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

INTRODUCTION: Dysembryoplastic neuroepithelial tumors and gangliogliomas are developmental glioneuronal tumors usually revealed by partial epilepsy. High epileptogenicity, childhood epilepsy onset, drug-resistance, temporal location, and seizure freedom after complete resection are common characteristics of both tumors. We report the specificity of surgical management, functional results and seizure outcome in cases of a tumor location in eloquent areas. METHODS: Among 150 patients (88 males, 3-55 years) operated on for refractory epilepsy due to a glioneuronal tumor (1990-2015), 30 (20%, dysembryoplastic neuroepithelial tumors=21; gangliogliomas=9) had a tumor located in an eloquent cortex (sensory-motor, insular or language areas). Surgery was performed after a preoperative work-up, including stereo-electroencephalography in 48 patients (26%) and functional MRI in 100 (67%). MRI-guided lesionectomy was mainly performed in extra-temporal location, whereas an additional corticectomy was performed in a temporal location. Tumor microsurgical resections were guided using neuronavigation and cortical/subcortical electrical stimulations. Multiple stereotactic thermocoagulations were performed in two insular tumors. RESULTS: New motor/language deficits related to eloquent areas occurred postoperatively in 6/30 patients (20%) without any major permanent disability. Minor sensorimotor (n=2) and moderate language disturbance (n=1) persisted in three of them. Postoperative seizure-free outcome (mean follow-up>5 years) was obtained in 81% of the entire series, but significantly decreased to 60% in eloquent areas. Incomplete tumor resection was the main cause of surgical failure. However, unfavorable seizure outcome was also observed despite complete tumor resection. Malignant transformation occurred in one ganglioglioma. CONCLUSION: Epilepsy surgery for benign glioneuronal tumors in eloquent areas provides acceptable results regarding the functional risks. Complete tumor resection is crucial for long-term favorable outcome.

Role of gap junctions on synchronization in human neocortical networks.

Gap junctions (GJ) have been implicated in the synchronization of epileptiform activities induced by 4-aminopyrine (4AP) in slices from human epileptogenic cortex. Previous evidence implicated glial GJ to govern the frequency of these epileptiform events. The synchrony of these events (evaluated by the phase unlocking index, PUI) in adjacent areas however was attributed to neuronal GJ. In the present study, we have investigated the effects of GAP-134, a recently developed specific activator of glial GJ, on both the PUI and the frequency of the 4AP-induced epileptiform activities in human neocortical slices of temporal lobe epilepsy tissue. To delineate the impact of GJ on spatial spread of synchronous activity we evaluated the effects of carbenoxolone (CBX, a non-selective GJ blocker) on the spread in three axes 1. vertically in a given cortical column, 2. laterally within the deep cortical layers and 3. laterally within the upper cortical layers. GAP-134 slightly increased the frequency of the 4AP-induced spontaneous epileptiform activities while leaving the PUI unaffected. CBX had no effect on the PUI within a cortical column or on the PUI in the deep cortical layers. CBX increased the PUI for long interelectrodes distances in the upper cortical layers. In conclusion we provide new arguments toward the role played by glial GJ to maintain the frequency of spontaneous activities. We show that neuronal GJ control the PUI only in upper cortical layers.

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.

Very early EEG responses to a meaningful auditory stimulus in the frontal lobes: an intracerebral study in humans.

Frontal auditory evoked potentials (FAEPs) obtained as a response to the warning auditory stimulus of a contingent negative variation task from depth electrodes were investigated. The second, imperative stimulus was visual. Thirteen epileptic patients participated in the study. Records from 20 electrodes of 10 patients exhibited signs of local generation. They were localized in the motor cortices (7 cases), in the superior, medial, and inferior frontal gyri (7 cases), in the cingulate gyrus (5 cases), and in the nucleus caudatus (1 case). A typical FAEP from these generators consisted of three components: (i) first negative wave peaking at 99+/-13 ms; (ii) positive wave peaking at 181 +/- 21 ms; (iii) second negative wave peaking at 324 +/- 63 ms. In 11 generators no evoked activity to visual stimulus was observed; in the remaining 9 generators both auditory and visual stimuli evoked a response. FAEPs with very early onsets (onset latency below 20 ms) were found in three sites in the precentral gyrus.

Comparing ERP concomitant with stimulus-induced and self-paced movements: intracerebral recordings at various cortical sites.

