[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.

Non-supervised spatio-temporal analysis of interictal magnetic spikes: comparison with intracerebral recordings.

OBJECTIVE: Our main goal was to evaluate the accuracy of an original non-supervised spatio-temporal magnetoencephalography (MEG) localization method used to characterize interictal spikes generators. METHODS: MEG and stereotactic intracerebral recordings (stereo-electro-encephalographic exploration, SEEG) data were analyzed independently in 4 patients. MEG localizations were performed with and without anatomical constraints. RESULTS: We analyzed 1326 interictal spikes recorded using MEG. For each patient, 2-3 typical source patterns were described. These source configurations were compared with SEEG. SEEG findings and MEG spatio-temporal localization results were remarkably coherent in our 4 patients. Most of the MEG patterns were similar to interictal SEEG patterns from a spatio-temporal point of view. CONCLUSIONS: We were able to evaluate the usefulness of our non-invasive localization method. This approach described correctly the part of the epileptogenic network involved in the generation of interictal events. Our results demonstrate the potential of MEG in the non-invasive spatio-temporal characterization of generators of interictal spikes.

The serotonergic innervation of the cerebral cortex in man and its changes in focal cortical dysplasia.

We present the morphology and the laminar distribution of the serotonin (5-hydroxytryptamine, 5-HT) innervation of the cerebral cortex of patients who underwent cortical resection for partial seizures. The limits of the resections were established by stereoelectroencephalography. The 5-HT innervation was mapped by using an antiserum anti-5-HT. Two patients had cryptogenic epilepsies and two others had seizures related to focal cortical dysplasia. 5-HT immunoreactive axons were morphologically heterogeneous and projected diffusely to the cerebral cortex with regional-specific densities. Two types of terminal axon were demonstrated. Type I had large and spherical (intensely immunoreactive) varicosities and was distributed sparsely with a characteristic predominance in the molecular layer. Type II had fine and pleiomorphic varicosities (granular or fusiform) and was distributed through all cortical layers. The distribution of the 5-HT innervation varied according to the different architectonic areas investigated. The granular cortical areas characterized by a highly developed layer IV (primary somatosensory, primary visual and prefrontal cortices) had the highest density of 5-HT-ir fibers distributed from layer I to layer V. The agranular primary motor cortex had the lowest density with fibers preferentially seen in layers I, IIIa and V-VI. The orbital cortex with a poorly defined layer IV had an intermediate density with a laminar repartition predominant in the supragranular layers. In patients with cryptogenic epilepsies, the brain epileptogenic tissue was histologically normal as well as the serotonergic innervation. In contrast, in patients with focal cortical dysplasia, the dysplastic epileptogenic tissue was characterized by a serotonergic hyperinnervation. In agreement with previous data in primates, we give morphological evidence for two morphologically distinct serotonergic subsystems and for regional specific densities in the human cerebral cortex. Moreover, we previously reported an altered pattern of the catecholaminergic innervation in the same dysplasia areas. All these results provide evidence that this development epileptogenic lesion involves several sets of neurons which may contribute to epileptogenic activity.

A methodology for generating normal and pathological brain perfusion SPECT images for evaluation of MRI/SPECT fusion methods: application in epilepsy.

Quantitative evaluation of brain MRI/SPECT fusion methods for normal and in particular pathological datasets is difficult, due to the frequent lack of relevant ground truth. We propose a methodology to generate MRI and SPECT datasets dedicated to the evaluation of MRI/SPECT fusion methods and illustrate the method when dealing with ictal SPECT. The method consists in generating normal or pathological SPECT data perfectly aligned with a high-resolution 3D T1-weighted MRI using realistic Monte Carlo simulations that closely reproduce the response of a SPECT imaging system. Anatomical input data for the SPECT simulations are obtained from this 3D T1-weighted MRI, while functional input data result from an inter-individual analysis of anatomically standardized SPECT data. The method makes it possible to control the 'brain perfusion' function by proposing a theoretical model of brain perfusion from measurements performed on real SPECT images. Our method provides an absolute gold standard for assessing MRI/SPECT registration method accuracy since, by construction, the SPECT data are perfectly registered with the MRI data. The proposed methodology has been applied to create a theoretical model of normal brain perfusion and ictal brain perfusion characteristic of mesial temporal lobe epilepsy. To approach realistic and unbiased perfusion models, real SPECT data were corrected for uniform attenuation, scatter and partial volume effect. An anatomic standardization was used to account for anatomic variability between subjects. Realistic simulations of normal and ictal SPECT deduced from these perfusion models are presented. The comparison of real and simulated SPECT images showed relative differences in regional activity concentration of less than 20% in most anatomical structures, for both normal and ictal data, suggesting realistic models of perfusion distributions for evaluation purposes. Inter-hemispheric asymmetry coefficients measured on simulated data were found within the range of asymmetry coefficients measured on corresponding real data. The features of the proposed approach are compared with those of other methods previously described to obtain datasets appropriate for the assessment of fusion methods.

