Low-grade gliomas of chronic epilepsy: a distinct clinical and pathological entity

Prediagnosis epilepsy and survival in patients with glioma: a nationwide population-based cohort study from 2009 to 2018

OBJECTIVE

Considering that epilepsy is common, and knowledge is lacking on its role especially for the prognosis of high-grade gliomas, the objective of this study was to investigate the association between epilepsy prior to glioma diagnosis and survival among glioma patients.

METHODS

In a nationwide population-based cohort study, we included 3763 adult glioma patients diagnosed between 2009 and 2018 according to the Danish Neuro-Oncology Registry. Information on epilepsy was redeemed through Danish Neuro-Oncology Registry, National Patient Registry, and National Prescription Registry. Cox proportional hazard models with 95% confidence intervals (CIs) were applied to examine hazard ratios (HRs) for the association between epilepsy (< 1 year prior to glioma including epilepsy at onset; 1-10 years prior to glioma; no prior epilepsy) and risk of death, and whether it differed according to tumor grade and size, performance status, and treatment modalities.

RESULTS

A 32% decreased risk of death in patients with epilepsy within 1 year prior to glioma compared to no prior epilepsy was found (HR = 0.68; CI 0.63-0.75). A favorable prognosis was seen for epilepsy in all glioma grades: II (HR = 0.55; CI 0.39-0.77), III (HR = 0.59; CI 0.48-0.73), and IV (HR = 0.85; CI 0.77-0.94).

CONCLUSIONS

Patients with epilepsy within 1 year prior to glioma diagnosis had significant survival benefits compared to patients with no prior epilepsy. This association was significant for both low-grade gliomas (grade II) and high-grade gliomas (grade III and IV). Survival benefits in glioma patients with epilepsy at onset are possibly primarily attributable to tumor-specific histopathology, molecular biomarkers, and early diagnosis.

Clinical characteristics associated with postoperative seizure control in adult low-grade gliomas: a systematic review and meta-analysis

Background

Epilepsy is the most common symptom in patients with supratentorial low-grade gliomas (LGGs), which adversely affects the patient's quality of life. Poor seizure control with anti-epileptic therapy is an indication for surgery in these patients. Recent studies have sought to identify predictors of postoperative seizure control after surgical resection of LGG; gross total resection was shown to be a significant predictor in this respect. However, the prognostic value of other factors is not clear.

Methods

We performed a systematic review and meta-analysis of 23 studies with a combined study population of 2641 patients with LGG, in order to identify potential factors associated with favorable postoperative seizure control. Data were extracted on age and sex of patient, tumor location, tumor histology, type of seizure, seizure duration, extent of resection, and imaging characteristics.

Results

Patients ≥45 years of age achieved better postoperative seizure control (risk ratio [RR], 0.89; 95% CI, 0.81-0.99). Focal seizures were associated with poor seizure control (RR, 1.32; 95% CI, 1.18-1.49) compared with generalized seizures (RR, 0.77; 95% CI, 0.68-0.87). Prolonged history of seizures (≥1 y) had a negative impact on postoperative seizure control (RR, 1.22; 95% CI, 1.10-1.34). Gross total resection was superior to subtotal resection with respect to postoperative seizure control (RR, 0.68; 95% CI, 0.63-0.73).

Conclusions

This systematic review and meta-analysis identified predictors of postoperative seizure control in patients undergoing surgical resection of LGGs. Our results provide a reference for clinical treatment of LGG-related epilepsy.

Association Between IDH1 and IDH2 Mutations and Preoperative Seizures in Patients with Low-Grade Versus High-Grade Glioma: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with brain tumors, particularly gliomas, commonly present with seizures. Higher incidence of seizure has been reported in low-grade gliomas and tumors located within the temporal and insular area. The association between IDH1 and IDH2 mutations with preoperative seizures in glioma and the magnitude of this association in low-grade versus high-grade gliomas are unclear. To clarify this relationship, a systematic review and meta-analysis was performed.

METHODS

Following accepted guidelines and systematic review recommendations, electronic searches were performed in journal databases up to May 2017. Data were extracted and pooled via meta-analysis.

RESULTS

We compared 782 patients with IDH1 and IDH2 mutations with 803 patients with wild-type IDH1 and IDH2 before surgery. There was a significant difference in seizure incidence between the IDH1 mutation group (61.6%) and wild-type IDH1 group (32.1%) (odds ratio 2.76; 95% confidence interval, 1.26-6.02; I² = 73%; P = 0.01). Similar findings were observed in analysis of IDH1 and IDH2 mutations (odds ratio 2.74; 95% confidence interval, 1.74-4.33; I² = 58%; P < 0.0001). The difference remained in both mutation groups (IDH1, IDH1 and IDH2) with grade II gliomas but not with grade III and IV gliomas. Patients with grade II gliomas showed a higher rate of IDH1 and IDH2 mutations and seizures than patients with grade III and IV gliomas.

CONCLUSIONS

This study demonstrated a significant association of IDH1 and IDH2 mutations with incidence of preoperative seizures. This association was significant only in patients with low-grade glioma (grade II) and not in patients with higher grade gliomas (grade III and IV).

