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M Guénot

Publications and source records attributed to M Guénot.

15 recordsLinked to original sources
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↗
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

[Indications and risk of neurosurgical techniques in the adult presenting with drug-resistant partial epilepsy (radiosurgery included)].

To be considered for resective (curative) surgery, most seizures have to been proved to arise exclusively from one area of the brain that is functionally silent. The drug-resistance must be certain, and the patient must be strongly motivated to undergo surgery. Temporal lobectomy for drug-resistant temporo-mesial epilepsy is now scientifically validated by a randomized controlled trial. Hemispherotomy, which consists in complete disconnection of one hemisphere, is a curative technique, which may be considered where there is a pre-existing hemiplegia associated with a structural abnormality of the contralateral hemisphere. Therefore, it is rarely performed in adult patients. Stereotactic radiosurgery is also a curative technique, which shares most of its indications with those of temporo-mesial resections. Callosotomy is a palliative technique, which consists in disconnecting the hemispheres, one from the other. It may be considered in individuals having frequent atonic seizures (drop attacks). Multiple subpial transection involves transection of transverse fibers, leaving longitudinal fibers intact. It may be performed if the epileptogenic focus is located in an eloquent brain area. The complication rate of resective surgery is low. Controlateral motor impairement is the main permanent complication related to cortical resection. It is a rare occurrence (1 to 2 percent of cases) due to peroperative lesions of the sylvian vasculature, or of the anterior choroidal artery, or even of the motor area. Postoperative hematomas, infections, or hydrocephalus may also occur in 2 to 6 percent of cases, depending on the authors. Some postoperative neuropsychological complications are reported in the literature, especially after surgery on the dominant side. Hydrocephalus and infection are the most frequent complications occurring after hemispherotomy (10 percent of cases). Dysconnexion syndrome is a rare complication, which can be seen after total callosotomy. It is unusual for the effects of disconnection after anterior callosotomy to represent significant handicap. Permanent postoperative worsening of a pre-existing neurological impairement, as well as hematomas, are seen in less than 10 percent of the cases after multiple subpial transection. In conclusion, surgery is an important therapeutic option, which has to be considered as soon as the epileptic disease appears to be drug-resistant, particularly in case of temporo-mesial epilepsy.

Adult↗
PubMed2004

[Surgical treatment for epilepsy in children: indications and complications].

The main etiologies of epilepsy are somewhat different in the pediatric population, from those found in the adults. This explains why temporal resections are less frequently performed in children than in adults. To be considered for resective (curative) surgery, most seizures have to been proved to arise exclusively from one area of the brain that is functionally silent. The drug-resistance must be certain, and the patient, or his family, must be strongly motivated to undergo surgery. Hemispherotomy, which consists in complete disconnection of one hemisphere, is a curative technique, which may be considered where there is a pre-existing hemiplegia associated with a structural abnormality of the contralateral hemisphere. Callosotomy is a palliative technique, which consists in disconnecting the hemispheres, one from the other. It may be considered in individuals having frequent atonic seizures (drop attacks). Multiple subpial transection involves transection of transverse fibers, leaving longitudinal fibers intact. It may be performed if the epileptogenic focus is located in an eloquent brain area. It may also be performed in case of Landau-Kleffner syndrome. The complication rate of resective surgery is low. Contralateral motor impairement is the main permanent complication related to cortical resection. It is a rare occurrence (1 to 2 percent of cases) due to peroperative lesions of the sylvian vasculature, or of the anterior choroidal artery, or even of the motor area. Postoperative hematomas, infections, or hydrocephalus may also occur in 2 to 6 percent of cases, depending on the authors. Some postoperative neuropsychological complications are reported in the literature, especially after surgery on the dominant side. Hydrocephalus and infection are the most frequent complications occurring after hemispherotomy (10 percent of cases). Dysconnexion syndrome is a rare complication, which can be seen after total callosotomy. It is unusual for the effects of disconnection after anterior callosotomy to represent significant handicap. Permanent postoperative worsening of a pre-existing neurological impairement is seen in less than 10 percent of the cases after multiple subpial transection. In conclusion, surgery has to be considered without unnecessary delay in the children presenting with drug-resistant epilepsy, before any cognitive or psychosocial deterioration, due to the epileptic disease, occurs.

