Development of a transplantable glioma tumour model from genetically engineered mice: MRI/MRS/MRSI characterisation

The initial aim of this study was to generate a transplantable glial tumour model of low-intermediate grade by disaggregation of a spontaneous tumour mass from genetically engineered models (GEM). This should result in an increased tumour incidence in comparison to GEM animals. An anaplastic oligoastrocytoma (OA) tumour of World Health Organization (WHO) grade III was obtained from a female GEM mouse with the S100β-v-erbB/inK4a-Arf (+/-) genotype maintained in the C57BL/6 background. The tumour tissue was disaggregated; tumour cells from it were grown in aggregates and stereotactically injected into C57BL/6 mice. Tumour development was followed using Magnetic Resonance Imaging (MRI), while changes in the metabolomics pattern of the masses were evaluated by Magnetic Resonance Spectroscopy/Spectroscopic Imaging (MRS/MRSI). Final tumour grade was evaluated by histopathological analysis. The total number of tumours generated from GEM cells from disaggregated tumour (CDT) was 67 with up to 100 % penetrance, as compared to 16 % in the local GEM model, with an average survival time of 66 ± 55 days, up to 4.3-fold significantly higher than the standard GL261 glioblastoma (GBM) tumour model. Tumours produced by transplantation of cells freshly obtained from disaggregated GEM tumour were diagnosed as WHO grade III anaplastic oligodendroglioma (ODG) and OA, while tumours produced from a previously frozen sample were diagnosed as WHO grade IV GBM. We successfully grew CDT and generated tumours from a grade III GEM glial tumour. Freezing and cell culture protocols produced progression to grade IV GBM, which makes the developed transplantable model qualify as potential secondary GBM model in mice.

Paradoxical perfusion metrics of high-grade gliomas with an oligodendroglioma component: quantitative analysis of dynamic susceptibility contrast perfusion MR imaging

INTRODUCTION

The aim of this study is to investigate perfusion characteristics of glioblastoma with an oligodendroglioma component (GBMO) compared with conventional glioblastoma (GBM) using dynamic susceptibility contrast (DSC) perfusion magnetic resonance (MR) imaging and microvessel density (MVD).

METHODS

The study was approved by the institutional review board. Newly diagnosed high-grade glioma patients were enrolled (n = 72; 20 GBMs, 14 GBMOs, 19 anaplastic astrocytomas (AAs), 13 anaplastic oligodendrogliomas (AOs), and six anaplastic oligoastrocytomas (AOAs)). All participants underwent preoperative MR imaging including DSC perfusion MR imaging. Normalized cerebral blood volume (nCBV) values were analyzed using a histogram approach. Histogram parameters were subsequently compared across each tumor subtype and grade. MVD was quantified by immunohistochemistry staining and correlated with perfusion parameters. Progression-free survival (PFS) was assessed according to the tumor subtype.

RESULTS

GBMO displayed significantly reduced nCBV values compared with GBM, whereas grade III tumors with oligodendroglial components (AO and AOA) exhibited significantly increased nCBV values compared with AA (p < 0.001). MVD analyses revealed the same pattern as nCBV results. In addition, a positive correlation between MVD and nCBV values was noted (r = 0.633, p < 0.001). Patients with oligodendroglial tumors exhibited significantly increased PFS compared with patients with pure astrocytomas in each grade.

CONCLUSION

In contrast to grade III tumors, the presence of oligodendroglial components in grade IV tumors resulted in paradoxically reduced perfusion metrics and MVD. In addition, patients with GBMO exhibited a better clinical outcome compared with patients with GBM.

Loss of heterozygosity analysis in an anaplastic oligodendroglioma arising after radiation therapy

OBJECTIVE AND IMPORTANCE

Oligodendroglial tumors rarely occur after radiation therapy. Here, we report a rare case of anaplastic oligodendroglioma arising after radiation therapy, in which genetic analysis was performed.

CLINICAL PRESENTATION AND INTERVENTION

A 41-year-old man who had received radiation therapy for a tumor of the suprasellar and pineal regions 31 years previously, presented with headache and progressive right hemiparesis. Magnetic resonance (MR) images revealed a ring-enhanced mass lesion in the left frontal lobe. Total removal of the tumor was performed through left frontoparietal craniotomy, and the histologic diagnosis was anaplastic oligodendroglioma. Using 23 microsatellite markers, the allelic status of chromosomes 1p, 10, 17p and 19q was evaluated by a PCR-based loss of heterozygosity (LOH) assay. Markers on chromosomes 1p, 17p and 19q revealed LOH, but none of the markers on chromosome 10 showed LOH. Based on the genetic analysis, this tumor was considered to be sensitive to chemotherapy. Two courses of chemotherapy, with procarbazine, ACNU and vincristine, were performed. However, tumor recurrence was detected only 3 months after the surgery. Despite additional radiochemotherapy, the tumor aggressively increased in size and the patient died with multiple recurrent tumors 1 year after surgery.

CONCLUSION

The anaplastic oligodendroglioma presented in this report showed a more aggressive clinical course than was expected from the genetic analysis. The significance of 1p and 19q LOH in radiation-induced oligodendroglial tumors might differ from that in spontaneous counterparts.

Oligodendroglioma presenting with intradural spinal metastases: an unusual cause of cauda equina syndrome

We report a 37-year-old man with a primary intracranial oligodendroglioma presenting later with symptomatic multiple cerebrospinal fluid (CSF) intradural drop spinal metastases. This patient initially presented in 2006 with complex partial seizures. Initial histology demonstrated World Health Organization (WHO) grade 2 oligodendroglioma. The patient had further generalised seizures 7 months after initial tumour resection. MRI at that time confirmed tumour recurrence. The patient underwent a repeat craniotomy. Histology showed anaplastic transformation to a WHO grade 3 oligodendroglioma. About 30 months after his initial presentation, the patient developed a focal neurological deficit in the left leg with associated retention of urine. MRI of the neuraxis demonstrated widespread leptomeningeal metastatic drop deposits within the spinal canal. We discuss the mechanisms involved in tumour dissemination throughout the CSF. We also review the relevant literature regarding this phenomenon.

Group independent component analysis of language fMRI from word generation tasks

Language fMRI has been used to study brain regions involved in language processing and has been applied to pre-surgical language mapping. However, in order to provide clinicians with optimal information, the sensitivity and specificity of language fMRI needs to be improved. Type II error of failing to reach statistical significance when the language activations are genuinely present may be particularly relevant to pre-surgical planning, by falsely indicating low surgical risk in areas where no activations are shown. Furthermore, since the execution of language paradigms involves cognitive processes other than language function per se, the conventional general linear model (GLM) method may identify non-language-specific activations. In this study, we assessed an exploratory approach, independent component analysis (ICA), as a potential complementary method to the inferential GLM method in language mapping applications. We specifically investigated whether this approach might reduce type II error as well as generate more language-specific maps. Fourteen right-handed healthy subjects were studied with fMRI during two word generation tasks. A similarity analysis across tasks was proposed to select components of interest. Union analysis was performed on the language-specific components to increase sensitivity, and conjunction analysis was performed to identify language areas more likely to be essential. Compared with GLM, ICA identified more activated voxels in the putative language areas, and signals from other sources were isolated into different components. Encouraging results from one brain tumor patient are also presented. ICA may be used as a complementary tool to GLM in improving pre-surgical language mapping.

