Optimizing MR imaging detection of type 2 focal cortical dysplasia: best criteria for clinical practice

BACKGROUND AND PURPOSE

Type 2 FCD is one of the main causes of drug-resistant partial epilepsy. Its detection by MR imaging has greatly improved surgical outcomes, but it often remains overlooked. Our objective was to determine the prevalence of typical MR imaging criteria for type 2 FCD, to provide a precise MR imaging pattern, and to optimize its detection.

MATERIALS AND METHODS

We retrospectively reviewed 1.5T MR imaging of 71 consecutive patients with histologically proved type 2 FCD. The protocol included millimetric 3D T1-weighted, 2D coronal and axial T2-weighted, and 2D or 3D FLAIR images. Two experienced neuroradiologists looked for 6 criteria: cortex thickening, cortical and subcortical signal changes, blurring of the GWM interface, the "transmantle" sign, and gyral abnormalities. The frequency of each sign and their combination were assessed. We compared the delay between epilepsy onset and surgery, taking into account the time of type 2 FCD detection by MR imaging.

RESULTS

Only 42 patients (59%) had positive MR imaging findings. In this group, a combination of at least 3 criteria was always found. Subcortical signal changes were constant. Three characteristic signs (cortical thickening, GWM blurring, and transmantle sign) were combined in 64% of patients, indicating that MR imaging can be highly suggestive. However, typical features of type 2 FCD were overlooked on initial imaging in 40% of patients, contributing to a delay in referral for surgical consideration (17 versus 11.5 years when initial MR imaging findings were positive).

CONCLUSIONS

A combination of 3 major MR imaging signs allows type 2 FCD to be recognized in clinical practice, thereby enabling early identification of candidates for surgery.

FDG-PET improves surgical outcome in negative MRI Taylor-type focal cortical dysplasias

OBJECTIVE

To determine the diagnostic accuracy and prognostic value of ¹⁸FDG-PET in a recent series of patients operated for intractable partial epilepsy associated with histologically proven Taylor-type focal cortical dysplasia (TTFCD) and negative MRI.

METHODS

Of 23 consecutive patients (12 male, 7-38 years old) with negative 1.5-Tesla MRI, 10 exhibited subtle nonspecific abnormalities (e.g., unusual sulcus depth or gyral pattern) and the 13 others had strictly normal MRI. FDG-PET was analyzed both visually after coregistration on MRI and using SPM5 software. Metabolic data were compared with the epileptogenic zone (EZ) determined by stereo-EEG (SEEG) and surgical outcome.

RESULTS

Visual PET analysis disclosed a focal or regional hypometabolism in 18 cases (78%) corresponding to a single gyrus (n = 9) or a larger cortical region (n = 9). PET/MRI coregistration detected a partially hypometabolic gyrus in 4 additional cases. SPM5 PET analysis (n = 18) was concordant with visual analysis in 13 cases. Location of PET abnormalities was extratemporal in all cases, involving eloquent cortex in 15 (65%). Correlations between SEEG, PET/MRI, and histologic findings (n = 20) demonstrated that single hypometabolic gyri (n = 11) corresponded to EZ and TTFCD, which was localized at the bottom of the sulcus. Larger hypometabolic areas (n = 9) also included the EZ and the dysplastic cortex but were more extensive. Following limited cortical resection (mean follow-up 4 years), seizure freedom without permanent motor deficit was obtained in 20/23 patients (87%).

CONCLUSIONS

¹⁸FDG-PET coregistered with MRI is highly sensitive to detect TTFCD and greatly improves diagnosis and surgical prognosis of patients with negative MRI.

[Criteria of diagnosis and grading of oligodendrogliomas or oligo-astrocytomas according to the WHO and Sainte-Anne classifications]

Two main classification systems are used in France for the histological typing and grading of oligodendrogliomas: the WHO and Sainte-Anne Hospital (SA) classifications. According to the WHO, the typing of diffuse gliomas is based on the predominant cell type, oligodendroglial versus astrocytic. In contrast, the SA classification is based on the distinction of two patterns of tumor growth, solid tumor tissue versus isolated tumor cells and also relies on imaging and clinical features. According to this approach, the SA classification includes in the category of oligodendrogliomas, the fibrillary or gemistocytic diffuse astrocytomas (WHO grade II) as well as a substantial proportion of astrocytomas WHO grade III, 2) the WHO uses multiple histological criteria for the grading of oligodendrogliomas (grade II versus grade III), including the degree of differentiation, cellular atypia, mitotic activity and necrosis. In contrast, the SA grading of these tumors (grade A versus B) only uses two criteria: the presence or absence of endothelial hyperplasia, and the presence or absence of contrast enhancement. This last criterion allows overcoming the problems related to the representativeness of surgical samples. Difficulties and discrepancies regarding the diagnosis of oligodendrogliomas are in part due to the lack of immunomarker for the identification of tumoral oligodendrocytes. The potential interest of new markers of oligodendroglial precursors for the diagnosis of these tumors will further be discussed.

