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Wu J, Chen J, Ding Z, Fan J, Wang Q, Dai P, Han D. Outcomes of cochlear implantation in 75 patients with auditory neuropathy. Front Neurosci 2023; 17:1281884. [PMID: 38027523 PMCID: PMC10679445 DOI: 10.3389/fnins.2023.1281884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 10/27/2023] [Indexed: 12/01/2023] Open
Abstract
Background Cochlear implantation (CI) outcomes in patients with auditory neuropathy (AN) are variable, which hampers patients' decisions on CI. Objective This study aims to assess the outcomes of CI in individuals diagnosed with AN and to examine the various factors that may influence the effectiveness of this intervention. Methods A total of 75 patients diagnosed with AN were included in the study. The hearing threshold, the score of categories of auditory performance (CAP), speech intelligibility rating (SIR), and speech audiometry were tested. Genetic testing was conducted by medical exome sequencing in 46 patients. Results After CI, the average aided hearing threshold for patients with prelingual and post-lingual onset was 38.25 ± 6.63 dB and 32.58 ± 9.26 dB, respectively; CAP score improved to 5.52 ± 1.64 (p < 0.001) and 6.00 ± 0.96 (p < 0.001), respectively; SIR score increased to 3.57 ± 1.22 (p < 0.001) and 4.15 ± 0.95 (p < 0.001), respectively. Maximum speech recognition ranged from 58 to 93% for prelingual onset patients and 43 to 98% for those with post-lingual onset. Speech outcomes of CI in cases with cochlear nerve (CN) deficiency were significantly poorer (p = 0.008). Molecular etiologies, including TWIST1, ACTG1, m.A7445G, and a copy-number variant (CNV) carrying ACTB, were related to AN here. Conclusion CI is a viable therapy option for patients with AN; CN deficiency might impact outcomes of CI.
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Affiliation(s)
| | | | | | | | | | - Pu Dai
- Key Lab of Hearing Impairment Science of Ministry of Education, Key Lab of Hearing Impairment Prevention and Treatment of Beijing, National Clinical Research Center for Otolaryngologic Diseases, College of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Chinese PLA Medical School, Beijing, China
| | - Dongyi Han
- Key Lab of Hearing Impairment Science of Ministry of Education, Key Lab of Hearing Impairment Prevention and Treatment of Beijing, National Clinical Research Center for Otolaryngologic Diseases, College of Otolaryngology Head and Neck Surgery, Chinese PLA General Hospital, Chinese PLA Medical School, Beijing, China
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Saidia AR, Ruel J, Bahloul A, Chaix B, Venail F, Wang J. Current Advances in Gene Therapies of Genetic Auditory Neuropathy Spectrum Disorder. J Clin Med 2023; 12:jcm12030738. [PMID: 36769387 PMCID: PMC9918155 DOI: 10.3390/jcm12030738] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/11/2023] [Accepted: 01/13/2023] [Indexed: 01/18/2023] Open
Abstract
Auditory neuropathy spectrum disorder (ANSD) refers to a range of hearing impairments characterized by an impaired transmission of sound from the cochlea to the brain. This defect can be due to a lesion or defect in the inner hair cell (IHC), IHC ribbon synapse (e.g., pre-synaptic release of glutamate), postsynaptic terminals of the spiral ganglion neurons, or demyelination and axonal loss within the auditory nerve. To date, the only clinical treatment options for ANSD are hearing aids and cochlear implantation. However, despite the advances in hearing-aid and cochlear-implant technologies, the quality of perceived sound still cannot match that of the normal ear. Recent advanced genetic diagnostics and clinical audiology made it possible to identify the precise site of a lesion and to characterize the specific disease mechanisms of ANSD, thus bringing renewed hope to the treatment or prevention of auditory neurodegeneration. Moreover, genetic routes involving the replacement or corrective editing of mutant sequences or defected genes to repair damaged cells for the future restoration of hearing in deaf people are showing promise. In this review, we provide an update on recent discoveries in the molecular pathophysiology of genetic lesions, auditory synaptopathy and neuropathy, and gene-therapy research towards hearing restoration in rodent models and in clinical trials.
