Hearing Loss

Authored by 17 international researchers and research teams, the book provides up-to-date insights on topics in five different research areas related to normal hearing and deafness. Techniques for assessment of hearing and the appropriateness of the Mongolian gerbil as a model for age-dependent hearing loss in humans are presented. Parental attitudes to childhood deafness and role of early intervention for better treatment of hearing loss are also discussed. Comprehensive details are provided on the role of different environmental insults including injuries in causing deafness. Additionally, many genes involved in hearing loss are reviewed and the genetics of recessively inherited moderate to severe and progressive deafness is covered for the first time. The book also details established and evolving therapies for treatment of deafness

Cellular and Deafness Mechanisms Underlying Connexin Mutation-Induced Hearing Loss - A Common Hereditary Deafness

Hearing loss due to mutations in the connexin gene family, which encodes gap junctional proteins, is a common form of hereditary deafness. In particular, connexin 26 (Cx26, GJB2) mutations are responsible for ~50% of non-syndromic hearing loss, which is the highest incidence of genetic disease. In the clinic, Cx26 mutations cause various auditory phenotypes ranging from profound congenital deafness at birth to mild, progressive hearing loss in late childhood. Recent experiments demonstrate that congenital deafness mainly results from cochlear developmental disorders rather than hair cell degeneration and endocochlear potential reduction, while late-onset hearing loss results from reduction of active cochlear amplification, even though cochlear hair cells have no connexin expression. However, there is no apparent, demonstrable relationship between specific changes in connexin (channel) functions and the phenotypes of mutation-induced hearing loss. Moreover, new experiments further demonstrate that the hypothesized K+-recycling disruption is not a principal deafness mechanism for connexin deficiency induced hearing loss. Cx30 (GJB6), Cx29 (GJC3), Cx31 (GJB3), and Cx43 (GJA1) mutations can also cause hearing loss with distinct pathological changes in the cochlea. These new studies provide invaluable information about deafness mechanisms underlying connexin mutation-induced hearing loss and also provide important information for developing new protective and therapeutic strategies for this common deafness. However, the detailed cellular mechanisms underlying these pathological changes remain unclear. Also, little is known about specific mutation-induced pathological changes in vivo and little information is available for humans. Such further studies are urgently required

Deafness and hearing loss in higher education

Hearing loss and deafness affect more than 5% of the world's population. Although hearing loss and deafness are invisible disabilities, they significantly impact individuals. In this chapter, I draw on my personal experiences as an academic with hearing loss and a researcher of ableism in academia to reflect on what it means to be hard of hearing, deaf and Deaf in higher education

Molecular diagnostics for congenital hearing loss including 15 deafness genes using a next generation sequencing platform

Background: Hereditary hearing loss (HL) can originate from mutations in one of many genes involved in the complex process of hearing. Identification of the genetic defects in patients is currently labor intensive and expensive. While screening with Sanger sequencing for GJB2 mutations is common, this is not the case for the other known deafness genes (> 60). Next generation sequencing technology (NGS) has the potential to be much more cost efficient. Published methods mainly use hybridization based target enrichment procedures that are time saving and efficient, but lead to loss in sensitivity. In this study we used a semi-automated PCR amplification and NGS in order to combine high sensitivity, speed and cost efficiency. Results: In this proof of concept study, we screened 15 autosomal recessive deafness genes in 5 patients with congenital genetic deafness. 646 specific primer pairs for all exons and most of the UTR of the 15 selected genes were designed using primerXL. Using patient specific identifiers, all amplicons were pooled and analyzed using the Roche 454 NGS technology. Three of these patients are members of families in which a region of interest has previously been characterized by linkage studies. In these, we were able to identify two new mutations in CDH23 and OTOF. For another patient, the etiology of deafness was unclear, and no causal mutation was found. In a fifth patient, included as a positive control, we could confirm a known mutation in TMC1. Conclusions: We have developed an assay that holds great promise as a tool for screening patients with familial autosomal recessive nonsyndromal hearing loss (ARNSHL). For the first time, an efficient, reliable and cost effective genetic test, based on PCR enrichment, for newborns with undiagnosed deafness is available

Labyrinthine window rupture as a cause of acute sensorineural hearing loss

Labyrinthine window rupture (LWR) is one cause of acute sensorineural hearing loss and need for early exploration is clear for good improved hearing. Acute sensorineural hearing loss of 60 dB or more treated from May 2006 to May 2010 were retrospectively analyzed. There were 21 ears of severe deafness, 18 ears of profound deafness, and 10 ears of total deafness. All patients were examined with temporal bone CT. Space-occupying lesions around the labyrinthine windows were suggestive images of LWR. Thirty-five ears were operated for LWR while 14 ears of SHL received conservative treatments. Fifty-seven percent of LWR improved 30 dB or more after sealing of both labyrinthine windows. Of the 15 markedly recovered ears, 14 ears were operated within 2 weeks from the onset. Of the five cured ears, four ears were operated within a week from the onset. As for the hearing prognosis of SHL, 88% of severe and profound deafness improved 30 dB or more but total deafness did not improve more than 30 dB. Exclusion of LWR from SHL and early surgical intervention in LWR will bring about good hearing prognosis to both LWR and SHL