Epilepsy and brain tumors

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

Tumour associated epilepsy and glutamate excitotoxicity in patients with gliomas

Tumour associated epilepsy (TAE) is common, debilitating and often not successfully controlled by surgical resection of the tumour and administration of multiple anti-epileptic drugs. It represents a cause of significant lost quality of life in an incurable disease and is therefore an important subject for ongoing research. The pathogenesis of TAE is likely to be multifactorial and involve, on the microscopic level, the interaction of genetic factors, changes in the peritumoural microenvironment, alterations in synaptic neurotransmitter release and re-uptake, and the excitotoxic effects of glutamate. On a macroscopic level, the occurrence of TAE is likely to be influenced by tumour size, location and interaction with environmental factors. The optimal treatment of TAE requires a multi-disciplinary approach with input from neurosurgeons, neurologists, radiologists, pathologists and basic scientists. This article reviews the current literature regarding the incidence, treatment, and aetiology of TAE.

Surgery for low-grade glioma infiltrating the central cerebral region: location as a predictive factor for neurological deficit, epileptological outcome, and quality of life

Object

A main concern with regard to surgery for low-grade glioma (LGG, WHO Grade II) is maintenance of the patient's functional integrity. This concern is particularly relevant for gliomas in the central region, where damage can have grave repercussions. The authors evaluated postsurgical outcomes with regard to neurological deficits, seizures, and quality of life.

Methods

Outcomes were compared for 33 patients with central LGG (central cohort) and a control cohort of 31 patients with frontal LGG (frontal cohort), all of whom had had medically intractable seizures before undergoing surgery with mapping while awake. All surgeries were performed in the period from February 2007 through April 2010 at the same institution.

Results

For the central cohort, the median extent of resection was 92% (range 80%–97%), and for the frontal cohort, the median extent of resection was 93% (range 83%–98%; p = 1.0). Although the rate of mild neurological deficits was similar for both groups, seizure freedom (Engel Class I) was achieved for only 4 (12.1%) of 33 patients in the central cohort compared with 26 (83.9%) of 31 patients in the frontal cohort (p < 0.0001). The rate of return to work was lower for patients in the central cohort (4 [12.1%] of 33) than for the patients in the frontal cohort (28 [90.3%] of 31; p < 0.0001).

Conclusions

Resection of central LGG is feasible and safe when appropriate intraoperative mapping is used. However, seizure control for these patients remains poor, a finding that contrasts markedly with seizure control for patients in the frontal cohort and with that reported in the literature. For patients with central LGG, poor seizure control ultimately determines quality of life because most will not be able to return to work.

Spontaneous and therapeutic prognostic factors in adult hemispheric World Health Organization Grade II gliomas: a series of 1097 cases

Object

The spontaneous prognostic factors and optimal therapeutic strategy for WHO Grade II gliomas (GIIGs) have yet to be unanimously defined. Specifically, the role of resection is still debated, most notably because the actual amount of resection has seldom been assessed.

Methods

Cases of GIIGs treated before December 2007 were extracted from a multicenter database retrospectively collected since January 1985 and prospectively collected since 1996. Inclusion criteria were a patient age ≥ 18 years at diagnosis, histological diagnosis of WHO GIIG, and MRI evaluation of tumor volume at diagnosis and after initial surgery. One thousand ninety-seven lesions were included in the analysis. The mean follow-up was 7.4 years since radiological diagnosis. Factors significant in a univariate analysis (with a p value ≤ 0.1) were included in the multivariate Cox proportional hazard regression model analysis.

Results

At the time of radiological diagnosis, independent spontaneous factors of a poor prognosis were an age ≥ 55 years, an impaired functional status, a tumor location in a nonfrontal area, and, most of all, a larger tumor size. When the study starting point was set at the time of first treatment, independent favorable prognostic factors were limited to a smaller tumor size, an epileptic symptomatology, and a greater extent of resection.

Conclusions

This large series with its volumetric assessment refines the prognostic value of previously stressed clinical and radiological parameters and highlights the importance of tumor size and location. The results support additional arguments in favor of the predominant role of resection, in accordance with recently reported experiences.

Seizures and the natural history of World Health Organization Grade II gliomas: a review

OBJECTIVE

The majority of adults with low-grade gliomas have seizures. Despite the frequency of seizures as initial symptoms and symptoms of later disease, seizures in relation to the natural course of low-grade gliomas have received little attention.

METHODS

In this review, we provide an update of the literature on the prognostic impact of preoperative seizures and discuss the tumor- and treatment-related factors affecting seizure control at later stages of the disease.

RESULTS

Seizures occur most frequently at disease presentation and predict a more favorable outcome. Initial seizures are correlated with tumor location and possibly indirectly to the molecular profile of the tumor. About 50% of all patients with seizures at presentation continue to have seizures before surgery. Maximal tumor resection, including resection of epileptic foci, is a valuable strategy for improving seizure control. In addition, radiotherapy and chemotherapy, as single therapies or in combination with surgery, have shown beneficial effects in terms of seizure reduction. Recurrent seizures after macroscopically complete tumor resection may be a marker for accelerated tumor growth. Recurrent seizures after an initial transient stabilization after radiotherapy and/or chemotherapy may be a marker for anaplastic tumor transformation.

CONCLUSION

Preoperative seizures likely reflect, apart from tumor location, intrinsic tumor properties as well. Change in seizure control in individual patients is frequently associated with altered tumor behavior. Including seizures and seizure control as clinical parameters is recommended in future trials of low-grade gliomas to further establish the prognostic value of these symptoms and to identify the factors affecting seizure control.