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Affiliation(s)
- Anissa Rym Saidia
- Institute for Neurosciences of Montpellier (INM), University Montpellier, INSERM, 34295 Montpellier, France
| | - Jérôme Ruel
- Institute for Neurosciences of Montpellier (INM), University Montpellier, INSERM, 34295 Montpellier, France
- Cognitive Neuroscience Laboratory, Aix-Marseille University, CNRS, UMR 7291, 13331 Marseille, France
| | - Amel Bahloul
- Institute for Neurosciences of Montpellier (INM), University Montpellier, INSERM, 34295 Montpellier, France
| | - Benjamin Chaix
- Department of ENT and Head and Neck Surgery, University Hospital of Montpellier, 34295 Montpellier, France
| | - Frédéric Venail
- Institute for Neurosciences of Montpellier (INM), University Montpellier, INSERM, 34295 Montpellier, France
- Department of ENT and Head and Neck Surgery, University Hospital of Montpellier, 34295 Montpellier, France
| | - Jing Wang
- Institute for Neurosciences of Montpellier (INM), University Montpellier, INSERM, 34295 Montpellier, France
- Department of ENT and Head and Neck Surgery, University Hospital of Montpellier, 34295 Montpellier, France
- Correspondence: ; Tel.: +33-499-63-60-48
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Burdo S, Di Berardino F, Bruno G. Is auditory neuropathy an appropriate term? A systematic literature review on its aetiology and pathogenesis. ACTA OTORHINOLARYNGOLOGICA ITALICA 2021; 41:496-506. [PMID: 34825666 PMCID: PMC8686806 DOI: 10.14639/0392-100x-n0932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 05/15/2021] [Indexed: 11/23/2022]
Abstract
To clarify the aetio-pathogenesis of Auditory Neuropathy Spectrum Disorder (ANSD), a total of 845 papers were divided into four categories: Review, Audiology, Treatment and Aetiology. Aetiology was the topic analysed categorising papers as: Genetics, Histopathology, Imaging and Medical diseases. Isolated ANs were in relation to Otoferlin, Pejvakin and DIAPH3 deficiency, and the syndromes were mainly Charcot Marie Tooth, Friedreich Ataxia, mitochondrial disorders and those associated with optic neuropathies. In histopathology papers, important information was available from analyses on human premature newborns and on some syndromic neuropathies. From cochlear dysmorphism to cerebral tumours associated with ANs, these are described in what is identified as the Imaging area. Finally, the prevalent clinical pathology was bilirubinopathy, followed by diabetes. In conclusion, AN/ANSDs do not refer to a clear pathological condition, but to an instrumental pattern without any evidence of auditory nerve involvement, except in a few conditions. The terms AN/ANSD are misleading and should be avoided, including terms such as “synaptopathy” or “dis-synchrony”.
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Santarelli R, Scimemi P, La Morgia C, Cama E, del Castillo I, Carelli V. Electrocochleography in Auditory Neuropathy Related to Mutations in the OTOF or OPA1 Gene. Audiol Res 2021; 11:639-652. [PMID: 34940017 PMCID: PMC8698970 DOI: 10.3390/audiolres11040059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 11/18/2021] [Accepted: 11/19/2021] [Indexed: 11/16/2022] Open
Abstract
Auditory Neuropathy (AN) is characterized by disruption of temporal coding of acoustic signals in auditory nerve fibers resulting in alterations of auditory perceptions. Mutations in several genes have been associated to the most forms of AN. Underlying mechanisms include both pre-synaptic and post-synaptic damage involving inner hair cell (IHC) depolarization, neurotransmitter release, spike initiation in auditory nerve terminals, loss of auditory fibers and impaired conduction. In contrast, outer hair cell (OHC) activities (otoacoustic emissions [OAEs] and cochlear microphonic [CM]) are normal. Disordered synchrony of auditory nerve activity has been suggested as the basis of both the alterations of auditory brainstem responses (ABRs) and reduction of speech perception. We will review how electrocochleography (ECochG) recordings provide detailed information to help objectively define the sites of auditory neural dysfunction and their effect on receptor summating potential (SP) and neural compound action potential (CAP), the latter reflecting disorders of ribbon synapses and auditory nerve fibers.
