Frameless Stereotaxy in Stereoelectroencephalography Using Intraoperative Computed Tomography

Background: Pharmacoresistant epilepsy affects approximately one-third of all epilepsy patients, and resective surgery may offer favorable outcomes for carefully selected patients with focal epilepsy. The accurate identification of the epileptogenic zone (EZ) is essential for successful surgery, particularly in cases where non-invasive diagnostics are inconclusive. Invasive diagnostics with stereoelectroencephalography (SEEG) offer a reliable approach to localizing the EZ, especially in MRI-negative cases. Methods: This retrospective study analyzed the data of 22 patients with pharmacoresistant epilepsy who underwent frameless stereotactic SEEG electrode implantation with automated CT-based registration between September 2016 and November 2024. For measuring accuracy, Euclidean distance, radial deviation, angular deviation, and depth deviation were calculated for each electrode. Results: A total of 153 depth electrodes were implanted, targeting various cortical regions. The median Euclidean distance at the entry point was 1.54 mm (IQR 1.31), with a radial deviation of 1.33 mm (IQR 1.32). At the target level, the median Euclidean distance was 2.61 mm (IQR 1.53), with a radial deviation of 1.67 mm (IQR 1.54) and depth deviation of 0.95 mm (IQR 2.43). Accuracy was not significantly affected by electrode order, anatomical location, skull thickness, or intracranial length. Conclusions: These findings demonstrate that frameless stereotactic SEEG electrode implantation is safe and feasible for identifying the EZ. The integration of automatic intraoperative CT-based registration ensures precision. While maintaining workflow efficiency, it achieves accuracy comparable to frame-based methods. Further studies with larger cohorts are warranted to validate these results and assess their impact on surgical outcomes.

Augmented Reality in Extratemporal Lobe Epilepsy Surgery

Background: Epilepsy surgery for extratemporal lobe epilepsy (ETLE) is challenging, particularly when MRI findings are non-lesional and seizure patterns are complex. Invasive diagnostic techniques are crucial for accurately identifying the epileptogenic zone and its relationship with surrounding functional tissue. Microscope-based augmented reality (AR) support, combined with navigation, may enhance intraoperative orientation, particularly in cases involving subtle or indistinct lesions, thereby improving patient outcomes and safety (e.g., seizure freedom and preservation of neuronal integrity). Therefore, this study was conducted to prove the clinical advantages of microscope-based AR support in ETLE surgery. Methods: We retrospectively analyzed data from ten patients with pharmacoresistant ETLE who underwent invasive diagnostics with depth and/or subdural grid electrodes, followed by resective surgery. AR support was provided via the head-up displays of the operative microscope, with navigation based on automatic intraoperative computed tomography (iCT)-based registration. The surgical plan included the suspected epileptogenic lesion, electrode positions, and relevant surrounding functional structures, all of which were visualized intraoperatively. Results: Six patients reported complete seizure freedom following surgery (ILAE 1), one patient was seizure-free at the 2-year follow-up, and one patient experienced only auras (ILAE 2). Two patients developed transient neurological deficits that resolved shortly after surgery. Conclusions: Microscope-based AR support enhanced intraoperative orientation in all cases, contributing to improved patient outcomes and safety. It was highly valued by experienced surgeons and as a training tool for less experienced practitioners.

Epileptogenic networks in extra temporal lobe epilepsy

Extra temporal lobe epilepsy (eTLE) may involve heterogenous widespread cerebral networks. We investigated the structural network of an eTLE cohort, at the postulated epileptogenic zone later surgically removed, as a network node: the resection zone (RZ). We hypothesized patients with an abnormal connection to/from the RZ to have proportionally increased abnormalities based on topological proximity to the RZ, in addition to poorer post-operative seizure outcome. Structural and diffusion MRI were collected for 22 eTLE patients pre- and post-surgery, and for 29 healthy controls. The structural connectivity of the RZ prior to surgery, measured via generalized fractional anisotropy (gFA), was compared with healthy controls. Abnormal connections were identified as those with substantially reduced gFA (z < -1.96). For patients with one or more abnormal connections to/from the RZ, connections with closer topological distance to the RZ had higher proportion of abnormalities. The minority of the seizure-free patients (3/11) had one or more abnormal connections, while most non-seizure-free patients (8/11) had abnormal connections to the RZ. Our data suggest that eTLE patients with one or more abnormal structural connections to/from the RZ had more proportional abnormal connections based on topological distance to the RZ and associated with reduced chance of seizure freedom post-surgery.

Who are the Better Candidates for Epilepsy Surgery?

