Biomedical subjects

J Isnard

Publications and source records attributed to J Isnard.

At least 19 recordsLinked to original sources

PubMed2006

[Vertebrovertebral arteriovenous fistula diagnosis and treatment: report of 8 cases and review of the literature].

Vertebrovertebral Arteriovenous Fistula (V.V.A.V.F.) is a relatively rare entity. It may be an incidental finding or be detected in patients presenting with pulsatile tinnitus, cervical bruit, or vertebro-basilar insufficiency. It can be spontaneous but it most frequently is post-traumatic in etiology. The authors report 8 patients, 4 women and 4 men aged between 20 to 77 years, with 4 post-traumatic V.V.A.V.F. and 4 spontaneous V.V.A.V.F. that were seen over a 15 year period. Imaging work-up included Doppler US (n=4), MRI 9n=3) and angiography (n=8). Seven of 8 patients were treated successfully using an endovascular technique (5 with balloon occlusion, 1 with coil embolization and 1 using a mechanical maneuver), without complication or recurrence, except in one case. We compare our results with published reports from the literature and review the underlying pathology and management strategies of V.V.A.V.F.

Adult↗

PubMed2006

[Value of multidetector-row computed tomography for infantile renovascular hypertension: report of two cases].

The work-up of renovascular hypertension (10% of children hypertension cases) benefits from multiple imaging modalities. These two cases show the difficulties encountered with infant and underscore "the major role" of the computed tomography angiography within for diagnosis and management. Indeed CTA allows reproducible studies of abdominal vessels at the expense of radiation exposure.

Female↗

PubMed2005

Temporo-mesial epilepsy surgery: outcome and complications in 100 consecutive adult patients.

BACKGROUND: We studied the surgical outcome, and the complications in a group of 100 consecutive adult patients with medically refractory epilepsy arising from the temporo-mesial structures. METHODS: Hundred patients were treated surgically between 1994 and 2003 for drug-resistant epilepsy involving the temporo-mesial structures. All of them underwent a comprehensive noninvasive presurgical evaluation. Fourty-eight of them underwent depth electrodes recordings (according to the Talairach's StereoElectroEncephaloGraphic (SEEG) methodology) because the noninvasive investigations were not congruent enough to identify the epileptic zone. The patients presenting with any space-occupying lesion, or with a cavernoma, or with a strictly lateral neocortical epileptic focus, were excluded. The MRI-examination was abnormal in 87 cases, displaying a hippocampal atrophy in 69 cases. The extent of temporal resection was planned according to the results of the presurgical investigation in each particular patient. Consequently, this "tailored" resection varied from selective amygdalo-hippocampectomy (6 cases), to anterior temporal lobectomy (76 cases), or to total temporal lobectomy (18 cases). FINDINGS: The mean post-operative follow-up period was 53 months. 85 patients were found to be in Engel's class I post-operatively (free of disabling seizures), among them 74 were in class Ia (totally seizure free). Nine patients were in Engel's class II and six were in Engel's class III or IV (failures). There was no surgical mortality. Three patients had a postoperative hematoma; two patients required a shunt insertion; in three patients meningitis occurred; and two patients had postoperative ischaemia of the anterior choroidal artery territory, which resulted in a mild permanent hemiparesis. Neuropsychological complications are not addressed in detail in this article. CONCLUSIONS: These data indicate that "tailored" resective surgery for temporo-mesial epilepsy can be performed with a low rate of morbidity, and is highly efficacious. The use of invasive presurgical investigation (SEEG) may explain this high rate of success.

Adolescent↗

PubMed2005

Somatosensory and pain responses to stimulation of the second somatosensory area (SII) in humans. A comparison with SI and insular responses.

