Early surgical intervention in adult patients with ganglioglioma is associated with improved clinical seizure outcomes

Seizure-outcome after surgery of low-grade epilepsy associated neuro-epithelial tumors

BACKGROUND

Most patients with glioneuronal tumors present with seizures. Although several studies have shown that greater extent of resection improves overall patient survival, few studies have focused on postoperative seizure outcome after resection of these tumors. The aim of this study was to characterize seizure control rates in patients undergoing glioneuronal tumor resection and evaluate the association between poor seizure outcome and tumor recurrence or progression.

METHODS

The study population included patients who had undergone resection of glioneuronal tumors between 2014 and 2019 at our institution. Seizure outcome was assessed using Engel grading. Preoperative seizure characteristics, tumor characteristics, surgical factors, and postoperative seizure outcomes were reviewed.

RESULTS

Twenty-six patients (N.=16, temporal lobe; N.=6, frontal lobe; N.=4, parietal lobe) with mean seizures duration of 56.9-months, were assessed. Histopathologically, N.=15 dysembryoplastic neurepithelial tumor, N.=7 ganglioglioma and N.=4 Diffuse lepto-meningeal neuroepithelial tumor. There were 2 cases of complex DNET and one case of DLMNT had associated cortical dysplasia. At mean follow-up of 49.7 months, N.=20 Engel 1, N.=4 Engel 2 and N.=2 had Engel 3 outcome. N.=20 underwent gross total excision (N.=18 Engel 1 and N.=2 Engel 2) and N.=6 sub-total excision. Among the 4 patients who needed re-surgery, two were in Engel 2 and another two were in Engel 3.

CONCLUSIONS

Good seizure-outcome is likely associated with extent of resection. Younger age of patient, less than one-year of seizure duration and absence of generalization of seizure are good prognostic indicators. The best seizure-control can be achieved by early surgical intervention.

Predicting posttraumatic epilepsy using admission electroencephalography after severe traumatic brain injury

OBJECTIVE

Posttraumatic epilepsy (PTE) develops in as many as one third of severe traumatic brain injury (TBI) patients, often years after injury. Analysis of early electroencephalographic (EEG) features, by both standardized visual interpretation (viEEG) and quantitative EEG (qEEG) analysis, may aid early identification of patients at high risk for PTE.

METHODS

We performed a case-control study using a prospective database of severe TBI patients treated at a single center from 2011 to 2018. We identified patients who survived 2 years postinjury and matched patients with PTE to those without using age and admission Glasgow Coma Scale score. A neuropsychologist recorded outcomes at 1 year using the Expanded Glasgow Outcomes Scale (GOSE). All patients underwent continuous EEG for 3-5 days. A board-certified epileptologist, blinded to outcomes, described viEEG features using standardized descriptions. We extracted 14 qEEG features from an early 5-min epoch, described them using qualitative statistics, then developed two multivariable models to predict long-term risk of PTE (random forest and logistic regression).

RESULTS

We identified 27 patients with and 35 without PTE. GOSE scores were similar at 1 year (p = .93). The median time to onset of PTE was 7.2 months posttrauma (interquartile range = 2.2-22.2 months). None of the viEEG features was different between the groups. On qEEG, the PTE cohort had higher spectral power in the delta frequencies, more power variance in the delta and theta frequencies, and higher peak envelope (all p < .01). Using random forest, combining qEEG and clinical features produced an area under the curve of .76. Using logistic regression, increases in the delta:theta power ratio (odds ratio [OR] = 1.3, p < .01) and peak envelope (OR = 1.1, p < .01) predicted risk for PTE.

SIGNIFICANCE

In a cohort of severe TBI patients, acute phase EEG features may predict PTE. Predictive models, as applied to this study, may help identify patients at high risk for PTE, assist early clinical management, and guide patient selection for clinical trials.

Glioneuronal and Neuronal Tumors of the Central Nervous System

Glioneuronal and neuronal tumors (GNTs) are rare neoplasms composed of neural and glial elements frequently located in the temporal lobe. Epilepsy is the main symptom and diagnosis mostly occurs before adulthood. The great majority of GNTs are WHO grade I tumors, but anaplastic transformations and forms exist. Their common association with focal cortical dysplasia is well recognized and should be taken into consideration during neurophysiological presurgical and surgical planning since the aim of surgery should be the removal of the tumor and of the entire epileptogenic zone according to anatomo-electrophysiological findings. Surgery still remains the cornerstone of symptomatic GNT, while radiotherapy, chemotherapy, and new target therapies are generally reserved for anaplastic, unresectable, or evolving tumors. Furthermore, since many GNTs show overlapping clinical and neuroradiological features, the definition of specific histopathological, genetic, and molecular characteristics is crucial. Epileptological, oncological, neurosurgical, and pathological issues of these tumors make a multidisciplinary management mandatory.

