中国一家系凝血因子C同源物基因新突变携带者听力学及前庭功能特点

Audiological and vestibular evaluation of new coagulation factor C homology mutation carriers in a Chinese family

目的分析携带凝血因子 C 同源物(coagulation factor c homology,COCH)基因新突变的中国常染色体显性遗传非综合征型聋(autosomal dominant non-syndromic sensorineural hearing loss,DFNA)9家系成员的听力学及前庭功能特点。方法对家系成员进行纯音测听、听性脑干反应、耳蜗电图等听力学及计算机动态姿势描记、前庭诱发性肌源性电位、视眼动、前庭眼动等前庭功能检查。结果听力学检查提示该家系患者20～50岁出现以高频下降为主的进行性感音神经性聋,60～70岁进展为重至极重度全频听力损失。前庭功能检查提示随意抽取的家系中耳聋患者计算机动态姿势描记、视眼动、温度试验正常;前庭诱发性肌源性电位检查提示耳聋患者耳石功能异常;速度阶梯试验时间常数异常、正弦谐波试验增益和相位异常,提示耳聋患者水平半规管功能减弱。结论中国DFNA9家系的所有耳聋患者均无前庭功能损害的主诉,通过详尽的前庭功能检查提示位于 COCH 非胶原结构糖蛋白 A 型2结构域上的突变所导致的前庭功能损害明显轻于位于 LCCL 结构域上的突变。中国 DFNA9家系的临床资料分析首次表明 DFNA9存在基因型和表现型的相关性。

Objective To analyze the clinical features of audiological and vestibular function in a Chinese family with late onset autosomal dominant nonsyndromic sensorineural hearing loss. Methods Comprehensive audiological and vestibular evaluation including pure tone audiometry, auditory brainstem reponse （ 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. Results All 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. Conclusions The 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 DFNAg.