Abstract
BackgroundMutations in SLC26A4 cause Pendred syndrome (hearing loss with goiter) or DFNB4 (non-syndromic hearing loss with inner ear malformation, such as enlarged vestibular aqueduct or Mondini deformity). The relationship between mutations in SLC26A4 and Mondini deformity without enlarged vestibular aqueduct has not been studied in any Chinese deaf population. The purpose of this study was to assess whether mutations in the SLC26A4 gene cause Mondini deformity without an enlarged vestibular aqueduct (isolated Mondini deformity) in a Chinese population.MethodsIn total, 144 patients with sensorineural hearing loss were included and subjected to high-resolution temporal bone CT. Among them, 28 patients with isolated Mondini dysplasia (MD group), 50 patients with enlarged vestibular aqueduct with Mondini dysplasia (EVA with MD group), 50 patients with enlarged vestibular aqueduct without Mondini dysplasia (EVA group), and 16 patients with other types of inner ear malformations (IEM group) were identified. The coding exons of SLC26A4 were analyzed in all subjects.ResultsDNA sequence analysis of SLC26A4 was performed in all 144 patients. In the different groups, the detection rate of the SLC26A4 mutation differed. In the isolated MD group, only one single allelic mutation in SLC26A4 was found in one patient (1/28, 3.6%). In the EVA with MD group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. Also, in the EVA group, biallelic and monoallelic SLC26A4 mutations were identified in 46 patients (46/50, 92.0%) and three patients (3/50, 6.0%), respectively. These percentages were identical to those in the EVA plus MD group. Only two patients carried monoallelic mutations of the SLC26A4 gene in the IEM group (2/16, 12.5%). There were significant differences in the frequency of SLC26A4 mutation among the groups (P < 0.001). The detection rate of SLC26A4 mutation in the isolated MD group was significantly lower than in the EVA group (with or without MD; P < 0.001), and there was no significant difference in the detection rate of SLC26A4 between the MD group and IEM group (P > 0.5).ConclusionAlthough mutations in the SLC26A4 gene were frequently found in Chinese EVA patients with and without MD, there was no evidence to show a relationship between isolated MD and the SLC26A4 gene in the Chinese population examined. Hearing impairment in patients with isolated MD may be caused by factors other than mutations in the SLC26A4 gene.
Highlights
Hearing impairment is the most common neurosensory disorder in humans with congenital or prelingual deafness, affecting about 1 in 300 to 1 in 1000 children [1,2,3]
In the Chinese deaf population, SLC26A4 was found to have a close relationship with the pathogenesis of DFNB4 [14,15], but no systematic study was applied to examine the role of SLC26A4 in the pathogenesis of isolated Mondini
Based on the image information in these 144 patients, isolated MD was identified in 28 patients (19.4%), EVA with MD was identified in 50 patients (34.7%), EVA without MD was identified in 50 patients (34.7%), and other types of inner ear malformations (IEMs) were identified in 16 patients (11.1%)
Summary
Hearing impairment is the most common neurosensory disorder in humans with congenital or prelingual deafness, affecting about 1 in 300 to 1 in 1000 children [1,2,3]. Mutations in the SLC26A4 gene are probably the second most common cause of inherited hearing loss, after GJB2 mutations, and are responsible for Pendred syndrome as well as DFNB4 (non-syndromic hearing loss with inner ear abnormalities, such as enlarged vestibular aqueduct (EVA) with or without Mondini dysplasia (MD)) [5,6]. A Mondini cochlea (isolated Mondini) occurs only when the two and a half turns of the cochlea are replaced by a single cavity in the apical region because of the absence of the interscalar septum [9,10,11] It is usually bilateral and frequently associated with other inner ear malformations (IEMs) such as cystic expansion of the vestibules and semicircular canal dysplasia. Mutations in SLC26A4 cause Pendred syndrome (hearing loss with goiter) or DFNB4 (non-syndromic hearing loss with inner ear malformation, such as enlarged vestibular aqueduct or Mondini deformity). The purpose of this study was to assess whether mutations in the SLC26A4 gene cause Mondini deformity without an enlarged vestibular aqueduct (isolated Mondini deformity) in a Chinese population
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