CD34 and microtubule-associated protein 2 expression in dysembryoplastic neuroepithelial tumours with an emphasis on dual expression in non-specific types

AIMS

 Three histological variants of dysembryoplastic neuroepithelial tumour (DNT) have been described, namely, simple, complex and non-specific. However, the concept of non-specific variants of DNT remains controversial, because they cannot be accurately distinguished by histological findings alone from ordinary gliomas. The aim was to characterize further the non-specific histological forms of DNT.

METHODS AND RESULTS

Forty-one DNTs classified as three histological forms were investigated with CD34 and microtubule-associated protein 2 (MAP2) immunohistochemistry. CD34 immunoreactivity was more frequently observed in non-specific DNT types (16/18 cases; 88.9%) than in classic types (6/23 cases; 26.1%) (P < 0.001). Peritumoral CD34 expression of non-neoplastic cells was significantly associated with CD34-positive tumours (20/22 cases; 90.9%) than with CD34-negative tumours (3/19 cases; 15.8%) (P < 0.001). MAP2 positivity in oligodendroglia-like cells or glial elements was significantly different between classic types and non-specific types (P = 0.025). CD34 and MAP2 immunoreactivities were significantly more frequent in non-specific types (83.3%) than in simple (10%) and complex forms (30.8%) (P < 0.001).

CONCLUSIONS

Non-specific DNTs are glioneuronal tumours that have a heterogeneous population of cells with more immature neuronal and glial phenotypes. Furthermore, with regard to practical implications, combined analysis of CD34 and MAP2 is useful in distinguishing DNTs from particularly diagnostically challenging mimics.

Brain tumors in adults with medically intractable epilepsy

Much of the literature on tumors arising in the setting of chronic epilepsy focuses on children. This study reviewed 1 institution's 141-patient experience with tumors in adults arising in this clinical setting. The majority of tumors (71.6%) arose in the temporal lobe. The most common tumor types encountered included ganglioglioma (n = 38), low-grade fibrillary astrocytoma (n = 24), and low-grade oligodendroglioma (n = 22). Coexistent focal cortical dysplasia (type IA) was identified in 15 cases (10.6%). The largest group of tumors in adults were World Health Organization (WHO) grade II neoplasms compared with WHO grade I tumors in children. Gangliogliomas are the most commonly encountered neoplasms. Coexistent focal cortical dysplasia may be observed in a significant minority of tumors, suggesting a possible developmental origin for some of these neoplasms.

Tumours arising in the setting of paediatric chronic epilepsy

BACKGROUND

Along with malformations of cortical development or cortical dysplasia, hippocampal sclerosis, and remote ischaemic damage, tumours are among the more commonly identifiable causes of medically intractable seizures in paediatric age patients. This study reviews one institution's 20 year experience with tumours arising in this clinical setting.

METHODS

Retrospective review of 129 paediatric patients [less than 19 years of age, 65 females (50.4%)] with tumours and medically intractable seizures encountered during a 20 year period of time (1989-2009). Using the most recent World Health Organization (WHO) classification of brain tumours, tumour type and grade were assessed.

RESULTS

The most common sites of origin included temporal lobe (n = 77, 59.7%), parietal lobe (n = 20, 15.5%), and frontal lobe (n = 15, 11.6%). WHO grade included 73 (56.6%) grade I tumours, 32 (24.8%) grade II tumours, and 18 (14%) grade I/II tumours. In six cases (4.7%), a WHO grade was not associated with mass. Tumour types included: ganglioglioma (n = 48, 37.2%), dysembryoplastic neuroepithelial tumour (n = 17, 13.2%), low grade astrocytoma (n = 15, 11.6%), low grade mixed glioma (n = 8, 6.2%), low grade oligodendroglioma (n = 5, 3.9%), meningioangiomatosis (n = 4, 3.1%) angiocentric glioma (n = 3, 2.3%), and dysembryoplastic neuroepithelial tumour/ganglioglioma composite tumour (n = 3, 2.3%). Less frequently observed lesions (n = 1 or 2) included pilocytic astrocytoma, protoplasmic astrocytoma, pleomorphic xanthoastrocytoma, and glioneuronal hamartoma. In 18 cases, distinction between low grade glioma and low grade glioneuronal tumour could not be definitively made. Coexisting malformation of cortical development/cortical dysplasia was noted in 29.8% of evaluable cases. In four tumours, coexistent hippocampal sclerosis was identified. Ki-67 labelling indices were less than 5% in all (n = 51) cases assessed. Of 25 tumours evaluated for chromosome 1p status, only one low grade mixed glioma demonstrated evidence of deletion; only one of 22 evaluated tumours (a low grade mixed glioma) showed evidence of chromosome 19q deletion.

CONCLUSION

Collectively, WHO grade I glioneuronal tumours account for slightly more than half of all neoplasms which cause intractable epilepsy in paediatric patients. A significant minority of tumours (n = 18, 14%) were difficult to definitively classify as glioma versus glioneuronal tumour, due to extent of sampling. Coexistent pathologies including malformation of cortical development/cortical dysplasia may be observed in a significant minority of tumours, suggesting a possible developmental origin for some tumours arising in this setting.

