Various findings in surgically treated epilepsy patients with dysembryoplastic neuroepithelial tumors in comparison with those of patients with other low-grade brain tumors and other neuronal migration disorders

Dysembryoplastic Neuroepithelial Tumors: What You Need to Know

OBJECTIVE

An updated and comprehensive review on dysembryoplastic neuroepithelial tumor (DNET) focusing on differential diagnosis, atypical presentation, seizure outcome, and risk of malignant transformation.

METHODS

A PubMed/MEDLINE-based literature search has been performed using "dysembryoplastic neuroepithelial tumor" as a keyword. Two treated cases characterized by an atypical presentation have been reviewed.

RESULTS

Of 1162 articles, 200 relevant studies have been selected. DNET is a benign mixed neuronal-glial tumor causing drug-resistant epilepsy primarily in children and young adults. The typical radiological pattern is a magnetic resonance imaging (MRI) T1-hypointense, T2-, and fluid-attenuated inversion-recovery hyperintense multicystic lesion involving the cerebral cortex with no edema. Contrast enhancement may be present and a focal cortical dysplasia is commonly associated with it. MRI diffusion, perfusion, and spectroscopy have a paramount role in the differential diagnosis. The "specific glioneuronal elements" are pathognomonic. They are positive for S100 protein, synaptofisin, neuronal nuclei, oligodendrocyte transcription factor, neurite outgrowth inhibitor, and microtubule-associated protein 2, but negative for glial fibrillary acidic protein. As opposed to v-myb avian myeloblastosis viral oncogene homolog, isocitrate dehydrogenase-1/isocitrate dehydrogenase-2 mutation and codeletion 1p-19q, fibroblast growth factor receptor 1 and BRAF V600E mutations are present. The effectiveness of surgery on seizure outcome has been established. Rare malignant transformations have been reported, especially in extra-temporal and complex forms.

CONCLUSIONS

Advanced MRI techniques are fundamental in the differential diagnosis for DNET versus other low-grade gliomas. Immuno-phenotype assessment and search for fibroblast growth factor receptor 1 and BRAF V600E mutations limit the risk of misdiagnoses. A gross total tumor removal is generally associated with a seizure-free outcome. Recurrences and malignant transformations may rarely follow, legitimizing MRI surveillance in cases of subtotal tumor resection.

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.

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.

Seizures in children with dysembryoplastic neuroepithelial tumors of the brain--A review of surgical outcomes across several studies

PURPOSE

In children and adolescents, dysembryoplastic neuroepithelial tumors (DNETs) of the brain present with seizures almost 100% of the time, potentially creating significant long-term morbidity and disability despite the generally indolent course of the lesion. These tumors also tend to be quite resistant to anti-epileptic drugs which, themselves, can be associated with long-term side effects and resultant disability. Many clinicians advocate early surgical resection of these lesions, but how effective this approach is, and how aggressive tumor removal should be, continues to be debated.

METHODS

We performed a systematic review of the relevant literature to identify all reports of DNET resections in pediatric patients published over the past 20 years. In all, over 3000 MEDLINE abstracts were reviewed, ultimately resulting in 13 studies with 185 pediatric DNET patients to review.

RESULTS

Surgical resection of the lesion was effective at improving seizures in over 98% of patients and at achieving long-term seizure freedom in 86%. Surgical resection of DNETs also appeared to be quite safe, with no reported perioperative deaths and an overall rate of postoperative complications of 12%; the vast majority of these complications were transient.

CONCLUSIONS

Total gross resection of the lesion was the only factor statistically correlated with long-term seizure freedom (r = 0.63, p = 0.03). However, data remain lacking regarding whether this translates into more extensive procedures-like brain mapping and partial lobectomies-being any more effective than simple lesionectomies alone. Further research is clearly needed to address this and other crucial questions.

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: epileptogenicity related to histologic subtypes

OBJECTIVE

To analyze the electroclinical features and the relationship between the epileptogenic zone (EZ), the tumor and focal cortical dysplasia (FCD) in the three histologic subtypes of dysembryoplastic neuroepithelial tumors (DNTs) ("simple", "complex" and "non-specific forms").