Prediction of oligodendroglial tumor subtype and grade using perfusion weighted magnetic resonance imaging

OBJECT

Treatment of patients with oligodendrogliomas relies on histopathological grade and characteristic cytogenetic deletions of 1p and 19q, shown to predict radio- and chemosensitivity and prolonged survival. Perfusion weighted magnetic resonance (MR) imaging allows for noninvasive determination of relative tumor blood volume (rTBV) and has been used to predict the grade of astrocytic neoplasms. The aim of this study was to use perfusion weighted MR imaging to predict tumor grade and cytogenetic profile in oligodendroglial neoplasms.

METHODS

Thirty patients with oligodendroglial neoplasms who underwent preoperative perfusion MR imaging were retrospectively identified. Tumors were classified by histopathological grade and stratified into two cytogenetic groups: 1p or 1p and 19q loss of heterozygosity (LOH) (Group 1), and 19q LOH only on intact alleles (Group 2). Tumor blood volume was calculated in relation to contralateral white matter. Multivariate logistic regression analysis was used to develop predictive models of cytogenetic profile and tumor grade.

RESULTS

In World Health Organization Grade II neoplasms, the rTBV was significantly greater (p < 0.05) in Group 1 (mean 2.44, range 0.96-3.28; seven patients) compared with Group 2 (mean 1.69, range 1.27-2.08; seven patients). In Grade III neoplasms, the differences between Group 1 (mean 3.38, range 1.59-6.26; four patients) and Group 2 (mean 2.83, range 1.81-3.76; 12 patients) were not significant. The rTBV was significantly greater (p < 0.05) in Grade III neoplasms (mean 2.97, range 1.59-6.26; 16 patients) compared with Grade II neoplasms (mean 2.07, range 0.96-3.28; 14 patients). The models integrating rTBV with cytogenetic profile and grade showed prediction accuracies of 68 and 73%, respectively.

CONCLUSIONS

Oligodendroglial classification models derived from advanced imaging will improve the accuracy of tumor grading, provide prognostic information, and have potential to influence treatment decisions.

Negative correlation of Nogo-A with the malignancy of oligodendroglial tumor

OBJECTIVE

Nogo-A is an axon regeneration inhibitor, and its function in central nervous system (CNS) is still unknown. The present study is to explore the relationship between the expression of Nogo-A and the malignancy of oligodendroglial tumors in patients.

METHODS

Tumor tissue samples with different malignancy grade were obtained from the hospitals. The samples used for detection had been diagnosed as oligodendroglial tumors (oligodendroglioma or anaplastic oligodendroglioma). The expression of Nogo-A was detected by immunohistochemistry and western-blot analysis. The correlation test between the Nogo-A expression and the morphological changes (the percentages of atypical cells and mitotic cells in the tumors) related to the malignancy of tumor tissues was performed.

RESULTS

There was significant negative correlation between the Nogo-A expression and the morphological change of tumor tissues according to immunohistochemistry. Western-blot analysis also indicated that the gray value of Nogo-A protein band in the oligodendroglioma group was significantly higher than that in the anaplastic oligodendroglioma group.

CONCLUSION

Nogo-A expression was negatively correlated with the malignancy grade of oligodendroglial tumors.

DNA hypermethylation and aberrant expression of the EMP3 gene at 19q13.3 in Human Gliomas

Allelic losses on 19q are found in the majority of oligodendroglial tumors and approximately one-third of diffuse astrocytomas. However, the tumor suppressor genes (TSG) on 19q are still elusive. Using cDNA microarray expression profiling, EMP3 at 19q13.3 was among those genes showing the most pronounced expression differences. In line with this, other authors reported EMP3 as being epigenetically silenced in neuroblastomas and astrocytomas. To further investigate EMP3 as a TSG candidate on 19q13.3, we performed molecular analysis of this gene in 162 human gliomas. Mutation analysis did not reveal EMP3 alteration in 132 gliomas. In oligodendroglial tumors, we found that aberrant methylation in the 5'-region of EMP3 was significantly associated with reduced mRNA expression and LOH 19q. In astrocytomas, EMP3 hypermethylation was also paralleled by reduced expression but was independent of the 19q status. EMP3 hypermethylation was detected in more than 80% of diffuse, anaplastic astrocytomas and secondary glioblastomas. Primary glioblastomas, however, mostly lacked EMP3 hypermethylation and frequently overexpressed EMP3. Our data corroborate that oligodendroglial and astrocytic gliomas often show EMP3 hypermethylation and aberrant expression. Furthermore, our findings suggest that primary and secondary glioblastomas are not only characterized by distinct genetic profiles but also differ in their epigenetic aberrations.

[Oligodendrogliomas: their morphological characteristics and molecular alterations]

INTRODUCTION

Oligodendrogliomas constitute a group of infiltrating gliomas with a good response to radio and chemotherapy, which makes it important to distinguish them from the other gliomas and more especially from astrocytomas. Although oligodendrogliomas generally present typical histological features and are easy to diagnose, they sometimes have a mixed or hybrid morphology that makes their classification difficult and ambiguous. In these cases immunohistochemistry is of little use, since to date no markers have been found that enable a reliable distinction to be made between oligodendrogliomas and astrocytomas.

DEVELOPMENT

Here we review the histological criteria of oligodendroglial tumours and how to distinguish them from other morphologically similar brain tumours. We also discuss how alterations to the short arm of chromosome 1 and to the long arm of chromosome 19 (co-deletion of 1p/19q), which can be detected using FISH or PCR, enable us to classify mixed oligoastrocytic tumours and to define subgroups of oligodendrogliomas with different prognoses and responses to treatment.

CONCLUSIONS

In daily practice, the status of 1p and 19q should be analysed in all tumours with an oligodendroglial histological phenotype, because this makes it possible to define subgroups each having different prognoses and responses to therapy.

Cerebral blood volume, genotype and chemosensitivity in oligodendroglial tumours

Introduction

The biological factors responsible for differential chemoresponsiveness in oligodendroglial tumours with or without the −1p/−19q genotype are unknown, but tumour vascularity may contribute. We aimed to determine whether dynamic susceptibility contrast (DSC) magnetic resonance imaging (MRI) could distinguish molecular subtypes of oligodendroglial tumour, and examined the relationship between relative cerebral blood volume (rCBV) and outcome following procarbazine, lomustine and vincristine (PCV) chemotherapy.

Methods

Pretherapy rCBV was calculated and inter- and intraobserver variability assessed. Allelic imbalance in 1p36, 19q13, 17p13, 10p12–15, and 10q22–26 and p53 mutation (exons 5–8) were determined. rCBV was compared with genotype and clinicopathological characteristics (n=37) and outcome following PCV chemotherapy (n=33).

Results

1p/19q loss was seen in 6/9 grade II oligodendrogliomas, 6/14 grade II oligoastrocytomas, 4/4 grade III oligodendrogliomas, and 3/10 grade III oligoastrocytomas. rCBV measurements had good inter- and intraobserver variability, but did not distinguish histology subtype or grade. Tumours with 1p/19q loss had higher rCBV values (Student’s t-test P=0.001). Receiver operating characteristic analysis revealed a cut-off of 1.59 for identifying genotype (sensitivity 92%, specificity 76%). Tumours with high and low rCBV showed response to chemotherapy. The −1p/−19q genotype, but not rCBV, was strongly associated with response, progression-free and overall survival following PCV chemotherapy. Tumours with high rCBV and intact 1p/19q were associated with shorter progression-free and overall patient survival than those with intact 1p/19q and low rCBV or high rCBV and 1p/19q loss.

Conclusion

rCBV identifies oligodendroglial tumours with 1p/19q loss, but does not predict chemosensitivity. The prognostic significance of rCBV may differ in oligodendroglial tumours with or without the −1p/−19q genotype.

