European trends in epilepsy surgery

NeoCoMM: A neocortical neuroinspired computational model for the reconstruction and simulation of epileptiform events

BACKGROUND

Understanding the pathophysiological dynamics that underline Interictal Epileptiform Events (IEEs) such as epileptic spikes, spike-and-waves or High-Frequency Oscillations (HFOs) is of major importance in the context of neocortical refractory epilepsy, as it paves the way for the development of novel therapies. Typically, these events are detected in Local Field Potential (LFP) recordings obtained through depth electrodes during pre-surgical investigations. Although essential, the underlying pathophysiological mechanisms for the generation of these epileptic neuromarkers remain unclear. The aim of this paper is to propose a novel neurophysiologically relevant reconstruction of the neocortical microcircuitry in the context of epilepsy. This reconstruction intends to facilitate the analysis of a comprehensive set of parameters encompassing physiological, morphological, and biophysical aspects that directly impact the generation and recording of different IEEs.

METHOD

a novel microscale computational model of an epileptic neocortical column was introduced. This model incorporates the intricate multilayered structure of the cortex and allows for the simulation of realistic interictal epileptic signals. The proposed model was validated through comparisons with real IEEs recorded using intracranial stereo-electroencephalography (SEEG) signals from both humans and animals. Using the model, the user can recreate epileptiform patterns observed in different species (human, rodent, and mouse) and study the intracellular activity associated with these patterns.

RESULTS

Our model allowed us to unravel the relationship between glutamatergic and GABAergic synaptic transmission of the epileptic neural network and the type of generated IEE. Moreover, sensitivity analyses allowed for the exploration of the pathophysiological parameters responsible for the transitions between these events. Finally, the presented modeling framework also provides an Electrode Tissue Model (ETI) that adds realism to the simulated signals and offers the possibility of studying their sensitivity to the electrode characteristics.

CONCLUSION

The model (NeoCoMM) presented in this work can be of great use in different applications since it offers an in silico framework for sensitivity analysis and hypothesis testing. It can also be used as a starting point for more complex studies.

Surveying neurologist perspectives and knowledge of epilepsy surgery to identify barriers to surgery referral

OBJECTIVE

Epilepsy surgery is an effective means of treating medically refractory epilepsy (MRE), but it remains underused. We aimed to analyze the perspectives and knowledge of referring neurologists in the New York metropolitan area, who serve a large epilepsy population.

METHODS

We adapted a previous Canadian survey by Roberts et al. (2015), adding questions regarding demographic descriptors, insurance coverage, training and practice details, and perceived social barriers for patients. We surveyed neurologists directly affiliated with Montefiore Medical Center and those referring to Montefiore's Comprehensive Epilepsy Center. Participants had 10 weeks to fill out an online Qualtrics survey with weekly reminders.

RESULTS

Of 117 neurologists contacted, 51 eligible neurologists completed the survey (63.8% Montefiore, 35.0% referring group). A high proportion of the results were from epilepsy-trained individuals (41.2%) and neurologists who graduated residency ≤19 years ago (80.4%). 80.4% of respondents felt that epilepsy surgery is safe, but only 56.9% would refer a patient for surgical workup after two failed trials of anti-seizure medications. Epileptologists and providers with a larger volume of epilepsy patients and electroencephalogram readings had better knowledge of the epilepsy surgery workup guidelines. When asked to rank social barriers to patients receiving surgery, participants were most concerned about lack of social support, financial insecurity, and a patient's dual role as a caregiver.

SIGNIFICANCE

Our study suggests continued reluctance of neurologists regarding epilepsy surgery, and deficiencies in the knowledge and adherence to the recommended guidelines. In the context of prior studies, these results showed improved understanding of the definition of MRE (80.4%) and an increased likelihood to refer eligible patients as early as possible (78.4%) in line with current consensus recommendations. The finding that epilepsy-trained and more epilepsy/electroencephalogram-facing neurologists showed better understanding of the guidelines suggests that increased education efforts should be targeted at non-epileptologists.

PLAIN LANGUAGE SUMMARY

Our study asked New York City doctors about their approach to epilepsy surgery. Many do not consider it as early as they could in treatment plans. The doctors with extra epilepsy training were better at knowing when to consider surgery.

Spatial and temporal properties of intra-operatively recorded spikes and high frequency oscillations in focal cortical dysplasia

OBJECTIVE

Focal cortical dysplasias (FCD) are characterized by distinct interictal spike patterns and high frequency oscillations (HFOs; ripples: 80-250 Hz; fast ripples: 250-500 Hz) in the intra-operative electrocorticogram (ioECoG). We studied the temporal relation between intra-operative spikes and HFOs and their relation to resected tissue in people with FCD with a favorable outcome.

METHODS

We included patients who underwent ioECoG-tailored epilepsy surgery with pathology confirmed FCD and long-term Engel 1A outcome. Spikes and HFOs were automatically detected and visually checked in 1-minute pre-resection-ioECoG. Channels covering resected and non-resected tissue were compared using a logistic mixed model, assessing event numbers, co-occurrence ratios, and time-based properties.

RESULTS

We found pre-resection spikes, ripples in respectively 21 and 20 out of 22 patients. Channels covering resected tissue showed high numbers of spikes and HFOs, and high ratios of co-occurring events. Spikes, especially with ripples, have a relatively sharp rising flank with a long descending flank and early ripple onset over resected tissue.

CONCLUSIONS

A combined analysis of event numbers, ratios, and temporal relationships between spikes and HFOs may aid identifying epileptic tissue in epilepsy surgery.

SIGNIFICANCE

This study shows a promising method for clinically relevant properties of events, closely associated with FCD.

The Pediatric Epilepsy Surgery Interest Group (PESIG) under the auspice of the ISPN Research Committee: Availability of relevant technology and geographical distribution

PURPOSE

Epilepsy surgery for pediatric drug-resistant epilepsy has been shown to improve seizure control, enhance patient and family QoL, and reduce mortality. However, diagnostic tools and surgical capacity are less accessible worldwide. The International Society Pediatric Neurosurgery (ISPN) has established a Pediatric Epilepsy Surgery Interest Group (PESIG), aiming to enhance global collaboration in research and educational aspects. The goals of this manuscript are to introduce PESIG and analyze geographical differences of epilepsy surgery and technology availability.

METHODS

PESIG was established (2022) following an ISPN executive board decision. Using a standardized form, we surveyed the PESIG members, collecting and analyzing data regarding geographical distribution, and availability of various epilepsy treatment-related technologies.

RESULTS

Two hundred eighty-two members registered in PESIG from 70 countries, over 6 continents, were included. We categorized the countries by GDP as follows: low, lower-medium, upper-medium, and high income. The most commonly available technology was vagus nerve stimulation 68%. Stereoelectroencephalography was available for 58%. North America had statistically significant greater availability compared to other continents. Europe had greater availability compared to Africa, Asia, and South (Latin) America. Asia had greater availability compared to Africa. High-income countries had statistically significant greater availability compared to other income groups; there was no significant difference between the other income-level subgroups.

CONCLUSION

There is a clear discrepancy between countries and continents regarding access to epilepsy surgery technologies. This strengthens the need for collaboration between neurologists and neurosurgeons from around the world, to enhance medical education and training, as well as to increase technological availability.

Transcranial electrical stimulation during functional magnetic resonance imaging in patients with genetic generalized epilepsy: a pilot and feasibility study

Objective

A third of patients with epilepsy continue to have seizures despite receiving adequate antiseizure medication. Transcranial direct current stimulation (tDCS) might be a viable adjunct treatment option, having been shown to reduce epileptic seizures in patients with focal epilepsy. Evidence for the use of tDCS in genetic generalized epilepsy (GGE) is scarce. We aimed to establish the feasibility of applying tDCS during fMRI in patients with GGE to study the acute neuromodulatory effects of tDCS, particularly on sensorimotor network activity.

Methods

Seven healthy controls and three patients with GGE received tDCS with simultaneous fMRI acquisition while watching a movie. Three tDCS conditions were applied: anodal, cathodal and sham. Periods of 60 s without stimulation were applied between each stimulation condition. Changes in sensorimotor cortex connectivity were evaluated by calculating the mean degree centrality across eight nodes of the sensorimotor cortex defined by the Automated Anatomical Labeling atlas (primary motor cortex (precentral left and right), supplementary motor area (left and right), mid-cingulum (left and right), postcentral gyrus (left and right)), across each of the conditions, for each participant.

Results

Simultaneous tDCS-fMRI was well tolerated in both healthy controls and patients without adverse effects. Anodal and cathodal stimulation reduced mean degree centrality of the sensorimotor network (Friedman's ANOVA with Dunn's multiple comparisons test; adjusted p = 0.02 and p = 0.03 respectively). Mean degree connectivity of the sensorimotor network during the sham condition was not different to the rest condition (adjusted p = 0.94).

Conclusion

Applying tDCS during fMRI was shown to be feasible and safe in a small group of patients with GGE. Anodal and cathodal stimulation caused a significant reduction in network connectivity of the sensorimotor cortex across participants. This initial research supports the feasibility of using fMRI to guide and understand network modulation by tDCS that might facilitate its clinical application in GGE in the future.

Variation in access to specialist services for neurosurgical procedures in adults with epilepsy in England, a cohort study

PURPOSE

To understand if primary consultation at tertiary epilepsy centres (TEC) in England impacts access to neurosurgical procedures (resective surgery, vagus nerve stimulator [VNS], deep brain stimulator [DBS]).

METHODS

Adults with epilepsy, and with a first neurology outpatient visit (index) between 01/01/2013 and 31/12/2015, were followed using English Hospital Episode Statistics from index date to 31/12/2019. Analyses were stratified by geographic location, learning disability record, and whether the index or follow-up visits were at a TEC.

