1,720,986 research outputs found
Plasticity of motor cortical representations following stroke
No full textDans les suites d'un accident vasculaire moteur (AVC), il existe une réorganisation des cartes de représentation corticale des territoires musculaires pouvant intéresser aussi bien le cortex moteur primaire (CMP) que le cortex prémoteur (CPM) de l'hémisphère cérébral atteint. La contribution de ces deux aires à la plasticité corticale post-AVC est loin d'être bien définie. Notre objectif était d'étudier les modifications de cartographie corticale motrice, notamment au niveau du CMP et du CPM, et leur implication dans la récupération fonctionnelle post-AVC. Dans ce but nous avons utilisé une technique de stimulation magnétique transcrânienne (SMT) guidée par l'imagerie (neuronaviguée). Les limites anatomiques des aires corticales et l'existence de repères anatomiques fiables dans différentes régions d'intérêts ont été définies dans un premier temps. Puis nous avons établi la cartographie normale des représentations corticales motrices dans un groupe de sujets sains, notamment au moyen de cartes « probabilistes » d'obtention de réponses motrices à la SMT qui prennent en compte les variabilités interindividuelles. Nous avons ensuite étudié les modifications de ces représentations dans un groupe de patients ayant des séquelles de lésion vasculaire des régions corticales motrices. Enfin, nous avons effectué un travail prospectif de suivi cartographique d'un groupe de patients ayant présenté un AVC moteur. Dans cette dernière partie, l'analyse des données cliniques et de SMT obtenues à la phase aigüe et à trois mois de l'AVC nous a permis de caractériser les modifications anatomo-fonctionnelles corticales qui accompagnent la régression du déficit moteur, supportant en particulier le rôle central du CMP de l'hémisphère lésé. En conclusion, nous proposons des modèles d'organisation neuronale expliquant le fonctionnement du cortex moteur chez le sujet sain ainsi que la récupération motrice après une lésion partielle du CMP.Following stroke, reorganization of the motor cortical maps takes places and involves both the primary motor cortex (M1) and the premotor cortex (PMC) on the affected hemisphere. The relative contribution of each of these two cortical areas in the process of post-stroke plasticity and motor recovery remains uncertain. The present project was designed to study the cortical changes that follow a motor stroke, namely those involving M1 and the PMC, and their implications for motor recovery. For this purpose we used MRI-guided (neuronavigated) transcranial magnetic stimulation (TMS). First, we defined the anatomical limits of the cortical areas and the reliable cortical landmarks within each region of interest. We then defined a normal motor map in a group of healthy subjects. Our “probabilistic” map was based on the probability of obtaining motor responses in a given area and therefore accounted for inter-subject variability of motor representations. Thereafter we studied the modifications of the motor cortical representations in a group of patients having recovered from a motor stroke. Finally, we prospectively followed a group of patients presenting with a motor stroke. By comparing the neurophysiological and clinical data at admission and three months later, we were able to characterize the anatomo-functional cortical changes that accompany motor recovery following stroke. Our results are consistent with a major role of M1 in motor recovery. To conclude, we propose a model of how the motor cortex works in healthy subjects and during post-stroke recovery process
The use of repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) to relieve pain
No full textChronic pain resulting front injury of the peripheral or central nervous system may be associated with a significant dysfunction of extensive neural networks. Noninvasive stimulation techniques, such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current, stimulation (tDCS) may be suitable to treat chronic pain as they call act on these networks by modulating neural activities not only in the stimulated area, but also in remote re,,ions that are interconnected to the site Of stimulation. Motor cortex was the first cortical target that was proved to be efficacious in Chronic pain treatment. At present, significant analgesic effects were also shown to occur after the stimulation of other cortical targets (including prefrontal and parietal areas) in acute provoked pain, chronic neuropathic pain, fibromyalgia, or visceral pain. Therapeutic applications of rTMS in pain syndromes are limited by the short duration of the induced effects, but prolonged pain relief can be obtained by repeating rTMS sessions every day for several weeks. Recent tDCS studies also showed some effects on various types of chronic pain. We review the evidence to date of these two techniques of noninvasive brain stimulation for the treatment of pain. (c) 2008 Elsevier Inc. All rights reserved
Vertical 'half-and-a-half'syndrome
