Postlingual Hearing Loss Research Articles

Cochlear implantation in deafness-dystonia-optic neuronopathy (DDON) syndrome

To report the results of the first known cochlear implantation in a patient with deafness-dystonia-optic neuronopathy (DDON) syndrome (Mohr-Tranebaerg syndrome, DFN-1). DDON syndrome is an X-linked condition characterized by postlingual sensorineural hearing loss in early childhood followed by dystonia, psychosis, and optic atrophy in adolescence and adulthood. The gene responsible for the condition maps to Xq22 adjacent to the gene causally related to X-linked agammaglobulinemia. The audiometric characteristics of DDON syndrome are typical of auditory neuropathy, with spiral ganglion cells being the suspected site of pathology. Performance following cochlear implantation in auditory neuropathy patients is variable and has yet to be reported in any patients with DDON syndrome. The reported case describes a male initially diagnosed with X-linked agammaglobulinemia due to recurrent infections. Speech, language and hearing were typical of a child in the first year of life; however profound hearing loss developed and cochlear implantation was performed at age 4. Following implantation, further genetic workup determined that the patient carries a deletion that includes BTK and DDP1/TIMM8a, consistent with the diagnosis of X-linked agammaglobulinemia and DDON syndrome. The patient's performance with the cochlear implant was marginal even after 2 years of use, with continued poor scores in standardized speech, language and audiometric tests. Additionally, his most-comfortable-level implant setting requires higher-than-normal current applied to the electrode array. This case report supports other studies showing that DDON syndrome results in an auditory neuropathy. Further investigation is required to determine the efficacy of cochlear implantation in this patient population. DDON syndrome should be considered in patients with X-linked agammaglobulinemia and hearing loss.

Aminoglycoside-induced deafness in leukemic patients: Cost-effectiveness of prevention by genetic testing

9014 Background: Aminoglycosides are highly-effective, inexpensive antimicrobials widely used in empirical combination therapy for fever in children with severe neutropenia, including patients receiving treatment for acute leukemia. Some genetically predisposed individuals are exquisitely sensitive to the cochleotoxic effects of these drugs, even when levels are within the therapeutic range. This genetic susceptibility is maternally inherited and caused by mutation of the MT-RNR1 gene encoding mitochondrial 12S rRNA at base position 1555, termed m.1555A>G. Methods: Retrospective analysis of m.1555A>G positive cases in the Regional Diagnostic laboratory to determine how many were revealed by aminoglycoside treatment for cancer treatment-related sepsis. Results: Three unrelated mutation positive individuals were identified in a two year period. All were children with acute lymphoblastic leukemia who experienced rapidly progressive hearing loss during their treatment. Two of the three children have a post-lingual hearing loss of sufficient severity to merit cochlear implantation. None had a significant family history of deafness. Conclusions: Initial estimates of the prevalence of the m.1555A>G mutation were based upon extrapolation back from its contribution to the cause of hearing loss amongst hearing-impaired people and were thought to be low. However, recent small studies of the prevalence of m.1555A>G in the general population suggest that prevalence is much higher than previously calculated (1 in 206 in New Zealand (n=206), 1 in 1,161 in Texas (n=1,161)) but that penetrance, at least in the absence of aminoglycosides, is low. Using estimates of the lifetime cost of pediatric cochlear implantation we suggest that screening for the m.1555A>G mutation at the time of diagnosis of leukemia would be cost effective and therefore suggest that all children diagnosed with leukemia should be screened for this mutation prior to receiving aminoglycoside therapy. No significant financial relationships to disclose.

Otosclerosis

1. To examine whether speech perception after implantation is correlated with the total duration of deafness, the duration of deafness in the implanted ear, or age at implantation. 2. To examine whether the rate of facial nerve stimulation postoperatively is correlated with the type of electrode used. Retrospective case note review. Tertiary referral center. Fifty-nine adults with profound postlingual sensorineural hearing loss due to otosclerosis. Cochlear implantation with the Nucleus device using either a straight (n = 35) or Contour (n = 29) electrode array. Speech perception scores for patients at 3, 6 and 12 months postimplantation were correlated against duration of deafness in the implanted ear, duration of total deafness, and age at implantation. Data on facial nerve stimulation rates postoperatively were collected. Implantation in the shortest deafened ear conferred an initial advantage for speech perception 3 months after surgery; however, this effect was lost by 6 months. There were no significant correlations between the duration of bilateral deafness and hearing outcomes. Age at implantation was negatively correlated with outcome at 3 months, but not at 6 and 12 months. Fourteen of 35 patients with straight electrodes and 0 of 24 patients with Contour electrodes experienced facial nerve stimulation during mapping sessions (p < 0.005, chi). Patients with otosclerosis are not disadvantaged in the long term by implantation in the longest deafened ear. Increasing age at implantation did not predict poorer outcomes. A perimodiolar design of electrode should be used in otosclerotic patients when possible to reduce the risk of facial nerve stimulation.

