How have neck muscle vibration effects on visuospatial behavior and spatial neglect been explored? A scoping review

Abstract

Introduction: Neck muscle vibration (NMV) has been proposed as a bottom-up intervention toenhance visuospatial exploration in post-stroke patients with unilateral spatial neglect (USN). Whilesome studies report enlarged visual exploration during NMV application, others find no significantimpact, highlighting inconsistencies in the literature. The diversity in NMV application methodsand the variation in visuospatial outcome measures may contribute to these conflicting findings.This study aimed to overview the methodological approaches used to investigate NMV’s effects onvisuospatial behavior in USN patients, focusing on aspects beyond sample size and study design.Methods: Among the seven databases, studies that applied NMV and assessed visual or perceptualoutcomes were included in the analysis. Two independent reviewers screened titles and abstractsto select the studies to analyze. Data about the publication, population, modalities of application,and outcomes were extracted and synthesized.Results: Twenty-five publications from 1988 to 2023 were included, involving a total of 512participants, of whom 114 (22.3%) had USN. The presence of USN was assessed based on paper-and-pencil tests. The frequency of NMV was set between 80 and 125 hz. In 22 studies, NMV wereapplied on the left side of the neck muscles. Six studies proposed multiple NMV sessions, lastingbetween 5 and 50 minutes/day, 3–5 times/week, for 2–4 weeks. One study included a follow-upperiod of up to 1.4 years. The tasks during NMV often involved indicating the subjective straightahead (SSA, n = 8), pointing out targets, or no specific activity (n = 7, each). The SSA and cancella-tion tests were the most frequent outcomes.Conclusions: NMV application modalities varied widely across studies, with only vibration fre-quency showing consistency. The tasks performed during NMV and the outcome measures werediverse and generally unrelated to activities of daily living. Therefore, NMV effects during moreecologically valid tasks should be explored.