The resective epilepsy surgery can be the effective procedure to get seizure-free outcome in these drug resistant epilepsy (DRE) patients. Class I evidence firmly establishes the superiority of epilepsy surgery over medical treatments in both seizure control and quality of life for DRE patients. For the effective identification of optimal surgical candidates, it's essential to understand the prognostic factors of epilepsy surgery based on the surgical methods employed. Established positive prognostic indicators for temporal resection include the presence of hippocampal sclerosis on magnetic resonance imaging (MRI), focal lesions on MRI, unilateral temporal spikes, concordant ictal electroencephalography (EEG), and a history of prolonged febrile convulsion. Potential negative predictors encompass preoperative secondary generalized tonic-clonic seizures, a normal MRI, postoperative EEG spikes, and age at the time of surgery. For neocortical epilepsy, the prognostic factors identified through multivariate analysis were the presence of a discrete lesion, localized hypometabolism on Fluorodeoxyglucose positron emission tomography (FDG-PET), and localized ictal EEG. A significant correlation was found between achieving a seizure-free outcome in no visible lesion on MRI (MR-negative) epilepsy patients and having concordance in two or more presurgical evaluations, specifically in interictal EEG, ictal EEG, FDG-PET, and ictal single-photon emission computed tomography. There was a marked improvement in the seizure-free outcome in MR-negative temporal lobe epilepsy (TLE) by the application of this strategy. The better surgical candidates for epilepsy surgery are the followings: patients displaying a discrete lesion on MRI with concordant video-EEG monitoring (VEM) results, patients diagnosed with unilateral hippocampal sclerosis who have concordant VEM results, patients with unilateral hippocampal sclerosis but discordant VEM results, patients with focal cortical dysplasia and concordant VEM results, and patients diagnosed with MR-negative TLE who exhibit two or more consistent results from presurgical evaluations.

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.

Diagnostic Accuracy of Epilepsy-dedicated MRI with Post-processing

PURPOSE

To evaluate the diagnostic accuracy of epilepsy-dedicated 3 Tesla MRI including post-processing by correlating MRI, histopathology, and postsurgical seizure outcomes.

METHODS

3 Tesla-MRI including a magnetization-prepared two rapid acquisition gradient echo (MP2RAGE) sequence for post-processing using the morphometric analysis program MAP was acquired in 116 consecutive patients with drug-resistant focal epilepsy undergoing resection surgery. The MRI, histopathology reports and postsurgical seizure outcomes were recorded from the patient's charts.

RESULTS

The MRI and histopathology were concordant in 101 and discordant in 15 patients, 3 no hippocampal sclerosis/gliosis only lesions were missed on MRI and 1 of 28 focal cortical dysplasia (FCD) type II associated with a glial scar was considered a glial scar only on MRI. In another five patients, MRI was suggestive of FCD, the histopathology was uneventful but patients were seizure-free following surgery. The MRI and histopathology were concordant in 20 of 21 glioneuronal tumors, 6 cavernomas, and 7 glial scars. Histopathology was negative in 10 patients with temporal lobe epilepsy, 4 of them had anteroinferior meningoencephaloceles. Engel class IA outcome was reached in 71% of patients.

CONCLUSION

The proposed MRI protocol is highly accurate. No hippocampal sclerosis/gliosis only lesions are typically MRI negative. Small MRI positive FCD can be histopathologically missed, most likely due to sampling errors resulting from insufficient harvesting of tissue.

Does Stereoelectroencephalography Add Value in Patients with Lesional Epilepsy?

OBJECTIVE

Stereoelectroencephalography (SEEG) has gained popularity as an invasive monitoring modality for epileptogenic zone (EZ) localization. The need and indications for SEEG in patients with evident brain lesions or associated abnormalities on imaging is debated. We report our experience with SEEG as a presurgical evaluation tool for patients with lesional epilepsy.

METHODS

A retrospective cohort study was performed of 131 patients with lesional or magnetic resonance imaging abnormality-associated medically refractory focal epilepsy who underwent resections from 2010 to 2017. Seventy-one patients had SEEG followed by resection, and 60 had no invasive recordings. Volumetric analysis of resection cavities from 3T magnetic resonance imaging was performed.

RESULTS

Mean lesion and resection volumes for SEEG and non-SEEG were 16.2 (standard deviation [SD] = 29) versus 23.7 cm3 (SD = 38.4) and 28.1 (SD = 23.2) versus 43.6 cm3 (SD = 43.5), respectively (P = 0.009). Comparing patients with seizure recurrence and patients who remained seizure free, significantly associated variables with seizure recurrence included mean number of failed antiseizure medications (6.86 [SD = 0.32] vs. 5.75 [SD = 0.32]; P = 0.01) and in SEEG patients the mean number of electrodes implanted (8.1 [SD = 0.8] vs. 5.0 [SD = 0.8]; P = 0.005). After multivariate analysis, only failed numbers of medication remained significantly associated with seizure recurrence.

