Dysembryoplastic neuroepithelial tumors: epileptogenicity related to histologic subtypes

Epilepsy in Patients With Primary CNS Lymphoma: Prevalence, Risk Factors, and Prognostic Significance

BACKGROUND AND OBJECTIVES

Epilepsy is a common comorbidity of brain tumors; however, little is known about the prevalence, onset time, semiology, and risk factors of seizures in primary CNS lymphoma (PCNSL). Our objectives were to determine the prevalence of epilepsy in PCNSL, to identify factors associated with epilepsy, and to investigate the prognostic significance of seizures in PCNSL.

METHODS

We performed an observational, retrospective single-center study at a tertiary neuro-oncology center (2011-2023) including immunocompetent patients with PCNSL and no history of seizures. We collected clinical, imaging, and treatment data; seizure status over the course of PCNSL; and oncological and seizure outcome. The primary outcome was to determine the prevalence of epilepsy. Furthermore, we aimed to identify clinical, radiologic, and treatment-related factors associated with epilepsy. Univariate analyses were conducted using the χ2 test for categorical variables and unpaired t test for continuous variables. Predictors identified in the unadjusted analysis were included in backward stepwise logistic regression models.

RESULTS

We included 330 patients, 157 (47.6%) were male, median age at diagnosis was 68 years, and the median Karnofsky Performance Status score was 60. Eighty-three (25.2%) patients had at least 1 seizure from initial diagnosis to the last follow-up, 40 (12.1%) as the onset symptom, 16 (4.8%) during first line of treatment, 27 (8.2%) at tumor progression and 6 (1.8%) while in remission. Focal aware seizures were the most frequent seizure type, occurring in 43 (51.8%) patients. Seizure freedom under antiseizure medication was observed in 97.6% patients. Cortical contact (odds ratio [OR] 8.6, 95% CI 4.2-15.5, p < 0.001) and a higher proliferation index (OR 5.7, 95% CI 1.3-26.2, p = 0.02) were identified as independent risk factors of epilepsy. Patients with PCNSL and epilepsy had a significantly shorter progression-free survival (median progression-free survival 9.6 vs 14.1 months, adjusted hazard ratio 1.4, 95% CI 1.0-1.9, p = 0.03), but not a significantly shorter overall survival (17 vs 44.1 months, log-rank test, p = 0.09).

DISCUSSION

Epilepsy affects a quarter of patients with PCNSL, with half experiencing it at the time of initial presentation and potentially serving as a marker of disease progression. Further research is necessary to assess the broader applicability of these findings because they are subject to the constraints of a retrospective design and tertiary center setting.

Imaging of pediatric glioneuronal and neuronal tumors

Glioneuronal tumors (GNTs) are an expanding group of primary CNS neoplasms, commonly affecting children, adolescents and young adults. Most GNTs are relatively indolent, low-grade, WHO grade I lesions. In the pediatric age group, GNTs have their epicenter in the cerebral cortex and present with seizures. Alterations in the mitogen-activated protein kinase (MAPK) pathway, which regulates cell growth, are implicated in tumorigenesis. Imaging not only plays a key role in the characterization and pre-surgical evaluation of GNTs but is also crucial role in follow-up, especially with the increasing use of targeted inhibitors and immunotherapies. In this chapter, we review the clinical and imaging perspectives of common pediatric GNTs.

Long-term seizure outcome after epilepsy surgery of neuroglial tumors

Purpose

Neuroglial tumors are frequently associated with pharmacorefractory epilepsies. However, comprehensive knowledge about long-term outcomes after epilepsy surgery and the main prognostic factors for outcome is still limited. We sought to evaluate long-term outcomes and potential influencing factors in a large cohort of patients who underwent surgery for neuroglial tumors in a single-center setting.

Methods

The study analyzed the outcomes of 107 patients who underwent epilepsy surgery for neuroglial tumors between 2001 and 2020 at the Department of Epileptology, University Hospital Bonn, in Germany. The outcomes were evaluated using Engel classification. Differences in outcome related to potential prognostic factors were examined using the Chi2-test, Fisher's exact test and sign test. Additionally, stepwise logistic regression analysis was employed to identify independent prognostic factors.

Results

Complete seizure freedom (Engel Class IA) was achieved in 75% of the operated patients at 12 months, and 56% at the last follow-up visit (70.4 ± 6.2 months, median: 40 months). Completeness of resection was a crucial factor for both 12-month follow-up outcomes and the longest available outcomes, whereas lobar tumor localization, histology (ganglioglioma vs. dysembryoplastic neuroepithelial tumor), history of bilateral tonic-clonic seizures prior to surgery, invasive diagnostics, side of surgery (dominant vs. non-dominant hemisphere), age at epilepsy onset, age at surgery, and epilepsy duration did not consistently impact postsurgical outcomes. Among temporal lobe surgeries, patients who underwent lesionectomy and lesionectomy, including hippocampal resection, demonstrated similar outcomes.

Conclusion

Neuroglial tumors present as excellent surgical substrates in treating structural epilepsy. To achieve an optimal postsurgical outcome, a complete lesion resection should be pursued whenever possible.

Epileptic seizures in patients with primary central nervous system lymphoma: A systematic review

BACKGROUND

Primary central nervous system lymphoma (PCNSL) accounts for less than 5% of primary brain tumors. Epileptic seizures are a common manifestation of brain tumors; however, literature on the prevalence, characteristics, and oncological implications of seizures in patients with PCNSL is limited, and the management of antiepileptic drugs (AEDs) is unclear. This review aimed to summarize the existing knowledge on seizures in PCNSL, their potential association with surgery, oncological treatment, survival rates, and management of AEDs.

METHODS

A systematic review was performed according to the PRISMA recommendations and included articles published between 1953 and 2023 describing seizures in patients with PCNSL.

RESULTS

The search identified 282 studies, of which 21 were included. Up to 33% of patients with PCNSL developed seizures, mostly at the initial presentation. Little information was found on changes in seizure incidence through the course of the disease, and no details were found on seizure frequency, the percentage of treatment-resistant patients, or the evolution of seizures at remission. Younger age, cortical location, and immunodeficiency have been identified as potential risk factors for seizures, but evidence is very limited. The growing use of vigorous treatments including intensive chemotherapy with autologous stem cell transplantation and immunotherapy with CAR-T cells is associated with a higher incidence of seizures. The association between seizure development and patient mortality in PCNSL remains unknown. There are no data on AED prophylaxis or the use of specific AEDs in PCNSL.

CONCLUSIONS

Further studies are needed to investigate seizures in larger cohorts of PCNSL, to clarify their prevalence, better characterize them, identify risk factors, analyze survival rates, and make recommendations on AED management. We recommend following general practice guidelines for seizures symptomatic of brain tumors and not to prescribe AED prophylaxis in PCNSL.

