[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.

[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.

Unilateral spatial neglect following right inferior parietal cortectomy.

Research in brain-damaged patients has suggested that the right hemisphere plays a role in unilateral spatial neglect (USN), but provides only limited information for pinpointing the intraparietal localization of the lesions associated with this syndrome. We report a case of unilateral neglect in a patient who underwent a right inferior parietal cortectomy for refractory epilepsy without any macroscopic lesion. We describe the evolution of the neuropsychological disturbances observed at 3 and 24 months after cortectomy. This case illustrates the role played by the inferior parietal lobe and, particularly, the parietal opercule in USN syndrome, and provides strong "experimental" evidence of the special role played by the inferior parietal lobule in the perception processes related to spatial attention.

Mutations within the MGC4607 gene cause cerebral cavernous malformations.

Cerebral cavernous malformations (CCM) are hamartomatous vascular malformations characterized by abnormally enlarged capillary cavities without intervening brain parenchyma. They cause seizures and focal neurological deficits due to cerebral hemorrhages. CCM loci have already been assigned to chromosomes 7q (CCM1), 7p (CCM2), and 3q (CCM3) and have been identified in 40%, 20%, and 40%, respectively, of families with CCM. Loss-of-function mutations have been identified in CCM1/KRIT1, the sole CCM gene identified to date. We report here the identification of MGC4607 as the CCM2 gene. We first reduced the size of the CCM2 interval from 22 cM to 7.5 cM by genetic linkage analysis. We then hypothesized that large deletions might be involved in the disorder, as already reported in other hamartomatous conditions, such as tuberous sclerosis or neurofibromatosis. We performed a high-density microsatellite genotyping of this 7.5-cM interval to search for putative null alleles in 30 unrelated families, and we identified, in 2 unrelated families, null alleles that were the result of deletions within a 350-kb interval flanked by markers D7S478 and D7S621. Additional microsatellite and single-nucleotide polymorphism genotyping showed that these two distinct deletions overlapped and that both of the two deleted the first exon of MGC4607, a known gene of unknown function. In both families, one of the two MGC4607 transcripts was not detected. We then identified eight additional point mutations within MGC4607 in eight of the remaining families. One of them led to the alteration of the initiation codon and five of them to a premature termination codon, including one nonsense, one frameshift, and three splice-site mutations. All these mutations cosegregated with the disease in the families and were not observed in 192 control chromosomes. MGC4607 is so far unrelated to any known gene family. Its implication in CCMs strongly suggests that it is a new player in vascular morphogenesis.

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.

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.

Fear as the main feature of epileptic seizures.

OBJECTIVES: There are circumstances in which partial seizures may be misdiagnosed as acute psychiatric disturbances. In particular, when fear is the prominent feature the patient may be considered for years as having panic attacks. Eight patients in whom fear was the main symptom of the seizures are reported on. Patients who had a proved lack of consciousness during the fits and patients in whom fear was just fear of having a seizure were excluded. The ictal involvement of temporal limbic and frontal structures in those patients with fear of particular intensity was studied. METHODS: The localisation of the epileptogenic zone was assessed by prolonged interictal EEG recordings as well as ictal video-EEG recording of at least one seizure in every patient; five had ictal SPECT and four had chronic stereotactic implantation of depth electrodes (SEEG). In six patients, a cortical resection was performed with an Engel's class 1 outcome (minimum 28 months follow up, except for two patients). RESULTS: Localisations of primary epileptogenic zones were right temporal in three patients, left temporal in three, bitemporal in one, and frontal in one. In all cases, diagnosis of epileptic seizures could be clinically evoked because of the stereotypy of fits and of associated symptoms. The association of a fear sensation, autonomic symptoms, and coordinated behaviour suggests disturbance of a particular system. The SEEG data argue for temporolimbic and prefrontal lobe involvement in the expression of ictal fear. CONCLUSIONS: In intense ictal fear, with coordinated behaviour and autonomic features, the discharge may involve or interfere with a physiological complex information processing network. This network involves orbitoprefrontal, anterior cingulate, and temporal limbic cortices.

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.

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.

The RETAIN project: DICOM teleradiology over an ATM-based network. Radiological Examinations Transfer on an ATM Integrated Network.