Seizures in patients with low-grade gliomas--incidence, pathogenesis, surgical management, and pharmacotherapy

Seizures complicate the clinical course of > 80% of patients with low-grade gliomas. Patients with some tumor variants almost always have epilepsy. Diffuse low-grade gliomas (LGG) are believed to cause epilepsy through partial deafferentiation of nearby brain cortex (denervation hypersensitivity). Glioneural tumors may interfere with local neurotransmitter levels and are sometimes associated with structural abnormalities of the brain which may produce seizures. The severity of tumor associated epilepsy varies considerably between patients. Some cases may present with a first seizure. Others suffer from long-standing pharmacoresistant epilepsy. Seizure control rates of > 70-80% can be expected after complete tumor resections. Patients with drug-resistant epilepsy require a comprehensive preoperative epileptological work-up which may include the placement of subdural (and intraparenchymal) electrodes or intraoperative electrocorticography (ECoG) for the delineation of extratumoral seizure foci. Partial and subtotal tumor resections are helpful in selected cases, i.e. for gliomas involving the insula. In one series, 40% of patients presented for surgery with uncontrolled seizures, i.e. medical therapy alone often fails to control tumor-related epilepsy. Use of the newer (second generation) non-enzyme inducing antiepileptic drugs (non-EIAED) is encouraged since they seem to have lesser interactions with other medications (e.g. chemotherapy). Chemotherapy and irradiation may have some minor beneficial effects on the patients' seizure disorder. Overall 60-70% of patients may experience recurrent epilepsy during long-term follow-up. Recurrent seizures (not infrequently heralding tumor recurrence) after surgery continue to pose significant clinical problems.

Epilepsy and insular Grade II gliomas: an interdisciplinary point of view from a retrospective monocentric series of 46 cases

OBJECT

There are few data in the literature concerning a multimodal approach to insular WHO Grade II gliomas (GIIGs) and the control of epilepsy after treatment. In this paper, the authors describe a monocentric series of 46 cases in which patients underwent various sequential treatments for insular GIIGs. On the basis of global results with regard to epilepsy, the respective interests in the various treatments are discussed.

METHODS

Available data on 46 patients harboring insular GIIGs were extracted from a local database of 288 GIIGs. The various therapeutic sequences were analyzed in parallel with the course of seizure frequency.

RESULTS

Despite the usual difficulties with seizure quantification in retrospective studies, the authors showed that 1) the negative course of seizure frequency was mostly connected to tumor progression, 2) surgery almost always had a favorable effect on epilepsy, and 3) chemotherapy had a mostly favorable effect with acceptable tolerance. The authors were unable to draw conclusions about the role of radiotherapy given the too few cases.

CONCLUSIONS

This extensive experience with insular GIIGs tends to confirm interest in their surgical removal and supports interest in chemotherapy from an epileptological point of view.

Seizure characteristics and control following resection in 332 patients with low-grade gliomas

OBJECT

Seizures play an important role in the clinical presentation and postoperative quality of life of patients who undergo surgical resection of low-grade gliomas (LGGs). The aim of this study was to identify factors that influenced perioperative seizure characteristics and postoperative seizure control.

METHODS

The authors performed a retrospective chart review of all cases involving adult patients who underwent initial surgery for LGGs at the University of California, San Francisco between 1997 and 2003.

RESULTS

Three hundred and thirty-two cases were included for analysis; 269 (81%) of the 332 patients presented with >or=1 seizures (generalized alone, 33%; complex partial alone, 16%; simple partial alone, 22%; and combination, 29%). Cortical location and oligodendroglioma and oligoastrocytoma subtypes were significantly more likely to be associated with seizures compared with deeper midline locations and astrocytoma, respectively (p=0.017 and 0.001, respectively; multivariate analysis). Of the 269 patients with seizures, 132 (49%) had pharmacoresistant seizures before surgery. In these patients, seizures were more likely to be simple partial and to involve the temporal lobe, and the period from seizure onset to surgery was likely to have been longer (p=0.0005, 0.0089, and 0.006, respectively; multivariate analysis). For the cohort of patients that presented with seizures, 12-month outcome after surgery (Engel class) was as follows: seizure free (I), 67%; rare seizures (II), 17%; meaningful seizure improvement (III), 8%; and no improvement or worsening (IV), 9%. Poor seizure control was more common in patients with longer seizure history (p<0.001) and simple partial seizures (p=0.004). With respect to treatment-related variables, seizure control was far more likely to be achieved after gross-total resection than after subtotal resection/biopsy alone (odds ratio 16, 95% confidence interval 2.2-124, p=0.0064). Seizure recurrence after initial postoperative seizure control was associated with tumor progression (p=0.001).

CONCLUSIONS

The majority of patients with LGG present with seizures; in approximately half of these patients, the seizures are pharmacoresistant before surgery. Postoperatively, >90% of these patients are seizure free or have meaningful improvement. A shorter history of seizures and gross-total resection appear to be associated with a favorable prognosis for seizure control.