Conduction aphasia as a function of the dominant posterior perisylvian cortex

✓ Assessment of eloquent functions during brain mapping usually relies on testing reading, speech, and comprehension to uncover transient deficits during electrical stimulation. These tests stem from findings predicted by the Geschwind–Wernicke hypothesis of receptive and expressive cortices connected by white matter tracts. Later work, however, has emphasized cortical mechanisms of language function. The authors report two cases that demonstrate that conduction aphasia is cortically mediated and can be inadequately assessed if not specifically evaluated during brain mapping.

To determine the distribution of language on the dominant cortex, electrical cortical stimulation was performed in two cases by using implanted subdural electrodes during brain mapping before epilepsy surgery. A transient isolated deficit in repetition of language was reported during stimulation of the posterior portion of the dominant superior temporal gyrus in one patient and during stimulation of the supramarginal gyrus in the other patient.

These cases demonstrate a localization of language repetition to the posterior perisylvian cortex. Brain mapping of this region should include assessment of verbal repetition to avoid potential deficits resembling conduction aphasia.

Recent advances in the treatment of oligodendrogliomas

The optimal treatment for patients with oligodendrogliomas is unknown, and current management strategies remain controversial. This past year, further exploration of the molecular genetics of the tumors and its prognostic implications for outcome, evaluation of the utility of positron emission tomography imaging, and the role of radiation and chemotherapy in the treatment of oligodendrogliomas have been reported. It is becoming increasingly apparent that oligodendrogliomas are several distinct diseases on a molecular level, and that key genetic derangements can signify a response to treatment and favorable outcome. The added contributions of recent publications consolidates these emerging impressions. Ultimately, the combination of improved imaging techniques, molecular profiling, and new therapies should result in improved outcome with reduced treatment-related toxicity for patients with newly diagnosed, progressive, and recurrent oligodendrogliomas.

Intraoperative Cortical Mapping Has Low Sensitivity for the Detection of Motor Function in Proximity to a Tumor in the Primary Motor Area

Six patients with brain tumors within or near the primary motor cortex underwent preoperative functional magnetic resonance imaging (fMRI) and intraoperative cortical mapping, and the accuracy of those techniques for localization of the primary motor cortex and motor function beside the tumor were determined by comparison against neuroanatomical correlates from pre-, intra- and postoperative neurological observations. The location of the primary motor cortex was detected by intraoperative cortical mapping in 5 of 6 cases and by fMRI in all 6 cases. Brain mapping provided equivocal information on the cortical representation of motor territories, and with the technique used in close proximity to the tumor, the motor territories were not detected in all but 1 case. In contrast, the areas controlling motor function in close proximity to the tumor were detected by fMRI in 4 of 6 cases. These data indicate that intraoperative cortical mapping has a low sensitivity for the detection of motor function in the area beside the tumor. Therefore, this technique may not be sufficient to prevent compromise of motor areas during tumor resection.

Irm fonctionnelle et oligodendrogliomes

The localization of functional areas obtained from functional MRI (fMRI) is useful for patients suffering from tumors contiguous to eloquent brain areas. fRMI is an efficient tool in the strategy of treatment of low grade oligodendroglioamas in the rolandic area in intact or slightly impaired patients. It can be used preoperatively to assess motor functional areas. Indeed there is a good correlation for motor cortex lesions when using comparison between fMRI and intraoperative findings. Direct integration of fMRI data into neuronavigation enables to better visualize and preserve eloquent brain areas. One must be aware of fMRI limits. It is still often used with the control of direct cortical stimulations.

Mutational study of the 1p located genes p18ink4c, Patched-2, RIZ1 and KIF1B in oligodendrogliomas

Loss of 1p heterozygosity is one of the most characteristic events in oligodendrogliomas. Several genes located in this region have been previously studied to find the target gene implicated in the development of this tumor without success. Patched-2, RIZ1 and KIF1B are novel oncosuppressor genes located at 1p and involved in different kinds of tumors. We have studied these genes and p18(ink4c) using PCR/SSCP methods to detect sequence variations in a series of 40 oligodendrogliomas in which the allelic status at 1p was analyzed. Polymorphisms or no sequence changes were detected in all four genes analyzed. None of the genes analyzed seem to be the target-gene mapped at 1p involved by mutation in oligodendroglioma development.

The dielectric properties of cancerous tissues in a nude mouse xenograft model

The dielectric properties of various cancers, namely brain tumor, breast cancer, gastric carcinoma, and colon cancer, were measured in the frequency range of 500 MHz to 5 GHz. Cancers were cultivated applying the xenograft model of growing human cancerous tissues using the specific pathogen free, homo inbred mouse (a nude mouse). The complex permittivity was measured using an open-ended coaxial probe (HP85070B) and a computer controlled network analyzer (HP8510C). For the measurement of the dielectric properties, a total of 58 xenografted specimens was used. The results showed that measured values of complex permittivity for all four cancerous tissues were similar, with little variations over the frequency range used. It might be agreed that components and characteristics of different cancerous tissues would be similar despite their different occurrences in the human body. It is necessary to investigate this result further.

Magnetic source imaging supports clinical decision making in glioma patients

OBJECTIVE

This study addresses the potential utility of preoperative functional imaging with magnetoencephalography (MEG) for the selection of glioma patients who are likely to benefit from resective surgical treatment regarding postoperative morbidity.

METHODS

One hundred and nineteen patients with gliomas adjacent to sensorimotor, visual and speech related brain areas were investigated preoperatively with a MAGNES II biomagnetometer. In each patient the pre-surgical evaluation was focussed on the visual, sensorimotor cortex and/or of the speech related brain areas. A grading system was then used according to the distance of the MEG activation sources to the nearest tumour border to determine the further treatment. The therapeutic options consisted in conservative treatment, stereotactic biopsy and/or a radiation and chemotherapy, substantial cytoreduction and the gross total removal of the lesion.

RESULTS

From 119 investigated patients, 55 patients (46.2%) were not considered for surgery due to tumour invasion to functional cortex. Sixty four patients (53.8%) were chosen for resective surgery. In the surgical group only four patients (6.2%) suffered from neurological deterioration.

CONCLUSIONS

Magnetic source imaging (MSI) proved to be a valuable help in the clinical decision making process of lesions adjacent to functional important brain areas. The relative high number of patients in whom MSI warns of the postoperative crippling sequelae may lead to a better selection of patients who benefit from resective surgery. This method may help to find the patients for whom conservative treatment seems to be more favourable concerning quality of life in the surviving time.

Advances in the biology and treatment of oligodendrogliomas

PURPOSE OF REVIEW

The sensitivity of oligodendroglioma to chemotherapy and the prognostic significance of combined loss of 1p/19q in these tumors are now well established. This review discusses recent molecular, genetic and clinical advances made in studies on oligodendroglioma and mixed oligoastrocytoma.

RECENT FINDINGS

Methylation of genes is a frequent event in oligodendroglioma (OD), but no specific methylation sites have been discovered. In contrast to earlier reports, the expression of the basic helix-loop-helix transcription factors is not specific for OD, but may occur in glial tumors of all lineages. In a number of studies, the prognostic relevance of 1p/19q loss has been confirmed, and several studies have shown that loss of 1p/19q are early events in OD. No candidate genes have so far been identified on 1p36 and 19q13. Gene expression profiling using gene arrays allows the separation of glial tumors according to histology, tumor grade and prognosis. A number of genes have been identified that are significantly more highly expressed in OD. On MRI imaging, OD with combined 1p/19q loss has typical characteristics, including indistinct borders and a mixed signal intensity on T2-weighted images. Despite the large increase in knowledge on the molecular abnormalities in OD, the therapeutic options for these tumors have not improved significantly since the introduction of temozolomide. The increased survival after chemotherapy has been clearly established, but the timing of chemotherapy seems less critical. It is clear that temozolomide is a good alternative to procarbazine, CCNU and vincristine (PCV) chemotherapy, in particular, because it is better tolerated. No randomized trials, however, have compared PCV-chemotherapy to temozolomide. New agents--and probably more targeted therapies--are needed to further improve treatment. Chemo-irradiation deserves further study in anaplastic OD.