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Affiliation(s)
- Rosamaria Santarelli
- Department of Neurosciences, University of Padova, Via Belzoni 160, 35121 Padova, Italy; (P.S.); (E.C.)
- Audiology Service, Santi Giovanni e Paolo Hospital, Campo Santi Giovanni e Paolo, Castello 6777, 30122 Venezia, Italy
- Correspondence:
| | - Pietro Scimemi
- Department of Neurosciences, University of Padova, Via Belzoni 160, 35121 Padova, Italy; (P.S.); (E.C.)
- Audiology Service, Santi Giovanni e Paolo Hospital, Campo Santi Giovanni e Paolo, Castello 6777, 30122 Venezia, Italy
| | - Chiara La Morgia
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy; (C.L.M.); (V.C.)
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
| | - Elona Cama
- Department of Neurosciences, University of Padova, Via Belzoni 160, 35121 Padova, Italy; (P.S.); (E.C.)
- Audiology Service, Santi Giovanni e Paolo Hospital, Campo Santi Giovanni e Paolo, Castello 6777, 30122 Venezia, Italy
| | - Ignacio del Castillo
- Servicio de Genética, Hospital Universitario Ramón y Cajal, IRYCIS, 28034 Madrid, Spain;
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), 28034 Madrid, Spain
| | - Valerio Carelli
- Department of Biomedical and Neuromotor Sciences (DIBINEM), University of Bologna, Via Ugo Foscolo 7, 40123 Bologna, Italy; (C.L.M.); (V.C.)
- IRCCS Institute of Neurological Sciences of Bologna, Bellaria Hospital, Via Altura 3, 40139 Bologna, Italy
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Zanin J, Dhollander T, Rance G, Yu L, Lan L, Wang H, Lou X, Connelly A, Nayagam B, Wang Q. Fiber-Specific Changes in White Matter Microstructure in Individuals With X-Linked Auditory Neuropathy. Ear Hear 2021; 41:1703-1714. [PMID: 33136644 DOI: 10.1097/aud.0000000000000890] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Auditory neuropathy (AN) is the term used to describe a group of hearing disorders, in which the hearing impairment occurs as a result of abnormal auditory nerve function. While our understanding of this condition has advanced significantly over recent years, the ability to determine the site of lesion and the extent of dysfunction in affected individuals remains a challenge. To this end, we investigated potential axonal degeneration in the white matter tracts of the brainstem in individuals with X-linked AN. We hypothesized that individuals with X-linked AN would show focal degeneration within the VIII nerve and/or auditory brainstem tracts, and the degree of degeneration would correlate with the extent of auditory perceptual impairment. DESIGN This was achieved using a higher-order diffusion magnetic resonance imaging (dMRI)-based quantitative measure called apparent fiber density as obtained from a technique called single-shell 3-tissue constrained spherical deconvolution and analyzed with the fixel-based analysis framework. Eleven subjects with genetically confirmed X-linked AN and 11 controls with normal hearing were assessed using behavioral and objective auditory measures. dMRI data were also collected for each participant. RESULTS Fixel-based analysis of the brainstem region showed that subjects with X-linked AN had significantly lower apparent fiber density in the VIII nerve compared with controls, consistent with axonal degeneration in this region. Subsequent analysis of the auditory brainstem tracts specifically showed that degeneration was also significant in these structures overall. The apparent fiber density findings were supported by objective measures of auditory function, such as auditory brainstem responses, electrocochleography, and otoacoustic emissions, which showed VIII nerve activity was severely disrupted in X-linked AN subjects while cochlear sensory hair cell function was relatively unaffected. Moreover, apparent fiber density results were significantly correlated with temporal processing ability (gap detection task) in affected subjects, suggesting that the degree of VIII nerve degeneration may impact the ability to resolve temporal aspects of an acoustic signal. Auditory assessments of sound detection, speech perception, and the processing of binaural cues were also significantly poorer in the X-linked AN group compared with the controls with normal hearing. CONCLUSIONS The results of this study suggest that the dMRI-based measure of apparent fiber density may provide a useful adjunct to existing auditory assessments in the characterization of the site of lesion and extent of dysfunction in individuals with AN. Additionally, the ability to determine the degree of degeneration has the potential to guide rehabilitation strategies in the future.
