Sound localization in patients with bilateral vestibulopathy

Purpose The goal of this study was to evaluate if bilaterally (partially) absent vestibular function during static sound localization testing, would have a negative impact on sound localization skills. Therefore, this study compared horizontal static sound localization skills of normal-hearing patients with bilateral vestibulopathy (BV) and healthy controls. Methods Thirteen normal-hearing patients with BV and thirteen age-matched healthy controls were included. Sound localization skills were tested using seven loudspeakers in a frontal semicircle, ranging from - 90 degrees to + 90 degrees. Sound location accuracy was analyzed using the root-mean-square error (RMSE) and the mean absolute error (MAE). To evaluate the severity of the BV symptoms, the following questionnaires were used: Dizziness Handicap Inventory (DHI), Oscillopsia severity questionnaire (OSQ), 12-item Spatial, Speech, and Qualities Questionnaire (SSQ12), and Health Utilities Index Mark 3 (HUI3). Results The RMSE and MAE were significantly larger (worse) in the BV group than in the healthy control group, with respective median RMSE of 4.6 degrees and 0 degrees, and a median MAE of 0.7 degrees and 0 degrees. The subjective reporting of speech perception, spatial hearing, and quality of life only demonstrated a moderate correlation between DHI (positive correlation) and HUI total score (negative correlation), and localization scores. Conclusion Static sound localization skills of patients with BV were only mildly worse compared to healthy controls. However, this difference was very small and therefore most likely due to impaired cognitive function. The vestibular system does not seem to have a modulating role in sound localization during static conditions, and its impact is negligible in contrast to the impact of hearing impairment. Furthermore, the subjective reporting of speech perception, spatial hearing, and quality of life was not strongly correlated with localization scores.