Correlation between GJB2 mutations and audiological deficits: personal experience

Mutations in GJB2 gene are the most common cause of genetic deafness. More than 100 mutations have been described. The aim of this work is to describe the personal experience in genetic hearing loss, investigating the audiological and genetical characteristics of Cx26 deafness and correlating genotype and phenotype. We performed audiological and genetical evaluation in 154 patients affected by non-syndromic deafness of different degree. All patients showed a bilateral symmetrical sensorineural hearing loss. From the genetical analysis 127 probands resulted as negatives while 27 as positives (51.8% homozygous for 35 delG, 14.8% compound heterozygosis and 33.3% single mutation); 7.5% of patients had a mild deafness, 37% moderate, 33.3% severe and 22.2% profound. The c.35 delG mutation was detected in 66.6% of patients. Three mutations were found in compound heterozygosis with 35 delG, six different single mutations already described, and a new mutation S138G were also found. Correlation between genotype and phenotype confirmed the high variability of hearing loss

Newborn Genetic Screening for Hearing Impairment: A Preliminary Study at a Tertiary Center

Universal newborn hearing screening (UNHS) is of paramount importance for early identification and management of hearing impairment in children. However, infants with slight/mild, progressive, or late-onset hearing impairment might be missed in conventional UNHS. To investigate whether genetic screening for common deafness-associated mutations could assist in identifying these infants, 1017 consecutive newborns in a tertiary hospital were subjected to both newborn hearing screening using a two-step distortion-product otoacoustic emissions (DPOAE) screening and newborn genetic screening (NGS) for deafness. The NGS targeted 4 deafness-associated mutations commonly found in the Taiwanese population, including p.V37I (c.109G>A) and c.235delC of the GJB2 gene, c.919-2A>G of the SLC26A4 gene, and mitochondrial m.1555A>G of the 12S rRNA gene. The results of the NGS were then correlated to the results of the NHS. Of the 1017 newborns, 16 (1.6%) had unilateral DPOAE screening failure, and 22 (2.2%) had bilateral DPOAE screening failure. A total of 199 (19.6%) babies were found to have at least 1 mutated allele on the NGS for deafness, 11 (1.1%) of whom were homozygous for GJB2 p.V37I, 6 (0.6%) compound heterozygous for GJB2 p.V37I and c.235delC, and 1 (0.1%) homoplasmic for m.1555A>G, who may potentially have hearing loss. Among them, 3 babies, 5 babies, and 1 baby, respectively, passed the NHS at birth. Comprehensive audiological assessments in the 9 babies at 3 months identified 1 with slight hearing loss and 2 with mild hearing loss. NGS for common deafness-associated mutations may identify infants with slight/mild or potentially progressive hearing impairment, thus compensating for the inherent limitations of the conventional UNHS

The prevalence of self-reported hearing loss in Ireland. The prevalence of self-reported hearing loss in Munster

Background: Hearing loss can have a profound impact on individuals and their families. It can result in negative consequences on quality of life, interpersonal communication, educational attainment and employment opportunities. There is a clear deficit of epidemiological research on prevalence of hearing loss in Ireland. This study was completed on behalf of Deaf Enterprises through the Community Academic Research Links (CARL) programme in University College Cork (UCC). Research Aim: This research aims to describe the prevalence of self-reported hearing loss in Munster, Ireland. Research Objectives: To extract and descriptively present all information on persons who self-reported a hearing loss, the educational attainment and labour force participation of this population Methods: To extract and descriptively present all information on self-reported hearing loss data mined the Census 2011 and 2016, Irish Health Survey (IHS) 2015, and National Disability Survey (NDS) 2006. Results: The National figure of self- reported Deafness or Serious Hearing Impairment has risen from 92,060 in 2011 to just over 103,000 in the Census 2016. Munster has the second highest prevalence of self-reported Deafness or Serious Hearing Impairment of all provinces. Those who self-reported Deafness or a Serious Hearing Impairment in Ireland had the highest labour force participation rate and the lowest unemployment rate of all disabilities. Conclusions: The rising prevalence of hearing loss in Ireland is crucial to informing enablement organisations like Deaf Enterprises so that they can effectively plan and deliver services based on the need and profile skills of the Deaf and hard of hearing community in Munster

Suffering in Silence: The unmet needs of d/Deaf prisoners

For many, deafness is seen as simply being an inability to hear; a misfortunate affliction making ‘normal’ life difficult.1 However, in reality defining d/Deafness is much more complex than this, with medical conceptions of deafness differing significantly from those which are cultural. Medical definitions look at deafness as an impairment, measuring the level of such impairment on a spectrum according to the quietest sound that an individual is able to hear.2 The extent to which a person is medically deaf varies significantly from those whose hearing is only slightly impaired, to individuals who are hard of hearing (HoH), and finally to those who are severely deaf. For the purposes of this article, HoH refers to individuals with mild to moderate hearing loss who may have difficulty following speech without the use of hearing aids, and severely deaf includes those who have little or no functional hearing, who usually need to rely on lip reading even with hearing aids.