RESULTS

84,093 people were included, with mean 5.5 years of follow-up. 12.4% of the cohort had learning disability (range 10.1%-17.4% across regions). TEC consultations varied by National Health Service regions and Clinical Commissioning Groups. 37.5% of people (11.2%-75.0% across regions) had their index visit at a TEC; and, of those not initially seen at a TEC, 10.6% (6.5%-17.7%) subsequently attended a tertiary centre. During follow-up, 11.1% people (9.5%-13.2%) visited a neurosurgery department, and 2.3% of those (0.9%-5.0%) then underwent a neurosurgical procedure, mainly VNS implantation. Median time from index date to first visit at a neurosurgery centre was 7 months (range 6-8 months across regions) and 40 months to procedure (36.5-49 months, 37.0 months in people with index visit at a TEC and 49.0 months otherwise). People with learning disability were less likely to have resective surgery (<0.5% versus 1.0% in those without) and more likely to undergo VNS implantation (5.8% versus 0.8%).

CONCLUSION

Although clinically recommended for suitable individuals, neurosurgical procedures in epilepsy remain uncommon even after consultation at a TEC. Geographical variation in access to TECs was present.

Triggered Seizures for Ictal SPECT Imaging: A Case Series and Feasibility Study

Ictal SPECT is an informative seizure imaging technique to tailor epilepsy surgery. However, capturing the onset of unpredictable seizures is a medical and logistic challenge. Here, we sought to image planned seizures triggered by direct stimulation of epileptic networks via stereotactic electroencephalography (sEEG) electrodes. Methods: In this case series of 3 adult participants with left temporal epilepsy, we identified and stimulated sEEG contacts able to trigger patient-typical seizures. We administered 99mTc-HMPAO within 12 s of ictal onset and acquired SPECT images within 40 min without any adverse events. Results: Ictal hyperperfusion maps partially overlapped concomitant sEEG seizure activity. In both participants known for periictal aphasia, SPECT imaging revealed hyperperfusion in the speech cortex lacking sEEG coverage. Conclusion: Triggering of seizures for ictal SPECT complements discrete sEEG sampling with spatially complete images of early seizure propagation. This readily implementable method revives interest in seizure imaging to guide resective epilepsy surgery.

Yield of non-invasive imaging in MRI-negative focal epilepsy

OBJECTIVE

The absence of MRI-lesion reduces considerably the probability of having an excellent outcome (International League Against Epilepsies [ILAE] class I-II) after epilepsy surgery. Surgical success in magnetic-resonance imaging (MRI)-negative cases relies therefore mainly on non-invasive techniques such as positron-emission tomography (PET), subtraction ictal/inter-ictal single-photon-emission-computed-tomography co-registered to MRI (SISCOM), electric source imaging (ESI) and morphometric MRI analysis (MAP). We were interested in identifying the optimal imaging technique or combination to achieve post-operative class I-II in patients with MRI-negative focal epilepsy.

METHODS

We identified 168 epileptic patients without MRI lesion. Thirty-three (19.6%) were diagnosed with unifocal epilepsy, underwent surgical resection and follow-up ⩾ 2 years. Sensitivity, specificity, predictive values, and diagnostic odds ratio (OR) were calculated for each technique individually and in combination (after co-registration).

RESULTS

23/33 (70%) were free of disabling seizures (75.0% with temporal and 61.5% extratemporal lobe epilepsy). None of the individual modalities presented an OR > 1.5, except ESI if only patients with interictal epileptiform discharges (IEDs) were considered (OR 3.2). On a dual combination, SISCOM with ESI presented the highest outcome (OR = 6). MAP contributed to detecting indistinguishable focal cortical dysplasia in particular in extratemporal epilepsies with a sensitivity of 75%. Concordance of PET, ESI on interictal epileptic discharges, and SISCOM was associated with the highest chance for post-operative seizure control (OR = 11).

CONCLUSION

If MRI is negative, the chances to benefit from epilepsy surgery are almost as high as in lesional epilepsy, provided that multiple established non-invasive imaging tools are rigorously applied and co-registered together.

Epilepsy surgery perceptions among general neurologists and epilepsy specialists: A survey

OBJECTIVE

Surgical intervention for drug-resistant epilepsy (DRE) is a safe and efficacious evidence-based treatment. Yet, neurologists have historically revealed hesitance in referring patients for surgical evaluations. The present study surveyed general neurologists and epilepsy specialists to assess their views and process in referring patients for specialized epilepsy care and epilepsy surgery.

METHODS

A 14-item survey assessing epilepsy referrals and views of epilepsy surgery was distributed to all neurologists currently practicing in a large national integrated health system using REDCap. Responses were qualitatively analyzed and differences between general neurologists and epileptologists were assessed using chi-squared tests.

RESULTS

In total, 100 responses were received from 67 general neurologists and 33 epileptologists with several similarities and differences emerging between the two groups. Both groups endorsed surgery and neuromodulation as treatment options in DRE, felt that seizure frequency rather than duration was relevant in considering epilepsy surgery, and indicated patient preference as the largest barrier limiting epilepsy surgery. General neurologists were more likely to require ≥ 3 ASMs to fail to diagnose DRE compared to epileptologists (45% vs. 15%, p < 0.01) who more often required ≥ 2 ASMs to fail. Epileptologists were also more likely than neurologists to try a new ASM (75.8% vs. 53.7%, p < 0.05) or optimize the current ASM (75.8% vs. 49.3%, p < 0.05) in DRE. General neurologists were more likely to consider epilepsy surgery to be less efficacious (p = 0.001) or less safe (p < 0.05).

SIGNIFICANCE

Overall, neurologists appear to have generally positive opinions of epilepsy surgery, which is a change from prior literature and represents a changing landscape of views toward this intervention. Furthermore, epileptologists and general neurologists endorsed more similarities than differences in their opinions of surgery and steps to referral, which is another encouraging finding. Those gaps that remain between epileptologists and general neurologists, particularly in standards of ASM prescription, may be addressed by more consistent education about DRE and streamlining of surgical referral procedures.

IQ changes after pediatric epilepsy surgery: a systematic review and meta-analysis

OBJECTIVE

This systematic review aimed to assess the intellectual outcome of children who underwent surgery for epilepsy.

METHODS

A systematic review of electronic databases was conducted on December 3, 2021, for PubMed and January 11, 2022, for Web of Science. The review was conducted according to the PRISMA guidelines. The included studies reported on intelligence quotient (IQ) or developmental quotient (DQ) before and after epilepsy surgery in children. Studies were included, if the patients had medically intractable epilepsy and if the study reported mainly on curative surgical procedures. We conducted a random-effects meta-analysis to determine the mean change of IQ/DQ.

RESULTS

Fifty-seven studies reporting on a total of 2593 patients met the inclusion criteria. The mean age at surgery was 9.2 years (± 3.44; range 2.4 months-19.81 years). Thirty-eight studies showed IQ/DQ improvement on a group level, 8 yielded stable IQ/DQ, and 19 showed deterioration. Pooled analysis revealed a significant mean gain in FSIQ of + 2.52 FSIQ points (95% CI 1.12-3.91). The pooled mean difference in DQ was + 1.47 (95% CI - 6.5 to 9.5). The pooled mean difference in IQ/DQ was 0.73 (95% CI - 4.8 to 6.2). Mean FSIQ gain was significantly higher in patients who reached seizure freedom (+ 5.58 ± 8.27) than in patients who did not (+ 0.23 ± 5.65). It was also significantly higher in patients who stopped ASM after surgery (+ 6.37 ± 3.80) than in patients who did not (+ 2.01 ± 2.41). Controlled studies showed a better outcome in the surgery group compared to the non-surgery group. There was no correlation between FSIQ change and age at surgery, epilepsy duration to surgery, and preoperative FSIQ.

SIGNIFICANCE

The present review indicates that there is a mean gain in FSIQ and DQ in children with medically intractable epilepsy after surgery. The mean gain of 2.52 FSIQ points reflects more likely sustainability of intellectual function rather than improvement after surgery. Seizure-free and ASM-free patients reach higher FSIQ gains. More research is needed to evaluate individual changes after specific surgery types and their effect on long-term follow-up.

Learning to generalize seizure forecasts

OBJECTIVE

Epilepsy is characterized by spontaneous seizures that recur at unexpected times. Nonetheless, using years-long electroencephalographic (EEG) recordings, we previously found that patient-reported seizures consistently occur when interictal epileptiform activity (IEA) cyclically builds up over days. This multidien (multiday) interictal-ictal relationship, which is shared across patients, may bear phasic information for forecasting seizures, even if individual patterns of seizure timing are unknown. To test this rigorously in a large retrospective dataset, we pretrained algorithms on data recorded from a group of patients, and forecasted seizures in other, previously unseen patients.

METHODS

We used retrospective long-term data from participants (N = 159) in the RNS System clinical trials, including intracranial EEG recordings (icEEG), and from two participants in the UNEEG Medical clinical trial of a subscalp EEG system (sqEEG). Based on IEA detections, we extracted instantaneous multidien phases and trained generalized linear models (GLMs) and recurrent neural networks (RNNs) to forecast the probability of seizure occurrence at a 24-h horizon.

RESULTS

With GLMs and RNNs, seizures could be forecasted above chance in 79% and 81% of previously unseen subjects with a median discrimination of area under the curve (AUC) = .70 and .69 and median Brier skill score (BSS) = .07 and .08. In direct comparison, individualized models had similar median performance (AUC = .67, BSS = .08), but for fewer subjects (60%). Moreover, calibration of pretrained models could be maintained to accommodate different seizure rates across subjects.

SIGNIFICANCE

Our findings suggest that seizure forecasting based on multidien cycles of IEA can generalize across patients, and may drastically reduce the amount of data needed to issue forecasts for individuals who recently started collecting chronic EEG data. In addition, we show that this generalization is independent of the method used to record seizures (patient-reported vs. electrographic) or IEA (icEEG vs. sqEEG).

The evolution of epilepsy surgery in tuberous sclerosis in Sweden: A national registry study

PURPOSE

This study aimed to characterize the Swedish cohort of surgically treated patients with TSC and explore differences in preoperative investigation and outcome over time.

METHODS

Data on patient and seizure characteristics were retrieved from the Swedish National Epilepsy Surgery Register. Two-year follow-up results were compared between the years 1997-2010 and 2011-2018. Preoperative investigations were re-evaluated.

