Abstract: Objective By detecting the common deafness genes in patients with severe to extremely severe sensorineural hearing loss in Nanjing, we aimed to analyze the spectrum and prevalence of the hot-deafness gene mutations among these patients. Moreover, we aimed to clarify the genetic etiology of deafness in patients with severe to extremely severe sensorineural hearing loss in Nanjing. Methods First, we obtained patient data from deafness etiology questionnaires, physical examination, high-resolution temporal bone computed tomography(CT), and clinical audiological examination. Thereafter, 2-4 mL of peripheral venous blood was collected from 128 patients with severe to extremely severe sensorineural hearing loss and the 21 common mutation sites in GJB2, GJB3, SLC26A4, mtDNA, and 12S rRNA genes were analyzed. Results Among the 128 patients, gene mutation in the analyzed sites were detected in 39 cases(30.47%, 39/128). Two patients showed double gene locus mutations, whereas 14 of them showed homozygous mutations. Thirty(23.44%, 30/128)patients were detected with GJB2 gene mutation. Among them, 18(14.06%, 18/128)patients had homozygous or compound heterozygous GJB2 gene mutations. The rate of 235delC mutation sites was 20.31%(26/128), that of the 299-300delAT mutation site was 4.69%(6/128), and that of the 176-191del mutation site was 3.91%(5/128). Ten(7.81%, 10/128)patients were detected with SLC26A4 gene mutation. Among them, 4(3.13%,4/128)patients were detected with homozygous or compound heterozygous SLC26A4 gene mutation. The rate of IVS7-2 A>G mutation was 7.03%. Mutations of mtDNA 12S rRNA and GJB3 genes were not found in the present study. High-resolution temporal bone CT revealed enlarged vestibular aqueduct in 11 patients, and 10 of them tested positive for SLC26A4 homozygous or heterozygous mutations. The concordance rate between genetic diagnosis and temporal bone CT was 90.91%(10/11). Conclusions GJB2 gene mutation was the most commonly observed mutation in patients with severe to extremely severe sensorineural hearing loss in Nanjing, and the most common mutation site was 235delC. SLC26A4 gene mutation was the second most commonly observed mutation, and the most common mutation site was IVS7-2 A>G. SLC26A4 gene mutation is often found in patients with enlarged vestibular aqueduct syndrome, and mutation in this gene is useful to diagnose the syndrome. However, temporal bone CT can be used to reduce the rate of missed diagnosis in patients with sensorineural hearing loss.

Key words: Sensorineural hearing loss, Gene mutation, Gene detection