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Affiliation(s)
- Julien Zanin
- The HEARing Cooperative Research Centre (HEARing CRC), Melbourne, Victoria, Australia
- Department of Audiology and Speech Pathology, University of Melbourne, Parkville, Australia
| | - Thijs Dhollander
- Developmental Imaging, Murdoch Children's Research Institute, Melbourne, Victoria, Australia
| | - Gary Rance
- The HEARing Cooperative Research Centre (HEARing CRC), Melbourne, Victoria, Australia
- Department of Audiology and Speech Pathology, University of Melbourne, Parkville, Australia
| | - Lan Yu
- Department of Otorhinolaryngology, Head and Neck Surgery, Institute of Otolaryngology, Chinese People's Liberation Army General Hospital 301, Beijing, China
- China National Clinical Research Centre for Otolaryngologic Diseases, Chinese People's Liberation Army General Hospital 301, Beijing, China
| | - Lan Lan
- Department of Otorhinolaryngology, Head and Neck Surgery, Institute of Otolaryngology, Chinese People's Liberation Army General Hospital 301, Beijing, China
- China National Clinical Research Centre for Otolaryngologic Diseases, Chinese People's Liberation Army General Hospital 301, Beijing, China
| | - Hongyang Wang
- Department of Otorhinolaryngology, Head and Neck Surgery, Institute of Otolaryngology, Chinese People's Liberation Army General Hospital 301, Beijing, China
- China National Clinical Research Centre for Otolaryngologic Diseases, Chinese People's Liberation Army General Hospital 301, Beijing, China
| | - Xin Lou
- Department of Radiology, Chinese People's Liberation Army General Hospital 301, Beijing, China
| | - Alan Connelly
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
- The Florey Department of Neuroscience and Mental Health, University of Melbourne, Melbourne, Australia
| | - Bryony Nayagam
- Department of Audiology and Speech Pathology, University of Melbourne, Parkville, Australia
- These authors contributed equally to this work
| | - Qiuju Wang
- Department of Otorhinolaryngology, Head and Neck Surgery, Institute of Otolaryngology, Chinese People's Liberation Army General Hospital 301, Beijing, China
- China National Clinical Research Centre for Otolaryngologic Diseases, Chinese People's Liberation Army General Hospital 301, Beijing, China
- Key Lab of Hearing Impairment Science of Ministry of Education, Beijing, China
- These authors contributed equally to this work
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Leonhard L, Brewer K, Roche J. Adult Onset Bilateral Cochlear Nerve Atrophy and Cochlear Implantation: A Case Report and Review of the Literature. Ann Otol Rhinol Laryngol 2021; 131:322-325. [PMID: 34041922 DOI: 10.1177/00034894211019518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To describe a case of idiopathic bilateral cochlear nerve atrophy acquired in adulthood. PATIENT A 75-year-old male with acquired bilateral cochlear nerve atrophy. INTERVENTION(S) Unilateral cochlear implantation. MAIN OUTCOME AND RESULTS Description of a patient with acquired bilateral cochlear nerve atrophy diagnosed at the age of 75. The patient had normal hearing and no communication deficits until the age of 66. At this point, the patient demonstrated a slight asymmetric hearing loss, which progressed to severe sensorineural hearing loss. Due to the resulting communication deficit, cochlear device implantation candidacy was pursued. Pre-operative magnetic resonance imaging (MRI) showed severe atrophy versus absence of the cochlear nerves bilaterally. After careful counseling regarding the expected communication outcomes given the MRI findings, the patient underwent left-sided cochlear implantation. The patient gained sound awareness, but no additional communication benefit compared to pre-operative baseline abilities. CONCLUSION Cochlear nerve deficiency is a known finding in certain cases of congenital and acquired hearing loss, but no cases of idiopathic adult-onset bilateral nerve atrophy have been reported. Without MR imaging, the clinically significant finding would not have been identified. Thus, MRI is advantageous when compared with other imaging modalities in patients with progressive sensorineural hearing loss and enables improved patient counseling regarding expected auditory and communication outcomes.
