Prediction of cochlear implant performance by genetic mutation: the spiral ganglion hypothesis.

The GJB2 gene is located on chromosome 13q12 and it encodes the connexin 26, a transmembrane protein involved in cell-cell attachment of almost all tissues. GJB2 mutations cause autosomal recessive (DFNB1) and sometimes dominant (DFNA3) non-syndromic sensorineural hearing loss. Moreover, it has been demonstrated that connexins are involved in regulation of growth and differentiation of epidermis and, in fact, GJB2 mutations have also been identified in syndromic disorders with hearing loss associated with various skin disease phenotypes. GJB2 mutations associated with skin disease are, in general, transmitted with a dominant inheritance pattern. Nonsyndromic deafness is caused prevalently by a loss-of-function, while literature evidences suggest for syndromic deafness a mechanism based on gain-of-function. The spectrum of skin manifestations associated with some mutations seems to have a very high phenotypic variability. Why some mutations can lead to widely varying cutaneous manifestations is poorly understood and in particular, the reason why the skin disease-deafness phenotypes differ from each other thus remains unclear. This review provides an overview of recent findings concerning pathogenesis of syndromic deafness imputable to GJB2 mutations with an emphasis on relevant clinical genotype-phenotype correlations. After describing connexin 26 fundamental characteristics, the most relevant and recent information about its known mutations involved in the syndromic forms causing hearing loss and skin problems are summarized. The possible effects of the mutations on channel expression and function are discussed.

GJB2 Gene Mutations in Syndromic Skin Diseases with Sensorineural Hearing Loss.

Prolyl 3-hydroxylase-1 null mice exhibit hearing impairment and abnormal morphology of the middle ear bone joints.

Long term speech perception after cochlear implant in pediatric patients with GJB2 mutations.

Introduction 
The contribution of Gap junction beta-2 protein (GJB2) to the genetic load of deafness and its mutation spectra vary among different ethnic groups.


Objective 
In this study, the mutation spectrum and audiologic features of patients with GJB2 mutations were evaluated with a specific focus on residual hearing.


Methods 
An initial cohort of 588 subjects from 304 families with varying degrees of hearing loss were collected at the otolaryngology clinics of Seoul National University Hospital and Seoul National University Bundang Hospital from September 2010 through January 2014. GJB2 sequencing was carried out for 130 probands with sporadic or autosomal recessive non syndromic hearing loss. The audiograms were evaluated in the GJB2 mutants.


Results 
Of the 130 subjects, 22 (16.9%) were found to carry at least one mutant allele of GJB2. The c.235delC mutation was shown to have the most common allele frequency (39.0%) among GJB2 mutations, followed by p.R143W (26.8%) and p.V37I (9.8%). Among those probands without the p.V37I allele in a trans configuration who showed some degree of residual hearing, the mean air conduction thresholds at 250 and 500 Hz were 57 dB HL and 77.8 dB HL, respectively. The c.235delC mutation showed a particularly wide spectrum of hearing loss, from mild to profound and significantly better hearing thresholds at 250 Hz and 2k Hz than in the non-p.V37I and non-235delC nonsyndromic hearing loss and deafness 1(DFNB1) subjects.


Conclusion 
Despite its reputation as the cause of severe to profound deafness, c.235delC, the most frequent DFNB1 mutation in our cohort, caused a wide range of hearing loss with some residual hearing in low frequencies. This finding can be of paramount help for prediction of low frequency hearing thresholds in very young DFNB1 patients and highlights the importance of soft surgery for cochlear implantation in these patients.

/pdf/residual-hearing-in-dfnb1-deafness-and-its-clinical-4z2gyfy7d7.pdf

Residual Hearing in DFNB1 Deafness and Its Clinical Implication in a Korean Population

Conclusion. The outcome of surgery depends on complexities of middle ear anomalies and definite diagnosis can only be achieved during exploratory tympanotomy. We must be aware that the pathology of the congenital ossicular anomalies is variable and careful surgery is needed for hearing improvement. Objective. This study aimed to investigate congenital ossicular malformation. Subjects and methods. Fifteen cases of ossicular anomalies without external ear malformation were studied. The anomaly of the incus-stapes complex was the most frequent. There were two cases of fused incudostapedial (IS) joint, which is an extremely rare occurrence. Case 1 was a 33-year-old man, in whom otosclerosis was suspected and exploratory tympanotomy was performed. The IS joint was fused, and the stapes was immobile. Small fenestra stapedectomy was performed. In case 2, a 52-year-old woman, otosclerosis was also suspected and exploratory tympanotomy was performed. The IS joint was fused and the incus was fixed. After the long p...

Involvement of the incudostapedial joint anomaly in conductive deafness.

The clinical features of patients with the homozygous 235delC and the compound-heterozygous Y136X/G45E of the GJB2 mutations (Connexin 26) in cochlear implant recipients.

Clinical Assessment of 15 Cases of Pediatric Neck Abscess

Cochlear implantation is a well-established treatment for total deafness. According to the increased number of cochlear implantation cases and the postoperative period, we have encountered various problems and complications. We describe a patient with cochlear destruction from repeated otitis media several years after cochlear implantation. She underwent cochlear implantation in the opposite ear. We assume that the uncontrolled infection led to a chronic state, thus causing cochlear destruction. We sometimes experience fungus-induced otitis media after cochlear implantation which is difficult to control. It is therefore important to control otitis media before cochlear implantation.

A Case of Cochlear Destruction Induced by Otitis Media after Cochlear Implantation

Change in vestibular function and vertigo after cochlear implantation

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