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Alim Louis Benabid

Publications and source records attributed to Alim Louis Benabid.

17 recordsLinked to original sources
PubMed2006

Correlation between the anatomical and functional human subthalamic nucleus.

This work addresses the spatial correlation between the anatomical and functional human subthalamic nucleus (STN). The anatomical STN (A-STN), derived from the Schaltenbrand-Wahren brain atlas, is histology based. The functional STN (F-STN) is probabilistic, constructed from neuroelectrophysiological and neuroimaging data of 184 Parkinson's disease patients. The A-STN and F-STN are placed in the same space and compared in terms of mutual relative overlapping of anatomy with function. The F-STN and A-STN correlate well for medium and high probabilities of the F-STN. For probability p >or= 0.3, >95% of F-STN is inside the A-STN, and for p >or= 0.5, the complete F-STN is inside the A-STN for each left and right STN. Therefore, the F-STN for p = 0.5 can potentially be used for identification of the STN in neuroimages.

Anatomy, Artistic↗
PubMed2006

A probabilistic functional atlas of the VIM nucleus constructed from pre-, intra- and postoperative electrophysiological and neuroimaging data acquired during the surgical treatment of Parkinson's disease patients.

We have previously introduced a concept of a probabilistic functional atlas (PFA) to overcome limitations of the current electronic stereotactic brain atlases: anatomical nature, spatial sparseness, inconsistency and lack of population information. The PFA for the STN has already been developed. This work addresses construction of the PFA for the ventrointermediate nucleus (PFA-VIM). The PFA-VIM is constructed from pre-, intra- and postoperative electrophysiological and neuroimaging data acquired during the surgical treatment of Parkinson's disease patients. The data contain the positions of the chronically implanted electrodes and their best contacts. For each patient, the intercommissural distance, height of the thalamus and width of the third ventricle were measured. An algorithm was developed to convert these data into the PFA-VIM, and to present them on axial, coronal and sagittal planes and in 3-D. The PFA-VIM gives a spatial distribution of the best contacts, and its probability is proportional to best contact concentration in a given location. The region with the highest probability corresponds to the best target. The PFA-VIM is calculated with 0.25-mm3 resolution from 107 best contacts in two situations: with and without lateral compensation against the width of the third ventricle. For the PFA-VIM compensated laterally, the anterior, lateral and dorsal coordinates of the mean value are (in mm) 6.24, 13.83, 1.68 for the left VIM and 6.54, -13.84, 2.10 for the right VIM. The coordinates of the mean value of the highest probability region along with the highest number of the best contacts (P) are: 6.25, 14.25, 1.75, P = 16, for the left VIM, and 6.0, -14.0, 1.00, P = 18, for the right VIM. The coordinate system origin is at the posterior commissure. For the PFA-VIM not compensated laterally, the coordinates of the mean value are 6.24, 13.99, 1.68 for the left VIM and 6.53, -14.13, 2.10 for the right VIM. The coordinates of the mean value of the highest probability region along with the highest number of the best contacts are 5.58, 13.67, 1.33, P = 14, for the left VIM, and 6.36, -14.03, 1.11, P = 17, for the right VIM. The PFA-VIM atlas overcomes several limitations of the current anatomical atlases and can improve targeting of thalamotomies and thalamic stimulations. It is dynamic and can easily be extended with new cases.

Algorithms↗
PubMed2005

The temporopolar cortex plays a pivotal role in temporal lobe seizures.