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Affiliation(s)
- Lucas Leonhard
- Division of Otolaryngology, Department of Surgery, The University of Wisconsin School of Medicine and Public Health, The University of Wisconsin-Madison
| | | | - Joseph Roche
- Division of Otolaryngology, Department of Surgery, The University of Wisconsin School of Medicine and Public Health, The University of Wisconsin-Madison
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Mitochondrial Dysfunction and Therapeutic Targets in Auditory Neuropathy. Neural Plast 2020; 2020:8843485. [PMID: 32908487 PMCID: PMC7474759 DOI: 10.1155/2020/8843485] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 05/27/2020] [Accepted: 07/11/2020] [Indexed: 11/30/2022] Open
Abstract
Sensorineural hearing loss (SNHL) becomes an inevitable worldwide public health issue, and deafness treatment is urgently imperative; yet their current curative therapy is limited. Auditory neuropathies (AN) were proved to play a substantial role in SNHL recently, and spiral ganglion neuron (SGN) dysfunction is a dominant pathogenesis of AN. Auditory pathway is a high energy consumption system, and SGNs required sufficient mitochondria. Mitochondria are known treatment target of SNHL, but mitochondrion mechanism and pathology in SGNs are not valued. Mitochondrial dysfunction and pharmacological therapy were studied in neurodegeneration, providing new insights in mitochondrion-targeted treatment of AN. In this review, we summarized mitochondrial biological functions related to SGNs and discussed interaction between mitochondrial dysfunction and AN, as well as existing mitochondrion treatment for SNHL. Pharmaceutical exploration to protect mitochondrion dysfunction is a feasible and effective therapeutics for AN.
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Auditory Neuropathy Spectrum Disorders: From Diagnosis to Treatment: Literature Review and Case Reports. J Clin Med 2020; 9:jcm9041074. [PMID: 32290039 PMCID: PMC7230308 DOI: 10.3390/jcm9041074] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 03/21/2020] [Accepted: 04/01/2020] [Indexed: 12/21/2022] Open
Abstract
Auditory neuropathy spectrum disorder (ANSD) refers to a range of hearing impairments characterized by deteriorated speech perception, despite relatively preserved pure-tone detection thresholds. Affected individuals usually present with abnormal auditory brainstem responses (ABRs), but normal otoacoustic emissions (OAEs). These electrophysiological characteristics have led to the hypothesis that ANSD may be caused by various dysfunctions at the cochlear inner hair cell (IHC) and spiral ganglion neuron (SGN) levels, while the activity of outer hair cells (OHCs) is preserved, resulting in discrepancies between pure-tone and speech comprehension thresholds. The exact prevalence of ANSD remains unknown; clinical findings show a large variability among subjects with hearing impairment ranging from mild to profound hearing loss. A wide range of prenatal and postnatal etiologies have been proposed. The study of genetics and of the implicated sites of lesion correlated with clinical findings have also led to a better understanding of the molecular mechanisms underlying the various forms of ANSD, and may guide clinicians in better screening, assessment and treatment of ANSD patients. Besides OAEs and ABRs, audiological assessment includes stapedial reflex measurements, supraliminal psychoacoustic tests, electrocochleography (ECochG), auditory steady-state responses (ASSRs) and cortical auditory evoked potentials (CAEPs). Hearing aids are indicated in the treatment of ANSD with mild to moderate hearing loss, whereas cochlear implantation is the first choice of treatment in case of profound hearing loss, especially in case of IHC presynaptic disorders, or in case of poor auditory outcomes with conventional hearing aids.