The long-term surgical outcomes of low-grade epilepsy-associated neuroepithelial tumors

OBJECTIVE

This study aimed to evaluate the surgical outcomes and relevant prognostic factors in patients with low-grade epilepsy-associated neuroepithelial tumors (LEAT) and, especially, to develop a scoring system to predict postoperative seizure outcomes.

METHODS

The clinical data of patients who underwent epilepsy surgery for LEAT were retrospectively studied. The surgical outcomes of seizure and neurological statuses in patients were evaluated using Engel classification and modified Rankin Scale (mRS) scoring, respectively. A scoring system of seizure outcomes was constructed based on the weight of the β-coefficient estimate of each predictor in the final multivariate predicting model of seizure outcomes.

RESULTS

Of the 287 patients (106 female) enrolled, the median age was 19 years at surgery and 10 years at seizure onset, with a median duration of epilepsy of 60 months. Among 258 patients who were followed up for at least 12 months, 215 (83.3%) patients had a favorable seizure outcome (Engel class I) after surgery, and 43 (16.7%) patients had an unfavorable seizure outcome; longer duration of epilepsy, discordant magnetoencephalography (MEG) findings, and acute postoperative seizures were significantly included in the scoring system to predict unfavorable seizure outcomes, and in the scoring system, accumulated scoring of 0-19 scores was recorded, which were finally grouped into three risk levels: low risk (risk < 30%), medium risk (30% ≤ risk < 70%), and high risk (risk ≥ 70%). In addition, favorable neurological outcomes (mRS score 0-1) were recorded in 187 (72.5%) patients, while unfavorable neurological outcomes were recorded in 71 (27.5%) patients, which were significantly related to poor seizure control, older age at surgery, and longer duration of epilepsy and hospitalization time.

SIGNIFICANCE

The long-term surgical outcomes of LEAT after surgery were satisfactory. A scoring system for predicting unfavorable seizure outcomes with different risk levels was developed, which could partly guide clinical treatments of LEAT.

Open surgery or laser interstitial thermal therapy for low-grade epilepsy-associated tumors of the temporal lobe: A single-institution consecutive series

Outcomes of treating low-grade epilepsy-associated tumors (LEATs) in the temporal lobe with MRI-guided laser interstitial thermal therapy (MRgLITT) remain poorly characterized. This study aimed to compare the safety and effectiveness of treating temporal lobe LEATs with MRgLITT versus open resection in a consecutive single-institution series. We reviewed all adult patients with epilepsy that underwent surgery for temporal lobe LEATs at our institution between 2002 and 2019, during which time we switched from open surgery to MRgLITT. Surgical outcome was categorized by Engel classification at >12mo follow-up and Kaplan-Meir analysis of seizure freedom. We recorded hospital length of stay, adverse events, and available neuropsychological results. Of 14 total patients, 7 underwent 9 open resections, 6 patients underwent MRgLITT alone, and 1 patient underwent an open resection followed by MRgLITT. Baseline group demographics differed and were notable for preoperative duration of epilepsy of 9.0 years (range 1-36) for open resection versus 14.0 years (range 2-34) for MRgLITT. Median length of stay was one day shorter for MRgLITT compared to open resection (p=<.0001). There were no major adverse events in the series, but there were fewer minor adverse events following MRgLITT. At 12mo follow-up, 50% (5/10) of patients undergoing open resection and 57% (4/7) of patients undergoing MRgLITT were free of disabling seizures (Engel I). When comparing patients who underwent similar procedures in the dominant temporal lobe, patients undergoing MRgLITT had fewer and milder material-specific neuropsychological declines than patients undergoing open resections. In this small series, MRgLITT was comparably safe and effective relative to open resection of temporal lobe LEATs.

Neuropathology of Surgically Managed Epilepsy Specimens

Epilepsy is characterized as recurrent seizures, and it is one of the most prevalent disorders of the human nervous system. A large and diverse profile of different syndromes and conditions can cause perturbations in neural networks that are associated with epilepsy. Advances in neuroimaging and electrophysiological monitoring have enhanced our ability to localize the neuropathological lesions that alter the neural networks giving rise to epilepsy, whereas advances in surgical management have resulted in excellent seizure control in many patients following resections. Histopathologic study using a variety of special stains, molecular analysis, and functional studies of these resected tissues has facilitated the neuropathological characterization of these lesions. Here, we review the neuropathology of common structural lesions that cause epilepsy and are amenable to neurosurgical resection, such as hippocampal sclerosis, focal cortical dysplasia, and its associated principal lesions, including long-term epilepsy-associated tumors, as well as other malformations of cortical development and Rasmussen encephalitis.

Low-grade gangliogliomas in adults: A population-based study

BACKGROUND

Low-grade gangliogliomas (GGs) are rare tumors of the central nervous system in adults. This study aims to define their characteristics, prognostic factors, and the impact of different treatment patterns on survival.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) database was used to investigate the potential clinicopathological factors of low-grade GGs in adult patients (age ≥18 years). Kaplan-Meier method and Cox regression model were utilized to evaluate the associations between variables and overall survival (OS).

