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Biomedical subjects

F Cassim

Publications and source records attributed to F Cassim.

At least 19 recordsLinked to original sources
PubMed2006

Predominance of the contralateral movement-related activity in the subthalamo-cortical loop.

OBJECTIVE: Abnormal low- and high-frequency oscillatory activities have been linked to abnormal movement control in Parkinson's disease. We aimed to study how low- and high-frequency oscillatory activities are modulated by movement in the contralateral and ipsilateral subcorticocortical loops. METHODS: We studied mu, beta and gamma rhythm event-related desynchronisation (ERD) and synchronisation (ERS) recorded from electrode contacts in the subthalamic nucleus (STN) areas and over the primary sensorimotor (PSM) cortex. RESULTS: Mu and beta ERD/ERS patterns were very similar when comparing PSM cortex and STN areas and very different when comparing contralateral and ipsilateral structures. Beta rhythm ERS was more predominant over contralateral structures than over ipsilateral ones. Gamma rhythm ERS was only recorded from the contralateral STN area (particularly following administration of L-Dopa). For all patients, the best bipolar derivations - as defined by the earliest mu and beta ERD and the strongest beta and gamma ERS - always included the STN electrode contacts that produced the best clinical results. CONCLUSIONS: Movement-related activity is involved in the movement preparation in the contralateral subthalamo-cortical loop and in the movement execution in the bilateral subthalamo-cortical loops. SIGNIFICANCE: Contralateral beta rhythm ERD seemed to be related to bradykinesia of the limb performing the movement.

Cerebral Cortex↗
PubMed2006

The effect of repetitive transcranial magnetic stimulation on dystonia: a clinical and pathophysiological approach.

Dystonia is characterized by sustained muscle contraction, which frequently causes repetitive, twisting movements or abnormal posture. The precise pathophysiological mechanisms of dystonia are still unknown. Several studies did demonstrate that, although motor cortex hyperexcitability appears to be responsible for abnormal co-contraction and overflow to adjacent muscles, plasticity mechanisms and integrative sensorimotor processing are also likely to be involved in this condition. Current dystonia treatments are based on oral medication, injection of botulinum toxin and, in a low proportion of cases, bi-pallidal deep brain stimulation. However, treatment outcome is generally disappointing. A few researchers have reported the application of repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex or the premotor cortex, with the goal of decreasing motor cortex hyperexcitability. This article reviews all studies using this technique in dystonia and discusses rTMS therapeutic impact and its possible mechanisms of action in this indication. Currently, the premotor cortex seems to be the best target for rTMS in dystonia. Rather than merely reducing the hyperexcitability of the primary motor cortex, this technique's clinical benefit seems to result from modifications in plasticity and restoration of sensorimotor integration. The corollary technique for chronic rTMS is electrical cortical stimulation. Even though this new therapeutic tool may have therapeutic promise, more studies are required to confirm it. In particular, we need to broaden our knowledge of rTMS impact on the various forms of dystonia and to optimize target localization.

Dystonia↗
PubMed2006

Oscillatory cortical activity related to voluntary muscle relaxation: influence of normal aging.

OBJECTIVE: In this study we aimed to investigate if there are age-related differences in cortical oscillatory activity induced by self-paced muscular pure relaxation in comparison with muscle contraction as reference movement. METHODS: Event-related (de)synchronization (ERD/ERS) have been recorded related to voluntary muscle contraction and relaxation in 10 young and 10 elderly right-handed healthy subjects. The muscle relaxation task consisted in a voluntary relaxation of maintained wrist extension without any overt, associated muscle contraction. The muscle contraction task corresponded to a self-initiated brief wrist extension. RESULTS: In elderly subjects compared to young ones, mu and beta ERD preceding muscular relaxation was more widespread, beginning significantly earlier over contralateral frontocentral and parietocentral regions (p<0.05) as well as over ipsilateral regions (p<0.05). The beta synchronization was significantly attenuated (p<0.05). CONCLUSIONS: These results suggest an alteration of inhibitory motor systems and an altered post-movement somesthetic inputs processing with normal aging. These alterations were accompanied by compensatory mechanisms. SIGNIFICANCE: These age-related alterations during different phases of muscle relaxation could participate to explain global sensorimotor slowing observed with normal aging.

