OBJECTIVETo analyze the clinical features of audiological and vestibular function in a Chinese family with late onset autosomal dominant nonsyndromic sensorineural hearing loss.

METHODSComprehensive audiological and vestibular evaluation including pure tone audiometry, auditory brainstem response (ABR), electrocochleogram (EcochG), oculomotor testing, caloric tests, rotational testing, computerized dynamic posturography and vestibular evoked myogenic potentials (VEMP) were conducted to identify the hearing and vestibular impairment.

RESULTSAll affected family members shared sensorineural hearing loss with full penetrance starting between the second and fifth decade of life as a high frequency loss which progresses to a severe to profound loss at the sixth to seventh decade. The extensive vestibular evaluation indicated that all affected members performed normally in computerized dynamic posturography and caloric testing. Impairment of the saccular otolith in all of six affected members was suggested by results of the VEMP test. The velocity step test generated abnormal time constants and sinusoidal oscillation test generated abnormal gains and phase in affected members indicated that horizontal canal vestibular hyporeflexia in history. All affected subjects examined in this family showed completely normal ocular motor responses in oculomotor testing, including smooth pursuit, optokinetic nystagmus, gaze and saccade.

CONCLUSIONSThe predominant feature of the Chinese DFNA9 family was that all the affected subjects harboring COCH mutation in the vWFA2 domain didn't suffer the vestibular symptoms during their life time and comprehensive vestibular assessment revealed only subtle vestibular hypofunction in affected members of this family. There is a genotype-phenotype correlation in DFNA9.