Abstract
There is limited research on sensory acuity i.e., ability to perceive external perturbations via body-sway during standing in individuals with a traumatic brain injury (TBI). It is unclear whether sensory acuity diminishes after a TBI and if it is a contributing factor to balance dysfunction. The objective of this investigation is to first objectively quantify the sensory acuity in terms of perturbation perception threshold (PPT) and determine if it is related to functional outcomes of static and dynamic balance. Ten individuals with chronic TBI and 11 age-matched healthy controls (HC) performed PPT assessments at 0.33, 0.5, and 1 Hz horizontal perturbations to the base of support in the anterior-posterior direction, and a battery of functional assessments of static and dynamic balance and mobility [Berg balance scale (BBS), timed-up and go (TUG) and 5-m (5MWT) and 10-m walk test (10MWT)]. A psychophysical approach based on Single Interval Adjustment Matrix Protocol (SIAM), i.e., a yes-no task, was used to quantify the multi-sensory thresholds of perceived external perturbations to calculate PPT. A mixed-design analysis of variance (ANOVA) and post-hoc analyses were performed using independent and paired t-tests to evaluate within and between-group differences. Pearson correlation was computed to determine the relationship between the PPT and functional measures. The PPT values were significantly higher for the TBI group (0.33 Hz: 2.97 ± 1.0, 0.5 Hz: 2.39 ± 0.7, 1 Hz: 1.22 ± 0.4) compared to the HC group (0.33 Hz: 1.03 ± 0.6, 0.5 Hz: 0.89 ± 0.4, 1 Hz: 0.42 ± 0.2) for all three perturbation frequencies (p < 0.006 post Bonferroni correction). For the TBI group, the PPT for 1 Hz perturbations showed significant correlation with the functional measures of balance (BBS: r = −0.66, p = 0.037; TUG: r = 0.78, p = 0.008; 5MWT: r = 0.67, p = 0.034, 10MWT: r = 0.76, p = 0.012). These findings demonstrate that individuals with TBI have diminished sensory acuity during standing which may be linked to impaired balance function after TBI.
Highlights
Balance control is regulated within the central nervous system by the complex integration of visual, vestibular, and somatosensory pathways and motor control (Hillier et al, 1997; Greenwald et al, 2001)
The outcome measure of sensory acuity can serve as a novel marker of balance function which goes beyond biomechanical and functional outcomes and may provide added information to develop rehabilitation programs aimed at improving balance and reducing falls in individuals with Traumatic brain injury (TBI)
perception threshold (PPT) computed for 0.33 Hz showed the highest variability while 1 Hz perturbations showed the lowest variability based on the standard deviations
Summary
Balance control is regulated within the central nervous system by the complex integration of visual, vestibular, and somatosensory pathways and motor control (Hillier et al, 1997; Greenwald et al, 2001). Impairments to sensory pathways (Fino et al, 2017) and their integration (Peterka et al, 2018) to facilitate perception of bodyenvironment interaction can lead to poor understanding of the surroundings, impaired balance and a greater risk of falls after TBI. In the domain of perception and balance, sensory acuity, i.e., the ability to detect body-sway during external perturbations (Fitzpatrick and McCloskey, 1994; Richerson et al, 2003), could stem from impaired sensory integration. An objective assessment of the sensory acuity, i.e., the ability to perceive external perturbations, is necessary to accurately detect, quantify, and treat sensory integration deficits that could lead to poor detection of body sway and imbalance in dynamic environment.
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