Analysis of genetic mutation in patients with nonsyndromic hearing loss received cochlear implant

To investigate the prevalence of mutations of the gap junction protein (GJB) 2 and mitochondria 12SrRNA in patients with nonsyndromic hearing loss who received cochlear implant. Genomic DNA was extracted from the peripheral blood samples obtained from 100 Chinese patients who had received cochlear implantation, 96 with prelingual hearing loss and 4 with postlingual hearing loss, all very severe. Sixteen of the 100 patients had the history of application of aminoglycosides, among which 12 were with prelingual hearing loss and 4 with postlingual hearing loss. PCR was performed and the products were sequenced by automated DNA sequencer. GJB2 mutations were detected in 34 of the 100 cochlear implant recipients (34%), all with prelingual hearing loss, among which 27 (27%) had 235delC mutation. Among the 16 patients who had used aminoglycosides, two had the mutation A1555G, and one carried the mitochondrial genetic mutation delT961Cn. Mutation of GJB2 gene is the major cause of deafness in cochlear implant recipients, with a high frequency of 235delC mutation. Mitochondria genetic mutation A1555G is the common form of mutation in postlingual deafness with a history of aminoglycoside injection.

The roles of connexin genes in sporadic hearing loss population

To investigate the roles of connexin genes in Chinese population. Peripheral blood samples were collected from 214 patients with hearing loss, 160 with sensorineural hearing loss (66 with prelingual hearing loss and 94 with postlingual hearing loss), 32 with auditory neuropathy, and 22 with enlarged vestibular aqueduct syndrome (EVAS), 110 males and 104 females, all from 14 provinces north of the Yangtze River, all of Han nationality, and 86 normal controls. PCR and sequencing of the PCR products were used to screen 3 connexin genes: GJB2, GJB3, and GJB6. The frequency of connexin gene sequence variant was 73.36% (157/214), higher than that of the controls (60.05%, 42/86). 34 of the 157 patients carried pathogenic mutations (15.89%). The frequency of 235delC deletion was 16.67% among patients with prelingual hearing loss (11/66). Six known polymorphisms and six new mutations were found in these patients. The pathogenic mutations of the patients with hearing loss are distributed quite differently between the patients and normal persons. The genetic variants GJB2 235delG and GJB6-Delta (GJB6/D13S1830) were not common. Relevant information is helpful in early diagnosis of hearing loss in Chinese population.

Survival and stimulation of neurite outgrowth in a serum-free culture of spiral ganglion neurons from adult mice

We have developed a reliable protocol for the serum-free dissociation and culture of spiral ganglion neurons from adult mice, an important animal model for patients with post-lingual hearing loss. Pilot experiments indicated that the viability of spiral ganglion cells in vitro depended critically on the use of Hibernate medium with B27 supplement. With an optimized protocol, we obtained 2 × 10 3 neurons immediately after dissociation, or about one-fifth of those present in the intact spiral ganglion. After four days in culture, 4% of the seeded neurons survived without any exogenous growth factors other than insulin. This yield was highly reproducible in five independent experiments and enabled us to measure systematically the numbers and lengths of the regenerating neurites. Furthermore, the survival rate compared well to the few published protocols for culturing adult spiral ganglion neurons from other species. Enhanced survival and neurite outgrowth upon the addition of brain-derived neurotrophic factor and leukemia inhibitory factor demonstrated that both are potent stimulants for damaged spiral ganglion neurons in adults. This responsiveness to exogenous growth factors suggested that our culture protocol will facilitate the screening of molecular compounds as potential treatments for sensorineural hearing loss.

Functional characterization of a novel Cx26 (T55N) mutation associated to non-syndromic hearing loss

Mutations of the GJB2 gene, encoding connexin 26, are the most common cause of hereditary congenital hearing loss in many countries and account for up to 50% of cases of autosomal-recessive non-syndromic deafness. By contrast, only a few GJB2 mutations have been reported to cause an autosomal-dominant form of non-syndromic deafness. Here, we report a family from Southern Italy affected by non-syndromic autosomal dominant post-lingual hearing loss, due to a novel missense mutation in the GJB2 gene, a threonine to asparagine amino acid substitution at codon 55 (T55N). Functional studies indicated that the mutation T55N produces a protein that, although expressed to levels similar to those of the wt counterpart, is deeply impaired in its intracellular trafficking and fails to reach the plasma membrane. The mutation T55N is located at the apex of the first extracellular loop of the protein, a region suggested to play a role in protein targeting and a site for other two mutations, G59A and D66H, causing dominant forms of deafness.

