RESUMO
The objective of the present work was to study specific features of the audiological phenotype and the prevalence of GJB2-related sensorineural hearing loss (SNHL) in the infants suffering acoustic disturbances. The study included 264 children with bilateral non-syndromic sensorineural loss of hearing diagnosed during the first year of life by means of detailed audiological examination that included tympanometry, registration of short-latency auditory action potentials (SLAAP), delayed evoked otoacoustic emission (DEOAE), distortion product-frequency otoacoustic emission (DPFOAE), and auditory brain-stem response (ABR). In addition, stationary acoustically evoked responses (SAER) were recorded in 38 children presenting with hearing impairment associated with GJB2-related sensorineural loss of hearing. The follow-up dynamic study involved 113 children subjected to repeated audiological examination. The study revealed the genotype with pathological mutations in 182 (69.0%) children including 171 (64.8%) ones with biallelic mutations and 11 (4.2%) with a single mutation (heterozygous genotype). Eighty two (31.0%) children had genotype without mutations. A total of 21 different mutations and 30 different genotypes were identified. Analysis of the family histories of the children showed that neither the absence of relatives suffering from hearing impairment nor the presence of risk factors of acquired hearing impairment excludes the possibility of GJB2-related sensorineural loss of hearing in the infants. Otoacoustic emission fails to be registered in the majority of the children with the altered genotype (87%) during the stay in the maternity house. Mutations in the GJB2 gene are most frequently diagnosed in the patients with the moderate, moderately severe, and severe loss of hearing. At the same time, almost half of the infants presenting with the mild loss of hearing were found to exhibit changes in the GJB2 gene. The thresholds of registration of short-latency auditory action potentials remain stable in 90.0% of the children presenting with GJB2-related sensorineural loss of hearing which makes it possible to choose the strategy of their rehabilitative treatment (the use of hearing aids or cochlear implantation) during the very first months of life and predict the favourable outcome of cochlear implantation and hearing aid measures. The results of the present work illustrate the importance and practical significance of genetic studies (GJB2 gene tresting) of the infants suffering sensorineural loss of hearing and other acoustic disturbances for the elucidation of etiology of these conditions, prognosis of the disease, and the choice of the strategy for its treatment.