RESULTS

A total of 703 adult patients diagnosed with low-grade GGs were identified between 2004 and 2016, with a median follow-up period of 60.0 months. The median age at diagnosis was 32.0 years, with 50.1% of patients being male, 84.2% white people, and 40.2% of married status. The predominant tumor site was located in temporal lobe (38.8%). The median OS time for the whole cohort was not reached. The 5- and 10-year OS rates for patients underwent gross total resection (GTR) were 92.5% and 87.2%, respectively. Univariate and multivariate analysis showed age, gender, tumor site, and treatment pattern were significant factors for OS. The employment of adjuvant radiotherapy (RT) and/or chemotherapy would significantly shorten OS time.

CONCLUSIONS

This is the largest retrospective study of adult low-grade GGs up to date. Younger age, female gender, temporal lobe location, and GTR indicated better survival. Adjuvant RT and/or chemotherapy should not be considered after whatever surgery in adult patients with low-grade GGs, unless the malignant transformation has been confirmed.

Long-Term Epilepsy-Associated Tumors (LEATs): A Single-Center, Retrospective Series and Review of Literature on Factors Affecting the Seizure Outcome

BACKGROUND

Tumors presenting with drug-resistant seizures are termed as long-term epilepsy-associated tumors (LEATs). LEATs are more common in the temporal lobe, occur predominantly in pediatric age, and focal neurological deficits are rare. In this article, we aim to highlight our surgical experience in terms of seizure outcome among LEATs and discuss the factors affecting outcome.

METHODOLOGY

We have retrospectively analyzed all the operated cases of intra-axial brain tumors with seizures (2015-2019). The clinical and radiographic data were collected from the hospital record system. For comparison, 2 groups were made (group 1 with good seizure control, i.e., Engel 1; and group 2 poor seizure outcome, i.e., Engel 2 and 3).

RESULTS

A total of 51 cases were included; the temporal lobe was the most common location (n = 27); 23 patients had seizure frequency of "more than 1 seizure per week." Focal unaware seizures/complex partial seizures were the most common type of seizures encountered (n = 28). At a mean follow-up of 39.60 months, 38 patients had Engel 1 (78.5%) outcome (35 cases [71.05%] had the seizure duration of ≤2 years). The median duration of symptoms (group 1, 25 months vs. group 2, 65 months) was significantly different (P = 0.002). On comparing patients with seizure duration, we found a statistically significant difference (P < 0.00001).

CONCLUSION

A shorter duration of symptoms, younger age of the patient, partial/focal seizures, and gross total excision were predictors of a good seizure outcome. Histopathology of the tumor does not affect the outcome when one compares glioneuronal tumors with non-glioneuronal tumors.

Factors affecting seizure outcome in Long-term epilepsy associated tumors (LEATs) in children and young adolescents

OBJECTIVE

Tumors with seizures as primary mode of presentation are collectively called Long-term epilepsy associated tumors (LEATs or Epileptomas). The overall survival is good so 'seizure outcome' becomes the primary goal rather than neuro-oncological outcome.

METHODS

A retrospective analysis of our surgical database (2015-19) was done to find operated patients of intra-axial brain tumors with age less than 25-years and who had presented with seizures.

RESULTS

The mean age at presentation was 16.44 years (SD + 6.82 years). Complex partial seizures/focal unaware seizures were the most common type of seizures encountered (n = 22) with mean duration of seizures was 49.50 months (SD + 31.04 months). The most common pathology was glioneuronal tumors (GNTs) (n = 17). Gross total resection (GTR) group had a significantly better seizure outcome as compared with the Subtotal resection (STR) group (p = 0.006). Presence of focal or partial seizure was a significant factor pointing towards a better seizure control (p = 0.005).

CONCLUSION

The shorter duration of symptoms, partial/focal seizures and gross total excision were predictors of a good seizure-outcome. Age of the patient and the histopathology of the tumor does not affect seizure-outcome on comparing GNTs with non GNTs.

Factors associated with seizure and cognitive outcomes after epilepsy surgery for low-grade epilepsy-associated neuroepithelial tumors in children

Low-grade epilepsy-associated neuroepithelial tumors (LEATs) are responsible for drug-resistant chronic focal epilepsy, and are the second-most common reason for epilepsy surgery in children. LEATs are extremely responsive to surgical treatment, and therefore epilepsy surgery should be considered as a treatment option for LEATs. However, the optimal time for surgery remains controversial, and surgeries are often delayed. In this review, we reviewed published article on the factors associated with seizure and cognitive outcomes after epilepsy surgery for LEATs in children to help clinicians in their decision whether to pursue epilepsy surgery for LEATs. The achievement of gross total resection may be the most important prognostic factor for seizure freedom. A shorter duration of epilepsy, a younger age at surgery, and extended resection of temporal lobe tumors have also been suggested as favorable prognostic factors in terms of seizure control. Poor cognitive function in children with LEATs is associated with a longer duration of epilepsy and a younger age at seizure onset.