The RETAIN project (Radiological Examinations Transfer on an ATM Integrated Network) has aimed at testing videoconferencing and DICOM image transfers to get advice about difficult radiological cases over an asynchronous transfer mode (ATM)-based network, which affords a more comfortable interface than narrow-band networks and allows exchange of complete image series using the DICOM format of studies. For this purpose, an experimental ATM network was applied between six university hospitals in four different countries. An assessment of the functionalities of the system was performed by means of log-file analysis, video recording of the sessions and forms filled out by the participants at the end of each session. Questionnaires were answered by the users at the end of the project to bring out perspectives of utilisation and added value. We discussed 43 cases during 20 sessions. For technical or organisational problems, only 20 of the 36 planned sessions took place. The throughput over ATM (10.5 Mbit/s, 20 times faster than six ISDN B-channels) was adequate. Despite the experimental configuration of the network, the system was considered as satisfactory by all the physicians. In 72 % of the sessions, the expected result (answer to the question) was gained. By common consent, videoconferencing was unanimously regarded as a prominent tool in improving the interaction quality. Asynchronous transfer mode is an efficient method for fast transferring of radiologic examinations in DICOM format and for discussing them through high-quality videoconferencing.

[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.

Anatomic bases for the compression and neurolysis of the deep branch of the radial nerve in the radial tunnel.

The anatomy of the radial tunnel was studied on twenty-five elbow preparations. We noted five different elements that could affect the deep branch of the radial nerve in the radial tunnel and cause an entrapment syndrome: a capsule-tendon-aponeurotic complex on the anterior aspect of both the humeroradial joint and the radial head, the vascular arcade formed by the radial recurrent a, and its branches, the arcade formed by the medial edge of extensor carpi radialis brevis muscle, and the superior and inferior arcades of the superficial layer of the supinator muscle. These results are compared with recent anatomical and clinical data, and the relevance of a surgical approach between the extensor carpi radialis brevis and longus muscles is discussed.

Opercular reflex seizures: a case report with stereo-electroencephalographic demonstration.

Reflex epileptic seizures of opercular origin have been described previously based on video-electroencephalographic monitoring, but very few patients have been explored with depth electrodes. We report a woman with late-onset epilepsy who had intractable seizures despite trials of several antiepileptic drugs. At the time of the depth-electrode recordings, seizures were usually continuous and occurred either spontaneously or were induced by movements of the jaw and mouth. The seizures originated in the deep central opercular cortex; localization was confirmed by a good surgical outcome.

Influence of the teleradiology technology (N-ISDN and ATM) on the inter-hospital management of neurosurgical patients.

We set out to assess the influence of a teleradiology network on the relations between a general hospital and a 100 km distant university hospital in the context of neurosurgical emergencies, and compared a commercially available technology, N-ISDN (Narrowband Integrated Service/Digital Network), to an emerging technology, ATM (Asynchronous Transfer Mode). The evaluation was conducted using records of advice request calls and patient transfers. Three phases were considered: without teleradiology, with transfer of digitized images over N-ISDN at 64 kbps, and with an experimental ATM network at 10.5 Mbps with DICOM image transfers and videoconferencing. Additionally, staff meetings over ATM videoconferencing were set up. To assess the ATM service, we used log files and questionnaires, 108 advice requests were studied over a 18 month period. The average transmission time for one examination was 38 s with full DICOM image resolution over ATM, versus 150 s with 10:1 JPEG (Joint Photographic Expert Group) compression over N-ISDN. Up to 50% unnecessary patient transfers were avoided. Advice requests increased fourfold, and non-urgent advice requests increased from 0 to 21%. Despite the experimental configuration of the ATM network, the service gave satisfaction to all the physicians. Videoconferencing was unanimously regarded as a prominent tool to improve the quality of interaction. It was particularly useful for non-urgent cases and distant staff meetings. Teleradiology can improve the relations between hospitals through an increase of urgent and non-urgent advice requests. Asynchronous transfer mode is an efficient way for fast transfer of radiological examinations in DICOM format and for discussing them through high-quality videoconferencing.

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.

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.

Analysis of cerebrovascular diseases by a new 3-dimensional computerised X-ray angiography system.

We set out to validate the concept of three-dimensional (3D) angiography. We evaluated the sensitivity and the quality of morphological analysis mode possible by an experimental system for imaging cerebrovascular disease versus standard digital subtraction angiography (DSA). The system, the 3D Morphometer, is a computerised X-ray angiography unit capable of acquiring a set of two-dimensional (2D) projections during a rotation and then reconstructing a 3D volume from them. We studied 78 patients with suspected cerebrovascular disease. 3D and 2D images (standard 2D DSA performed during the same procedure), were reviewed blindly to assess detection and display of morphological characteristics of cerebrovascular diseases. We found 53 aneurysms, 22 arteriovenous malformations and two venous angiomas. On 3D angiography we detected two aneurysms we missed on 2D angiography. In 47 aneurysms on which further data were obtained during surgery or embolisation, the 3D angiography allowed more accurate analysis of the neck and surrounding vessels in cases in which the 2D angiographic findings were doubtful. Assessment of arteriovenous malformations was equivalent with both techniques. Under the conditions of our study, the technical constraints being the same for both methods, 3D angiography was superior to 2D angiography. Implementation on C-arm vascular systems is being evaluated.

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.