Influence of the critical EEG pattern on blood flow variations measured by single photon computed emission tomography.

Anatomo-electro-clinical correlation's using stereo-electro-encephalography (SEEG) or electro-cortico-graphy (EcoG) are the gold standard for delineating the epileptic zone (EZ) in patients with partial epilepsy. These two techniques reflect the temporal and spatial dimensions of the epileptic fit. More recently, ictal Single Photon Computed Tomography (SPECT) compared with interictal SPECT allows anatomo-clinical correlations. SPECT reflects variations of the regional cerebral blood flow (rCBF) during the seizure. These variations of the rCBF are linked with the electrical activity but the relations between electrical activity and rCBF have not been well studied and it is still difficult to compare ictal/interictal SPECT with the SEEG and EcoG data to delineate the EZ. From the few published studies, we know that, if the injection of the SPECT tracer is performed at the onset of the seizure, while the fast ictal discharge is still going on, we shall observe a local hyperperfusion in the region where the discharge started and in the region where it propagated secondarily. If the tracer injection is performed late during the seizure, or after the end of it, we shall observe a local hypoperfusion in these regions, this has also a good localizing value. Time of injection must be known, as it represents a key issue for SPECT interpretation.

Gelastic seizures: video-EEG and scintigraphic analysis of a case with a frontal focus; review of the literature and pathophysiological hypotheses.

We report scalp EEG and SPECT findings in a young patient who experienced gelastic seizures; clinical, EEG and scintigraphic data strongly suggested a frontal focus in a context of cryptogenic epilepsy. Few cases of gelastic seizures originating in the frontal lobe have been reported in the literature, most of them involving a diencephalic hamartoma or a temporal focus although, no clinical pattern has been found to be specific for each of these three anatomical regions. The ictal laughter is of variable nature, unmotivated or associated with feelings of mirth, forced or natural, except in the case of a frontal focus where the laughter seems consistently described as forced and unmotivated. However, mirth and laughter are two dissociable clinical elements; their genesis probably involves distinct mechanisms. Anatomical considerations lead to several hypotheses concerning laughter generation: it could be a simple reactional behavior in response to a modified cognitive process, an automatic behavior or a forced action. In a few cases with a temporal focus, laughter seems directly related to a disorganization of the associative temporal cortex and may be considered as a reactional behavior. In cases with frontal focus, anterior cingulate and orbital structures would be particularly implicated in laughter genesis, although with possible different pathophysiological routes: in the first case by disconnection within the premotor mesial system or by an imbalance between premotor mesial and premotor lateral systems, and in the second case by activation of a previously conditioned orbital region.

Video-EEG and ictal SPECT in three patients with both epileptic and non-epileptic seizures.

We report scalp EEG and ictal SPECT findings in epileptic (complex partial) and non-epileptic seizures in three patients who experienced both types of event during presurgical investigation of medically intractable epilepsies. In all three patients, ictal SPECT showed localizing changes in cerebral blood flow during epileptic seizures, but showed no change during pseudoseizures. In two patients, the physical manifestations of the pseudoseizures were similar to those of the epileptic seizures, supporting the contention that physiological activation is unlikely to mimic ictal perfusion changes. In one patient, the EEG recording was rendered difficult to interpret by muscle artefact, while SPECT was clear and showed no change. SPECT is not a primary tool for diagnosis of pseudoseizures, but when patients undergoing presurgical investigation are injected during pseudoseizures, then SPECT is unlikely to show misleading perfusion changes due to activation effects, and may aid diagnosis where there is muscle artefact on EEG.

Treatment in tumours of the pineal region: value of sterotaxic biopsy.

The treatment of tumours of the pineal region is the subject of keen controversy between advocates of surgical excision and those of radiotherapy with ventricular shunting. The proponents of these extremes often seem to ignore the wide pathological variety of tumours of this site. Attempted excision of a germinoma invading the walls of the 3rd ventricle is as futile and dangerous as irradiation of a teratoma. Stereotaxic biopsy provides precise pathological diagnosis and thus allows more specific management; the procedure is safe and no serious complications were experienced in 25 cases.

Extracorporeal circulation with deep hypothermia and circulatory arrest in the treatment of intracranial arterial aneurysms.