SUMMARY

The progress in the understanding of genetic and molecular abnormalities of OD has improved the recognition of treatment-sensitive OD, although this has not yet been mirrored in improved therapies or new treatment options. While chemotherapy improves the outcome of OD, further improvements will likely require new drugs or new treatment concepts.

Dissecting tumor maintenance requirements using bioluminescence imaging of cell proliferation in a mouse glioma model

Bioluminescence imaging has previously been used to monitor the formation of grafted tumors in vivo and measure cell number during tumor progression and response to therapy. The development and optimization of successful cancer therapy strategies may well require detailed and specific assessment of biological processes in response to mechanistic intervention. Here, we use bioluminescence imaging to monitor the cell cycle in a genetically engineered, histologically accurate model of glioma in vivo. In these platelet-derived growth factor (PDGF)-driven oligodendrogliomas, G1 cell-cycle arrest is generated by blockade of either the PDGF receptor or mTOR using small-molecule inhibitors.

Conventional MR imaging with simultaneous measurements of cerebral blood volume and vascular permeability in ganglioglioma

The conventional MR imaging appearance of gangliogliomas is often variable and nonspecific. Conventional MR images, relative cerebral blood volume (rCBV) and vascular permeability (K(trans)) measurements were reviewed in 20 patients with pathologically proven grade 1 and 2 gangliogliomas (n = 20) and compared to a group of grade 2 low-grade gliomas (n = 30). The conventional MRI findings demonstrated an average lesion size of 4.1 cm, contrast enhancement (n = 19), variable degree of edema, variable mass effect, necrosis/cystic areas (n = 8), well defined (n = 12), signal heterogeneity (n = 9), calcification (n = 4). The mean rCBV was 3.66 +/- 2.20 (mean +/- std) for grade 1 and 2 gangliogliomas. The mean rCBV in a comparative group of low-grade gliomas (n = 30), was 2.14 +/- 1.67. p Value < 0.05 compared with grade 1 and 2 ganglioglioma. The mean K(trans) was 0.0018 +/- 0.0035. The mean K(trans) in a comparative group of low-grade gliomas (n = 30), was 0.0005 +/- 0.001. p Value = 0.14 compared with grade 1 and 2 ganglioglioma. The rCBV measurements of grade 1 and 2 gangliogliomas are elevated compared with other low-grade gliomas. The K(trans), however, did not demonstrate a significant difference. Gangliogliomas demonstrate higher cerebral blood volume compared with other low-grade gliomas, but the degree of vascular permeability in gangliogliomas is similar to other low-grade gliomas. Higher cerebral blood volume measurements can help differentiate gangliogliomas from other low-grade gliomas.

Language functional magnetic resonance imaging in preoperative assessment of language areas: correlation with direct cortical stimulation

OBJECTIVE

The aim of this study was to analyze the usefulness of preoperative language functional magnetic resonance imaging (fMRI), by correlating fMRI data with intraoperative cortical stimulation results for patients with brain tumors.

METHODS

Naming and verb generation tasks were used, separately or in combination, for 14 right-handed patients with tumors in the left hemisphere. fMRI data obtained were analyzed with SPM software, with two standard analysis thresholds (P < 0.005 and then P < 0.05). The fMRI data were then registered in a frameless stereotactic neuronavigational device and correlated with direct brain mapping results. We used a statistical model with the fMRI information as a predictor, spatially correlating each intraoperatively mapped cortical site with fMRI data integrated in the neuronavigational system (site-by-site correlation). Eight patients were also studied with language fMRI postoperatively, with the same acquisition protocol.

RESULTS

We observed high variability in signal extents and locations among patients with both tasks. The activated areas were located mainly in the left hemisphere in the middle and inferior frontal gyri (F2 and F3), the superior and middle temporal gyri (T1 and T2), and the supramarginal and angular gyri. A total of 426 cortical sites were tested for each task among the 14 patients. In frontal and temporoparietal areas, poor sensitivity of the fMRI technique was observed for the naming and verb generation tasks (22 and 36%, respectively) with P < 0.005 as the analysis threshold. Although not perfect, the specificity of the fMRI technique was good in all conditions (97% for the naming task and 98% for the verb generation task). Better correlation (sensitivity, 59%; specificity, 97%) was achieved by combining the two fMRI tasks. Variation of the analysis threshold to P < 0.05 increased the sensitivity to 66% while decreasing the specificity to 91%. Postoperative fMRI data (for the cortical brain areas studied intraoperatively) were in accordance with brain mapping results for six of eight patients. Complete agreement between pre- and postoperative fMRI studies and direct brain mapping results was observed for only three of eight patients.

CONCLUSION

With the paradigms and analysis thresholds used in this study, language fMRI data obtained with naming or verb generation tasks, before and after surgery, were imperfectly correlated with intraoperative brain mapping results. A better correlation could be obtained by combining the fMRI tasks. The overall results of this study demonstrated that language fMRI could not be used to make critical surgical decisions in the absence of direct brain mapping. Other acquisition protocols are required for evaluation of the potential role of language fMRI in the accurate detection of essential cortical language areas.

Oligodendroglioma: clinical profile and treatment results

Oligodendrogliomas are rare glial tumors with a long natural history. Radical surgery, postoperative radiotherapy, chemotherapy and observation have been suggested as part of primary management. This series reports the presentation and outcome in 34 patients with histologically verified pure oligodendrogliomas treated between 1983 and 1993. All patients were treated at the time of initial diagnosis with surgery, with or without additional radiotherapy. The overall survival and progression free survival rates at five years were 69.8% and 55% respectively. There was no tumor or treatment related factor influencing survival significantly.

Oligodendrogliomas with neurocytic differentiation. A report of 4 cases with diagnostic and histogenetic implications

Oligodendroglioma represents a distinct type of diffuse glioma with a relatively favorable prognosis. Although an O2A-like glial progenitor cell of origin has been suggested, a neuronal-oligodendroglial progenitor cell is also of interest, particularly because variable degrees of neuronal marker expression have been reported in typical oligodendrogliomas. We present 2 female and 2 male patients (ages 34-54) with frontal lobe oligodendrogliomas containing a) morphologically distinct collections of small round cells with hyperchromatic nuclei, b) well-formed Homer Wright-like and perivascular rosettes, and c) demonstrable neuronal differentiation by immunohistochemistry and/or electron microscopy in the rosette-associated regions. Unlike extraventricular neurocytomas, these cases featured an infiltrative growth pattern and a classic oligodendroglioma immunophenotype in non-rosette bearing portions of each tumor. FISH analysis demonstrated chromosome 1p and 19q codeletions in 3 (75%) cases, both in regions with and without rosettes. Recurrences were common, although all patients are currently alive 4 months to 13 yr from initial diagnosis. Based on clinicopathologic and genetic features, we diagnosed these tumors as oligodendrogliomas with neurocytic differentiation. However, it is unclear whether they represent a) gliomas with divergent neuronal differentiation, b) a distinctive form of glioneuronal neoplasm, or c) a reflection of glioneuronal histogenesis in oligodendrogliomas in general. In any case, their occurrence suggests a histogenetic overlap between oligodendroglioma and extraventricular neurocytoma not previously recognized.

