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Biomedical subjects

L Defebvre

Publications and source records attributed to L Defebvre.

At least 73 records · Page 4Linked to original sources
PubMed2001

Intermuscular coherence in Parkinson's disease: relationship to bradykinesia.

We hypothesised that bradykinesia may be partly due to the failure of the corticomuscular system to engage in high frequency oscillatory activity in Parkinson's disease (PD). In healthy subjects such oscillations are evident in coherence between active muscles at 15--30 Hz. We therefore investigated the effects of therapeutic stimulation of the basal ganglia on this coherence and related it to changes in bradykinesia in the contralateral arm. Increases in coherence at 15--30 Hz and improvements in bradykinesia upon stimulation were correlated (r = 0.564, p < 0.001). This suggests that the basal ganglia modulate oscillatory activity in the corticomuscular system and that impairment of the motor system's ability to engage in synchronised oscillations at high frequency may contribute to bradykinesia in PD.

Electric Stimulation Therapy↗
PubMed2001

[Gait disorders in Parkinson disease. Neuroanatomic and physiologic organization of gait].

GAIT IS A VOLUNTARY, AUTOMATIC AND REFLEX RHYTHMIC ACTIVITY: It is generated by a central pattern generator identified from animal models. This spinal gait generator (SGG) is controlled by various parts of the central nervous system: the descending tracts and locomotor regions of the brainstem, the cerebellum, the basal ganglia, the motor and parietal cortex and the hippocampus. Kinesthetic inputs which project to the SGG and the cerebellum, play an important role in the production of postural reflex responses; vestibular and visual inputs mainly control balance. GAIT MAINLY DEPENDS ON THE RELATIONSHIP BETWEEN POSTURE BALANCE AND MOVEMENT: As concerns posture each segment is under the control of both peripheral and central nervous systems and is used as a system of reference to organize movements of adjacent segments. Balance is maintained by sensory inputs which provide corrective mechanisms: anticipatory postural responses, reflex postural responses and voluntary responses. DIFFERENT DESCRIPTIVE PARAMETERS MAY BE PROPOSED: Analysis of kinematic (displacement, speed and acceleration of segments) and kinetic parameters during the four successive stages of gait (posture, initiation, rhythmic gait and return to the initial posture) provides an understanding of neurological gait disorders. In particular the relationship between the center of pressure and the center of gravity is used to analyze infraclinical gait abnormalities. NEW AND SOPHISTICATED INVESTIGATIONS METHODS ARE AVAILABLE: The optoelectronic system provides a tridimensional analysis of movement and can be combined with forceplate and electromyographic recordings. These methods constitute an interesting contribution to the clinical analysis of gait. CLASSIFICATION: This is established according to clinical data and the positionment of the lesion among the structures of the nervous system. The physiopathological approach is then specified taking into account the lesions of the muscular, skeletal and nervous structures.

Brain↗
PubMed2001

[Gait disorders in Parkinson disease. Clinical description, analysis of posture, initiation of stabilized gait].

A WELL INFORMED DESCRIPTION: The parkinsonian posture is generally described as a stooped one. At the beginning of the disease, the gait troubles remain moderate; gradually the gait is composed of small steps without a wide base; the patient tends to run after his centre of gravity by accelerating the step (festination phenomenon). Difficulties occurs for starting up (delay of gait initiation), for about-turn or for clearing obstacles. Kinetic jammings and standing around (freezing) can last several seconds and be responsible for falls. POSTURAL INSTABILITY, A MAJOR SYMPTOM IN PARKINSON'S DISEASE: This symptom is little improved by therapies and is responsible for serious disability. Postural instability induces a disequilibrium and is partially due to a simultaneous antagonist muscles contraction and to the impossibility of modifying postural responses to changing support conditions. The passive viscoelastic properties of muscles and tendons constitute a first line of defence against the disequilibrium and contribute to postural stability in the case of medium disturbances. Automatic and voluntary postural responses which come into play in the case of major disturbances can also be impaired (delay or defect of the responses). GAIT INITIATION FAILURE ARE FREQUENT: They result from an increase of the postural phase and a decrease of the propulsion forces, depending on a deficit of the postural anticipation mechanisms and also the sequential organization and the integration of two different motor programs, postural and locomotor. They can be controlled partially with sensory stimuli, notably visual inputs. DATA CONCERNING STABILIZED WALKING AND ITS PATHOPHYSIOLOGY REMAINS TO BE CLARIFIED: Spatial and temporal parameters are impaired: speed, step length and swing phase are reduced, while cadence increases to compensate these troubles. These modifications are the consequence of an incapacity to produce internal marks to generate regular steps. When the parkinsonian patient is supplied with external marks, these parameters can be normalized. From a pathophysiological point of view, gait disorders could result from defective central integration of proprioceptive information during movement within the basal ganglia, associated with a visual perceptive deficit linked with a retinal dopaminergic cells dysfunction and finally from an impairment of the proprioceptive feedback of the load receptors in the leg extensor muscles.