[Spatial delimitation of low grade oligodendrogliomas]

Image-guided surgery is the central element of therapeutic management of low grade gliomas and consequently, a precise preoperative definition of their spatial extension is necessary. The question of the present work is: do the imaging abnormalities delineate the real spatial development of low grade oligodendrogliomas? A review of the literature showed that MRI on T2-weighted and FLAIR sequences are used to delineate the spatial developement of these tumours and that spectroscopic magnetic resonance imaging is more sensible to appreciate it. Moreover, mathematical models and histological studies suggest that MRI does not indicate the actual spatial extension of low grade oligodendrogliomas. This study focused on histological analysis of biopsy samples performed outside MRI imaging abnormalities in patients who harboured a low grade oligodendroglioma. It showed that isolated tumour cells were identified beyond imaging abnormalities in all of the 17 patients studied. In 15 of those 17 patients, isolated tumour cells were identified in the most distant biopsy samples taken outside imaging abnormalities. Thus, conventional imaging findings, including MRI on T2-weighted and FLAIR sequences, are not able to provide the real spatial development and boundaries of low grade oligodendrogliomas.

[Reappraisal of the Sainte-Anne Hospital classification of oligodendrogliomas in view of retrospective studies]

PURPOSE

Definition of homogeneous tumor groups of oligodendrogliomas or oligo-astrocytomas is a basic condition for an adequate evaluation and comparison of the results of treatments in patients from various institutions. However, increasing discordances are observed in the histological diagnosis of these tumors. The main goal of this study is to assess whether, for retrospective studies, MRI data may serve as a common basis for encompassing asymmetry in diagnosis established according to the WHO or Ste-Anne (SA) classification.

PATIENTS AND METHODS

This study included 251 adult patients in whom a SA grade A or B oligodendroglioma or oligo-astrocytoma was newly diagnosed at our institution from 1984 to 2003. Routine histological preparations and post-contrast preoperative MRI/CT-scan were simultaneously reviewed in order to assess the impact on survival of the following features: presence or absence of a polymorphous or gemistocytic astrocytic component, of necrosis and of contrast enhancement (CH); endothelial hyperplasia (EH) assessed as absent, present minor (HE+) or (HE++) when conform to the threshold of HE defined in the SA grading system of oligodendrogliomas. The tumors were graded A: no CH and no EH; in B: CH and /or HE++, and A/B: EH + but no CE.

RESULTS

70.1% of the tumors were classified as "pure" oligodendroglioma, 19.5% as "polymorphous oligo-astroastrocytoma" and 10.3% as "gemistocytic oligo-astrocytoma". In grade A, or B tumors, the presence of a polymorphous or a gemistocytic component had no significant influence on survival; however respectively 53% and 65% of these tumours versus 32% of "pure" oligodendrogliomas were grade B at the time of diagnosis. In either histological subtypes, survival was not significantly different when HE was absent or minor (HE+). After regrouping of the histological subtypes and of the tumors with HE+ or absent, the series included 153 oligodendrogliomas grade A and 98 grade B. Survival in patients with grade A versus grade B tumors was respectively 142 versus 52 months (p<0.0001). In grade B tumors, necrosis had no significant influence on survival. Ring-shaped contrast enhancement surrounding large foci of necrosis was observed in only 4 cases. In tumors with or without CE, patient survival was respectively 148 versus 40 months (p<0.0001). On post contrast MRI done in 235 patients, only 7 tumors (3%) were grade A/B (EH++ but no CH).

CONCLUSIONS

From these results and our previous observation that, according to the SA classification of gliomas, only oligodendrogliomas or oligo-astrocytomas may not show CE, we propose that for retrospective studies: 1) tumors diagnosed according to the Ste-Anne classification as oligodendroglioma or oligo-astrocytoma be regrouped in a unique category, 2) independent of their histological type and grade according to the WHO, gliomas that do not show CE be regrouped with SA oligodendrogliomas grade A, 3) concerning gliomas that show CE on MRI: oligodendrogliomas or oligo-astrocytomas WHO grade II or III, as well as WHO secondary glioblastomas or glioblastomas with an oligodendroglial component, be regrouped with SA oligodendrogliomas grade B; however tumors that show ring-like CE surrounding large foci of necrosis and finger-like "peritumoral" edema should be excluded or analysed separately.

[Oligodendrogliomas: historical background of classifications]

The story of the classifications for gliomas is related to the development of the techniques used for cytological and histological examination of brain parenchyma. After a review of these techniques and the progressive discovery of the central nervous system cell types, the main classifications are presented. The first classification is due to Bailey and Cushing in 1926. It was based on histoembryogenetic theory. Then Kernohan introduced, in 1938, the concept of anaplasia. The WHO classification was published in 1979, then revised in 1993 and 2000. It took into account some data from both previous systems and introduced gradually the notion of histological criteria of malignancy. More recently; molecular genetics data and clinical evolution were retained. The Sainte-Anne classification for oligodendrogliomas is based on both histological and imaging data. It includes the notion of spatial histological structure of oligodendrogliomas. Contrast enhancement is closely related to endotheliocapillary hyperplasia. Gliomas classifications are changing and confusions can be made because of lack of reproductibility and misinterpretations of samples.

[Results of the Sainte-Anne - Lyons series of 318 oligodendroglioma in adults]

INTRODUCTION

Incidence of cerebral oligodendrogliomas is increasing because of better recognition made possible by improved classifications. We studied a homogeneous series using the Sainte-Anne grading scale in order to better understanding the history of these tumors with or without treatment and to assess prognosis and associated factors.