METHODS

We analyzed electroclinical data from 78 patients (50 males; 3-54 years) operated for intractable epilepsy due to a DNT. We compared EZ extent, defined by stereo-electroencephalography (n = 33), with the tumor and FCD areas, in each DNT subtype.

RESULTS

Non-specific forms (68%) and temporal location were predominant (73%). The main characteristics consisted of late childhood epilepsy onset (median 12 years), drug-resistant partial seizures and EEG abnormalities concordant with tumor location. In all DNT subtypes, intrinsic epileptogenicity was demonstrated by intralesional recordings (n = 30), displaying a depressed background activity interrupted by rapid spikes or polyspikes. EZ co-localized with the tumor in all simple and complex DNTs, but in only 1/3 of non-specific DNTs. The main discordance between the EZ and tumor extent was found in temporal non-specific DNTs associated with extensive FCD.

CONCLUSION

These results are helpful when planning surgery for DNTs.

SIGNIFICANCE

Intrinsic epileptogenicity characterizes all DNTs; however, the EZ differs according to histologic subtypes and is particularly widespread in non-specific temporal forms.

Systematic review and case series of neuropsychological functioning after epilepsy surgery in children with dysembryoplastic neuroepithelial tumors (DNET)

RATIONALE

The purposes of this study were to 1) conduct a review of neuropsychological (NP) outcomes after epilepsy surgery for DNET and 2) present pre/post-surgical NP results from a series of children with DNET.

METHODS

First, a systematic literature review was conducted with specific inclusion criteria. Second, a review of DNET surgical patients seen at two tertiary-care hospitals using reliable change methods of NP functioning was conducted.

RESULTS

Of 300 citations retrieved, 7 studies met criteria. Studies reported low average to average pre-surgical IQ. Engel Class I outcome was approximately 85%.

CASE SERIES

Thirteen children completed pre/post-surgical NP assessments. Pre-surgically, children demonstrated low average to average functioning. Post-surgically, few patients showed reliable change. One-third of children demonstrated psychological improvement.

CONCLUSIONS

NP outcome following DNET has not been well-described. Children with DNET demonstrate low average to average NP functioning pre-surgically, good seizure outcome, and stable NP functioning post-surgically.

Dysembryoplastic neuroepithelial tumors: a prospective clinicopathologic and outcome study of 13 children

Dysembryoplastic neuroepithelial tumors (DNETs) are benign intracortical masses that are typically observed in children and young adults and are classified as glioneuronal tumors (WHO grade I). Large and retrospective series of patients with DNETs have been reported, but prospective studies on pediatric cohorts of patients with DNETs have been lacking. In the present study, 13 children (8 boys, 5 girls; age 8-18 years) who had simple (n = 2) or complex (n = 11) partial seizures (seizure duration range, 2-4 years; mean, 1.5 years; mode, 1.2 years) were prospectively enrolled and monitored over 13 years. The DNETs were located in the frontal (n = 2), temporal (n = 9), or occipital (n = 2) cortex. In 11/13 cases, the seizures were resistant to drug therapy, and all the children had surgery consisting of extended lesionectomy coupled with neuronavigation. Pathology examination revealed cortical dysplasia (n = 8), glial nodules (n = 11), calcification (n = 4), cellular atypia (n = 3), endothelial proliferation (n = 1), perivascular inflammation (n = 3), and meningeal involvement (n = 6). All children were seizure free throughout postsurgical follow-up of 2-11 years. This first prospective study with follow-up monitoring of a childhood population with DNETs confirms, on a long-term basis, that the coupled strategy of extended lesionectomy and neuronavigation has good outcome for long-term seizure control.

