Does galvanic vestibular stimulation reduce spatial neglect? A negative study

A systematic review of vestibular stimulation in post-stroke visual neglect

Unilateral visual neglect is a condition that negatively impacts the lives of many stroke survivors. Studies have investigated different forms of vestibular stimulation as a potential therapy, but evidence is yet to be systematically reviewed. We therefore reviewed the effects of vestibular stimulation on outcomes of neglect and activities of daily living (ADL) for people with visual neglect. We searched relevant databases up until September 2022. Eligible articles included any form of vestibular stimulation, study design, or control condition. Included participants were 18 years or older, presenting with neglect following a haemorrhagic or ischaemic stroke. Relevant outcomes were clinically validated measures of neglect and ADL. Cochrane risk of bias tools were used to assess study quality. Meta-analyses and narrative methods were used to synthesize the data. Our search returned 17 relevant studies comprising 180 participants. Meta-analyses showed no difference between galvanic vestibular stimulation and sham conditions on outcomes, whereas caloric vestibular stimulation led to improvement compared to pre-stimulation scores. Narrative syntheses showed mixed results. Clinical and methodological heterogeneity was found both within and between studies. Overall, results were inconsistent regarding the effects of vestibular stimulation as a treatment for neglect. Further trials are warranted but require more careful methodological planning.

Unilateral Spatial Neglect After Stroke: Current Insights

INTRODUCTION

Unilateral spatial neglect (USN) is a disorder of contralesional space awareness which often follows unilateral brain lesion. Since USN impairs awareness of contralesional space/body and often of concomitant motor disorders, its presence represents a negative prognostic factor of functional recovery. Thus, the disorder needs to be carefully diagnosed and treated. Here, we attempted to present a clear and concise picture of current insights in the comprehension and rehabilitation of USN.

METHODS

We first provided an updated overview of USN clinical and neuroanatomical features and then highlighted recent progresses in the diagnosis and rehabilitation of the disease. In relation to USN rehabilitation, we conducted a MEDLINE literature research on three of the most promising interventions for USN rehabilitation: prismatic adaptation (PA), non-invasive brain stimulation (NIBS), and virtual reality (VR). The identified studies were classified according to the strength of their methods.

RESULTS

The last years have witnessed a relative decrement of interest in the study of neuropsychological disorders of spatial awareness in USN, but a relative increase in the study of potential interventions for its rehabilitation. Although optimal protocols still need to be defined, high-quality studies have demonstrated the efficacy of PA, TMS and tDCS interventions for the treatment of USN. In addition, preliminary investigations are suggesting the potentials of GVS and VR approaches for USN rehabilitation.

CONCLUSION

Advancing neuropsychological and neuroscience tools to investigate USN pathophysiology is a necessary step to identify effective rehabilitation treatments and to foster our understanding of neurofunctional bases of spatial cognition in the healthy brain.

Rehabilitation of unilateral neglect: Evidence-based medicine

BACKGROUND

In the last decades, several rehabilitation methods have been developed to improve spatial neglect. These can be classified according to their theoretical basis: (i) enhance awareness of neglect behaviour through a top-down mechanism; (ii) low-level bottom-up sensory stimulation; (iii) modulation of inhibitory processes; (iv) increase arousal.

OBJECTIVE

The purpose of this study was to provide an overview of the evidence on the effectiveness of rehabilitation procedures for unilateral neglect.

METHOD

A systematic search was performed to look for all randomised controlled trials aimed at reducing left spatial neglect that included a functional assessment. In addition, recent review papers and meta-analyses were analysed.

RESULTS

Thirty-seven randomized controlled trials were found (12 bottom-up; 12 top-down; 1 interhemispheric competition; 12 combination of approaches) that included 1027 patients with neglect. Although there are some encouraging results, overall, the level of evidence remains low. Poor methodological quality and small sample sizes are major limitations in many published trials.

CONCLUSION

There is a need for well-conducted, large-scale randomised controlled trials that incorporate blinded assessments, evaluation of the generalization to activities of daily living and long-term follow-up.