Antiparkinson Agents↗
PubMed2001

[Gait disorders in Parkinson disease. Gait freezing and falls: therapeutic management].

GAIT ARRESTS: They affect the evolution of the disease. This freezing phenomenon which induces falls sometimes constitutes an initial sign. Like the gait initiation failure, freezing can be controlled by sensory stimulation, notably visual inputs, but also by more sustained attention. FALLS ARE MAINLY CONNECTED WITH BOTH POSTURAL INSTABILITY AND RIGIDITY: They are poorly influenced by dopaminergic therapies. The progressive decrease of step width represents a main factor in their occurrence. PRECOCITY OF GAIT DISORDERS IS UNUSUAL IN PARKINSON'S DISEASE: Other parkinsonian syndromes such as progressive supranuclear palsy, multiple system atrophy and vascular parkinsonian syndrome must then be evoked. Their association with a cognitive impairment and abnormal sphincter behaviour infers a diagnosis of normal pressure hydrocephalus. GAIT IMPROVES WITH L-DOPA THERAPY: Speed, step length and duration of the swing phase are increased without change of cadence. Progressive loss of L-dopa efficiency on gait and postural stability contrasts with the persistent effect on tremor, rigidity and bradykinesia; a functional abnormality of nondopaminergic systems can explain these symptoms. In the following stages, gait troubles increased by motor fluctuations and abnormal involuntary movements are less controlled by L-dopa therapy. PHYSICAL THERAPY PLAYS A MAJOR ROLE IN THERAPEUTIC MANAGEMENT: An individual or collective rehabilitation project must be established according to the stage of evolution; the exercises aim to protect postural control and coordination. Visual or sound rhythmic inputs can be employed in the case of gait initiation failure. THE EFFECTS OF FUNCTIONAL NEUROSURGERY ARE IN THE COURSE OF EVALUATION: Thermolesion and chronic electrical stimulation of deep brain structures have opposite effects on gait troubles. Bilateral thalamotomy or pallidotomy are sometimes a source of disequilibrium. Chronic thalamic stimulation does not induce either benefits or adverse effects. On the other hand, stimulation of the internal pallidum improves gait kinematic parameters; improved postural adjustments have also been reported. The effect of subthalamic nucleus stimulation is comparable to that of L-dopa, however the long-term effect remains to be evaluated.

Accidental Falls↗
PubMed2001

Genetic analysis of synphilin-1 in familial Parkinson's disease.

alpha-Synuclein is present in Lewy bodies of patients with both sporadic and familial Parkinson's disease. However, pathogenic mutations Ala30Pro and Ala53Thr in alpha-synuclein are rare causes of disease. Synphilin-1 has been demonstrated to associate with alpha-synuclein and promote the formation of cytosolic inclusions in vitro. Two-point genetic linkage analysis of a dinucleotide repeat within the synphilin-1 gene initially implicated this locus as a cause of Parkinson's disease in three of nine families. However, subsequent haplotype, sequencing, and association analyses in these three families and an independent case-control series suggest that variability within the locus does not confer susceptibility to Parkinson's disease.

Aged↗
PubMed2001

Chronic bilateral pallidal stimulation and levodopa do not improve gait in the same way in Parkinson's disease: a study using a video motion analysis system.