Atypical presentation of dysembryoplastic neuroepithelial tumor in an adult without epilepsy: a case report

Aim of the study: Dysembryoplastic neuroepithelial tumor (DNET) is a rare glioneuronal tumor usually found in the temporal lobe of children and young adults. DNETs are commonly associated with drug-resistant partial seizures, with most cases diagnosed before age 20. Asymptomatic brain tumors are rare in the general healthy population, and the frequency of incidental DNETs in adults remains unknown.Materials and methods: We report the case of a 34-year-old healthy man who presented with a facial rash but was incidentally found to have a large T1 hypointense lesion in the left temporal cortex on neuroimaging. The patient opted for surgical removal of the mass, which was subsequently identified as a DNET, positive for a fibroblast growth factor receptor (FGFR) mutation.Results: This case report presents the first incidentally discovered DNET in an adult without epilepsy, highlighting its atypical presentation. In addition, the presence of an FGFR mutation emphasizes its role in DNET pathogenesis and potential therapeutic implications. DNETs exhibit varied behavior based on age, tumor location, and cortical dysplasia.Conclusions: In this case, the absence of seizure onset may be attributed to the lack of cortical dysplasia. Further research is needed to understand the incidence of DNETs and their association with seizure onset and cortical dysplasia.

Long-Term Seizure Outcomes and Predictors in Patients with Dysembryoplastic Neuroepithelial Tumors Associated with Epilepsy

OBJECTIVE

To determine the predictors and the long-term outcomes of patients with seizures following surgery for dysembryoplastic neuroepithelial tumors (DNTs); Methods: Clinical data were collected from medical records of consecutive patients of the Department of Neurosurgery of Sanbo Brain Hospital of Capital Medical University with a pathological diagnosis of DNT and who underwent surgery from January 2008 to July 2021. All patients were followed up after surgery for at least one year. We estimated the cumulative rate of seizure recurrence-free and generated survival curves. A log-rank (Mantel-Cox) test and a Cox proportional hazard model were performed for univariate and multivariate analysis to analyze influential predictors; Results: 63 patients (33 males and 30 females) were included in this study. At the final follow-up, 49 patients (77.8%) were seizure-free. The cumulative rate of seizure recurrence-free was 82.5% (95% confidence interval (CI) 71.8-91.3%), 79.0% (95% CI 67.8-88.6%) and 76.5% (95% CI 64.8-87.0%) at 2, 5, and 10 years, respectively. The mean time for seizure recurrence-free was 6.892 ± 0.501 years (95% CI 5.91-7.87). Gross total removal of the tumor and a short epilepsy duration were significant predictors of seizure freedom. Younger age of seizure onset, bilateral interictal epileptiform discharges, and MRI type 3 tumors were risk factors for poor prognosis; Conclusions: A favorable long-term seizure outcome was observed for patients with DNT after surgical resection. Predictor analysis could effectively guide the clinical work and evaluate the prognosis of patients with DNT associated with epilepsy.

Pre-surgical evaluation challenges and long-term outcome in children operated on for Low Grade Epilepsy Associated brain Tumors

OBJETIVE

Analyze pre-surgical evaluation modalities, surgical failures, long-term results of surgery and neurocognitive outcome in children with Low-grade Epilepsy Associated brain Tumors (LEAT).

METHODS

Retrospective observational study of 37 children who underwent epilepsy surgery, with a minimum follow-up of 12 months. At time of surgery, pharmaco-sensitivity (Group 1; n = 8) and drug-resistance (Group 2; n = 29), were considered.

RESULTS

Age range of seizure onset was 5 months-14 years (mean 5.73years) and age at surgery was 2.2-18.7years (mean 10.7years). Gangliogliomas (35.1%) or DNTs (29.7%), combined or not to a focal cortical dysplasia (FCD), were the most frequent. Extended lesionectomy 16 children (43.2%) were the most frequently used surgical approach in both groups. At one year of follow-up, 36 children (97.2%) were classified as Engel I. Within the age-range studied, duration of epilepsy and time to surgery appeared to have no impact on clinical and neurocognitive outcome in both groups. It is noteworthy, however, that antiseizure medications (ASMs) were withdrawn in 100% of the pharmacosensitive group vs 34.5% of the drug-resistant group (p = 0.002). In children with a pharmaco-sensitive epilepsy, neurocognitive evaluation showed significant improvement in the verbal comprehension index (p = 0.029).

CONCLUSIONS

Epilepsy-surgery is a safe therapeutic option for LEATs including for children with seizures controlled by ASMs. Presence of associated lesions is not rare. Comprehensive pre-surgical evaluation increases the chances for control of the seizures, the early discontinuation of medications and favours neurocognitive development.

Altered Extracellular Matrix as an Alternative Risk Factor for Epileptogenicity in Brain Tumors

Seizures are one of the most common symptoms of brain tumors. The incidence of seizures differs among brain tumor type, grade, location and size, but paediatric-type diffuse low-grade gliomas/glioneuronal tumors are often highly epileptogenic. The extracellular matrix (ECM) is known to play a role in epileptogenesis and tumorigenesis because it is involved in the (re)modelling of neuronal connections and cell-cell signaling. In this review, we discuss the epileptogenicity of brain tumors with a focus on tumor type, location, genetics and the role of the extracellular matrix. In addition to functional problems, epileptogenic tumors can lead to increased morbidity and mortality, stigmatization and life-long care. The health advantages can be major if the epileptogenic properties of brain tumors are better understood. Surgical resection is the most common treatment of epilepsy-associated tumors, but post-surgery seizure-freedom is not always achieved. Therefore, we also discuss potential novel therapies aiming to restore ECM function.

The genomic landscape of dysembryoplastic neuroepithelial tumours and a comprehensive analysis of recurrent cases

AIMS

Dysembryoplastic neuroepithelial tumour (DNT) is a glioneuronal tumour that is challenging to diagnose, with a wide spectrum of histological features. Three histopathological patterns have been described: specific DNTs (both the simple form and the complex form) comprising the specific glioneuronal element, and also the non-specific/diffuse form which lacks it, and has unclear phenotype-genotype correlations with numerous differential diagnoses.

METHODS

We used targeted methods (immunohistochemistry, fluorescence in situ hybridisation and targeted sequencing) and large-scale genomic methodologies including DNA methylation profiling to perform an integrative analysis to better characterise a large retrospective cohort of 82 DNTs, enriched for tumours that showed progression on imaging.

RESULTS

We confirmed that specific DNTs are characterised by a single driver event with a high frequency of FGFR1 variants. However, a subset of DNA methylation-confirmed DNTs harbour alternative genomic alterations to FGFR1 duplication/mutation. We also demonstrated that a subset of DNTs sharing the same FGFR1 alterations can show in situ progression. In contrast to the specific forms, "non-specific/diffuse DNTs" corresponded to a heterogeneous molecular group encompassing diverse, newly-described, molecularly distinct entities.

CONCLUSIONS

Specific DNT is a homogeneous group of tumours sharing characteristics of paediatric low-grade gliomas: a quiet genome with a recurrent genomic alteration in the RAS-MAPK signalling pathway, a distinct DNA methylation profile and a good prognosis but showing progression in some cases. The "non-specific/diffuse DNTs" subgroup encompasses various recently described histomolecular entities, such as PLNTY and diffuse astrocytoma, MYB or MYBL1 altered.