In vivo uptake and metabolism of alpha-[11C]methyl-L-tryptophan in human brain tumors

Abnormal metabolism of tryptophan has been implicated in modulation of tumor cell proliferation and immunoresistance. alpha-[(11)C]Methyl-L-tryptophan (AMT) is a PET tracer to measure cerebral tryptophan metabolism in vivo. In the present study, we have measured tumor tryptophan uptake in 40 patients with primary brain tumors using AMT PET and standard uptake values (SUV). Tryptophan metabolism was further quantified in 23 patients using blood input data. Estimates of the volume of distribution (VD') and the metabolic rate constant (k(3)') were calculated and related to magnetic resonance imaging (MRI) and histology findings. All grade II to IV gliomas and glioneuronal tumors showed increased AMT SUV, including all recurrent/residual tumors. Gadolinium enhancement on MRI was associated with high VD' values, suggesting impaired blood-brain barrier, while k(3)' values were not related to contrast enhancement. Low-grade astrocytic gliomas showed increased tryptophan metabolism, as measured by k(3)'. In contrast, oligodendrogliomas showed high VD' values but lower k(3)' as compared with normal cortex. In astrocytic tumors, low grade was associated with high k(3)' and lower VD', while high-grade tumors showed the reverse pattern. The findings show high AMT uptake in primary and residual/recurrent gliomas and glioneuronal tumors. Increased AMT uptake can be due to increased metabolism of tryptophan and/or high volume of distribution, depending on tumor type and grade. High tryptophan metabolic rates in low-grade tumors may indicate activation of the kynurenine pathway, a mechanism regulating tumor cell growth. AMT PET might be a useful molecular imaging method to guide therapeutic approaches aimed at controlling tumor cell proliferation by acting on tryptophan metabolism.

[11C]-Methionine PET: dysembryoplastic neuroepithelial tumours compared with other epileptogenic brain neoplasms

BACKGROUND AND OBJECTIVES

Brain tumours responsible for longstanding partial epilepsy are characterised by a high prevalence of dysembryoplastic neuroepithelial tumour (DNT), whose natural evolution is much more benign than that of gliomas. The preoperative diagnosis of DNT, which is not yet feasible on the basis of available clinical and imaging data, would help optimise the therapeutic strategy for this type of tumour. This study tested whether [(11)C]-methionine positron emission tomography (MET-PET) could help to distinguish DNTs from other epileptogenic brain tumours.

METHODS

Prospective study of 27 patients with partial epilepsy of at least six months duration related to a non-rapidly progressing brain tumour on magnetic resonance imaging (MRI). A structured visual analysis, which distinguished between normal, moderately abnormal, or markedly abnormal tumour methionine uptake, as well as various regions of interest and semiquantitative measurements were conducted.

RESULTS

Pathological results showed 11 DNTs (41%), 5 gangliogliomas (18%), and 11 gliomas (41%). MET-PET visual findings significantly differed between the various tumour types (p<0.0002), regardless of gadolinium enhancement on MRI, and were confirmed by semiquantitative analysis (p<0.001 for all calculated ratios). All gliomas and gangliogliomas were associated with moderately or markedly increased tumour methionine uptake, whereas 7/11 DNTs had a normal methionine uptake, including all six located in the mesiotemporal structures. No DNT presented with a marked MET-PET abnormality.

CONCLUSION

Normal MET-PET findings in patient with an epileptogenic and non-rapidly progressing brain tumour are suggestive of DNT, whereas a markedly increased tumour methionine uptake makes this diagnosis unlikely.

Low-grade gliomas: an update on pathology and therapy

Low-grade gliomas (LGG) are not benign neoplasms. Patients with LGG eventually die as a consequence of this disease. Although the survival of patients with LGG is better than that of patients with higher-grade tumours, many of the treatments can produce or contribute to chronic impairment, particularly radiotherapy. Chemotherapy has emerged as a promising therapy, although definitive findings are awaited. Breakthroughs in molecular biology have improved our understanding of tumours and have led to the development of novel treatments and better prognoses. Ongoing clinical trials will help to elucidate the optimum management of patients with LGG.

Application of neuronavigator coupled with an operative microscope and electrocorticography in epilepsy surgery

Application of neuronavigator coupled with an operative microscope and electrocorticography (ECoG) is a new trial for epilepsy surgery for achieving better seizure outcome and better efficiency for lesionectomy. We used a neuronavigator coupled with a microscope to delineate the magnetic resonance image-detected lesion for lesionectomy and used ECoG for evaluation of the epileptogenic foci. There were 46 patients with medically intractable partial seizures who underwent craniotomy for epilepsy surgery. Half of the patients had lesions at the temporal lobe and another half at the extratemporal lobe. Sixty-one percent of the patients were seizure-free (grade I) and 22% were nearly seizure-free (grade II). Overall, 83% of the patients had satisfactory seizure control. Complete lesion removal was successful in 37 patients (80%). For lesions with requiring complete removal, neuronavigator coupled with a microscope was 95% effective for lesionectomy. Class A of postresection ECoG had a higher rate of seizure-free outcome (92%) (P < .05). On the other hand, 93% of patients (26/28) with seizure-free outcome (grade I) needed complete lesion resection (P < .05). Lesions at the extratemporal lobe yielded a higher rate of seizure-free outcome (78.2%, 18/23) (P < .05). Application of neuronavigator and ECoG (additional cortical resection) is usually necessary for temporal lobe lesions. All patients with cavernous hemangioma were seizure-free. The complication rate in our study was 8.7%. Neuronavigator coupled with a microscope provides efficacy and safety to complete lesionectomy, which is a key point of seizure outcome. Intraoperative ECoG is valuable for evaluating the epileptogenic foci for epilepsy surgery especially for lesions at the temporal lobe.

