PO106 / #1015 IS THE USE OF REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION (RTMS) SYSTEMATICALLY SUCCESSFUL IN THE REHABILITATION OF CHRONIC SPATIAL NEGLECT AFTER STROKE?

International audienceIntroduction: Neglect represents a neurological condition consisting in the lack of awareness in the contralesional hemispace (generally the left, after a right hemisphere lesion), precluding the rehabilitation of patients' deficits. By targeting cortical nodes and their associated networks, non-invasive brain stimulation techniques are currently used in neglect rehabilitation, being based on the inter-hemispheric rivalry hypothesis (Kinsbourne, 1977), that posits the existence of mutual inhibitions between the two brain hemispheres. The main approach consists in the inhibition of intact systems in the contralesional structures in order to restitute the lost function. Materials / Methods: The present study is based on data acquired in the PHRC Regional NEGLECT, a multicentric double-blind clinical trial evaluating the efficacy and safety of a repetitive transcranial magnetic stimulation (rTMS) regime for 2 weeks, to improve visuo-spatial neglect in 21 stroke patients (10 men), at least at 2 months after the stroke. All patients performed neurological, neuropsychological (paper and pencil and computerbased reaction time target detection-localization tests) and neuroradiological evaluations, before and during the real or sham rTMS program, as well as 10 days, 14 days, 4 weeks and 24 weeks following the end of the rTMS. Based on the neuropsychological evaluation, a Spatial Bias Compound Score (SBCS) was computed. During the rTMS, the coil of a standard Magstim Superrapid machine was applied on the intact left posterior parietal cortex (PPC), at the posterior part of the intraparietal sulcus. In line with Kinsbourne's hypothesis, we aimed at decreasing the 'excess' of inhibitory information that is projected transcallosally from the intact left PPC onto the damaged right PPC. Specifically, we assessed the effects of rTMS in the treatment of neglect and we documented lesional patterns of patients, with the aim to characterize predictive factors of response to treatment. Results: Statistical analyses did not emphasize any changes in the SBCS between baseline and the four post rTMS treatment evaluations, between the sham and the rTMS groups (all p > 0.05). However, computer-based tests showed significant improvement in the rTMS group comparing with the sham group. The anatomical analysis emphasized heterogenous lesional patterns for both groups. Discussion: These results suggest that a reappraisal of the inter-hemispheric rivalry hypothesis and/or of inhibitory effects of rTMS is necessary. Conclusions: Future stimulation protocols should be individually designed, considering the presence of the lesion and of the impaired/ preserved networks, in order to efficiently rehabilitate neglect. Acknowledgements: Authors thank l'Assistance Publique-Hôpitaux de Paris for financial support in conducting this study. Learning Objectives: 1 To learn about the rehabilitation of neglect 2 To understand the physiological basis of neglect rehabilitation by using rTMS 3 To conceive future stimulation protocols individually designed

La stimulation magnétique trans-crânienne répétitive à basse fréquence (rTMS) au niveau de l'hémisphère gauche est-elle efficace pour la rééducation de la négligence spatiale unilatérale persistante après un AVC ?

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Game theoretical mapping of white matter contributions to visuospatial attention in stroke patients with hemineglect

International audienceWhite matter bundles linking gray matter nodes are key anatomical players to fully characterize associations between brain systems and cognitive functions. Here we used a multivariate lesion inference approach grounded in coalitional game theory (multiperturbation Shapley value analysis, MSA) to infer causal contributions of white matter bundles to visuospatial orienting of attention. Our work is based on the characterization of the lesion patterns of 25 right hemisphere stroke patients and the causal analysis of their impact on three neuropsychological tasks: line bisection, letter cancellation, and bells cancellation. We report that, out of the 11 white matter bundles included in our MSA coalitions, the optic radiations, the inferior fronto-occipital fasciculus and the anterior cingulum were the only tracts to display task-invariant contributions (positive, positive, and negative, respectively) to the tasks. We also report task-dependent influences for the branches of the superior longitudinal fasciculus and the posterior cingulum. By extending prior findings to white matter tracts linking key gray matter nodes, we further characterize from a network perspective the anatomical basis of visual and attentional orienting processes. The knowledge about interactions patterns mediated by white matter tracts linking cortical nodes of attention orienting networks, consolidated by further studies, may help develop and customize brain stimulation approaches for the rehabilitation of visuospatial neglect

Testing the therapeutic effects of transcranial direct current stimulation (tDCS) in semantic dementia: a double blind, sham controlled, randomized clinical trial

International audienceBACKGROUND: Semantic dementia is a neurodegenerative disease that primarily affects the left anterior temporal lobe, resulting in a gradual loss of conceptual knowledge. There is currently no validated treatment. Transcranial stimulation has provided evidence for long-lasting language effects presumably linked to stimulation-induced neuroplasticity in post-stroke aphasia. However, studies evaluating its effects in neurodegenerative diseases such as semantic dementia are still rare and evidence from double-blind, prospective, therapeutic trials is required.OBJECTIVE: The primary objective of the present clinical trial (STIM-SD) is to evaluate the therapeutic efficacy of a multiday transcranial direct current stimulation (tDCS) regime on language impairment in patients with semantic dementia. The study also explores the time course of potential tDCS-driven improvements and uses imaging biomarkers that could reflect stimulation-induced neuroplasticity.METHODS: This is a double-blind, sham-controlled, randomized study using transcranial Direct Current Stimulation (tDCS) applied daily for 10 days, and language/semantic and imaging assessments at four time points: baseline, 3 days, 2 weeks and 4 months after 10 stimulation sessions. Language/semantic assessments will be carried out at these same 4 time points. Fluorodeoxyglucose positron emission tomography (FDG-PET), resting-state functional magnetic resonance imaging (rs-fMRI), T1-weighted images and white matter diffusion tensor imaging (DTI) will be applied at baseline and at the 2-week time point. According to the principle of inter-hemispheric inhibition between left (language-related) and right homotopic regions we will use two stimulation modalities - left-anodal and right-cathodal tDCS over the anterior temporal lobes. Accordingly, the patient population (n = 60) will be subdivided into three subgroups: left-anodal tDCS (n = 20), right-cathodal tDCS (n = 20) and sham tDCS (n = 20). The stimulation will be sustained for 20 min at an intensity of 1.59 mA. It will be delivered through 25cm2-round stimulation electrodes (current density of 0.06 mA/cm2) placed over the left and right anterior temporal lobes for anodal and cathodal stimulation, respectively. A group of healthy participants (n = 20) matched by age, gender and education will also be recruited and tested to provide normative values for the language/semantic tasks and imaging measures.DISCUSSION: The aim of this study is to assess the efficacy of tDCS for language/semantic disorders in semantic dementia. A potential treatment would be easily applicable, inexpensive, and renewable when therapeutic effects disappear due to disease progression