Early and late epilepsy surgery in focal epilepsies associated with long-term epilepsy-associated tumors

OBJECTIVE

Epilepsy surgery is an effective means of treating focal epilepsy associated with long-term epilepsy-associated tumors. This study evaluated a large population of surgically treated patients with childhood onset of epilepsy and a histologically confirmed diagnosis of long-term epilepsy-associated tumors. The authors analyzed long-term seizure outcomes to establish whether the time of surgery and patients' ages were determinant factors.

METHODS

The authors separately investigated several presurgical, surgical, and postsurgical variables in patients operated on before (pediatric group) and at or after (adult group) the age of 18 years. Patients with < 24 months of postsurgical follow-up were excluded from the analysis.

RESULTS

The patients who underwent surgery before 18 years of age showed better seizure outcomes than those after 18 years of age (80% vs 53.3% Engel Class Ia outcome, respectively; p < 0.001). Multivariate analysis showed that the only variables significantly associated with seizure freedom were complete resection of the lesion, a shorter duration of epilepsy, and temporal lobe resection.

CONCLUSIONS

The findings of this study indicate that pediatric patients are more responsive to epilepsy surgery and that a shorter duration of epilepsy, complete resection, and a temporal lobe localization are determinant factors for a positive seizure outcome.

Epilepsy and brain tumors

Seizures are common in patients with brain tumors, and epilepsy can significantly impact patient quality of life. Therefore, a thorough understanding of rates and predictors of seizures, and the likelihood of seizure freedom after resection, is critical in the treatment of brain tumors. Among all tumor types, seizures are most common with glioneuronal tumors (70-80%), particularly in patients with frontotemporal or insular lesions. Seizures are also common in individuals with glioma, with the highest rates of epilepsy (60-75%) observed in patients with low-grade gliomas located in superficial cortical or insular regions. Approximately 20-50% of patients with meningioma and 20-35% of those with brain metastases also suffer from seizures. After tumor resection, approximately 60-90% are rendered seizure-free, with most favorable seizure outcomes seen in individuals with glioneuronal tumors. Gross total resection, earlier surgical therapy, and a lack of generalized seizures are common predictors of a favorable seizure outcome. With regard to anticonvulsant medication selection, evidence-based guidelines for the treatment of focal epilepsy should be followed, and individual patient factors should also be considered, including patient age, sex, organ dysfunction, comorbidity, or cotherapy. As concomitant chemotherapy commonly forms an essential part of glioma treatment, enzyme-inducing anticonvulsants should be avoided when possible. Seizure freedom is the ultimate goal in the treatment of brain tumor patients with epilepsy, given the adverse effects of seizures on quality of life.

Ganglioglioma: Single-institutional experience of 24 cases with review of literature

Background:

Ganglioglioma is a common seizure associated tumor. The goal of this study was to observe the postoperative outcome in patients with gangliogliomas.

Material and Methods:

A total 24 patients with gangliogliomas who underwent surgery at our institute from 2008 to 2011 were included. There were 13 males (54%) in our study. A retrospective analysis for the demographic profile, surgery and outcome was performed using STATA software. Literature on this subject was also reviewed, MEDLINE and PUBMED databases were searched.

Observations:

Sixteen patients presented with signs and symptoms of raised intracranial pressure and 12 patients had seizure disorder. Average age at surgery was 20 years (range 7-50 years). Twelve each were located in the temporal lobe and extra-temporal location. Intra-operative electrocorticography (ECoG) alone in three and image guidance alone were used in two patients, respectively. Both ECoG and image guidance were used in one patient and none of them was used in 18 patients. Gross total resection was achieved in 17 patients. After a mean follow-up of 1.6 years (range 3 months to 2.5 years), out of 12 patients with preoperative seizures, 10 (83.3%) were seizure free (Engel class-I) and 2 (16.6%) belonged to Engel class-II. None of the factors, including age at surgery, seizure duration prior to surgery, type of seizures, use of intra-operative ECoG and image guidance, extent of tumor resection, and surgical strategy proved to have significant correlation with postoperative seizure outcome.

Conclusions:

Surgical treatment is effective and safe for patients with gangliogliomas. Neither intra-operative ECoG nor image guidance necessarily leads to better seizure control, although they are useful adjunct for achieving safe and complete tumor resection.

