Research paperVestibular function is associated with residual low-frequency hearing loss in patients with bi-allelic mutations in the SLC26A4 gene

- About half of DFNB4 patients with bi-allelic SLC26A4/pendrin mutations show unilateral vestibulopathy.
- Vestibular function in DFNB4 is not associated with specific SLC26A4/pendrin mutant alleles or vestibular size.
- Vestibular phenotype in DFNB4 is strongly correlated with a residual low frequency hearing level.

DFNB4 is non-syndromic, autosomal recessive type of hearing loss with an enlarged vestibular aqueduct (EVA) caused by mutations in SLC26A4/pendrin. Although the characteristics of hearing loss are well known in DFNB4, vestibular function remains inconclusive. We evaluated the vestibular function of 31 patients with bi-allelic mutations in SLC26A4/pendrin and analyzed genetic, radiological, and audiological correlations with vestibular function. In a caloric test, unilateral and bilateral vestibulopathies were detected in 45.2% and 6.4% of patients, respectively; however, only 22.6% had subjective vertigo symptoms. While vestibular phenotype was not significantly associated with specific mutations in genetic alleles or the sizes of the endolymphatic sac and vestibular aqueduct, a residual hearing threshold at a low frequency (500 Hz) was definitely correlated with vestibular function in DFNB4 (p = 0.005). These findings may indicate that vestibular function in DFNB4 deteriorates unilaterally in ears when hearing loss occurs. In conclusion, DFNB4 shows vestibular dysfunction, which is strongly linked to hearing loss at low frequencies without any allelic or anatomical predisposing factor.