Presurgical evaluation for drug refractory epilepsy

Subunit specific altered expression and activity of casein kinase 2 in the brain tissues resected from mesial temporal lobe epilepsy with hippocampal sclerosis patients & rodent temporal lobe epilepsy model

INTRODUCTION

Mesial temporal lobe epilepsy (MTLE), is associated with dysregulated excitatory-inhibitory balance in the brain. Numerous enzymes, protein kinases, that are modulated through phosphorylation, have been linked with key processes involved in the pathogenesis of epilepsy. Therefore, in this study, we determined the subunit specific expression and activity of multi-subunit casein Kinase 2 (CK2) which influences NMDARs through phosphorylation events, in MTS patients as well as pilocarpine model of TLE.

METHODS

mRNA expression of CK2 (α, α', β) & NR2B was measured by real time PCR andprotein expression of CK2 (α, α', β), NR2B, and NR2B Ser1480 were evaluated using western blotting and immunohistochemistry in experimental models of TLE and MTS patients. CK2 α and α' activity was measured by kinase assay.

RESULTS

Significant increase in CK2α', CK2β, and NR2B mRNA expression were noted in chronic TLE rat model. Similarly, MTS patients displayed upregulated CK2α' and CK2β expressions, but NR2B mRNA remained unchanged. CK2α', CK2β, and NR2B Ser1480 protein expressions were higher in chronic TLE and MTS patients in relation to controls (p < 0.05), as was kinase activity (p < 0.05). In acute TLE rats, only NR2B protein expression was upregulated (p < 0.05).

CONCLUSION

Our research demonstrated for the first time the upregulation of CK2α' subunit and its increased kinase activityin resected brain samples from MTS patients as well as pilocarpine model of TLE. Altered expression and higher activity of CK2 α' highlights subunit specific contribution, suggesting the modulation of NMDA receptors by Casein Kinase 2 may contribute to hyperexcitability in MTLE.

Altered expression of activating transcription factor 3 in the hippocampus of patients with mesial temporal lobe epilepsy-hippocampal sclerosis (MTLE-HS)

Aim of the study: Activating Transforming factor 3 (ATF3) is a stress induced gene and closely associated with neuro-inflammation while Transforming growth Factor Beta (TGFβ) signalling is also reported to be involved in neuro-inflammation and hyper-excitability associated with drug resistant epilepsy. Animal model studies indicate the involvement of ATF3 and TGFβ receptors to promote epileptogenesis. Human studies also show that TGFβ signalling is activated in MTLE-HS. However, lack of studies on ATF3 and TGFβRI expression in MTLE-HS patients exists. We hypothesize that ATF3 and TGFβRI might be expressed in hippocampi of patients with MTLE-HS and playing role in epileptogenesis. Materials & methods: Protein expression of ATF3 and TGFβRI was performed by western blotting. Localisation of ATF3 was performed by immunohistochemistry and immunoflorescence. Results: Protein expression of ATF3 and TGFβRI was significantly up-regulated in hippocampi of patients as compared to controls. Also ATF3 IR was significantly expressed in hippocampi of patients and ATF3 was expressed predominantly in cytoplasm as compared to nucleus. No correlation was found between ATF3 expression and epilepsy duration and seizure frequency. Conclusions: ATF3 and TGFβRI are both important players in neuro-inflammation and might potentiate epileptogenesis in these patients.

Disparities in pediatric drug-resistant epilepsy care

INTRODUCTION

Epilepsy affects millions of children worldwide, with 20-40% experiencing drug-resistant epilepsy (DRE) who are recommended for epilepsy surgery evaluation and may benefit from surgical management. However, many patients live with DRE for multiple years prior to surgical epilepsy referral or treatment or are never referred at all.

OBJECTIVE

We aimed to describe factors associated with referral for epilepsy surgery in the USA, in order to identify disparities in DRE, characterize why they may exist, and recognize areas for improvement.