Dysembryoplastic Neuroepithelial Tumor: A Benign but Complex Tumor of the Cerebral Cortex

Dysembryoplastic neuroepithelial tumor (DNET) is a distinct type of low-grade glioneuronal tumor. Clinically, DNET is highly associated with intractable epilepsy in young children and adolescents. Therefore, the burden of the tumor comprises oncological concerns (recurrence), seizure control, and quality of life. The pathology of DNET is characterized by glioneuronal elements and floating neurons. Grossly, many DNETs harbor separate nodules on the medial side of the mass. Some of the satellite lesions are bone fide tumor nodules that grow during the follow-up. Therefore, removing all satellite lesions may be important to prevent tumor progression. Seizure control is highly dependent on the complete removal of tumors, and the presence of satellite lesions also exerts a negative impact on seizure outcomes.

Transcriptomic profiling of nonneoplastic cortical tissues reveals epileptogenic mechanisms in dysembryoplastic neuroepithelial tumors

Low-grade dysembryoplastic neuroepithelial tumors (DNTs) are a frequent cause of drug-refractory epilepsy. Molecular mechanisms underlying seizure generation in these tumors are poorly understood. This study was conducted to identify altered genes in nonneoplastic epileptogenic cortical tissues (ECTs) resected from DNT patients during electrocorticography (ECoG)-guided surgery. RNA sequencing (RNAseq) was used to determine the differentially expressed genes (DEGs) in these high-spiking ECTs compared to non-epileptic controls. A total of 477 DEGs (180 upregulated; 297 downregulated) were observed in the ECTs compared to non-epileptic controls. Gene ontology analysis revealed enrichment of genes belonging to the following Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways: (i) glutamatergic synapse; (ii) nitrogen metabolism; (iii) transcriptional misregulation in cancer; and (iv) protein digestion and absorption. The glutamatergic synapse pathway was enriched by DEGs such as GRM4, SLC1A6, GRIN2C, GRM2, GRM5, GRIN3A, and GRIN2B. Enhanced glutamatergic activity was observed in the pyramidal neurons of ECTs, which could be attributed to altered synaptic transmission in these tissues compared to non-epileptic controls. Besides glutamatergic synapse, altered expression of other genes such as GABRB1 (synapse formation), SLIT2 (axonal growth), and PROKR2 (neuron migration) could be linked to epileptogenesis in ECTs. Also, upregulation of GABRA6 gene in ECTs could underlie benzodiazepine resistance in these patients. Neural cell-type-specific gene set enrichment analysis (GSEA) revealed transcriptome of ECTs to be predominantly contributed by microglia and neurons. This study provides first comprehensive gene expression profiling of nonneoplastic ECTs of DNT patients and identifies genes/pathways potentially linked to epileptogenesis.

Surgical resection of dysembryoplatic neuroepithelioma tumor associated with epilepsy based on imaging classification

OBJECTIVE

Dysembryoplastic neuroepithelioma tumors (DNETs) are rare glioneuronal tumors usually present with partial epilepsy. We analyzed the surgical curative effect of DNETs based on imaging classification.

METHODS

The clinical, neuroimaging, seizure history, neuropathological data, and other medical records of 21 cases of cerebral hemisphere DNETs were collected and analyzed retrospectively. According to the magnetic resonance imaging (MRI) classification of Chassoux, these cases were divided into 8 cases of type I (thylakoid type), 6 cases of type II (nodular type), and 7 cases of type III (dysplasia). All patients received detailed preoperative evaluation and underwent surgical treatment. We statistically compared the postoperative seizure outcome of different DNET MRI types by Engel classification.

RESULTS

All tumors were surgically removed and pathologically diagnosed as DNETs. The follow-up period was 5-68 months Engel class I outcome was achieved in all type I cases, 3 (50%) type II cases, and 3 (42.9%) type III cases. The postoperative seizure outcome of MRI type I was better than that of type II and III.

CONCLUSION

Based on the MRI classification of DNET by Chassoux, the postoperative epilepsy control of type I is better than that of type II and type III, which may be related to the residual FCD around the tumor of type II and type III. Thus, the MRI classification of DNET can contribute to the preoperative design of the resection plan. Total resection of type I and extended resection of type II, as well as type III, will help to improve the postoperative seizure-free rate in DNET.

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.

[Features of the neuroradiological picture of ganglioglioma on the example of 20 clinical cases]

OBJECTIVE

To analyze the images obtained during pre-surgical neuroimaging in patients with gangliomas for the presence of specific signs and verification of the neoplastic process.

MATERIAL AND METHODS

The results of presurgical MRI (3.0, 1.5 Tesla) of 20 patients with gangliomas were analyzed to identify specific signs of a neuronal-glial tumor and verify the neoplastic process based on the results obtained and a review of the literature. In addition to high-resolution MRI (HR MRI), various protocol modifications were applied to patients with epileptogenic pathological substrates of unclear etiology, including tractography (DTI) and contrast-free MR perfusion (ASL). In 5 cases, a multi-modal study was performed that combined the results of CT, routine MRI, HR MRI, functional MRI (fMRI) in various combinations and PET CT.

RESULTS AND CONCLUSION

In 17 cases, patients underwent epileptic surgery. Three patients without epilepsy were operated on for a tumor diagnosed by radiological examination. In all 20 cases, gangliogliomas were verified, including 1 anaplastic, 1 infantile desmoplastic, and another patient had histological samples showing signs of a composite tumor. Combination with FCD IIIb was observed in 3 cases. Two patients had a double pathology (cases of tumors combination with lissencephaly and neuronal heterotopia) and another had a composite neuronal-glial tumor. In 15 cases, gangliogliomas showed neuroradiological features typical for dysembryoplastic neuroepithelial tumor (DNT) such as multicystic, nodular, and diffuse (dysplastic) described in the literature. In addition, in 9 cases, they had significant signs of neoplastic process such as contrast enhancement, continued growth and remodeling of the underlying bone. Verification of the neoplastic process based on the results of neuroradiological studies was difficult in 6 cases. In 2 cases, it was not possible to confirm the presence of neoplasm by radiological methods, and in 1 patient, the verification of the tumor during differential diagnosis took more than 8 years. The most common differential diagnosis was performed with DNT and FCD type IIb, which have a number of similar neuroradiological features.

Dysembryoplastic neuroepithelial tumor presenting as a hypothalamic hamartoma in a child with gelastic seizures: case report

Dysembryoplastic neuroepithelial tumors (DNETs) are benign intracranial tumors of neuroglial origin, mostly located in the supratentorial regions and particularly in the temporal lobe. Few cases of DNETs in the hypothalamus have been described. The authors present the case of a DNET in the hypothalamus. The 5-year-old girl with complaints of limb and gelastic seizures was admitted to the neurosurgical department of Xiangya Hospital. Neurological examination findings were unremarkable. MRI showed isointensity without significant enhancement on T1- and T2-weighted images. The lesion exhibited clearly defined borders on the sagittal, coronal, and axial images. The preliminary diagnosis was hypothalamic hamartoma (HH); however, the lesion was surgically removed, and histopathological examination confirmed the diagnosis of a DNET. Hypothalamic DNETs are extremely rare. Based on their clinical manifestation and imaging, DNETs are easily misdiagnosed as HHs. Diagnoses apart from HHs must be entertained when a hypothalamic lesion is being investigated.

