Audiovestibular findings in a branchio-oto syndrome patient with a SIX1 mutation

A reported mutation in SIX1 was identified in a patient with familial hearing loss (HL), a left preauricular pit, and bilateral enlarged vestibular aqueducts (EVA). Although the characteristic symptoms of EVA including fluctuating HL and repetitive vertigo were not seen in the patient, further studies are needed to clarify the association between EVA and such symptoms.

To study the audiovestibular functions, and to identify the causative gene in a patient with branchio-oto syndrome.

We enrolled a 30-year-old female in whom HL was pointed out at the age of 6 years. She visited our department at the age of 21 years, and had not experienced any progression of her HL, tinnitus, or vertigo. Pure-tone audiograms showed bilateral moderate mixed HL with no apparent progression during a 9-year follow-up period. Audiovestibular examinations included distortion product otoacoustic emissions (DPOAEs), electrocochleography (ECochG), and electronystagmography (ENG). Direct sequencing was utilized to screen for SIX1, EYA1, SLC26A4, GJB2, and mitochondrial DNA MTRNR1 including 1555 position.

The findings of DPOAEs, ECochG, and ENG indicated cochlear HL with no vestibular dysfunction. A previously reported mutation of a heterozygous c.386A > G (p.Y129C) in SIX1 was detected. No mutation was identified in EYA1, SLC26A4, GJB2, or MTRNR1.