Cochlear Implant Outcome Is Not Influenced by the Choice of Ear

This study tested the hypothesis that patients with residual hearing in the nonimplanted ear had the same cochlear implant benefit whether the implanted ear had profound or severe hearing loss. A retrospective chart review of adult cochlear implant recipients with postlingual hearing loss. Patients were categorized according to the pure-tone average of the implanted and contralateral ears as (a) bilateral profound, (b) severe-profound, and (c) bilateral severe. The results of a test battery of spoken language measures were compared among patients belonging to these hearing categories at 6, 12, and 24 months after surgery, using a t-test and multivariate regression analyses. The presence of residual hearing in one or both ears was associated with significantly higher postoperative speech perception scores compared with participants with bilateral profound hearing loss. Among participants with similar amounts of residual hearing in the nonimplanted ear, however, there was no difference in speech recognition scores between those with profound and those with severe hearing loss in the implanted ear. Among participants with asymmetric hearing loss, there is no additional benefit to implanting the better-hearing ear that can be preserved for use with a hearing aid for better speech understanding in noise and sound localization. These results suggest that the additional benefit received by patients with residual hearing is mediated by trophic effects on crossed pathways in the central nervous system and is independent of the preoperative functional status of the implanted ear.

Evaluation of speech perception in noise in cochlear implanted adults

SummaryAim: to evaluate the effects of different signal-to-noise ratios on speech recognition obtained by the use of cochlear implant (CI); to compare the speech recognition in noise with different types of multichannel cochlear implants (CIs) and to evaluate the degree of difficulty for speech understanding in noise in daily life situations. Study design: cohort transversal. Material and Method: Forty adults with post-lingual hearing loss implanted with Nucleus 22, Nucleus 24, Combi 40, Combi 40+ and Clarion. We evaluated the recognition for CPA sentences in quiet and in S/N +15, +10 and +5 dB. We also applied the Social Hearing Handicap Index (SHHI) questionnaire for self-assessment in daily life. Results and Conclusion: All the implanted adults presented a significant reduction in the scores for sentences recognition as the S/N decreased. The medians´ curve for sentence recognition reached 50% in the signal-to-noise ratio of +10 dB. There was no statistically significant difference in sentences’ recognition scores and difficulty scores obtained with the SHHI, for all types of implants. The difficulties of implanted adults were rare in quiet and occasional in noisy situations according to SHHI questionnaire.

Deafness due to A1555G mitochondrial mutation without use of aminoglycoside.

The objective was to clarify the characteristics of deafness associated with the A1555G mutation within mitochondrial 12S ribosomal RNA gene in the absence of aminoglycoside exposure. Clinical and genetic studies in family members with the A1555G mitochondrial mutation were performed. The subjects were 123 maternally related members of a large Japanese family with the A1555G mutation. All subjects had no previous history of exposure to aminoglycosides. Hearing disability and handicap, tinnitus, and medical histories were analyzed by interviews in all of the subjects, genetic testing was performed in 41 subjects, and pure-tone audiometry was conducted in 26 subjects with hearing disability and handicap. The A1555G mutation was detected in a homoplasmic form (meaning that all the mitochondrial DNA carries the mutation) in all 41 subjects who were screened. The risk for developing postlingual hearing loss was likely to be much higher in the present subjects than in the general population. Both the severity and age at onset of the phenotype were similar in affected subjects within the same sibling group. Pure-tone averages were significantly worse in subjects who developed hearing loss before age 10 years than in those who developed hearing loss later. The present study demonstrated that the prevalence of deafness in individuals with the A1555G mitochondrial mutation was likely to be high even in the absence of aminoglycoside exposure and clearly showed the association of severe to profound hearing loss with the onset of hearing loss before age 10 years.

A novel dominant missense mutation--D179N--in the GJB2 gene (Connexin 26) associated with non-syndromic hearing loss.

Mutations of the GJB2 gene, encoding Connexin 26, are the most common cause of hereditary congenital hearing loss in many countries, and account for up to 50% of cases of autosomal-recessive non-syndromic deafness. By contrast, only a few GJB2 mutations have been reported to cause an autosomal-dominant form of non-syndromic deafness. We report on a family from southern Italy in whom dominant, non-syndromic, post-lingual hearing loss is associated with a novel missense mutation in the GJB2 gene. Direct sequencing of the gene showed a heterozygous G-->A transition at nucleotide 535, resulting in an aspartic acid to asparagine amino acid substitution at codon 179 (D179N). This mutation occurred in the second extracellular domain (EC2), which would seem to be very important for connexon-connexon interaction.