Surgical treatment of low-grade brain tumors associated with epilepsy

OBJECTIVE

To explore the strategy of surgical treatment of low-grade brain tumors associated with epilepsy.

METHODS

Clinical data of 158 patients with low-grade brain tumors were collected from January 2011 to December 2017 in Guangdong Sanjiu brain hospital. All patients received Preoperative evaluation. Lesion site: 18 cases were located in multiple cerebral lobes, 10 cases were in the functional zones, 130 cases were in the non-functional zones (including 74 cases were in the medial of temporal lobe). The surgical strategy included subtotal resection, gross-total resection and enlarged resection. Postoperative effects were evaluated by Engel classification.

RESULTS

A total of 158 patients underwent surgical treatment, among these patients, only 1 patient underwent intracranial electrode implantation. Surgical methods: 34 cases of subtotal resection, 3 cases of gross-total resection, 119 cases of enlarged resection (including Anterior temporal lobectomy in 74 cases) and 2 case of Selective hippocampal amygdalectomy. The final pathology suggested that there are 74 cases of ganglionglioma, 25 cases of dysembryoplastic neuroepithelial tumors, 9 cases of pilocytic astrocytoma, 16 cases of oligodendroglioma, 10 cases of pleomorphic xanthoastrocytoma, 4 case of diffuse astrocytoma, 9 cases of unclassified astrocytoma, 11 case of oligoastrocytoma. The follow-up time was between 1 and 7 years, with an average of 3.44±1.77 years. Postoperative recovery: 147 patients had an Engel Class I outcome, 10 patients were in Engel Class II, 1 patient was in Class IV.

CONCLUSION

The strategy of surgical treatment of low-grade brain tumors associated with epilepsy should pay more attention to the preoperative assessment of the epileptogenic zone. The tumor is not exactly the same as the epileptogenic zone, and the strategy of surgical treatment depends on the tumor feature as well as whether it was located in temporal lobe or involved in functional areas.

[Surgical treatment of epilepsy in children with gloneuronal brain tumors: morphology, MRI semiology and factors affecting the outcome]

INTRODUCTION

Glioneuronal tumors (GNT) are usually found in children (less than 1.5% of all neoplasms of the brain). With rare exceptions, they are benign and usually manifest only by epilepsy, which is quite often resistant to treatment with AE drugs. Tumor removal usually helps to cope with epileptic seizures, however, a number of issues regarding diagnosis and surgical treatment (interpretation of morphological data and classification, epileptogenesis and topography of the epileptogenic zone, the value of intraoperative invasive EEG and the optimal volume of resection) remain debatable.

AIM

To describe the morphology, electro-clinical picture and MR-semiology in patients with gloneuronal brain tumors, as well as to analyse the results of their surgical treatment and the factors determining its outcome.

MATERIAL AND METHODS

152 children with a median age of 8 years were treated surgically (There were 64 gangliogliomas, 73 DNT, 15 cases where the tumor classification failed - GNT NOS). In children under 2 years of age, temporal localization of the tumor prevailed. In 81 cases, ECoG was used during the operation. Surgical treatment complications: transient neurological deficit (in 15 cases); hematomas removed without consequences (in 2 cases), infectious (osteomyelitis of bone bone flap in 2 cases). We analyzed: the age of the epilepsy onset (median - 4 years 7 months) and its duration (median - 23.5 months), the type of seizures, as well as the features of MR-semiology and morphology of tumors and adjacent areas of the brain. The volume of tumor resection was verified by MRI (in 101 cases) and CT (in each case). The follow-up was collected through face-to-face meetings, with repeated video EEG and MRI, as well as telephone interviews. We studied the effect of a number of parameters characterizing the patient and features of his/her operation on the outcome of treatmen.

RESULTS

Among 102 patients in whom the follow-up history is one year or more (median - 2 years), a favorable outcome (Engel IA) was observed in 86 of them (84%); 55 of them (54%) at the time of the last examination stopped drug AE treatment. Radical tumor removal and younger age at the time of surgery were statistically significantly associated with a favorable result.

CONCLUSION

In children with gloneuronal brain tumors, removal of the tumor is effective and relatively safe in the treatment of symptomatic epilepsy. Radical tumor resection and earlier intervention are the most important prerequisites for a favorable outcome and persistent remission of seizures.

Stereoelectroencephalography: retrospective analysis of 742 procedures in a single centre

This retrospective description of a surgical series is aimed at reporting on indications, methodology, results on seizures, outcome predictors and complications from a 20-year stereoelectroencephalography (SEEG) activity performed at a single epilepsy surgery centre. Prospectively collected data from a consecutive series of 742 SEEG procedures carried out on 713 patients were reviewed and described. Long-term seizure outcome of SEEG-guided resections was defined as a binomial variable: absence (ILAE classes 1–2) or recurrence (ILAE classes 3–6) of disabling seizures. Predictors of seizure outcome were analysed by preliminary uni/bivariate analyses followed by multivariate logistic regression. Furthermore, results on seizures of these subjects were compared with those obtained in 1128 patients operated on after only non-invasive evaluation. Survival analyses were also carried out, limited to patients with a minimum follow-up of 10 years. Resective surgery has been indicated for 570 patients (79.9%). Two-hundred and seventy-nine of 470 patients operated on (59.4%) were free of disabling seizures at least 2 years after resective surgery. Negative magnetic resonance and post-surgical lesion remnant were significant risk factors for seizure recurrence, while type II focal cortical dysplasia, balloon cells, glioneuronal tumours, hippocampal sclerosis, older age at epilepsy onset and periventricular nodular heterotopy were significantly associated with seizure freedom. Twenty-five of 153 patients who underwent radio-frequency thermal coagulation (16.3%) were optimal responders. Thirteen of 742 (1.8%) procedures were complicated by unexpected events, including three (0.4%) major complications and one fatality (0.1%). In conclusion, SEEG is a safe and efficient methodology for invasive definition of the epileptogenic zone in the most challenging patients. Despite the progressive increase of MRI-negative cases, the proportion of seizure-free patients did not decrease throughout the years.

Review: Challenges in the histopathological classification of ganglioglioma and DNT: microscopic agreement studies and a preliminary genotype-phenotype analysis

Low-grade epilepsy-associated brain tumours (LEAT) are the second most common cause for drug-resistant, focal epilepsy, that is ganglioglioma (GG) and dysembryoplastic neuroepithelial tumours (DNT). However, molecular pathogenesis, risk factors for malignant progression and their frequent association with drug-resistant focal seizures remain poorly understood. This contrasts recent progress in understanding the molecular-genetic basis and targeted treatment options in diffuse gliomas. The Neuropathology Task Force of the International League Against Epilepsy examined available literature to identify common obstacles in diagnosis and research of LEAT. Analysis of 10 published tumour series from epilepsy surgery pointed to poor inter-rater agreement for the histopathology diagnosis. The Task Force tested this hypothesis using a web-based microscopy agreement study. In a series of 30 LEAT, 25 raters from 18 countries agreed in only 40% of cases. Highest discordance in microscopic diagnosis occurred between GG and DNT variants, when oligodendroglial-like cell patterns prevail, or ganglion cells were difficult to discriminate from pre-existing neurons. Suggesting new terminology or major histopathological criteria did not satisfactorily increase the yield of histopathology agreement in four consecutive trials. To this end, the Task Force applied the WHO 2016 strategy of integrating phenotype analysis with molecular-genetic data obtained from panel sequencing and 450k methylation arrays. This strategy was helpful to distinguish DNT from GG variants in all cases. The Task Force recommends, therefore, to further develop diagnostic panels for the integration of phenotype-genotype analysis in order to reliably classify the spectrum of LEAT, carefully characterize clinically meaningful entities and make better use of published literature.

