Can intraoperative HFO under Sevoflurane anesthesia identify the epileptic focus?

• Project/Area Number: 16K10797
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Neurosurgery
• Research Institution: Nara Medical University
• Principal Investigator: TAMURA KENTARO 奈良県立医科大学, 医学部, 学内講師 (00423913)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Project Status: Completed (Fiscal Year 2018)
• Budget Amount: ¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000); Fiscal Year 2018: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2017: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2016: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
• Keywords: HFO / 術中脳波 / セボフルラン / 高周波振動 / 術中皮質脳波記録 / 脳神経疾患 / てんかん / てんかん外科 / 頭蓋内脳波

Outline of Final Research Achievements

We identified the epileptic focus by using chronic intracranial electrocorticography(ECoG). Before craniotomy, we recorded intraoperative ECoG under Sevoflurane anesthesia with the same electrodes as the ones for chronic intracranial ECoG. The group in which the hippocampus was included in seizure onset zone, high frequency oscillations are more frequent on the hippocampus under lower concentration of Sevoflurane than the group in which the hippocampus was not included in seizure onset zone.　From these findings, we could identify the epileptic focus only with intraoperative ECoG under Sevoflurane anesthesia. But we should consider that the concentration of Sevoflurane could influence the effects of provocation of high frequency oscillations.

Academic Significance and Societal Importance of the Research Achievements

難治てんかんに対するてんかん焦点切除術において，てんかん焦点を同定するためには，頭蓋内脳波記録が必要なことが多いが，侵襲的であることから施行できないことがある．もし切除術中の脳波で焦点が正確に判断できれば，頭蓋内脳波がスキップできる．今回の結果から，手術中のセボフルラン麻酔下の高周波振動測定が，慢性頭蓋内脳波記録の代替となり得ることを示せたが，同時に濃度による影響を十分考慮する必要があることも判明した．この結果を発展させることで，頭蓋内脳波をスキップできる可能性があり，侵襲性が低く，より安全にてんかん外科治療を行うために意義のある成果であったと考える．