Novel tumor-specific isoforms of BEHAB/brevican identified in human malignant gliomas

Malignant gliomas are deadly brain tumors characterized by diffuse invasion into the surrounding brain tissue. Understanding the mechanisms involved in glioma invasion could lead to new therapeutic strategies. We have previously shown that BEHAB/brevican, an extracellular matrix protein in the central nervous system, plays a role in the invasive ability of gliomas. The mechanisms that underlie BEHAB/brevican function are not yet understood, due in part to the existence of several isoforms that may have different functions. Here we describe for the first time the expression of BEHAB/brevican in human brain and characterize two novel glioma-specific isoforms, B/b(sia) and B/b(Deltag), which are generated by differential glycosylation and are absent from normal adult brain and other neuropathologies. B/b(sia) is an oversialylated isoform expressed by about half the high- and low-grade gliomas analyzed. B/b(Deltag) lacks most of the carbohydrates typically present on BEHAB/brevican and is the major up-regulated isoform of this protein in high-grade gliomas but is absent in a specific subset of low-grade, indolent oligodendrogliomas. B/b(Deltag) is detected on the extracellular surface, where it binds to the membrane by a mechanism distinct from the other BEHAB/brevican isoforms. The glioma-specific expression of B/b(Deltag), its restricted membrane localization, and its expression in all high-grade gliomas tested to date suggest that it may play a significant role in glioma progression and make it an important new potential therapeutic target. In addition, its absence from benign gliomas prompts its use as a diagnostic marker to distinguish primary brain tumors of similar histology but different pathologic course.

Surgical resection for patients with benign primary brain tumors and low grade gliomas

'Benign' brain tumors are a heterogeneous group of primary neoplasms representing 40% of primary brain tumors. Amongst neuroepithelial tumors, astrocytic neoplasms predominate, followed by oligodendroglial and mixed glial and glial-neuronal neoplasms. Less common are tumors of the ependyma, choroid plexus and neuroepithelial tumors of unknown origin such as chordoid glioma of the third ventricle. Neurosurgical intervention is indicated in order to establish a diagnosis, alleviate symptoms of mass effect, hydrocephalus, or hemorrhage, remove a seizure focus and decrease the cell pool at risk of malignant degeneration. As the majority of patients survive their tumor for years after initial diagnosis, the benefits of therapy must be carefully weighed against adverse treatment effects. This article, with a particular focus on surgical management, reflects the authors approach to the treatment of low-grade tumors of the brain parenchyma in the adult and reviews the pertinent literature published on this controversial issue.

Physiology of human cortical neurons adjacent to cavernous malformations and tumors

PURPOSE

Focal neocortical seizures can be associated with a number of specific pathologies including supratentorial tumors and cavernous malformations (CMs), both of which are highly epileptogenic.

METHODS

To begin to address the question of whether these lesions have different mechanisms of epileptogenesis, we used intracellular recordings from neurons adjacent to intracerebral neoplasms and cerebral CMs. Developmental anomalies were not included in this study.

RESULTS

Neurons adjacent to CMs had a greater propensity to show large (>5 mV), complex spontaneous synaptic events than did neurons neighboring neoplastic substrates (50 vs. 4.7% of cells and 75 and 8% of patients, respectively; p < 0.004; p < 0.05). Both spontaneous excitatory and inhibitory events were noted. In contrast, in tissue adjacent to tumors, low-amplitude (<3 mV) spontaneous excitatory activity predominated. Neurons neighboring CMs also exhibited more excitable responses to synaptic stimulation, with multiple action potentials riding on prolonged excitatory postsynaptic potentials (EPSPs) being evoked in 71% of these cells, versus 32% of cells from the tumor group; p < 0.05. In studies using hippocampal tissue, we noted a similar pattern of spontaneous activity in tissue adjacent to CMs.

CONCLUSIONS

These data suggest that CMs may induce seizure activity via a different pathophysiologic mechanism(s) than glial tumors.

Frontal lobe tumoral epilepsy: clinical, neurophysiologic features and predictors of surgical outcome

PURPOSE

To review the clinical, neurophysiologic features and surgical outcomes in patients with frontal lobe tumors and chronic intractable seizures.

METHODS

Medical records of patients with intractable epilepsy who underwent resection or stereotactic biopsy of frontal lobe tumor (confirmed by surgical pathology) seen between 1985 and 1999 at Yale University School of Medicine Epilepsy Center were reviewed for age at diagnosis, age at onset of seizures, delay between seizure onset and tumor diagnosis, types and frequencies of seizures, EEG results, use of anticonvulsants, extent of surgery, pathological diagnosis, and tumor recurrence.

RESULTS

Thirty-seven patients were included. Mean age at seizure onset was 31.6 years, and at tumor diagnosis was 36.2 years. Mean duration between onset of seizures and tumor diagnosis was 6.1 years. Seventeen patients had auras. Seizure frequency averaged 7.6 seizures per week, with 58% of patients having more than one seizure type. All patients used anticonvulsants, with 90% eventually using polytherapy. All patients eventually underwent at least one surgical procedure. Only 13 (35.1%) patients were class I. Twelve (32.4%) patients were class II, seven (18.9%) class III, and five (13.5%) class IV. No statistically significant differences were seen between good and poor long-term seizure outcome in relation to specific tumor pathology, seizure types, or type of resection.