We investigated the role of the temporal pole (TP) in 48 consecutive patients with drug-refractory temporal lobe epilepsy (TLE). Chronic depth recordings of TP cortex activity were used in association with video recording of ictal symptoms during 48 spontaneous seizures. In 23 cases (48%, group 1) the TP was involved at the onset of the seizure, before or concurrently with the hippocampus. In the remaining 25 patients (52%, group 2) the TP was involved 16.4 +/- 13.8 s after the hippocampus. A past history of febrile seizures was found in both groups, with no statistical difference. Ictal symptoms did not differentiate TP seizures from seizures originating in the hippocampus but the first clinical sign occurred sooner in group 1 compared with group 2 (respectively 10.56 +/- 9 and 25.7 +/- 19 s, respectively, P = 0.005). Loss of awareness also occurred sooner in the case of TP seizures compared with mesiotemporal lobe (MTL) seizures (22.9 +/- 22.6 versus 42.2 +/- 18.6 s, P = 0.0002). MRI data analysis showed that hippocampal sclerosis was present in both groups of patients, although it was more frequent in patients with MTL onset. Anterior temporal white matter changes were found ipsilateral to the epileptogenic area and tended to be more frequent in patients with TP seizures. All the patients underwent tailored anterior temporal lobectomy that included the TP, the hippocampus, the parahippocampal gyrus and the anterior part of the lateral temporal cortex. A better postoperative outcome was achieved in group 1 compared with group 2 (Engel class 1, 95 and 72% respectively, P = 0.04). We conclude that the frequent TP involvement at the onset of seizures could be a supplementary explanation for some failures of selective amygdalohippocampectomy, which should be addressed preferentially to well-selected patients. Moreover, the involvement of the TP cortex at the onset of the seizures is a good predicting factor for postoperative seizure outcome.

Adolescent↗
PubMed2005

Deep-brain stimulation in Parkinson's disease: long-term efficacy and safety - What happened this year?

PURPOSE OF REVIEW: Deep-brain high-frequency stimulation of the thalamus was introduced in 1987 to treat tremor, and was applied in 1993 to the subthalamic nucleus to treat advanced Parkinson's disease. High-frequency stimulation of the subthalamic nucleus has become the surgical therapy of choice. This review concentrates on recent data on long-term results and side-effects, after 12 years of practice using this technique. RECENT FINDINGS: A literature search produced 260 papers from February 2004 to March 2005. The stable efficacy of high-frequency stimulation of the subthalamic nucleus on Parkinson's disease motor symptoms is confirmed. Evidence for a neuroprotective effect is still lacking. There are transient neuropsychological disturbances, but no cognitive impairment over time. Complications are rare and mild, mortality is extremely low and hardware complications are highly variable. SUMMARY: The safety and innocuity of the method legitimizes earlier operations, before impairment of the quality of life. Depression and suicide are related to pre-existing co-morbidities and multifactorial causes that could become contraindications. Neuropsychological effects should be documented, to determine whether they are caused by an alteration of high-frequency stimulation of the subthalamic nucleus, or inappropriate electrode placement. There is an urgent need for the organization of research and reports, and no need to report small series replicating well-established conclusions. Clinical reports should concentrate on unobserved effects in relation to causative parameters, based on the precise location of electrodes, and on clinical reports comparable between teams and on methods to optimize and facilitate the tuning of parameters and postoperative evaluations in order to make this treatment easier to provide for the neurologist.

Deep Brain Stimulation↗
PubMed2004

A probabilistic functional atlas of the human subthalamic nucleus.

This paper introduces a method for generation and validation of a probabilistic functional brain atlas of subcortical structures from electrophysiological and neuroimaging data. The method contains three major steps: (1) acquisition of pre, intra, and postoperative multimodal data; (2) selection of an accurate data set for atlas generation; and (3) generation of the atlas from the selected data set. The method is applied to construct the probabilistic functional atlas of the human subthalamic nucleus (STN). The STN atlas has been built from data collected during surgical treatment of 184 patients with Parkinson's disease. It is based on preoperative X-ray ventriculography imaging, intraoperative electrophysiological measurements and X-ray imaging, and postoperative neurological assessment. The atlas features a high resolution of 0.25 mm(3) and a high accuracy of 0.25 mm. It is dynamic and can be rapidly recalculated for arbitrary resolution and extended by adding new patient data. The atlas can easily be reformatted and warped to match patient-specific data. Its applications include planning of subthalamic stimulations and neuroscience research to study functional properties of the STN. The presented method is general and can be applied for constructing human and animal probabilistic brain atlases.

Anatomy, Artistic↗
PubMed2003

An algorithm for rapid calculation of a probabilistic functional atlas of subcortical structures from electrophysiological data collected during functional neurosurgery procedures.

