Engel Class Research Articles

Insulectomy for Refractory Epilepsy: Case Series and Literature Review

AbstractSurgical resection of the insula (insulectomy) is a procedure used for brain lesions and for refractory epilepsy. It has a difficult surgical access and the need of a wide anatomical knowledge and preoperative planning. There are two types of surgical approaches aiming the exposure of the insular cortex: transsylvian and transcortical. The importance of insulectomies is the efficacy in providing a remarkable decrease in seizures. The objective of the present article is to document the results of a series of 10 patients submitted to insulectomies for refractory epilepsies and compare them with the results of other studies reported in the literature, as well as to describe the main nuances of the surgical approaches and their associated risks. In the new case series, all patients corresponded to preoperative Engel classification IV for; after a mean 2-year follow-up period, they corresponded to Engel classification II. A subtotal resection was performed in six patients, and the remaining four underwent a partial resection, most of them leading to temporary complications. The literature review endorsed the good outcomes of the casuistry. A critical analysis of the presented data reiterates the opinion of several authors that insulectomies are beneficial and safe for the patients. A broad anatomical knowledge of the insular region, preoperative planning (limits of resections), and the use of modern microsurgical techniques must be considered as basic principles by neurosurgeons for the prevention of perioperative morbidities. Insulectomies are safe and effective, although they result in temporary postoperative complications, and provide highly satisfactory results in terms of seizure control.

Predictors of postoperative seizure outcome in supratentorial meningioma.

Meningiomas are the most common primary intracranial tumor. Seizures are common sequelae of meningioma development. Meningioma patients with seizures can be effectively treated with resection, with reports of seizure freedom of 60%-90%. Still, many patients manifest persistent epilepsy. Determining factors associated with worsened seizure outcomes remains critical in improving the quality of life for these patients. The authors sought to identify clinical, radiological, and histological factors associated with worse seizure outcomes in patients with supratentorial meningioma and preoperative seizures. The authors retrospectively reviewed the charts of 384 patients who underwent meningioma resection from 2008 to 2020. The charts of patients with a documented history of preoperative seizures were further reviewed for clinical, radiological, operative, perioperative, histological, and postoperative factors associated with seizures. Engel class at last follow-up was retrospectively assigned by the authors and further grouped into favorable (class I) and worse (class II-IV) outcomes. Factors were subsequently compared by group using comparative statistics. Univariable and multivariable regression models were utilized to identify independent predictors of worse seizure outcome. Fifty-nine patients (15.4%) were found to have preoperative seizures, of whom 57 had sufficient postoperative data to determine Engel class outcome. Forty-two patients (74%) had Engel class I outcomes. The median follow-up was 17 months. Distinct margins on preoperative imaging (p = 0.012), Simpson grade I resection (p = 0.004), postresection ischemia (p = 0.019), WHO grade (p = 0.019), and recurrent disease (p = 0.015) were found to be the strongest predictors of Engel class outcome in univariable logistic regression. MIB-1 index (p = 0.001) and residual volume (p = 0.014) at last follow-up were found to be the strongest predictors of Engel class outcome in univariable generalized linear regression. Postresection ischemia (p = 0.012), WHO grade (p = 0.022), recurrent disease (p = 0.038), and MIB-1 index (p = 0.002) were found to be the strongest independent predictors of Engel class outcomes in multivariable analysis. Postresection ischemia, higher WHO grade, elevated MIB-1 index, and disease recurrence independently predict postresection seizure persistence in patients with supratentorial meningioma. Further understanding of the etiology of these markers may aid in elucidation of this complex disease process and guide management to prevent worse outcomes.

Postsurgical seizure outcome in temporal lobe epilepsy patients with normal or subtle, nonspecific MRI findings.