Dysembryoplastic neuroepithelial tumours: clinical, radiological, pathological features and outcome

OBJECT

To analyse the clinical, imaging and histopathological data of patients who were diagnosed to have Dysembrioplastic Neuroepithelial Tumour (DNET) and underwent surgery between 1995-2015.

MATERIALS AND METHODS

Age at seizure onset, age at surgery, gender, disease duration, seizure outcome of 44 patients were analysed together with Magnetic Resonance Imaging (MRI) of 21 patients. MRI types were classified as type 1 (cystic/polycystic-like, well-delineated, strongly hypointense T1), type 2 (nodularlike,heterogeneous), type 3 (dysplastic-like, iso/hyposignal T1, poor delineation, gray-white matter blurring).

RESULTS

Histopathological classification revealed simple form in 19, complex in 14 and non-specific in 11 patients. Lobar distribution of the lesions was as follows: 21 Temporal (47.7%), 12 parietal (27.3%), 8 frontal (18.2%) and 3 occipital (6.8%). Type 1 MRI was observed in 10, type 2 was in 7, and type 3 in 4 patients on radiological evaluation. All cases with type 1 MRI corresponded to either simple or complex forms and all cases with type 3 MRI corresponded to nonspecific form. The histopathological distribution of cases with type 2 MRI was 4 as non-specific, 2 as simple, 1 as complex. There was no significant difference in the age of onset, age at operation and duration of epilepsy between the patients with different MRI subtypes. The majority of patients (N:36) had Engel I outcome (81,8%). In groups with Engel II and III outcome, duration of epilepsy was significantly higher (p:0,014) and simple form of DNET has significantly higher seizure freedom after surgery compared to complex and nonspecific forms of DNET (p:0,002).

CONCLUSION

Patients with DNET constitute a group with favorable outcomes after epilepsy surgery especially with early referral to surgery. Longer duration of epilepsy was associated with worse seizure outcome for DNET patients. There was significant correlation between radiological and histopathological types of DNET especially in type 1 and 3.

Pathology-MRI Correlations in Diffuse Low-Grade Epilepsy Associated Tumors

It is recognized that IDH mutation negative, low-grade epilepsy associated tumors (LEAT) can show diffuse growth patterns and lack the diagnostic hallmarks of either classical dysembryoplastic neuroepithelial tumors (DNT) or typical ganglioglioma. “Nonspecific or diffuse DNT” and more recently “polymorphous low-grade neuroepithelial tumor of the young” have been terms used for these entities. There are few reports on the MRI recognition of these diffuse glioneuronal tumors (dGNT), which is important in planning the extent of surgical resection. In 27 LEATs T1, T2, FLAIR, and postcontrast T1 MRI were evaluated and the pathology reviewed, including immunostaining for NeuN, CD34, MAP2, and IDH1. Each case was then independently classified by pathology or MRI as simple DNT, complex DNT, or dGNT. There was agreement in 23/27 (85%; Kappa score 0.62; p < 0.01). In 4 cases, there was discrepancy in the diagnosis of simple versus complex DNT but 100% agreement achieved for dGNT. DNT showed significantly more expansion of the cortex, cystic change and ventricle extension than dGNT. dGNT showed significantly more subcortical T2w hyperintensity and focal cortical atrophy which correlated on pathology with CD34 expression, cortical neuronal loss and white matter rarefaction. There was no distinct cortical dysplasia component identified by MRI or pathology in any case. This study highlights that dGNT can be reliably discriminated on MRI from DNT.

Prevention and management of postoperative seizures in neuro-oncology

INTRODUCTION

Epilepsy related to brain tumors is often difficult to treat and may impact the quality of life. We performed a review of current recommendations for the prevention of postoperative seizures and optimizing the anti-epileptic treatment.

MATERIAL AND METHODS

Based on studies performed since 2000 we conducted the review by (1) analyzing the incidence of tumoral epilepsy and mechanisms of epileptogenicity; (2) describing the current medical and surgical strategy according to oncologic treatments; (3) discussing the management of postoperative seizures; (4) considering the drug withdrawal after oncologic therapy.

RESULTS

Epilepsy related to supra-tentorial brain tumors is frequent (40-60%) especially in low-grade gliomas, glioneuronal tumors, fronto-temporal and eloquent cortex locations. Seizures can occur as a presenting symptom or during the course of the tumor, including after surgery and oncological treatments. Maximal safe surgical resection is the more effective therapy, alone or combined with adjuvant therapy (chemotherapy, radiotherapy). Anti-epileptic drugs are not indicated for epilepsy prophylaxis in patients without seizures but only after the first seizure due to high risk of recurrence. As they may generate adverse effects and interfere with oncological treatments, the choice is based on efficacy, tolerability and potential interactions. New anti-epileptic non-enzyme-inducing drugs are recommended in first-line monotherapy in association with adjuvant oncological therapies. Enzyme-inhibiting drugs could have a favorable effect on survival. Late seizures are often related to tumor progression or recurrence. Discontinuation of anti-epileptic drugs could be considered after successful oncological treatment and a stable medical condition.

CONCLUSION

These guidelines are helpful for a rational therapy in tumoral epilepsy.

Surgery for dysembryoplastic neuroepithelial tumors and gangliogliomas in eloquent areas. Functional results and seizure control

INTRODUCTION

Dysembryoplastic neuroepithelial tumors and gangliogliomas are developmental glioneuronal tumors usually revealed by partial epilepsy. High epileptogenicity, childhood epilepsy onset, drug-resistance, temporal location, and seizure freedom after complete resection are common characteristics of both tumors. We report the specificity of surgical management, functional results and seizure outcome in cases of a tumor location in eloquent areas.

METHODS

Among 150 patients (88 males, 3-55 years) operated on for refractory epilepsy due to a glioneuronal tumor (1990-2015), 30 (20%, dysembryoplastic neuroepithelial tumors=21; gangliogliomas=9) had a tumor located in an eloquent cortex (sensory-motor, insular or language areas). Surgery was performed after a preoperative work-up, including stereo-electroencephalography in 48 patients (26%) and functional MRI in 100 (67%). MRI-guided lesionectomy was mainly performed in extra-temporal location, whereas an additional corticectomy was performed in a temporal location. Tumor microsurgical resections were guided using neuronavigation and cortical/subcortical electrical stimulations. Multiple stereotactic thermocoagulations were performed in two insular tumors.

RESULTS

New motor/language deficits related to eloquent areas occurred postoperatively in 6/30 patients (20%) without any major permanent disability. Minor sensorimotor (n=2) and moderate language disturbance (n=1) persisted in three of them. Postoperative seizure-free outcome (mean follow-up>5 years) was obtained in 81% of the entire series, but significantly decreased to 60% in eloquent areas. Incomplete tumor resection was the main cause of surgical failure. However, unfavorable seizure outcome was also observed despite complete tumor resection. Malignant transformation occurred in one ganglioglioma.