Anticonvulsants↗
PubMed2004

[Surgical treatment of epilepsy: outcome of various surgical procedures in adults and children].

Surgical treatment of drug-resistant epilepsy is being performed in a growing number of adults and children. The objective of this report is to review and evaluate the published literature related to the outcome of epilepsy surgery. Surgical procedures were classified as "curative", which included temporal and extratemporal resections, as well as hemispherotomy and stereotactic radiosurgery, and as "palliative", which mainly included callosotomy and multiple subpial transections. Data obtained from the literature suggest that after temporal lobe surgery, 68 percent of the adult patients, on average, are seizure-free. This result may vary, according to the authors, from 50 to 93 percent. One randomized controlled study concludes that 58 percent of patients treated surgically become seizure-free, compared to only 8 percent in the group of patients who do not receive surgery. This suggests that temporal lobe surgery is an efficient treatment of drug-refractory temporal lobe surgery. Seizure outcome is similar in the pediatric population. Studies of frontal lobe surgery report that an average of 60 percent of patients are seizure-free after surgery, in adults as well as in children. These results may vary considerably, depending on how the seizure outcome is defined. Too few studies are available to allow for an evaluation of parietal or occipital lobe surgery. Hemispherotomy is mostly performed in the pediatric population. Studies of this procedure report that 60 percent of patients become seizure free after surgery, whereas 80 percent are improved in terms of seizure outcome and in terms of behavior. Stereotactic radiosurgery may be performed in case of hypothalamic hamartoma, and in some cases of temporal lobe epilepsy. In this later case, the reported results are similar to those obtained with temporal resections. Seizure outcome after corpus callosotomy is difficult to summarize, because of the many variations, according to the authors, of the definition of a good or poor seizure outcome. However, it can be stated that 65 to 85 percent of patients achieve a significant reduction in overall seizure frequency. The best reduction in seizure frequency is achieved in patients with atonic. Reported percentages of patients who benefit from multiple subpial transection, varies between 50 and 70 percent. In conclusion, our report shows that temporal resection is an efficient and scientifically validated treatment of drug-resistant temporal lobe epilepsy. Extra-temporal resections, hemispherotomy, and palliative surgery often allow cure of epilepsy, or a decrease of seizure frequency, however, prospective studies of these surgical procedures are needed.

Adult↗
PubMed2001

Stereotactic recordings of median nerve somatosensory-evoked potentials in the human pre-supplementary motor area.

Median nerve somatosensory-evoked potentials (SEPs) have been recorded using intracortical electrodes stereotactically implanted in the frontal lobe of eight epileptic patients in order to assess the waveforms, latencies and surface-to-depth distributions of somatosensory responses generated in the anterior subdivision of supplementary motor areas (SMAs), the so-called pre-SMA. Intracortical responses were analysed in two latency ranges: 0--50 ms and 50--150 ms after stimulus. In all patients, we recorded in the first 50 ms after stimulus two positive P14 and P20 potentials followed by a N30 negativity. In the hemisphere contralateral to stimulation, the P20--N30 potentials showed a clear amplitude decrease from the outer to the inner aspect of the frontal lobe with minimal amplitudes in the pre-SMA. In the hemisphere ipsilateral to stimulus, P20 and N30 amplitudes were decreasing from mesial to lateral frontal cortex. In the 50--150 ms latency range, contacts implanted in the pre-SMA recorded a negative potential in the 60--70 ms latency range which, in five patients, was followed by a positive response peaking 80--110 ms after stimulus. These potentials were not picked up by more superficial contacts. We conclude that no early SEP is generated in pre-SMA in the first 50 ms after stimulation, while some potentials peaking in the 60--100 ms after stimulus are likely to originate from this cortical area. The latency of the pre-SMA responses recorded in our patients supports the hypothesis that the pre-SMA does not receive short-latency somatosensory inputs via direct thalamocortical projections. More probably the pre-SMA receives somatosensory inputs mediated by a polysynaptic transcortical transmission through functionally secondary motor and somatosensory areas.