The authors' objective was to report postsurgical seizure outcome of temporal lobe epilepsy (TLE) patients with normal or subtle, nonspecific MRI findings and to identify prognostic factors related to seizure control after surgery. This was a retrospective study of patients who underwent surgery from 1999 to 2014 at two comprehensive epilepsy centers. Patients with a clear MRI lesion according to team discussion and consensus were excluded. Presurgical information, surgery details, pathological data, and postsurgical outcomes were retrospectively collected from medical charts. Multiple logistic regression analysis was used to assess the effect of clinical, surgical, and neuroimaging factors on the probability of Engel class I (favorable) versus class II-IV (unfavorable) outcome at last follow-up. The authors included 73 patients (59% were female; median age at surgery 35.9 years) who underwent operations after a median duration of epilepsy of 13 years. The median follow-up after surgery was 30.6 months. At latest follow-up, 44% of patients had Engel class I outcome. Favorable prognostic factors were focal nonmotor aware seizures and unilateral or no spikes on interictal scalp EEG. Favorable outcome can be achieved in a good proportion of TLE patients with normal or subtle, nonspecific MRI findings, particularly when presurgical investigation suggests a rather circumscribed generator. Presurgical factors such as the presence of focal nonmotor aware seizures and unilateral or no spikes on interictal EEG may indicate a higher probability of seizure freedom.

Surgical treatment of pediatric intractable frontal lobe epilepsy due to malformation of cortical development

BackgroundMalformation of cortical development (MCD) is a common cause of intractable epilepsy in children. In this study, the effectiveness of frontal lobe epilepsy (FLE) surgery in children with intractable epilepsy due to MCD was assessed and its prognostic factors were studied.MethodsSeventy-six patients with intractable FLE who received epilepsy surgery between January 2016 and March 2018 in Peking University First Hospital were recruited in this study. All the resected brain tissues were demonstrated to be MCD. All patients were followed up for at least 3 years. The clinical data and prognosis were analyzed retrospectively. Univariate and multivariate analyses were performed to investigate the correlations between clinical variables and prognostic outcome (Engel classification).ResultsSixty (78.9%) patients had Engel class I postoperative outcome. The mean age at surgery was 6.00 ± 4.24 years. Sixty-six patients (86.8%) had daily seizures, 40.2% of the patients had epileptic spasm, and 33% of the patients had extensive interictal EEG abnormalities, which, however, could not provide any helpful information for localizing epileptogenic zones. About 29% of the patients had normal MRI findings even by experienced radiologists, and 26% of the patients had epileptogenic lesion involving adjacent lobes. There was a significant correlation between acute postoperative seizure (APOS) and prognosis (P < 0.05): APOS predicted poor prognosis. There was a significant correlation between pathology and prognosis (P < 0.05): FCD IA and FCD IIB were correlated with a good outcome. Both variables with a significance level of P < 0.05 during univariate analysis, including pathology and APOS, were included in multivariate analysis, which were significant independent predictors of prognosis.ConclusionsThe clinical manifestations of pediatric intractable FLE due to MCD are more complicated than those in adults. Multidisplinary presurgical evaluation in pediatric epilepsy is mandatory. The surgical outcome of pediatric FLE due to MCD could reach a seizure-free rate of 78.9% with the follow-up of at least 3 years. The post-operative pathology and APOS may be related to the prognosis of surgery in this group of pediatric patients.

Role of resective surgery in patients older than 60 years with therapy-resistant epilepsy.

Epilepsy surgery for older adults is controversial owing to their longer duration of epilepsy and perceived higher surgical risk. However, because of an aging population and documented benefit of epilepsy surgery, surgery is considered more frequently for these patients. The authors' objective was to analyze the role of resective surgery in patients older than 60 years and to assess outcomes and safety. The authors conducted a retrospective analysis of 595 patients who underwent resective epilepsy surgery at their center from 1999 to 2018. Thirty-one patients aged 60 years or older were identified. Sixty patients younger than 60 years were randomly selected as controls. Population characteristics, results of presurgical evaluations, outcomes, and complications were analyzed. No significant differences were found between the groups in terms of hemisphere dominance, side of surgery, presence of a lesion, and incidence of temporal lobe epilepsy. Epilepsy duration was greater in the older cohort (p = 0.019), and invasive EEG was more commonly employed in younger patients (p = 0.030). The rates of Engel class I outcome at 6 months, 1 year, and 2 years were 89.7%, 96.2%, and 94.7% for the older group and 75% (p = 0.159), 67.3% (p = 0.004), and 75.8% (p = 0.130) for the younger group, respectively. The proportion of seizure-free patients was greatest among those with temporal lobe epilepsy, particularly in the older group. Neurological complication rates did not differ significantly between groups, however medical and other minor complications occurred more frequently in the older group. Patients older than 60 years had equal or better outcomes at 1 year after epilepsy surgery than younger patients. A trend toward a greater proportion of patients with lesional temporal lobe epilepsy was found in the older group. These results suggest that good seizure outcomes can be obtained in older patients despite longer duration of epilepsy.