Rare glial tumors

This chapter describes the epidemiology, pathology, molecular characteristics, clinical and neuroimaging features, treatment, outcome, and prognostic factors of the rare glial tumors. This category includes subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma, astroblastoma, chordoid glioma of the third ventricle, angiocentric glioma, ganglioglioma, desmoplastic infantile astrocytoma and ganglioma, dysembryoplastic neuroepithelial tumor, papillary glioneuronal tumor, and rosette-forming glioneuronal tumor of the fourth ventricle. Many of these tumors, in particular glioneuronal tumors, prevail in children and young adults, are characterized by pharmacoresistant seizures, and have an indolent course, and long survival following surgical resection. Radiotherapy and chemotherapy are reserved for recurrent and/or aggressive forms. New molecular alterations are increasingly recognized.

Resection of cerebral gangliogliomas causing drug-resistant epilepsy: short- and long-term outcomes using intraoperative MRI and neuronavigation

OBJECT Cerebral gangliogliomas (GGs) are highly associated with intractable epilepsy. Incomplete resection due to proximity to eloquent brain regions or misinterpretation of the resection amount is a strong negative predictor for local tumor recurrence and persisting seizures. A potential method for dealing with this obstacle could be the application of intraoperative high-field MRI (iopMRI) combined with neuronavigation. METHODS Sixty-nine patients (31 female, 38 male; median age 28.5 ± 15.4 years) suffering from cerebral GGs were included in this retrospective study. Five patients received surgery twice in the observation period. In 48 of the 69 patients, 1.5-T iopMRI combined with neuronavigational guidance was used. Lesions close to eloquent brain areas were resected with the implementation of preoperative diffusion tensor imaging tractography and blood oxygenation level-dependent functional MRI (15 patients). RESULTS Overall, complete resection was accomplished in 60 of 69 surgical procedures (87%). Two patients underwent biopsy only, and in 7 patients, subtotal resection was accomplished because of proximity to critical brain areas. Excluding the 2 biopsies, complete resection using neuronavigation/iopMRI was documented in 33 of 46 cases (72%) by intraoperative imaging. Remnant tumor mass was identified intraoperatively in 13 of 46 patients (28%). After intraoperative second-look surgery, the authors improved the total resection rate by 9 patients (up to 91% [42 of 46]). Of 21 patients undergoing conventional surgery, 14 (67%) had complete resection without the use of iopMRI. Regarding epilepsy outcome, 42 of 60 patients with seizures (70%) became completely seizure free (Engel Class IA) after a median follow-up time of 55.5 ± 36.2 months. Neurological deficits were found temporarily in 1 (1.4%) patient and permanently in 4 (5.8%) patients. CONCLUSIONS Using iopMRI combined with neuronavigation in cerebral GG surgery, the authors raised the rate of complete resection in this series by 19%. Given the fact that total resection is a strong predictor of long-term seizure control, this technique may contribute to improved seizure outcome and reduced neurological morbidity.

Epilepsy associated tumors: Review article

Long-term epilepsy associated tumors (LEAT) represent a well known cause of focal epilepsies. Glioneuronal tumors are the most frequent histological type consisting of a mixture of glial and neuronal elements and most commonly arising in the temporal lobe. Cortical dysplasia or other neuronal migration abnormalities often coexist. Epilepsy associated with LEAT is generally poorly controlled by antiepileptic drugs while, on the other hand, it is high responsive to surgical treatment. However the best management strategy of tumor-related focal epilepsies remains controversial representing a contemporary issues in epilepsy surgery. Temporo-mesial LEAT have a widespread epileptic network with complex epileptogenic mechanisms. By using an epilepsy surgery oriented strategy LEAT may have an excellent seizure outcome therefore surgical treatment should be offered early, irrespective of pharmacoresistance, avoiding both the consequences of uncontrolled seizures as well as the side effects of prolonged pharmacological therapy and the rare risk of malignant transformation.

Factors associated with preoperative and postoperative epileptic seizure in patients with cerebral ganglioglioma

OBJECTIVE

To explore the factors associated with preoperative epileptic seizure and surgical outcome in patients with cerebral gangliolioma (GG).

METHODS

A total of 31 consecutive patients with pathologically confirmed ganglioglioma and surgically treated from January 2003 to June 2011 in West China Hospital of Sichuan University were retrospectively reviewed. Clinical data, surgical procedure and follow-up information were collected and analyzed.

RESULTS

Nineteen patients presented with epileptic seizure, of which 63.2% were males. The mean age at epilepsy surgery and mean seizure duration were 25.6 years and 2.3 years respectively. Factors associated with preoperative epileptic seizure were supratentorial lesion and temporal lobe involvement (p=0.016 and 0.008). Intraoperative electrocorticography (ECoG) was applied in 8 out of 19 epilepsy patients. Eighteen achieved total tumor excision. After a mean follow up of 2.8 (1.3-6.3) years, 11 (68.8%, 11/16) achieved seizure free (Engel class I). Early surgery (seizure duration <3 years) was a significant predictor of favorable seizure outcome (p=0.013). None of the factors including seizure type, tumor location, neuroimaging characteristics and application of intraoperative ECoG or surgical strategy were found to be significantly associated with postoperative seizure outcome. Postoperative combination of AEDs was unnecessary for seizure control.