RESULTS

Eighteen tuberectomies and seven callosotomies were identified. Seizure freedom after tuberectomy was achieved in 11 % (1/9) 1997-2010 and 56 % (5/9) 2011-2018. The number of tuberectomies increased each decade. Patients operated on in 1997-2010 had higher seizure frequency (median 175 seizures/month vs. 102) and incidence of infantile spasms (4/9 vs. 1/9, none after 2011). There was a trend towards surgery at a younger age (median 86 months 1997-2010 vs. 48 months 2011-2018). None with >200 seizure/month, SEGA, or history of infantile spasms achieved seizure freedom. Two patients underwent anterior callosotomy (1992 and 1994) and became free of drop attacks. Five callosotomies were performed between 2011 and 2013, one patient became free of drop attacks. Two complications with new neurological deficits were reported. The median age at surgery was higher in the callosotomy group (14 years) than in the tuberectomy group (5 years).

CONCLUSION

Seizure freedom after tuberectomy in patients with TSC has increased over time in our cohort. Signs of a heavier disease burden were more frequently observed 1997-2010 and associated with worse outcomes. Callosotomy operations were prevalent at the beginning of the 2010s.

Genetic testing in children enrolled in epilepsy surgery program. A real-life study

OBJECTIVE

Although genetic causes of drug-resistant focal epilepsy and selected focal malformations of cortical development (MCD) have been described, a limited number of studies comprehensively analysed genetic diagnoses in patients undergoing pre-surgical evaluation, their outcomes and the effect of genetic diagnosis on surgical strategy.

METHODS

We analysed a prospective cohort of children enrolled in epilepsy surgery program over January 2018-July 2022. The majority of patients underwent germline and/or somatic genetic testing. We searched for predictors of surgical outcome and positive result of germline genetic testing.

RESULTS

Ninety-five patients were enrolled in epilepsy surgery program and 64 underwent resective epilepsy surgery. We ascertained germline genetic diagnosis in 13/74 patients having underwent germline gene testing (pathogenic or likely pathogenic variants in CHRNA4, NPRL3, DEPDC5, FGF12, GRIA2, SZT2, STXBP1) and identified three copy number variants. Thirty-five patients underwent somatic gene testing; we detected 10 pathogenic or likely pathogenic variants in genes SLC35A2, PTEN, MTOR, DEPDC5, NPRL3. Germline genetic diagnosis was significantly associated with the diagnosis of focal epilepsy with unknown seizure onset.

SIGNIFICANCE

Germline and somatic gene testing can ascertain a definite genetic diagnosis in a significant subgroup of patients in epilepsy surgery programs. Diagnosis of focal genetic epilepsy may tip the scales against the decision to proceed with invasive EEG study or surgical resection; however, selected patients with genetic focal epilepsies associated with MCD may benefit from resective epilepsy surgery and therefore, a genetic diagnosis does not disqualify patients from presurgical evaluation and epilepsy surgery.

Trends in referral patterns to presurgical evaluation at a European reference center

PURPOSE

To determine if growing evidence for epilepsy surgery as an early treatment option is reflected in the decrease of latencies between epilepsy onset and referral for presurgical evaluation METHODS: Retrospective analysis of latencies in 1646 patients (children and adults) from the time of epilepsy diagnosis to first presurgical workup in the period from 1999 to 2019 based on electronic patient charts at a tertiary epilepsy center. Time spans 1999-2009 and 2010-2019, prior to and following the ILAE definition of pharmacoresistance, and the role of etiological factors were assessed.

RESULTS

Over the whole period, the mean latency between diagnosis and a presurgical workup was 15.3 y. There was a significant reduction in the latencies between the periods 1999-2009 (16.9 y) and 2010-2019 (13.4 y), (p < 0.0001). In a linear regression analysis, the latency decreased by 2.6 months/year from 17.4 in 1999 to 13.1 y in 2019 (p < 0.001). Subgroup analyses showed significant decreases in latency to presurgical evaluation in patients with hippocampal sclerosis from 24.4 to 19.5 y, in malformations of cortical development from 16.4 to 13.2 y, and in nonlesional patients from 18.1 to 12.8 y, in contrast to patients with MR evidence for brain tumors with similar latencies across time (10.5 vs. 9.5 y, n.s.).

CONCLUSION

The reduction of the time span to a first presurgical evaluation was highly significant over time, yet moderate in its degree. Overall, the aim of early diagnostic evaluation for epilepsy surgery options after established pharmacoresistance was only achieved for a minority of patients.

Twenty-five years of epilepsy surgery at a Central European comprehensive epilepsy center-Trends in intervention delay and outcomes

OBJECTIVE

We analyzed trends in patients' characteristics, outcomes, and waiting times over the last 25 years at our epilepsy surgery center situated in Central Europe to highlight possible areas of improvement in our care for patients with drug-resistant epilepsy.

METHODS

A total of 704 patients who underwent surgery at the Brno Epilepsy Center were included in the study, 71 of those were children. Patients were separated into three time periods, 1996-2000 (n = 95), 2001-2010 (n = 295) and 2011-2022 (n = 314) based on first evaluation at the center.

RESULTS

The average duration of epilepsy before surgery in adults remained high over the last 25 years (20.1 years from 1996 to 2000, 21.3 from 2001 to 2010, and 21.3 from 2011 to 2020, P = 0.718). There has been a decrease in rate of surgeries for temporal lobe epilepsy in the most recent time period (67%-70%-52%, P < 0.001). Correspondingly, extratemporal resections have become more frequent with a significant increase in surgeries for focal cortical dysplasia (2%-8%-19%, P < 0.001). For resections, better outcomes (ILAE scores 1a-2) have been achieved in extratemporal lesional (0%-21%-61%, P = 0.01, at least 2-year follow-up) patients. In temporal lesional patients, outcomes remained unchanged (at least 77% success rate). A longer duration of epilepsy predicted a less favorable outcome for resective procedures (P = 0.024) in patients with disease duration of less than 25 years.

SIGNIFICANCE

The spectrum of epilepsy surgery is shifting toward nonlesional and extratemporal cases. While success rates of extratemporal resections at our center are getting better, the average duration of epilepsy before surgical intervention is still very long and is not improving. This underscores the need for stronger collaboration between epileptologists and outpatient neurologists to ensure prompt and effective treatment for patients with drug-resistant epilepsy.

Distinct patterns of interictal intracranial EEG in focal cortical dysplasia type I and II

OBJECTIVE

Focal cortical dysplasia (FCD) is the most common malformation causing refractory focal epilepsy. Surgical removal of the entire dysplastic cortex is crucial for achieving a seizure-free outcome. Precise presurgical distinctions between FCD types by neuroimaging are difficult, mainly in patients with normal magnetic resonance imaging findings. However, the FCD type is important for planning the extent of surgical approach and counselling.

METHODS

This study included patients with focal drug-resistant epilepsy and definite histopathological FCD type I or II diagnoses who underwent intracranial electroencephalography (iEEG). We detected interictal epileptiform discharges (IEDs) and their recruitment into repetitive discharges (RDs) to compare electrophysiological patterns characterizing FCD types.

RESULTS

Patients with FCD type II had a significantly higher IED rate (p < 0.005), a shorter inter-discharge interval within RD episodes (p < 0.003), sleep influence on decreased RD periodicity (p < 0.036), and longer RD episode duration (p < 0.003) than patients with type I. A Bayesian classifier stratified FCD types with 82% accuracy.

CONCLUSION

Temporal characteristics of IEDs and RDs reflect the histological findings of FCD subtypes and can differentiate FCD types I and II.

SIGNIFICANCE

Presurgical prediction of FCD type can help to plan a more tailored surgical approach in patients with normal magnetic resonance findings.

Automated Identification of Stereoelectroencephalography Contacts and Measurement of Factors Influencing Accuracy of Frame Stereotaxy

OBJECTIVE

Stereoelectroencephalography (SEEG) is an established invasive diagnostic technique for use in patients with drug-resistant focal epilepsy evaluated before resective epilepsy surgery. The factors that influence the accuracy of electrode implantation are not fully understood. Adequate accuracy prevents the risk of major surgery complications. Precise knowledge of the anatomical positions of individual electrode contacts is crucial for the interpretation of SEEG recordings and subsequent surgery.

METHODS

We developed an image processing pipeline to localize implanted electrodes and detect individual contact positions using computed tomography (CT), as a substitute for time-consuming manual labeling. The algorithm automates measurement of parameters of the electrodes implanted in the skull (bone thickness, implantation angle and depth) for use in modeling of predictive factors that influence implantation accuracy.

RESULTS

Fifty-four patients evaluated by SEEG were analyzed. A total of 662 SEEG electrodes with 8,745 contacts were stereotactically inserted. The automated detector localized all contacts with better accuracy than manual labeling (p < 0.001). The retrospective implantation accuracy of the target point was 2.4 ± 1.1 mm. A multifactorial analysis determined that almost 58% of the total error was attributable to measurable factors. The remaining 42% was attributable to random error.

CONCLUSION

SEEG contacts can be reliably marked by our proposed method. The trajectory of electrodes can be parametrically analyzed to predict and validate implantation accuracy using a multifactorial model.

SIGNIFICANCE

This novel, automated image processing technique is a potentially clinically important, assistive tool for increasing the yield, efficiency, and safety of SEEG.

Efficacy and tolerability of lacosamide as adjunctive therapy in patients with focal-onset seizures: an observational, prospective study

PURPOSE

To evaluate the efficacy and tolerability of adjunctive lacosamide (LCM) in patients with focal-onset seizures, with or without combined secondarily generalized seizures.

METHODS

106 patients aged ≥ 16 years were recruited consecutively in this single-center prospective observational study. All patients received LCM as an add-on treatment on the basis of clinical judgement. Seizure frequency, adverse events (AEs) and retention rates were obtained at 3 and 6 months after LCM introduction.