CONCLUSIONS

Seizure outcomes did not correlate with final resection volume after SEEG evaluation. SEEG evaluation presurgically can be used to maintain the efficacy of resection and decrease the volume and subsequent risk of extensive tissue removal. We believe that this technology allows resective surgery to proceed in a subpopulation of patients with lesional epilepsy who may otherwise not have been considered surgical candidates.

Screening of Risk Factors for Poor Prognosis in Patients with Refractory Epilepsy Secondary to Encephalomalacia

Objective

The study was aimed at screening the independent prognostic risk factors for refractory epilepsy associated with encephalomalacia (REAE).

Methods

Patients with REAE treated in the First People's Hospital of Linping District from January 2018 to December 2019 were selected. The prognosis was represented by Engel grading. Clinical data of the patients were collected, including age, sex, BMI, lesion sites, number of lesion sites, lesion size, seizure frequency, epilepsy type, and treatment methods. Independent risk factors for poor prognosis were screened by logistic regression analysis. The receiver operating characteristic curve (ROC) was used to evaluate the prognostic efficacy of independent risk factors.

Results

A total of 48 patients were included in this study, including 31 patients (64.58%) in the good prognosis group and 17 patients (35.42%) in the poor prognosis group. The mean age of the poor prognosis group was higher than that of the good prognosis group (P = 0.002). The proportion of patients with multisite lesions in the poor prognosis group was higher than that in the good prognosis group (P = 0.016). The proportion of patients with cerebral malacia lesion diameter ≥ 3 cm in the poor prognosis group was higher than that in the good prognosis group (P = 0.002). The proportion of patients with attack frequency ≥ 2 times/month in the poor prognosis group was higher than in the good prognosis group (P = 0.002). The proportion of patients receiving surgical treatment in the poor prognosis group was lower than that in the good prognosis group (P < 0.001). Age, number of lesion sites, size of encephalomalacia, and seizure frequency were independent risk factors for the prognosis of patients with REAE (OR > 1, P < 0.05). Surgical treatment was an independent protective factor associated with the prognosis of patients with REAE (OR < 1, P < 0.05). The area under the ROC curve of surgical treatment was 0.83 (P = 0.004). The area under the ROC curve of the size of encephalomalacia was 0.72 (P = 0.008). There was a positive correlation between age and size of encephalomalacia and Engel grade (r > 0, P < 0.05). Surgical treatment was negatively correlated with Engel grade (r < 0, P < 0.05). The number of lesion sites and seizure frequency had no significant correlation with Engel (P > 0.05). The proportion of Engel I patients treated with surgery was higher than that treated with drugs (P = 0.001). The ratio of Engel III and IV patients treated with surgery was lower than that treated with medications (P < 0.05).

Conclusion

Age, number of lesion sites, size of encephalomalacia, and seizure frequency are independent risk factors for the prognosis of patients with REAE. Surgical treatment is an independent prognostic factor for patients with REAE. Surgical treatment can significantly improve patient outcomes.

Epilepsy Surgery in Extratemporal vs Temporal Lobe Epilepsy: Changes in Surgical Volumes and Seizure Outcome Between 1990 and 2017

Objective:

Seizure outcome after extratemporal lobe epilepsy (exTLE) surgery has often been poorer than after temporal lobe epilepsy (TLE) surgery, but recent improvements in diagnostics and surgery may have changed this. Our aim was to analyze the changes in presurgical and surgical volumes and seizure outcome two years after surgery for patients with exTLE compared to those with TLE.

Methods:

We performed a retrospective, single-center cohort study including patients from the Bethel presurgical-surgical-postsurgical database from 1990 to 2017. We used logistic regression to analyze factors influencing the odds for surgery and the odds for seizure freedom after surgery.

Results:

We included 3822 patients with presurgical evaluation, 2404 of whom had subsequently undergone surgery. The proportion of exTLE patients in presurgical evaluation increased from 41% between 1990-1993 to 64% in 2014-2017. The odds for surgery decreased over time (2003-2011: OR=0.50 [95%CI 0.36-0.70]; 2012-2017: OR=0.24 [CI 0.17-0.35]; reference: 1990-2002), and patients with exTLE had lower odds for surgery than TLE patients, but this difference diminished over time (exTLE vs. TLE 1990-2002: OR=0.14 [CI 0.09-0.20]; 2003-2011: OR=0.32 [CI 0.24-0.44]; 2012-2017: OR=0.46 [CI 0.34-0.63]). Etiology, the side of the epileptogenic lesion and invasive recordings additionally influenced the odds for surgery. The most frequent reasons for not undergoing surgery were the missing identification of a circumscribed epileptogenic zone or an unacceptable risk of postsurgical deficits in exTLE patients and the patient’s decision in TLE patients. Compared to TLE patients, the odds for seizure freedom after surgery started lower for patients with exTLE in earlier years, but increased (≤2 lobes 1990-2002: OR=0.47 [CI 0.33-0.68]; 2003-2011: OR=0.62 [CI 0.44-0.87]; 2012-2017: OR=0.78 [CI 0.53-1.15]; ≥3 lobes 1990-2002: OR=0.37 [CI 0.22-0.62]; 2003-2011: OR=0.73 [CI 0.43-1.23]; 2012-2017: OR=1.46 [CI 0.91-2.42]). Etiology, age at surgery and invasive recordings were further predictors for the odds for seizure freedom.