Surgical treatment of MRI-negative drug resistant epilepsy in children

Objective: analysis of treatment tactics for patients with magnetic-resonance-imaging (MRI) negative epilepsy, characteristics of morphological data and assessment of the treatment results. Material and methods. Within the period of 2013–2021, 31 patients under the age of 18 with drug-resistant nonlesional epilepsy were examined according to the “epilepsy” MRI-protocol. Patient distribution by gender, age, duration of illness, age of onset, number of anticonvulsant protocols, frequency of seizures at the time of initiated treatment, side and lobe of the seizure generation zone was analyzed. The instrumental diagnostic methods were noted in a specially designed study form and reported contribution of relevant result to epileptogenic zone. The distribution of patients according to surgical intervention and histological data was also analyzed. Results. Resection surgery was carried out in 26 (83.9%) patients. Palliative operations were performed in 5 (16.1%) cases with bilateral localization of the epileptic focus: callosotomy (3) and vagal nerve stimulation (2). Twelve months post-therapy outcomes by Engel class I were found in 19 (61.3%) patients, class II – in 6 (19.4%), class III – in 5 (16.1%), and class IV – in 1 (3.2%). Long-term results of surgical treatment were assessed 3 and 5 years later. Conclusion. Surgery of MRI-negative epilepsy can be effective with seizure-free outcome in 61.3% of cases, but requires use of additional diagnostic methods in relation to standard pre-surgery examination to localize epileptogenic zone.

Technical challenges to anterior temporal lobectomy after laser interstitial thermal therapy for mesial temporal lobe epilepsy: technical note.

Mesial temporal sclerosis (MTS) is a frequent cause of medically refractory epilepsy, for which laser interstitial thermal therapy (LITT) is an effective treatment. However, experience with the technical considerations posed by additional surgery after an initial LITT procedure is lacking. The authors present the case of a 12-year-old female with medically refractory temporal lobe epilepsy and left MTS who underwent LITT at a separate institution prior to referral. This patient had no change in early postoperative seizure control (Engel class IVB) and then her seizures worsened despite ongoing medical treatment (Engel class IVC). Post-LITT MRI revealed sparing of the mesial hippocampus head, a poor prognostic factor. The authors describe the technical details illustrated by this case of secondary, stereotactic electroencephalography-guided mesial temporal resection following LITT. The case was managed with anterior temporal lobectomy including the resection of residual hippocampus and amygdala.

De novo epilepsy after microsurgical resection of brain arteriovenous malformations.

Seizures are the second most common presenting symptom of brain arteriovenous malformations (bAVMs) after hemorrhage. Risk factors for preoperative seizures and subsequent seizure control outcomes have been well studied. There is a paucity of literature on postoperative, de novo seizures in initially seizure-naïve patients who undergo resection. Whereas this entity has been documented after craniotomy for a wide variety of neurosurgically treated pathologies including tumors, trauma, and aneurysms, de novo seizures after bAVM resection are poorly studied. Given the debilitating nature of epilepsy, the purpose of this study was to elucidate the incidence and risk factors associated with de novo epilepsy after bAVM resection. A retrospective review of patients who underwent resection of a bAVM over a 15-year period was performed. Patients who did not present with seizure were included, and the primary outcome was de novo epilepsy (i.e., a seizure disorder that only manifested after surgery). Demographic, clinical, and radiographic characteristics were compared between patients with and without postoperative epilepsy. Subgroup analysis was conducted on the ruptured bAVMs. From a cohort of 198 patients who underwent resection of a bAVM during the study period, 111 supratentorial ruptured and unruptured bAVMs that did not present with seizure were included. Twenty-one patients (19%) developed de novo epilepsy. One-year cumulative rates of developing de novo epilepsy were 9% for the overall cohort and 8.5% for the cohort with ruptured bAVMs. There were no significant differences between the epilepsy and no-epilepsy groups overall; however, the de novo epilepsy group was younger in the cohort with ruptured bAVMs (28.7 ± 11.7 vs 35.1 ± 19.9 years; p = 0.04). The mean time between resection and first seizure was 26.0 ± 40.4 months, with the longest time being 14 years. Subgroup analysis of the ruptured and endovascular embolization cohorts did not reveal any significant differences. Of the patients who developed poorly controlled epilepsy (defined as Engel class III-IV), all had a history of hemorrhage and half had bAVMs located in the temporal lobe. De novo epilepsy after bAVM resection occurs at an annual cumulative risk of 9%, with potentially long-term onset. Younger age may be a risk factor in patients who present with rupture. The development of poorly controlled epilepsy may be associated with temporal lobe location and a delay between hemorrhage and resection.