METHODS

Pediatric patients diagnosed with DRE between January 1, 2004 and December 31, 2020 were identified from the Pediatric Health Information System (PHIS) Database. Patients treated with antiseizure medications (ASMs) only, ASMs plus vagus nerve stimulation (VNS), and ASMs plus cranial epilepsy surgery were studied regarding access to epilepsy surgery and disparities in care. This study used chi-square tests to determine associations between treatment time and preoperative factors. Preoperative factors studied included epilepsy treatment type, age, sex, race/ethnicity, insurance type, geographic region, patient type, epilepsy type, and presence of pediatric complex chronic conditions (PCCCs).

RESULTS

A total of 18,292 patients were identified; 10,240 treated with ASMs, 5019 treated with ASMs + VNS, and 3033 treated with ASMs + cranial epilepsy surgery. Sex was not found to significantly vary among groups. There was significant variation in age, census region, race/ethnicity, patient type, presence of PCCCs, diagnosis, and insurance (p < 0.001). Those treated surgically, either with VNS or cranial epilepsy surgery, were 2 years older than those medically treated. Additionally, those medically treated were less likely to be living in the Midwest (25.46%), identified as non-Hispanic white (51.78%), have a focal/partial epilepsy diagnosis (8.74%), and be privately insured (35.82%).

CONCLUSIONS

We studied a large administrative US database examining variables associated with surgical epilepsy evaluation and management. We found significant variation in treatment associated with age, US census region, race/ethnicity, patient type, presence of PCCCs, diagnosis, and health insurance type. We believe that these disparities in care are related to access and social determinants of health, and we encourage focused outreach strategies to mitigate these disparities to broaden access and improve outcomes in children in the USA with DRE.

The Impact of Magnetoencephalography-Directed Stereo-Electroencephalography Depth Electrode Implantation on Seizure Control Outcome in Children

Introduction The use of magnetoencephalography (MEG) in localizing epileptic foci and directing surgical treatment of medically refractory epilepsy is well established in clinical practice; however, it has not yet been incorporated into the routine planning of stereo-electroencephalography (EEG) (SEEG) depth electrode trajectories during invasive intracranial evaluation for epileptic foci localization. In this study, we assess the impact of MEG-directed SEEG on seizure outcomes in a pediatric cohort. Methods A retrospective analysis was performed on a single-institution cohort of pediatric patients with medically refractory epilepsy who underwent epilepsy surgery. The primary endpoint was the reduction in seizure burden as determined by dichotomized Engel scores (favorable outcome: Engel scores I and II; poor outcome: Engel scores III and IV). Results Thirty-seven patients met the inclusion criteria (24 males and 13 females). The median age at seizure onset was three years, the median age at surgery was 14.1 years, and the median follow-up length was 30.8 months. Concordance was noted in 7/10 (70%) patients who received MEG-directed SEEG. Good clinical outcomes were achieved in 70% of MEG-directed SEEG patients, compared to 59.4% in their counterparts; however, this difference was not statistically significant (p=0.72). We noted no statistically significant association between sex, disease laterality, or age at surgery and good clinical outcomes. Conclusions Patients who underwent MEG-directed SEEG had favorable clinical outcomes, which demonstrated the practicability of this technique for determining SEEG electrode placement. Although no significant difference in clinical outcomes was obtained between the two groups, this may have been due to low statistical power. Future prospective, multi-institutional investigations to assess the benefit of MEG-directed SEEG are warranted.

Vagal Nerve Stimulation in the Management of Epilepsy - Recent Concepts

Epilepsy surgery currently offers the best treatment for patients with drug-refractory epilepsy (DRE). Resective surgery, in the presence of a well-localized epileptogenic focus, remains the best modality towards achieving seizure freedom. However, localization of the focus may not be possible in all the cases of DRE, despite comprehensive epilepsy workup. Neuromodulation techniques such as vagal nerve stimulation (VNS), deep brain stimulation (DBS) and responsive neurostimulation (RNS) may be a good alternative in these cases. This article intends to provide an overview of VNS in the management of DRE, including indications, comprehensive preoperative workup, exemplified by case illustrations and outcomes by reviewing the evidence available in the literature.