PATIENTS AND METHODS

A retrospective series of 318 adult patients with oligodendroglioma (OLG) treated at Hôpital Sainte-Anne, Paris (SA) and Hôpital Neurologique, Lyons (L) between 1984 and 2003 was analyzed: 182 grade A OLG (SA + L), 136 grade B among which a homogenous series of 98 (SA) were included. For grade A: age at diagnosis ranged from 21 to 70 (mean: 41), sex ratio was 1.28. For grade B: age at diagnosis ranged from 12 to 75 (mean: 45.5), sex-ratio was 1.58. The main first symptoms were: epilepsy (A: 91.5%; B: 76%), intracranial hypertension (A: 7.9%; B: 14.6%), neurological deficit (A: 5.1%; B: 17.7%). The most frequent locations were: frontal, insular and central for both A and B. Mean size was 55 mm for grade A, 62 mm for B. Calcifications were found in 20% of A, 48.5% of B. No tumor was enhanced on imaging (CT/MRI) in grade A, all but 7 in grade B. All patients underwent surgery either for biopsy (A: 47.2%; B: 53%), or removal which was partial (A: 26.4% vs B: 19.4%) or extended (A: 36.3% vs B: 37.8%). Fifty-six patients underwent 2 procedures and 12 three procedures. Radiotherapy was performed in 76.9% of grade A, and 91% of B patients, in the immediate postoperative period for 71% A and 82.7% B. Chemotherapy was delivered for 36% of grade A (in the event of transformation to grade B or failure of radiotherapy) and 67.5% of B patients. Among grade A tumors, 38% transformed into grade B within a mean delay of 51 months with a mean follow-up of 78 months.

RESULTS

Median survival was 136 months for grade A and 52 for grade B. Survival at 5, 10 and 15 was 75.5%, 51% and 22.4% for grade A vs 45.2%, 31.3% and 0% for grade B respectively. In univariate and multivariate analysis, grade A survival was associated with age at diagnosis, tumor size, large removal and response to radiotherapy. Grade B survival was associated with age at diagnosis, wide removal and sharply defined limits of the tumor on imaging.

CONCLUSIONS

Analysis of both published data and this series underlines many prognostic parameters. It shows that OLG are heterogeneous tumors even in each grade (A and B). Treatment should consequently progress towards more targeted procedures for patients mainly with postoperative radiotherapy and chemotherapy.

Functional endothelin ET B receptors are selectively expressed in human oligodendrogliomas

Endothelin-1 (ET-1), a vasoactive and mitogenic peptide mainly produced by vascular endothelial cells, may be involved in the progression of several human tumors. Here, we present an immunohistochemical analysis of the expression pattern of ET-1 receptor subtypes (ET(A)-R and ET(B)-R) and a functional study of their potential role in human oligodendrogliomas and oligoastrocytomas. By comparison, we assessed the corresponding expression patterns of glioblastomas. Interestingly, a nuclear localization of ET-1 receptor subtypes (associated or not with a cytoplasmic labeling) was constantly observed in tumor cells from all three glioma types. Moreover, we noted a distinct receptor distribution in the different gliomas: a nuclear expression of ET(B)-R by tumor cells was found to be restricted to oligodendrogliomas and oligoastrocytomas, while a nuclear expression of ET(A)-R was only detected in tumor cells from some glioblastomas. Using primary cultures of oligodendroglial tumor cells, we confirmed the selective expression of nuclear ET(B)-R, together with a plasma membrane expression, and further demonstrated that this receptor was functionally coupled to intracellular signaling pathways known to be involved in cell survival and/or proliferation: extracellular signal-regulated kinase and focal adhesion kinase activation, actin cytoskeleton reorganization. In addition, impairment of ET(B)-R activation in these cells by in vitro treatment with an ET(B)-R-specific antagonist induced cell death. These data point to ET-1 as a possible survival factor for oligodendrogliomas via ET(B)-R activation and suggest that ET(B)-R-specific antagonists might constitute a potential therapeutic alternative for oligodendrogliomas.

[Dysembryoplastic neuroepithelial tumors]

Dysembryoplastic neuroepithelial tumors DNTs are highly polymorphic tumors that arise during embryogenesis. They are preferentially, but not exclusively, located in the supratentorial cortex. Histologically they may mimic any categories of low-grade or even of high-grade gliomas, but from a carcinological point of view, they behave as stable lesions. Their differential diagnosis from gliomas is obviously important to spare these young patients with a normal life expectancy the long- term deleterious effect of radiation or chemotherapy. The diagnosis of DNT must be considered when all the following criteria are present: partial seizures with or without secondary generalization, no neurological deficit or a stable congenital deficit, cortical topography on MRI, absence of peri-tumoral edema and of mass effect. In other locations, the diagnosis of DNT has to be suspected in case of discordance between the neurological status of the patient and the topography of the tumor or of unusual radiological features such as contrast enhancement but no mass effect and no edema. Supratentorial cortical DNTs tend now to be detected more systematically by imaging soon after first seizures. In most instances, the epilepsy can be cured by gross total surgical removal. Surgery also allows to prevent the risks of intratumoral hematoma or infarct. DNTs should therefore be operated soon after diagnosis. However, excellent results can also be obtained by epilepsy surgery in patients with long term drug resistant partial seizures.