Epilepsy with SLC35A2 Brain Somatic Mutations in Mild Malformation of Cortical Development with Oligodendroglial Hyperplasia in Epilepsy (MOGHE)

Purpose: This study presents the characteristics of patients with mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy (MOGHE) with SLC35A2 somatic variants in the brain who underwent epilepsy surgery and showed clinical improvement in seizures. Methods: We collected 10 patients with SLC35A2 somatic mutations in the brain who underwent surgery to treat drug-resistant epilepsy at Severance Children’s Hospital from 2014 to 2019 and retrospectively reviewed their genetic profiles, neuropathologic results, clinical features, pre-operative evaluations, and post-operative outcomes.Results: Six of the 10 patients with SCL35A2 somatic mutations in the brain had Lennox Gastaut syndrome (LGS) evolving from infantile spasms (IS), three had LGS, and one had IS. The median value of variant allele frequencies (VAFs) was 5.7% (1.7% to 5.8%; range, 1.4% to 22.9%). Nonsense mutations were the most common (50%), followed by missense mutations (40%) and a splicing site mutation (10%). Eight patients (80%) had good post-operative outcomes, with freedom from disabling seizures in five (Engel class I) and rare disabling seizures in three (Engel class II). Four of the eight patients who could be assessed for social quotient (SQ) after surgery showed SQ improvements by 12.2±6.4. Although all patients were finally diagnosed with MOGHE, seven (70%) were initially diagnosed with gliosis, two with mild malformation of cortical development, and one with no abnormality.Conclusion: All patients with SCL35A2 brain somatic mutations, even with low VAFs, had refractory epilepsy such as LGS or IS, and were finally diagnosed with MOGHE. This report is the first in Korea to our knowledge.

The localization and lateralization of fear aura and its surgical prognostic value in patients with focal epilepsy.

ObjectiveFear aura has traditionally been considered relevant to epileptic discharges from mesial temporal areas, and few studies have investigated its effect on surgical outcome in drug‐resistant epilepsy. We aim to assess the localizing and lateralizing value as well as prognostic significance of fear aura in patients with focal epilepsy.MethodsThe occurrence of fear aura in relation to epileptogenic origin and its association with postoperative outcome were analyzed in 146 consecutive patients undergoing resective surgery for intractable epilepsy.ResultsNinety‐four (64.4%) patients reported auras, and 31 (21.2%) reported fear aura in their seizures. One hundred ten (75.3%) patients had an Engel class I outcome until last follow‐up, of whom 24 experienced fear aura preoperatively. Fear aura appeared more frequently during temporal and frontal lobe seizures, but did not lateralize the seizure onset zone. There were no significant baseline differences between patients with and without fear aura. No correlation was found between postoperative outcome and the presence of auras. Occurrence of fear aura failed to show predictive value in surgical outcome whether in pooled or subgroup analysis.InterpretationThis study advances our understanding of the origin of fear aura, and is helpful for presurgical evaluation and outcome prediction. Without lateralizing value, fear aura is more commonly seen with temporal or frontal origin. When taken as a whole, auras do not have a significant impact on seizure outcome in focal epilepsy. Patients with fear aura are no more likely to become seizure‐free than those without fear aura.

Impact of high-density EEG in presurgical evaluation for refractory epilepsy patients

