Outcomes of stereoelectroencephalography exploration at an epilepsy surgery center

Abstract

Objectives: Epilepsy surgery is offered in resistant focal epilepsy. Non-invasive investigations like scalp video EEG monitoring (SVEM) help delineate epileptogenic zone. Complex cases may require intracranial video EEG monitoring (IVEM). Stereoelectroencephalography (SEEG)-based intracerebral electrode implantationhas better spatial resolution, lower morbidity, better tolerance, and superiority in sampling deep structures. Our objectives were to assess IVEM using SEEG with regard to reasoning behind implantation, course, surgical interventions, and outcomes. Materials and methods: Seventy-two admissions for SEEG from January 2014 toDecember 2018 were included in the study. Demographic and clinical data were retrospectively collected. Results:The cohort comprised of 69 adults of which 34 (47%) had lesional MRI.Reasons for SEEG considering all cases included non-localizing ictal onset (76%), ictal-interictal discordance (21%), discordant semiology (17%), proximity to eloquent cortex (33%), nuclear imaging discordance (34%), and discordance with neuropsychology (19%). Among lesional cases, additional reasons included SVEM discordance (68%) and dual or multiple pathology (47%).Forty-eight patients (67%) were offered resective surgery, and 41 underwent it.Twenty-three (56%) had at least one year post-surgical follow-up of which 14 (61%) had Engels class I outcome. Of the remaining 23 who were continued on medical management, 4 (17%) became seizure-free and 12 (51%) had reduction in seizure frequency.Conclusion: SEEG monitoring is an important and safe tool for presurgical evaluation with good surgical and non-surgical outcomes. Whether seizure freedom following non-surgical management could be related to SEEG implantation, medication change, or natural course needs to be determined. K E Y W O R D Sdrug-resistant focal epilepsy, epilepsy surgery, outcomes, stereoelectroencephalography | CON CLUS IONSSEEG is a relatively safe procedure with minimal morbidity and mortality. Surgical outcomes are comparable to previous studies.Hemorrhagic complications are the most common with relatively low morbidity. Those continued on medical management after SEEG implantation do not have a dismal prognosis with a small proportion achieving seizure freedom and majority achieving seizure reduction suggesting that SEEG implantation itself may have some therapeutic effect disrupting epileptic networks. Further controlled studies need to be done to prove this.

Lack of spontaneous typical seizures during intracranial monitoring with stereo‐electroencephalography

“…This improvement has been associated with the “implantation effect” or “insertional effect,” terms used to describe a transient and rare phenomenon of seizure improvement following intracranial electroencephalography 9–11 . This effect has been reported by others, even resulting in seizure freedom for prolonged periods of time 12–16 . A transient period of electro‐corticographical post‐implantation changes recorded through responsive neurostimulation (RNS) devices has been reported as well 17 .…”

“…[9][10][11] This effect has been reported by others, even resulting in seizure freedom for prolonged periods of time. [12][13][14][15][16] A transient period of electro-corticographical post-implantation changes recorded through responsive neurostimulation (RNS) devices has been reported as well. 17 These alterations could be explained in local neuroinflammatory changes that may alter epileptogenic networks as some experimental models have suggested.…”

Candidate Selection for Implantation: Noninvasive Predictors of Seizure Onset Zone Focality and Surgical Outcome in People with Drug-Resistant Epilepsy Evaluated by Intracranial Video-EEG Monitoring—A Retrospective Cohort Study

“…In our study, only 7 of 58 patients with a nonfocal SOZ were ruled out for surgery. In contrast, other studies with a lower percentage of patients who had undergone surgery could achieve a higher Engel class I outcome ratio, probably due to stricter candidate selection criteria for surgery [16]. The high proportion of bilateral SEEG and the high number of electrodes in some patients (more than 15 electrodes in 5 cases) may also suggest that preimplantation hypotheses were not strong enough for these cases [8,29].…”

“…They require highly trained professionals specialised in epilepsy such as neurosurgeons, neurologists, nurses, or EEG technicians, which are usually only available in a limited number of epilepsy centres in each country [8]. Furthermore, not all patients who undergo IVEM will ultimately benefit from it [14][15][16]. Different factors may influence the outcome; these include IVEM candidate selection, implantation strategy, subsequent interpretation of the IVEM recordings, and the adequacy of the surgical procedure [17].…”

“…Different factors may influence the outcome; these include IVEM candidate selection, implantation strategy, subsequent interpretation of the IVEM recordings, and the adequacy of the surgical procedure [17]. For example, in some cases, surgery is not recommended due to a nonfocal SOZ or, conversely, patients are operated on, but seizure control does not improve significantly [14,16].…”