Somatosensory and pain responses to direct intracerebral stimulations of the SII area were obtained in 14 patients referred for epilepsy surgery. Stimulations were delivered using transopercular electrodes exploring the parietal opercular cortex (SII area), the suprasylvian parietal cortex (SI area) and the insular cortex. SII responses were compared to those from adjacent SI and insular cortex. In the three areas we elicited mostly somatosensory responses, including paresthesiae, temperature and pain sensations. The rate of painful sensations (10%) was similar in SII and in the insula, while no painful sensation was evoked in SI. A few non-somatosensory responses were evoked by SII stimulation. Conversely various types of non-somatosensory responses (auditory, vegetative, vestibular, olfacto-gustatory, etc.) were evoked only by insular stimulation, confirming that SII, like SI, are mostly devoted to the processing of somatosensory inputs whereas the insular cortex is a polymodal area. We also found differences in size and lateralization of skin projection fields of evoked sensations between the three studied areas, showing a spatial resolution of the somatotopic map in SII intermediate between those found in SI and insula. This study shows the existence of three distinct somatosensory maps in the suprasylvian, opercular and insular regions, and separate pain representations in SII and insular cortex.

Adult↗

PubMed2005

Hippocampal-orbitofrontal connectivity in human: an electrical stimulation study.

OBJECTIVE: The identification of the pathways involved in seizure propagation remains poorly understood in humans. For instance, the respective role of the orbitofrontal cortex (OFC) and of the commissural pathways in the interhemispheric propagation of mesial temporal lobe seizures (mTLS) is a matter of debate. In order to address this issue, we have directly tested the functional connectivity between the hippocampus and the OFC in 3 epileptic patients undergoing an intra-cranial stereotactic EEG investigation. METHODS: Bipolar electrical stimulations, consisting of two series of 25 pulses of 1 ms duration, 0.2 Hz frequency, and 3 mA intensity, were delivered in the hippocampus. Evoked potentials (EPs) were analysed for each series, separately. Grand average of reproducible EPs was then used to calculate latency of the first peak of each individual potential. RESULTS: Hippocampal stimulations evoked reproducible responses in the OFC in all 3 patients, with a mean latency of the first peak of 222 ms (range: 185-258 ms). CONCLUSIONS: Our data confirm a functional connectivity between the hippocampus and the OFC in human. SIGNIFICANCE: This connectivity supports the potential role of the OFC in the propagation of mTLS.

Adolescent↗

PubMed2005

[The insula in partial epilepsy].

The role of the insular lobe in temporal lobe epilepsy (TLE) has often been suggested but never directly demonstrated. In this article, we review data from recent literature and from our stereo-electroencephalographic (SEEG) recordings in patients referred for temporal lobe epilepsy surgery (TLE). Our description of the clinical features of insular lobe seizures is based on data from video and SEEG ictal recordings and direct electric cortical stimulation in a population of 50 consecutive patients whose seizures, on the basis of scalp video EEG recordings, were suspected to originate from, or to rapidly propagate to, the peri-sylvian cortex. A total of 144 intra-insular electrodes have been implanted in this series of patients. In six patients a stereotyped sequence of ictal symptoms could be identified on the basis of electro-clinical correlations. The clinical presentation of insular lobe seizures was that of simple partial seizures occurring in full consciousness, beginning with a sensation of laryngeal constriction followed by paresthesiae that were often unpleasant affecting large cutaneous territories. These initial symptoms were eventually followed by dysarthric speech and/or elementary auditory hallucinations, and seizures often ended with focal dystonic postures. The insular origin of these symptoms was supported by the data from functional cortical mapping of the insula using direct cortical stimulations. We were able to reproduce several of the spontaneous ictal symptoms in the six patients with insular seizures. Moreover, from the whole set of insular stimulations that we performed it could be concluded that the insular cortex is involved in somatic, vegetative and visceral functions to which spontaneous ictal insular symptoms are related. The observation of the insular symptoms sequence at the onset of seizures in patients who are candidates for TLE surgery strongly suggests that the epileptic focus is located in the insular lobe. It entails the risk of unsuccessful temporal lobectomy and should lead: i) to reconsider the indication of temporal lobectomy and; ii) to explore directly the ictal activity of both mesio-temporal and insular cortices before making any decision regarding epilepsy surgery.