ObjectiveElectrical source localization (ESI) can help to identify the seizure onset zone or propagation zone, but it is unclear how dipole localization techniques influence surgical planning. MethodsPatients who received a high density (HD)-EEG from 7/2014–7/2019 at Stanford were included if they met the following inclusion criteria: (1) adequate epileptiform discharges were recorded for source localization analysis, (2) underwent surgical treatment, which was at least 6 months before the survey. Interictal ESI was performed with the LORETA method on age matched MRIs. Six neurophysiologists from the Stanford Epilepsy Program independently reviewed each case through an HIPPA-protected online survey. The same cases were presented again with additional data from the HD-EEG study. Ratings of how much the HD-EEG findings added value and in what way were recorded. ResultsFifty out of 202 patients met the inclusion criteria, providing a total of 276 h of HDEEG recordings. All patients had video EEG recordings and at least one brain MRI, 88 % had neuropsychological testing, 78 % had either a PET or SPECT scan. Additional HD-EEG information was rated as helpful in 83.8 %, not useful in 14.4 % and misleading in 1.8 % of cases. In 20.4 % of cases the HD-EEG information altered decision-making in a major way, such as choosing a different surgical procedure, avoidance of invasive recording or suggesting placement of invasive electrodes in a lobe not previously planned. In 21.5 % of cases, HD-EEG changed the plan in a minor way, e.g., extra invasive electrodes near the previously planned sites in the same sub-lobar region. In 42.3 % cases, HD-EEG did not change their plan but provided confirmation. In cases with normal MRI, additional HD-EEG information was more likely to change physicians’ decision making during presurgical process when compared to the cases with MRI-visible lesions (53.3 % vs. 34.3 %, p = 0.002). Among patients achieving Engel class I/II outcome, the concordance rate of HD-EEG and resection zone was 64.7 % versus 35.3 % with class III/IV (p = 0.028). ConclusionHD-EEG assists presurgical planning for refractory epilepsy patients, with a higher yield in patients with non-lesional MRIs. Concordance of HD-EEG dipole analysis localization and resection site is a favorable outcome indicator.

Outcome after resective epilepsy surgery in the elderly.

The objective of this study was to compare complications, seizures, and neuropsychological outcomes after resective epilepsy surgery in patients ≥ 60 years of age who underwent operations to younger and matched controls. Charts of 2243 patients were screened for operated patients in the authors' center between 2000 and 2015. Patients with available postsurgical follow-up data who were operated on at the age of 60 years or older and matched (by gender, histopathology, and side of surgery) controls who were between 20 and 40 years of age at the time of surgery were included. Outcomes regarding postoperative seizure control were scored according to the Engel classification and group comparisons were performed by using chi-square statistics. Data of 20 older patients were compared to those of 60 younger controls. Postoperative seizure control was favorable in the majority of the elderly patients (Engel classes I and II: 75% at 12 months, 65% at last follow-up), but the proportion of patients with favorable outcome tended to be larger in the control group (Engel classes I and II: 90% at 12 months, p = 0.092; 87% at last follow-up, p = 0.032, chi-square test). The surgical complication rate was higher in the elderly population (65% vs 27%, p = 0.002), but relevant persistent deficits occurred in 2 patients of each group only. Neuropsychological and behavioral assessments displayed considerable preoperative impairment and additional postoperative worsening, particularly of verbal skills, memory (p < 0.05), and mood in the elderly. The overall favorable postsurgical outcome regarding seizure control and the moderate risk of disabling persistent neurological deficits in elderly patients supports the view that advanced age should not be a barrier per se for resective epilepsy surgery and underscores the importance of an adequate presurgical evaluation and of referral of elderly patients to presurgical assessment.

Determinants of seizure outcome after resective surgery following stereoelectroencephalography.

The aim of this study was to investigate seizure outcomes after resective epilepsy surgery following stereoelectroencephalography (SEEG), including group characteristics, comparing surgical and nonsurgical groups and assess predictors of time to seizure recurrence. Clinical and EEG data of 536 consecutive patients who underwent SEEG at Cleveland Clinic Epilepsy Center between 2009 and 2017 were reviewed. The primary outcome was defined as complete seizure freedom since the resective surgery, discounting any auras or seizures that occurred within the 1st postoperative week. In addition, the rate of seizure freedom based on Engel classification was determined in patients with follow-up of ≥ 1 year. Presumably significant outcome variables were first identified using univariate analysis, and Cox proportional hazards modeling was used to identify outcome predictors. Of 527 patients satisfying study criteria, 341 underwent resective surgery. Complete and continuous seizure freedom after surgery was achieved in 55.5% of patients at 1 year postoperatively, 44% of patients at 3 years, and 39% of patients at 5 years. As a secondary outcome point, 58% of patients achieved Engel class I seizure outcome for at least 1 year at last follow-up. Among surgical outcome predictors, in multivariate model analysis, the seizure recurrence rate by type of resection (p = 0.039) remained statistically significant, with the lowest risk of recurrence occurring after frontal and temporal lobe resections compared with multilobar and posterior quadrant surgeries. Patients with a history of previous resection (p = 0.006) and bilateral implantations (p = 0.023) were more likely to have seizure recurrence. The absence of an MRI abnormality prior to resective surgery did not significantly affect seizure outcome in this cohort. This large, single-center series shows that resective surgery leads to continuous seizure freedom in a group of patients with complex and severe pharmacoresistant epilepsy after SEEG evaluation. In addition, up to 58% of patients achieved seizure freedom at last follow-up. The authors' results suggest that SEEG is equally effective in patients with frontal and temporal lobe epilepsy with or without MRI identified lesions.