Local and remote epileptogenicity in focal cortical dysplasias and neurodevelopmental tumours

During the pre-surgical evaluation of drug-resistant epilepsy, the assessment of the extent of the epileptogenic zone and its organization is a crucial objective. Indeed, the epileptogenic zone may be organized as a simple focal lesional site or as a more complex network (often referred to as the 'epileptogenic network') extending beyond the lesion. This distinction is particularly relevant in developmental lesions such as focal cortical dysplasias or dysembryoplastic neuroepithelial tumours and may determine both the surgical strategy and the prognosis. In this study, we have quantified the epileptogenic characteristic of brain structures explored by depth electrodes in 36 patients investigated by stereoelectroencephalography and suffering from focal drug-resistant epilepsy associated with focal cortical dysplasias or dysembryoplastic neuroepithelial tumours. This quantification was performed using the 'Epileptogenicity Index' method that accounts for both the propensity of a brain area to generate rapid discharges and the time for this area to get involved in the seizure. Epileptogenicity Index values range from 0 (no epileptogenicity) to 1 (maximal epileptogenicity). We determined Epileptogenicity Index from signals recorded in distinct brain structures including the lesional site. We studied the type of epileptogenic zone organization (focal versus network) and looked for a correlation with clinical data and post-surgical outcome. Mean Epileptogenicity Index in lesional regions was 0.87 (+/-0.25), and 0.29 (+/-0.30) in 'non-lesional' structures. The number of highly epileptogenic structures (defined by Epileptogenicity Index value >or=0.4) was 3.14 (+/-1.87) in the whole population. We found that 31% of patients had only one epileptogenic structure (N(EI>or=0.4) = 1), therefore disclosing a strictly focal epileptogenic zone organization while 25 patients had more than one epileptogenic region, disclosing a network (61%) or bilateral (8%) epileptogenic zone organization. We observed a trend for a difference in seizure outcome according to the type of epileptogenic zone organization. Indeed, 57% of patients with network organization and 87% with focal organization were seizure-free while none of those with bilateral organization became seizure-free. The determination of Epileptogenicity Index computed from electrophysiological signals recorded according to the stereoelectroencephalography technique is a novel tool. Results suggest that it can help in the delineation of the epileptogenic zone associated with brain lesions and that it could be used in the definition of the subsequent surgical resection.

The Children's Cancer and Leukaemia Group guidelines for the diagnosis and management of dysembryoplastic neuroepithelial tumours

Dysembryoplastic neuroepithelial tumours (DNETs) were incorporated into the new World Health Organization classification of brain tumours as part of the group of glioneuronal tumours in 1993. Large series of patients with DNETs and pharmaco-resistant epilepsy have been reported. DNETs are most often located in the temporal lobe, occurring in both mesial and lateral temporal locations. DNETs have also been reported in the insular cortex, brain stem, cerebellum, occipital lobe and striatum. Approximately 40% of DNETs are cystic, and solitary nodular, multinodular or diffuse forms have been recognized. Approximately 30% of DNETs are associated with subtle cortical dysplastic changes in the adjacent cortex. DNET nodules usually look like oligodendroglioma, whilst between the nodules it may be possible to recognize vertical columns of neurons surrounded by oligodendrocyte-like cells. Cytologically, oligodendroglial-like cells of DNETs are distinguished from oligodendroglioma by larger nuclei with frequent nuclear indentations and multiple, small nucleoli, whilst oligodendrogliomas consistently show nuclear roundness with one or two occasional nucleoli. Very rare cases of malignant transformation have been reported. DNETs are hypodense on CT and demonstrate decreased signal on the T1-weighted images and a hyper-intense signal on T2-weighted MRI. DNETs associated with pharmaco-resistant epilepsy should be removed early to achieve seizure freedom and prevent tumour progression. The surgical approach should be that of an extended lesionectomy, i.e. excision of the lesion and the abnormal dysplastic cortex around it. Use of MRI-based image guidance (neuronavigation) as a surgical tool to identify this area of abnormal cortex is very helpful to ensure that the extended lesionectomy includes any visibly dysplastic cortex. It is not advocated to use a stereotactic biopsy only, as this may generate an unrepresentative tissue sample consisting of an oligodendroglial component only and may lead to an incorrect diagnosis.

