Tailor-Made Surgery Based on Functional Networks for Intractable Epilepsy

Abstract

Normal and pathological networks related to seizure propagation have got attention to elucide complex seizure semiology and contribute to diagnosis and surgical monitoring in epilepsy treatment. Since focal and generalized epileptogenic syndromes abnormalities might involve multiple foci and large-scale networks, we applied electrophysiolpgy (cortco-cortico evoked potential; CCEP), and tractography to make detailed diagnosis for complex syndrome. All 14 epilepsy patients with no or little abnormality on images investigations underwent subdural grid implantation for epilepsy diagnosis. To perform quick network analysis, we recorded and analyzed high gamma activity (HGA) of epileptogenic activity and CCEPs to identify pathological activity distribution and network connectivity. [Results] Pathological CCEPs showed two negative deflections consisting of early (>40 ms) and late (>150 ms) components in electrically stable circumstance at bed side and early CCEPs appeared in 57% of the patients. On the basis of the CCEP findings, tractography detected anatomical connections. Early components of pathological CCEPs diminished after complete disconnection of tractoography-based fibers between the foci in seven of eight cases. One case with residual pathological CCEPs showed poorer outcome. Thirteen (92.8%) patients with or without CCEPs who underwent network surgery had favorable prognosis except for a case with wide traumatic epilepsy. Intraoperative CCEP measurements and HGA mapping enabled visualization of pathological networks and clinical impotence as a biomarker to improve functional prognosis. HGA/CCEP recording should shed light on pathological and complex propagation for epilepsy surgery.

Canonical Response Parameterization: Quantifying the structure of responses to single-pulse intracranial electrical brain stimulation

“…Single-pulse electrical stimulation of the white and gray matter has been used for intraoperative connectivity mapping during surgery for tumor and epileptic focus resection [54, 55]. The utility of these diagnostics is still being explored [56], and CRP could help to simplify and standardize the interpretation of the CCEPs (the shape of which, as shown here, will vary dramatically), helping to identify the optimal approach for assistance during resection.…”

Intraoperative Brain Mapping by Cortico-Cortical Evoked Potential

“…Because of the marked practicality and feasibility, CCEP monitoring is now also used in intraoperative settings to probe and monitor functional brain networks, such as those involved in language and motor functions (Kikuchi et al, 2012 ; Saito et al, 2014 ; Yamao et al, 2014 , 2017b ; Enatsu et al, 2016 ; Tamura et al, 2016 ; Ookawa et al, 2017 ; Kanno et al, 2018 ; Suzuki et al, 2019 ; Yoshimoto et al, 2019 ; Nakae et al, 2020 ; Shibata et al, 2020 ; Vincent et al, 2020 ). CCEP monitoring is also able to detect connection or disconnection of an epileptogenic network during epilepsy surgery (Inoue et al, 2018 ; Kamada et al, 2018 , 2020 ) ( Table 1 ).…”

Network dysfunction in pre and postsurgical epilepsy: connectomics as a tool and not a destination

“…Using intraoperative electrophysiology, Mariani et al and Kamada et al both investigated the applicability of using neurostimulation to guide resection and improve cognitive outcomes [19,20]. Both groups found preliminary evidence to suggest that intraoperative monitoring of evoked potentials to evaluate the integrity of language circuits could improve cognitive outcomes.…”