OBJECTIVES: To compare the shape, amplitude, and topographical distribution over sensorimotor and centroparietal cortex of two sets of ERP concomitant with the same type of movement (MCP), either visually-triggered (VT-MCP) or self-paced (SP-MCP). METHODS: MCP were recorded in 21 patients with intractable partial seizures, undergoing presurgical evaluation using stereotaxically implanted multilead intracerebral electrodes. Each patient was tested during a single session with three successive experimental paradigms, each comprised of thirty trials: (1) a tone announcing a visual pattern, with no instruction to move; (2) same tone, and instruction to squeeze abruptly a joystick at a visual signal; (3) instruction to perform the same movement paced at will, without any "go" signal. Averaged ERP recorded during task (1) were subtracted from those recorded during task (2) giving the VT-MCP. All records were taken from various cortical sites devoid of overt pathological activity. RESULTS: MCP recorded from two main sites, perirolandic and centroparietal, were compared. Between all sites, VT-MCP and SP-MCP morphology differed only slightly. Ipsilateral and contralateral MCP were also very similar. By contrast, perirolandic MCP were mainly monophasic negative (N component 400 ms after visual stimulus), whereas centroparietal MCP tended to be biphasic, the late negativity being preceded by a positive P component, at 125 ms. CONCLUSIONS: MCP patterns were quasi-identical regardless of how they were elicited (visually-triggered or self-paced). On the other hand, perirolandic and centroparietal MCP had distinct shapes, suggesting that the mode of functioning of the generators at the two sites is different.

[On the best strategies on the best results for surgery of frontal epilepsy]. / Quelles stratégies pour quels résultats dans la chirurgie des épilepsies partielles frontales?

Frontal lobe epilepsy surgery is the second most common surgery performed for drug-resistant partial epilepsy. We investigated the longitudinal outcome in a cohort of patients investigated since 1990 with SEEG and modern diagnostic techniques. We reviewed 105 patients who underwent surgery between 1990 and 2005 (mean follow-up, six years; range: one to 17 years) and analyzed the year-per-year follow-up according to Engel's classification. Favorable outcome (Class I) was observed for 70% and this result was stable at least five years after surgery. More than 90% of patients with lesion-related epilepsies (focal cortical dysplasia and dysembryoplastic neuroepithelial tumors) became seizure-free. Less than 50% of patients classified as having cryptogenic epilepsy (defined as normal imaging and neuropathology on surgical specimen) had a favorable outcome. Permanent neurological sequelae were subtle and rare, especially after surgery for dysplasia in eloquent cortex (primary motor cortex). Our data indicate that frontal surgery is a successful treatment in patients when electrophysiological and morphological investigations demonstrate a well-defined epileptogenic zone or lesion to be surgically resected. Progress in electrophysiological and brain-imaging techniques will further improve the selection of frontal lobe epilepsy surgery candidates.

[Surgical resections in functional areas: report of 89 cases]. / Résections en région fonctionnelle: étude d'une série de 89 cas.

Surgical resections for intractable epilepsy are generally associated with a high risk of permanent neurological deficit and a poor rate of seizure control. We present a series of 89 patients operated on from 1992 through 2007 for drug-resistant partial epilepsy, in whom surgery was performed in a functional area of the brain: the central (sensorimotor and supplementary motor areas) region in 48 cases, posterior regions (parietal and occipital) in 27, the insula in eight, and the language areas in six. Epilepsy was cryptogenic in 12 patients, and lesion-related in 77: malformation of cortical development in 43, tumor in 17, perinatal cicatrix in 13, vascular lesion in three, and another prenatal lesion in one. Seventy patients underwent stereoelectroencephalographic (SEEG) exploration. The surgical procedure was resective (lesionectomy or SEEG-guided corticectomy) in 83 patients and multiple stereotactic thermocoagulations in six. Ten patients were reoperated because of early seizure recurrence. A postoperative complication was observed in 12 patients. Postoperative deficits were observed in 54 patients (61%) and resolved completely in 29. In 25, a permanent deficit persisted, minor in 19 and moderate to severe in six, which did not correlate with localization or etiology. With a one-year follow-up in 74 patients (mean, 3.6 years), 53 (72%) were in Engel's class I, including 38 (51%) in class IA. Seizure outcome was significantly associated with etiology: 93% of Taylor-type focal cortical dysplasia, whereas only 40% of cryptogenic epilepsies were in class I (p<0.05). This suggests that resective or disconnective surgery for intractable partial epilepsy in functional areas of the brain may be followed by excellent results on seizures and a moderate risk of permanent neurological sequelae.