Conclusion:

Over the past 28 years, the success of resective surgery for patients with exTLE has improved. At the same time, the number of exTLE patients being evaluated for surgery increased as well as their odds for undergoing surgery.

MRI of focal cortical dysplasia

Focal cortical dysplasia (FCD) are histopathologically categorized in ILAE type I to III. Mild malformations of cortical development (mMCD) including those with oligodendroglial hyperplasia (MOGHE) are to be integrated into this classification yet. Only FCD type II have distinctive MRI and molecular genetics alterations so far. Subtle FCD including FCD type II located in the depth of a sulcus are often overlooked requiring the use of dedicated sequences (MP2RAGE, FLAWS, EDGE) and/or voxel (VBM)- or surface-based (SBM) postprocessing. The added value of 7 Tesla MRI has to be proven yet.

Multimodal connectome biomarkers of cognitive and affective dysfunction in the common epilepsies

Epilepsy is one of the most common chronic neurological conditions, traditionally defined as a disorder of recurrent seizures. Cognitive and affective dysfunction are increasingly recognized as core disease dimensions and can affect patient well-being, sometimes more than the seizures themselves. Connectome-based approaches hold immense promise for revealing mechanisms that contribute to dysfunction and to identify biomarkers. Our review discusses emerging multimodal neuroimaging and connectomics studies that highlight network substrates of cognitive/affective dysfunction in the common epilepsies. We first discuss work in drug-resistant epilepsy syndromes, that is, temporal lobe epilepsy, related to mesiotemporal sclerosis (TLE), and extratemporal epilepsy (ETE), related to malformations of cortical development. While these are traditionally conceptualized as ‘focal’ epilepsies, many patients present with broad structural and functional anomalies. Moreover, the extent of distributed changes contributes to difficulties in multiple cognitive domains as well as affective-behavioral challenges. We also review work in idiopathic generalized epilepsy (IGE), a subset of generalized epilepsy syndromes that involve subcortico-cortical circuits. Overall, neuroimaging and network neuroscience studies point to both shared and syndrome-specific connectome signatures of dysfunction across TLE, ETE, and IGE. Lastly, we point to current gaps in the literature and formulate recommendations for future research.

Epilepsy is increasingly recognized as a network disorder characterized by recurrent seizures as well as broad-ranging cognitive difficulties and affective dysfunction. Our manuscript reviews recent literature highlighting brain network substrates of cognitive and affective dysfunction in common epilepsy syndromes, namely temporal lobe epilepsy secondary to mesiotemporal sclerosis, extratemporal epilepsy secondary to malformations of cortical development, and idiopathic generalized epilepsy syndromes arising from subcortico-cortical pathophysiology. We discuss prior work that has indicated both shared and distinct brain network signatures of cognitive and affective dysfunction across the epilepsy spectrum, improves our knowledge of structure-function links and interindividual heterogeneity, and ultimately aids screening and monitoring of therapeutic strategies.

On disturbance rejection control of the epileptiform spikes

Epilepsy is a neurological disorder resulting from a sudden development of synchronous firing in a massive group of neurons. For the particularity of the epilepsy, a neural mass model (NMM) is commonly utilized to understand and simulate the mechanism and evolution of the epilepsy. In this paper, based on a multi-coupling NMM and real EEGs of an epileptic mouse, a computational epileptic model is established to simulate the abnormal discharges of a mouse during seizures. Thus, rather than make animal experiments directly, numerical tests can be performed first. It reduces risks and helps improve the closed-loop neuromodulation. In addition, considering that no epileptic model can be utilized for neuromodulation in clinic, and even if a model exists, it still cannot describe the dynamics of the epilepsy faithfully, a scalable observer bandwidth and phase leading active disturbance rejection control (SOB-PLADRC) is proposed. Accordingly, a timelier and more accurate total disturbance estimation can be obtained by a scalable observer bandwidth and phase leading extended state observer, and an expected closed-loop neuromodulation can be realized without an accurate epileptic model. Numerical simulations based on the established model also show that the SOB-PLADRC suppresses seizures best among the PI and other active disturbance rejection approaches. More powerful disturbance rejection ability and more satisfactory closed-loop neuromodulation make the SOB-PLADRC more promising in the seizure control.