CONCLUSION

Epilepsy surgery for benign glioneuronal tumors in eloquent areas provides acceptable results regarding the functional risks. Complete tumor resection is crucial for long-term favorable outcome.

Comprehensive preoperative work-up and surgical treatment of low grade tumor/benign lesion related temporal lobe epilepsy

OBJECTIVE

Generally low-grade tumor/benign lesion related temporal lobe epilepsy (LGT/BL-TLE) is considered easier to treat and has better prognosis when compared to non-lesional TLE. However, multiple disputes exist in surgical management of this epilepsy entity. This study aims to discuss comprehensive preoperative work-up, surgical strategies and outcome of it.

METHODS

A retrospective review of sixty LGT/BL-TLE cases which underwent comprehensive preoperative work-up and then resective surgeries was conducted. Surgical strategies were categorized into limited and expanded resections. Surgical efficacy was evaluated using Engel grading after telephone or clinic follow-up and compared statistically.

RESULTS

Preoperative work-up includes magnetic resonance imaging (MRI), conventional electroencephalography, semiology evaluation, positron emission tomography (PET) and 256-channel dense-array electroencephalography source imaging (256-ch dESI). In aspect of concordance with epileptic lesions demonstrated on MRI, 256-ch dESI was more accurate than PET (72.7% vs. 39.4%) (p<0.05). Limited resections were performed in 28 cases while expanded resections in 32 cases. Altogether the surgical efficacy was: Engel grade I 86.7%, I+II 95.0%. Comparison of surgical outcome showed neither the outcome between limited and expanded resection nor the outcome between mesial and neocortical TLE (mTLE & nTLE) undergoing limited resections was significantly different (p>0.05).

CONCLUSIONS

For LGT/BL-TLE, most surgical strategies can be made preoperatively after comprehensive work-up rather than intraoperatively. Limited and expanded strategies yield similar surgical outcome in either nTLE or mTLE as long as comprehensive work-up supports the strategy and the epileptic lesion is totally removed. 256-ch dESI which can visualize both structural and electrophysiological lesions may be contributable to surgical planning of this entity.

A rare case of dysembryoplastic neuroepithelial tumor combined with encephalocraniocutaneous lipomatosis and intractable seizures

Encephalocraniocutaneous lipomatosis (ECCL) is a rare neurocutaneous syndrome that affects ectomesodermal tissues (skin, eyes, adipose tissue, and brain). The neurologic manifestations associated with ECCL are various including seizures. However, ECCL patients very rarely develop brain tumors that originate from the neuroepithelium. This is the first described case of ECCL in combination with dysembryoplastic neuroepithelial tumor (DNET) that presented with intractable seizures. A 7-year-old girl was admitted to our center because of ECCL and associated uncontrolled seizures. She was born with right anophthalmia and lipomatosis in the right temporal area and endured right temporal lipoma excision at 3 years of age. Seizures began when she was 3 years old, but did not respond to multiple antiepileptic drugs. Brain magnetic resonance (MR) imaging performed at 8 and 10 years of age revealed an interval increase of multifocal hyperintense lesions in the basal ganglia, thalamus, cerebellum, periventricular white matter, and, especially, the right temporal area. A nodular mass near the right hippocampus demonstrated the absence of N-acetylaspartate decrease on brain MR spectroscopy and mildly increased methionine uptake on brain positron emission tomography, suggesting low-grade tumor. Twenty-four-hour video electroencephalographic monitoring also indicated seizures originating from the right temporal area. Right temporal lobectomy was performed without complications, and the nodular lesion was pathologically identified as DNET. The patient has been seizure-free for 14 months since surgery. Although ECCL-associated brain tumors are very rare, careful follow-up imaging and surgical resection is recommended for patients with intractable seizures.

BRAF V600E mutation in epilepsy-associated glioneuronal tumors: Prevalence and correlation with clinical features in a Chinese population

PURPOSE

Glioneuronal tumors (GNTs) are the most common histological type of brain tumors in patients who received epilepsy surgery, and part of them presented with BRAF V600E mutation. We aimed to verify the presence of the BRAF V600E mutation in epilepsy-associated GNTs from Chinese population and evaluate the association with clinical features.

METHODS

Data from 35 patients diagnosed with GNTs, including 24 gangliogliomas and 11 dysembryoplastic neuroepithelial tumors, were retrospectively collected. DNA was extracted from GNTs tissues and BRAF V600E mutation was examined by DNA sequencing. The correlations between BRAF V600E mutation and clinical features were analyzed.

RESULTS

Totally, BRAF V600E mutations were detected in 11 patients with GNTs, the rate of mutation were 33.3% and 27.3% in GGs (8/24) and DNTs (3/11), respectively. The probability of BRAF V600E mutation in females (7/12, 58.3%) was significantly higher than that in males (4/23, 17.4%) (P=0.022). Moreover, patients with BRAF-mutated GNTs had a significantly wider variety of seizure types compared to GNTs with BRAF wild-type status (P=0.027). However, no significant correlation between the BRAF status and certain clinical features, such as age of seizure onset, duration of epilepsy, age at surgery, location of the tumor and postoperative seizure free, were observed.

CONCLUSION

We demonstrated the presence of BRAF V600E mutation in Chinese epileptic patients with GNTs, which was significantly correlated with gender and multiple seizure types. Large sample studies and long-term follow-up are required for further confirmation.

Seizure-onset patterns in focal cortical dysplasia and neurodevelopmental tumors: Relationship with surgical prognosis and neuropathologic subtypes

OBJECTIVES

The study of intracerebral electroencephalography (EEG) seizure-onset patterns is crucial to accurately define the epileptogenic zone and guide successful surgical resection. It also raises important pathophysiologic issues concerning mechanisms of seizure generation. Until now, several seizure-onset patterns have been described using distinct recording methods (subdural, depth electrode), mostly in temporal lobe epilepsies or with heterogeneous neocortical lesions.

METHODS

We analyzed data from a cohort of 53 consecutive patients explored by stereoelectroencephalography (SEEG) and with pathologically confirmed malformation of cortical development (MCD; including focal cortical dysplasia [FCD] and neurodevelopmental tumors [NDTs]).

RESULTS

We identified six seizure-onset patterns using visual and time-frequency analysis: low-voltage fast activity (LVFA); preictal spiking followed by LVFA; burst of polyspikes followed by LVFA; slow wave/DC shift followed by LVFA; theta/alpha sharp waves; and rhythmic spikes/spike-waves. We found a high prevalence of patterns that included LVFA (83%), indicating nevertheless that LVFA is not a constant characteristic of seizure onset. An association between seizure-onset patterns and histologic types was found (p = 001). The more prevalent patterns were as follows: (1) in FCD type I LVFA (23.1%) and slow wave/baseline shift followed by LVFA (15.4%); (2) in FCD type II burst of polyspikes followed by LVFA (31%), LVFA (27.6%), and preictal spiking followed by LVFA (27.6%); (3) in NDT, LVFA (54.5%). We found that a seizure-onset pattern that included LVFA was associated with favorable postsurgical outcome, but the completeness of the EZ resection was the sole independent predictive variable.