Comparison of somatostatin receptor expression in human gliomas and medulloblastomas

The expression of the five somatostatin receptor subtypes, sst1-5 was compared on tissue containing glial tumours (glioblastomas or oligodendrogliomas), medulloblastomas, and on normal human cortex. By semiquantitative reverse transcription coupled to polymerase chain reaction, the receptor expression profiles were high in cortex and in tissue containing oligodendrogliomas. It was moderate in medulloblastomas. Tissue containing glioblastomas displayed lower expression of somatostatin receptor subtypes, sst1 and sst3 being mostly expressed. By 125I-Tyr0DTrp8 somatostatin-14 or 125I-Leu8DTrp22 Tyr25 somatostatin-28 autoradiography combined with synaptophysin immunohistochemistry, it was possible to differentiate between isolated tumoral cell component infiltrating the cerebral parenchyma (cortex or white matter) and tumoral tissue (without residual parenchyma) in glioblastomas or oligodendrogliomas. Glial tumoral tissue per se presented few somatostatin receptors. By contrast, medulloblastoma tumoral cells exhibited numerous octreotide sensitive somatostatin receptors. sst2 immunocytochemistry demonstrated immunostaining of neuronal cells and neuropile; sst2 and sst3 immunostaining was identified on glioblastoma proliferating vessels endothelial cells and on medulloblastomas tumoral cells. Faint sst2 immunostaining among glial tumoral cells was due to microglia, while glioma cells did not significantly stain. In summary, medulloblastoma tumoral cells express sst2/sst3 receptors at a high level while glioma cells do not. In gliomas, sst expression is restricted to endothelial cells on proliferating vessels (displaying both sst2 and sst3 receptors), including parenchyma and reactive microglia (only sst2). The differential expression of sst2/sst3 receptors on gliomas and medulloblastomas has implications for the therapy of these tumours.

Apoptosis in the central nervous system of cerebral adrenoleukodystrophy patients

The childhood cerebral form of adrenoleukodystrophy (ALD) is a fatal demyelinating disease, yet mice deficient in the ALD gene do not show such clinicopathological phenotype. We have therefore investigated in human autopsy tissues whether the ALD gene mutation results in apoptosis of CNS cells. Specimens from telencephalic and brainstem regions of four patients, and three controls were examined for internucleosomal DNA fragmentation, in situ detection of DNA breaks by the TUNEL method, and caspase-3 immunostaining. None of the controls showed significant apoptosis in white matter, while apoptotic nuclei with chromatin alterations were detected in areas of active demyelination in three ALD patients. A large proportion of apoptotic cells were oligodendrocytes and some express activated caspase-3. TUNEL-positive nuclei and/or caspase-3 staining were also detected in perivascular infiltrates and, occasionally, in neurons. We conclude that apoptosis of oligodendrocytes may account, at least in part, for the demyelinating process in the ALD brain.

[The "smears" technique for the extemporaneous examination: diagnostic contribution to neurosurgical pathology]

Smear preparation is a fairly accurate, simple and reliable tool for rapid intraoperative diagnosis of central nervous system tumors. Compared with frozen sections this technique has the advantage of being both more accurate for cytological details and of requiring less tissue. In addition final histological analysis after direct formalin fixation is of better quality than post freezing fixation. This technique is most helpful in the field of neuro-oncological pathology specially in glial tumors and in stereotactic biopsy procedures. The cytological aspects and smear patterns disclose important complementary diagnostic information for the histopathological examination.

Vascular endothelial growth factor expression in oligodendrogliomas: a correlative study with Sainte-Anne malignancy grade, growth fraction and patient survival

Microangiogenesis is a delayed but crucial event in the malignant progression of oligodendrogliomas. Accord-ingly, in the new Sainte-Anne grading system of oligodendrogliomas, endothelial hyperplasia and contrast enhancement, both being indicators of microangiogenesis, are key criteria for the distinction of grade A from grade B tumours. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor: a strong correlation between VEGF expression, Sainte-Anne malignancy grade and patient outcome might thus be expected. In order to assess this hypothesis, VEGF immunostaining was performed in a series of 34 oligodendrogliomas that included 11 grade B and 23 grade A, of which nine became grade B during the study period (mean clinical and imaging follow-up: 41 months). VEGF expression correlated strongly with Sainte-Anne tumour grade (P < 0.001), and inversely with patient survival (P < 0.001) and recurrence-free survival (P = 0.002). One hundred per cent of grade B but only 17% of grade A were VEGF-positive. By contrast, the MIB-1 labelling index did not correlate with VEGF expression, total survival or recurrence-free survival. In accordance with the grading system, this study showed that, in oligodendrogliomas, VEGF expression and microangiogenesis are progression-related phenomena that confer on these tumours a growth advantage by presumably reducing hypoxia-induced apoptotic cell death. These findings might have important implications in the future for the indication and timing of anti-angiogenic therapies.

Stereoelectroencephalography in focal cortical dysplasia: a 3D approach to delineating the dysplastic cortex

Focal cortical dysplasia (FCD) is an increasingly recognized cause of intractable epilepsy. Surgical data suggest that the dysplastic cortex should be removed to obtain freedom from seizures, but the prognosis remains poor as FCD is difficult to delineate by imaging. We retrospectively analysed a series of 28 patients (aged 5-41 years, median 16.5 years) with FCD who had been investigated by stereoelectroencephalography (SEEG) between 1964 and 1995. Neurophysiological data were correlated with histological findings and surgical outcome. MRI was available for only seven patients. Severe partial epilepsy of early onset, pre-existing neurological deficit (68%) and cognitive impairment were the main clinical features. FCD was distributed equally between all lobes except for the temporal lobe, and was found predominantly on the mesial aspect of the cerebral hemispheres. SEEG findings provided evidence of dysplastic tissue epileptogenicity, as demonstrated by intralesional rhythmic spike discharges, the onset of ictal discharges and a low epileptogenic threshold. The epileptogenic zone corresponded to histologically defined FCD in 82% of the cases. Despite the lack of adequate neuroimaging in most cases, 64% of the patients became seizure-free after surgery. The main predictors of a favourable outcome were complete removal of the epileptogenic zone (P< 0.01) and complete removal of the dysplastic cortex (P< 0.01). These results emphasize the usefulness of neurophysiological data in accurately assessing the extent of the FCD.