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Neighbors A, Moss T, Holloway L, Yu SH, Annese F, Skinner S, Saneto R, Steet R. Functional analysis of a novel mutation in the TIMM8A gene that causes deafness-dystonia-optic neuronopathy syndrome. Mol Genet Genomic Med 2020; 8:e1121. [PMID: 31903733 PMCID: PMC7057109 DOI: 10.1002/mgg3.1121] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 12/20/2019] [Accepted: 12/23/2019] [Indexed: 12/19/2022] Open
Abstract
Background The rare, X‐linked neurodegenerative disorder, Mohr–Tranebjaerg syndrome (also called deafness‐dystonia‐optic neuronopathy [DDON] syndrome), is caused by mutations in the TIMM8A gene. DDON syndrome is characterized by dystonia, early‐onset deafness, and various other neurological manifestations. The TIMM8A gene product localizes to the intermembrane space in mitochondria where it functions in the import of nuclear‐encoded proteins into the mitochondrial inner membrane. Frameshifts or premature stops represent the majority of mutations in TIMM8A that cause DDON syndrome. However, missense mutations have also been reported that result in loss of the TIMM8A gene product. Methods We report a novel TIMM8A variant in a patient with DDON syndrome that alters the initiation codon and employed functional analyses to determine the significance of the variant and its impact on mitochondrial morphology. Results The novel base change in the TIMM8A gene (c.1A>T, p.Met1Leu) results in no detectable protein and a reduction in TIMM8A transcript abundance. We observed a commensurate decrease in the steady‐state level of the Tim13 protein (the binding partner of Tim8a) but no decrease in TIMM13 transcripts. Patient fibroblasts exhibited elongation and/or increased fusion of mitochondria, consistent with prior reports. Conclusion This case expands the spectrum of mutations that cause DDON syndrome and demonstrates effects on mitochondrial morphology that are consistent with prior reports.
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Affiliation(s)
- Addison Neighbors
- Greenwood Genetic Center, Greenwood, SC, USA.,University of South Carolina School of Medicine, Columbia, SC, USA
| | - Tonya Moss
- Greenwood Genetic Center, Greenwood, SC, USA
| | | | - Seok-Ho Yu
- Greenwood Genetic Center, Greenwood, SC, USA
| | - Fran Annese
- Greenwood Genetic Center, Greenwood, SC, USA
| | | | - Russell Saneto
- Program for Mitochondrial Medicine and Metabolism, Division of Pediatric Neurology, Neuroscience Institute, Seattle's Children's Hospital, University of Washington, Seattle, WA, USA
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Bommakanti K, Iyer JS, Stankovic KM. Cochlear histopathology in human genetic hearing loss: State of the science and future prospects. Hear Res 2019; 382:107785. [PMID: 31493568 PMCID: PMC6778517 DOI: 10.1016/j.heares.2019.107785] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 07/30/2019] [Accepted: 08/15/2019] [Indexed: 12/22/2022]
Abstract
Sensorineural hearing loss (SNHL) is an extraordinarily common disability, affecting 466 million people across the globe. Half of these incidents are attributed to genetic mutations that disrupt the structure and function of the cochlea. The human cochlea's interior cannot be imaged or biopsied without damaging hearing; thus, everything known about the morphologic correlates of hereditary human deafness comes from histopathologic studies conducted in either cadaveric human temporal bone specimens or animal models of genetic deafness. The purpose of the present review is to a) summarize the findings from all published histopathologic studies conducted in human temporal bones with known SNHL-causing genetic mutations, and b) compare the reported phenotypes of human vs. mouse SNHL caused by the same genetic mutation. The fact that human temporal bone histopathologic analysis has been reported for only 22 of the nearly 200 identified deafness-causing genes suggests a great need for alternative and improved techniques for studying human hereditary deafness; in light of this, the present review concludes with a summary of promising future directions, specifically in the fields of high resolution cochlear imaging, intracochlear fluid biopsy, and gene therapy.