No full textThe patient's behavioural impairment and right-sided ataxia improved significantly over the following week and the patient was discharged with residual anterograde amnesia, minimal word finding difficulties and vertical diplopia. [...]we suggest that the contralateral upward gaze palsy resulted from injury to the premotor fibres that innervate the contralateral superior rectus and ipsilateral inferior oblique subnuclei within the posterior commissure. 3 4 Since both the rostral interstitial medial longitudinal fasciculus and the posterior commissure are within the territory of the thalamo-subthalamic paramedian artery, 5 their simultaneous injury would explain this unique combination of vertical eye movement deficits.PublishedN/
Palatal tremor, focal seizures, repeated miscarriages and elevated anti-thyroid antibodies
No full textNeurological manifestations of thyroid autoimmunity are heterogeneous and nonspecific. The most frequently adopted name for this entity is Hashimoto's encephalopathy although this eponym has been recently contested. In the absence of specific clinical features, diagnosis is suggested by the presence of elevated levels of anti-thyroid antibodies in the appropriate clinical context. We describe a patient with recurrent focal seizures, palatal tremor and elevated anti-thyroid antibodies but no encephalopathy. Her past medical history was marked by recurrent miscarriages. The markedly elevated thyroid antibodies, the temporal relationship between neurological symptoms and hypothyroidism, and the absence of another explanation to her symptoms suggest a causal role of thyroid autoimmunity. In the clinical setting of recurrent spontaneous miscarriages, elevated levels of anti-thyroid antibodies and neurological deficits not attributed to another disease entity, Hashimoto's encephalopathy should be suspected.PublishedN/
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Congenital agenesis of internal carotid artery with ipsilateral Horner presenting as focal neurological symptoms
No full textInternal carotid artery (ICA) agenesis is a rare developmental anomaly and is most frequently asymptomatic, but it may also present as cerebrovascular accidents. The association with Horner’s syndrome is exceptional. We present three cases of agenesis of ICA associated with Horner’s syndrome and hypochromia iridum presenting as focal neurological symptoms. A system of collaterals develops as a consequence of agenesis of the ICA, making the majority of cases asymptomatic. Three types of collateral circulations have been described. These collaterals increase the risk of aneurysm formation and the occurrence of life-threatening subarachnoid hemorrhages. The association of congenital Horner’s syndrome and hypochromia iridum without anhidrosis is highly suggestive of sympathetic pathway injury early in life. Such signs should prompt further diagnostic evaluation to demonstrate the presence of the agenesis of the carotid canal. Early diagnosis is essential to rule out potentially life-threatening associated vascular anomaliesPublishedN/
Persistent multifocal pseudo‐conduction blocks in vasculitic neuropathy without antiganglioside antibodies
No full textA woman presented with severe multifocal acute axonal neuropathy due to necrotizing vasculitis. Six years later, electrophysiological examination revealed features suggestive of persistent conduction block (CB) with increased temporal dispersion (ITD) affecting the right median and tibial nerves. A clinical case characterized by multifocal CBs that were observed several years after an initial episode of vasculitic neuropathy was recently reported. The occurrence of CBs paralleled clinical deterioration and was attributed to superimposed antiganglioside antibody‐mediated demyelination. In contrast, our patient was clinically stable and did not have antiganglioside antibodies. Nerve conduction studies showed pseudo‐CBs rather than true CBs. We suggest that pseudo‐CBs with ITD can reveal heterogeneous axonal regeneration as a sequel of a severe multifocal vasculitic neuropathy. This condition should be distinguished from the occurrence of pseudo‐CB in the acute phase of vasculitis or from superimposed immune‐mediated demyelination. Muscle Nerve 40: 290–293, 2009
A decline of compound muscle action potential (CMAP) amplitude between proximal and distal nerve stimulation, suggestive of motor conduction block (CB), can be encountered in acute vasculitic neuropathy within hours or days of symptom onset.7-9, 13 This finding likely corresponds to the fact that nerve conduction is focally interrupted at the level of axonal infarction secondary to necrotizing vasculitis, while axons remain excitable distal to the lesion for several days. Such “pseudo‐CB” is transient and disappears as Wallerian degeneration progresses in the distal segment.2, 8
Recently, persistent multifocal CBs were reported in a patient with vasculitic neuropathy, occurring in the context of cryoglobulinemia and autoimmune thyroiditis.11 This finding was attributed to the presence of IgM antiganglioside antibodies, leading to superimposed immune‐mediated demyelination. In this report we show that apparent persistent CBs can be observed late in the course of vasculitic neuropathy in the absence of antiganglioside antibodies, likely due to heterogeneous axonal regeneration rather than to segmental demyelination.PublishedN/
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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