The paper introduces an optimal algorithm for rapid calculation of a probabilistic functional atlas (PFA) of subcortical structures from data collected during functional neurosurgery procedures. The PFA is calculated based on combined intraoperative electrophysiology, pre- and intraoperative neuroimaging, and postoperative neurological verification. The algorithm converts the coordinates of the neurologically most effective contacts into probabilistic functional maps taking into account the geometry of a stimulating electrode. The PFA calculation comprises the reconstruction of the contact coordinates from two orthogonal projections, normalizing (warping) the contacts modeled as cylinders, voxelizing the contact models, calculating the atlas, and computing probability. In addition, an analytical representation of the PFA is formulated based on Gaussian modeling. The initial PFA has been calculated from the data collected during the treatment of 274 Parkinson's disease patients, most of them operated bilaterally (487 operated hemispheres). It contains the most popular stereotactic targets, the subthalamic nucleus, globus pallidus internus, and ventral intermedius nucleus. The key application of the algorithm is targeting in stereotactic and functional neurosurgery, and it also can be employed in human and animal brain research.

Algorithms↗
PubMed2003

Deep brain stimulation for Parkinson's disease.

Deep brain stimulation at high frequency was first used in 1997 to replace thalamotomy in treating the characteristic tremor of Parkinson's disease, and has subsequently been applied to the pallidum and the subthalamic nucleus. The subthalamic nucleus is a key node in the functional control of motor activity in the basal ganglia. Its inhibition suppresses symptoms in animal models of Parkinson's disease, and high frequency chronic stimulation does the same in human patients. Acute and long-term results after deep brain stimulation show a dramatic and stable improvement of a patient's clinical condition, which mimics the effects of levodopa treatment. The mechanism of action may involve a functional disruption of the abnormal neural messages associated with the disease. Long-term changes, neural plasticity and neural protection might be induced in the network. Similar effects of stimulation and lesioning have led to the extension of this technique for other targets and diseases.

Electric Stimulation Therapy↗
PubMed2003

Restricted frontomesial epileptogenic focus generating dyskinetic behavior and laughter.

PURPOSE: Substantial data are missing about the anatomic location of frontal regions supporting gelastic seizures. METHODS: We report the results of stereo-electro-encephalographic recordings performed over several distinct functional premotor and executive fields in a patient whose seizures were characterized by dyskinetic behavior and ictal laughter, in the absence of cerebral MRI abnormalities. RESULTS: The epileptogenic zone was circumscribed in the anterior and ventral part of the supplementary motor area and the underlying dorsal cingulate cortex. There were no or little spreading to cortical neighboring areas. The patient is seizure-free (follow-up of 27 months) after a stereotactic electric radiofrequency lesion of the epileptogenic focus. CONCLUSION: The present data suggest that pericingulate premotor areas are involved in the triggering of the motor component of laughter. In this case, the coexistence of paroxysmal dyskinesias during laughter might reflect the involvement of specific compartment(s) of the basal ganglia.

Adult↗
PubMed2003

MRI morphological and volumetric study of the cingulate gyrus and its relevance in partial epileptic patients.

The cingulate gyrus (CG) is often involved during partial epileptic seizures. The purpose of the study was to analyse the CG morphology and to measure the CG volume in epileptic patients, in order to detect subtle MRI abnormalities such as atrophy, which could be indicative of its implication in the epileptogenic area. The population consisted of 20 epileptic patients (31.2 +/- 9.4 years) and 20 normal volunteers (31.8 +/- 7.7 years). The epileptic patients underwent intracerebral recordings, and were sub-divided into five patients presenting with seizures involving the CG (CG 1), seven patients in whom the CG was only secondarily involved (CG 2) and eight patients in whom the CG was not invoved at all (CG 3). All subjects were investigated by MRI (1.5 tesla Gyroscan Philips): axial T1w 3D Gradient Echo acquisitions, thickness 1.5 mm, reconstructions in all planes. At first, we described the sulcal limits of the CG, trying to define a "normalised CG". In a second step, we segmented the CG intrasulcal grey matter using the "Surgiscope Scopeplan" (Elekta). We compared (Mann and Whitney U test [alpha=0.05]), the CG volumes of CG 1 to CG 2 + 3, and the volume of CG 1 and of CG 1 + 2 + 3 to that of normal volunteers. There was no significant difference between CG 1 and CG 2 + 3 (P= 0.89), between CG 1 and normal volunteers (P= 0.75) or between CG1 + 2 + 3 and normal volunteers (P = 0.83). The volumetric analysis showed no atrophy of the CG in epileptic patients and did not distinguish the group in whom seizures involved the CG, from the other groups.

