Effects of the BalanCI on Working Memory and Balance in Children and Young Adults With Cochleovestibular Dysfunction

Objectives: This study aimed to: (1) determine the interaction between cognitive load and balance in children and young adults with bilateral cochleovestibular dysfunction who use bilateral cochlear implants (CIs) and (2) determine the effect of an auditory balance prosthesis (the BalanCI) on this interaction. Many (20 to 70%) children with sensorineural hearing loss experience some degree of vestibular loss, leading to poorer balance. Poor balance could have effects on cognitive resource allocation which might be alleviated by the BalanCI as it translates head-referenced cues into electrical pulses delivered through the CI. It is hypothesized that children and young adults with cochleovestibular dysfunction will demonstrate greater dual-task costs than typically-developing children during dual balance-cognition tasks, and that BalanCI use will improve performance on these tasks. Design: Study participants were 15 typically-developing children (control group: mean age +/- SD = 13.6 +/- 2.75 years, 6 females) and 10 children and young adults who use bilateral CIs and have vestibular dysfunction (CI-V group: mean age +/- SD=20.6 +/- 5.36 years, 7 females). Participants completed two working memory tasks (backward auditory verbal digit span task and backward visuospatial dot matrix task) during three balance conditions: seated, standing in tandem stance with the BalanCI off, and standing in tandem stance with the BalanCI on. Working memory performance was quantified as total number of correct trials achieved. Postural stability was quantified as translational and rotational path length of motion capture markers worn on the head, upper body, pelvis, and feet, normalized by trial time. Results: Relative to the control group, children and young adults in the CI-V group exhibited poorer overall working memory across all balance conditions (p = 0.03), poorer translational postural stability (larger translational path length) during both verbal and visuospatial working memory tasks (p < 0.001), and poorer rotational stability (larger rotational path length) during the verbal working memory task (p = 0.026). The CI-V group also exhibited poorer translational (p = 0.004) and rotational (p < 0.001) postural stability during the backward verbal digit span task than backward visuospatial dot matrix task; BalanCI use reduced this stability difference between verbal and visuospatial working memory tasks for translational stability overall (p > 0.9), as well as for rotational stability during the maximum working memory span (highest load) participants achieved in each task (p = 0.91). Conclusions: Balance and working memory were impaired in the CI-V group compared with the control group. The BalanCI offered subtle improvements in stability in the CI-V group during a backward verbal working memory task, without producing a negative effect on working memory outcomes. This study supports the feasibility of the BalanCI as a balance prosthesis for individuals with cochleovestibular impairments.