Cerebral Cortex↗

PubMed2004

Intracranial EEG study of seizure-associated nose wiping.

The authors studied the relation between seizure-associated nose wiping (NW) and intracerebral EEG data in 32 patients. NW was more frequent in mesial temporal lobe seizures (TLSs; 65%) than in other TLSs (36%; p < 0.05) and in frontal lobe seizures (3%; p < 0.0001). It was associated with the presence of an amygdala discharge at seizure onset (p < 0.05) and with the recording of an ictal low-voltage fast activity within that structure (p < 0.05), supporting the role of an amygdala dysfunction in the pathophysiology of NW.

Adolescent↗

PubMed2004

Intraoperative electrical stimulation mapping as an aid for surgery of intracranial lesions involving motor areas in children.

OBJECTIVE: We analysed the usefulness of intraoperative electrical stimulation mapping (ESM) for locating motor pathways in pediatric patients harboring cerebral lesions closely related to motor areas. METHODS: We applied ESM in 17 consecutive pediatric patients operated on under general anesthesia. It was possible to locate motor function in 15 patients and in all children 5 years old and younger, as well as in all patients presenting with severe motor deficits, using relatively high current intensities. Intraoperative seizures occurred in 20% of our patients. A macroscopically complete removal of the lesion was carried out in 12 cases out of 17 with no definitive postoperative aggravation. Motor function improved for all patients presenting preoperatively with a severe paresis. CONCLUSION: In our experience ESM revealed to be an useful tool for allowing us to push the resection of any lesion infringing on eloquent cortex up to the limit of functional areas, even in cases in very young and severely paretic children.

Adolescent↗

PubMed2004

Surgical anatomy of the insula.

The insula is the only cortical part of the brain which is not visible on the surface of the hemisphere. This is due to the fact that it is totally covered by the fronto-parietal and temporal opercula. The insula has a triangular shape, and is separated from the opercula by the anterior, superior, and inferior periinsular sulci. The limen insulae is the antero-inferiorly located insular cortical surface which conjoins the inferior insular point, the anterior perforated surface, and the temporo-mesial surface. The insula is morphologically divided into two parts by the central insular sulcus. The anterior part of the insula bears 3 gyri: the anterior, middle, and posterior short insular gyri, separated by the anterior and precentral insular sulcus. The posterior part of the insula contains the anterior and posterior long insular gyri, separated by the postcentral insular sulcus. The vascular supply of the insula is mainly provided by the M2 segment of the middle cerebral artery, which constitutes a substantial obstacle to any open or stereotactic procedure aiming at the insular region. Histologically, the insula is a part of the paralimbic cortex, as it bears in its antero-inferior part an allo and mesocortical area. The insula is functionally involved in cardiac rhythm and arterial blood pressure control, as well as in viscero-motor control and in viscero-sensitive functions. There is considerable evidence for the involvement of the insula as a somesthetic area, including a major role in the processing of nociceptive inputs. Its possible role in some epilepsies may explain some failures of temporal lobe resection. Surgery of the insular lobe is a technical challenge, whose risks can be minimized by the use of intra-operative direct cerebral stimulation.

Animals↗

PubMed2004

[Drug-resistant partial epilepsy. Invasive electrophysiological explorations].

During the past 20 years, advances in neuroimaging techniques have greatly improved the surgery of epilepsy. Nevertheless, for fifty percent of epileptic patients undergoing such surgery procedures, recordings with chronically implanted intracerebral electrodes are necessary to localize the epileptic focus. Since the fifties, these electrodes have been used to record the cerebral cortex during the surgical procedure. Due to technological progress, these electrodes can now be left implanted for several days to record the inter- and per-ictal electroencephalogram (EEG). In comparison with scalp recordings, intracortical assessment of epileptic patients allows exploring the cortical epileptic network with a higher spatial resolution and less artefacts. Moreover, this technique enables performing direct cortical electrical stimulation to map functionally eloquent cortices and epileptogenic areas. Each type of depth electrodes has been developed for a specific use. In this work, we review the different solutions used at the present time, their specific indications and finally their advantages and disadvantages. Moreover, we mention the new emerging therapeutic indications.

