The epileptogenic high frequency oscillations skipping the motor area in children with multilobar drug-resistant epilepsy

Publication date: Available online 24 March 2017
Source:Clinical Neurophysiology
Author(s): Yasushi Iimura, Kevin Jones, Kyoko Hattori, Yushi Okazawa, Atsuko Noda, Kana Hoashi, Yutaka Nonoda, Eishi Asano, Tomoyuki Akiyama, Cristina Go, Ayako Ochi, O. Carter Snead, Elizabeth J. Donner, James T. Rutka, James M. Drake, Hiroshi Otsubo
ObjectiveSubtotal hemispherectomy is characterized by resection of multiple-lobes in children with drug-resistant epilepsy, skipping the motor area (MA). We determined the epileptogenicity using occurrence rate (OR) of high frequency oscillations(HFO) and modulation index(MI) demonstrating strength of coupling between HFO and slow wave. We hypothesized that epileptogenicity increased over the multiple-lobes, but skipping MA.MethodsWe analyzed 23 children(14 subtotal hemispherectomy; 9 multilobar resections). Scalp video-EEG and magnetoencephalography were performed before surgery. We analyzed OR(HFO) and MI(5 phases=0.5-8 Hz) on electrodes of total, resection areas, and MA. We compared the data between good (ILAE class I-II) vs. poor (III-VI) seizure outcome groups.ResultsILAE Class Ia outcome was achieved in 18 children. Among MI(5 phases) in the resection areas, MI(3-4Hz) was the highest. OR(HFO) and MI(3-4Hz) in both total area and resection areas were significantly higher in the good seizure outcome group than those of poor group. OR(HFO) and MI(3-4Hz) in resection areas were significantly higher than those of MA.ConclusionsOur patients with multilobar drug-resistant epilepsy showed evidence of multifocal epileptogenicity that specifically skipped the MA.SignificanceThis is the first study demonstrating that the electrophysiological phenotype of multifocal epilepsy specifically skips the MA, using OR(HFO) and MI(3-4Hz).



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