Adult↗
PubMed2003

[Therapeutic and physiopathological contribution of electric stimulation of deep brain structures in Parkinson's disease].

Ablative functional neurosurgery constituted during the first half of the 20th century the main treatment of advanced forms of Parkinson's disease. The surgical procedure was spectacularly efficient on tremor, but sometimes complications were not totally regressive and even more severe when surgery was bilateral, this leading to neurocognitive deficits or to speech problems. This, associated to the efficiency of levodopa, was at the origin of the almost total disappearance of this type of surgery during the '60s until the eighties. The rebirth of functional neurosurgery, necessitated by the appearance of dyskinesias, was possible in most part because of the development of techniques with a lower morbidity, such as high frequency stimulation (HFS). This was initially applied to the thalamic ventral intermedius nucleus VIM, and the low morbidity of the method has been demonstrated by the possibility to operate a large number of patients bilaterally without complication. The demonstration that the pallidal target, which had been abandoned during the '50s because of its low efficiency on the triad of symptoms of Parkinson's disease, was selectively efficient on dyskinesias, led naturally to apply HFS to this target. In 1990, the demonstration in the field of fundamental research of the role of the subthalamic nucleus as a key element of regulation of movement, suggested to register this nucleus into the list of targets, despite the risk of hemiballism that this structure presents when it is lesioned by haemorrhage, because of the good tolerance of HFS as a surgical method. This target quickly showed its remarkable efficiency on all symptoms of Parkinson's disease. Because of the reduction of the doses of dopaminergic treatments which were allowed, this target had also the capacity to reduce, indirectly, the intensity of dyskinesias. If the efficiency of the method is nowadays demonstrated as well as the stability on the long term of its results, the mechanism is still mostly not understood. Moreover the physiopathogenic hypothesis suggests the possibility of a neuroprotective effect of the stimulation, which still needs to be clearly established at the experimental level as well as at the level of clinical applications.

Animals↗
PubMed2003

From hypothalamic hamartoma to cortex: what can be learnt from depth recordings and stimulation?

Patients having a hypothalamic hamartoma (HH) frequently present gelastic or dacrystic seizures, and they often later experience multiple additional seizure types which lead to a severe epileptic encephalopathy. There is now increasing evidence that the HH itself plays a crucial role in this syndrome, but the relationships between the lesion and the different types of seizures remain a questionable issue. Stereotactic intracerebral EEG recordings were performed in 5 patients suffering from a medically intractable epilepsy associated with a HH. The hamartoma was investigated in all cases, and various cortical areas were also evaluated in 4 of the 5 patients. The epileptic discharges arose and remained confined within the hamartoma in 3 of the 4 patients in whom laughing and crying episodes were recorded. In addition, interictal spikes were recorded from the hamartoma in 4 of the 5 patients, whereas the stimulation of the HH could reproduce gelastic or dacrystic episodes in 3. The three patients in whom other types of seizure were recorded showed that the latter were associated with cortical ictal discharges not affecting the HH. Ictal onset appeared either bifrontal, right fronto-central and lateral temporal, or bifrontal with a right side predominance. The cingulate gyrus was involved in all these 3 cases, and the lateralization of the ictal discharges was always ipsilateral to the predominating side of the hamartoma. Interestingly, these seizure types were sometimes immediately preceded by the laughing or crying attacks, as if ictal discharges within the hamartoma triggered those which seemed to originate in the cortex. Therefore, if these findings confirm the intrinsic epileptogenicity of HH, they also demonstrate that epileptic seizures associated with HH can exhibit different types of electroclinical patterns. We propose a speculative pathophysiology in which the mamillo-thalamo-cingulate tract would serve as a relay of HH discharges towards the cortex, the excitability of which would then progressively increase, first leading to cortical interictal epileptiform abnormalities and then to seizures of cortical origin. Whether this proposal of secondary epileptogenesis is valid or not remains a major issue, since it could provide arguments on the moment to discuss surgery.

