Search

Prism adaptation (PA) is one of the few rehabilitation techniques for spatial neglect that directly targets physiological mechanisms underlying space representation, but its efficacy and neural mechanisms remain unresolved. Using PA and fMRI in patients with spatial neglect after an acute right-hemispheric stroke, we previously observed post-PA increases in activity in bilateral parietal, frontal, and occipital cortex during specific visuo-spatial tasks (bisection and visual search). However, given a key role of parietal areas for PA in healthy individuals, we hypothesized that such activation might differ according to the site of brain damage. We studied a group of 10 patients with focal right hemisphere stroke and spatial neglect at baseline and after PA, who were divided in two groups (5 patients with frontal and 5 patients with parietal strokes). We compared their behavioural performance and brain activation patterns during fMRI. At the behavioural level, frontal and parietal patients showed similar neglect signs on visuo-spatial tasks before PA, but frontal patients showed larger benefit from PA. Differences were also observed in cortical activity, with enhanced recruitment of right parietal areas in frontal patients and less consistent patterns in parietal patients. Furthermore, fMRI analysis during PA itself (divided in 5 successive periods) showed differential activations between group in anatomically preserved pathways, including occipital areas and cerebellum, that preceded changes in parietal areas and were specific to frontal patients. These data accord with the hypothesis that intact cerebello-parietal connections may underpin improvement of spatial neglect after PA. Altogether, these results provide important insights on brain networks involved in spatial cognition and may allow an optimal selection of patients benefiting from PA after right hemispheric stroke., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Spatial neglect is one of the main predictors of poor functional recovery after stroke. Many therapeutic interventions have been developed to alleviate this condition, but to date the evidence of their effectiveness is still scarce., Objective: The purpose of this study was to test whether combining prism adaptation (PA) and methylphenidate (MP) could enhance the recovery of neglect patients at a functional level., Methods: RITAPRISM is a multicentre, randomized, double-blind, placebo-controlled study comparing PA plus placebo (control) versus PA plus MP. 24 patients were prospectively enrolled (10 in the placebo group and 14 in the MP group)., Results: The main result is a long-term functional improvement (on the functional independence measure (FIM) and on Bergego's scale) induced by MP combined with PA. No serious adverse event occurred., Conclusions: The long-term benefit on activities of daily living (ADL) obtained in this randomized controlled trial set this intervention apart from previous attempts and supports with a high level of evidence the value of combining PA and MP in order to improve the autonomy of neglect patients. Further studies will be needed to clarify the mechanism of this improvement. Although not specifically assessed at this stage, a part of the improvement in ADL might be related to the collateral effect of MP on mood, executive functions or fatigue, and/or the combined effect of PA and MP on motor intentional bias of neglect patients., Classification of Evidence: This study provides Class I evidence that adding MP to PA improves the functional outcome of neglect patients., Who Trial Registration Id: EUCTR2008-000325-20-FR., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Unilateral spatial neglect involves a failure to report or orient to stimuli in the contralesional (left) space due to right brain damage, with severe handicap in everyday activities and poor rehabilitation outcome. Because behavioral studies suggest that prism adaptation may reduce spatial neglect, we investigated the neural mechanisms underlying prism effects on visuo-spatial processing in neglect patients. We used functional magnetic resonance imaging (fMRI) to examine the effect of (right-deviating) prisms on seven patients with left neglect, by comparing brain activity while they performed three different spatial tasks on the same visual stimuli (bisection, search, and memory), before and after a single prism-adaptation session. Following prism adaptation, fMRI data showed increased activation in bilateral parietal, frontal, and occipital cortex during bisection and visual search, but not during the memory task. These increases were associated with significant behavioral improvement in the same two tasks. Changes in neural activity and behavior were seen only after prism adaptation, but not attributable to mere task repetition. These results show for the first time the neural substrates underlying the therapeutic benefits of prism adaptation, and demonstrate that visuo-motor adaptation induced by prism exposure can restore activation in bilateral brain networks controlling spatial attention and awareness. This bilateral recruitment of fronto-parietal networks may counteract the pathological biases produced by unilateral right hemisphere damage, consistent with recent proposals that neglect may reflect lateralized deficits induced by bilateral hemispheric dysfunction., (Copyright © 2011 Elsevier Ltd. All rights reserved.)