[On the best strategies on the best results for surgery of frontal epilepsy]

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]

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.

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.

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.

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.

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.

[Functional imaging of the auditory cortex: role of magnetoencephalography]

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.

[Sulcal identification and neuronavigation in supratentorial cavernoma surgery]

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.

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.

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.

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.

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.

[The role of 3-dimensional reconstructions in the angiographic evaluation of cerebral vascular malformations: 3D morphometry]

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.

Microsurgical anatomy of the anterior choroidal artery

In this study, the authors present the results of 50 dissections of the anterior choroidal a. in man. Fifty cerebral hemispheres were prepared with the classic techniques of preservation and vascular injection. An ectopic origin was observed in 4% of cases. The intracisternal segment of the anterior choroidal a. forms a neurovascular bundle with the optic tract and basal v. Most of its intraparenchymatous branches arise from the cisternal segment, while branches supplying the optic tract, lateral geniculate body and thalamus arise from the intraplexual segment. Constant anastomoses exist with the vertebrobasilar system, specially the postero-lateral choroidal and posterior cerebral aa. We discuss the importance of an adequate knowledge of the anatomy of the anterior choroidal a. and its relations in the surgical approach to arterial aneurysms and arteriovenous malformations of the region.

[Test of a teleradiology network based on 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.

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 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.

Auditory and visual sensory representations in human prefrontal cortex as revealed by stimulus-evoked spike-wave complexes

Multimodal sensory properties of the prefrontal cortex have been extensively studied in monkeys, while little is known of such functions in humans. We report electrophysiological evidence for auditory and visual representations in the dorsolateral prefrontal cortex, as inferred from intracerebral 'depth' recordings of focal, sensory-evoked spike-wave complexes (SWC) in an epileptic patient. In addition to clinical monitoring, the patient participated in behavioural evoked potential studies involving auditory and visual discrimination tasks. Inspection of evoked potential recordings from different medial-to-lateral prefrontal sites revealed overlapping, but non-identical topographies of evoked SWC for the two sensory modalities. The maximal activity of sensory-evoked SWC was located 7 mm more medially for visual than for auditory stimuli, and occurred later for visual presentations (mean = 117 ms following stimulus onset) than for auditory ones (mean = 87 ms). Effects of sensory habituation were seen. Evoked SWC were less likely to occur following repeated presentations of an unchanging tone than when tones alternated in pitch, or when a tone followed an omission in stimulus presentation. Visual hemifield effects were found, with greater prefrontal responsiveness to presentations in the contralateral visual hemifield. These results are consistent with electrophysiological findings in animals indicating overlapping auditory and visual representations in the dorsolateral prefrontal cortex.

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.

[Dimensions of the aortic ring. Anatomic and surgical study of 2 series of patients]

Both surgical (236 aortic valve replacements) and anatomical (62 dissections) studies have defined the aortic annulus diameter. Measurements (23.5 mm for women; 26 mm for men) are more considerable than established values. Furthermore, surgical study allows the authors to compare these results to several variables, more especially corporeal surface and stature: the height's increase perhaps explains the large sizes discovered.

[Aspergillosis from sphenoidal sinus (author's transl)]

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

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.

[Deep femoral artery. Anatomoradiological study]

After a double study (anatomical--50 dissections--and radiological--100 arteriograms) the following points can be stressed: the femoral tripod is only found in 38 per cent of the cases. One or several nutrient arteries of the thigh originate often separately (62% of cases). Their origine is situated highup in a number of cases (at 3 cm below the inguinal ligament). The collateral network develops from each of the arteries forming a complete "profunda femoris system". Two surgical consequences deserve to be underlined: 1. The approach to all the branches is possible by a transverse incision in the fold of the groin. 2. Surgical revascularisation must concern the whole of the "profunda femoris" network.

[Thoracopagus. Possibilities of surgical separation]

A new case of thoracopagus twins is reported. Radiological, hemodynamical and surgical explorations showed a communication between the two hearts, situated at the atrial level and associated with digestive and cardiovascular malformations. These abnormalities were definned by the anatomical study realized after vascular injection:hypoplastic pulmonary artery (associated with a persistent atrio-ventricular canal in one case, with a tricuspid atresia in the other case), a large fused liver, common pancreas and ileum. A bibliographic study allows the authors to define surgical separation possibilities. The prognosis depends essentially on cardiovascular abnormalities associating abnormal connections between the twins' hearts with malformations often too severe for surgical repair.

