Mutations of the GJB2 gene are a common cause of deafness, being found in 15-25% of cases of congenital deafness. Over 100 mutations are now recognised and may be associated with a hearing loss ranging from mild to profound. This paper describes the less-commonly reported effects of GJB2 mutations on the vestibular system. The study group consisted of 24 patients known to have biallelic GJB2 mutations, 23 underwent caloric testing and 36 ears of 21 patients underwent cervical VEMP testing (ears that had undergone cochlear implantation were excluded). A group of patients with normal-hearing ears were used as age-matched controls. Only two of 23 (8.7%) patients showed reduced caloric function, indicating largely normal lateral semicircular canal function in the GJB2 mutation group. In the VEMP test, 80% of the GJB2 mutations group (61% of ears) showed reduced function when compared to the controls, indicating reduced saccular function. Interestingly, no correlation was found between the hearing level and the vestibular function. No patients complained of balance disturbance, suggesting compensation in early life for the limited clinical manifestations of saccular dysfunction. This paper adds to the increasing knowledge base surrounding GJB2 mutations.

Balance function in GJB2 mutations.
Tsukada K, Fukuoka H, Usami S.
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Stuart Burrows

FRCS (ORL-HNS), Wellington Regional Hospital, Newtown, Wellington, New Zealand.

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