Adolescent↗
PubMed2002

Superior colliculus firing changes after lesion or electrical stimulation of the subthalamic nucleus in the rat.

Recent data have suggested a critical role for the basal ganglia in the remote control of epileptic seizures. In particular, it has been shown that inhibition of either substantia nigra pars reticulata or subthalamic nucleus as well as activation of the superior colliculus suppresses generalized seizures in several animal models. It was previously shown that high frequency stimulation of the subthalamic nucleus, thought to act as functional inhibition, stopped ongoing non-convulsive generalized seizures in rats. In order to determine whether high frequency stimulation of the subthalamic nucleus involved an activation of superior colliculus neurons, we examined the effects of subthalamic nucleus manipulation, by either high frequency stimulation or chemical lesion, on the spontaneous electrical activity of superior colliculus neurons. Acute high frequency stimulation of the subthalamic nucleus (frequency 130 Hz) induced an immediate increase of unitary activity in 70% of responding cells, mainly located within the deep layers, whereas a reduction was observed in the remaining 30%. The latter responses are dependent on the intensity and frequency of the stimulation. Unilateral excitotoxic lesion of the subthalamic nucleus induced a delayed and transient decrease of superior colliculus activity. Our data suggest that high frequency stimulation of the subthalamic nucleus suppresses generalised epileptic seizures through superior colliculus activation.

Action Potentials↗
PubMed2002

Imaging of subthalamic nucleus and ventralis intermedius of the thalamus.

The techniques of targeting the subthalamic nucleus (STN) and the ventralis intermedius nucleus (Vim) are similar, only the coordinates are different. Targeting ideally consists of gathering all data about a target and positioning the electrode correctly within that target. The electrode should be positioned within a statistical range of coordinates, where the neuronal firing fits a given pattern and responds to external stimuli, particularly to proprioceptive inputs, in a somatotopically organized manner. Moreover, final placement should provide the best clinical improvement of symptoms under the stimulation parameters expected to be used in the long term. This latter criterion is by far the most important, because intraoperative findings indicate the functional benefit for the patient, which is the ultimate purpose of this surgery. A variety of radiological modalities are available to provide data for electrode placement, but each type has its drawbacks. Ventriculography, although safe when performed accordingly to strict technical procedure, is the most precise method but provides more indirect targeting and is more invasive than magnetic resonance imaging (MRI). MRI is the best method for visualizing the STN and, to some extent, for discerning the Vim, but it is plagued with unpredictable and nonreproducible deformations that induce a systematic distortion. These shortcomings no doubt will be corrected in the near future, and the technologies will better assist us in the proper placement of electrodes, which will provide the patient with the highest possible benefit.

Cerebral Ventriculography↗
PubMed2002

Response to levodopa in parkinsonian patients with bilateral subthalamic nucleus stimulation.

The response to levodopa changes over time in Parkinson's disease, probably due to alterations in the dopaminergic system, progression of the disease and pulsatile oral intake of the drug. Bilateral high-frequency stimulation of the subthalamic nucleus (STN) allows a large reduction or the complete cessation of levodopa intake in patients with advanced Parkinson's disease. We studied variation in the motor short-duration response (SDR) during a levodopa challenge in bilaterally STN-stimulated patients. Twenty-eight consecutive patients with a mean duration of Parkinson's disease of 16.6 +/- 6.0 years at the time of surgery were enrolled. Fourteen patients were evaluated both before STN stimulation and 3 months after surgery (group 1) whereas the other 14 patients were assessed before implantation and after a mean of 3 years of STN stimulation (group 2). After drug withdrawal for one night, the hand-tapping test (TT) was carried out every 15 min, together with evaluation of dyskinesias using a modified Goetz scale. The Unified Parkinson's Disease Rating Scale (UPDRS) motor score was assessed every 30 min. In operated patients, STN stimulation was stopped 15 min before starting the clinical evaluations. A suprathreshold oral levodopa dose was given after one motor evaluation and two TTs. The clinical evaluation was carried out until the TT score returned to the baseline. In group 1, six patients continued without levodopa after surgery and the other eight received a daily mean dose of 337 mg; in group 2, seven patients continued without levodopa and the other seven received a daily mean dose of 386 mg. The main change in the levodopa SDR was a significant reduction in levodopa-induced dyskinesias in both groups. In those patients of group 1 who did not receive levodopa after surgery, the motor UPDRS magnitude decreased and the 'on' UPDRS motor score worsened. In group 2, the results were similar, but in the patients who continued to receive levodopa after surgery the TT magnitude increased. On the whole, chronic bilateral STN stimulation tended to decrease the magnitude of the levodopa SDR without changing the duration and latency of the response. These results suggest that continuous STN stimulation induces long-term plastic changes of the dopaminergic system, with slow and partial desensitization. In addition, the persistence of levodopa intake after surgery might hinder this beneficial process.