Brain↗

PubMed2003

Technical refinements for validating functional MRI-based neuronavigation data by electrical stimulation during cortical language mapping.

Preoperative functional neuroimaging techniques represent an appealing method to localize language areas in tumor surgery, but their reliability still needs to be confirmed by accurate comparison with more invasive but validated mapping techniques like intraoperative electrical cortical stimulation. Two patients harboring a glioma involving speech areas underwent mapping of language function by preoperative functional magnetic resonance imaging (fMRI), whose results were integrated into the neuronavigation device, and by intraoperative electrical stimulation mapping (ESM). The utilization of neuronavigation allowed us to estimate the degree of spatial correspondence between language areas detected by the two techniques. Language areas identified by functional magnetic resonance imaging on the cerebral cortex exposed during surgery corresponded to those identified by invasive mapping in both patients. It was possible to achieve a gross total tumor removal while respecting language areas in both cases, with no permanent postoperative phasic aggravation. The concordance of results between pre- and intraoperative mapping techniques in our patients indicates that preoperative fMRI language mapping may prove useful when planning the resection of intracerebral lesions in language areas. However, accurate neurofunctional imaging protocols and image analysis are crucial to obtain a preoperative language mapping that is in agreement with ESM findings.

Brain Mapping↗

PubMed2001

The value of cortical stimulation applied to the surgery of malignant gliomas in language areas.

This study analyzes the utility of peroperative cortical language mapping applied to the surgery of high-grade gliomas situated within or in close vicinity to speech areas. Fifteen consecutive patients harboring high-grade gliomas located in the dominant hemisphere, causing regressive or minor language troubles, underwent awake craniotomy in our institution between June 1998 and April 2000. The technique of cortical stimulation under local anesthesia for language mapping, initially described by Ojemann and colleagues, was applied with some modifications. All patients tolerated awake craniotomy except one, who was intubated after the mapping procedure. Mapping results confirmed a high variability in location of language sites. It was possible to achieve a gross total tumor removal in all cases. Nine patients (60%) exhibited a transient postoperative aggravation. Two patients (13%) presented permanent phasic aggravation. One patient died 16 days after surgery from pulmonary embolism. Five patients died for tumor progression, with a mean survival time of 16.4 months and a median high-quality survival period of 14.2 months. With a mean follow-up of 9.9 months (range, 18-6 months), the 9 survivors are recurrence-free and reveal no significant change in linguistic abilities. This technique is well tolerated and consents to maximize the extent of surgical removal while minimizing the risks of permanent postoperative deficits. This results in an improvement of survival and quality of life.

Adult↗

PubMed2001

Evidence of peripheral auditory activity modulation by the auditory cortex in humans.

At the auditory periphery, the medial olivocochlear system is assumed to be involved in complex sound processing and may be influenced by feedback from higher auditory nuclei. Indeed, the descending auditory pathway includes fibers coming from the auditory cortex that are anatomically well positioned to influence the superior olivary complex, and thus the medial efferent system. The aim of the present study was to verify the hypothesis of an implied influence of the auditory cortex on the peripheral auditory system. In three rare cases of patients presenting with intractable temporal lobe epilepsy, Heschl's gyrus (i.e. the temporal superior gyrus) was surgically removed in the right hemisphere in two patients and in the left hemisphere in a third patient, in order to minimize epilepsy attacks, as preoperative stereoencephalography had shown the epileptic focus or tumor to be situated in those locations. In all three cases, several weeks after the operation the medial olivocochlear system was clearly less functional on both sides, but especially on the side contralateral to the resection. In healthy controls, no such pattern was obtained. In four other epileptic patients, who were operated unilaterally at the anterior temporal pole, amygdala and hippocampus with the temporal gyrus partially spared, efferent suppression grew stronger in the ear ipsilateral to surgery. These results revealed that, in humans, the primary and secondary auditory cortex play a role in modulating auditory periphery activity through direct or indirect efferent fibers. In accordance with previous findings, this descending influence may improve the auditory afferent message by adapting the hearing function according to cortical analysis of the ascending input.