Chronic bilateral internal globus pallidus (GPi) stimulation allows control of levodopa induced dyskinesias (LID) and motor symptoms in severe Parkinson's disease (PD). The effect on gait has not been clearly established. Different results have been reported, mostly consisting of clinical data. The aim of this study was to evaluate, by means of a video motion analysis system (optoelectronic VICON system), the influence of bilateral GPi stimulation on gait in PD. Five patients underwent bilateral GPi stimulation. The preoperative and postoperative (3 months after surgery) clinical gait disturbances (items 29 and 30 of the motor UPDRS), as well as spatial and temporal gait measurements (namely cadence, velocity, stride and step times, single and double limb support times, stride and step lengths) were analysed in off condition (the patient had received no treatment for 12 hours or merely the lowest dose of levodopa allowing him to walk for the gait analysis) and in the on drug condition (after administration of 200 mg of levodopa). The gait analysis was performed with the VICON system. In off condition, there was a statistically significant improvement after surgery for UPDRS III and gait (clinically assessed). In on drug condition, there was a significant improvement for LID whereas UPDRS III and clinical assessment of gait were unchanged. The VICON system also showed that surgery improved gait especially in off condition, but also in on drug condition. Our method allowed exact quantification of the influence of surgery on gait characteristics. As compared with levodopa treatment, the effect of stimulation seems to be different. Indeed, the results suggest only limited effects of pallidal stimulation on the control of stride length and rather point to compensatory additional mechanisms.

Aged↗
PubMed2001

Influence of chronic bilateral stimulation of the subthalamic nucleus on cognitive function in Parkinson's disease.

BACKGROUND: The clinical efficacy of chronic deep brain stimulation in the treatment of parkinsonian patients with severe levodopa-related motor adverse effects has been repeatedly shown. Bilateral subthalamic nucleus (STN) stimulation has been shown to present an advantage over pallidal stimulation as it induces a higher antiakinetic effect and has positive effects on all parkinsonian symptoms. The morbidity of such surgery is usually considered to be very low. However, few studies have extensively examined the effects of chronic STN stimulation on cognitive function. OBJECTIVE: The aim of the present study was to assess the effects of chronic bilateral STN stimulation on performance in an extensive battery of neuropsychological tests, three months and one year after surgery. METHODS: Nine patients with Parkinson's disease were selected for STN electrodes implantation. They underwent a neuropsychological evaluation at one month before and at three months after surgery. Six of them were examined again at one year after surgery. RESULTS: Before surgery, no patient showed cognitive decline. At three months after surgery, no modification was observed for most tasks. The information processing speed tended to improve. There was a significant reduction of the performance in a delayed free recall test and a trend toward a significant reduction of categorial word fluency. At one year after surgery, most task measures did not change. Slight impairment was observed for tasks evaluating executive function. Examination of individual results showed that some patients (30% at 3 months after surgery) showed an overall cognitive decline. Behavioural changes were also observed in 4 patients with overall cognitive decline in one of them. CONCLUSION: In general, STN deep brain stimulation can be considered as a significant contribution to the treatment of severe Parkinson's disease However, in some patients it can induce overall cognitive decline or behavioural changes.

Cognition Disorders↗
PubMed2001

No genetic association of the ubiquitin carboxy-terminal hydrolase-L1 gene S18Y polymorphism with familial Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disorder for which genetic susceptibility has been documented in sporadic and familial cases. Recently, a polymorphism located in exon 3 at codon 18 (S18Y) of the Ubiquitin Carboxy-terminal Hydrolase-L1 (UCH-L1) gene has been associated with the disease in 2 populations of German origin and also in a Japanese population. We tested the impact of this polymorphism in a French sample of familial PD patients (n = 114) and controls (n = 93). No association was observed, indicating that this polymorphism did not confer susceptibility for familial PD in our population, even among the youngest age of onset group. This observation suggests that the previous positive results obtained may reflect mechanisms restricted to the sporadic form of the disease or to a founder effect of the disease susceptibility.

Age of Onset↗
PubMed2001

Memory and executive function in sporadic and familial Parkinson's disease.