Adolescent↗
PubMed2001

[Chronic subdural hematoma: historical studies].

The first description of a chronic subdural hematoma was made in 1658 by J.J. Wepfer, followed in 1761 by Morgagni. A possible case was described by Honoré de Balzac in 1840 including its traumatic origin and surgical treatment. Virchow, in 1857, denied a traumatic origin, and gave the name of "pachymeningitis hemorrhagica interna" to this pathology which he explained by inflammatory processes. The traumatic etiology of chronic subdural hematoma was recognized in the XXth century, especially by Trotter in 1914. Pathophysiology was considered later on in the XXth century.

Europe↗
PubMed2001

[Chronic subdural hematoma: diagnostic imaging studies].

CT-scan is able to provide the diagnosis of chronic subdural hematoma in more than 90% of the cases. It usually shows a peri-cerebral fluid collection along the convexity, with a convex outer border, and an irregular concave inner border. The density of the collection depends on the age of the hematoma. The main difficulties, in term of diagnosis, result from bilateral isodense chronic subdural hematoma, and differential diagnosis between hematoma, hygroma, and empyema. Some rare localisations can sometimes be seen (posterior fossa, skull base...). A double density with a sedimentation level, or heterogeneity of the hematoma, can sometimes be seen too. Chronic subdural hematoma is demonstrated by MRI in almost 100% of the cases. The intensity of the collection, in T1 and T2 sequences, depends on the age of the hematoma.

Diagnosis, Differential↗
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

The role of the insular cortex in temporal lobe epilepsy.

The role of the insular cortex in the genesis of temporal lobe epileptic (TLE) seizures has been investigated in 21 patients with drug-refractory TLE using chronic depth stereotactic recordings of the insular cortex activity and video recordings of ictal symptoms during 81 spontaneous electroclinical seizures. All of the recorded seizures were found to invade the insula, most often after a relay in the ipsilateral hippocampus (19/21 patients). However, 2 patients had seizures that originated in the insular cortex itself. Ictal symptoms associated with the insular discharges were similar to those usually attributed to mesial temporal lobe seizures, so that scalp video-electroencephalographic monitoring does not permit making any difference between ictal symptoms of temporo-mesial and insular discharges. A favorable outcome was obtained after a temporal cortectomy sparing the insular cortex in 15 of 17 operated patients. Seizures propagating to the insular cortex were found to be fully controlled by surgery, whereas those originating in the insular cortex persisted after temporal cortectomy. The fact that seizures originating in the insular cortex are not influenced by temporal lobectomy is likely to explain some of the failures of this surgical procedure in TLE.

Adolescent↗
PubMed1999

Intracortical recordings of early pain-related CO2-laser evoked potentials in the human second somatosensory (SII) area.

We studied responses of the parieto-frontal opercular cortex to CO2-laser stimulation of A delta fiber endings, as recorded by intra-cortical electrodes during stereotactic-EEG (SEEG) presurgical assessment of patients with drug-resistant temporal lobe epilepsy. After CO2-laser stimulation of the skin at the dorsum of the hand, we consistently recorded in the upper bank of the sylvian fissure contralateral to stimulation, a negative response at a latency of 135 +/- 18 ms (N140), followed by a positivity peaking around 171 +/- 22 ms (P170). The stereotactic coordinates in the Talairach's atlas of the electrode contacts recording these early responses covered the pre- and post-rolandic part of the upper bank of the sylvian fissure (-27 < y < +12 mm; 31 < x < 57 mm; 4 < z < 23 mm), corresponding to the accepted localization of the SII area in man, possibly including the upper part of the insular cortex. The spatial distribution of these early contralateral responses in the SII-insular cortex fits wit that of the modeled sources of scalp CO2-laser evoked potentials (LEPs) and with PET data from pain activation studies. Moreover, this study showed the likely existence of dipolar sources radial to the scalp surface in SII, which are overlooked in magnetic recordings. Early responses also occurred in the SII area ipsilateral to stimulation peaking 15 ms later than in contralateral SII, suggesting a callosal transmission of nociceptive inputs between the two SII areas. Other pain responsive areas such as the anterior cingulate gyrus, the amygdala and the orbitofrontal cortex did not show early LEPs in the 200 ms post-stimulus. These findings suggest that activation of SII area contralateral to stimulation, possibly through direct thalamocortical projections, represents the first step in the cortical processing of peripheral A delta fiber pain inputs.

