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Biomedical subjects

M F Lévesque

Publications and source records attributed to M F Lévesque.

12 recordsLinked to original sources
PubMed1999

Subthalamic stimulation in Parkinson's disease. Preliminary results.

OBJECTIVES: We wanted to evaluate chronic subthalamic nucleus (STN) stimulation as an alternative to pallidotomy for severe Parkinson's disease symptomatology. METHODS: Nine patients met clinical criteria for unilateral standard pallidotomy. All had severe medically refractory drug-induced dyskinesia and had reached maximal daily levodopa therapy. Pre- and postoperative videos, neuropsychometric testings and clinical stagings were administered. Three patients were selected to undergo stereotactic implantation of a deep brain stimulator (DBS) after Institutional Review Board approval and informed consent. These were performed using digitized microrecordings. The other group received unilateral pallidotomy. RESULTS: At a mean follow-up of 6 months, our results support recent findings of significant major improvement in motor scores, activity of daily living and decrease in amount of daily levodopa intake by close to 50% after 3 months of stimulation. CONCLUSIONS: Chronic stimulation of the STN appears to provide significant motor improvement in patients with severe Parkinson's disease and is more beneficial than pallidotomy.

Antiparkinson Agents↗
PubMed1999

MKM-guided resection of diffuse brainstem neoplasms.

OBJECTIVES: Some primary brainstem tumors, when extensive, are considered inoperable. We wanted to assess the value of robotic image-guided microscopic surgery in the resection of these tumors and to improve survival and quality of life for these patients. METHODS: Two patients with extensive brainstem tumors were evaluated at our center. They previously underwent several biopsies, attempted partial resections, radiotherapy and shunting. They presented with progressive neurological deterioration, 'coma vigil' for several months, and required life-supporting measures prior to surgery. Both patients underwent frameless stereotactic craniotomy using a MKM robotic microscope, intraoperative neurophysiological monitoring, and extensive resection of their recurrent brainstem tumors. RESULTS: In the immediate weeks after surgery, both patients became interactive and regained major motor and cranial nerve deficits present prior to surgery. Nine months after surgery, 1 patient succumbed to pneumonia. At 2 years after the operation, 1 patient has maintained his neurological status and showed no recurrence on imaging studies. CONCLUSIONS: Image-guided surgery with an MKM microscope allows surgical outlines to be injected in the microscope viewer and facilitates resection of extensive brainstem tumors previously considered inoperable.

Adult↗
PubMed1997

Human hippocampal AMPA and NMDA mRNA levels in temporal lobe epilepsy patients.

This study was designed to determine whether hippocampal neuronal AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) and NMDA (N-methyl-D-aspartate) mRNA levels were differentially increased in temporal lobe epilepsy patients compared with those measured in control tissue from non-seizure autopsies. Hippocampi from hippocampal sclerosis patients (n = 28) and temporal mass lesion cases (n = 12) were compared with those from the autopsies (n = 4), and studied for AMPA GluR1-3 and NMDAR1-2 mRNAs using semi-quantitative in situ hybridization, along with fascia dentata and Ammon's horn neuron densities. Compared with the autopsies, and without correction for neuron counts, the mass lesion cases with neuron densities similar to autopsies showed: (i) significantly increased NMDAR2 hybridization densities for fascia dentata granule cells; (ii) increased AMPA GluR3 mRNA densities for Ammon's horn pyramids; and (iii) similar or numerically increased mRNAs for all other subunits and hippocampal subfields. Compared with the autopsies, hippocampal sclerosis cases with decreased neuron densities showed: (i) significantly decreased AMPA GluR1-2 and NMDAR1-2 hybridization densities for Ammon's horn pyramids and (ii) similar or numerically decreased mRNAs for all other subunits and subfields. However, correcting for changes in neuron densities showed that hippocampal sclerosis patients had increased AMPA and NMDA mRNA levels per neuron compared with autopsies, and in the CA2 resistant sector GluR2 mRNA levels were numerically greater than autopsies and mass lesion cases. Furthermore, relative to autopsies both sclerosis and mass lesion hippocampi showed that, in the stratum granulosum, the greatest mRNA increases were in AMPA GluR1 and NMDAR2 compared with the other mRNAs. In chronic temporal lobe seizure patients these results indicate that mass lesion and sclerosis cases show differential increases in hippocampal AMPA and NMDA mRNA levels per neuron compared with autopsies, especially for AMPA GluR1 and NMDAR2 in fascia dentata granule cells. These findings support the hypothesis that temporal lobe seizures are associated with increased ionotropic glutamate receptor mRNA levels and alterations in receptor subunit composition that probably contribute to neuronal hyperexcitability, synchronization and seizure generation.

Adult↗
PubMed1995

The pathophysiologic relationships between lesion pathology, intracranial ictal EEG onsets, and hippocampal neuron losses in temporal lobe epilepsy.