RESULT

The overall response rates were 53.3 and 70.4% after 3 and 6 months, respectively, and the freedom of seizures at the same points was reached at 19 and 26.5%. The retention rates were 99.1% at the 3-month follow-up and 93.3% at the 6-month follow-up. The overall incidence of adverse events was 35.8%. The leading AEs were dizziness (16.98%) and sedation (6.6%).

CONCLUSIONS

Our study confirmed the efficacy and tolerability of adjunctive LCM in Chinese patients in real-life conditions. Based on our treatment experience, a universal maintenance dose of LCM would be needed in Chinese patients.

Number of epilepsy surgeries has decreased despite an increase in pre-surgical evaluations at a tertiary pediatric epilepsy center in Ontario

OBJECTIVE

A recent U.S. study reported that the number of epilepsy surgeries has remained stable or declined in recent years despite an increase in pre-surgical evaluation. This study aimed to evaluate trends in pre-surgical evaluation and epilepsy surgery from 2001 to 2019 and to determine whether these trends have changed in the later period (2014-2019) compared to earlier period (2001-2013).

METHODS

This study evaluated trends in pre-surgical evaluation and epilepsy surgery at a tertiary pediatric epilepsy center. Children with drug resistant epilepsy who were evaluated for surgery were included. Clinical data, reasons for not undergoing surgery, and surgical characteristics of surgery patients were collected. Overall trends and trends in later period compared to earlier period for pre-surgical evaluation and epilepsy surgery were assessed.

RESULTS

There were 1151 children who were evaluated for epilepsy surgery and 546 underwent surgery. There was an upward trend in pre-surgical evaluation in the earlier period (rate ratio [RR]=1.04 (95%CI:1.02-1.07), p<0.001) and the trajectory of presurgical evaluation in the later period was not significantly different to the earlier period (RR=1.00 [95%CI:0.95-1.06], p = 0.88). Among the reasons for not undergoing surgery, failure to localize the seizures occurred more frequently in later period than earlier period (22.6% vs. 17.1% respectively, p = 0.024). For number of surgeries, there was an upward trend between 2001 and 2013 (RR=1.08 [95%CI:1.05-1.11], p<0.001), and a decreasing trend in the later period compared to earlier period (RR=0.91 [95%CI:0.84-0.99], p = 0.029).

CONCLUSION

Despite an increasing trend in pre-surgical evaluation, there was a decreasing trend in the number of epilepsy surgery in the later period as there was a larger proportion of patients in whom the seizures could not be localized. Trends in presurgical evaluation and epilepsy surgery will continue to evolve with introduction of technologies such as stereo-EEG and minimally invasive laser therapy.

Predictors and reasons for epilepsy patients to decline surgery: a prospective study

BACKGROUND

In patients with drug-resistant focal epilepsy, resective surgery is the most successful treatment option to achieve seizure freedom. However, a surprisingly high rate of patients declines their physicians' recommendation to undergo removal of the seizure focus or-if necessary-further video-EEG monitoring (VEM).

METHODS

In this prospective study, consecutive patients in presurgical assessment with at least one scalp VEM between 2016 and 2018 were included. We assessed both epilepsy-related and psychosocial variables as well as decision-making of physicians and patients, including reasons for decline in the latter.

RESULTS

Out of 116 patients with a total of 165 VEM, 20 patients were eventually found to be ineligible for resection, 51 declined, and 45 agreed on recommendations for resection or further VEM diagnostics. Patients most frequently declined due to general fear of brain surgery (n = 30, 59%) and currently lower seizure frequency (n = 11, 22%). An independent predictor of patients' decline was less epilepsy-related fear (OR 0.43; p = 0.02) assessed in a standardised questionnaire.

CONCLUSION

Half of the patients potentially eligible for resective surgery decline the operation or further VEM procedures. Patients who decline are more fearful of brain surgery than of ongoing disabling seizures. More insight is needed to improve counselling of patients.

Personalised virtual brain models in epilepsy

Individuals with drug-resistant focal epilepsy are candidates for surgical treatment as a curative option. Before surgery can take place, the patient must have a presurgical evaluation to establish whether and how surgical treatment might stop their seizures without causing neurological deficits. Virtual brains are a new digital modelling technology that map the brain network of a person with epilepsy, using data derived from MRI. This technique produces a computer simulation of seizures and brain imaging signals, such as those that would be recorded with intracranial EEG. When combined with machine learning, virtual brains can be used to estimate the extent and organisation of the epileptogenic zone (ie, the brain regions related to seizure generation and the spatiotemporal dynamics during seizure onset). Virtual brains could, in the future, be used for clinical decision making, to improve precision in localisation of seizure activity, and for surgical planning, but at the moment these models have some limitations, such as low spatial resolution. As evidence accumulates in support of the predictive power of personalised virtual brain models, and as methods are tested in clinical trials, virtual brains might inform clinical practice in the near future.

Epilepsy surgery outcomes in patients with GATOR1 gene complex variants: Report of new cases and review of literature

AIM

To report seizure outcomes in children with GATOR1 gene complex disorders who underwent epilepsy surgery and perform a systematic literature search to study the available evidence.

METHODS

The records of children with pathogenic/likely pathogenic variants in GATOR1 gene complex who underwent epilepsy surgery were reviewed. Clinical, radiological, neurophysiological, and histological data were extracted/summarized. The systematic review included all case series/reports and observational studies reporting on children or adults with genetic (germline or somatic) variants in the GATOR1 complex genes (DEPDC5, NPRL2, NPRL3) with focal epilepsy with/without focal cortical dysplasia who underwent epilepsy surgery; seizure outcomes were analyzed.

RESULTS

Eight children with pathogenic/likely pathogenic variants in GATOR1 complex genes were included. All had drug-resistant epilepsy. Six children had significant neurodevelopmental delay. Epilepsy surgery was performed in all; clinical seizure freedom was noted in 4 children (50%). Systematic literature search identified 17 eligible articles; additional 30 cases with patient-level data were studied. Lesional MRI brain was seen in 80% cases. The pooled rate of seizure freedom following surgery was 60%; FCD IIa was the most encountered pathology.

INTERPRETATION

Epilepsy surgery may be effective in some children with GATOR1 complex gene variants. Seizure outcomes may be compromised by extensive epileptogenic zones.

Epileptic-network-based prediction and control of seizures in humans

Epilepsy is now conceptualized as a network disease. The epileptic brain network comprises structurally and functionally connected cortical and subcortical brain regions - spanning lobes and hemispheres -, whose connections and dynamics evolve in time. With this concept, focal and generalized seizures as well as other related pathophysiological phenomena are thought to emerge from, spread via, and be terminated by network vertices and edges that also generate and sustain normal, physiological brain dynamics. Research over the last years has advanced concepts and techniques to identify and characterize the evolving epileptic brain network and its constituents on various spatial and temporal scales. Network-based approaches further our understanding of how seizures emerge from the evolving epileptic brain network, and they provide both novel insights into pre-seizure dynamics and important clues for success or failure of measures for network-based seizure control and prevention. In this review, we summarize the current state of knowledge and address several important challenges that would need to be addressed to move network-based prediction and control of seizures closer to clinical translation.

Clinical Features, Neuropathology, and Surgical Outcome in Patients With Refractory Epilepsy and Brain Somatic Variants in the SLC35A2 Gene

BACKGROUND AND OBJECTIVES

The SLC35A2 gene, located at chromosome Xp11.23, encodes for a uridine diphosphate-galactose transporter. We describe clinical, genetic, neuroimaging, EEG, and histopathologic findings and assess possible predictors of postoperative seizure and cognitive outcome in 47 patients with refractory epilepsy and brain somatic SLC35A2 gene variants.

METHODS

This is a retrospective multicenter study where we performed a descriptive analysis and classical hypothesis testing. We included the variables of interest significantly associated with the outcomes in the generalized linear models.

RESULTS

Two main phenotypes were associated with brain somatic SLC35A2 variants: (1) early epileptic encephalopathy (EE, 39 patients) with epileptic spasms as the predominant seizure type and moderate to severe intellectual disability and (2) drug-resistant focal epilepsy (DR-FE, 8 patients) associated with normal/borderline cognitive function and specific neuropsychological deficits. Brain MRI was abnormal in all patients with EE and in 50% of those with DR-FE. Histopathology review identified mild malformation of cortical development with oligodendroglial hyperplasia in epilepsy in 44/47 patients and was inconclusive in 3. The 47 patients harbored 42 distinct mosaic SLC35A2 variants, including 14 (33.3%) missense, 13 (30.9%) frameshift, 10 (23.8%) nonsense, 4 (9.5%) in-frame deletions/duplications, and 1 (2.4%) splicing variant. Variant allele frequencies (VAFs) ranged from 1.4% to 52.6% (mean VAF: 17.3 ± 13.5). At last follow-up (35.5 ± 21.5 months), 30 patients (63.8%) were in Engel Class I, of which 26 (55.3%) were in Class IA. Cognitive performances remained unchanged in most patients after surgery. Regression analyses showed that the probability of achieving both Engel Class IA and Class I outcomes, adjusted by age at seizure onset, was lower when the duration of epilepsy increased and higher when postoperative EEG was normal or improved. Lower brain VAF was associated with improved postoperative cognitive outcome in the analysis of associations, but this finding was not confirmed in regression analyses.

DISCUSSION

Brain somatic SLC35A2 gene variants are associated with 2 main clinical phenotypes, EE and DR-FE, and a histopathologic diagnosis of MOGHE. Additional studies will be needed to delineate any possible correlation between specific genetic variants, mutational load in the epileptogenic tissue, and surgical outcomes.

The differential role of magnetic resonance imaging in predicting surgical outcomes between children versus adults with temporal lobe epilepsy

OBJECTIVE

This study aims to investigate the clinical discrepancies and the different predictors of anterior temporal lobectomy (ATL) in children (<18 years at surgery) and adults (>18 years at surgery) with temporal lobe epilepsy (TLE).