Adult↗
PubMed2006

Relationship between event-related beta synchronization and afferent inputs: analysis of finger movement and peripheral nerve stimulations.

OBJECTIVE: We compared beta synchronization associated with voluntary finger movement with beta synchronization produced by sensory stimulation, in order to better understand the relationship between event-related beta synchronization (ERS) and the different afferent inputs. METHODS: Twenty-four subjects performed an index finger extension. They also received three types of electrical stimulation (cutaneous stimulation of the index finger, single and repetitive stimulation of the median nerve). An EEG was recorded using 38 scalp electrodes. Beta ERS was analyzed with respect to movement offset and the stimulus (or the last stimulus in the series, for repetitive stimulation). RESULTS: Median nerve stimulation and finger extension induced more intense beta ERS than cutaneous stimulation. The magnitude of beta ERS induced by movement or by single median nerve stimulation were not different but post movement beta synchronization duration was longer than beta ERS induced by single median nerve stimulation and cutaneous stimulation. CONCLUSIONS: This study demonstrates that beta ERS depends on the type and quantity of the afferent input. SIGNIFICANCE: This work reinforces the hypothesis of a relationship between beta ERS and processing of afferent inputs.

Adult↗
PubMed2005

[Pathophysiological mechanisms implicated by high-frequency stimulation in Parkinson's disease: the restoration of high and low frequency oscillatory systems].

INTRODUCTION: Increased neuronal activity in the internal pallidum (GPi) and the subthalamic nucleus (STN) has been clearly demonstrated in Parkinsonian models, and the two structures have thus been selected as therapeutic targets for functional neurosurgery. High-frequency electrical stimulation of the GPi or the STN improves the parkinsonian symptoms but also dyskinesias directly by GPi stimulation or indirectly by reduction of L-Dopa associated with STN stimulation. According to Alexander's model of the organisation of the basal ganglia, electrical stimulation of GPi or STN should have led to uncontrolled hyperkinesia. This apparent paradox could be explained on one hand by the involvement of different anatomo-functional areas within these structures and on the other by spatial and temporal changes in neuronal discharge patterns in the basal ganglia which in turn produce variations in synchronisation. RESULTS: Event-related (de)synchronisation (ERD) has enabled us to study variations in subcortico-cortical oscillatory activity: it has been shown that high-frequency electrical stimulation of the GPi/STN increases desynchronisation of low frequency rhythms (mu and beta,<30 Hz) during movement preparation and execution and augments post-movement synchronisation. Stimulation also decreases the abnormal frontocentral spreading of desynchronisation during movement preparation. CONCLUSIONS: In accordance with previous coherence analyses, electrical stimulation of STN is likely to restore the activity of high-frequency and low-frequency systems, as evidenced by a decrease in the hypersynchronisation of low-frequency rhythms at rest and restoral of a high-frequency rhythm during movement. Stimulation may improve spatial selectivity by activating the selected programs in conjunction with the primary sensorimotor cortex, whilst inhibiting competitive programs represented by abnormal spreading outside the primary sensorimotor cortex.

Basal Ganglia↗
PubMed2004

Influence of aging on cortical activity associated with a visuo-motor task.

The aim of this study was to determine how cerebral aging influences the pattern of cortical oscillatory activity when a targeting movement with visual control is planned. Changes in cortical oscillatory activity were assessed by recording the event-related (de)synchronization (ERD/S) of micro and beta rhythms. Young and elderly subjects performed a distal movement, a proximal movement and a visuo-guided targeting movement. Our results demonstrated an increase in micro ERD over ipsilateral regions and showed the spatial extent of micro ERD over parietocentral and parietal regions during motor planning in elderly subjects compared to young ones. After the movement, the beta ERS was significantly modified (a decrease in slope and amplitude) in elderly subjects. The most pronounced age-related changes in ERD/S pattern were observed for the targeting movement. Our results suggest that motor planning is less efficient in elderly subjects. This deficit might result from impaired parietal integrative function and/or changes in inputs from subcortical structures. Subsequently, the changes observed in the post-movement phase might reflect a decrease in (reafferent) sensory inputs and hence impaired their input processing.

Adult↗
PubMed2004

[Usefulness and limitations of polymygraphic recordings in dystonia].