Extracorporeal circulation with circulatory arrest and deep hypothermia in surgery on certain giant intracranial arterial aneurysms or on aneurysms difficult to access is described. The series includes a giant left carotid aneurysm, an aneurysm of the basilar artery bifurcation, a patient with two aneurysms, one on the right middle cerebral artery and the other at the end of the basilar artery, and a fourth patient with two aneurysms, one on the right middle cerebral and the other on the right carotid. Closed-thorax extracorporeal circulation with femoral cannulation was performed on all the patients. Surgical procedure is described and the advantages and disadvantages discussed. Results are encouraging. The authors suggest that the technique be used during surgical treatment of certain intracranial aneurysms that are in awkward positions or are very large in size. They emphasize that the procedure should be confined to exceptional cases.

A data fusion environment for multimodal and multi-informational neuronavigation.

OBJECTIVE: Part of the planning and performance of neurosurgery consists of determining target areas, areas to be avoided, landmark areas, and trajectories, all of which are components of the surgical script. Nowadays, neurosurgeons have access to multimodal medical imaging to support the definition of the surgical script. The purpose of this paper is to present a software environment developed by the authors that allows full multimodal and multi-informational planning as well as neuronavigation for epilepsy and tumor surgery. MATERIALS AND METHODS: We have developed a data fusion environment dedicated to neuronavigation around the Surgical Microscope Neuronavigator system (Carl Zeiss, Oberkochen, Germany). This environment includes registration, segmentation, 3D visualization, and interaction-applied tools. It provides the neuronavigation system with the multimodal information involved in the definition of the surgical script: lesional areas, sulci, ventricles segmented from magnetic resonance imaging (MRI), vessels segmented from magnetic resonance angiography (MRA), functional areas from magneto-encephalography (MEG), and functional magnetic resonance imaging (fMRI) for somatosensory, motor, or language activation. These data are considered to be relevant for the performance of the surgical procedure. The definition of each entity results from the same procedure: registration to the anatomical MRI data set (defined as the reference data set), segmentation, fused 3D display, selection of the relevant entities for the surgical step, encoding in 3D surface-based representation, and storage of the 3D surfaces in a file recognized by the neuronavigation software (STP 3.4, Leibinger; Freiburg, Germany). RESULTS: Multimodal neuronavigation is illustrated with two clinical cases for which multimodal information was introduced into the neuronavigation system. Lesional areas were used to define and follow the surgical path, sulci and vessels helped identify the anatomical environment of the surgical field, and, finally, MEG and fMRI functional information helped determine the position of functional high-risk areas. CONCLUSION: In this short evaluation, the ability to access preoperative multi-functional and anatomical data within the neuronavigation system was a valuable support for the surgical procedure.

[Contribution of stereotactic methods to diagnosis and treatment of tumors of the pineal region (author's transl)]. / Apport des techniques stéréotaxiques au diagnostic et au traitement des tumeurs de la région pinéale.

The respective role of surgical ablation versus palliative methods (i.e. shunting followed by irradiation) in the treatment of tumors of pineal region is still questionnable and must take into account the variability of their pathology. Thus, knowledge of tumoral type in each case is the first step to therapeutic discussion. The stereotactic methods allow a faithful biopsy, easy to interpret and without major risks.

[Indications and risks of neurosurgical techniques for drug-resistant partial epilepsy in adults]. / Indications et risques des techniques neurochirurgicales chez l'adulte pour l'épilepsie partielle pharmaco-résistante.

Many different surgical procedures are performed for medically refractory partial epilepsy. Some surgical therapies are performed to cure the epilepsy (for example unifocal epilepsy), others are palliative procedures. To cure epilepsy, temporal lobectomy is the most common surgical procedure. The different techniques are shortly described, indications and complications are discussed.

[The role of 3-dimensional reconstructions in the angiographic evaluation of cerebral vascular malformations: 3D morphometry]. / Place des reconstructions tri-dimensionnelles dans le bilan angiographique des malformations vasculaires cérébrales: le morphomètre 3D.

The need for medical images which can directly contribute to therapeutic decision making has led to the development of 3D visualization techniques. With this objective, a procedure capable of producing 3D volume reconstructions using isotropic voxels from digitalized 2D films obtained by rotation around the object has been developed: 3D morphometry. The technique has been assessed from 1993 through 1996 for vascular malformations in the brain, particularly aneurysms. Recognition of collateral vessels originating at the malformation was helpful in better identifying the lesions and evaluating possible therapeutic difficulties. The morphometric sequence thus is a possibility for the future assessment of neurovascular arches.

MR demonstration of spontaneous acute spinal subdural hematoma.