MATERIALS AND METHODS

A total of 262 patients (56 children and 206 adults) with TLE who underwent ATL were included in this study. The clinical variables, including patients' characteristics, preoperative evaluations, pathology, surgical prognosis, and surgical predictors were assessed the discrepancies between TLE children versus adults using univariate and multivariate analyses. Kaplan-Meier survival analysis was used to calculate the probability of seizure freedom and AEDs withdrawal after ATL, and the difference between TLE children and adults was analyzed using the Log-Rank test.

RESULTS

There were significant differences including semiology, magnetic resonance imaging (MRI) examinations, numbers of preoperative AEDs, and pathologies between TLE children and adults (P < 0.05, Q < 0.05). The MRI-detected epileptic focus was the only independent predictor of seizure freedom (P = 0.002, Q = 0.036) in TLE children, and the concordance of MRI-detected focus with video-electroencephalography (video-EEG)-detected epileptic zone was the only variable associated with seizure freedom in TLE adults (OR = 2.686, 95% CI = 1.014-7.115, P = 0.047). The TLE children experienced a higher probability of AEDs withdrawal than adults after surgery (P = 0.005).

SIGNIFICANCE

There were remarkable differences in clinical manifestations, MRI examinations, number of preoperative AEDs, and pathologies between TLE children versus adults. TLE children had a higher possibility of AEDs withdrawal than adults after surgery. The favorable seizure outcome of ATL depended on the early complete resection of MRI-detected epileptogenic focus in TLE children, while the concordance of MRI-detected focus with EEG-detected epileptogenic zone was the only predictor of favorable seizure outcomes in TLE adults.

Wearable OPM-MEG: A changing landscape for epilepsy

Magnetoencephalography with optically pumped magnometers (OPM-MEG) is an emerging and novel, cost-effective wearable system that can simultaneously record neuronal activity with high temporal resolution ("when" neuronal activity occurs) and spatial resolution ("where" neuronal activity occurs). This paper will first outline recent methodological advances in OPM-MEG compared to conventional superconducting quantum interference device (SQUID)-MEG before discussing how OPM-MEG can become a valuable and noninvasive clinical support tool in epilepsy surgery evaluation. Although OPM-MEG and SQUID-MEG share similar data features, OPM-MEG is a wearable design that fits children and adults, and it is also robust to head motion within a magnetically shielded room. This means that OPM-MEG can potentially extend the application of MEG into the neurobiology of severe childhood epilepsies with intellectual disabilities (e.g., epileptic encephalopathies) without sedation. It is worth noting that most OPM-MEG sensors are heated, which may become an issue with large OPM sensor arrays (OPM-MEG currently has fewer sensors than SQUID-MEG). Future implementation of triaxial sensors may alleviate the need for large OPM sensor arrays. OPM-MEG designs allowing both awake and sleep recording are essential for potential long-term epilepsy monitoring.

Timing of referral to evaluate for epilepsy surgery: Expert Consensus Recommendations from the Surgical Therapies Commission of the International League Against Epilepsy

Epilepsy surgery is the treatment of choice for patients with drug-resistant seizures. A timely evaluation for surgical candidacy can be life-saving for patients who are identified as appropriate surgical candidates, and may also enhance the care of nonsurgical candidates through improvement in diagnosis, optimization of therapy, and treatment of comorbidities. Yet, referral for surgical evaluations is often delayed while palliative options are pursued, with significant adverse consequences due to increased morbidity and mortality associated with intractable epilepsy. The Surgical Therapies Commission of the International League Against Epilepsy (ILAE) sought to address these clinical gaps and clarify when to initiate a surgical evaluation. We conducted a Delphi consensus process with 61 epileptologists, epilepsy neurosurgeons, neurologists, neuropsychiatrists, and neuropsychologists with a median of 22 years in practice, from 28 countries in all six ILAE world regions. After three rounds of Delphi surveys, evaluating 51 unique scenarios, we reached the following Expert Consensus Recommendations: (1) Referral for a surgical evaluation should be offered to every patient with drug-resistant epilepsy (up to 70 years of age), as soon as drug resistance is ascertained, regardless of epilepsy duration, sex, socioeconomic status, seizure type, epilepsy type (including epileptic encephalopathies), localization, and comorbidities (including severe psychiatric comorbidity like psychogenic nonepileptic seizures [PNES] or substance abuse) if patients are cooperative with management; (2) A surgical referral should be considered for older patients with drug-resistant epilepsy who have no surgical contraindication, and for patients (adults and children) who are seizure-free on 1-2 antiseizure medications (ASMs) but have a brain lesion in noneloquent cortex; and (3) referral for surgery should not be offered to patients with active substance abuse who are noncooperative with management. We present the Delphi consensus results leading up to these Expert Consensus Recommendations and discuss the data supporting our conclusions. High level evidence will be required to permit creation of clinical practice guidelines.

Multimodal combination of neuroimaging methods for localizing the epileptogenic zone in MR-negative epilepsy

The objective was to determine the optimal combination of multimodal imaging methods (IMs) for localizing the epileptogenic zone (EZ) in patients with MR-negative drug-resistant epilepsy. Data from 25 patients with MR-negative focal epilepsy (age 30 ± 10 years, 16M/9F) who underwent surgical resection of the EZ and from 110 healthy controls (age 31 ± 9 years; 56M/54F) were used to evaluate IMs based on 3T MRI, FDG-PET, HD-EEG, and SPECT. Patients with successful outcomes and/or positive histological findings were evaluated. From 38 IMs calculated per patient, 13 methods were selected by evaluating the mutual similarity of the methods and the accuracy of the EZ localization. The best results in postsurgical patients for EZ localization were found for ictal/ interictal SPECT (SISCOM), FDG-PET, arterial spin labeling (ASL), functional regional homogeneity (ReHo), gray matter volume (GMV), cortical thickness, HD electrical source imaging (ESI-HD), amplitude of low-frequency fluctuation (ALFF), diffusion tensor imaging, and kurtosis imaging. Combining IMs provides the method with the most accurate EZ identification in MR-negative epilepsy. The PET, SISCOM, and selected MRI-post-processing techniques are useful for EZ localization for surgical tailoring.

Standardized reporting of complications of epilepsy surgery and invasive monitoring: A single-center retrospective study

OBJECTIVE

Monitoring adverse effects related to epilepsy surgery is essential for quality control and for counseling patients prior to the procedure. The aim of this study was to analyze the rates of complications related to epilepsy surgery following invasive monitoring and to classify them according to the recently proposed protocol by the E-pilepsy consortium.

METHODS

This is a retrospective study of collected data extracted from our routinely updated epilepsy surgery database which consisted of 173 surgical procedures: 89 surgeries for insertion of subdural grids, strips, and/or depth electrodes, and 84 resective surgeries. According to the protocol, complications were defined as unexpected postoperative adverse events and were stratified into transient (lasting less than 6 months) and permanent deficits (lasting 6 months or longer). In addition, we reported patients with postoperative psychiatric disturbances and calculated the rates of transient and permanent postoperative sequelae which were defined as expected postoperative deficits deemed inherent to the surgical procedure.

RESULTS

Six potentially life-threatening complications requiring acceleration of the planned resective surgery occurred during invasive monitoring. Following resective surgery, 12 transient sequelae (8 motor deficits, three language deficits, and one transient dyscalculia) and 10 permanent sequelae (5 mild memory disturbances, four visual field cuts, and one contralateral dysesthesia) occurred. In addition, 7 patients experienced transient motor complications. Four permanent postoperative neurological complications (4.8%) occurred: motor deficits in three patients and a partial peripheral facial palsy in one. Finally, five patients developed de novo psychiatric disturbances (transient in four and permanent in one).

CONCLUSIONS

This is the first study to classify complications of epilepsy surgery according to the E-pilepsy consortium protocol. Our findings demonstrate that epilepsy surgery following invasive monitoring is safe and associated with low morbidity when performed in specialized centers. Monitoring these complications according to a unified definition and using a multidimensional protocol will allow for a direct comparison across epilepsy surgery centers, will provide the epileptologists and surgeons with objective percentages to share with their patients and will help in identifying risk factors and improving the safety of epilepsy surgery.

Transcranial current stimulation in epilepsy: A systematic review of the fundamental and clinical aspects

Purpose

Transcranial electrical current stimulation (tES or tCS, as it is sometimes referred to) has been proposed as non-invasive therapy for pharmacoresistant epilepsy. This technique, which includes direct current (tDCS) and alternating current (tACS) stimulation involves the application of weak currents across the cortex to change cortical excitability. Although clinical trials have demonstrated the therapeutic efficacy of tES, its specific effects on epileptic brain activity are poorly understood. We sought to summarize the clinical and fundamental effects underlying the application of tES in epilepsy.

Methods

A systematic review was performed in accordance with the PRISMA guidelines. A database search was performed in PUBMED, MEDLINE, Web of Science and Cochrane CENTRAL for articles corresponding to the keywords “epilepsy AND (transcranial current stimulation OR transcranial electrical stimulation)”.

Results

A total of 56 studies were included in this review. Through these records, we show that tDCS and tACS epileptic patients are safe and clinically relevant techniques for epilepsy. Recent articles reported changes of functional connectivity in epileptic patients after tDCS. We argue that tDCS may act by affecting brain networks, rather than simply modifying local activity in the targeted area. To explain the mechanisms of tES, various cellular effects have been identified. Among them, reduced cell loss, mossy fiber sprouting, and hippocampal BDNF protein levels. Brain modeling and human studies highlight the influence of individual brain anatomy and physiology on the electric field distribution. Computational models may optimize the stimulation parameters and bring new therapeutic perspectives.

Conclusion

Both tDCS and tACS are promising techniques for epilepsy patients. Although the clinical effects of tDCS have been repeatedly assessed, only one clinical trial has involved a consistent number of epileptic patients and little knowledge is present about the clinical outcome of tACS. To fill this gap, multicenter studies on tES in epileptic patients are needed involving novel methods such as personalized stimulation protocols based on computational modeling. Furthermore, there is a need for more in vivo studies replicating the tES parameters applied in patients. Finally, there is a lack of clinical studies investigating changes in intracranial epileptiform discharges during tES application, which could clarify the nature of tES-related local and network dynamics in epilepsy.