[High grade (B) oligodendroglioma. Concerns and pitfalls in the intraoperative examination of smears]

According to the Ste Anne hospital classification and grading system of oligodendrogliomas the presence of contrast enhancement on MRI and/or the presence of an histological endothelial hyperplasia are correlated with a pejorative prognosis (high grade or grade B). Surgical tumoral exerese and adjuvant chemo or radiotherapy are indicated. When clinical and radiological aspects are typical the extemporaneous diagnosis of oligodendroglioma on smear is usually easy (1). In case of atypical forms: unusual localization or cytological appearance, especially with a small cell hyperchromatic undifferenciated tumor few diagnostic hypothesismay be considered. Four cerebellar tumors are presented with relevant and differential cytological diagnostic criteria. A comparative study between clinical and radiological aspects of medulloblastoma, primitive lymphoma, undifferenciated small cell lung carcinoma, and grade B oligodendroglioma is presented.

Retinoic acid modulates RAR alpha and RAR beta receptors in human glioma cell lines

To identify retinoic acid (RA) signalling pathways involved in growth and differentiation in cells of the glial lineage, two human glioma ceh lines were studied. The three RA receptors (RARs) mRNAs were constitutively expressed, and of the three RXRs, RXR beta appeared predominant. Western blotting analysis confirmed the constitutive expression of RAR alpha and RAR beta. Treatment with all-trans-RA induced morphological changes in the two cell lines, which progressed from their normal pattern of randomly oriented spindle-shaped cells to fibroblast-like glial cells. RA up-regulated RAR alpha and RAR beta mRNAs in both cell lines. Interestingly, RA treatment up-regulated RAR beta proteins but not RAR alpha proteins, suggesting post-transcriptional regulations of RAR transcripts in glioma cells.

Modulated release of IdUrd from poly (D,L-lactide-co-glycolide) microspheres by addition of poly (D,L-lactide) oligomers

This paper reports the release characteristics of a radiosensitizer, 5-iodo-2'-deoxyuridine (IdUrd), from poly (D,L-lactide-co-glycolide) 50: 50 (PLGA) microparticles obtained by a phase separation technique. Poly (D,L-lactide) oligomers (D,L-PLA) were incorporated into the PLGA matrix in order to accelerate the overall drug release rate and regulate the triphasic release profile exhibited by the standard PLGA microparticles. For D,L-PLA (800), the burst effect was large and the IdUrd release was complete between 28 and 35 days. These results were attributed to rapid pore formation on the periphery of the microsphere in the early stages of incubation, due to hydrosolubility of the smallest oligomers (D,L-PLA (800)). In the case of D,L-PLA (1,100), drug release occurred over a six week period, the standard time course of conventional radiation therapy. The period during which the radiosensitizer was incorporated in human brain tumor cell nuclei after its entrapment in biodegradable microspheres was determined by using an organotypical tissue culture. The presence of radiosensitizer in the DNA of tumor cell nuclei was detected by immunohistochemical labelling of tumor fragments. IdUrd release from standard microspheres (7+/-0.5 weeks) was longer than from oligomer-containing batches. For D,L-PLA (800)-containing microspheres, the radiosensitizer was entirely released within 4. 5+/-0.5 weeks. The microspheres containing D,L-PLA (1,100) allowed an IdUrd release over a 5 to 6 week period. The ex vivo data were consistent with the in vitro findings in terms of release duration.

Edg-2 in myelin-forming cells: isoforms, genomic mapping, and exclusion in Charcot-Marie-Tooth disease

Edg-2 is an heptahelical receptor whose spatio-temporal distribution during rat brain development is consistent with a role in the control of myelination. We have now identified two splice variants of Edg-2 mRNA in rat brain that encode two receptor isoforms differing by a stretch of 18 amino acids in the NH2-terminal extracellular tail of the receptor. Prenatally (i.e., before oligodendrocyte myelination), the two variants detected by selective in situ hybridization are equally abundant, vary in parallel, and remain restricted to proliferative zones in the brain. Postnatally, the long isoform becomes predominant in myelinating structures, where its abundance increases sharply during the period of myelination. In the adult human brain, only the long variant was detected, while in situ hybridization showed it selectively expressed in the white matter and in clusters of cells showing features of oligodendrocytes of the temporal cerebral cortex. Consequently, the human Edg-2 gene was studied to assess its possible contribution in inherited neuropathies. The coding sequence was found to be contained in three exons and to map to chromosome 9q31.3-32 by using radiation hybrid panel and Yeast-Artificial Chromosomes. Two intragenic bi-allelic polymorphisms and a rare mutation were identified. As a first application to molecular genetic studies, they were used to exclude the Edg-2 gene in six families with phenotype of demyelinating Charcot-Marie-Tooth disease of unknown origin.

Dysembryoplastic neuroepithelial tumors: nonspecific histological forms -- a study of 40 cases

OBJECTIVE

To demonstrate that DNTs include a large morphological spectrum of tumors that cannot be histologically distinguished from conventional categories of gliomas.