[Corticectomy: technical considerations]. / Cortectomies: aspects techniques.

The surgical treatment of epilepsy requires careful preparation and presents a certain number of technical specificities. The neurosurgeon must master not only the technical aspects but also the therapeutic and functional trade-off in order to modulate the procedure according to morphological and electrophysiological intraoperative data. A large number of technical variants have been developed to correspond to epileptological or functional anatomical considerations. Until this point, the choice of a particular technique does not seem to have a significant impact on the therapeutic effectiveness of surgery, and differences in results can be related to the presurgical evaluation and surgical indications. On the other hand, technical development promises to play an important role in limiting the long-term neurocognitive consequences of surgery.

[Surgical resection of focal cortical dysplasias in the central region]. / Chirurgie des dysplasies corticales focales en région centrale.

BACKGROUND AND PURPOSE: Taylor-type focal cortical dysplasias (TTFCD) represent a particular pathological entity responsible for severe drug-resistant epilepsy of extratemporal location. Epilepsy can be surgically cured if complete removal of the lesion can be performed. However, identification on imaging may be difficult and negative standard MRIs are not rare. The frequent location of TTFCD in the central region restrains the possibilities of complete resection. We report a series of patients operated on for intractable epilepsy associated with TTFCD in the central area. PATIENTS AND METHODS: Between 2000 and 2006, of 34 consecutive patients with TTFCD, 17 had a lesion located in the central area. MRI was considered normal in eight, although in five a subtle gyral abnormality was disclosed on further analysis. A (18)FDG PET scan performed in 16 cases demonstrated focal hypometabolism in 15 that correlated with abnormalities on MRI when visible. SEEG performed in 13 cases revealed typical abnormalities for TTFCD in 10 cases. At resection, cortical and subcortical stimulations of the dysplastic cortex did not elicit a motor response. RESULTS: Postoperative motor or sensory deficit was observed in 13 patients--severe in four--which subsequently resolved completely in seven. Six patients had a minor permanent, motor or sensory deficit. Four patients were reoperated for seizure recurrence and residual dysplastic tissue was found at reoperation in three cases. Average postoperative follow-up was 3.7 years. Sixteen patients (94%) were in Engel Class I (65% in Class IA). CONCLUSION: This study suggests that surgical resection of central region TTFCD may be associated with favorable seizure outcome and no or minor functional permanent disability. In cases of seizure relapse, reoperation can be performed without further permanent deficit and lead to seizure-free outcome. Future techniques for intraoperative detection of these lesions could optimize their complete resection in functional areas.

[Vagus nerve stimulation for the treatment of refractory epilepsy]. / Stimulation chronique du nerf vague dans le traitement del'épilepsie pharmacorésistante.

Proposed as an additive symptomatic treatment of refractory epilepsy, vagus nerve stimulation (VNS) has proven to be effective and well-tolerated in patients presenting with refractory epilepsy for whom cortical resection is not indicated. After two years of treatment, the overall reduction of seizure frequency averaged 40%. In 50% of the patients, the frequency of seizures decreased by at least 50%. Moreover, even in absence of a significant reduction of seizures, patients who undergo this treatment reported an improvement in their quality of life. Economic surveys also demonstrate a favorable impact of VNS on the management of refractory epilepsy. Since 1988, 65,000 patients with refractory epilepsy throughout the world have been treated by VNS for this indication (1000 in France). The surgical implantation technique used in our department, the effects of vagus nerve stimulation reported in the literature, and our experience with a cohort of 70 patients with refractory epilepsy who received implants over the last 10 years are described.

[Cellular mechanisms of the epilepsies: In vitro studies on human tissue]. / Etudes in vitro sur tissu humain des mécanismes cellulaires des épilepsies.