CONCLUSIONS

Ganglioglioma with temporal lobe involvement usually associated with intractable epilepsy. Early surgical resection is strongly suggested to achieve favorable outcome. Intraoperative ECoG is not inevitable and simple lesionectomy is sufficient for satisfactory seizure control. Early accurate diagnosis of ganglioglioma should be established on comprehensive consideration and plays an important role in dealing with these patients.

Epilepsy related to developmental tumors and malformations of cortical development

Structural abnormalities of the brain are increasingly recognized in patients with neurodevelopmental delay and intractable focal epilepsies. The access to clinically well-characterized neurosurgical material has provided a unique opportunity to better define the neuropathological, neurochemical, and molecular features of epilepsy-associated focal developmental lesions. These studies help to further understand the epileptogenic mechanisms of these lesions. Neuropathological evaluation of surgical specimens from patients with epilepsy-associated developmental lesions reveals two major pathologies: focal cortical dysplasia and low-grade developmental tumors (glioneuronal tumors). In the last few years there have been major advances in the recognition of a wide spectrum of developmental lesions associated with a intractable epilepsy, including cortical tubers in patients with tuberous sclerosis complex and hemimegalencephaly. As an increasing number of entities are identified, the development of a unified and comprehensive classification represents a great challenge and requires continuous updates. The present article reviews current knowledge of molecular pathogenesis and the pathophysiological mechanisms of epileptogenesis in this group of developmental disorders. Both emerging neuropathological and basic science evidence will be analyzed, highlighting the involvement of different, but often converging, pathogenetic and epileptogenic mechanisms, which may create the basis for new therapeutic strategies in these disorders.

Rates and predictors of seizure freedom in resective epilepsy surgery: an update

Epilepsy is a debilitating neurological disorder affecting approximately 1 % of the world's population. Drug-resistant focal epilepsies are potentially surgically remediable. Although epilepsy surgery is dramatically underutilized among medically refractory patients, there is an expanding collection of evidence supporting its efficacy which may soon compel a paradigm shift. Of note is that a recent randomized controlled trial demonstrated that early resection leads to considerably better seizure outcomes than continued medical therapy in patients with pharmacoresistant temporal lobe epilepsy. In the present review, we provide a timely update of seizure freedom rates and predictors in resective epilepsy surgery, organized by the distinct pathological entities most commonly observed. Class I evidence, meta-analyses, and individual observational case series are considered, including the experiences of both our institution and others. Overall, resective epilepsy surgery leads to seizure freedom in approximately two thirds of patients with intractable temporal lobe epilepsy and about one half of individuals with focal neocortical epilepsy, although only the former observation is supported by class I evidence. Two common modifiable predictors of postoperative seizure freedom are early operative intervention and, in the case of a discrete lesion, gross total resection. Evidence-based practice guidelines recommend that epilepsy patients who continue to have seizures after trialing two or more medication regimens should be referred to a comprehensive epilepsy center for multidisciplinary evaluation, including surgical consideration.

Seizures in low-grade gliomas: natural history, pathogenesis, and outcome after treatments

Seizures represent a common symptom in low-grade gliomas; when uncontrolled, they significantly contribute to patient morbidity and negatively impact quality of life. Tumor location and histology influence the risk for epilepsy. The pathogenesis of tumor-related epilepsy is multifactorial and may differ among tumor histologies (glioneuronal tumors vs diffuse grade II gliomas). Gross total resection is the strongest predictor of seizure freedom in addition to clinical factors, such as preoperative seizure duration, type, and control with antiepileptic drugs (AEDs). Epilepsy surgery may improve seizure control. Radiotherapy and chemotherapy with alkylating agents (procarbazine + CCNU+ vincristine, temozolomide) are effective in reducing the frequency of seizures in patients with pharmacoresistant epilepsy. Newer AEDs (levetiracetam, topiramate, lacosamide) seem to be better tolerated than the old AEDs (phenobarbital, phenytoin, carbamazepine), but there is lack of evidence regarding their superiority in terms of efficacy.

Seizure outcome of surgical treatment of focal epilepsy associated with low-grade tumors in children

OBJECT

Low-grade tumor (LGT) is an increasingly recognized cause of focal epilepsies, particularly in children and young adults, and is frequently associated with cortical dysplasia. The optimal surgical treatment of epileptogenic LGTs in pediatric patients has not been fully established.

METHODS

In the present study, the authors retrospectively reviewed 30 patients (age range 3-18 years) who underwent surgery for histopathologically confirmed LGTs, in which seizures were the only clinical manifestation. The patients were divided into 2 groups according to the type of surgical treatment: patients in Group A (20 cases) underwent only tumor removal (lesionectomy), whereas patients in Group B (11 cases) underwent removal of the tumor and the adjacent epileptogenic zone (tailored surgery). One of the patients, who underwent 2 operations, is included in both groups. Follow-up ranged from 1 to 17 years.