CONCLUSIONS

Long-term surgical outcomes in tumoral frontal lobe epilepsy are more favorable than those in nontumoral intractable frontal lobe epilepsy (65% class I or II) and less favorable than those in other tumoral epilepsy (overall, 70% class I). Frontal location of intracranial neoplasm may predict a less favorable long-term epilepsy prognosis than tumoral epilepsy in general, an observation for which several explanations are proposed.

Gangliogliomas: an intriguing tumor entity associated with focal epilepsies

Gangliogliomas represent the most frequent tumor entity in young patients suffering from chronic focal epilepsies. In a series of 326 gangliogliomas collected from the University of Bonn Epilepsy Surgery Program and other departments of neuropathology in Germany, Austria, and Switzerland, epidemiological findings and histopathological hallmarks of gangliogliomas are systematically reviewed. The majority of these tumors occur within the temporal lobe and reveal a biphasic histological architecture characterized by a combination of dysplastic neurons and neoplastic glial cell elements. However, gangliogliomas exhibit a considerable variability in their histopathological appearance. Immunohistochemical studies are an important tool to discriminate these neoplasms from other tumor entities. Almost 80% of gangliogliomas reveal immunoreactivity for CD34, a stem cell epitope not expressed in normal brain. Immunohistochemical reactions for MAP2 or NeuN can be employed to characterize the dysplastic nature of neurons in those areas difficult to discriminate from pre-existing brain parenchyma. Less than 50% of the cases display binucleated neurons. With the frequent finding of "satellite" tumor clusters in adjacent brain regions, gangliogliomas are microscopically less circumscribed than previously assumed. The distinction from diffusely infiltrating gliomas is of considerable importance since tumor recurrence or malignant progression are rare events in gangliogliomas. Only little is known about the molecular pathogenesis of these glioneuronal tumors. Our findings support a dysontogenic origin from a glioneuronal precursor lesion with neoplastic, clonal proliferation of the glial cell population. Candidate genes appear to associate with neurodevelopmental signaling cascades rather than cell cycle control or DNA repair mechanisms. The reelin signaling and tuberin/insulin growth receptor pathways have recently been implicated in ganglioglioma development. Powerful new molecular genetic and biological tools can now be employed to unravel the pathogenesis of these intriguing lesions.

Prognostic value of platelet derived growth factor alpha receptor expression in grade 2 astrocytomas and oligoastrocytomas

OBJECTIVE

To determine whether the expression of platelet derived growth factor alpha receptor (PDGFRalpha) in low grade astrocytomas and oligoastrocytomas is associated with survival.

METHODS

Formalin fixed and paraffin embedded tumour samples of 40 consecutive patients with supratentorial diffuse astrocytomas and oligoastrocytomas of WHO grade 2, resected between 1986 and 1993, were used for immunohistochemical staining. The fraction of tumour cells expressing PDGFRalpha protein was quantified and entered into univariate and multivariate survival analyses. Changes in PDGFalpha expression over time were analysed in seven patients in whom reoperations had been performed.

RESULTS

Patients with a relatively high fraction of PDGFRalpha expressing cells had a more favourable outcome in both univariate (p = 0.04) and multivariate analyses (p = 0.02). Expression of PDGFRalpha was greater in oligoastrocytomas than in astrocytomas (p = 0.05). In four reoperated patients with histologically confirmed malignant transformation, there was a marked decrease in the number of cells expressing the receptor.

CONCLUSIONS

There is an association between high PDGFRalpha expression and long survival time in patients with grade 2 astrocytomas and oligoastrocytomas. The findings suggest that expression of the receptor may be a useful prognostic marker in such patients.

Seizure disorders in patients with brain tumors

The aim of this study was to analyze the clinical data of patients with epileptic seizures and diagnosed brain tumors. Analysis included 711 patients with primary and secondary brain tumors. 165 (23%) patients had experienced at least one seizure before tumor diagnosis. The mean time from the first epileptic seizure to tumor diagnosis was 16 months. The patient's age, location and pathology of tumor were associated with occurrence of seizures. Seizures were more common in patients aged 30-50 years. Tumors involving the frontal, frontoparietal, temporal and frontotemporal lobes were associated with occurrence of seizures. According to the histological diagnosis, patients with mixed gliomas (62%), oligodendrogliomas (53%) and astrocytomas (42%) experienced seizures most frequently.

The role of surgery in low grade gliomas

Several prognostic factors appear to be more important than treatment factors in determining the outcome of patients with low grade glioma. The role of surgery in establishing a histological diagnosis or in relieving neurological deficit is well established. The role of surgery in prolonging survival of patients with low grade glioma however, remains controversial, largely because studies in the literature on the management of this disease have been predominantly descriptive and observational, which precludes the setting of standards for the management of these patients. Several viable management options are discussed.