INTRODUCTION: Diagnosis of dystonia is based on well-known clinical findings, but electrophysiological explorations can help to establish the diagnosis. METHODS: We report 179 patients presenting primary or secondary dystonia. Polymyographic recordings were available for all. We studied activation patterns of agonist and antagonists muscles (prolonged bursts, co-contraction), presence of antagonistic gestures and other associated movement disorders such as tremor or myoclonus. RESULTS: 83.9 percent of patients presented abnormalities which evoked dystonia (prolonged bursts: 75.3 percent, co-contraction: 48.7 percent, successful antagonistic gesture successful with reduction or suppression of EMG activity, 8.7 percent). For the patients who presented no EMG abnormality, diagnosis was maintained in 22 cases because of the limitations of the exploration: intermittent symptoms, dystonia involving deep muscles which were not recorded by the surface electromyogram, or difficulties to reproduce the conditions of apparition of the dystonic symptoms during examination or to recognize a pathologic EMG pattern in hand cramps for instance. Another diagnosis was retained because of the polymyographic findings in 16.2 p.cent of these patients, particularly those who had tremor associated with dystonia (essentially diagnosis of primary writing tremor). CONCLUSION: Polymyography is an effective tool for confirming clinical findings.

Adult↗
PubMed2004

[Multiple sclerosis with sensory disturbances and hyperhidrosis of the hand].

INTRODUCTION: Hyperhidrosis may result from brain, spinal cord or peripheral nervous system injuries. We report the case of a 26-year-old patient who presented with sensorial disorders and focal hyperhidrosis of the right hand. OBSERVATION: MRI revealed multiple lesions very suggestive of active demyelinization. A lesion in the left paramedian posterior portion of the pons was enhanced after gadolinium infusion. The diagnosis of multiple sclerosis was suggested by MRI data and oligoclonal IgG bands on cerebrospinal fluid electrophoresis. CONCLUSIONS: Focal hyperhidrosis may be due to a lesion of the crossed sympathetic inhibitory tract. Although autonomic dysfunction is common during the late course of multiple sclerosis this case is, to our knowledge, the first report of focal hyperhidrosis revealing multiple sclerosis.

Adult↗
PubMed2003

Subthalamic nucleus stimulation modulates motor cortex oscillatory activity in Parkinson's disease.

In Parkinson's disease, impaired motor preparation has been related to an increased latency in the appearance of movement-related desynchronization (MRD) throughout the contralateral primary sensorimotor (PSM) cortex. Internal globus pallidus (GPi) stimulation improved movement desynchronization over the PSM cortex during movement execution but failed to improve impaired motor preparation. PET studies indicate that subthalamic nucleus (STN) stimulation partly reverses the abnormal premotor pattern of brain activation during movement. By monitoring MRD, we aimed to assess changes in premotor and PSM cortex oscillatory activity induced by bilateral STN stimulation and to compare these changes with those induced by l-dopa. Ten Parkinson's disease patients and a group of healthy, age-matched controls performed self-paced wrist flexions in each of four conditions: without either stimulation or l-dopa (the 'off' condition), with stimulation and without l-dopa (On Stim), with l-dopa and without stimulation ('on drug'), and with both stimulation and l-dopa (On Both). Compared with the Off condition, in both the On Stim and the On Drug condition the Unified Parkinson's Disease Rating Scale (UPDRS) III score decreased by about 60% and in the On Both condition it decreased by 80%. The desynchronization latency over central regions contralateral to movement and the movement desynchronization over bilateral central regions were significantly increased by stimulation and by l-dopa, with a maximal effect when the two were associated. Furthermore, desynchronization latency significantly decreased over bilateral frontocentral regions in the three treatment conditions compared with the Off condition. In Parkinson's disease, STN stimulation may induce a change in abnormal cortical oscillatory activity patterns (similar to that produced by l-dopa) by decreasing the abnormal spreading of desynchronization over frontocentral regions and increasing PSM cortex activity during movement preparation and execution, with a correlated improvement in bradykinesia. Parkinsonians under treatment displayed a desynchronization pattern close to that seen in healthy, age-matched controls, although central latencies remained shorter. The study indicates that it is possible to influence cortical reactivity related to the planning and execution of voluntary movement through the basal ganglia, and furthermore that the oscillatory activity of the PSM cortex (in addition to that of premotor areas) could be of major importance in the control of movement-associated, neural activity in Parkinson's disease.