BACKGROUND AND PURPOSE: Animal models have provided very valuable data to specify the physiopathological mechanisms of the various forms of epilepsy. However, the question arises of knowing which of these experimental results are relevant to the human epileptic brain. The development of epileptic surgery makes it possible to directly study the functional properties of human brain tissue in vitro and to analyze the mechanisms underlying seizures and epileptogenesis. We review some of the results obtained over the last few years in our laboratory based on electrophysiological, immunocytochemical and molecular experiments conducted on human brain tissue. RESULTS: This review covers a number of the mechanisms of neuronal synchronizations generating epileptiform discharges, including the role of electrical synapses connecting the inhibitory interneurons, particularly in Taylor-type focal cortical dysplasia and the functional lability of GABAergic inhibition in epileptogenic human cortical tissue, which may sustain triggering and propagation of seizures. Some of these mechanisms have not been described in animal models. CONCLUSIONS: Studies on human tissue, when carefully designed, are necessary to validate the data collected on animal models and will continue to provide us with new and important information on the cerebral changes related to epilepsy. Moreover, these studies allow development of a class of antiepileptic drugs that have a completely new mechanism of action, which could be effective in the treatment of drug-resistant epilepsies.

[Brainstem cavernomas: surgical experience at the CH Sainte-Anne general hospital]. / Cavernomes du tronc cérébral: l'expérience chirurgicale du centre hospitalier Sainte-Anne.

BACKGROUND AND PURPOSE: No standard treatment for brainstem cavernoma has been established because of the lack of sufficient data about the natural history of these lesions in a highly functional location with potential difficult surgical accessibility. METHODS: We present a series of 82 brainstem cavernomas managed at the Sainte-Anne Hospital. Surgery was undertaken for 25 with stereotactic biopsy for 9 and direct surgery for 19 (3 after biopsy). RESULTS: Surgical outcome was good or fair for 17 patients. Two patients worsened and one died. Biopsy results were disappointing with high morbidity (4 patients with 2 permanent deficits). Histological diagnostic was possible for all biopsies. CONCLUSION: In light of these results, an active surgical attitude could be proposed for cavernomas in an accessible locations which have produced at least one previous hemorrhage. Stereotactic biopsies for suspect brainstem cavernoma must be avoided.

Effects of gap junction blockers on human neocortical synchronization.

Field potentials and intracellular recordings were obtained from human neocortical slices to study the role of gap junctions (GJ) in neuronal network synchronization. First, we examined the effects of GJ blockers (i.e., carbenoxolone, octanol, quinine, and quinidine) on the spontaneous synchronous events (duration = 0.2-1.1 s; intervals of occurrence = 3-27 s) generated by neocortical slices obtained from temporal lobe epileptic patients during application of 4-aminopyridine (4AP, 50 muM) and glutamatergic receptor antagonists. The synchronicity of these potentials (recorded at distances up to 5 mm) was decreased by GJ blockers within 20 min of application, while prolonged GJ blockers treatment at higher doses made them disappear with different time courses. Second, we found that slices from patients with focal cortical dysplasia (FCD) could generate in normal medium spontaneous synchronous discharges (duration = 0.4-8 s; intervals of occurrence = 0.5-90 s) that were (i) abolished by NMDA receptor antagonists and (ii) slowed down by carbenoxolone. Finally, octanol or carbenoxolone blocked 4AP-induced ictal-like discharges (duration = up to 35 s) in FCD slices. These data indicate that GJ play a role in synchronizing human neocortical networks and may implement epileptiform activity in FCD.

Dystonic posturing in seizures of mesial temporal origin: electroclinical and metabolic patterns.

OBJECTIVE: To test the hypothesis that extratemporal neuronal networks are involved in dystonic posturing (DP) observed in mesial temporal epilepsy (MTLE). METHODS: The authors analyzed electroclinical findings in 36 patients with MTLE with or without DP. Three DP types were defined (types I, II, III) corresponding to a gradual increase in duration and complexity. Interictal [18F]fluorodeoxyglucose-PET in different groups and subgroups was compared with control subjects using statistical parametric mapping software (SPM99). RESULTS: DP was found in 20 patients (55%), contralateral to the epileptogenic focus in 95%. Patients with DP had longer seizure duration, higher frequency of head deviation, salivation, motor manifestations, secondary generalization, severe clouding of consciousness, and prolonged postictal confusion when compared with patients without DP. Ictal discharge patterns during DP consisted of fast rhythmic activity spreading to frontal or suprasylvian areas, whereas slow rhythmic activity restricted to the temporal areas occurred in the absence of DP. In patients with DP, widespread temporal and extratemporal hypometabolism including the putamen was found. Hypometabolism was restricted to the anteromesial part of the temporal lobe and anterior insula in patients without DP. Putaminal hypometabolism was found in all DP types, but different extratemporal cortical involvements were found in DP subgroups: insula and inferior frontal gyrus in type I, inferior and superior frontal gyri and anterior cingulate gyrus in type II, and parietal areas in type III. CONCLUSION: Dystonic posturing may result from involvement of both putaminal and extratemporal cortical areas. Moreover, different frontal or parietal networks may be involved according to the duration or complexity of dystonic posturing.