Imaging of Neuromodulation and Surgical Interventions for Epilepsy

About one-third of epilepsy cases are refractory to medical therapy. During the past decades, the availability of surgical epilepsy interventions has substantially increased as therapeutic options for this group of patients. A wide range of surgical interventions and electrophysiologic neuromodulation techniques are available, including lesional resection, lobar resection, thermoablation, disconnection, multiple subpial transections, vagus nerve stimulation, responsive neurostimulation, and deep brain stimulation. The indications and imaging features of potential complications of the newer surgical interventions may not be widely appreciated, particularly if practitioners are not associated with comprehensive epilepsy centers. In this article, we review a wide range of invasive epilepsy treatment modalities with a particular focus on their postoperative imaging findings and complications. A state-of-the-art treatment algorithm provides context for imaging findings by helping the reader understand how a particular invasive treatment decision is made.

Neuroimaging and genetic characteristics of malformation of cortical development due to mTOR pathway dysregulation: clues for the epileptogenic lesions and indications for epilepsy surgery

Introduction: Malformation of cortical development (MCD) is strongly associated with drug-resistant epilepsies for which surgery to remove epileptogenic lesions is common. Two notable technological advances in this field are identification of the underlying genetic cause and techniques in neuroimaging. These now question how presurgical evaluation ought to be approached for 'mTORpathies.'Area covered: From review of published primary and secondary articles, the authors summarize evidence to consider focal cortical dysplasia (FCD), tuber sclerosis complex (TSC), and hemimegalencephaly (HME) collectively as MCD mTORpathies. The authors also consider the unique features of these related conditions with particular focus on the practicalities of using neuroimaging techniques currently available to define surgical targets and predict post-surgical outcome. Ultimately, the authors consider the surgical dilemmas faced for each condition.Expert opinion: Considering FCD, TSC, and HME collectively as mTORpathies has some merit; however, a unified approach to presurgical evaluation would seem unachievable. Nevertheless, the authors believe combining genetic-centered classification and morphologic findings using advanced imaging techniques will eventually form the basis of a paradigm when considering candidacy for early surgery.

Surgical Outcome in Extratemporal Epilepsies Based on Multimodal Pre-Surgical Evaluation and Sequential Intraoperative Electrocorticography

Objective: to present the postsurgical outcome of extratemporal epilepsy (ExTLE) patients submitted to preoperative multimodal evaluation and intraoperative sequential electrocorticography (ECoG). Subjects and methods: thirty-four pharmaco-resistant patients with lesional and non-lesional ExTLE underwent comprehensive pre-surgical evaluation including multimodal neuroimaging such as ictal and interictal perfusion single photon emission computed tomography (SPECT) scans, subtraction of ictal and interictal SPECT co-registered with magnetic resonance imaging (SISCOM) and electroencephalography (EEG) source imaging (ESI) of ictal epileptic activity. Surgical procedures were tailored by sequential intraoperative ECoG, and absolute spike frequency (ASF) was calculated in the pre- and post-resection ECoG. Postoperative clinical outcome assessment for each patient was carried out one year after surgery using Engel scores. Results: frontal and occipital resection were the most common surgical techniques applied. In addition, surgical resection encroaching upon eloquent cortex was accomplished in 41% of the ExTLE patients. Pre-surgical magnetic resonance imaging (MRI) did not indicate a distinct lesion in 47% of the cases. In the latter number of subjects, SISCOM and ESI of ictal epileptic activity made it possible to estimate the epileptogenic zone. After one- year follow up, 55.8% of the patients was categorized as Engel class I–II. In this study, there was no difference in the clinical outcome between lesional and non lesional ExTLE patients. About 43.7% of patients without lesion were also seizure- free, p = 0.15 (Fischer exact test). Patients with satisfactory seizure outcome showed lower absolute spike frequency in the pre-resection intraoperative ECoG than those with unsatisfactory seizure outcome, (Mann– Whitney U test, p = 0.005). Conclusions: this study has shown that multimodal pre-surgical evaluation based, particularly, on data from SISCOM and ESI alongside sequential intraoperative ECoG, allow seizure control to be achieved in patients with pharmacoresistant ExTLE epilepsy.

Unilateral prefrontal lobotomy for epilepsy: technique and surgical anatomy

OBJECTIVE

Surgery for frontal lobe epilepsy remains a challenge because of the variable seizure outcomes after surgery. Disconnective procedures are increasingly applied to isolate the epileptogenic focus and avoid complications related to extensive brain resection. Previously, the authors described the anterior quadrant disconnection procedure to treat large frontal lobe lesions extending up to but not involving the primary motor cortex. In this article, they describe a surgical technique for unilateral disconnection of the prefrontal cortex, while providing an accurate description of the surgical and functional anatomy of this disconnective procedure.