Seizure Outcome of Temporal Lobe Epilepsy Surgery in Adults and Children: A Systematic Review and Meta-Analysis

BACKGROUND

Temporal lobe epilepsy (TLE) surgery is associated with the best seizure outcome in adults, although its long-term results remain suboptimal. Retrospective pediatric studies suggest better figures whose determinants are poorly understood.

OBJECTIVE

To conduct a systematic review and meta-analysis of studies on the efficacy of TLE surgery in children (age younger than 18 years) and adults.

METHODS

We searched MEDLINE, Embase, and Cochrane Library for TLE surgery original research from January 1, 1990, until May 12, 2020. The outcome measures were seizure freedom since surgery and seizure freedom either at last or longest follow-up. We meta-analyzed the proportion of children and adults achieving either Engel I/International League Against Epilepsy (ILAE) 1 or Engel IA/ILAE 1A outcome by follow-up duration, type of surgery, histopathology, neuroimaging, quality of the studies, and publication period. We used a random effects model with Freeman-Tukey double arcsine transformation of proportions.

RESULTS

From 40 409 records identified, we included 277 studies (30 848 patients). The proportions of patients achieving Engel I/ILAE 1 and Engel IA/ILAE 1A outcomes were 0.74 (95% CI, 0.69-0.78) and 0.61 (0.48-0.74) for children and 0.69 (0.67-0.71) and 0.56 (0.52-0.60) for adults. Histopathology significantly influenced Engel I/ILAE 1 outcome in adults but not in children (P < .0001), while the type of surgery significantly influenced Engel I/ILAE 1 outcome in children but not in adults.

CONCLUSION

The proportion of seizure freedom after TLE surgery was higher in children, although not significantly. Histopathology and the surgical approach can influence seizure outcome, with age-related variability.

Stereoelectroencephalography in the preoperative assessment of patients with refractory focal epilepsy: experience at an epilepsy centre

OBJECTIVE

Stereoelectroencephalography (SEEG) is a technique for preoperative evaluation of patients with difficult-to-localise refractory focal epilepsy (DLRFE), enabling the study of deep cortical structures. The procedure, which is increasingly used in international epilepsy centres, has not been fully developed in Spain. We describe our experience with SEEG in the preoperative evaluation of DLRFE.

MATERIAL AND METHODS

In the last 8 years, 71 patients with DLRFE were evaluated with SEEG in our epilepsy centre. We prospectively analysed our results in terms of localisation of the epileptogenic zone (EZ), surgical outcomes, and complications associated with the procedure.

RESULTS

The median age of the sample was 30 years (range, 4-59 years); 27 patients (38%) were women. Forty-five patients (63.4%) showed no abnormalities on brain MR images. A total of 627 electrodes were implanted (median, 9 electrodes per patient; range, 1-17), and 50% of implantations were multilobar. The EZ was identified in 64 patients (90.1%), and was extratemporal or temporal plus in 66% of the cases. Follow-up was over one year in 55 of the 61 patients undergoing surgery: in the last year of follow-up, 58.2% were seizure-free (Engel Epilepsy Surgery Outcome Scale class I) and 76.4% had good outcomes (Engel I-II). Three patients (4.2%) presented brain haemorrhages.

CONCLUSION

SEEG enables localisation of the EZ in patients in whom this was previously impossible, offering better surgical outcomes than other invasive techniques while having a relatively low rate of complications.

Stereoelectroencephalography in the preoperative assessment of patients with refractory focal epilepsy: Experience at an epilepsy centre

OBJECTIVE

Stereoelectroencephalography (SEEG) is a technique for preoperative evaluation of patients with difficult-to-localise refractory focal epilepsy (DLRFE), enabling the study of deep cortical structures. The procedure, which is increasingly used in international epilepsy centres, has not been fully developed in Spain. We describe our experience with SEEG in the preoperative evaluation of DLRFE.

MATERIAL AND METHODS

In the last 8 years, 71 patients with DLRFE were evaluated with SEEG in our epilepsy centre. We prospectively analysed our results in terms of localisation of the epileptogenic zone (EZ), surgical outcomes, and complications associated with the procedure.

RESULTS

The median age of the sample was 30 years (range, 4-59 years); 27 patients (38%) were women. Forty-five patients (63.4%) showed no abnormalities on brain MR images. A total of 627 electrodes were implanted (median, 9 electrodes per patient; range, 1-17), and 50% of implantations were multilobar. The EZ was identified in 64 patients (90.1%), and was extratemporal or temporal plus in 66% of the cases. Follow-up was over one year in 55 of the 61 patients undergoing surgery: in the last year of follow-up, 58.2% were seizure-free (Engel Epilepsy Surgery Outcome Scale class I) and 76.4% had good outcomes (Engel I-II). Three patients (4.2%) presented brain haemorrhages.

CONCLUSION

SEEG enables localisation of the EZ in patients in whom this was previously impossible, offering better surgical outcomes than other invasive techniques while having a relatively low rate of complications.

Virtual Epileptic Patient brain modeling: relationships with seizure onset and surgical outcome

Objective

The virtual epileptic patient (VEP) is a large‐scale brain modeling method based on virtual brain technology, using stereoelectroencephalography (SEEG), anatomical data (magnetic resonance imaging [MRI] and connectivity), and a computational neuronal model to provide computer simulations of a patient's seizures. VEP has potential interest in the presurgical evaluation of drug‐resistant epilepsy by identifying regions most likely to generate seizures. We aimed to assess the performance of the VEP approach in estimating the epileptogenic zone and in predicting surgical outcome.

Methods

VEP modeling was retrospectively applied in a cohort of 53 patients with pharmacoresistant epilepsy and available SEEG, T1‐weighted MRI, and diffusion‐weighted MRI. Precision recall was used to compare the regions identified as epileptogenic by VEP (EZ_VEP) to the epileptogenic zone defined by clinical analysis incorporating the Epileptogenicity Index (EI) method (EZ_C). In 28 operated patients, we compared the VEP results and clinical analysis with surgical outcome.

Results

VEP showed a precision of 64% and a recall of 44% for EZ_VEP detection compared to EZ_C. There was a better concordance of VEP predictions with clinical results, with higher precision (77%) in seizure‐free compared to non‐seizure‐free patients. Although the completeness of resection was significantly correlated with surgical outcome for both EZ_C and EZ_VEP, there was a significantly higher number of regions defined as epileptogenic exclusively by VEP that remained nonresected in non‐seizure‐free patients.

Significance

VEP is the first computational model that estimates the extent and organization of the epileptogenic zone network. It is characterized by good precision in detecting epileptogenic regions as defined by a combination of visual analysis and EI. The potential impact of VEP on improving surgical prognosis remains to be exploited. Analysis of factors limiting the performance of the actual model is crucial for its further development.

Reorganization of Parvalbumin Immunopositive Perisomatic Innervation of Principal Cells in Focal Cortical Dysplasia Type IIB in Human Epileptic Patients

Focal cortical dysplasia (FCD) is one of the most common causes of drug-resistant epilepsy. As several studies have revealed, the abnormal functioning of the perisomatic inhibitory system may play a role in the onset of seizures. Therefore, we wanted to investigate whether changes of perisomatic inhibitory inputs are present in FCD. Thus, the input properties of abnormal giant- and control-like principal cells were examined in FCD type IIB patients. Surgical samples were compared to controls from the same cortical regions with short postmortem intervals. For the study, six subjects were selected/each group. The perisomatic inhibitory terminals were quantified in parvalbumin and neuronal nuclei double immunostained sections using a confocal fluorescent microscope. The perisomatic input of giant neurons was extremely abundant, whereas control-like cells of the same samples had sparse inputs. A comparison of pooled data shows that the number of parvalbumin-immunopositive perisomatic terminals contacting principal cells was significantly larger in epileptic cases. The analysis showed some heterogeneity among epileptic samples. However, five out of six cases had significantly increased perisomatic input. Parameters of the control cells were homogenous. The reorganization of the perisomatic inhibitory system may increase the probability of seizure activity and might be a general mechanism of abnormal network activity.

Surgeon-Led Initiatives to Increase Access to Surgical Treatment of Epilepsy at an Academic Level 4 Epilepsy Center: An Observational Cohort Study

BACKGROUND

Underutilization of surgical treatment for epilepsy is multifactorial, and the multidisciplinary nature of caring for these patients represents a significant hurdle in expanding surgical treatment of epilepsy.

OBJECTIVE

To develop internal and external surgical referral relationships for patients with medically refractory epilepsy with the goal of improving access to care.

METHODS

To expand access to surgical epilepsy treatment at University of California (UC)-Irvine, 4 broad approaches focused on developing referral relationships and process improvement of surgical evaluation were undertaken in 2015 and 2016. The authors performed a retrospective review of all surgical epilepsy case referrals of the senior author from 2014 through 2020.

RESULTS

Epilepsy surgical volume at UC-Irvine increased from an average of 5.2 cases annually to 32 cases in the first year (2015) of implementation. There was continued case volume growth from 2015 through 2020 to 52 procedures in the most recent year (P = .03). Hospital payments for epilepsy procedures increased from $1.09M in 2015 to $2.02M and $1.8M in 2019 and 2020 (P < .01), respectively, while maintaining a diverse payer mix. 79.4% of these patients did not have a previously established option for surgical epilepsy care.

CONCLUSION

We outline strategies that level 4 epilepsy centers may use to strengthen collaborations and improve patient access for surgical epilepsy treatment. Increased collaboration can both improve the number of patients with epilepsy with access to specialized surgical care and produce reimbursement benefits for the centers caring for these patients, regardless of insurance source.

Machine Learning Approaches for Imaging-Based Prognostication of the Outcome of Surgery for Mesial Temporal Lobe Epilepsy

Objectives

Around 30% of patients undergoing surgical resection for drug‐resistant mesial temporal lobe epilepsy (MTLE) do not obtain seizure freedom. Success of anterior temporal lobe resection (ATLR) critically depends on the careful selection of surgical candidates, aiming at optimizing seizure freedom while minimizing postoperative morbidity. Structural MRI and FDG‐PET neuroimaging are routinely used in presurgical assessment and guide the decision to proceed to surgery. In this study, we evaluate the potential of machine learning techniques applied to standard presurgical MRI and PET imaging features to provide enhanced prognostic value relative to current practice.