We report an unusual case of spontaneous acute spinal subdural hematoma. To date, only a few cases of magnetic resonance imaging (MRI) demonstration of such a pathology have been reported in the medical literature. We analyse the pathogenesis, clinical presentation, magnetic resonance imaging results, intraoperative findings and prognosis of this rare condition. We would like to stress that prompt and non-invasive diagnosis by MRI sagittal sections leads to efficient surgical treatment.

[Aspergillosis from sphenoidal sinus (author's transl)]. / Aspergillose pseudo-tumorale du sinus sphénoïdal (ou l'étiologie d'une paralysie unilatérale du III).

The authors describe an exceptional case of aspergillosis from sphenoidal sinus showed by oculomotar palsy its follow up simulates a malignant tumour.

[Test of a teleradiology network based on ATM (asynchronous transfer mode)]. / Essai d'un réseau de téléradiologie basé sur ATM (asynchronous transfer mode).

The retain project (Radiological Examination Transfer on ATM Integrated Network) consisted in teleradiology trials focused on pediatric imaging between two university hospitals. Rennes (France) and Barcelona (Spain) using an integrated broadband communication network based on ATM (asynchronous transfer mode), as part of a European research program. The network used was a full 10 Mbits/s ATM network directly connected to local PACSs (medical imaging hospital networks). One important reason to explicitly consider ATM for medical imaging is that multimedia applications on such networks allow integration of digital data and person-to-person communication. The utility of broadband communication for teleradiology has been confirmed. High quality video and sound are important for both human communication and medical video transfer. The project led to guidelines regarding technical options still open to improvement.

A ray-traced texture mapping for enhanced virtuality in image-guided neurosurgery.

3D imaging systems and algorithms give virtual representations of the real world. New emergent hardware systems can combine virtual information and the real world. Virtual and real information must be also visually confronted in order to facilitate our comprehension of the data. We propose a solution which entails the superimposition of a real image of the anatomical areas visualised in a surgical operation with 3D digital data sets. Unlike other solutions which display virtual images in the real world, our method involves ray traced texture mapping which displays real images in a computed world.

[The place of surgery in the treatment of supra-tentorial malignant gliomas (author's transl)]. / Place de la chirurgie dans le traitement des gliomes malins supra-tentoriels.

The natural history of malignant gliomas is compared to the mean survival duration after surgery alone and/or surgery associated with radiotherapy and chemotherapy. In the state of the art a combined treatment by surgery and roentgentherapy offers the best prognosis but does not allow for more than 35% of expectation of life at the end of the first year. According to the severity of the general prognosis the present authors advocate a strict care for the functional integrity. An improved knowledge in the biology of cerebral gliomas justifies further consideration in the surgical treatment preparing the expected effects of radiotherapy and chemotherapy.

[Sulcal identification and neuronavigation in supratentorial cavernoma surgery]. / Repérage sulcal et neuronavigation dans la chirurgie des cavernomes supratentoriels.

We present the use of cortical sulci, segmented from magnetic resonance imaging, in image guided neurosurgery. Sulcal information was transferred to a surgical microscope with enhanced reality features. This assistance was used for the resection of supratentorial cavernomas (7 patients). Sulci were semi-automatically segmented from 3D MRI data sets. Sulci close to the cavernoma were selected and transferred to the neuronavigation system which allows the superimposition of graphics into the right ocular of the microscope. Selected sulci were displayed on the workstation and superimposed into the ocular of the microscope. Cortical sulci proved to be useful for the recognition of the anatomical environment. The superimposed sulci helped to optimize location and size of the skin incision as well as to guide the access to the cavernoma by using the course of a sulcus as indirect trajectory.

[Functional imaging of the auditory cortex: role of magnetoencephalography]. / Imagerie fonctionelle du cortex auditif. Place de la magnétoencéphalographie.

We present the different methods for detecting cerebral activity in the auditory cortex. Positron emission tomography (PET) and functional MRI (fMRI) measure such activity indirectly by calculating the blood flow rate or the consumption of oxygen. The direct methods of detection record the electrical or magnetic activity by eletroencephalography (EEG), or magnetoencephalography (MEG), respectively. The aim of this study was to define the role of MEG amongst these different techniques using the data from recordings of evoked magnetic fields in 5 healthy subjects. The localizations demonstrated the tonotopic organization of the auditory cortex, with high-pitched sounds showing a more medial cortical projection than low-pitched sounds. These various techniques are complementary. PET allows a pharmacological study of the cortex, and could be used in patients with cochlear implants. FMRI is non-invasive, and has a high spatial resolution. EEG has an excellent temporal resolution, and EEG recordings do not require major equipment or infrastructure. MEG has a better spatial resolution, with the same temporal resolution, as EEC. MEG is particularly useful in the localization of the cortical generators of middle-latency auditory evoked responses.