Adult↗
PubMed2002

Antiepileptic effect of high-frequency stimulation of the subthalamic nucleus (corpus luysi) in a case of medically intractable epilepsy caused by focal dysplasia: a 30-month follow-up: technical case report.

OBJECTIVE AND IMPORTANCE: Currently, some forms of epilepsy are resistant to both pharmacological and surgical interventions. As a result, there is a need for new therapeutic strategies. Because the nigral system modulates neuronal excitability in animal models of epilepsy, we considered therapeutic high-frequency stimulation of the subthalamic nucleus (STN). We were encouraged by the known relationship between the STN and the nigral system, as well as by our experience with high-frequency stimulation of the STN in Parkinsonian patients. CLINICAL PRESENTATION: A 5-year-old girl with pharmacologically resistant, inoperable epilepsy caused by focal centroparietal dysplasia underwent implantation with a permanent electrode in the left STN and was chronically stimulated. To date, we have followed up this patient for 30 months postoperatively. TECHNIQUE: High-frequency stimulation of the STN induced a significant voltage-dependent reduction (by 80%) in the number and severity of seizures. In addition, consistent improvement in both motor and cognitive functions was noted as a result of reduced postictal states. The effect was more prominent for seizures occurring in clusters (89% reduction) and during the day (88% reduction) than for those that occurred during sleep (53% reduction). CONCLUSION: This is the first report of epilepsy control using chronic high-frequency stimulation of the STN. Preliminary observations in three other operated patients (at 2, 12, and 18 mo) confirm these data. We think that high-frequency stimulation of the STN may hold significant future potential as a treatment for epilepsy, similar to its established role in the treatment of Parkinson's disease. This finding opens completely new experimental and therapeutic avenues for the treatment of surgically and medically intractable epilepsy.

Brain↗
PubMed2002

Surgical pathology of drug-resistant partial epilepsy. A 10-year-experience with a series of 327 consecutive resections.

Herein we reviewed the histopathological findings in 327 consecutive surgical specimens from patients with pharmaco-resistant epilepsy (PRE). Three major pathological groups (78.3% of all cases) were identified: Ammon's horn sclerosis (85 cases as an isolated lesion plus 18 as one part of a dual pathology), tumors (94 cases), and malformations (77 cases). Tumors, often associated with cortical dysplasias (CDs), were all of low histological grade and included 61 dysembryoplastic neuroepithelial tumors (DNTs), 29 gangliogliomas, and 4 pleomorphic xanthoastrocytomas (PXAs). Among the malformations were observed 52 CDs, 13 cavernomas, 8 cortical tubers, and 4 cysts. The remaining findings consisted of 16 scars (mostly post-traumatic) and 4 Rasmussen's encephalitis. Fifty-one (15.6%) specimens contained non-specific changes, and histological samples from 215 patients with presurgical implantation of electrodes revealed iatrogenic changes. All these figures are in agreement with the most recent and comparable series, and confirm the high incidence of DNTs that appear clearly as the most common tumoral entity in PRE. Our data also support the hypothesis of a close histogenetic relationship between DNT, ganglioglioma, and PXA, with a putative common origin from pluripotential progenitor CD34 positive cells of the subpial granular layer. As for CDs, our study confirms the clinical relevance of two main subtypes: severe CD (or Taylor's type CD) with neuronal cytomegaly and balloon cells, and non-Taylor's type CDs with a better outcome. Eventually, this series demonstrates that most patients have significant histopathological lesions, among which, aspects that are relevant to the diagnostic surgical pathologist are highlighted [published with a complete image database on CD-Rom].

Adolescent↗