METHODS

The authors report the surgical treatment of a 5-month-old boy who presented with refractory epilepsy due to extensive cortical dysplasia of the left prefrontal lobe. In addition, with the aim of both describing the subcortical intrinsic anatomy and illustrating the different connections between the prefrontal lobe and the rest of the brain, the authors dissected six human cadaveric brain hemispheres. These dissections were performed from lateral to medial and from medial to lateral to reveal the various tracts sectioned during the three different steps in the surgery, namely the intrafrontal disconnection, anterior callosotomy, and frontobasal disconnection.

RESULTS

The first step of the dissection involves cutting the U-fibers. During the anterior intrafrontal disconnection, the superior longitudinal fasciculus in the depth of the middle frontal gyrus, the uncinate fasciculus, and the inferior frontooccipital fasciculus in the depth of the inferior frontal gyrus at the level of the anterior insular point are visualized and sectioned, followed by sectioning of the anterior limb of the internal capsule. Once the frontal horn is reached, the anterior callosotomy can be performed to disconnect the genu and the rostrum of the corpus callosum. The intrafrontal disconnection is deepened toward the falx, and at the medial surface, the cingulum is sectioned. The frontobasal disconnection involves cutting the anterior limb of the anterior commissure.

CONCLUSIONS

This technique allows selective isolation of the epileptogenic focus located in the prefrontal lobe to avoid secondary propagation. Understanding the surface and white matter fiber anatomy is essential to safely perform the procedure and obtain a favorable seizure outcome.

Resective surgery for drug-resistant posttraumatic epilepsy: predictors of seizure outcome

OBJECTIVE

The object of this study was to evaluate surgical outcomes and prognosis factors in patients with drug-resistant posttraumatic epilepsy (PTE) who had undergone resective surgery.

METHODS

The authors retrospectively reviewed the records of all patients with drug-resistant PTE who had undergone resective surgery at Sanbo Brain Hospital, Capital Medical University, in the period from January 2008 to December 2016. All patients had a follow-up period of at least 2 years. Seizure outcomes were evaluated according to the International League Against Epilepsy (ILAE) classification. Patients in ILAE classes 1 and 2 during the last 2 years of follow-up were classified as having a favorable outcome; patients in all other classes were considered to have an unfavorable outcome. Univariate analysis and a multivariate logistic regression model in a backward fashion were used to identify the potential predictors of seizure outcomes.

RESULTS

Among 90 patients with a follow-up of 2-10 years (mean ± standard deviation, 5.79 ± 2.84 years), 70% (63 patients) were seizure free, of whom 68.9% (62 patients) had an ILAE class 1 outcome and 1.1% (1 patient) had an ILAE class 2 outcome. Permanent neurological deficits were observed in 10 patients (11.1%). Univariate and multivariate analyses revealed that only the duration of seizures ≤ 8 years was an independent predictor of a favorable seizure outcome (OR 0.34, 95% CI 0.13-0.92).

CONCLUSIONS

Resective surgery is an effective treatment for patients with drug-resistant PTE with an acceptable incidence of complications. The information on prognosis factors suggests that early surgery may offer more benefits to patients with drug-resistant PTE.

Seizures following surgery for supratentorial extratemporal low-grade tumors in children: a multicenter retrospective study

OBJECTIVE

Resection of brain tumors may lead to new-onset seizures but may also reduce seizure rates in patients presenting with seizures. Seizures are seen at presentation in about 24% of patients with brain tumors. For lesional epilepsy in general, early resection is associated with improved seizure control. However, the literature is limited regarding the occurrence of new-onset postoperative seizures, or rates of seizure control in those presenting with seizures, following resections of extratemporal low-grade gliomas (LGGs) in children.

METHODS

Data were collected retrospectively from 4 large tertiary centers for children (< 18 years of age) who underwent resection of a supratentorial extratemporal (STET) LGG. The patients were divided into 4 groups based on preoperative seizure history: no seizures, up to 2 seizures, more than 2 seizures, and uncontrolled or refractory epilepsy. The authors analyzed the postoperative occurrence of seizures and the need for antiepileptic drugs (AEDs) over time for the various subgroups.

RESULTS

The study included 98 children. Thirty patients had no preoperative seizures, 18 had up to 2, 16 had more than 2, and 34 had refractory or uncontrolled epilepsy. The risk for future seizures was higher if the patient had seizures within 1 month of surgery. The risk for new-onset seizures among patients with no seizures prior to surgery was low. The rate of seizures decreased over time for children with uncontrolled or refractory seizures. The need for AEDs was higher in the more active preoperative seizure groups; however, it decreased with time.