Role of Neuromodulation for Treatment of Drug-Resistant Epilepsy

The choice of neuromodulation techniques has greatly increased over the past two decades. While vagal nerve stimulation (VNS) has become established, newer variations of VNS have been introduced. Following the SANTE's trial, deep brain stimulation (DBS) is now approved for clinical use. In addition, responsive neurostimulation (RNS) has provided exciting new opportunities for treatment of drug-resistant epilepsy. While neuromodulation mostly offers only a 'palliative' measure, it still provides a significant reduction of frequency and intensity of epilepsy. We provide an overview of all the techniques of neuromodulation which are available, along with long-term outcomes. Further research is required to delineate the exact mechanism of action, the indications and the stimulation parameters to extract the maximum clinical benefit from these techniques.

Increased levels of α4-containing GABAA receptors in focal cortical dysplasia: A possible cause of benzodiazepine resistance

Benzodiazepines are the first choice of anti-epileptic drugs used to treat seizures. However, it has been seen that their efficacy decreases with time leading to drug insensitivity, plausibly caused by an alteration in the expression of the benzodiazepine biding site on GABA_A receptors. This study was designed to investigate if the differential expression of GABA_A receptor subunits α1/α4/γ2/δ across the postsynaptic sites could contribute to benzodiazepine resistance in patients with focal cortical dysplasia (FCD), the most common cause of drug resistant epilepsy in pediatric population. Differential gene and cellular expression of GABA_A receptor subunits α1, α4, γ2 and δ were evaluated and validated using qPCR and immunohistochemistry. Whole cell patch clamp studies were performed on pyramidal neurons of resected cortical FCD samples to measure the spontaneous GABA_A receptor activity. Upregulation of α4-and γ2-subunits containing GABA_A receptors were observed at both mRNA and protein level. α1-and δ-subunits containing GABA_A receptors did not show any significant changes. Flumazenil treatment did not affect the kinetics of GABAergic events in FCD; however, it significantly reduced the frequency and amplitude of spontaneous GABAergic activity in non-seizure control samples. Our results demonstrate the enhanced expression of α4-containing GABA_A receptors and GABAergic activity in pyramidal neurons which in turn may contribute to benzodiazepine resistance in FCD patients.

Altered hippocampal kynurenine pathway metabolism contributes to hyperexcitability in human mesial temporal lobe epilepsy-hippocampal sclerosis

BACKGROUND AND PURPOSE

Glutamate receptor-mediated enhanced excitatory neurotransmission is typically associated with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). Kynurenic acid and quinolinic acid are two important tryptophan-kynurenine pathway metabolites that modulate glutamate receptor activity. This study was designed to test the hypothesis that alteration in metabolism of tryptophan-kynurenine pathway metabolites in the hippocampus of patients with MTLE-HS contributes to abnormal glutamatergic transmission.

EXPERIMENTAL APPROACH

Levels of tryptophan-kynurenine pathway metabolites were determined using HPLC and LC-MS/MS in hippocampal samples from patients with MTLE-HS, compared with autopsy and non-seizure control samples. mRNA and protein expressions of tryptophan-kynurenine pathway enzymes were determined by qPCR and Western blot. Spontaneous glutamatergic activities were recorded from pyramidal neurons in the presence of kynurenine and kynurenic acid, using whole-cell patch clamp.

KEY RESULTS

Levels of kynurenic acid were reduced and quinolinic acid levels were raised in hippocampal samples from MTLE-HS patients, whereas kynurenine levels remained unaltered, compared with levels in non-seizure controls. Spontaneous glutamatergic activity in MTLE-HS hippocampal samples was higher than that in non-seizure controls. Treatment with kynurenine inhibited glutamatergic activity in non-seizure control samples but not in MTLE-HS samples. However, exogenously applied kynurenic acid inhibited glutamatergic activity in both non-seizure control and MTLE-HS hippocampal samples. Also, levels of kynurenine aminotransferase II and its cofactor pyridoxal phosphate were reduced in MTLE-HS samples.

CONCLUSION AND IMPLICATIONS

Our findings indicate that altered metabolism of tryptophan-kynurenine pathway metabolites in hippocampus could contribute to hyperglutamatergic tone in patients with MTLE-HS.