Aged↗
PubMed2003

Effect of L-Dopa on the pattern of movement-related (de)synchronisation in advanced Parkinson's disease.

In the early stages of Parkinson's disease (PD), impaired motor preparation has been related to a delay of mu rhythm movement-related desynchronisation, suggesting hypoactivation of the contralateral, primary sensorimotor (PSM) cortex. Following movement, a decrease in the amplitude of beta rhythm movement-related synchronisation was observed over the same region. This decrease--not seen in control subjects--was thus thought to be related to an impairment in cortical deactivation. By monitoring movement-related (de)synchronisation, we aimed (i) to extend to advanced PD the observations made in less-advanced situations and (ii) to test the effect of acute L-Dopa on these abnormalities. The United Parkinson's Disease Rating Scale (UPDRS) III score decreased by about 60% following acute L-Dopa administration, and we observed the following concurrent changes: a marked increase in mu desynchronisation pre-movement latency (thus reduced delay) during movement preparation over contralateral, central regions; an increase in mu desynchronisation during movement execution over bilateral central regions; a decrease in mu desynchronisation latency over bilateral frontocentral regions, and a significant increase in beta synchronisation over contralateral, central regions after movement. Changes of mu and beta rhythm parameters seemed to be inversely correlated with bradykinesia. Mu rhythm desynchronisation latency and beta synchronisation amplitude further decreased in advanced PD compared to earlier stages of the disease, suggesting greater impairment of cortical activation/deactivation as the disease progresses. L-Dopa partially restored the abnormal mu and beta rhythm cortical (de)synchronisation patterns over the PSM cortex.

Adult↗
PubMed2003

Changes in oscillatory cortical activity related to a visuomotor task in young and elderly healthy subjects.

OBJECTIVE: In order to better understand the spatio-temporal interaction of the activated cortical areas when the movement is visuo-guided and to assess the age effect on the spatio-temporal pattern of cortical activity, we have compared a proximo-distal movement with visual-motor control and hand-eye coordination (targeting movement) with a distal and a proximal movement. METHODS: Brain's electrical activity was studied using the analysis of event-related (de)synchronizations (ERD/S) of cortical mu and beta rhythms in 17 subjects, 8 young and 9 elderly subjects. RESULTS: In both populations, we found an earlier and broader mu and beta ERD during the preparation of the targeting movement compared to distal and proximal movements, principally involving the contralateral parietal region. During the execution, a spreading over the parietocentral region during proximal movement and over the parietal region during targeting movement was observed. After the execution of proximal and targeting movements, a wider and higher beta ERS was observed only in the young subjects. In the elderly subjects, our results showed a significant decrease of beta ERS during the targeting task. CONCLUSIONS: These results suggest there was a larger recruitment of cortical areas, involving notably the parietal cortex when the movement is visuo-guided. Moreover, cerebral aging-related changes in the spatio-temporal beta ERS pattern suggests an impaired sensory integration.

Adult↗
PubMed2003

Motor preparation is more impaired in Parkinson's disease when sensorimotor integration is involved.

OBJECTIVE: This study aimed to investigate changes in spatio-temporal, event-related (de)synchronization (ERD/ERS) patterns recorded with respect to the more akinetic versus the less akinetic side during performance of a visuo-guided targeting movement when compared to an index finger extension. METHODS: Twelve de novo parkinsonian patients were recorded. ERD/ERS in mu and beta frequency bands was computed from 21 source derivations. RESULTS: When the index finger extension was performed with the less akinetic limb, mu ERD focused over contralateral central region appeared 2 s before movement. With the targeting movement, additional pre-movement mu ERD was observed over the parietal region, as well as earlier ipsilateral mu ERD. When the same movements were performed with the more akinetic limb, we observed delayed mu ERD over contralateral regions, earlier ipsilateral mu ERD and a lack of contralateral parietal mu ERD before the targeting movement. Following index finger extension for the less akinetic limb, a focused contralateral central beta ERS was recorded, increasing and spreading after the targeting movement. In contrast, for the more akinetic limb, beta ERS was dramatically attenuated and remained unchanged after the targeting movement. CONCLUSIONS: These results confirm the fact that motor programming is delayed, and provide some insight into what may well be impaired sensorimotor integration in Parkinson's disease.