In temporal lobe epilepsy (TLE) lesion patients the pathology, location of intracranial ictal EEG onsets, and hippocampal neuron losses were compared. Patients (n = 63) were classified into: (1) Tumors (n = 26, e.g. astrocytomas, gangliogliomas); (2) vascular (n = 9, e.g. cavernous and venous angiomas); (3) developmental (n = 17, e.g. cortical dysplasia, heterotopias); or (4) atrophic (n = 11, e.g. cortical or white matter encephalomalacia). Other variables were; (1) the location of the temporal lesion in the mesial to lateral, and anterior to posterior plane, (2) a clinical history of an initial precipitating injury (IPI) prior to the onset of TLE (e.g. prolonged first seizure, head trauma), (3) hippocampal neuron densities, (4) focal or regional location by intracranial depth EEG of ictal onsets, and (5) seizure outcomes. Results showed that severe hippocampal neuron losses were associated with two statistically significant findings. First, patients with mesial lesions in or adjacent to the body of the hippocampus had greater neuron losses compared to mesial lesions anterior or posterior to the hippocampus (P = 0.04). Second, lesion patients with an IPI history had greater Ammon's horn (AH) neuron losses compared to those without IPI histories (P = 0.0005), and the profile of loss was similar to hippocampal sclerosis (HS). Granule cell losses correlated in a complex manner in that; 1) by regression analysis densities decreased with longer intervals of TLE (P = 0.006), (2) tumor patients with IPIs had less granule cell loss compared to those without IPIs intervals of TLE (P = 0.006), (2) tumor patients with IPIs had less granule cell loss compared to those without IPIs (P = 0.05), and (3) developmental patients with IPIs had greater granule cell loss than patients without IPIs (P = 0.009). Mesial-temporal depth EEG electrodes were the first areas of ictal activity in 15 of 16 patients (94%), and greater hippocampal neuron losses were not associated with focal mesial-temporal EEG onsets. Seizure outcomes were worse in tumor patients compared to HS patients (P = 0.01), and patients with post-resection seizures had incomplete resections of their lesions and/or hippocampi. These results indicate that in TLE lesion patients the amount and pattern of hippocampal neuron loss depends on the location of the lesion, the pathologic classification, and a history of an IPI. Further, despite variable neuron losses, in temporal lesion patients the hippocampus was nearly always involved in the genesis or propagation of the chronic seizures.

Case-Control Studies↗
PubMed1993

Surgical treatment of partial epilepsy arising from the insular cortex. Report of two cases.

Despite its documented connections with many limbic structures, the role of the insula in the etiology of partial seizures is poorly understood. Two patients are described in whom lesions of the insula were associated with intractable partial seizures. In the first patient, the seizures involved visceral sensory hallucinations followed by motor automatism. Seizures in the second patient began with somatic sensory hallucinations and then produced visceral motor effects. Both patients were found to have low-grade astrocytomas of the insula. In both instances, resection of the lesion and adjacent insular cortex resulted in a cure of the seizures. These cases are placed within the context of the existing literature on the subject.

Adolescent↗
PubMed1992

Ventral intermediate thalamotomy for posttraumatic hemiballismus.

An unusual case of hemiballismus following closed head injury is presented. The abnormal movement persisted for 16 years despite medical treatment. Preoperative studies did not reveal a specific lesion within the subthalamic nucleus or within the basal ganglia. A stereotactic ventral intermediate thalamotomy was performed producing a complete resolution of the ballistic movement which persisted for the length of our 12-month follow-up.

Adult↗
PubMed1992

Seizure outcome following standard temporal lobectomy: correlation with hippocampal neuron loss and extrahippocampal pathology.

The authors reviewed 149 patients who underwent standard anterior temporal lobectomies for intractable complex partial epilepsy with a mean follow-up period of 5 years. Quantitative analyses of hippocampal neuron loss showed that all patients had some cell loss compared to control hippocampi obtained at autopsy. The average hippocampal cell loss was categorized as severe (greater than 30% of autopsy control levels) or mild. Analysis of hippocampal and extrahippocampal pathologies showed that in 109 cases (73%, the hippocampal lesion group) hippocampal cell loss was mild in 17 cases (16%) and severe in 92 cases (84%); in the remaining 40 cases (27%, the extrahippocampal structural lesion group) hippocampal cell loss was mild in 24 cases (60%) and severe in 16 (40%). The first index of surgical outcome was worthwhile seizure reduction, which occurred in 94 cases (86%) with mild or severe hippocampal lesions and in 33 cases (82%) with extrahippocampal pathology. In the hippocampal lesion group, worthwhile seizure reduction occurred in 90% of cases with severe and in only 65% of cases with mild hippocampal cell loss (p = 0.015). In the extrahippocampal pathology group, worthwhile seizure was not statistically different, whether hippocampal cell loss was severe (94% of cases) or mild (75% of cases). The second index of surgical outcome was the occurrence of residual seizures in the patients with worthwhile seizure reduction, which would indicate remaining epileptogenic tissue. In the hippocampal lesion group, the incidence of residual seizures was not statistically different whether hippocampal cell loss was severe (24% of cases) or mild (45% of cases). However, in the extrahippocampal pathology group, residual seizures occurred in 53% of cases with severe cell loss (dual pathology) but in only 11% of cases with mild cell loss (p = 0.025). Worthwhile seizure reduction can be predicted by the presence of either severe hippocampal cell loss or an extrahippocampal structural lesion. However, residual seizures more frequently follow in cases with a combination of both (extrahippocampal pathology associated with severe hippocampal cell loss, or dual pathology), suggesting that epileptogenic tissue more likely extends outside the boundaries of a standard temporal lobectomy.