Some studies have demonstrated that the motor symptomatology in sporadic and familial Parkinson's disease was identical. From a physiopathological point of view, and perhaps in the future from a therapeutic point of view, it seems important to determine whether sporadic and familial Parkinson's disease are also similar with regard to cognitive impairment. The aim of the present study was to assess cognitive functions in patients suffering from sporadic and familial Parkinson's disease. Executive functions and memory were investigated in particular. Two groups of 12 patients with Parkinson's disease (sporadic and familial) and 12 healthy controls performed a set of tasks known to evaluate different aspects of executive function and memory. One-way analysis of variance tested for significant group effects, and when justified, post hoc analysis was performed. Cognitive impairment was different in sporadic and familial forms of Parkinson's disease. Indeed, although executive function was impaired in both groups of patients, deficits in tests of explicit memory recall were only observed in patients with sporadic Parkinson's disease. Although the impairment observed in both groups of patients suggests a disruption of the striatoprefrontal circuits, this disruption seems to be quantitatively more important and more widespread in the sporadic patients than in the familial ones. In both patient groups, the deficits probably result from dopaminergic and nondopaminergic deprivation and a greater participation of nondopaminergic factors in patients with sporadic Parkinson's disease could be suggested. In this group, a xenobiotic could be responsible for an acquired metabolic defect involving more widespread structures of the striatoprefrontal circuits, leading to disruption of nondopaminergic loops. Cholinergic deprivation is considered in particular.

Adult↗
PubMed2001

[Cytomegalovirus rhombencephalomyelitis in an immunocompetent subject].

We report the clinical and MRI findings of a 31-year-old healthy immuno-competent patient who presented following 48 hours of diffuse headache with progressive and severe rhombencephalomyelitis signs. Cerebral and medullar MRI confirmed the central nervous system improvement. Serology showed relation with cytomegalovirus infection. Spontaneous improvement was observed and favoured by ganciclovir administration.

Adult↗
PubMed2001

Event-related variations in the activity of EEG-rhythms. Application to the physiology and the pathology of movements.

The averaging of the ongoing activity of the electroencephalogram (EEG) allows extracting the potentials that are time-locked and phase-locked to an event. These potentials are described as evoked potentials. There is another type of change in the ongoing EEG, which is time-locked but not phase-locked to an event: the EEG rhythm reactivity, also called "Event-Related Desynchronization and Synchronization" (ERD/ERS) by Pfurtscheller. These changes are often visible to the naked eye but they cannot be extracted by the averaging technique. Their quantification requires another method, which was suggested by Pfurtscheller and Aranibar in 1977. This method consists in measuring the temporal evolution of the power of EEG signal within a given frequency band before, during, and after an event. ERD corresponds to the decrease in power of an EEG rhythm related to an event. Conversely, ERS corresponds to an increase in amplitude of an EEG rhythm related to the event. ERD represents the activation of the subjacent cortical areas. ERS would partly traduce the setting at rest of the cortex; it would also be related to the somesthetics afferents inputs. This method can be applied to the study of cortical activation in many situations: memory tasks, auditory processing, attention, anticipatory behavior, and voluntary movement. Thus, a voluntary self-paced movement of the dominant hand is preceded by an ERD of mu and beta rhythms occurring respectively 2 000 and 1 500 ms before the movement onset. This ERD is recorded over the contralateral central region. It becomes bilateral at the movement onset and reaches its maximum at the movement offset. It is then followed by an ERS of the beta rhythms. We show that ERD/ERS phenomena vary with the type of movement, and that their study allows exploring the modifications of cortical excitability that are observed in Parkinson's disease and in epilepsy with focal motor seizures.

Journal Article↗
PubMed2000

[Chronic electric stimulation of the internal globus pallidus and subthalamic nucleus in Parkinson disease].

PATHOPHYSIOLOGY: In Parkinson's disease, the neurodegenerative process of the nigrostriatal dopaminergic pathways induces an increase in activity of the subthalamic nucleus and the medial globus pallidus, which cause inhibition of thalamo-cortical outputs explaining parkinsonism. HIGH-FREQUENCY DEEP BRAIN STIMULATION: The adverse effects induced by lesions of subcortical structures (thalamotomy, pallidotomy) have increased interest in chronic electrical stimulation proposed as a new therapy in Parkinson's disease. This technique is reversible and can be modulated with less adverse effects. TWO TARGETS: Two targets may be proposed in case of severe motor fluctuations: the medial globus pallidus and the subthalamic nucleus. Pallidial stimulation improves dramatically levodopa-induced dyskinesia and, with a variable degree, the parkinsonian triad. Subthalamic stimulation rapidly reverses akinesia, rigidity and tremor and also dyskinesias which progressively tend to diminish after decreasing L-dopa dosage. LONG-TERM EFFICACY: A follow-up period of a few years has confirmed that the beneficial effect is maintained. However, stimulation dose not prevent the development of certain symptoms (postural impairment, cognitive decline). LIMITED INDICATIONS: Chronic electrical stimulation of medial globus pallidus and subthalamic nucleus may be proposed for parkinsonian patients with severe motor fluctuations associated with abnormal involuntary movements which are not controlled by different medical therapies. Parkinsonian symptoms must still be levodopa responsive and cause severe clinical disability severely limiting daily living activities. Cognitive impairment and other severe pathologies are contraindications.

