[Follow-up research on hearing progression of GJB2 mutation associated hearing loss in children]

Objective: To analyze the auditory follow-up alteration of GJB2 associated hearing loss children. Method: Forty three children aged 0-5 years with homozygous or heterozygous mutations of gene attach to the Children' s Hearing Diagnostic Center of our hospital were enrolled in this study. Distortion product otoacoustic emissions and acoustic immittance, auditory brainstem response, auditory steady state response, acoustic impedance, pediatric behavior audiometry and other audiological tests were performed. The subjects had at least two audiology diagnosis results at different time; follow-up time was at least three months. According to the genotype, the subjects were divided into two groups: 23 cases(53.49%) in the truncating mutation/truncating mutation (T/T) group and 20 cases(46.51%) in the nontruncating mutation/truncating mutation (NT/T) group. Hearing levels of the first and last diagnoses and progression rate were compared between the two groups, and the progression value and progression rate were analyzed. Result: The average follow-up time was(19.63 ± 16.76) months. The frequency of c. 235delC (56.98%) in GJB2 gene mutations sites was highest in this group, followed by c. 109G> A (22.09%). The first diagnosis of hearing loss, T/T group was mainly severe(60.87%), NT/T group was mainly mild (50.00%); The degree of final hearing loss in the T/T group was mainly severe(50.00%) while the NT/T group was mainly mild(42.50%), and the T/T group was both heavier than the NT/T group. The difference was both statistically significant. Follow-up research on 43 cases(86 ears) showed that 3 cases(4 ears) developed hearing progression, 1 of them were bilateral progression, two was unilateral progression; the overall rate of progression was 4.65%(4/86), and the rate of progression in the T/T group was 2.17%(1/46) while the NT/T group was 7.50%(3/40). There was no significant difference between the two groups. The average progression of 4 ears was 11.25 dB HL, the average progression speed was 0.5 dB HL/month. Conclusion: This study showed that the degree of hearing loss of associated hearing loss children was mild to profound, and those with truncating mutations/truncating mutations were severer than those with nontruncating mutations/truncating mutations. Hearing progression was seen in both groups, it is suggested that children with GJB2 gene mutations hearing progression may occur during growth and development, therefore, they should be followed up regularly. .