Seizure outcome after surgery for epilepsy due to focal cortical dysplastic lesions

Neocortical development is a highly complex process encompassing cellular proliferation, neuronal migration and cortical organization. At any time this process can be interrupted or modified by genetic or acquired factors causing malformations of cortical development (MCD). Epileptic seizures are the most common type of clinical manifestation, besides developmental delay and focal neurological deficits. Seizures due to MCD are frequently pharmacoresistant, especially those associated to focal cortical dysplasia (FCD). Surgical therapy results have been reported since 1971, however, currently available data from surgical series are still limited, mainly due to small number of patients, distinct selection of candidates and surgical strategies, variable pathological diagnosis and inadequate follow-up. This study addresses the possibilities of seizure relief following resection of focal cortical dysplasia, and the impact of presurgical evaluation, extent of resection and pathological findings on surgical outcome. We included 41 patients, 22 adults and 19 children and adolescents, with medically intractable seizures operated on from 1996 to 2002. All were submitted to standardized presurgical evaluation including high-resolution MRI, Video-EEG monitoring and ictal SPECT. Post-surgical seizure outcome was classified according to Engel's schema. Univariate and multivariate analysis were performed. Fifteen patients had temporal and 26 extratemporal epilepsies. Of the total 26 patients (63.4%) reached seizure-free status post-operatively. There was no correlation between outcome and age at surgery, duration of epilepsy, frequency of seizures, and pathological findings. There was, however, a clear correlation with topography of FCD (temporal versus extratemporal) and regional ictal EEG onset, on univariate as well as multivariate analysis.

Long-term seizure outcome following surgery for dysembryoplastic neuroepithelial tumor

OBJECT

Resection of dysembryoplastic neuroepithelial tumor (DNET) is thought to result in favorable seizure outcome, but long-term follow-up data are scarce. The authors present a review of 18 patients who underwent surgical removal of a DNET: 12 via temporal lobectomy and six via lesionectomy.

METHODS

The mean long-term follow up was 10.8 years (median 10.4 years, range 7.8 to 14.8 years), and results obtained during this time period were compared with previously reported short-term (mean 2.7 years) seizure outcome data. In the current study, 66.7% patients had an Engel Class I outcome and 55.6% had an Engel Class IA outcome compared with 77.8% and 55.6%, respectively. Temporal lobectomy (Engel Class I, 83.3%; Engel Class IA, 66.7%) led to a better seizure outcome than lesionectomy (Engel Classes I and IA, 33.3%). Two patients (11.1%) required repeated operation and both had an incomplete lesionectomy initially.

CONCLUSIONS

Results indicated that complete resection of a DNET leads to a favorable seizure outcome, with epilepsy cure in those who had experienced early postoperative seizure relief. Long-term seizure outcome after surgery is predictable based on the result of short-term follow up.

Correlation of transcriptome profile with electrical activity in temporal lobe epilepsy

The biology underlying epileptic brain activity in humans is not well understood and likely depends on changes in gene expression. We performed a microarray transcriptome profiling of 12 anterolateral temporal cortical samples originating from five individuals who suffered with temporal lobe epilepsy for at least 10 years. Prior to partial lobectomy, intraoperative electrocorticography was performed on the cortical surface of each patient. These recordings showed characteristic differences in frequency and amplitude that were defined as "spiking" (abnormal) or "non-spiking" (normal). Between the transcriptome of the two sample groups, transferrin (TF) was the most differentially expressed gene. Furthermore, gene expression profiling also revealed a downregulation of multiple GABA system-related genes (GABRA5, GABRB3, ABAT) in the spiking samples and an upregulation of oligodendrocyte and lipid metabolism transcripts (MOG, CA2, CNP, SCD, PLP1, FA2H, ABCA2). In addition, several transcripts related to the classical MAPK cascade showed expression level alterations between the spiking and non-spiking samples (G3BP2, MAPK1, PRKAR1A, and MAP4K4). Out of 12 genes chosen for verification by RT qPCR, 9 showed significant expression changes in the microarray-predicted direction. Furthermore, the microarray and qPCR data were highly correlated (r = 0.98; P < 0.001). We conclude that abnormal electrical brain activity in the spiking samples is strongly correlated with gene expression changes and we speculate that some of the observed transcriptome changes may be directly involved in the induction or prevention of the ictal events seen in epilepsy.

Neurosurgical treatment of brain tumors in children

Primary brain tumors are the most common solid neoplasms of childhood. The diagnosis of brain tumors in the general pediatric population remains challenging. Nevertheless, it is clear that refinements in imaging, surgical technique, and adjunctive therapies have led to longer survival and an improving quality of life in children with brain tumors.