Brain Mechanisms Explaining Postural Imbalance in Traumatic Brain Injury: A Systematic Review

Introduction: Persisting imbalance and falls in community-dwelling traumatic brain injury (TBI) survivors are linked to reduced long-term survival. However, a detailed understanding of the impact of TBI upon the brain mechanisms mediating imbalance is lacking. To understand the state of the art concerning the brain mechanisms mediating imbalance in TBI, we performed a systematic review of the literature.Methods: PubMed, Web of Science, and Scopus were searched and peer-reviewed research articles in humans, with any severity of TBI (mild, moderate, severe, or concussion), which linked a postural balance assessment (objective or subjective) with brain imaging (through computed tomography, T1-weighted imaging, functional magnetic resonance imaging [fMRI], resting-state fMRI, diffusion tensor imaging, magnetic resonance spectroscopy, single-photon emission computed tomography, electroencephalography, magnetoencephalography, near-infrared spectroscopy, and evoked potentials) were included. Out of 1940 articles, 60 were retrieved and screened, and 25 articles fulfilling inclusion criteria were included.Results: The most consistent finding was the link between imbalance and the cerebellum; however, the regions within the cerebellum were inconsistent.Discussion: The lack of consistent findings could reflect that imbalance in TBI is due to a widespread brain network dysfunction, as opposed to focal cortical damage. The inconsistency in the reported findings may also be attributed to heterogeneity of methodology, including data analytical techniques, small sample sizes, and choice of control groups. Future studies should include a detailed clinical phenotyping of vestibular function in TBI patients to account for the confounding effect of peripheral vestibular disorders on imbalance and brain imaging. Impact statement Postural imbalance after moderate-to-severe traumatic brain injury (TBI) is virtually ubiquitous. However, a detailed understanding of the brain mechanisms mediating imbalance in TBI is lacking. Thus, we synthesized the literature linking brain imaging with postural balance in TBI. We found that cerebellum was commonly linked with postural imbalance in TBI. However, these findings are limited due to inappropriate selection of participants, lack of peripheral vestibular assessments, inappropriate control groups, and selection bias due to regions of interest analysis in brain imaging. Based on our findings we provide recommendations for future studies investigating brain mechanisms of imbalance in TBI.