Methods

Eighty two patients with drug resistant MTLE were scanned with FDG‐PET pre‐surgery and T1‐weighted MRI pre‐ and postsurgery. From these images the following features of interest were derived: volume of temporal lobe (TL) hypometabolism, % of extratemporal hypometabolism, presence of contralateral TL hypometabolism, presence of hippocampal sclerosis, laterality of seizure onset volume of tissue resected and % of temporal lobe hypometabolism resected. These measures were used as predictor variables in logistic regression, support vector machines, random forests and artificial neural networks.

Results

In the study cohort, 24 of 82 (28.3%) who underwent an ATLR for drug‐resistant MTLE did not achieve Engel Class I (i.e., free of disabling seizures) outcome at a minimum of 2 years of postoperative follow‐up. We found that machine learning approaches were able to predict up to 73% of the 24 ATLR surgical patients who did not achieve a Class I outcome, at the expense of incorrect prediction for up to 31% of patients who did achieve a Class I outcome. Overall accuracies ranged from 70% to 80%, with an area under the receiver operating characteristic curve (AUC) of .75–.81. We additionally found that information regarding overall extent of both total and significantly hypometabolic tissue resected was crucial to predictive performance, with AUC dropping to .59–.62 using presurgical information alone. Incorporating the laterality of seizure onset and the choice of machine learning algorithm did not significantly change predictive performance.

Significance

Collectively, these results indicate that "acceptable" to "good" patient‐specific prognostication for drug‐resistant MTLE surgery is feasible with machine learning approaches utilizing commonly collected imaging modalities, but that information on the surgical resection region is critical for optimal prognostication.

Underutilization of advanced presurgical studies and high rates of vagus nerve stimulation for drug-resistant epilepsy: a single-center experience and recommendations

INTRODUCTION

Epilepsy surgery continues to be profoundly underutilized despite its safety and effectiveness. We sought to investigate factors that may contribute to this phenomenon, with a particular focus on the antecedent underutilization of appropriate preoperative studies.

METHODS

We reviewed patient data from a pediatric epilepsy clinic over an 18-month period. Patients with drug-resistant epilepsy (DRE) were categorized according to brain magnetic resonance imaging (MRI) findings (lesional, MRI-negative, or multifocal abnormalities) and type of epilepsy diagnosis based on semiology and electroencephalography (EEG) (focal or generalized). We then analyzed the rates of diagnostic test utilization, surgical referral, and subsequent epilepsy surgery as well as vagus nerve stimulation (VNS).

RESULTS

Of the 249 patients with a diagnosis of epilepsy, 138 (55.4%) were found to have DRE. Excluding the 10 patients with DRE who did not undergo MRI, 76 patients (59.4%) were found to be MRI-negative (non-lesional epilepsy), 37 patients (28.9%) were found to have multifocal abnormalities, and 15 patients (11.7%) were found to have a single epileptogenic lesion on MRI (lesional epilepsy). Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) were each completed in nine patients (7.0%) and magnetoencephalography (MEG) in four patients (3.1%). Despite the low utilization rate of adjunctive studies, over half (56.3%) ultimately underwent VNS alone, and 8.6% ultimately underwent definitive intracranial resection or disconnection surgery.

CONCLUSIONS

The underutilization of appropriate non-invasive, presurgical testing in patients with focal DRE may in part explain the continued underutilization of definitive, resective/disconnective surgery. For patients without access to a high-volume, multidisciplinary surgical epilepsy center, adjunctive presurgical studies [e.g., PET, SPECT, MEG, electrical source imaging (ESI), EEG-functional magnetic resonance imaging (fMRI)], even when available, are rarely ordered, and this may contribute to excessive rates of VNS in lieu of definitive intracranial surgery.

Gratifying Gizmos for Research and Clinical MEG

Experimental designs are of utmost importance in neuroimaging. Experimental repertoire needs to be designed with the understanding of physiology, clinical feasibility, and constraints posed by a particular neuroimaging method. Innovations in introducing natural, ecologically-relevant stimuli, with successful collaboration across disciplines, correct timing, and a bit of luck may cultivate novel experiments, new discoveries, and open pathways to new clinical practices. Here I introduce some gizmos that I have initiated in magnetoencephalography (MEG) and applied with my collaborators in my home laboratory and in several other laboratories. These gizmos have been applied to address neuronal correlates of audiotactile interactions, tactile sense, active and passive movements, speech processing, and intermittent photic stimulation (IPS) in humans. This review also includes additional notes on the ideas behind the gizmos, their evolution, and results obtained.

Early epilepsy surgery for non drug-resistant patients

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Absence of drug-resistance is predictor of better post-surgical outcome.

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Post-surgical outcome in non drug-resistant patients is favourable irrespective of both the localization of surgery and the histological diagnosis.

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Non drug-resistant patients who underwent epilepsy surgery are more likely to successfully discontinue ASMs.

The aim of epilepsy treatment is to achieve seizure freedom. Surgery is often still considered a late option when pharmacological treatments have failed and epilepsy has become drug-resistant.

We analyse the clinical features and surgical outcome in patients who underwent surgery without experiencing drug-resistance comparing with those observed in patients who became drug-resistant.

Two-hundred and fifty patients with symptomatic focal epilepsy (12.1% of patients who underwent surgery at the “Claudio Munari” Epilepsy Surgery Center) were selected on the basis of initial period of seizure freedom and followed-up for at least 12 months. Patients were divided into two groups: those who underwent surgery during the initial period of seizure freedom (n = 74), and those who underwent surgery after an initial seizure-free period followed by drug-resistance (n = 176).

Outcomes were significantly better in non-drug-resistant patients (p < 0.001), all of whom had Engel class Ia or Ic. In the drug-resistant group, 136 patients (77.3%) had class Ia or Ic. The median post-operative follow-up was respectively 75.0 and 84.0 months.

Epilepsy surgery is a successful treatment, especially for non-drug-resistant patients with focal epilepsy with structural etiology. The timing of surgery affects the outcomes, and “early” surgery should be preferred to prevent likely drug-resistance and to improve prognosis.

Characteristics, surgical outcomes, and influential factors of epilepsy in Sturge-Weber syndrome

Few studies have reported the clinical presentation, surgical treatment, outcomes, and influential factors for patients with epilepsy and Sturge-Weber syndrome.

This large-scale retrospective study continuously enrolled 132 patients with Sturge-Weber syndrome and epilepsy from January 2008 to December 2018 at our hospital to analyze their characteristics. Among these patients, 90 underwent epilepsy surgery, and their postoperative 2-year follow-up seizure, cognitive, and motor functional outcomes were assessed and analyzed. Univariable and multivariable logistic analyses were conducted to explore the influential factors.

Among the Sturge-Weber syndrome patients for whom characteristics were analyzed (n = 132), 76.52% of patients had their first epileptic seizures within their first year of life. The risk factors for cognitive decline were seizure history≥2 years (adjusted odds ratio [aOR] = 3.829, 95% confidence interval [CI]: 1.810-9.021, p = 0.008), bilateral leptomeningeal angiomas (aOR = 3.173, 95% CI: 1.970-48.194, p = 0.013), age at onset &lt; 1 year (aOR = 2.903, 95% CI: 1.230-6.514, p = 0.013), brain calcification (aOR = 2.375, 95% CI: 1.396-5.201, p = 0.021) and left leptomeningeal angiomas (aOR = 2.228, 95% CI: 1.351-32.571, p = 0.030). Of the patients who underwent epilepsy surgery (n = 90), 44 were subject to focal resection, and 46 underwent hemisphere surgery (19 anatomical hemispherectomies and 27 modified hemispherotomies). A postoperative seizure-free status, favorable cognitive outcomes, and favorable motor outcomes were achieved in 83.33%, 44.44%, and 43.33% of surgical patients, respectively. The modified hemispherotomy group had similar surgical outcomes, less intraoperative blood loss and shorter postoperative hospital stays than the anatomical hemispherectomy group. Regarding seizure outcomes, full resection (aOR = 11.115, 95% CI: 1.260-98.067, p = 0.020) and age at surgery &lt; 2 years (aOR = 6.040, 95% CI: 1.444-73.367, p = 0.031) were positive influential factors for focal resection. Age at surgery &lt; 2 years (aOR = 15.053, 95% CI: 1.050-215.899, p = 0.036) and infrequent seizures (aOR = 8.426, 95% CI: 1.086-87.442, p = 0.042; monthly vs. weekly) were positive influential factors for hemisphere surgery.

In conclusion, epilepsy surgery resulted in a good postoperative seizure-free rate and favorable cognitive and motor functional outcomes and showed acceptable safety for patients with epilepsy and Sturge-Weber syndrome. Modified hemispherotomy is a less invasive and safer type of hemisphere surgery than traditional anatomic hemispherectomy with similar surgical outcomes. Early surgery may be helpful to achieve better seizure outcomes and cognitive protection, while the risk of surgery for young children should also be considered.

Surgical evaluation in children <3 years of age with drug-resistant epilepsy: Patient characteristics, diagnostic utilization, and potential for treatment delays

OBJECTIVE

Drug-resistant epilepsy (DRE) occurs at higher rates in children <3 years old. Epilepsy surgery is effective, but rarely utilized in young children despite developmental benefits of early seizure freedom. The present study aims to identify unique patient characteristics and evaluation strategies in children <3 years old who undergo epilepsy surgery evaluation as a means to assess contributors and potential solutions to health care disparities in this group.

METHODS

The Pediatric Epilepsy Research Consortium Epilepsy Surgery Database, a multicentered, cross-sectional collaboration of 21 US pediatric epilepsy centers, collects prospective data on children <18 years of age referred for epilepsy surgery evaluation. We compared patient characteristics, diagnostic utilization, and surgical treatment between children <3 years old and those older undergoing initial presurgical evaluation. We evaluated patient characteristics leading to delayed referral (>1 year) after DRE diagnosis in the very young.

