Hearing Function in Spinal and Bulbar Muscular Atrophy (SBMA): A Case Control Study From a Tertiary Referral Center

Background: Expanding on earlier findings of auditory involvement from two small-scale studies, we conducted a comprehensive evaluation of hearing levels in a larger cohort of SBMA patients. Methods: Thirty-six SBMA patients and 36 age-matched male controls without risk factors for hearing loss underwent a comprehensive audiological assessment, including pure-tone audiometry at 250, 500, 1000, 2000, 4000, and 8000 Hz frequencies, using both air and bone conduction. The pure-tone average (PTA) was calculated as the mean threshold at 500, 1000, 2000, and 4000 Hz. A correlation analysis was performed to evaluate the relationship between patients' audiological features and clinical characteristics, including motor disability, as measured by the SBMA functional rating scale (SBMAFRS) and the 6-min walk test (6MWT). Results: PTA values were significantly higher in SBMA patients compared to healthy controls (Mann–Whitney U test, p = 0.0005, and p = 0.0001 for the right and left side, respectively), even when analysis was restricted to the 19 SBMA patients without risk factors for hearing loss (Mann–Whitney U test, p = 0.0148 and p = 0.0243 for the right and left ear, respectively). In the latter group, the hearing thresholds of each individual frequency were significantly higher than in controls, except for the intermediate frequencies (2000 Hz on both sides and 1000 on the left one). Negative significant correlations were found between PTA values and both the CAG repeat number and 6MWT distances. Conversely, SBMAFRS scores were overall unrelated to PTA values. Conclusions: Our findings suggest a disease-specific hearing impairment in SBMA patients.