RESULTS

Sixteen (80%) of 20 patients in Group A had an Engel Class I outcome. In this group, 3 of 4 patients who were in Engel Classes II and III had temporomesial lesions. All patients in Group B had temporomesial tumors and were seizure free (Engel Class I). In this series, in temporolateral and extratemporal tumor locations, lesionectomy yielded a good seizure outcome. In addition, a young age at seizure onset (in particular < 4 years) was associated with a poor seizure outcome.

CONCLUSIONS

Tailored resection in temporomesial LGTs was associated with excellent seizure outcome, indicating that an adequate presurgical evaluation including extensive neurophysiological evaluation (long-term videoelectroencephalography monitoring) to plan appropriate surgical strategy is advised.

Long-term seizure control outcomes after resection of gangliogliomas

BACKGROUND

Gangliogliomas are rare glioneuronal tumors that typically cause refractory seizures during the first 3 decades of life.

OBJECTIVE

To determine the prognosticators of seizure outcome after surgery for ganglioglioma.

METHODS

We reviewed the cases of 66 patients who underwent resection of gangliogliomas at the University of California, San Francisco. Demographic, seizure history, and operative data were examined for statistical association with postoperative seizure outcomes.

RESULTS

Of the 66 patients who underwent surgical resection of ganglioglioma, 49 patients (74%) presented with a history of seizures. Of those 49 patients, 50% presented with intractable epilepsy. Temporal lobe gangliogliomas were present in 76% of the patients who presented with a history of seizures. Electrocorticography was performed on 35% of the patients, and of those patients, 82% underwent extended lesionectomy to remove abnormally epileptogenic extralesional tissue. The median follow-up duration was 6.9 years, during which tumor progression occurred in 38% of patients who underwent subtotal resection and in 8% of patients who underwent gross total resection (P = .02). Overall, 85% of patients were seizure free (International League Against Epilepsy class I or II) 5 years after surgery. Subtotal resection was associated with poor seizure outcomes 1 year after resection (odds ratio = 14.6; 95% confidence interval = 2.4-87.7): rates of seizure freedom were 54% after subtotal resection, 96% after gross total resection, and 93% after gross total resection with intraoperative electrocorticography-guided extended lesionectomy.

CONCLUSION

We report excellent long-term seizure control outcomes after surgery for gangliogliomas. Intraoperative electrocorticography may be a useful adjunct for guiding extended resection in certain pharmacoresistant epilepsy patients with gangliogliomas. Subtotal resection is associated with higher rates of tumor progression and nonoptimal seizure outcomes.

Long-term epilepsy-associated tumors

The term long-term epilepsy associated tumor (LEAT) encompasses lesions identified in patients investigated for long histories (often 2 years or more) of drug-resistant epilepsy. They are generally slowly growing, low grade, cortically based tumors, more often arising in younger age groups and in many cases exhibit neuronal in addition to glial differentiation. Gangliogliomas and dysembryoplastic neuroepithelial tumors predominate in this group. LEATs are further united by cyto-architectural changes that may be present in the adjacent cortex which have some similarities to developmental focal cortical dysplasias (FCD); these are now grouped as FCD type IIIb in the updated International League Against Epilepsy (ILAE) classification. In the majority of cases, surgical treatments are beneficial from both perspectives of managing the seizures and the tumor. However, in a minority, seizures may recur, tumors may show regrowth or recurrence, and rarely undergo anaplastic progression. Predicting and identifying tumors likely to behave less favorably are key objectives of the neuropathologist. With immunohistochemistry and modern molecular pathology, it is becoming increasingly possible to refine diagnostic groups. Despite this, some LEATs remain difficult to classify, particularly tumors with "non-specific" or diffuse growth patterns. Modification of LEAT classification is inevitable with the goal of unifying terminological criteria applied between centers for accurate clinico-pathological-molecular correlative data to emerge. Finally, establishing the epileptogenic components of LEAT, either within the lesion or perilesional cortex, will elucidate the cellular mechanisms of epileptogenesis, which in turn will guide optimal surgical management of these lesions.

Seizure outcome with surgical management of epileptogenic ganglioglioma: a study of 55 patients

BACKGROUND

Ganglioglioma is a common seizure-associated tumor, and some factors that may influence the postoperative seizure outcome have not been discussed or are controversial. The goal of this study was to observe the postoperative seizure outcome and the prognostic factors in patients with epileptogenic gangliogliomas.

METHODS

In this retrospective study, 55 patients with epileptogenic gangliogliomas underwent surgery. Postoperative seizure outcome during follow-up was recorded, and possible postoperative prognostic factors were analyzed.