SIGNIFICANCE

Six different seizure-onset patterns can be described in FCD and NDT. Better postsurgical outcome is associated with patterns that incorporate LVFA.

Lesional cerebellar epilepsy: a review of the evidence

Classical teaching in epileptology localizes the origins of focal seizures solely in the cerebral cortex, with only inhibitory effects attributed to subcortical structures. However, electrophysiological and neuroimaging studies over the last decades now provide evidence for an initiation of epileptic seizures within subcortical structures. Intrinsic epileptogenicity of hypothalamic hamartoma has already been established in recognition of subcortical epilepsy, whereas a seizure-generating impact of dysplastic cerebellar lesions remains to be clarified. Herein, we examine the supportive evidence and clinical presentation of cerebellar seizures and review therapy options.

Review of seizure outcomes after surgical resection of dysembryoplastic neuroepithelial tumors

Dysembryoplastic neuroepithelial tumors (DNETs) are rare tumors that present with seizures in the majority of cases. We report the results of a review of seizure freedom rates following resection of these benign lesions. We searched the English literature using PubMed for articles presenting seizure freedom rates for DNETs as a unique entity. Patient demographics, tumor characteristics, and operative variables were assessed across selected studies. Twenty-nine articles were included in the analysis. The mean age at surgery across studies was a median of 18 years (interquartile range 11-25 years). The mean duration of epilepsy pre-operatively was a median 7 years (interquartile range 3-11 years). Median reported gross-total resection rate across studies was 79% (interquartile range 62-92%). Authors variously chose lesionectomy or extended lesionectomy operations within and across studies. The median seizure freedom rate was 86% (interquartile range 77-93%) with only one study reporting fewer than 60% of patients seizure free. Seizure outcomes were either reported at 1 year of follow-up or at last follow-up, which occurred at a median of 4 years (interquartile range 3-7 years). The number of seizure-free patients who discontinued anti-epileptic drugs varied widely from zero to all patients. Greater extent of resection was associated with seizure freedom in four studies.

Dysembryoplastic Neuroepithelial Tumors

Dysembryoplastic neuroepithelial tumor (DNT) is a benign glioneuronal neoplasm that most commonly occurs in children and young adults and may present with medically intractable, chronic seizures. Radiologically, this tumor is characterized by a cortical topography and lack of mass effect or perilesional edema. Partial complex seizures are the most common presentation. Three histologic subtypes of DNTs have been described. Histologically, the recognition of a unique, specific glioneuronal element in brain tumor samples from patients with medically intractable, chronic epilepsy serves as a diagnostic feature for complex or simple DNT types. However, nonspecific DNT has diagnostic difficulty because its histology is indistinguishable from conventional gliomas and because a specific glioneuronal element and/or multinodularity are absent. This review will focus on the clinical, radiographic, histopathological, and immunohistochemical features as well as the molecular genetics of all three variants of DNTs. The histological and cytological differential diagnoses for this lesion, especially the nonspecific variant, will be discussed.

Resection of a dysembryoplastic neuroepithelial tumor in the precentral gyrus

BACKGROUND

Dysembryoplastic neuroepithelial tumors (DNTs) are common causes of intractable epilepsy in pediatric epilepsy patients. The effect of surgical intervention is often limited when the tumor is located in the precentral gyrus. Furthermore, complete surgical resection is often not performed in order to avoid permanent neurological deficits.

METHODS

Here, we present a pediatric patient with intractable epilepsy caused by a simple DNT located in the precentral gyrus. Intracranial electrodes were implanted and used in combination with magnetic resonance imaging, video-electroencephalography and electrical cortical stimulation to assess neurological function, and where the epileptogenic zone was located.

RESULTS

The results of intracranial electrode monitoring suggested that the epileptogenic zone was located in the tumor area and that cortical function had been reorganized. We completely resected the tumor based on these findings. The patient has been seizure free after the surgery and has not had any neurological deficits.

CONCLUSIONS

Simple form DNTs in the precentral gyrus can be completely resected with careful preoperative assessment of cortical function. Cortical reorganization could partly explain the functional preservation after surgery.

Epilepsy surgery for glioneuronal tumors in childhood: avoid loss of time

BACKGROUND

In contrast to the abundance of seizure outcome reports in epilepsy surgery for glioneuronal tumors in childhood and adolescence, there is a dearth of information regarding cognitive outcomes.

OBJECTIVE

To investigate the seizure and cognitive outcome of children and adolescents that underwent resective surgery for glioneuronal tumor-associated refractory epilepsy and determine their predictive factors.

METHODS

We retrospectively analyzed the presurgical findings, resection types, and outcomes over 1.3 to 12.3 years (mean, 7.3) of 29 consecutive patients, who underwent resection in 2000 to 2011. The mean age at epilepsy onset was 7.9 years (range, 0-15.4), the mean age at surgery was 11.7 years (range, 2.6-17.3), and the mean epilepsy duration to surgery was 3.8 years (range, 0.3-15.3). Etiology comprised 13 dysembryoplastic neuroepithelial tumors and 16 gangliogliomas, with additional focal cortical dysplasia in 5 cases.

RESULTS

Eighty-six percent of children were seizure free 12 months after surgery; at final follow-up, 76% remained seizure free and 62% had discontinued antiepileptic drugs. Gross total resection was related to significantly higher rates of seizure freedom. Higher presurgical cognitive functioning (full-scale IQ, verbal IQ) was related to shorter epilepsy duration to surgery independent of age at epilepsy onset, thus determining postsurgical functioning. Improvements in verbal IQ, performance IQ, and visual memory as well as a trend toward improvement in full-scale IQ were established after surgery. Despite individual losses in full-scale IQ, verbal or visual memory, no deterioration was noted in any cognitive variable on a group level.

CONCLUSION

Completeness of resection predisposes to favorable outcomes regarding seizure alleviation. Whereas cognitive functioning deteriorates with time in glioneuronal tumor-related refractory epilepsy, surgery is linked to improvement rather than to deterioration on a group level.

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.

Cerebral cavernous malformations in the setting of focal epilepsies: pathological findings, clinical characteristics, and surgical treatment principles

Cavernous cerebral malformations (CCMs) are a well-defined epilepsy-associated pathology. They represent lesions/conglomerates of abnormally configured vessels leading to seizures either as a result of physiological changes affecting the cerebral cortex immediately surrounding the CCM (an epileptogenic mechanism that is relevant for both temporal and extratemporal lesions), or as a result of promoting epileptogenicity in remote but anatomo-functionally connected brain regions (a mechanism that is particularly relevant for temporal lobe lesions). This review details the pathological findings in CCMs and discusses the mechanisms of epileptogenicity in this context. The bulk of the review will focus on therapeutic strategies. Medical therapy using antiepileptic drugs is recommended as a first-line therapy, but surgical removal of the CCM with the surrounding cortex should be pursued if seizures prove to be drug resistant. Early timing of the resection and complete removal of any associated epileptic pathology are critical for best outcomes. In addition to reviewing the available data from prior series, we present original research from two specialized epilepsy centers targeted at answering particularly pressing clinical questions mainly related to the ideal timing and extent of surgery. Further research is needed to define the best surgical strategies in patients with temporal lobe CCMs and structurally normal hippocampi.