Molecular markers that identify human astrocytomas and oligodendrogliomas

The classification of human gliomas is currently based solely on neuropathological criteria. Prognostic and therapeutic parameters are dependent upon whether the tumors are deemed to be of astrocytic or oligodendroglial in origin. We sought to identify molecular reagents that might provide a more objective parameter to assist in the classification of these tumors. In order to identify mRNA transcripts for genes normally transcribed exclusively by oligodendrocytes. Northern blot analysis was carried out on RNA samples from 138 human gliomas. Transcripts encoding the myelin basic protein (MBP) were found in an equally high percentage of tumors that by neuropathological criteria were either astrocytic or oligodendroglial. In contrast, proteolipid protein (PLP) and cyclic nucleotide phosphodiesterase (CNP) mRNA molecules were found significantly more often in oligodendrogliomas than in astrocytomas. The strongest association with histological typing was found with the transcript for the myelin galactolipid biosynthetic enzyme UDP-galactose: ceramide galactosytransferase (CGT), which was about twice as frequently detected in tumors of oligodendroglial type. Results of glycolipid analyses were previously reported on a subset of the tumors studied herein. Statistical analyses of both molecular and biochemical data on this subset of astrocytomas, oligoastrocytomas, and oligodendrogliomas were performed to determine if a panel of markers could be used to separate astrocytic and oligodendroglial tumors. The presence of asialo GM1 (GA1) and the absence of paragloboside occurred most frequently in oligodendrogliomas. Ceramide monohexoside (CMH) levels correlated highly with the expression of mRNA for 4 myelin proteins: CGT, MBP, CNP, and PLP. The best combination of 2 markers of oligodendroglial tumors was CGT and GA1; the best combination of 3 markers was the presence of CGT, GA1, and the absence of paragloboside. We conclude that this combination of markers could be useful in distinguishing between astrocytic and oligodendroglial tumors.

Histopathological-molecular genetic correlations in referral pathologist-diagnosed low-grade "oligodendroglioma"

Allelic loss of chromosome 1p predicts increased chemosensitivity and better survival in oligodendroglial tumors. Clinical testing for 1p loss in oligodendroglial tumors at our hospital has allowed us to postulate that certain histological appearances are associated with 1p allelic status. Forty-four cases received for genetic testing were diagnosed by referring pathologists as pure low-grade oligodendroglioma. Central neuropathological review divided the series equally into 22 cases with classical oligodendroglioma histology and 22 with more astrocytic features. Molecular genetic analyses demonstrated 1p loss in 19 of 22 classic oligodendrogliomas (86%) and maintenance of both 1p alleles in 16 of 22 gliomas with astrocytic features (73%). No glial fibrillary acidic protein-positive cell type (gliofibrillary oligodendrocyte, minigemistocyte, cellular processes) was associated with 1p allelic status. Fourteen of the 44 cases were treated with chemotherapy at tumor progression: 3 "astrocytic" gliomas with 1p loss responded to PCV chemotherapy and 2 classic oligodendrogliomas that maintained both 1p alleles included a responder and a non-responder. These results suggest that histological appearance correctly predicts genotype in approximately 80% of low-grade gliomas, but that tumor genotype more closely predicts chemosensitivity. As a result, such objective molecular genetic analyses should be incorporated into patient management and into clinical trials of low-grade diffuse gliomas.

Survivin inhibition induces human neural tumor cell death through caspase-independent and -dependent pathways

Survivin inhibits apoptosis during development and carcinogenesis and is absent in differentiated cells. To determine whether survivin inhibition induces cell death in neural tumor cells, survivin antisense oligonucleotides (SAO) were administered to a human neuroblastoma (MSN) and an oligodendroglioma (TC620) resulting in a dose-dependent reduction in survivin protein. Although 74% of the SAO-treated MSN cells were trypan blue(+), PARP cleavage or activated caspase-3 was not observed. However nuclear translocation of AIF occurred and XIAP increased dramatically. Co-administration of z-Val-Ala-Asp(OMe)-fluoromethyl ketone (zVAD-fmk) with SAO did not inhibit cell death suggesting a caspase-independent mechanism of cell death. Propidium iodide (PI) staining revealed multiple large macronuclei with no apoptotic bodies supporting a role for survivin in cell division. By contrast, while 70% of the SAO-treated TC620 cells were trypan blue(+), PARP was cleaved, cells were TUNEL(+) and PI-staining revealed macronuclei and numerous apoptotic bodies. Co-treatment of the TC620 cells with SAO and zVAD-fmk blocked cell death. While no macronuclei or apoptotic bodies were observed there was a two-fold increase in metaphase cells. Our results suggest that survivin inhibition decreases the viability of human neural tumor cells and as a result of mitotic catastrophe, cell death can be initiated by either a classic apoptotic mechanism or a caspase-independent mechanism.

Temozolomide chemotherapy in recurrent oligodendroglioma

The authors determined the tolerance, response rate, and duration of recurrent anaplastic oligodendroglioma in 30 patients to temozolomide given orally at 150 to 200 mg/m2 on days 1 through 5 in cycles of 28 days. Nine patients responded: 7 of 27 patients (26%) treated with temozolomide after prior PCV chemotherapy and 2 of 3 chemotherapy-naive patients (both complete response). Median time to progression in responding patients was 13 months. Temozolomide shows promise and has an acceptable safety profile in recurrent anaplastic oligodendroglial tumors. Patients not responding to PCV may respond to temozolomide.

Expression of hypoxia-inducible factor-1 alpha in oligodendrogliomas: its impact on prognosis and on neoangiogenesis

BACKGROUND

Hypoxia-inducible factor (HIF)1 alpha is considered to play a key role in the adaptation of cells to hypoxia by stimulating angiogenesis via regulation of vascular endothelial growth factor and by metabolic adaptation to O(2) deprivation.

METHODS

Expression of HIF-1 alpha protein and p53 was investigated by immunohistochemistry in 51 specimens of supratentorial pure oligodendrogliomas. Microvessels density (MVD) was determined by anti-CD34 immunostaining. The influence of HIF-1 alpha expression on survival was investigated using univariate and multivariate analysis.

RESULTS

Strong expression of HIF-1 alpha was observed in 12 (23.5%) specimens, moderate in 21 (41.2%) specimens, and weak in 8 (15.7%) cases, and no expression was found in 10 samples (19.6%). There was no correlation of HIF-1 alpha expression with histologic grading (P = 0.428, Mann-Whitney test). Hypoxia-inducible factor-1 alpha expression and MVD showed a strong correlation (P < 0.001, r = 0.735, Spearman coefficient of correlation). Overexpression of p53 was observed in only two cases. Patients with strong or moderate expression of HIF-1 alpha had a significantly shorter overall survival rate compared with those with low or no expression in univariate (P = 0.0434; log-rank test) and multivariate analysis (P = 0.0187).

CONCLUSIONS

Overexpression of HIF-1 alpha indicates a diminished prognosis in oligodendrogliomas, independent of p53 status. This finding may be explained by the strong vascularization of these tumors that prevents hypoxia and allows O(2) diffusion and henceforth tumor progression.

Biology of oligodendrocyte and myelin in the mammalian central nervous system

Oligodendrocytes, the myelin-forming cells of the central nervous system (CNS), and astrocytes constitute macroglia. This review deals with the recent progress related to the origin and differentiation of the oligodendrocytes, their relationships to other neural cells, and functional neuroglial interactions under physiological conditions and in demyelinating diseases. One of the problems in studies of the CNS is to find components, i.e., markers, for the identification of the different cells, in intact tissues or cultures. In recent years, specific biochemical, immunological, and molecular markers have been identified. Many components specific to differentiating oligodendrocytes and to myelin are now available to aid their study. Transgenic mice and spontaneous mutants have led to a better understanding of the targets of specific dys- or demyelinating diseases. The best examples are the studies concerning the effects of the mutations affecting the most abundant protein in the central nervous myelin, the proteolipid protein, which lead to dysmyelinating diseases in animals and human (jimpy mutation and Pelizaeus-Merzbacher disease or spastic paraplegia, respectively). Oligodendrocytes, as astrocytes, are able to respond to changes in the cellular and extracellular environment, possibly in relation to a glial network. There is also a remarkable plasticity of the oligodendrocyte lineage, even in the adult with a certain potentiality for myelin repair after experimental demyelination or human diseases.