RESULTS

The cohort included 437 children, of whom 71 (16%) were <3 years of age at referral. Children evaluated before the age of 3 years more commonly had abnormal neurological examinations (p = .002) and daily seizures (p = .001). At least one ancillary test was used in 44% of evaluations. Fifty-nine percent were seizure-free following surgery (n = 34), with 35% undergoing limited focal resections. Children with delayed referrals more often had focal aware (p < .001) seizures and recommendation for palliative surgeries (p < .001).

SIGNIFICANCE

There are relatively few studies of epilepsy surgery in the very young. Surgery is effective, but may be disproportionally offered to those with severe presentations. Relatively low utilization of ancillary testing may contribute to reduced surgical therapy for those without evident lesions on magnetic resonance imaging. Despite this, a sizeable portion of patients have favorable outcome after focal epilepsy surgery resections.

Markov modelling of treatment response in a 30-year cohort study of newly diagnosed epilepsy

People with epilepsy have variable and dynamic trajectories in response to antiseizure medications. Accurately modelling long-term treatment response will aid prognostication at the individual level and health resource planning at the societal level. Unfortunately, a robust model is lacking. We aimed to develop a Markov model to predict the probability of future seizure-freedom based on current seizure state and number of antiseizure medication regimens trialled. We included 1,795 people with newly diagnosed epilepsy who attended a specialist clinic in Glasgow, Scotland, between July 1982 and October 2012. They were followed up until October 2014 or death. We developed a simple Markov model, based on current seizure state only, and a more detailed model, based on both current seizure state and number of antiseizure medication regimens trialled. Sensitivity analyses were performed for the regimen-based states model to examine the effect of regimen changes due to adverse effects. The model was externally validated in a separate cohort of 455 newly diagnosis epilepsy patients seen in Perth, Australia, between May 1999 and May 2016. Our models suggested that once seizure-freedom was achieved, it was likely to persist, regardless of the number of antiseizure medications trialled to reach that point. The likelihood of achieving long-term seizure-freedom was highest with the first antiseizure medication regimen, at approximately 50%. The chance of achieving seizure-freedom fell with subsequent regimens. Fluctuations between seizure-free and not seizure-free states were highest earlier on, but decreased with chronicity of epilepsy. Seizure-freedom/recurrence risk tables were constructed with these probability data, similar to cardiovascular risk tables. Sensitivity analyses showed that the general trends and conclusions from the base model were maintained despite perturbing the model and input data with regimen changes due to adverse effects. Quantitative comparison with the external validation cohort showed excellent consistency at year 1, good at year 3 and moderate at year 5. Quantitative models, as used in this study, can provide pertinent clinical insights that are not apparent from simple statistical analysis alone. Attaining seizure freedom at any time in a patient's epilepsy journey will confer durable benefit. Seizure-freedom risk tables may be used to individualise the prediction of future seizure control trajectory.

Temporal lobe epilepsy: A never-ending story

INTRODUCTION

Semiology and anatomo-electroclinical correlations remain invaluable for maintaining the level of excellence in temporal lobe epilepsy (TLE) surgery, in parallel to the constantly evolving technical progress. The aim of this study was to address semiological frequent and not so frequent signs, rarities and red flags in a long follow-up surgical series of patients suffering from TLE.

METHODS

Patients operated within the boundaries of the TL at our center, with presurgical video-EEG recorded seizures and seizure free after a postoperative follow-up of at least 24 months were included. Ictal semiology was systematically described and new red flags were explored by comparing with a second group of patients with the same inclusion criteria but whose outcome had been unfavorable (Engel II-IV).

RESULTS

Sixty-two patients were included, 46 seizure free and 16 with outcome Engel II-IV. Most seizure-free patients had a classical semiological presentation including aura (69.6%, abdominal the most frequent), followed by loss of responsiveness (90.2%) oral automatisms (90.7%), ipsilateral gestural automatisms (53.5%), contralateral upper limb dystonia (37.5%) or immobility (39.1%), and early ipsilateral non-versive head orientation (33.3%). More infrequent presentations were also present in the group of seizure-free patients: ictal language disturbance (13%), maintenance of responsiveness during seizures (9.8%), and contralateral rhythmic non manipulative automatism (6.9%). The presence of an isolated viscerosensory and/or psychic aura was significantly more frequent in the seizure-free group (p = 0.017), as well as oroalimentary automatisms (p = 0.005). Two signs were only present in the group with outcome Engel II-IV, constituting possible red flags (0.06 < p < 0.07): inferior limbs stepping-like automatisms and postictal dysarthria.

CONCLUSION

An adequate clinical exam during seizures and a careful analysis of video recordings allow to recognize infrequent but well-characterized ictal signs that are part of the range of semiology in TLE, together with the most frequent and classical ictal presentations. Special attention to the localization hypothesis must be paid in the absence of oroalimentary automatisms or when the signs classified as possible red flags emerge.

Outcome of epilepsy surgery in lesional epilepsy: Experiences from a developing country

BACKGROUND

Our aim was to report the postoperative seizure outcome and associated factors in patients with lesional epilepsy, in a low-income setting.

METHODS

This longitudinal prospective study included patients who underwent epilepsy surgery at Kashani Comprehensive Epilepsy Center between 2014 and 2019. Post-surgical outcomes were reported according to the Engel score, and patients were classified into two groups of seizure free (SF) and not-seizure free (NSF).

RESULTS

A total of 148 adult patients, with a mean age of 30.45 ± 9.23 years were included. The SF outcome was reported in 86.5% of patients and antiepileptic drugs (AEDs) were reduced or discontinued in 45.9%. The mean follow-up duration was 26.7 ± 14.9 months. Temporal lobe lesions (76.3%) and mesial temporal sclerosis (MTS) (56.7%) were the most frequent etiologies. Temporal lesion (Incidence relative risk (IRR): 1.76, 95% CI [1.08-2.87], p = 0.023), prior history of CNS infection (IRR:1.18, 95% CI [1.03-1.35], p = 0.019), use of intra-operative ECoG (IRR:1.73, 95% CI [1.06-2.81], p = 0.028), and absence of IEDs in postoperative EEG (IRR: 1.41, 95% CI [1.18-1.70], p < 0.001) were positive predictors for a favorable outcome.

CONCLUSION

Many patients with drug-resistant lesional epilepsy showed a favorable response to surgery. We believe that resective epilepsy surgery in low-income settings is a major treatment option. The high frequency of patients with drug-resistant epilepsy in developing countries is associated with high rates of morbidity and mortality. Hence, strategies to increase access to epilepsy surgery in these settings are urgently needed.

The epileptogenic zone in children with tuberous sclerosis complex is characterized by prominent features of focal cortical dysplasia

OBJECTIVE

Patients with tuberous sclerosis complex (TSC) present with drug-resistant epilepsy in about 60% of cases, and evaluation for epilepsy surgery may be warranted. Correct delineation of the epileptogenic zone (EZ) among multiple dysplastic lesions on MRI represents a challenging step in pre-surgical evaluation.

METHODS

Two experienced neuroradiologists evaluated pre- and post-surgical MRIs of 28 epilepsy surgery patients with TSC, assessing characteristics of tubers, cysts, calcifications, and focal cortical dysplasia (FCD)-resembling lesions. Utilizing multiple metrics, we compared MRI features of the EZ-defined as the resected area in TSC patients who achieved seizure-freedom 2 years after epilepsy surgery-with features of other brain areas. Using combinatorial analysis, we identified combinations of dysplastic features that are most frequently observed in the epileptogenic zone in TSC patients.

RESULTS

All TSC-associated dysplastic features were more frequently observed in the EZ than in other brain areas (increased cortical thickness, gray-white matter blurring, transmantle sign, calcifications, and tubers; Kendal's tau 0.35, 0.25, 0.27, 0.26, and 0.23, respectively; P value <.001 in all). No single feature could reliably and independently indicate the EZ in all patients. Conversely, the EZ was indicated by the presence of the combination of three of the following features: tubers, transmantle sign, increased cortical thickness, calcifications, and the largest FCD-affected area. Out of these, the largest FCD-affected area emerged as the most reliable indicator of the EZ, combined either with calcifications or tubers.

SIGNIFICANCE

The epileptogenic zone in TSC patients harbors multiple dysplastic features, consistent with focal cortical dysplasia. A specific combination of these features can indicate the EZ and aid in pre-surgical MRI evaluation in epilepsy surgery candidates with TSC.

Transcutaneous vagus nerve stimulation in the treatment of drug-resistant epilepsy

Epilepsy is a common chronic neurological disease with a high burden of illness. Invasive vagus nerve stimulation (iVNS) is a well-established treatment option in patients with epilepsy (PWE). More recently, transcutaneous vagus nerve stimulation (tVNS) was introduced, an alternative option which is particularly interesting because it does not require surgery and is instantaneously removable. Here, we thoroughly reviewed clinical data on efficacy and safety of tVNS in epilepsies. Five prospective trials in 118 patients with drug-resistant epilepsies and 3 randomized controlled trials in 280 patients with drug-resistant epilepsies were carried out. Study protocols were heterogeneous in terms of patients' characteristics, used device, stimulation parameters, study duration and endpoints. Seizure reduction amounted up to 64%, with responder rates (seizure reduction ≥50%) up to 65%. Seizure freedom was reached in up to 24%, and even to 31% in a small pediatric study group. Seizure severity scores were provided in 4 studies, showing significant improvement in two of them. Adverse side effects were mostly headache, ear pain and skin alteration and rated as mild to moderate. Drowsiness might be depend on stimulation intensity. Quality of life scores reflecting burden of illness showed significant improvement in two studies. Efficacy and safety of tVNS in PWE has to be interpreted as promising. Multicenter randomized double-blind clinical trials with standardized stimulation protocols and long-term follow-up studies are necessary to finally assess tVNS treatment outcome in drug-resistant epilepsies.