[Adult supratentorial oligodendrogliomas. Surgical treatment: indications and techniques]. / Oligodendrogliomes supratentoriels de l'adulte. Traitement chirurgical: indications et techniques.

Surgical resection is the first step in the treatment of adult supratentorial oligodendrogliomas (OLG). However, the role of resection on prognosis, the most appropriate time for surgery along the natural history of those tumors, and the best operative strategy remain debated. Survival curves after resection vary greatly among reported series, in particular as a result of a persisting confusion in identification and classification of cerebral OLG. Surgical or stereotactic biopsy is the first surgical procedure which enables confirmation of the diagnosis suggested on imaging, assessment of extension of tumor cell infiltration beyond abnormalities limit described an imaging, and currently available molecular biology studies. Biopsies may be the only surgical procedure in patients having a deep-seated tumor with minimal mass effect, or prior to a surgical resection or a "wait and watch" strategy. Surgical resection is indicated for the other patients. However, it has not been demonstrated that time for resection has an influence on survival, excepted in patients with rapidly growing tumors, with mass effect causing increased intracranial pressure. A wait and watch strategy is therefore warranted in patients with a tumor aspect suggestive of a grade A OLG; surgical resection may be indicated later. There is a current trend for maximal safe resection, preserving functional cerebral areas, since truly complete resection of the tumor including infiltration is exceptional. However, from the contradictory results reported to date, one cannot ascertain whether large or complete resection based on imaging is associated with significantly longer survival. Neuronavigation guidance, intraoperative imaging, and cortical stimulation techniques are helpful neurosurgical techniques enabling maximal safe resection with preservation of functional areas.

[Results of the Sainte-Anne - Lyons series of 318 oligodendroglioma in adults]. / Résultats de la série Sainte-Anne - Lyon de 318 oligodendrogliomes intracrâniens de l'adulte.

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.

[Massive haemorrhage after dorsal decompressive laminectomy]. / Hémorragie massive après laminectomie dorsale décompressive.

We describe a case of a massive haemorrhage after dorsal decompressive laminectomy. The biological syndrome was at first a disseminated intravascular coagulation (DIC), rapidly complicated by a secondary fibrinolysis. The usual treatment of DIC with plasma and platelet transfusion failed to control bleeding and the patient underwent four repeat operations for relapsing rapidly evolving paraplegia. Aprotinine treatment stopped the haemorrhage. The vertebral metastasis causing spinal compression proved to be of prostatic origin.

GABAA receptor-dependent synchronization leads to ictogenesis in the human dysplastic cortex.

Patients with Taylor's type focal cortical dysplasia (FCD) present with seizures that are often medically intractable. Here, we attempted to identify the cellular and pharmacological mechanisms responsible for this epileptogenic state by using field potential and K+-selective recordings in neocortical slices obtained from epileptic patients with FCD and, for purposes of comparison, with mesial temporal lobe epilepsy (MTLE), an epileptic disorder that, at least in the neocortex, is not characterized by any obvious structural aberration of neuronal networks. Spontaneous epileptiform activity was induced in vitro by applying 4-aminopyridine (4AP)-containing medium. Under these conditions, we could identify in FCD slices a close temporal relationship between ictal activity onset and the occurrence of slow interictal-like events that were mainly contributed by GABAA receptor activation. We also found that in FCD slices, pharmacological procedures capable of decreasing or increasing GABAA receptor function abolished or potentiated ictal discharges, respectively. In addition, the initiation of ictal events in FCD tissue coincided with the occurrence of GABAA receptor-dependent interictal events leading to [K+]o elevations that were larger than those seen during the interictal period. Finally, by testing the effects induced by baclofen on epileptiform events generated by FCD and MTLE slices, we discovered that the function of GABAB receptors (presumably located at presynaptic inhibitory terminals) was markedly decreased in FCD tissue. Thus, epileptiform synchronization leading to in vitro ictal activity in the human FCD tissue is initiated by a synchronizing mechanism that paradoxically relies on GABAA receptor activation causing sizeable increases in [K+]o. This mechanism may be facilitated by the decreased ability of GABAB receptors to control GABA release from interneuron terminals.