Adult↗
PubMed1991

Surgical treatment of limbic epilepsy associated with extrahippocampal lesions: the problem of dual pathology.

The authors present their review of 178 patients who underwent en bloc temporal lobectomies as surgical treatment for intractable epilepsy. Hippocampal cell density was quantitatively analyzed and the histology of the anterior temporal lobe was reviewed. Fifty-four patients (30.3%) had evidence of extrahippocampal lesions in addition to neuronal cell loss within the hippocampus (the dual pathology group). The pattern of cell loss was analyzed in the remaining 124 cases (69.7%) with no extrahippocampal pathology, and compared with that of the dual pathology group and a control group of four nonepileptic patients. Hippocampal cell loss was found in almost all epileptic patients compared to the control group. Severe cell loss greater than 30% of control values was found in 88.7% of patients without extrahippocampal lesions, but in only 51.8% of patients with dual pathology. The difference between these two groups was statistically significant (p less than 0.001). In the dual pathology group, lesions of different pathology had a significant relationship with the degree of hippocampal cell loss: all 12 patients with glioma had mild cell loss, whereas all 13 patients with heterotopia were associated with severe cell loss. Severity of hippocampal cell loss was also analyzed in relation to seizure history: a prior severe head injury was associated with severe cell loss. Other factors such as seizure duration, secondary generalization, or family history of seizures were not associated with hippocampal damage. Dual pathology may produce a combination of neocortical and temporolimbic epilepsies that warrants a precise definition of the true epileptogenic area prior to surgical treatment.

Adolescent↗
PubMed1990

Accuracy of MR-guided stereotactic electrode implantation. 1. Preimplantation correlation with the Talairach system.

The accuracy of stereotactic electrode implantation using MR guidance and a computerized imaging system was compared to the conventional Talairach system, using ventriculography and a stereotactic atlas. A combined methodology of two stereotactic approaches was used, with a modified Leksell and a Todd-Wells frame. The coordinates of temporo-limbic structures and the length of the AC-PC line were measured prior to implantation in 10 epileptic patients undergoing the combined procedure. Relative differences in single and three-dimensional values were obtained for 68 targets within the temporal lobe. Lengths of AC-PC lines were measured in 9 patients. Statistical differences were found for all temporal coordinates, but the AC-PC line did not differ significantly.

Brain Mapping↗
PubMed1990

Stereotactic investigation of limbic epilepsy using a multimodal image analysis system. Technical note.

A methodology has been developed for stereotactic investigation of limbic epilepsy using an image-analysis system that simultaneously displays different structural and functional images of the brain. The validity and accuracy of this system were established with phantom studies. Surgical planning and electrode implantation are guided by stereotactic magnetic resonance imaging, digital subtraction angiography, and position emission tomography. This methodology provides the spatiotemporal relationship of cerebral structure and function necessary to identify seizure onset and propagation in human limbic system epilepsy.

Brain Mapping↗
PubMedDate not supplied

Correlation of unit recordings with regional cell counts in epileptogenic human temporal lobe.

The previously reported diminished incidence of neuronal activity recorded from areas ipsilateral to a seizure focus may result from either cell loss or pathophysiologic changes in hippocampus and related structures. We examined records of single-cell discharge from 471 electrode bundles in 62 patients who later had cell counts taken from samples of resected tissue. Analysis of variance showed that amygdala and parahippocampal gyrus had more activity than hippocampus and the subicular complex and that the resected side had less activity overall. Only the posterior subicular complex showed more high-amplitude (> 50 microV) activity on the epileptogenic side; all other areas showed more activity contralaterally. Activity between 25 and 50 microV did not differ across sides or structures. Percentage of maximal cell count was correlated with the number of electrodes with high-amplitude activity only in the subicular complex. Low-amplitude activity in nonresected hippocampus, however, was strongly negatively correlated with cell counts on the resected side, perhaps owing to compensatory mechanisms. Cell counts in hippocampus correlated negatively with high-amplitude unit activity in resected amygdala, suggesting reciprocity between these areas. These results suggest that the amount of cell activity recorded from mesiotemporal structures involves bilateral factors more complex than simple cell loss.

Amygdala↗