH Grant NS47550 to E. Asano)