CONCLUSIONS

The resection of STET LGGs in children is associated with a low rate of postoperative new-onset epilepsy. For children with preoperative seizures, even with uncontrolled epilepsy, most have a significant improvement in the seizure activity, and many may be weaned off their AEDs.

WITHDRAWN: Analysis of Risk Factors for Prognosis and Infection of Child with Refractory Epilepsy Via Artificial Intelligence Neural Network Image Information

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Lesion Network Localization of Seizure Freedom following MR-guided Laser Interstitial Thermal Ablation

Treatment-resistant epilepsy is a common and debilitating neurological condition, for which neurosurgical cure is possible. Despite undergoing nearly identical ablation procedures however, individuals with treatment-resistant epilepsy frequently exhibit heterogeneous outcomes. We hypothesized that treatment response may be related to the brain regions to which MR-guided laser ablation volumes are functionally connected. To test this, we mapped the resting-state functional connectivity of surgical ablations that either resulted in seizure freedom (N = 11) or did not result in seizure freedom (N = 16) in over 1,000 normative connectomes. There was no difference seizure outcome with respect to the anatomical location of the ablations, and very little overlap between ablation areas was identified using the Dice Index. Ablations that did not result in seizure-freedom were preferentially connected to a number of cortical and subcortical regions, as well as multiple canonical resting-state networks. In contrast, ablations that led to seizure-freedom were more functionally connected to prefrontal cortices. Here, we demonstrate that underlying normative neural circuitry may in part explain heterogenous outcomes following ablation procedures in different brain regions. These findings may ultimately inform target selection for ablative epilepsy surgery based on normative intrinsic connectivity of the targeted volume.

Ictal semiology, functional anatomy and multimodal diagnostic in patients with insular epilepsies

Background

The insula is a hidden part in the cerebral cortex. Insular epilepsy is underrecognized and it bears a special risk for misdiagnosis with regard to nonepileptic seizures or wrong localization of epileptic seizures.

Case presentations

The manuscript describes 2 cases with ictal semiology of paresthesia and pain followed by hyperkinetic movements, noninvasive findings of source localization and/or invasive SEEG exploration.

Conclusion

Magnetic source imaging, ictal SPECT as noninvasive and invasive recordings with depth electrodes (SEEG) can provide important preoperative information for the involvement of insular and periinsular regions in focal pharmacoresistant epilepsies. The optimal use of these methods presupposes extensive knowledge of ictal semiology and other clinical characteristics. The clinical localization hypothesis can be optimally proofed by SEEG exploration.

Network-targeted approach and postoperative resting-state functional magnetic resonance imaging are associated with seizure outcome

OBJECTIVE

Postoperative resting-state functional magnetic resonance imaging (MRI) in children with intractable epilepsy has not been quantified in relation to seizure outcome. Therefore, its value as a biomarker for epileptogenic pathology is not well understood.

METHODS

In a sample of children with intractable epilepsy who underwent prospective resting-state seizure onset zone (SOZ)-targeted epilepsy surgery, postoperative resting-state functional MRI (rs-fMRI) was performed 6 to 12 months later. Graded normalization of the postoperative resting-state SOZ was compared to seizure outcomes, patient, surgery, and anatomical MRI characteristics.

RESULTS

A total of 64 cases were evaluated. Network-targeted surgery, followed by postoperative rs-fMRI normalization was significantly (p < 0.001) correlated with seizure reduction, with a Spearman rank correlation coefficient of 0.83. Of 39 cases with postoperative rs-fMRI SOZ normalization, 38 (97%) became completely seizure free. In contrast, of the 25 cases without complete rs-fMRI SOZ normalization, only 3 (5%) became seizure free. The accuracy of rs-fMRI as a biomarker predicting seizure freedom is 94%, with 96% sensitivity and 93% specificity.

INTERPRETATION

Among seizure localization techniques in pediatric epilepsy, network-targeted surgery, followed by postoperative rs-fMRI normalization, has high correlation with seizure freedom. This study shows that rs-fMRI SOZ can be used as a biomarker of the epileptogenic zone, and postoperative rs-fMRI normalization is a biomarker for SOZ quiescence. ANN NEUROL 2019;86:344-356.

Surgical outcomes and prognostic factors of drug-resistant epilepsy secondary to encephalomalacia

OBJECTIVE

To evaluate long-term outcomes and prognostic factors in patients who underwent surgical resection for drug-resistant epilepsy secondary to encephalomalacia.

METHODS

A total of 143 patients with drug-resistant epilepsy who underwent surgical resection with a follow-up of at least 5 years were included. Seizure outcomes were evaluated based on the International League Against Epilepsy classification. Univariate analysis and a multivariate logistic regression model in a backward fashion were used to identify the potential predictors of seizure outcomes.