Anesthetic Considerations for Functional Neurosurgery

Functional neurosurgery is a rapidly growing field that uses surgical resection, ablation, or neuromodulation to treat an assortment of neurologic and psychiatric disorders, the most common of which are movement disorders and epilepsy. Anesthesiologists caring for patients undergoing neurofunctional procedures should be aware of the anesthetic implications of patients' underlying disease as well as procedure-specific concerns, such as the effects of anesthetics on intraoperative neuromonitoring and limited access to patients due to stereotactic frames or intraoperative imaging.

Epilepsy surgery in COVID times-a unique conundrum

The COVID-19 pandemic has forced hospitals to prioritize admissions. Epilepsy surgeries have been postponed at most centers. As the pandemic continues with no definite end in sight in the near future, the question arises until when such patients should be denied appropriate treatment. A 12-year-old child with left-sided Rasmussen's encephalitis with drug refractory epilepsy (DRE) presented at the height of the pandemic, with worsening of seizure frequency from 4-5/day to 20/day, with new-onset epilepsia partialis continua. She demonstrated features of progressive cognitive decline. The pros and cons of operating during the pandemic were discussed with the parents by a multidisciplinary team. She underwent endoscopic left hemispherotomy. Postoperatively she became seizure free but developed hospital-acquired mild COVID infection for which she was treated accordingly. Chosen cases of severe DRE, as the one illustrated above, who are deemed to benefit from surgery by a multidisciplinary team of physicians, should be re-categorized into the most severe class of patients and scheduled for surgery as soon as possible. The risk benefit ratio of the seizures being mitigated by surgery on one hand and possibility of acquiring COVID infection during hospital stay has to be balanced and a decision made accordingly.

Does Tc-99m ECD ictal brain SPECT have incremental value in localization of epileptogenic zone and predicting postoperative seizure freedom in cases with discordant video electroencephalogram and MRI findings?

OBJECTIVE

Localization of epileptogenic focus in drug-refractory epilepsy using Tc-99m ethylene cystine dimer (ECD) brain single photon emission computed tomography (SPECT) is less studied in patients with discordant findings on video electroencephalogram (VEEG) and MRI. The study was done to evaluate brain SPECT for epileptogenic focus localization and postoperative seizure freedom.

METHODS

Epilepsy patients with discordant VEEG and MRI findings underwent brain SPECT at ictal and interictal phases. Various groups unilateral/bilateral mesial temporal sclerosis (MTS), solitary and multifocal lesional, nonlesional epilepsy were studied for localization of epileptogenic focus and postoperative seizure freedom (>2 years) using Engels classification. Reasons for nonoperability was evaluated in nonoperated group.

RESULTS

SPECT could localize epileptogenic focus in 49/67 (73.13%) and guided surgery in 19/33 (57.57%) patients in operated group. SPECT was useful in 12 (46.12%) of unilateral (2)/bilateral (10) MTS. Postoperative seizure freedom of Engels Class I and II in 22 (66.67%), III in six (18.2%) and IV in one patient based on SPECT findings (P = 0.0086). Overall sensitivity and specificity were 79.3% and 85.7%, respectively. SPECT could localize epileptogenic focus in 23/34 (67.64%) patients in nonoperated group; 10 (29.41%) patients refused for surgery and no epileptogenic focus was localized in the rest of 14 (41.2%).

CONCLUSION

Ictal SPECT showed incremental value and was found necessary for epileptogenic focus localization and subsequent surgery in unilateral/bilateral MTS in this study. Seizure freedom in patients undergoing epilepsy surgery based on ictal SPECT assistance was comparable to the surgical group not requiring ictal SPECT.

Deciphering the surgical treatment gap for drug-resistant epilepsy (DRE): A literature review

Patients with drug-resistant epilepsy (DRE) rarely achieve seizure freedom with medical therapy alone. Despite being safe and effective for select patients with DRE, epilepsy surgery remains heavily underutilized. Multiple studies have indicated that the overall rates of surgery in patients with DRE have stagnated in recent years and may be decreasing, even when hospitalizations for epilepsy-related problems are on the rise. Ultimately, many patients with DRE who might otherwise benefit from surgery continue to have intractable seizures, lacking access to the full spectrum of available treatment options. In this article, we review the various factors accounting for the persistent underutilization of epilepsy surgery and uncover several key themes, including the persistent knowledge gap among physicians in identifying potential surgical candidates, lack of coordinated patient care, patient misconceptions of surgery, and socioeconomic disparities impeding access to care. Moreover, factors such as the cost and complexity of the preoperative evaluation, a lack of federal resource allocation for the research of surgical therapies for epilepsy, and difficulties recruiting patients to clinical trials all contribute to this multifaceted dilemma.