USH3A transcripts encode clarin-1, a four-transmembrane-domain protein with a possible role in sensory synapses.

Usher syndrome type 3 (USH3) is an autosomal recessive disorder characterised by the association of post-lingual progressive hearing loss, progressive visual loss due to retinitis pigmentosa and variable presence of vestibular dysfunction. Because the previously defined transcripts do not account for all USH3 cases, we performed further analysis and revealed the presence of additional exons embedded in longer human and mouse USH3A transcripts and three novel USH3A mutations. Expression of Ush3a transcripts was localised by whole mount in situ hybridisation to cochlear hair cells and spiral ganglion cells. The full length USH3A transcript encodes clarin-1, a four-transmembrane-domain protein, which defines a novel vertebrate-specific family of three paralogues. Limited sequence homology to stargazin, a cerebellar synapse four-transmembrane-domain protein, suggests a role for clarin-1 in hair cell and photoreceptor cell synapses, as well as a common pathophysiological pathway for different Usher syndromes.

Temporal Bone Histopathologic and Genetic Studies in Mohr-Tranebj??rg Syndrome (DFN-1)

To describe the temporal bone histopathologic and genetic abnormalities in a case of Mohr-Tranebjaerg syndrome. Mohr-Tranebjaezrg syndrome (DFN-1) is an X-linked, recessive, syndromic hearing loss, characterized by postlingual sensorineural hearing loss with onset in childhood, followed in adult life by progressive dystonia, spasticity, dysphagia, and optic atrophy. The syndrome is caused by mutations in the DDP (deafness/dystonia peptide) gene, which are thought to result in mitochondrial dysfunction with subsequent neurodegeneration. The temporal bone pathologic changes in this syndrome have not been reported. Hearing loss developed in the patient at age 4, blindness at age 48, and dystonia at age 57. Genetic studies on peripheral blood showed a l51delT mutation in his DDP gene. He died at age 66. The right temporal bone was subjected to light microscopy and polymerase chain reaction-based analysis of the DDP gene sequence. There was near complete loss of spiral ganglion cells with loss of nearly all peripheral and central processes. Only 1,765 spiral ganglion cells remained (8.5% of mean normal for age). The organ of Corti (including hair cells), stria vascularis, and spiral ligament were preserved. There was also a severe loss of Scarpa's ganglion cells with preservation of vestibular hair cells. The population of geniculate and trigeminal ganglion cells appeared normal. Sequence analysis from temporal bone DNA showed the 15ldelT DDP gene mutation. Sensorineural hearing loss in Mohr-Tranebjaerg syndrome is the result of a postnatal, progressive, severe auditory neuropathy.

Clinical and genetic features of nonsyndromic autosomal dominant sensorineural hearing loss: KCNQ4 is a gene responsible in Japanese.

Sixteen Japanese nonsyndromic autosomal dominant sensorineural hearing loss (ADSNHL) families were investigated clinically as well as genetically. Most families showed postlingual hearing loss. Although the severity of their hearing loss varied, most patients showed mild-moderate sensorineural hearing loss of a progressive nature. Mutation analysis was performed for the MYO7A, KCNQ4, and GJB3 genes, which are known to be responsible for autosomal dominant sensorineural hearing loss. The present study reports that a mutation in KCNQ4, a member of a large family of potassium channel genes, was responsible for ADSNHL in one Japanese family.

Novel mutations in the connexin 26 gene (GJB2) responsible for childhood deafness in the Japanese population

Mutations in the connexin 26 gene (GJB2), which encodes a gap-junction protein and is expressed in the inner ear, have been shown to be responsible for a major part of nonsyndromic hereditary prelingual (early-childhood) deafness in Caucasians. We have sequenced the GJB2 gene in 39 Japanese patients with prelingual deafness (group 1), 39 Japanese patients with postlingual progressive sensorineural hearing loss (group 2), and 63 Japanese individuals with normal hearing (group 3). Three novel mutations were identified in group 1: a single nucleotide deletion (235delC), a 16-bp deletion (176-191 del (16)), and a nonsense mutation (Y136X) in five unrelated patients. The 235delC mutation was most frequently observed, accounting for seven alleles in 10 mutant alleles. Screening of 203 unrelated normal individuals for the three mutations indicated that the carrier frequency of the 235delC mutation was 2/203 in the Japanese population. No mutation was found in group-2 patients. We also identified two novel polymorphisms (E114G and I203T) as well as two previously reported polymorphisms (V27I andV37I). Genotyping with these four polymorphisms allowed normal Japanese alleles to be classified into seven haplotypes. All 235delC mutant alleles identified in four patients resided only on haplotype type 1. These findings indicate that GJB2 mutations are also responsible for prelingual deafness in Japan.