RESULTS

There were 30 males and 25 females in our study. Twenty patients presented with chronic seizures. The mean age at surgery was 19.39 years, and the mean seizure duration prior to surgery was 4.47 years. Forty-three patients had complex partial seizures, 12 patients had simple partial seizures, and secondary generalization occurred in 18 patients. Brain magnetic resonance imaging (MRI) revealed 32 tumors were located in the temporal lobe and 23 in the extratemporal lobes. Intraoperative electrocorticography (ECoG) and intraoperative ultrasound (IOUS) were used in 42 and 11 patients, respectively. Gross total resection of the tumor was achieved in 42 patients (1 patient underwent reoperation), subtotal resection in 11, and partial resection in 2. Simple lesionectomy and tailored epilepsy surgery were performed in 24 and 31 patients, respectively. After a mean follow-up of 3.27 years, 48 patients, including 1 re-operated patient, were seizure free (Engel class I). None of the factors, including age at surgery, seizure duration prior to surgery, the type of seizures, use of intraoperative ECoG and IOUS, extent of tumor resection, and surgical strategy, proved to be significantly correlated with postoperative seizure outcome.

CONCLUSIONS

Surgical treatment is effective and safe for patients with epileptogenic gangliogliomas. Early surgical intervention is necessary for achieving early seizure control. Neither intraoperative ECoG nor IOUS necessarily leads to better seizure control, although the latter can be helpful in achieving complete tumor resection. Simple lesionectomy is sufficient for favorable postoperative seizure outcome.

Factors associated with seizure freedom in the surgical resection of glioneuronal tumors

PURPOSE

Gangliogliomas (GGs) and dysembryoplastic neuroepithelial tumors (DNETs) are low-grade brain tumors of glioneuronal origin that commonly present with seizures. Achieving seizure control in patients with glioneuronal tumors remains underappreciated, as tumor-related epilepsy significantly affects patients' quality-of-life.

METHODS

We performed a quantitative and comprehensive systematic literature review of seizure outcomes after surgical resection of GGs and DNETs associated with seizures. We evaluated 910 patients from 39 studies, and stratified outcomes according to several potential prognostic variables.

KEY FINDINGS

Overall, 80% of patients were seizure-free after surgery (Engel class I), whereas 20% continued to have seizures (Engel class II-IV). We observed significantly higher rates of seizure-freedom in patients with ≤1 year duration of epilepsy compared to those with >1 year of seizures [odds ratio (OR) 9.48; 95% confidence interval (CI) 2.26-39.66], and with gross-total resection over subtotal lesionectomy (OR 5.34; 95% CI 3.61-7.89). In addition, the presence of secondarily generalized seizures preoperatively predicted a lower rate of seizure-freedom after surgery (OR 0.40; 95% CI 0.24-0.66). Outcomes did not differ significantly between adults and children, patients with temporal lobe versus extratemporal tumors, pathologic diagnosis of GG versus DNET, medically controlled versus refractory seizures, or with the use of electrocorticography (ECoG). Extended resection of temporal lobe tumors, with hippocampectomy and/or corticectomy, conferred additional benefit.

SIGNIFICANCE

These results suggest that early operative intervention and gross-total resection are critically important factors in achieving seizure-freedom, and thus improving quality-of-life, in patients with glioneuronal tumors causing epilepsy.

Surgical management of glioneuronal tumors with drug-resistant epilepsy

In this review, we discuss the options for the surgical management of glioneuronal tumors (GNTs) associated with drug-resistant epilepsy, with an emphasis on the surgical issues involved in addressing the epileptogenic nature of these lesions. We briefly summarize the pathological hallmarks of these lesions in order to outline how these tumors contribute to seizure activity. Understanding the pathophysiology of these lesions is important in discussing the advantages and disadvantages of different surgical strategies. There have been a number of studies that have investigated the utility of different surgical approaches in improving seizure outcome, and we highlight some of these studies in order to shed light on surgical issues related to these tumors.

Focal epilepsy associated with glioneuronal tumors

Glioneuronal tumors are an increasingly recognized cause of partial seizures that occur primarily in children and young adults. Focal epilepsy associated with glioneuronal tumors is often resistant to pharmacological treatment. The cellular mechanisms underlying the epileptogenicity of glioneuronal tumors remain largely unknown. The involved mechanisms are certain to be multifactorial and depend on specific tumor histology, integrity of the blood-brain barrier, characteristics of the peritumoral environment, circuit abnormalities, or cellular and molecular defects. Glioneuronal tumors presenting with epilepsy were observed to have relatively benign biological behavior. The completeness of the tumor resection is of paramount importance in avoiding tumor progression and malignant transformation, which are rare in cases of epileptogenic glioneuronal tumors. An evolving understanding of the various mechanisms of tumor-related epileptogenicity may also lead to a more defined surgical objective and effective therapeutic strategies, including antiepileptogenic treatments, to prevent epilepsy in at-risk patients.