A neuropathology-based approach to epilepsy surgery in brain tumors and proposal for a new terminology use for long-term epilepsy-associated brain tumors

Every fourth patient submitted to epilepsy surgery suffers from a brain tumor. Microscopically, these neoplasms present with a wide-ranging spectrum of glial or glio-neuronal tumor subtypes. Gangliogliomas (GG) and dysembryoplastic neuroepithelial tumors (DNTs) are the most frequently recognized entities accounting for 65 % of 1,551 tumors collected at the European Epilepsy Brain Bank (n = 5,842 epilepsy surgery samples). These tumors often present with early seizure onset at a mean age of 16.5 years, with 77 % of neoplasms affecting the temporal lobe. Relapse and malignant progression are rare events in this particular group of brain tumors. Surgical resection should be regarded, therefore, also as important treatment strategy to prevent epilepsy progression as well as seizure- and medication-related comorbidities. The characteristic clinical presentation and broad histopathological spectrum of these highly epileptogenic brain tumors will herein be classified as “long-term epilepsy associated tumors—LEATs”. LEATs differ from most other brain tumors by early onset of spontaneous seizures, and conceptually are regarded as developmental tumors to explain their pleomorphic microscopic appearance and frequent association with Focal Cortical Dysplasia Type IIIb. However, the broad neuropathologic spectrum and lack of reliable histopathological signatures make these tumors difficult to classify using the WHO system of brain tumors. As another consequence from poor agreement in published LEAT series, molecular diagnostic data remain ambiguous. Availability of surgical tissue specimens from patients which have been well characterized during their presurgical evaluation should open the possibility to systematically address the origin and epileptogenicity of LEATs, and will be further discussed herein. As a conclusion, the authors propose a novel A–B–C terminology of epileptogenic brain tumors (“epileptomas”) which hopefully promote the discussion between neuropathologists, neurooncologists and epileptologists. It must be our future mission to achieve international consensus for the clinico-pathological classification of LEATs that would also involve World Health Organization (WHO) and the International League against Epilepsy (ILAE).

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.

Developmental tumors and adjacent cortical dysplasia: single or dual pathology?

Developmental tumors often lead to refractory partial seizures and constitute a well-defined, surgically remediable epilepsy syndrome. Dysplastic features are often associated with these tumors, and their significance carries both practical and conceptual relevance. If associated focal cortical dysplasia (FCD) relates to the extent of the epileptogenic tissue, then presurgical evaluation and surgical strategies should target both the tumor and the surrounding dyslaminated cortex. Furthermore, the association has been included in the recently revised classification of FCD and the epileptogenicity of this associated dysplastic tissue is crucial to validate such revision. In addition to the possibility of representing dual pathology, the association of developmental tumors and adjacent dysplasia may instead represent a single developmental lesion with distinct parts distributed along a histopathologic continuum. Moreover, the possibility that this adjacent dyslamination is of minor epileptogenic relevance should also be entertained. Surgical data show that complete resection of the solid tumors and immediately adjacent tissue harboring satellites may disrupt epileptogenic networks and lead to high rates of seizure freedom, challenging the epileptogenic relevance of more extensive adjacent dyslaminated cortex. Whether the latter is a primary or secondary abnormality and whether dyslaminated cortex in the context of a second lesion may produce seizures after complete resection of the main lesion is still to be proven.

Dysembryoplastic neuroepithelial tumors: where are we now?

Dysembryoplastic neuroepithelial tumors (DNTs) belong to the surgically treatable long-term epilepsy-associated group of tumors. Based on cortical specimens provided through epilepsy surgery at Sainte-Anne hospital, three histologic subtypes (simple, complex, and nonspecific) have been described. Electroclinical data, imaging, intralesional recordings (stereo-electroencephalography [EEG]) and histologic correlations have been recently reviewed in order to assess the relationship between the epileptogenic zone (EZ), the tumor, and associated focal cortical dysplasia (FCD), and to determine optimal strategy for curing epilepsy. Based on a large series (78 patients, 50 male, aged 3-54 years, temporal location 73%, nonspecific forms 68%), we found similar electroclinical data in all DNT subtypes, and demonstrated that magnetic resonance imaging (MRI) features allow differentiation of histologic subtypes. Type 1 (cystic/polycystic-like) always corresponded to complex or simple forms, whereas type 2 (nodular-like) and type 3 (dysplastic-like) corresponded to nonspecific forms. It is notable that we demonstrated intrinsic epileptogenicity in all cases, but found that the EZ differed significantly according to MRI subtype, colocalizing with the tumor in type 1 MRI, including perilesional cortex in type 2 MRI, and involving extensive areas in type 3 MRI. The main prognostic factors for favorable outcome (83% of seizure-free patients) were complete tumor and EZ removal, short epilepsy duration, and lack of cortico-subcortical damage. According to these findings, surgical resection may be restricted to the tumor in type 1 MRI but should be more extensive in other MRI subtypes, especially in type 3 MRI. This MRI-based scheme may be helpful for optimal resection in epilepsy due to DNTs. In addition, we emphasize that early surgery is crucial in curing epilepsy.

Dysembryoplastic neuroepithelial tumors: a model for examining the effects of pathology versus seizures on cognitive dysfunction in epilepsy

PURPOSE

Dysembryoplastic neuroepithelial tumors (DNTs) provide a unique model for studying the effects of seizures on cognitive development. Epilepsy and antiepileptic medications are prominent features in the lives and schooling of people who develop seizures in childhood. People with an adult onset share the same underlying brain pathology, but their childhood development is unaffected by seizures. Therefore, DNTs provide a model to examine the specific influence of seizures and their treatment on cognitive development, over and above the effects of the underlying pathology in epilepsy.

METHODS

We examined the neuropsychological characteristics of 56 adults with DNT and medically intractable epilepsy (mean age 32.7 years). Twenty-two adults (39%) had an age of onset of epilepsy before the age of 12 years (childhood-onset group). Scores on tests of intelligence (Verbal IQ and Performance IQ), reading, working memory, verbal learning, verbal recall, visual learning, and expressive and receptive language ability were analyzed.

KEY FINDINGS

There were no significant localization effects (right vs. left vs. extratemporal) on any of the neuropsychological test scores. In the group as a whole, the neuropsychological test scores were significantly lower than healthy, age-matched controls on measures of Verbal IQ (p < 0.01), naming p < 0.01, verbal learning (p < 0.01), and working memory (p < 0.05). The childhood-onset group had significantly lower scores on the measures of Verbal IQ (p < 0.01), Performance IQ (p < 0.05), reading (p < 0.05), naming (p = 0.05), and verbal retention (p < 0.05) than those with an onset of seizures at the age of 12 or older.

SIGNIFICANCE

The traditional pattern of lateralized memory deficits seen in people with hippocampal sclerosis may not be present in people with temporal lobe epilepsy associated with a DNT. The presence of seizures and their treatment in early childhood may adversely influence the development of these core cognitive abilities, resulting in patterns of cognitive deficits that remain apparent in adulthood.