METHODS

All tumors from patients who underwent epilepsy surgery in Sainte-Anne hospital (Paris) that histologically resembled gliomas and did not conform to current histological criteria for DNTs or gangliogliomas were entered in the study.

RESULTS

According to the WHO histological classification, the 40 tumors resembled: pilocytic astrocytomas (4 cases), astrocytomas (16 cases), anaplastic astrocytoma (1 case), oligodendrogliomas (10 cases), oligo-astrocytomas (8 cases) or anaplastic oligo-astrocytomas (1 case). However foci of cortical dysplasia could be observed in 47% of the cases. Clinical presentation and imaging features were strikingly similar to that observed in typical DNTs. Although surgical removal was incomplete in 28% of the cases and none of the patients underwent chemo or radiotherapy, none of the tumors recurred (mean follow-up: 7 years). Moreover, serial preoperative imaging in 26 patients (mean follow-up: 4.5 years) demonstrated that these lesions were perfectly stable.

CONCLUSIONS

Whatever the histological appearance of a glial tumor, the diagnosis of DNT must be considered when all the following criteria are associated: (1) partial seizures, with or without secondary generalization, beginning before the age 20 years, (2) no neurological deficit or stable congenital deficit, (3) cortical topography of the lesion as better demonstrated by MRI and (4) no mass effect on imaging.

Chronic intractable epilepsy associated with a tumor located in the central region: functional mapping data and postoperative outcome

Out of 57 patients operated for intractable epilepsy of the central region, 8 harbored an indolent glioma (7 dysembryoplastic neuroepithelial tumors, 1 ganglioglioma). Mapping of the sensorimotor area with depth electrodes implanted for stereoelectroencephalographic exploration demonstrated no or abnormal motor responses after low-frequency stimulation, and variable sensory responses to high-frequency stimulation, suggesting reorganization of the sensorimotor cortex representation around the tumor and absence of functional tissue within the neoplastic volume. After lesionectomy (3 cases) or corticectomy including the tumor (5 cases), 6 (75%) patients were seizure-free (class I of Engel) at the time to follow-up. No permanent motor or sensory deficit was observed in 6 cases. In 2, a mild facial (in 1) and arm (in 1) deficit persisted. It is concluded that the resection of intrinsic low-grade tumors associated with long-standing epilepsy and located in the central region can be associated with excellent seizure outcome and no or minimal postoperative deficit because of functional reorganization of the sensorimotor cortex.

Oligodendrogliomas. Part I: Patterns of growth, histological diagnosis, clinical and imaging correlations: a study of 153 cases

The present study has attempted to demonstrate that the morphological spectrum of oligodendrogliomas includes tumors which are traditionally misinterpreted as 'diffuse fibrillary astrocytoma'. We have shown that these tumors are in fact made of isolated neoplastic oligodendrocytes which are entrapped in a fibrillary background composed of axons and fibrillary reactive gliosis. Analysis in a series of 153 'pure' supratentorial oligodendrogliomas composed of 'classical' or pseudo 'diffuse fibrillary oligodendrogliomas' diagnosed by imaging-based serial stereotactic biopsies showed that 2/3 of the tumors were exclusively made of isolated tumor cells (ITCs) (structure type III) and that only 1/3 of them exhibited both ITCs and solid tumor tissue components (structure type II). The tumor tissue destroys the brain parenchyma and contains new formed microblood vessels whereas ITCs do not destroy the parenchyma and are not associated with microangiogenesis. These fundamentally opposite morphological characteristics were reflected by the following findings: 1) contrast enhancement was observed in 64% of structure type II but was never seen in structure type III oligodendrogliomas. 2) a neurological deficit occurred in 57% of structure type II but in only 8% of structure type III oligodendrogliomas. 3) using the new grading system described in the companion paper to this study, we found that the biological behavior of oligodendrogliomas was also closely related to the patterns of tumor growth. From a synthesis of data gathered in this study it is suggested that emergence of microangiogenesis within a tumor which at first grows slowly with a structure type III pattern is a crucial event toward more aggressive behavior.

Oligodendrogliomas. Part II: A new grading system based on morphological and imaging criteria

This second part of our study of 'pure' oligodendrogliomas focuses on survival data analysis. In order to identify potentially useful prognostic factors and to assess the effectiveness of a new grading system, the 79 patients in the previously analyzed series for whom adequate follow-up could be obtained (52%) were entered in the present analysis. Statistical analysis demonstrated that contrast enhancement and endothelial hyperplasia had powerful and similar influence on survival. Median survival with and without contrast enhancement were: 3 versus 11 years, and with or without endothelial hyperplasia were: 3.5 versus 11 years. Conversely, the degree of nuclear atypia and presence or absence of mitosis or necrosis were not correlated with survival. These findings allowed us to devise a simple grading system which discriminates two malignancy grades as follows: absence of endothelial hyperplasia and of contrast enhancement = Grade A, presence of endothelial hyperplasia and/or of contrast enhancement = Grade B. Of the 79 oligodendrogliomas in this study, 59 tumors were categorized as grade A and 20 as grade B. Median survival were: 11 years in grade A and 3.5 years in grade B. Five-year and 8-year survival rates were: 89% and 60% in grade A and: 33% and 15% in grade B. Double blind grading between two independent observers was concordant in 96% of the cases. Application of this simple efficient and reproducible grading scheme should permit reliable comparison of retrospective or prospective therapeutic data emanating from various institutions.

