Abstracts

Rationale: Recent neuroimaging studies suggest that intractable epilepsy involves pathological functional networks as well as strong epileptogenic foci. Combined cortico-cortical evoked potential (CCEP) recording and tractography is a useful strategy for mapping functional connectivity in normal and pathological networks. In this report, we demonstrate the efficacy of preoperative combined CCEP, high gamma activity (HGA) mapping, and tractography for surgical planning and of intraoperative CCEP measures for confirmation of selective pathological network disconnection.  Methods: We treated four intractable epilepsy cases, all with subdural grid implantation, using presurgical CCEP, HGA, and diffusion tensor imaging (DTI)-based tractography analysis as well as continuous CCEP monitoring during resection surgery.  Results: All four patients in this report had measurable pathological CCEPs. The mean N1 latency of normal CCEPs related to language functions was 22.2 ± 3.5(mean ± SD) ms, whereas pathological CCEP latencies varied between 18.1 and 22.4 ms. Pathological CCEPs diminished after complete disconnection in all cases. All of them were in long-term postoperative seizure-free status, although one has still suffered from visual aura every other month.  Conclusions: Combined CCEP measurement, HGA mapping, and tractography greatly facilitated targeted disconnection of pathological networks. Although CCEP recording requires technical expertise, it allows for assessment of pathological network involvement in intractable epilepsy and may improve seizure outcome.  Funding: N/A