Adult↗

PubMed2001

Neurophysiological monitoring for epilepsy surgery: the Talairach SEEG method. StereoElectroEncephaloGraphy. Indications, results, complications and therapeutic applications in a series of 100 consecutive cases.

OBJECT OF THE STUDY: In some candidates for epilepsy surgery in whom the decision to operate is difficult to make, invasive presurgical investigations, namely depth electrode recordings, may be needed. The SEEG (StereoElectroEncephaloGraphy) method consists of stereotactic orthogonal implantation of depth electrodes (5 to 15, 11 on average). The object of this study is to clarify the indications for SEEG, to expose its complications, and to display its usefulness in terms of surgical strategy and results. PATIENTS AND METHODS: 100 patients, suffering from drug-resistant epilepsy and selected as candidates for surgical resection, underwent SEEG between 1996 and 2000. A total of 1,118 electrodes were implanted. For each single case, the sites of implantation of the electrodes were chosen in order to determine either the side of the onset of seizures, or the uni- or multilobar feature of them, or a possible operculo-insular propagation from a temporal onset, and also, using direct electrode stimulation, the proximity of speech or motor area. RESULTS: Complications occurred in 5 patients (2 superficial infections, 2 breakages of electrodes, and 1 intracerebral hematoma responsible for death). SEEG was helpful in most (84%) of the 100 patients to confirm or annul surgical indication, and to adjust the extent of the resection. In some cases (14%), SEEG allowed to propose a resection that might have been disputable based solely on noninvasive investigation data. For frontal epilepsy, SEEG was crucial in all cases to delineate the extent of resection. CONCLUSION: SEEG proved to be a relatively safe and a very useful method in 'difficult' candidates for epilepsy surgery. In addition, in some cases the implanted electrodes can be used to perform therapeutic RF thermocoagulation of epileptic foci or networks.

Adult↗

PubMed2001

[Perioperative cortical stimulation of language fields under local anesthesia in preparation to excision of tumors of the dominant hemisphere].

OBJECTIVES: The aim of this study is to demonstrate the accuracy of direct cortical stimulation of language areas preparatory to the removal of infiltrating tumors of dominant hemisphere. MATERIAL AND METHODS: From June 1998 to March 2000 we included in our study 15 patients, aged from 30 to 75 years, harboring gliomas (14 high grades and 1 low grade) close to language-specific cortex. All patients had slight inaugural phasic troubles. They underwent craniotomy under local anesthesia for cortical stimulation language mapping, in conjunction with electrocorticography to identify the after-discharge threshold. Stimulation mapping covered the entire macroscopically tumor involved area, extending up to 3 cm away from the margins of the lesion, without searching to identify systematically the language areas. Therefore, the lesion was removed as completely as possible, respecting a security margin of at least 1 cm from the recognized language sites. RESULTS: We identified from 1 to 6 language sites for 14 of our patients, in different locations. A radical removal was achieved for all high grade gliomas, while the low grade was only partially removed. A patient died on the 16th postoperative day from pulmonary embolism; 2 patients deteriorated from peri- or immediate postoperative complications; 9 showed a transient neurological worsening that receded by the 2nd postoperative month, while 3 did not present any postoperative aggravation. At a follow-up of 1 month to 2 years (mean 8 months), 6 patients died and the 9 survivors maintain a good life quality. CONCLUSIONS: Cortical stimulation for language mapping is an accurate technique that allows the surgical morbidity of lesions in proximity to language areas to decrease and become comparable to the surgical morbidity for lesions in non eloquent areas.

Adult↗

PubMed2000

Towards an optimal reference region in single-photon emission tomography difference images in epilepsy.