Histological heterogeneity of dysembryoplastic neuroepithelial tumour: identification and differential diagnosis in a series of 74 cases

AIMS

In a retrospective study of resected specimens from 416 patients being treated for long-standing epilepsy, 74 cases of dysembryoplastic neuroepithelial tumour (DNT) were encountered that were all characteristically composed of small round oligodendroglia-like cells (OLC), astrocytes and mature neurones in varying proportions. The architectural patterns, histological, immunohistochemical and ultrastructural features and results of cell proliferation studies and postoperative follow-up are described to facilitate the identification of DNT and to differentiate it from other intrinsic neoplasms that commonly present with seizures.

METHODS AND RESULTS

The tumours presented with early onset of seizures, at a median age of 7 years, without the signs of raised intracranial pressure. A majority of the lesions were located in the temporal lobe (n = 59), with fewer cases in the frontal (n = 8), parietal (n = 6) and occipital lobes (n = 1), and ranged in size from 10 to 70 mm; 33 were cystic. Histologically three types could be distinguished, multinodular, solitary nodular and diffuse. The first type (37.8%) had the features of a typical DNT with multinodular architecture and mixed cellular composition. The second type (33.8%) consisted of a solitary nodule, while the third (28.4%) was a diffuse tumour, both composed of a similar mixture of cells as the multinodular DNT. The lesions were seen in the neocortex and white matter and tumours in the temporal lobe often involved the amygdala and hippocampus. The presence of myxoid matrix, microcystic change, calcification and leptomeningeal involvement were common. Dysplastic neurones at the periphery of the tumour and abnormalities in cortical lamination in the adjacent neocortex were found in about one-third of the resections. Rare mitotic figures were encountered in eight of the tumours and necrosis was found in two. Immunocytochemistry for glial fibrillary acidic protein (GFAP) and neuronal markers neuron-specific enolase, synaptophysin and neurofilament (RT 97) assists in establishing the diagnosis, highlighting the astrocytic and neuronal components, and the OLC, by the absence of expression of GFAP. Electron microscopy showed that in some cases OLC show neuronal differentiation. Although the proliferating cell nuclear antigen labelling index varied between 0 and 45.5%, 20 of the 51 tumours stained failed to express the antigen, in keeping with the indolent nature of this neoplasm. The response to surgery was excellent; none of the tumours have recurred, and the control of seizures remained good.

CONCLUSIONS

Despite some histological heterogeneity, the clinical and pathological features and indolent biological behaviour indicate that these tumours constitute a single distinct entity. The spectrum of morphological appearances of DNT is broader than has been previously reported, the recognition of which is needed to avoid unnecessary neoadjuvant therapy.

Trends in reported incidence of primary malignant brain tumors in children in the United States

BACKGROUND

The reported incidence of primary malignant brain tumors among children in the United States increased by 35% during the period from 1973 through 1994. The purpose of our study was twofold: 1) to determine whether the reported incidence rates for this period are better represented by a linear increase over the entire period ("linear model") or, alternatively, by a step function, with a lower rate in the years preceding 1984-1985 and a constant higher rate afterward ("jump model"); and 2) to identify the specific brain regions and histologic subtypes that have increased in incidence.

METHODS

Incidence data from the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute for the period from 1973 through 1994 for primary malignant brain tumors in children were used to model the number of cases in a year as a random variable from a Poisson distribution by use of either a linear model or a jump model.

RESULTS/CONCLUSIONS

The increase in reported incidence of childhood primary malignant brain tumors is best explained by the jump model, with a step increase in incidence occurring in the mid-1980s. The brain stem and the cerebrum are the primary sites for which an increase in tumor incidence has been reported. The increase in reported incidence of low-grade gliomas in the cerebrum and the brain stem (unaccompanied by an increase in mortality for these sites) supports the substantial contribution of low-grade gliomas to the overall increase in reported incidence for childhood brain tumors.

IMPLICATIONS

The significantly better fit of the data to a jump model supports the hypothesis that the observed increase in incidence somehow resulted from changes in detection and/or reporting of childhood primary malignant brain tumors during the mid-1980s.

Neurosurgical considerations in supratentorial low-grade gliomas: experience with 175 patients

The authors reviewed 175 low-grade hemispheric gliomas surgically treated by one surgeon (P.B.) between 1987 and 1996: 74 astrocytomas (42%), 35 oligodendrogliomas (20%), 52 mixed gliomas (30%), 12 gangliogliomas (7%), and two ependymomas (1%). Patient age ranged from 7.5 to 81.9 years (mean 39.2 years); 84 patients (48%) were males and 91 (52%) females. Postsurgical follow-up review ranged from 0.1 to 225.2 months (mean 36.2 months, median 24.9 months). Either T2-weighted or contrast-enhanced T1-weighted magnetic resonance (MR) images were used to evaluate the percentage of resection achieved and volume of residual disease postoperatively. The majority of patients (55%) had seizures as the presenting symptom, and 45% experienced preoperative symptoms for more than 12 months. Tumor enhancement was present in 21% of cases. In 66% of surgical procedures at least one of the following technical adjuncts was used: monitored local anesthesia, real-time MR imaging, stereotactic guidance with computerized tomography, three dimensional reconstruction, cortical mapping with cortical stimulation, somatosensory or visual evoked potential recording, corticography, or intraoperative ultrasound. Intraoperative MR imaging was used for 40 (22.9%) of the craniotomies and nine (5.14%) biopsies. There were no surgery-related deaths. Complications appeared in 6% of the patients. Progression to a higher-grade tumor occurred in 9.2% of patients within the 3-year follow-up period.