P.097 After-discharges and presurgical cortical stimulation in stereo-encephalography in the study of drug-resistant epilepsy

Background: Background: Cortical stimulation (CS) as a part of presurgical investigations in patients undergoing implantation of depth electrodes (SEEG) is a growing practice in some Comprehensive Epilepsy Centers. After-discharges (AD) are useful to determine epileptogenic tissue within or outside the epileptogenic network. Classification of afterdischarges was proposed by Blume using subdural recordings(1); its utility in SEEG is unknown. Methods: Methods: Single center, retrospective study that included patients with SEEG that underwent CS in the Epilepsy Monitoring Unit. Demographic characteristics were explored and Blume’s proposed AD classification was used to determine whether or not the CS changed surgical outcomes. Results: Results: From January 2015 to June 2021, a total of 177 patients were implanted with SEEG and analyzed. 95 patients had CS and 91 had AD. Morphologies found were: Rhythmic waves in 4 (0.04%), Rhythmic waves evolving into spikes in18 (19%), Polyspike bursts in 14 (15%), Spike-waves in 28 (30%), and sequential spikes in 18 (19%). 12/14 (86%) patients with Spike-waves had Engel I outcome; Engel class IV patients were more likely to have an evolution of morphology and frequency of ADs in 3 patients(75%). Conclusions: Conclusions: The most frequent morphology of ADs seen was spike-waves. AD morphology and duration may predict post-operative seizure outcomes.

Lateral versus vertical hemispheric disconnection for epilepsy: a systematic review and meta-analysis.

Lateral periinsular hemispherotomy (LPH) and vertical parasagittal hemispherotomy (VPH) are the most popular disconnective techniques for intractable epilepsies associated with unilateral hemispheric pathologies. The authors aimed to investigate possible differences in seizure outcome and complication rates between patients who underwent LPH and VPH. A comprehensive literature search of PubMed and Embase identified English-language articles published from database inception to December 2019 that reported series (minimum 12 patients with follow-up ≥ 12 months) on either LPH or VPH. Pooled rates of seizure freedom and complications (with a particular focus on hydrocephalus) were analyzed using meta-analysis to calculate both fixed and random effects. Heterogeneity (Cochran's Q test) and inconsistency (fraction of Q due to actual heterogeneity) were also calculated. Twenty-five studies were included. Data from 825 patients were available for seizure outcome analysis (583 underwent LPH and 242 underwent VPH), and data from 692 patients were available for complication analysis (453 underwent LPH and 239 underwent VPH). No differences were found in the pooled rates of Engel class I seizure outcome between patients who underwent LPH (80.02% and 79.44% with fixed and random effects, respectively) and VPH (79.89% and 80.69% with fixed and random effects, respectively) (p = 0.953). No differences were observed in the pooled rates of shunted hydrocephalus between patients who underwent LPH (11.34% and 10.63% with fixed and random effects, respectively) and VPH (11.07% and 9.98% with fixed and random effects, respectively) (p = 0.898). Significant heterogeneity and moderate inconsistency were determined for hydrocephalus occurrence in patients who underwent both LPH and VPH. LPH and VPH techniques present similar excellent seizure outcomes, with comparable and acceptable safety profiles.