[Abnormal fusion of 2 primitive trigeminal arteries: apropos of an anatomo-radiological case]

Agenesis of the internal carotid artery was discovered during emergency cerebral angiography carried out on a comatose 28 year old man. The left cerebral hemisphere was supplied from the controlateral carotid artery, via a large vessel running through the sphenoid bone, between the intracavernous portions of the internal carotid arteries. Postmortem examination showed that death resulted from massive haemorrhagic infarction of the cerebellum and brain stem. Absence of the cervical and petrosal portions of the left internal carotid artery was confirmed. The anastomotic vessel was found to run through the spongiosa below the dorsum sellae. The heart, major vessels and circle of Willis were otherwise normal. An intercarotid anastomosis of this type has been reported on three previous occasions, in none of which was there anatomical confirmation.

[Diagnosis of hyperprolactinaemias: respective value of response to THR and to bromocriptine (author's transl)]

Seventy tests of stimulation with hypothalamic thyreotrophic hormone liberation factor, and 35 bromocriptine inhibition tests were carried out on a routine basis in patients with latent or frank hyperprolactinaemia. Pathological hyperprolactinaemia does not have a single clinical pattern: frank, it takes the form either of an exteriorised pituitary adenoma (14 cases), or of an amenorrhoea-galactorrhoea syndrome with or without micro-adenoma (12 cases); latent, it takes the form either of isolated amenorrhoea (17 cases) or of dysovulatory sterility (16 cases). Amongst the dynamic tests available, it is worthwhile to make a choice, and in the case of frank hyperprolactinaemia, the authors propose use of the bromocriptine inhibition test in the first instance. The TRH test is reserved for verification of the results of neurosurgery. As far as latent hyperprolactinaemia is concerned, it may be identify only by the TRH test, with the resultant possibility of specific treatment.

[Contribution of stereotactic methods to diagnosis and treatment of tumors of the pineal region (author's transl)]

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.

[Comparative study of afferent connections in the habenula in rats and cats after injection of horseradish peroxidase]

The habenular complex of 11 cats and 13 rats was injected with horse Radish peroxydase (HRP) (30% solution, 0,05--0,4 microliter). Retrograde labelling of cells was visualized after a survival period of 24 to 48 hours by means of the method of Lavail et al. (1973). The resultats obtained with this method suggest significant species differences regarding the habenular afferents in cats and rats. One of the most striking differences is that the entopeduncular nucleus of the cat contains very few HRP labelled cells after lateral habenular nucleus injection in comparison to the entopeduncular nucleus of the rat which can be shown to be the major source of afferents to the lateral habenular nucleus by the same method.

Stereotaxic exploration in 200 supratentorial brain tumors. Its value in addition to computerized tomography

The authors emphasize the advantages of stereotaxic methodology in the management of 200 brain tumors. Nowadays computerized tomography is the first stage of radiologic diagnosis. Both CT scan and stereotaxic examination have been carried out in more than 35% of these tumors. Rather than a comparison of the two examinations, the authors' purpose is to attempt to demonstrate their complementarity in the assessment of location, volume, and nature of the lesion and eventually in the choice of a therapeutic attitude. Analysis of topographic data and staged biopsies, gathered from the 'stereotaxic space,' provides the neurosurgeon with accurate information for planned surgical excision or interstitial irradiation.

[Calculation of the volume of the grafted kidney. Value of this measurement by echotomography in renal transplantation]

From a necropsy series of 14 kidneys, it is very easy to prove, that there is a quite good correlation between the theorical calculated volume of the kidney and its real volume. It is possible to compare the kidney to an ovoid, and to calculate its volume, knowing the 3 dimensions which are its length, its width, its depth. In this way, by echotomography it is possible to estimate these three parameters at the level of the transplanted and to calculate the volume and if, after two successive examinations of control, the kidney volume is found to be enlarged (over 20%) a reject phenomenon must be diagnozed.

Role of the pneumo-encephalogram in the diagnosis of spontaneous subarachnoid haemorrhage

The authors have collected eighteen cases of primary intraventricular lesions revealed by a subarachnoid haemorrhage. Among these cases, the most important are the choroid plexus papillomas followed by ependymomas; some cases have no precise histological interpretation. Generally speaking, cerebral arteriography gives only indirect evidence of ventricular dilation and thus does not confirm the presence of a lesion. On the contrary, the pneumoencephalogram is consistantly positive, but does not give the differential diagnosis between intraventricular tumours and primary intraventricular haemorrhages. This test should therefore be given the same importance as spinal cord arteriography in the exploration of subarachnoid haemorrhages with negative cerebral angiograms.