Négligence spatiale unilatérale : une conséquence dramatique mais souvent négligée des lésions de l’hémisphère droit

Perturbation-driven paradoxical facilitation of visuo-spatial function: Revisiting the 'Sprague effect'

The 'Sprague Effect' described in the seminal paper of James Sprague (Science 153:1544-1547, 1966a) is an unexpected paradoxical effect in which a second brain lesion reversed functional deficits induced by an earlier lesion. It was observed initially in the cat where severe and permanent contralateral visually guided attentional deficits generated by the ablation of large areas of the visual cortex were reversed by the subsequent removal of the superior colliculus (SC) opposite to the cortical lesion or by the splitting of the collicular commissure. Physiologically, this effect has been explained in several ways-most notably by the reduction of the functional inhibition of the ipsilateral SC by the contralateral SC, and the restoration of normal interactions between cortical and midbrain structures after ablation. In the present review, we aim at reappraising the 'Sprague Effect' by critically analyzing studies that have been conducted in the feline and human brain. Moreover, we assess applications of the 'Sprague Effect' in the rehabilitation of visually guided attentional impairments by using non-invasive therapeutic approaches such as transcranial magnetic stimulation (TMS) and transcranial direct-current stimulation (tDCS). We also review theoretical models of the effect that emphasize the inhibition and balancing between the two hemispheres and show implications for lesion inference approaches. Last, we critically review whether the resulting inter-hemispheric rivalry theories lead toward an efficient rehabilitation of stroke in humans. We conclude by emphasizing key challenges in the field of 'Sprague Effect' applications in order to design better therapies for brain-damaged patients.

Treatment of unilateral spatial neglect after stroke using transcranial direct current stimulation (ELETRON trial): study protocol for a randomized controlled trial

Background

Unilateral spatial neglect (USN) is characterized by the inability to report or respond to people or objects that are presented in the spatial hemisphere that is contralateral to the lesioned hemisphere of the brain. USN has been associated with poor functional outcomes and long stays in hospitals and rehabilitation centers. Noninvasive brain stimulation, such as transcranial direct current stimulation (tDCS), has been used in people who have been affected by USN after stroke. The effects of such treatment could provide new insights for health professionals and policy-makers. The aim of this study will be to evaluate the effectiveness and safety of tDCS for USN after stroke.

Methods

A prospective randomized controlled trial with two parallel groups will be conducted, which will aim to recruit 60 patients with USN after ischemic or hemorrhagic stroke. Participants will be randomly placed into the following four treatment groups: (1) anodal tDCS over the right parietal lobe (n = 15), (2) cathodal tDCS over the left parietal lobe (n = 15), (3) a sham group of anodal tDCS over the right parietal lobe (n = 15), and (4) a sham group of cathodal tDCS over the left parietal lobe (n = 15). Blinded assessors will conduct two baseline assessments and one post-intervention assessment. The primary outcome measure will be the level of USN as assessed by the conventional Behavioral Inattention Tasks and the Catherine Bergego Scale. Secondary measures will include neurological capacity (based on the Scandinavian Stroke Scale), functional capacity (based on the Functional Independence Measure and Modified Rankin Scale), autonomy (based on the Barthel Index), and quality of life (based on the EuroQol-5D). Group allocation will be concealed, and all analyses will be based on an intention-to-treat principle.

Discussion

This study will explore the effects of more than 15 sessions of tDCS on the level of USN, functional capacity, autonomy, and quality of life in patients with USN after stroke. This proposed study has the potential to identify a new, evidence-based intervention that can enhance perception and independent living in patients with USN after stroke.

Trial registration

REBEC - RBR-78jvzx, registered on 13 March 2016.

A new clinical sign probably associated to left hemiplegia with left hemineglect syndrome: the crossed legs

OBJECTIVE

To describe a new clinical sign associated with left unilateral neglect syndrome (UNS) in patients with ischemic stroke.

METHOD

Head computed tomography (CT) and National Institute of Health Stroke Scale were obtained in 150 patients with ischemic stroke. Those with right cerebral vascular lesions, left hemiplegia and right leg persistently crossed over the left were submitted to specific tests for UNS. The tests were also applied to 30 patients with right cerebral vascular lesions, left hemiplegia but without crossed legs.

RESULTS

From 9 patients with persistent tendency to cross the right leg over the left, UNS was detected in 8. One patient died before the clinical tests were applied. Of the 30 patients without the crossed legs, 20 had normal clinical tests for UNS and 10 had minimal alterations, not sufficient for the diagnosis of UNS.

CONCLUSION

The right leg crossed over the left may represent a new neurological semiotic sign associated with left hemiplegia and left UNS.