Stereotactic Electroencephalography in Patients with Drug-resistant Epilepsy

Stereotactic electroencephalography (SEEG) is an important method for invasive presurgical exploration of candidates for epilepsy surgery by means of stereotactic implantation of intracerebral electrodes without craniotomy. Implantations of intracerebral electrodes through craniotomy in drug-resistant epileptic patients have been performed in Bulgaria in the 1980s, but no further development of epilepsy surgery followed. The aim of our study is to present the first Bulgarian series of patients with drug-resistant epilepsy explored by SEEG. Our study included 53 patients with drug-resistant epilepsy explored by SEEG. Stereotactic Leksell frame, stereotactic software for avascular trajectory planning and depth electrodes with diameter of 0.8 mm and 8–18 contacts were used in all patients. Subsequently, long-term video-SEEG monitoring of various duration was performed and registered interictal and ictal EEG activity in order to evaluate the putative epileptogenic zone. Fifty-three patients were explored by 62 SEEGs because one patient underwent three SEEG procedures and seven patients – two SEEG procedures. We implanted 753 electrodes in these 62 SEEGs (mean: 12 electrodes per exploration; range: 5–20 electrodes). The mean age in our cohort was 23.6 years (4–60 years). The main indication for SEEG was MRI-negative epilepsy (20 patients). Focal cortical dysplasia was found in 17 cases, and hippocampal sclerosis in 8 cases. Surgical intervention was done in 48 patients (91%). Surgical resection of the epileptogenic zone (EZ) as defined by the SEEG was performed in 27 patients; radiofrequency stereotactic thermocoagulation (RFTC) on selected electrode contacts was applied in seven patients, and both procedures (i.e. RFTC followed by resective surgery) were performed on 14 patients. Full seizure control (Engel class I) was achieved in 28 patients (58.3%) and significant improvement – in 17 patients (35.4%). Three patients (6.2%) had no effect from surgery. No complications were observed in our series of 62 SEEGs. SEEG is a major tool for the determination of the EZ in patients with drug-resistant epilepsy who are candidates for epilepsy surgery, including MRI-negative cases or such without congruent data from the clinical, neurophysiological and neuroimaging perspectives. SEEG is a low-risk invasive diagnostic and even a therapeutic method when performed by experienced epilepsy surgery team.

Validity of intraoperative ECoG in the parahippocampal gyrus as an indicator of hippocampal epileptogenicity

PurposeIntraoperative electrocorticography (ECoG) in the parahippocampal gyrus is sometimes used as a substitute for intraoperative ECoG in the hippocampus. This study aimed to elucidate the validity of parahippocampal ECoG as an indicator of hippocampal epileptogenicity. MethodsWe retrospectively identified 10 patients with drug-resistant unilateral mesial temporal lobe epilepsy who achieved Engel class I or II after anteromedial temporal lobectomy. Intraoperative ECoG was recorded in the parahippocampal gyrus and hippocampal alveus at sevoflurane concentrations of 1.5–3.0%. We sought to identify the sevoflurane proconvulsant effects on spikes and high-frequency oscillations (HFOs) on spikes in the epileptogenic area. The number of spikes and number of HFOs superimposed on spikes were counted in ECoG recordings of the parahippocampal gyrus, hippocampal alveus, and lateral temporal lobe, and analyzed using two-way repeated-measures analysis of variance. ResultsThe number of spikes and number of HFOs superimposed on spikes significantly increased as the sevoflurane concentration increased in both the hippocampal alveus and parahippocampal gyrus (spike, p < 0.001; ripple, p < 0.001; Fast ripple (FR), p < 0.001), and the pattern of increase was similar in these two areas.The number of spikes and number of HFOs on spikes were statistically higher in the hippocampal alveus than in the parahippocampal gyrus (spike, p = 0.004; ripple, p = 0.005; FR, p = 0.001). There were almost no spikes or HFOs on spikes in the lateral temporal lobe at sevoflurane concentrations in the range of 1.5–2.5%. ConclusionsIntraoperative ECoG in the parahippocampal gyrus can serve as an indicator of hippocampal epileptogenicity.

Intelligence quotient (IQ) as a predictor of epilepsy surgery outcome

IntroductionAbout one-third of patients with epilepsy have a refractory form which is associated with important economic and psychosocial burden. Most of these patients also suffer from comorbidities. One of the most frequent is cognitive impairment. Resective surgery or neuromodulation techniques may improve seizure control. Several factors have been proposed as potential predictors of the success of surgery regarding seizure frequency. We aimed to study preoperative cognitive performance as a predictor of the epilepsy surgery outcome. MethodsIn this ambispective study we studied total intelligence quotients (IQ) measured before surgery with the Wechsler Adult Intelligence Scale (WAIS) as a potential predictor of Engel Class at 1 year after surgery. Then we included IQ in a multivariate model and tested its performance. ResultsPreoperative IQ was a significant and independent predictor of the Engel Class at 1 year after surgery (OR 0.94; CI 0.90–0.98; p = 0.007). The multivariate model including the age at epilepsy onset, education level, sex, and the type of surgery (resective versus palliative surgery) showed an area under the ROC curve of 0.85. ConclusionsA low intelligence level may constitute a marker of worse prognosis after epilepsy surgery. However, other predictors should also be considered when evaluating surgical candidates.

