Structural and Functional Brain Differences Related to Recurrent Shoulder Instability: A Systematic Review

Abstract

Objective47To explore (i) structural and functional brain changes associated with recurrent shoulder instability,48and (ii) their associations with clinical outcomes.49Design50Systematic review of observational and case-control studies.51Literature Search52A comprehensive search was conducted in PubMed, Web of Science, and Embase for articles53published up to December 2023. Reporting was guided by the PERSiST and PRISMA 2020 guidelines.54Study Selection Criteria55Peer-reviewed observational and case-control studies were eligible if they included individuals with56recurrent shoulder instability and assessed structural or functional brain changes using57neuroimaging.58Data Synthesis59The internal validity of included studies was evaluated using the NIH Quality Assessment Tool for60Observational and Cross-Sectional Studies and the Tool for Case-Control Studies. Outcomes were61synthesized qualitatively due to heterogeneity in imaging protocols and outcome measures.62Results63Seven studies met the inclusion criteria, involving 100 patients with recurrent shoulder instability64and 70 healthy controls. Structural brain differences assessed via voxel-based morphometry (VBM)65were not significant in three studies, and were significant in one. Six studies reported consistent66patterns of neuroplasticity in functional brain outcomes, with increased functional connectivity in67the primary sensorimotor cortex, dorsolateral prefrontal cortex, and anterior insula. Four studies68identified significant correlations between brain connectivity measures and clinical scores,69suggesting a link between sensorimotor and emotional regulation networks and functional70outcomes in recurrent shoulder instability.71Conclusion72Functional, rather than structural, brain alterations appeared to be involved in recurrent shoulder73instability. These findings support the relevance of central mechanisms in recurrent shoulder74instability and require confirmation through longitudinal designs and larger cohorts.75