Extradural spinal tophaceous gout: evolution with medical treatment

A patient with chronic tophaceous gouty arthritis developed paraparesis due to medullar compression from a urate sodium tophus. We report the MRI features of this tophaceous gout, which showed an extradural hyperintense signal with an isointense nodule signal on T1 weighted sequences. Surgical removal of the epidural lesion resulted in complete clinical recovery. At the upper level of the spine, an extension of the epidural lesion was not removed, but after one year of medical treatment of the gout, MRI showed regression of the epidural compression.

Dysembryoplastic neuroepithelial tumors located in the caudate nucleus area: report of four cases

OBJECTIVE AND IMPORTANCE

Dysembryoplastic neuroepithelial tumors (DNTs) histologically resemble gliomas but behave as stable lesions. These tumors initially were considered to be located exclusively within the supratentorial cortex. The four reported cases demonstrate that DNTs may also arise in the area of the caudate nuclei. Moreover, the peculiar topography of these lesions, which suggests a derivation from the subependymal plate, is in accordance with the putative origin of DNTs from secondary germinal layers.

CLINICAL PRESENTATION

The patients experienced partial seizures (two patients), generalized seizures (one patient), or headaches (one patient). All patients were young (17-26 yr) at the onset of symptoms, and all had normal results from their neurological examinations.

INTERVENTION

All lesions demonstrated a pseudocystic appearance on computed tomographic scans, were hypointense on T1-weighted magnetic resonance imaging scans, hyperintense on T2-weighted magnetic resonance imaging scans, and did not show contrast enhancement. The four tumors similarly lined the left or right caudate nuclei and expanded within the homolateral ventricle (three patients) or both lateral ventricles (one patient). In one patient, the tumor also involved the adjacent paraolfactory cortex.

CONCLUSION

In all patients, stereotactic biopsies helped to identify a specific glioneuronal element of DNTs. None of the tumors was operated on. Radiotherapy was performed in only one patient. A long pre- and/or postbiopsy imaging follow-up, which was available in two nontreated patients (3 yr and 16 yr), demonstrated the perfect stability of the lesion. The occurrence of DNTs in this peculiar location needs to be considered to avoid misidentification as "ordinary" gliomas and prevent useless aggressive treatment.

Dementia in two histologically confirmed cases of multiple sclerosis: one case with isolated dementia and one case associated with psychiatric symptoms

During the past 10 years, considerable attention has been devoted to cognitive impairment in multiple sclerosis. Occasionally this impairment may be so severe that multiple sclerosis presents as a dementia associated with only minor neurological signs and symptoms. The cases of two women affected by multiple sclerosis who presented with a pure dementia are reported. In the first patient, a progressive apragmatic behavioural disturbance with reduced short term memory and learning abilities were the main clinical features. Neuropathological examination of the brain disclosed numerous plaques in the periventricular white matter, with severe atrophy of the corpus callosum. Plaques were also seen in the white matter of both hippocampus and in the columns of the fornix. The impairment of short term memory could be linked to these lesions. Behavioural changes were probably related to the bilateral lesions of the long associative bundles that disconnected the frontal lobes from other parts of the cerebral hemispheres. In the second patient, visual hallucinations were associated with cognitive dysfunction. MRI showed large plaques in the white matter of both left frontal and temporal lobes. Smaller plaques were also present in the periventricular white matter of the occipital lobes, the nature of which were confirmed by a stereotactic biopsy.

Dysembryoplastic neuroepithelial tumours

Dysembryoplastic neuroepithelial tumours (DNTs) are a group of supratentorial cortical benignant lesions that superficially resemble mixed oligo-astrocytomas, oligodendrogliomas or astrocytomas. Clinically these tumours are associated with partial seizures beginning before the age of 20 years, with no neurologic deficit and no stigmata of phacomatosis. In the revised WHO classification, DNTs have been incorporated among the category of neuronal and mixed neuronoglial tumours. This classification describes a histologic variant characterized by the following criteria: cortical location, multinodular architecture--the nodule being made of multiple variants looking like astrocytomas, oligodendrogliomas or oligo-astrocytomas, foci of dysplastic cortical disorganization and the presence of a glioneuronal element showing a columnar structure perpendicular to the cortical surface. A study of 14 cases for which only a specific glioneuronal element could be identified demonstrated that this specific element is sufficient for diagnosing DNTs and that the spectrum of DNTs includes a simple form with a unique glioneuronal element. Preoperative imaging follow-up data, in the series of 23 simple and complex forms, indicated that DNTs are perfectly stable. However, these tumours may show a high MIB 1 labeling index.

Histological grading of gliomas

Usefulness of grading systems based on non-specific features (e.g. mitosis, necrosis) is unequivocal in only certain types of astrocytomas, and their efficiency remains to be seen in oligodendrogliomas and in mixed oligo-astrocytomas. The possibility of grading ependymomas is still uncertain. Accordingly, only a small proportion of gliomas which occur in children can be reliably graded. Lack of reproducibility is a severe impediment of both current conventional and kinetic methods in the prognosis of gliomas.