Adult↗
PubMed2003

Subthalamic stimulation influences postmovement cortical somatosensory processing in Parkinson's disease.

In Parkinson's disease, poor motor performance (resulting primarily from abnormal cortical activation during movement preparation and execution) may also be due to impaired sensorimotor integration and defective cortical activity termination of the ongoing movement, thus delaying preparation of the following one. Reduced movement-related synchronization of the beta rhythm in Parkinson's disease compared to controls has been put forward as evidence for impaired postmovement cortical deactivation. We assessed the effects of subthalamic deep brain stimulation and l-dopa on beta rhythm synchronization over the premotor and primary sensorimotor cortex. Ten advanced patients performed self-paced wrist flexion in four conditions according to the presence or not of stimulation and l-dopa. Compared to without treatment, the motor score improved by approximately 60%; the beta synchronization was present over the contralateral frontocentral region and increased significantly over the contralateral central region under stimulation and under l-dopa, with a maximal effect when both treatments were associated. Our advanced patients displayed very focused and attenuated beta rhythm synchronization which, under stimulation, increased over the contralateral premotor and primary sensorimotor cortex. Stimulation and l-dopa both partly restored postmovement cortical deactivation in advanced Parkinson's disease, although the respective mechanisms probably differ. They may improve bradykinesia and cortical deactivation by reestablishing movement-related somatosensory processing at the end of the movement through the basal ganglia into the cortex.

Aged↗
PubMed2003

[Neurophysiology of parkinsonian syndromes].

Neurophysiological investigations may contribute to establish the diagnosis of different parkinsonian syndromes such as multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration, which are often suspected in case of atypical parkinsonian syndrome. They provide a means of objective analysis of certain symptoms (myoclonus for example) and identify the pathophysiological processes underlying these parkinsonian syndromes. This article reviews especially the following electrophysiological tests: autonomic nervous system analysis (sympathetic sudomotor skin response, R-R interval variation, electromyography of the external anal sphincter), surface electromyography and movement recording to investigate myoclonus, somatosensory and motor evoked potentials, brainstem reflexes (mainly the blink reflex), startle reaction, monosynaptic and long latency reflexes and finally the premotor potentials (contingent negative variation, Bereitschaftspotential) and movement-related desynchronization).

Anal Canal↗
PubMed2003

[Clinical and electrophysiological features of "cortical tremor"].

The purpose of this paper is to draw attention to one particular variant of tremor named "cortical tremor," which corresponds to rhythmic cortical myoclonus whose principal differential diagnosis is essential tremor. Diagnosis may be established with electrophysiological explorations (electromyography, accelerometry, electroencelography with back averaging, long latency reflexes, giant somesthesic evoked potentials). Clinical and electrophysiological features of 15 patients are reported and compared to cases previously published. Association with generalized or partial seizures is possible. Other cases in the family are often mentioned with a dominant autosomal transmission. The therapeutic approach is based on the use of antiepileptic drugs.

Adolescent↗
PubMed2003

[Myoclonic dystonia].

Myoclonic dystonia is mainly described as a familial entity. Nevertheless it is also a syndrome. In the first part of this review we discuss the diagnostic difficulties of myoclonic dystonia which are mainly explained by the numerous denominations. In a second part, these entities (essential myoclonus, benign hereditary chorea, myoclonic dystonia with dramatic response to alcohol) are described, then grouped into one single disease, namely inherited myoclonic dystonia, To date, only benign hereditary chorea family, mapped to chromosome 14q, is still considered as a separate disease. In a third part, the main causes of myoclonic dystonia syndrome are described, with special focus on inherited myoclonic dystonia or myoclonus-dystonia. Numerous mutations are described on the epsilon-sarcoglycan gene located on chromosome 7q21. The function of epsilon-sarcoglycan is still unknown. The clinical features are predominant alcohol-sensitive myoclonus (neck, arms) with mild and more restrained dystonia (torticollis, writer's cramp). Obsessive-compulsive disorder may be associated with the disease. Promising treatments may be medical (gamma-hydroxybutyric acid) and surgical (deep brain stimulation) although therapeutic abstention may be possible owing to the frequent benign course of the disease.

Alcoholism↗