Promoter hypermethylation and homozygous deletion of the p14ARF and p16INK4a genes in oligodendrogliomas

The INK4a/ARF locus on chromosome 9p21 encodes two gene products that are involved in cell cycle regulation through inhibition of CDK4-mediated RB phosphorylation (p16INK4a) and binding to MDM2 leading to p53 stabilization (p14ARF). The locus is deleted in up to 25% of oligodendrogliomas and 50% of anaplastic oligodendrogliomas, but little is known on the frequency of gene silencing by DNA methylation. We assessed promoter hypermethylation of p14ARF and p16INK4a using methylation-specific PCR, and homozygous deletion of the p14ARF and p16INK4a genes by differential PCR in 29 oligodendrogliomas (WHO grade II) and 20 anaplastic oligodendrogliomas (WHO grade III). Promoter hypermethylation of the p14ARF gene was detected in 6/29 (21%) oligodendrogliomas and 3/20 (15%) anaplastic oligodendrogliomas. None of the oligodendrogliomas and only 1 out of 20 anaplastic oligodendrogliomas showed hypermethylation of p16INK4a. Homozygous deletion was not detected in any of the WHO grade II oligodendrogliomas but was present in 5/20 (25%) anaplastic oligodendrogliomas and always affected both genes. In one tumor containing distinct areas with and without anaplasia, p14ARF hypermethylation was detected in the WHO grade II area, while homozygous co-deletion of p14ARF and p16INK4a was found in the region with anaplastic features (grade III). These data suggest that aberrant p14ARF expression due to hypermethylation is the earliest INK4a/ARF change in the evolution of oligodendrogliomas, while the presence of p14ARF and p16INK4a deletions indicates progression to anaplastic oligodendroglioma.

Functional reorganization of motor cortex due to brain tumor: a case report

We report the case of a 39-year-old man with a brain tumor and 12 years of intractable partial epilepsy with secondary generalization. After extensive noninvasive and invasive evaluation the seizure focus was localized to the right fronto-parietal region. Functional cortical mapping (FCM) was performed after craniotomy and implantation of a subdural grid with 40 electrodes covering the epileptogenic focus and the adjacent cortex. A Grass Model S12 Stimulator was used to deliver gradual increments of current and stimulus duration with fixed frequency of 10 Hz and pulse duration of 500 microsec for defining eloquent cortex next to the seizure focus. FCM demonstrated cortical representation of eye anterior to and hand posterior and inferior to expected locations on the motor cortex compared to the classical homunculus. Subsequently, he underwent resection of an oligodendroglioma. This case demonstrates that the brain undergoes reorganization of cortical motor representation as a result of pathological lesions in the brain.

Ezrin immunoreactivity is associated with increasing malignancy of astrocytic tumors but is absent in oligodendrogliomas

The actin-binding protein ezrin has been associated with motility and invasive behavior of malignant cells. To assess the presence of this protein in human glial cells of the brain and its potential role in benign and malignant glial tumors, we studied ezrin immunoreactivity (IR), proliferation (MIB-1-IR), and apoptosis (terminal dUTP nick-end labeling) in normal human brain tissues from 10 autopsies and tissues from 115 cases of human glial tumors including astro-cytomas, ependymomas, oligodendrogliomas, and glioblastomas. We found weak staining of peripheral processes in normal human brain astrocytes and in World Health Organization grade II benign astrocytomas. Staining was markedly increased in anaplastic astrocytomas (World Health Organization grade III) and clearly strongest in glioblastomas (World Health Organization grade IV). The increase of ezrin-IR correlated significantly with increasing malignancy of astrocytic tumors (P < 0.0001). Statistical analysis revealed a stronger association with increasing malignancy for ezrin-IR than for MIB-1-IR or terminal dUTP nick-end labeling staining. Ezrin-IR was absent in normal oligodendrocytes and in oligodendrogliomas, but pronounced in normal ependymal cells and ependymomas. Ezrin-IR seems to be specific for astrocytes and ependymal glia in the normal brain. Our results indicate that ezrin-IR may provide a useful tool for the distinction of oligodendrogliomas and astrocytomas and for the grading of astrocytic tumors.

Magnetic source imaging in stereotactic and functional neurosurgery

Magnetic source imaging (MSI) combines the unique spatial and temporal functional accuracy of magnetoencephalography (MEG) with the anatomic and pathologic detail of magnetic resonance (MR). This relatively new method of evaluating brain function provides a preoperative mapping of brain function and brain structure by integrating the functional information of MEG with the structural information of MR. This results in data on actual neuronal interactions in clinical patients. The temporal and spatial accuracy of the MEG data, combined with the anatomic and pathologic specificity of MRI, results in the magnetic source image, which offers accurate knowledge of cortical functional organization, and is important in the surgical treatment of brain neoplasms, vascular malformations, and epilepsy. MSI allows the tracking of neuronal activity on the scale of milliseconds with millimeter accuracy, and continues to lead to new understanding of many functional brain disorders.

Analysis of proliferation and apoptosis in brain gliomas: prognostic and clinical value

With the introduction of new (immuno-)histochemical techniques it is now possible to assess rates of proliferation and apoptosis in brain gliomas using archival paraffin embedded material. As proliferation and apoptosis are related to tumour growth rate quantification of these processes has prognostic value and is related to tumour grading. In this study we assessed the proliferation rate by measuring the Ki-67 labelling index using the MIB-1 antibody (MIB-LI) and the apoptotic rate using the in situ labelling of DNA strand breaks with TUNEL (TUNEL-LI) in 315 supratentorial gliomas. MIB-LI and TUNEL-LI in astrocytomas (A) where significantly lower compared to anaplastic astrocytomas (AA), glioblastomas (GBM) and oligodendroglial tumours [oligodendrogliomas (O) and anaplastic oligodendrogliomas (AO)]. MIB-LI and TUNEL-LI were significantly lower in AA compared to GBM. In astrocytic tumours MIB-LI and TUNEL-LI appeared to be correlated. As the distinction between A and AA is of clinical value but can be difficult histomorphologically we analysed the prognostic value of MIB-LI and TUNEL-LI in gliomas with particular emphasis on A and AA. MIB-LI below 10% was of prognostic value in A and AA, O and AO but not in GBM on univariate survival analysis. TUNEL-LI was of no prognostic value. With multivariate survival analysis MIB-LI lost prognostic significance in O and AO. Astrocytomas with a gemistocytic component (AG) are similar to A with respect to survival and MIB-LI and TUNEL-LI. MIB-LI is of independent prognostic value in A and AA. Assessment of MIB-LI in A and AA can be used as an aid in distinguishing A and AA.

Correspondence between functional magnetic resonance imaging somatotopy and individual brain anatomy of the central region: comparison with intraoperative stimulation in patients with brain tumors

OBJECT

The goal of this study was to determine the somatotopical structure-function relationships of the primary motor cortex in individual patients by using functional magnetic resonance (fMR) imaging. This was done to assess whether there is a displacement of functional areas compared with anatomical landmarks in patients harboring brain tumors close to the central region, and to validate these findings with intraoperative cortical stimulation.

