Brain plasticity in patients with lateral ankle sprain and chronic ankle instability: a systematic review

Introduction: Research investigating LAS and CAI has essentially focused on local adaptations. Recently, growing evidence is supporting the hypothesis neural plasticity occurs at both the spinal and cortical levels following (repeated) ligamentous ankle injury. These alterations might explain persisting dysfunctions, an increased injury risk, and the increased probability of developing CAI. This systematic review synthesizes the literature on brain plasticity following LAS and CAI.
Methods: Studies eligible for this systematic review investigated the brain with direct outcomes measures in patients with LAS or CAI. The following electronic databases were used for the systematic search from their conception to 19/10/2021: Pubmed, Web of Science, Embase, Scopus, PEDro, The Cochrane Central Registry for Controlled Trials (CENTRAL) and SPORTDiscus. Three authors independently screened 1227 articles from 7 databases using a two-staged process to include 16 studies. The quality assessment tool for observational and cross-sectional studies was used for the risk of bias assessment. The authors extracted and summarised relevant outcomes from each study in table 1.
Results: Patients with LAS showed lower superior cerebellar peduncles (white matter microstructure) compared with healthy controls. CAI populations displayed an increased sensitivity of intermediate inhibitory neurons and a decreased sensitivity of excitatory neurons in the corticospinal pathway. They also found more variability in cortical activation in the superior parietal lobe, pre-and postcentral gyrus and the supplementary motor area with lower corticomotor excitability in several lower limb muscles in patients with CAI.
Conclusion: Whilst these findings may support the hypothesis of brain plasticity in patients with ligamentous ankle injuries, all studies were retrospective in nature and most used different measurement methods which makes direct comparisons difficult and limits the strength of evidence of this review. Future research should focus on the understanding of the underlying neurophysiological mechanisms.
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