Electric Stimulation Therapy↗
PubMed2000

Thalamic tremor: correlations with three-dimensional magnetic resonance imaging data and pathophysiological mechanisms.

Tremor associated with a single focal thalamic lesion has rarely been reported. Furthermore, the exact localization of the lesions is difficult to determine because of the imprecision of "conventional" radiology (computed tomography scan and/or "standard" magnetic resonance imaging). The aim of this study was to identify which thalamic structures are involved in tremor associated with a single focal thalamic lesion. We selected two patients who presented with unilateral postural and kinetic tremor of the upper limb related to a localized thalamic infarction. Three-dimensional T1-weighted magnetic resonance imaging sequence (MP-RAGE sequence) was used to determine the precise topography of the lesions by stereotactic analysis using the atlas of Hassler. The lesions were located within the pulvinar, the sensory nuclei, the mediodorsal nucleus, and the ventral lateral posterior nucleus (according to the classification of Hirai and Jones), the latter including the ventral intermediate nucleus (Vim according to the classification of Hassler). However, the Vim was spared. The subthalamic area, which can induce tremor, was not involved. After having compared the topography of the lesions with the clinical findings, we suggest that thalamic tremors may result from the interruption of the cerebellar outflow tract to the Vim within the thalamus.

Adult↗
PubMed2000

The first identified French family with dentatorubral-pallidoluysian atrophy.

We report the first French family with dentatorubral-pallidoluysian atrophy (DRPLA) in which three members, a 36-year-old woman (proband), her 34-year-old sister, and 14-year-old brother were affected. There was no family history of DRPLA and their father presented at age 66 with pes cavus but without any other neurologic symptoms. Molecular analysis of the DRPLA gene from blood leukocytes showed CAG repeat sizes to be 68/16 in the proband, 62/15 in her father, and 16/16 in her mother. This study provides support for the variable clinical presentation of this disease with incomplete penetrance in the father and demonstrates that DRPLA can be observed in the French Caucasian population.

Adult↗
PubMed2000

Linkage exclusion in French families with probable Parkinson' s disease.

We analyzed the segregation of genetic markers spanning chromosomal regions 2p13, 4p14-15, 4q21-23, 6q25-27, and 17q21 in nine French families affected by autosomal-dominant probable Parkinson's disease. These regions have been linked or associated with familial Parkinson's disease. Multipoint linkage and haplotype analyses excluded 2p13 and 4p14-15 loci in five of nine families. For three families, which were equivocal for two-point linkage at D4S405, the ubiquitin carboxy-terminal hydrolase gene (UCH-L1) was sequenced. In one family, a novel UCH-L1 M124L mutation that did not segregate with early-onset disease was identified. This suggests that rare variants in this gene may not be pathogenic. In seven of nine families, it could be inferred that affected individuals did not share 4q21-23 (alpha-synuclein) haplotypes. All families were unequivocally excluded by haplotype analysis from the parkin locus on 6q25-27. Finally, the 17q21 region was excluded in four of nine families, and no mutation in the tau gene was identified in the five remaining families. Findings from this study confirm genetic heterogeneity within familial parkinsonism.

Adult↗
PubMed2000

A case of severe dysexecutive syndrome consecutive to chronic bilateral pallidal stimulation.

In treatment for severe Parkinson's disease (PD), a recent procedure was developed which consists of implanting electrodes in the internal Globus Pallidus (GPi) for chronic electrical stimulation. The consequences on cognitive function of such an intervention are quite variable. Although most group studies observed no significant post-operative change, individual cases of post-operative cognitive impairment were reported. The present study reports the case of a PD patient who underwent bilateral implantation of deep brain stimulation electrodes in the GPi and who, after surgery, suffered from a severe dysexecutive syndrome. An extensive neuropsychological examination showed a selective negative effect of pallidal stimulation on tests assessing executive function. When the stimulation was turned off, the impairment was partly reversible. This observation emphasizes the role of the GPi in executive function.

Attention↗