METHODS

One hundred twenty hemispheres in 60 patients were studied by obtaining blood oxygen level-dependent fMR images in patients while they performed movements of the foot, hand, and face on both sides. There was a good correspondence between anatomical landmarks in the deep portion of the central sulcus on axial slices and the somatotopical organization of primary motor areas. Pixels activated during hand movements were centered on a small characteristic digitation; those activated during movements in the face and foot areas were located in the lower portion of the central sulcus (lateral to the hand area) and around the termination of the central sulcus, respectively. In diseased hemispheres, signal-intensity changes were still observed in the projection of the expected anatomical area. The fMR imaging data mapped intraoperative electrical stimulation in 92% of positive sites.

CONCLUSIONS

There was a high correspondence between the somatotopical anatomy and function in the central sulcus, which was similar in normal and diseased hemispheres. The fMR imaging and electrical stimulation data were highly concordant. These findings may enable the neurosurgeon to locate primary motor areas more easily during surgery.

Acquired procedural dyscalculia associated to a left parietal lesion in a child

We report the case of an 11-year-old boy who developed an anarithmetia in association with a left temporo-parietal tumor. His oral and written language were normal as well as his ability to judge magnitudes, process numbers, read operation signs and retrieve number facts. He had a specific difficulty in performing the procedures of subtraction, especially when it involved borrowing. These skills had been mastered before the present illness. This case shows that the components of calculation can be dissociated by brain lesions sustained during childhood, while arithmetic abilities are being acquired, thus reinforcing findings from developmental dyscalculias, that suggest a modular organisation of those skills during development.

Expression of Bcl-2 and Bax in oligodendrogliomas and their relationship to apoptosis

Apoptotic bodies are frequently found in oligodendrogliomas, particularly in the anaplastic subtype. A range of proteins, such as those of the Bcl family, are implicated in the control of apoptosis. The ratio of antagonists of apoptosis, such as Bcl-2, to agonists, such as Bax, is thought to determine the outcome for a particular cell. This study aimed to determine the expression of Bcl-2 and Bax proteins in a series of oligodendrogliomas and to relate the expression of these to measures of apoptosis. Immunohistochemistry was used to detect the expression of Bcl-2 and Bax in an archival series of 32 oligodendrogliomas. The results were scored semiquantitatively for the extent and intensity of tumour staining. Apoptosis indices were determined by counting apoptotic bodies on haematoxylin and eosin staining and the percentage of cells showing a positive reaction with the TdT-mediated dUTP-biotin nick end-labelling technique (TUNEL). Granular cytoplasmic staining for Bcl-2 was seen in tumour cells in 81% of cases. Cases with a strong intensity (but not extent) of staining showed a lower TUNEL index (P=0.038). Bcl-2 expression was identified in the walls of intratumoural blood vessels in 55% of cases and in peri-tumoural neurones (where present) in 87%. Bax expression was detected in tumour cells in 69% of cases but no relationship to TI was detected. Bax positivity was seen in blood vessels in 44% of cases and peri-tumoural neurones in 60%. Bcl-2 and Bax were concluded to be expressed in a high proportion of oligodendrogliomas, suggesting that they may exert a regulatory role in cell death in these tumours.

Intraoperative validation of functional magnetic resonance imaging and cortical reorganization patterns in patients with brain tumors involving the primary motor cortex

OBJECT

The purpose of the present study was to compare the results of functional magnetic resonance (fMR) imaging with those of intraoperative cortical stimulation in patients who harbored tumors close to or involving the primary motor area and to assess the usefulness of fMR imaging in the objective evaluation of motor function as part of the surgical strategy in the treatment of these patients.

METHODS

A total of 11 consecutive patients, whose tumors were close to or involving the central region, underwent presurgical blood oxygen level-dependent fMR imaging while performing a motor paradigm that required them to clench and spread their hands contra- and ipsilateral to the tumor. Statistical cross-correlation functional maps covering the primary and secondary motor cortical areas were generated and overlaid onto high-resolution anatomical MR images. Intraoperative electrical cortical stimulation was performed to validate the presurgical fMR imaging findings. In nine (82%) of 11 patients, the anatomical fMR imaging localization of motor areas could be verified by intraoperative electrical cortical stimulation. In seven patients two or more activation sites were demonstrated on fMR imaging, which were considered a consequence of reorganization phenomena of the motor cortex: contralateral primary motor area (nine patients), contralateral premotor area (four patients), ipsilateral primary motor area (two patients), and ipsilateral premotor area (four patients).

CONCLUSIONS

Functional MR imaging can be used to perform objective evaluation of motor function and surgical planning in patients who harbor lesions near or involving the primary motor cortex. Correlation between fMR imaging findings and the results of direct electrical brain stimulation is high, although not 100%. Based on their study, the authors believe that cortical reorganization patterns of motor areas might explain the differences in motor function and the diversity of postoperative motor function among patients with central tumors.

Blood flow and metabolism of oligodendrogliomas: a positron emission tomography study with kinetic analysis of 18F-fluorodeoxyglucose

To accurately characterize the pathophysiology and proliferating activity of oligodendrogliomas, we studied cerebral blood flow and metabolism using positron emission tomography (PET) in five patients with this tumor. Regional cerebral blood flow (rCBF), cerebral blood volume (rCBV), oxygen extraction fraction (rOEF), and cerebral metabolic rates of oxygen (rCMRO2) and of glucose (rCMRGl) were quantitatively measured in tumor lesions and the contralateral gray matter, rCMRGl was analyzed based on both kinetic and autoradiographic methods. Tumor rCBF and rCBV were lower than in the contralateral gray matter in all preoperatively examined patients. Oxygen metabolism, determined by rCMRO2 and rOEF, was consistently reduced in the tumor (rCMRO2, P<0.05 vs. gray matter, determined by the Student's t-test). Tumor rCMRGl was significantly lower than the gray matter rCMRGl in both kinetic (P<0.01) and autoradiographic (P<0.05) analyses. Kinetic tumor rCMRGl varied between 1.22 and 4.13 mg/100 ml/min, but was lower than the gray matter value in all patients. Autoradiographic tumor rCMRGl, which ranged from 1.02 to 5.79 mg/100 ml/min, was also reduced in all tumors but one; the remaining tumor, which had a relatively high value of autoradiographic rCMRGl (comparable to gray matter rCMRGl), infiltrated the contralateral hemisphere through the corpus callosum, and was characterized by high cellular density. In one patient who suffered from tumor recurrence 8 years and 10 months after initial treatment, phosphorylation constant (K3) and kinetic rCMRGl of the recurring tumor were higher than those of the original tumor. No other tumors have regrown or recurred during the postoperative follow-up periods, which ranged from 22 to 130 months (median = 101 months). Circulation and metabolism measured by PET provide in vivo biological characteristics, including proliferating activity, in oligodendrogliomas.

Cell cycle and proliferation markers in neuroepithelial tumors

Cell proliferation is characteristic, though non specific, of tumors. The cell cycle is regarded as a clock with ordered activation of protein complexes triggering initiation and advancement through checkpoints. The cell cycle and its control mechanisms are briefly described herein focusing on neuroepithelial tumors. The assessment of cell proliferation in brain tumors is a very important tool in diagnosis and especially in prognosis. It can be performed by different methods: counting mitoses, calculating the labeling index (Ll) of [3H] Thymidine, BrdU, Ki-67, MIB.1, PCNA, cytometry and AgNORs. Each method has its advantages and disadvantages. The main obstacles to the usefulness of different Lls in establishing prognosis in individual cases are sampling error, heterogeneity of the proliferation potential of brains tumors and the wide overlapping of Ll ranges between classic and anaplatic variants. The principal findings are critically described and commented upon.