RESULTS

Three months after surgery, 102 of 143 (71.3%) patients had achieved favorable seizure outcomes. Five years after surgery, 107 of 143 (74.8%) patients had achieved favorable seizure outcomes. Changes in the postoperative seizure status were observed in 22 of 143 (15.4%) patients during follow-up, but the difference in the seizure-free rate between 3 months and 5 years after surgery was not significant. Univariate and multivariate analyses revealed that only a monthly seizure frequency of >30 seizures (odds ratio = 3.42, 95% confidence interval = 1.19-9.76) and bilateral ictal onset rhythms (odds ratio = 4.46, 95% confidence interval = 1.61-12.39) were independent predictors of unfavorable seizure outcomes.

SIGNIFICANCE

Surgical resection is an effective treatment for patients with drug-resistant epilepsy secondary to encephalomalacia. Knowledge of the predictors of seizure outcomes may help during preoperative counseling and selection of optimal candidates for epilepsy surgery among patients with drug-resistant epilepsy secondary to encephalomalacia.

Safety and effectiveness of stereotactic laser ablation for epileptogenic cerebral cavernous malformations

OBJECTIVE

Magnetic resonance (MR) thermography-guided laser interstitial thermal therapy, or stereotactic laser ablation (SLA), is a minimally invasive alternative to open surgery for focal epilepsy caused by cerebral cavernous malformations (CCMs). We examined the safety and effectiveness of SLA of epileptogenic CCMs.

METHODS

We retrospectively analyzed 19 consecutive patients who presented with focal seizures associated with a CCM. Each patient underwent SLA of the CCM and adjacent cortex followed by standard clinical and imaging follow-up.

RESULTS

All but one patient had chronic medically refractory epilepsy (median duration 8 years, range 0.5-52 years). Lesions were located in the temporal (13), frontal (five), and parietal (one) lobes. CCMs induced magnetic susceptibility artifacts during thermometry, but perilesional cortex was easily visualized. Fourteen of 17 patients (82%) with >12 months of follow-up achieved Engel class I outcomes, of which 10 (59%) were Engel class IA. Two patients who were not seizure-free from SLA alone became so following intracranial electrode-guided open resection. Delayed postsurgical imaging validated CCM involution (median 83% volume reduction) and ablation of surrounding cortex. Histopathologic examination of one previously ablated CCM following open surgery confirmed obliteration. SLA caused no detectable hemorrhages. Two symptomatic neurologic deficits (visual and motor) were predictable, and neither was permanently disabling.

SIGNIFICANCE

In a consecutive retrospective series, MR thermography-guided SLA was an effective alternative to open surgery for epileptogenic CCM. The approach was free of hemorrhagic complications, and clinically significant neurologic deficits were predictable. SLA presents no barrier to subsequent open surgery when needed.

Outcome after individualized stereoelectroencephalography (sEEG) implantation and navigated resection in patients with lesional and non-lesional focal epilepsy

BACKGROUND

Refined localization of the epileptogenic zone (EZ) in patients with pharmacoresistant focal epilepsy proceeding to resective surgery might improve postoperative outcome. We here report seizure outcome after stereo EEG (sEEG) evaluation with individually planned stereotactically implanted depth electrodes and subsequent tailored resection.

METHODS

A cohort of consecutive patients with pharmacoresistant focal epilepsy, evaluated with a non-invasive evaluation protocol and invasive monitoring with personalized, stereotactically implanted depth electrodes for sEEG was analyzed. Co-registration of post-implantation CT scan to presurgical MRI data was used for 3D reconstructions of the patients' brain surface and mapping of neurophysiology data. Individual multimodal 3D maps of the EZ were used to guide subsequent tailored resections. The outcome was rated according to the Engel classification.

RESULTS

Out of 914 patients who underwent non-invasive presurgical evaluation, 85 underwent sEEG, and 70 were included in the outcome analysis. Median follow-up was 31.5 months. Seizure-free outcome (Engel class I A-C, ILAE class 1-2) was achieved in 83% of the study cohort. Patients exhibiting lesional and non-lesional (n = 42, 86% vs. n = 28, 79%), temporal and extratemporal (n = 45, 80% vs. n = 25, 84%), and right- and left-hemispheric epilepsy (n = 44, 82% vs. n = 26, 85%) did similarly well. This remains also true for those with an EZ adjacent to or distant from eloquent cortex (n = 21, 86% vs. n = 49, 82%). Surgical outcome was independent of resected tissue volume.

CONCLUSION

Favourable post-surgical outcome can be achieved in patients with resistant focal epilepsy, using individualized sEEG evaluation and tailored navigated resection, even in patients with non-lesional or extratemporal focal epilepsy.