Pre- and Post-surgical Poor Seizure Control as Hallmark of Malignant Progression in Patients With Glioma?

BackgroundRegarding brain tumor-related epilepsy (BTRE), there is an increasing number of evidence about a relationship between epileptogenesis and oncogenesis. A recent study suggests a role of post-surgery seizure outcome on the survival of patients with low-grade glioma (LGG), underlying the need for a targeted and aggressive epilepsy treatment.ObjectiveThis study aims at investigating the possible correlation between pre- and post-surgical seizure control and tumor progression in patients who underwent surgery for LGG.MethodsWe performed a retrospective analysis of patients affected by LGGs and BTRE, in a single high-volume neurosurgical center. Seizure control was assessed before surgery and at 3 years of follow-up. Patients with histological progression in high-grade glioma (HGG) have been evaluated. Clinical features, pre-surgical electroencephalograms (EEGs), and electrocorticography (ECoG) have been analyzed.ResultsAmong 154 subjects, we collected 32 patients who presented a tumor progression in HGG during the follow-up period. The majority had poor seizure control both pre- and post-surgery, never being in Engel class Ia throughout the whole history of their disease. Almost all patients with poor seizure control had pathological ECoG recording. Clinical features of seizures did not correlate with seizure outcome. On the univariate analysis, the age, the post-operative Engel class, and the extent of resection (EOR) were the prognostic factors significantly associated with oncological outcome; nevertheless, on multivariate analysis, Engel class significance was not confirmed, and the only predicting factor were age and EOR.ConclusionsAlthough not confirmed on multivariate analysis, post-surgical seizure control could be a relevant factor to consider during follow-up of BRTE, in particular, when gross total resection is not achieved. Pathological findings on the ECoG may suggest a “hidden” propensity to malignant progression, strictly related to the persistent neuronal hyper-excitability. Further studies with longer follow-up period are needed to confirm our observations.

Acute Postoperative Seizures and Engel Class Outcome at 1 Year Postselective Laser Amygdalohippocampal Ablation for Mesial Temporal Lobe Epilepsy.

MRI-guided laser interstitial thermal therapy (MRgLITT) for mesial temporal lobe epilepsy is a safe, minimally invasive alternative to traditional surgical approaches. Prognostic factors associated with efficacy are debated; preoperative epilepsy duration and semiology seem to be important variables. To determine whether acute postoperative seizure (APOS) after MRgLITT for mesial temporal lobe epilepsy is associated with seizure freedom/Engel class outcome at 1 year. A single-institution retrospective study including adults undergoing first time MRgLITT for mesial temporal lobe epilepsy (2010-2019) with ≥1-year follow-up. Preoperative data included sex, epilepsy duration, number of antiepileptics attempted, weekly seizure frequency, seizure semiology, and radiographically verified anatomic lesion at seizure focus. Postoperative data included clinical detection of APOS within 7 days postoperatively, and immediate amygdala, hippocampal, entorhinal, and parahippocampal residual volumes determined using quantitative imaging postprocessing. Primary outcome was seizure freedom/Engel classification 1 year postoperatively. Of 116 patients, 53% (n = 61) were female, with an average epilepsy duration of 21 (±14) years, average 6 failed antiepileptics (±3), and weekly seizure frequency of 5. APOS was associated with worse Engel class ( P = .010), conferring 6.3 times greater odds of having no improvement vs achieving seizure freedom at 1 year. Residual amygdala, hippocampal, entorhinal, and parahippocampal volumes were not statistically significant prognostic factors. APOS was associated with a lower chance of seizure freedom at 1 year post-MRgLITT for mesial temporal lobe epilepsy. Amygdala, hippocampal, entorhinal, and parahippocampal residual volumes after ablation were not significant prognostic factors.