Adult↗
PubMed1998

A stereoelectroencephalographic (SEEG) study of light-induced mesiotemporal epileptic seizures.

PURPOSE: This study explored the mechanism of light-induced complex partial seizures by using ictal intracerebral recordings in a patient with refractory epilepsy of the right temporal lobe. METHODS: Presurgical evaluation of this patient was realized by means of video-EEG recordings, WADA test, magnetic resonance imaging (MRI), F18-deoxyglucose and C11-flumazenil positron emission tomography (PET) interictal neuroimaging data, and stereoelectroencephalographic (SEEG) ictal recordings. RESULTS: SEEG investigations demonstrated the right mesiotemporal origin of all the patient's seizures. This result was confirmed by a successful right temporal lobectomy. Moreover, SEEG recordings revealed a frequent interictal spiking activity in the right occipital visual cortex that was undetectable on scalp recordings. However, the occipital cortex was not involved at the onset of mesiotemporal ictal discharges and was not hyperresponsive to focal electrical stimulation. CONCLUSIONS: This study shows that, in spite of interictal occipital spiking, the photosensitivity of mesiotemporal seizures can be observed in both the absence of occipital cortex involvement during ictal discharges and demonstrable hyperexcitability of the occipital cortex to light or direct electrical stimulation.

Adult↗
PubMedDate not supplied

Polyglucosan bodies and temporal lobe epilepsy: an incidental finding or more?

This study reports on histological findings in the temporal lobe of a 36-year-old woman who underwent a right temporal lobectomy for pharmaco-resistant complex partial seizures. Since surgery, the patient has remained seizure-free. The patient had an established diagnosis of right temporal lobe epilepsy, based on video EEG recordings of seizures, MRI hippocampal atrophy, focal interictal hypometabolism on fluoro-desoxyglucose, hypofixation of Cl1-flumazenil in PET studies, and ictal intracerebral recordings. Biopsies were studied under light- and electron microscopy. Histology showed diffuse distribution of a large number of polyglucosan bodies (PBs) in the whole right temporal lobe white matter. PBs were mostly confined to the perivascular areas and in subpial zones rarely and were observed in the most superficial cortical layers. There was some neuronal loss, especially in opercular zone T , but no other histological lesion was found. Ultrastructurally, PBs were made of filamentous and amorphous material, and were found both in intra-astrocytic processes and in axons. The presence of numerous PBs in the temporal lobe of patients with refractory temporal lobe epilepsy has been reported in 3 patients in the literature. It raises the questions whether this histological abnormality could be related to the epileptogenic process as a cause or as a consequence.

Adult↗
PubMedDate not supplied

[MRI in infectious and spontaneous tumoral epidural hemorrhagic pathology].

Several studies have served to underline the interest of MRI in the diagnosis and assessment of epidural abscess and malignant extradural spinal tumors. In our work, one of the quantitatively greatest published to this day, 64 patients presenting epidural pathology were evaluated by means of MRI. All the explorations were brought about through weighted multiplaned sequences T1, T2 and gadolinium injection. The pathological spectrum encountered is comprised of: metastatic extradural spinal tumors (58%), primary extradural spinal tumors (7%), epidural localizations of hematological diseases (9%), epidural abscess (25%), and one case of epidural hematoma. Assessment was brought to bear upon behavior in relation to type of sequence, spread of disease, medullary effects, type of enhancement following gadolinium injection. Degree of correlation with clinical data and surgical findings was also appraised. As concerns tumourous epidural pathology, positive diagnosis due to a lesion hinges upon the T1 and T2 sequences. Gadolinium's contribution is restricted to analysis of perivertebral and vertebral spreading; it also facilitates recognition of the spinal cord in circumferential epiduritis. So much said, gadolinium appears to be essential in frequently less compressive forms of infectious epiduritis; it plays a pronounced role in both follow-up of their evolution and recognition of acute epidural hematoma.

Bacterial Infections↗