Action potential-generating cells in human glioblastomas

We studied the electrophysiological properties of cells from human glioblastomas obtained after surgery. The membrane currents were compared in cells of acute tissue slices and primary cultures using the whole cell mode of the patch-clamp technique. Very strikingly, in about a third of the tumor cells in situ and in vitro, depolarizing voltage steps elicited large, tetrodotoxin-sensitive inward currents with a threshold of about -30 mV, indicating the presence of voltage-gated sodium channels. In addition, three types of potassium currents, a delayed rectifying, an A-type, and an inward rectifying, were observed. Such a set of voltage-gated channels is characteristic for neurons. Indeed, in these glioblastoma cells, depolarizing current pulses in the current clamp mode were able to generate action potentials with properties similar to those observed in neurons. We interpret this finding as the ability of glioblastoma cells to acquire neuronlike properties but retain some glial features, since they still express markers typical for astrocytes and their precursors. The role of sodium channels in glioblastoma cells is unclear at this moment and needs further investigation. Our findings, however, imply that the tumor tissue can be intrinsically excitable and that neoplastic glial cells themselves may be an etiologic factor for epileptic seizures.

The in vivo metabolic pattern of low-grade brain gliomas: a positron emission tomographic study using 18F-fluorodeoxyglucose and 11C-L-methylmethionine

OBJECTIVE

The object of the present study was to identify metabolic differences between low-grade astrocytomas and oligodendrogliomas and to improve their diagnosis and noninvasive assessment, because both types of tumors look very similar from the point of view of clinical and radiological data (as assessed by computed tomography and magnetic resonance imaging).

METHODS

Before any aggressive treatment, 22 patients with primary low-grade gliomas (astrocytomas in 12 patients and oligodendrogliomas in 10) were investigated with positron emission tomography for both glucose metabolism (18F-fluorodeoxyglucose) and amino acid uptake (11C-L-methylmethionine). An original software that allows a full metabolic analysis of the tumor region of interest (defined from the T1-weighted magnetic resonance image) and compares tumor tissue uptake tracer concentrations with average healthy tissue values has been implemented for data processing. Heterogeneity of each individual tumor has been taken into account and was expressed in histograms, which provided data about the mean and also extreme and intermediate values of tracer concentrations and the way these values are distributed among the full tumor mass.

RESULTS

It has been shown that both tumor types exhibit a glucose hypometabolism (slightly more pronounced with astrocytomas), whereas they strongly differ in methionine uptake, which is high in all oligodendrogliomas and either decreased, normal, or moderately increased in astrocytomas. This latter metabolic difference between both tumor populations may be partially explained by their different cell densities.

CONCLUSION

This study suggests that despite similar radiological and clinical presentations, these two kinds of low-grade gliomas are metabolically different and could therefore have specific responses to different therapies. Moreover, their in vivo metabolic follow-up with positron emission tomography should rely on different parameters, depending on their histological type; methionine uptake may be more relevant than glucose metabolism in the follow-up of oligodendrogliomas.

Tumors of Heschl's gyrus: report of two cases

OBJECTIVE AND IMPORTANCE

The clinical presentation and treatment of patients with lesions involving Heschl's gyrus is reported. Intraoperative bipolar cortical stimulation mapping of Heschl's gyrus has not been previously reported. Only monopolar stimulation of this region (with potential electrical recruitment of large areas of surrounding cortex) has been undertaken.

CLINICAL PRESENTATION

Two patients with intrinsic brain tumors located in Heschl's gyrus, in the hemisphere dominant for speech, presented with interictal or ictal auditory changes.

INTERVENTION

Craniotomies were performed with the patients awake and with intraoperative bipolar cortical stimulation mapping of language cortex and of Heschl's gyrus.

CONCLUSION

In contrast to previous studies using monopolar cortical stimulation, auditory changes were not elicited by stimulation. In one of the patients, a persistent interictal ringing sound stopped abruptly during lesion resection. Neither patient had essential temporal lobe language cortex near the lesion. Lesions in Heschl's gyrus can be identified by clinical presentation and magnetic resonance imaging. Based on topographic anatomy, cytoarchitecture, and functional mapping data, these lesions may be resectable without language or auditory mapping, although further experience will be necessary to confirm this observation.

Prognostic factors in oligodendrogliomas

An outcome analysis was performed on 96 patients with pure cerebral oligodendrogliomas operated in the 30-year period 1962 to 1991. The most important predictive prognostic factors were youth and no neurological deficit, demonstrated as a median survival for the group younger than 20 years of 17.5 years and for the group older than 60 years of 13 months. The group without neurological deficits had a 5-years survival of 43 per cent while the group with deficits had a 5-years survival of 5 per cent. The 5-years survival for oligodendroglioma of grade II was 46 per cent and for grade III 10 per cent. We found no effect of radiotherapy on survival, neither in the whole material or in any subgroup.

Circling seizures

Twelve cases with circling seizures are presented with their clinical, electroencephalographic and radiological findings. Four patients had symptomatic partial epilepsy, five had cryptogenic partial epilepsy, and the remaining three had idiopathic generalized epilepsy. Three of the patients with symptomatic partial epilepsy had frontal lesion, and one had parito-occipital lesion. Turning direction had no lateralizing value in patients with partial epilepsy. Based on our study we conclude that circling seizures may occur in different epileptic syndromes and epilepsies. In cases with symptomatic partial epilepsy, lesions are mostly located in frontal lobes but also in parietooccipital areas.

The effects of verapamil and flunarizine on epileptiform activity induced by bicuculline and low Mg2+ in neocortical tissue of epileptic and primary non-epileptic patients

In human neocortical slices the specific L-type calcium channel blocker verapamil had been shown to be antiepileptic in the low Mg(2+)-model of epilepsy. The present investigation demonstrated: (1) verapamil exerted also an antiepileptic effect on epileptiform field potentials (EFP) induced by the GABAA-antagonist bicuculline. (2) The unspecific calcium channel modulator flunarizine, which in contrast to verapamil penetrates the blood-brain barrier, depressed EFP in the low Mg(2+)-model and in the bicuculline model. (3) There was no significant difference in the antiepileptic efficacy of verapamil and flunarizine in epileptic (epilepsy surgery) and primary non-epileptic (tumor surgery) neocortical slices.

Functional magnetic resonance imaging mapping of the motor cortex in patients with cerebral tumors

OBJECTIVE

The purpose of this study was to determine the usefulness of functional magnetic resonance imaging (FMRI) to map cerebral functions in patients with frontal or parietal tumors.

METHODS

Charts and images of patients with cerebral tumors or vascular malformations who underwent FMRI with an echoplanar technique were reviewed. The FMRI maps of motor (11 patients), tactile sensory (12 patients), and language tasks (4 patients) were obtained. The location of the FMRI activation and the positive responses to intraoperative cortical stimulation were compared. The reliability of the paradigms for mapping the rolandic cortex was evaluated.

RESULTS

Rolandic cortex was activated by tactile tasks in all 12 patients and by motor tasks in 10 of 11 patients. Language tasks elicited activation in each of the four patients. Activation was obtained within edematous brain and adjacent to tumors. FMRI in three cases with intraoperative electrocortical mapping results showed activation for a language, tactile, or motor task within the same gyrus in which stimulation elicited a related motor, sensory, or language function. In patients with > 2 cm between the margin of the tumor, as revealed by magnetic resonance imaging, and the activation, no decline in motor function occurred from surgical resection.

CONCLUSIONS

FMRI of tactile, motor, and language tasks is feasible in patients with cerebral tumors. FMRI shows promise as a means of determining the risk of a postoperative motor deficit from surgical resection of frontal or parietal tumors.