There is marked variability in the cerebral blood flow (CBF) between the ictal and interictal state in epilepsy, and it would therefore be desirable to increase the reliability of ictal/interictal single-photon emission tomography (SPET) difference images. We aimed to improve the step of quantitative normalization of images by finding the best possible reference region. In 16 patients (11 with lateralization of the epileptogenic focus, five with bilateral foci) both ictal and inter-ictal SPET scans were performed after injection of technetium-99m labelled tracer. Then, each region among a selected set (brain+cerebellum, brain, cerebellum, hemispheres, and for patients with an expected lateralization, cortical lobe containing the focus and symmetrical contralateral lobe) was investigated by comparison of the regional ictal/inter-ictal variance in counts. Among patients with a suspected lateralized focus, the distribution of CBF in the contralateral cortical lobe appeared to vary less between ictal and inter-ictal states than in other investigated areas. As a consequence, this latter region constitutes the best choice as a reference region. For patients with bilateral foci, the cerebellum appears to be a good compromise even though it presents with significant CBF changes.

Brain↗

PubMed2000

Functional mapping of the insular cortex: clinical implication in temporal lobe epilepsy.

PURPOSE: We report the results of 75 intracortical electrical stimulations of the insular cortex performed in 14 patients during stereo-electroencephalography (SEEG) investigation of drug-resistant partial epilepsy. The insular cortex was investigated on electroclinical arguments suggesting the possibility of a perisylvian spread or a rapid multilobar diffusion of the discharges during video EEG. METHODS: In these 14 patients, 27 stereotactically implanted transopercular electrodes reached the insular cortex (11 the right insula, 16 the left insula). Square pulses of current were applied between the two deepest adjacent contacts of each transopercular electrode using low (1 Hz) or high-frequency (50 Hz) stimulation. Only symptoms evoked in the absence of afterdischarges were analyzed. RESULTS: Clinical responses were evoked in 10 of the 14 patients (in 20 of the 27 insular sites) and showed a clear topographic specificity inside the insular cortex. Viscerosensitive and visceromotor responses, similar to those evoked by temporomesial stimulation, were evoked by anterior insular stimulation and somesthetic sensation, similar to those evoked by opercular cortex stimulation, by posterior insular stimulation. CONCLUSIONS: The topographic organization of the induced responses within the insular cortex suggest that two different cortical networks, a visceral network extending to the temporomesial structures and a somesthetic network reaching the opercular cortex, are disturbed with stimulation of the anterior or the posterior insula, respectively. Thus ictal symptoms associated with the spread of the epileptic discharges to the insular cortex might be difficult to distinguish from those usually reported during temporomesial or opercular discharges.

Adult↗

PubMed2000

Anatomy of optic nerve radiations as assessed by static perimetry and MRI after tailored temporal lobectomy.

AIMS: To determine the course of optic nerve radiations in the temporal lobe, especially their retinotopic organisation and the anterior limit of the Meyer's loop. METHODS: 18 adult patients who had undergone a tailored temporal lobectomy for epilepsy were included in this study between 1994 and 1998. The rostrocaudal extent of the lateral temporal lobe resection assessed intraoperatively by the surgeon and by postoperative MRI was compared with the postoperative visual fields determined by automated static perimetry (ASP). RESULTS: 15 patients (83%) presented a postoperative visual field deficit (VFD) confined to the superior homonymous field contralateral to the side of the resection. All degrees from a minimal upper field loss to a complete quadrantanopia were observed. The VFDs were somewhat stereotyped, predominating along the vertical meridian. The smallest anteroposterior resection resulting in a VFD was limited to 20 mm from the tip of the temporal lobe. A relation was observed between the extent of the lateral resection in front of the second and third convolutions and the occurrence and extent of postoperative VFDs. No patient reported persisting subjective visual impairment. CONCLUSION: The high frequency of postoperative VFDs appears to be due to the greater sensitivity of ASP. The characteristics of the stereotyped VFDs allow new conclusions about the course and retinotopy of optic nerve radiations. The anterior limit of Meyer's loop is likely to be located more rostrally than previously believed.

Adult↗