EEG lateralization and seizure outcome following peri-insular hemispherotomy for pediatric hemispheric epilepsy

OBJECTIVE

To determine whether preoperative non-lateralizing scalp electroencephalography (EEG) influences seizure outcome following peri-insular hemispherotomy (PIH) in pediatric hemispheric epilepsy.

METHODS

Retrospective data was collected on all 45 pediatric patients who underwent PIH between 2005 and 2016. All underwent a basic pre-surgical evaluation consisting of detailed history and examination, neuropsychological assessment, MRI, and EEG. SPECT/PET, fRMI, or Wada testing were done in only eight patients. Seizure outcome was assessed using the Engel classification.

RESULTS

Among those who underwent hemispherotomy, 20 (44%) were females. Mean age at surgery was 8 ± 4.3 years and mean duration of symptoms was 5.2 ± 3.7 years. The most common etiologies of hemispheric epilepsy were hemiconvulsion-hemiplegia epilepsy syndrome, Rasmussen encephalitis, and post-encephalitic sequelae, together comprising 27 (60%) patients. Among the 44 patients with follow-up data (mean duration 48 ± 33 months), seizure freedom (Engel class I) was attained by 41 (93.2%). Anti-epileptic medications were stopped or decreased in 36 (82%). Seventeen (38.6%) patients had non-lateralizing EEG. Seizure outcome was not related to lateralization of EEG activity.

CONCLUSIONS

PIH provides excellent long-term seizure control in patients despite the presence of non-lateralizing epileptiform activity, although occurrence of acute postoperative seizures may be higher. Routine SPECT/PET may not be required in patients with a non-lateralizing EEG if there is good clinico-radiological concordance.

Promoting faster pathways to surgery: a clinical audit of patients with refractory epilepsy

Background

Individuals with epilepsy who cannot be adequately controlled with anti-epileptic drugs, refractory epilepsy, may be suitable for surgical treatment following detailed assessment. This is a complex process and there are concerns over delays in referring refractory epilepsy patients for surgery and subsequent treatment. The aim of this study was to explore the different patient pathways, referral and surgical timeframes, and surgical and medical treatment options for refractory epilepsy patients referred to two Tertiary Epilepsy Clinics in New South Wales, Australia.

Methods

Clinical records were reviewed for 50 patients attending the two clinics, in two large teaching hospitals (25 in Clinic 1; 25 in Clinic 2. A purpose-designed audit tool collected detailed aspects of outpatient consultations and treatment. Patients with refractory epilepsy with their first appointment in 2014 were reviewed for up to six visits until the end of 2016. Data collection included: patient demographics, type of epilepsy, drug management, and assessment for surgery. Outcomes included: decisions regarding surgical and/or medical management, and seizure status following surgery. Patient-reported outcome measures to assess anxiety and depression were collected in Clinic 1 only.

Results

Patient mean age was 38.3 years (SD 13.4), the mean years since diagnosis was 17.3 years (SD 9.8), and 88.0% of patients had a main diagnosis of focal epilepsy. Patients were taking an average of 2.3 (SD 0.9) anti-epileptic drugs at the first clinic visit. A total of 17 (34.0%) patients were referred to the surgical team and 11 (22.0%) underwent a neuro-surgical procedure. The average waiting time between visit 1 to surgical referral was 38.8 weeks (SD 25.1), and between visit 1 and the first post-operative visit was 55.8 weeks (SD 25.0).

Conclusion

The findings confirm international data showing significant waiting times between diagnosis of epilepsy and referral to specialist clinics for surgical assessment and highlight different approaches in each clinic in terms of visit numbers and recorded activities. A standardised pathway and data collection, including patient-reported outcome measures, would provide better evidence for whether promoting earlier referral and assessment for surgery improves the lives of this disease group.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1255-0) contains supplementary material, which is available to authorized users.