Central neurocytomas. Critical evaluation of a small-cell neuronal tumor

We report herein the clinical and pathological features of 20 patients with central neurocytomas. Investigations for various differentiation antigens and cell type-specific markers were performed by immunohistochemistry using paraffin-embedded tissue. In addition, the expression of L1 adhesion molecule and of the various N.CAM (neural cell adhesion molecule) isoforms were investigated by immunoblotting studies in two frozen specimens. Central neurocytomas are clinically characterized by their intraventricular localization, occurrence in young adults, and good prognosis. It rarely occurs in patients over 50, but such cases have a poor prognosis. Total surgical excision is the best treatment. Radiotherapy is appropriate if surgery is incomplete or contraindicated. Histologically, central neurocytomas display the following features: an oligo-like pattern, usually associated with large fibrillary rosettes or perivascular arrangement, and a rich endocrine-type vasculature. Central neurocytomas have a remarkably homogeneous antigenic profile. GFAP expression is only found in scattered reactive astrocytes, S100 protein in reactive astrocytes and rare tumor cells. Among the pan-neuroendocrine markers, central neurocytomas always express neuron-specific enolase; they frequently express synaptophysin but never chromogranin A. Synaptophysin is the most reliable immunohistological marker for central neurocytomas; however, immunoreactivity could be lost with long formalin fixation. In these cases, electron microscopy is used to support the neuronal nature of the tumor cells. The expression of L1 adhesion molecule and the isoform 180 of N.CAM, indicates that central neurocytomas are formed by cells committed to neuronal phenotype. Nevertheless, advanced neuronal differentiation may be absent, as suggested by the persistence of embryonic N.CAM, the nonexpression of neurofilament proteins, and the absence of mature synapses in numerous cases. Central neurocytomas and neuroblastomas share some biochemical properties, but their respective clinicopathological features and biological behavior are dramatically different.

Histological grading and bromodeoxyuridine labeling index of astrocytomas. Comparative study in a series of 60 cases

The histological grade and the bromodeoxyuridine (BUdR) labeling index of 60 astrocytomas of "ordinary" cell types (fibrillary, protoplasmic, gemistocytic, and anaplastic astrocytomas and glioblastomas) were compared to determine whether the grading system reflects the proliferative potential of the tumors. The tumor grade was based on the presence or absence of four criteria (nuclear abnormalities, mitosis, necrosis, and vascular endothelial proliferation): Grade 1, no criterion, Grade 2, one criterion, Grade 3, two criteria; and Grade 4, three or four criteria. The BUdR labeling index, or percentage of S-phase cells, was calculated in paraffin-embedded tumor sections after in situ labeling by intraoperative intravenous infusion of BUdR, 200 mg/sq m. Exponential regression analyses showed a positive correlation between the histological grade and labeling index (r = 0.88, p less than 0.001) that was stronger than the correlations between log labeling index and age (r = 0.55, p less than 0.001) and between grade and age (r = 0.55, p less than 0.001). These results indicate that the histological grading system reflects the proliferative potential of "ordinary" astrocytomas.

Diagnosis and treatment of colloid cysts of the third ventricle by stereotactic drainage. Report on eleven cases

Between December 1979 and September 1986, 11 patients with colloid cysts of the third ventricle were operated on by a stereotactic procedure with Talairach's system. Stereoscopic angiography and ventriculographic study allowed for a percutaneous (twist-drill hole diameter: 2.5 mm) stereotactic aspiration of the cysts. The operations were successful, and there were no intraoperative or postoperative mortalities but just mild transient morbidity in three cases. Six cysts were evacuated completely, and five only partially. The mean residual volume was 19% of the initial one. Clinical and anatomical results are presented, and the advantages of this stereotactic procedure are discussed.

Radiation therapy in the management of low-grade supratentorial astrocytomas

The records of 167 patients with grade 1 or 2 supratentorial pilocytic astrocytomas (41 patients), ordinary astrocytomas (91 patients), or mixed oligoastrocytomas (35 patients) diagnosed between 1960 and 1982 are retrospectively reviewed. The extent of surgical tumor removal was gross total or radical subtotal in 33 patients (20%) and subtotal or biopsy only in the remaining 134 patients (80%). Postoperative radiation therapy was given to 139 (83%) of the 167 patients, with a median dose of 5000 cGy (range 600 to 6500 cGy). Multivariate analysis revealed that a pilocytic histology was the most significant prognostic variable associated with a good survival. The 5- and 10-year survival rates were, respectively, 85% and 79% for the 41 patients with pilocytic astrocytomas compared to 51% and 23% for the 126 patients with ordinary astrocytomas or mixed oligoastrocytomas. Postoperative irradiation did not appear to be associated with improved survival times in the patients with pilocytic astrocytomas; however, in the 126 patients with ordinary astrocytomas or mixed oligoastrocytomas, those who received "high-dose" radiation (greater than or equal to 5300 cGy) had significantly better survival times than those who received "low-dose" radiation (less than 5300 cGy) or surgery alone. The 5- and 10-year survival rates were, respectively, 68% and 39% for the 35 patients receiving high-dose radiation, 47% and 21% for the 67 receiving low-dose radiation, and 32% and 11% for the 19 treated with surgery alone. The survival rate was poor for the 23 patients with ordinary astrocytomas and oligoastrocytomas who underwent gross total or radical subtotal tumor removal (14 of whom were also irradiated): 52% at 5 years and 21% at 10 years, with 19 of 23 patients developing tumor progression and dying 1 to 12 years postoperatively. In contrast, all 10 patients with pilocytic astrocytomas who had gross total or radical subtotal tumor removal alone were long-term survivors, with follow-up periods of about 4 to 25 years.