Autosomal dominant nonsyndromic hearing impairment.

Nearly all genes that have been localized for autosomal dominantly inherited hearing impairment are characterized by postlingual hearing loss that is progressive in nature. This auditory phenotype is in contrast to that of genes localized for autosomal recessive hearing impairment, which generally cause nonprogressive severe-to-profound or profound prelingual hearing loss. In most cases, extended pedigrees have been used to localize autosomal dominant deafness genes, To date, 22 autosomal dominant loci have been mapped, and 10 of these genes have been cloned. The functions of these deafness-causing genes are diverse and include transcription factors, extracellular matrix components, ion channels, cytoskeletal components, and unknown functions. Interesting findings include the unexpected expression pattern of some of these genes and the discovery that in some genes, allele variants can cause either isolated hearing loss or syndromic deafness. The greatest challenge for future research will be identifying additional deafness-causing genes and elucidating their function in the inner ear. Am. J. Med. Genet. (Semin. Med. Genet.) 89:167-174, 1999. @ 2000 Wiley-Liss, Inc.

Autosomal dominant nonsyndromic hearing impairment

Nearly all genes that have been localized for autosomal dominantly inherited hearing impairment are characterized by postlingual hearing loss that is progressive in nature. This auditory phenotype is in contrast to that of genes localized for autosomal recessive hearing impairment, which generally cause nonprogressive severe-to-profound or profound prelingual hearing loss. In most cases, extended pedigrees have been used to localize autosomal dominant deafness genes, To date, 22 autosomal dominant loci have been mapped, and 10 of these genes have been cloned. The functions of these deafness-causing genes are diverse and include transcription factors, extracellular matrix components, ion channels, cytoskeletal components, and unknown functions. Interesting findings include the unexpected expression pattern of some of these genes and the discovery that in some genes, allele variants can cause either isolated hearing loss or syndromic deafness. The greatest challenge for future research will be identifying additional deafness-causing genes and elucidating their function in the inner ear. Am. J. Med. Genet. (Semin. Med. Genet.) 89:167–174, 1999. @ 2000 Wiley-Liss, Inc.

A gene for non-syndromic autosomal dominant progressive postlingual sensorineural hearing loss maps to chromosome 14q12-13.

We report a novel locus responsible for postlingual progressive sensorineural hearing loss (designated DFNA9) that maps to chromosome 14q12-13. A large kindred with autosomal dominant transmission of non-syndromic hearing loss was clinically studied. Hearing in affected individuals deteriorated at approximately 20 years of age and progressed to anacusis in the fifth decade. A random genome-wide search using polymorphic short tandem repeats demonstrated linkage with D14S121 (maximum two point LOD score = 6.19, theta = 0). Haplotype analysis of recombination events defined a 9 cM disease interval, between D14S252 and D14S49.

Analysis of View Angle Used in Speechreading Training of Sentences

This study examines the effects of sentence perception across three speaker viewing angles: front view (0°), quarter view (45°), and side view (90°). The performance of a female adult with postlingual hearing loss was measured for accuracy at each angle. The present study used a single-subject, alternating treatment design where three treatment angles were randomly presented in every session. The percentage accuracy levels for each session were compared to determine the most effective treatment viewing angle of the speaker. The results indicated that the side-view angle was most effective, as the percentage gain of improvement was greatest in combination with the consistent upward trend of the data points across treatment sessions. The performance at front-view and quarter-view angles was also successful. The results of this preliminary effort indicate the value of treatment for visual sentence perception at all three angles, including the nontraditionally targeted side view.

The UCH/RNID cochlear implant programme: patient selection.

After an initial postal questionnaire, patients undergo a series of tests and assessments designed to establish their suitability for implantation. The following criteria should be met: Total or profound post-lingual hearing loss. Sufficient age to give informed consent. General good health. Psychological stability. Unable to benefit from hearing aids. Free from middle ear or mastoid disease. Detailed medical, audiometric, vestibular and psychological investigations are performed, as well as acute electrical stimulation of the cochlea, and a hearing aid trial in those subjects with some measurable hearing. Fifty-two applicants have so far been assessed and of these 14 have been found to be suitable for implantation and seven have received implants.