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Affiliation(s)
- Krishna Bommakanti
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA; Eaton Peabody Laboratories and Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, USA; University of California San Diego School of Medicine, San Diego, CA, USA
| | - Janani S Iyer
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA; Eaton Peabody Laboratories and Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, USA; Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, USA; Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA, USA
| | - Konstantina M Stankovic
- Department of Otolaryngology, Harvard Medical School, Boston, MA, USA; Eaton Peabody Laboratories and Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, USA; Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, USA; Harvard Program in Therapeutic Science, Harvard Medical School, Boston, MA, USA.
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Shearer AE, Hansen MR. Auditory synaptopathy, auditory neuropathy, and cochlear implantation. Laryngoscope Investig Otolaryngol 2019; 4:429-440. [PMID: 31453354 PMCID: PMC6703118 DOI: 10.1002/lio2.288] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 05/17/2019] [Accepted: 06/13/2019] [Indexed: 02/03/2023] Open
Abstract
Cochlear implantation has become the standard-of-care for adults and children with severe to profound hearing loss. There is growing evidence that qualitative as well as quantitative deficits in the auditory nerve may affect cochlear implant (CI) outcomes. Auditory neuropathy spectrum disorder (ANSD) is characterized by dysfunctional transmission of sound from the cochlea to the brain due to defective synaptic function or neural conduction. In this review, we examine the precise mechanisms of genetic lesions causing ANSD and the effect of these lesions on CI outcomes. Reviewed data show that individuals with lesions that primarily affect the cochlear sensory system and the synapse, which are bypassed by the CI, have optimal CI outcomes. Individuals with lesions that affect the auditory nerve show poor performance with CIs, likely because neural transmission of the electrical signal from the CI is affected. We put forth a nuanced molecular classification of ANSD that has implications for preoperative counseling for patients with this disorder prior to cochlear implantation. We propose that description of ANSD patients should be based on the molecular site of lesion typically derived from genetic evaluation (synaptopathy vs. neuropathy) as this has implications for expected CI outcomes. Improvements in our understanding of genetic site of lesions and their effects on CI function should lead to better CI outcomes, not just for individuals with auditory neuropathy, but all individuals with hearing loss.
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Affiliation(s)
- Aiden Eliot Shearer
- Department of Otolaryngology-Head and Neck Surgery University of Iowa Carver College of Medicine Iowa City Iowa U.S.A
| | - Marlan R Hansen
- Department of Otolaryngology-Head and Neck Surgery University of Iowa Carver College of Medicine Iowa City Iowa U.S.A.,Department of Neurosurgery University of Iowa Carver College of Medicine Iowa City Iowa U.S.A
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12
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Wang H, Wang L, Yang J, Yin L, Lan L, Li J, Zhang Q, Wang D, Guan J, Wang Q. Phenotype prediction of Mohr-Tranebjaerg syndrome (MTS) by genetic analysis and initial auditory neuropathy. BMC MEDICAL GENETICS 2019; 20:11. [PMID: 30634948 PMCID: PMC6330410 DOI: 10.1186/s12881-018-0741-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Accepted: 12/21/2018] [Indexed: 12/02/2022]
Abstract
Background Mohr-Tranebjaerg syndrome (MTS) is a rare X-linked recessive neurodegenerative disorder resulting in early-onset hearing impairment, gradual dystonia and optic atrophy. MTS is caused by variations in the nuclear TIMM8A gene, which is involved in mitochondrial transport of metabolites. This study aimed to identify the pathogenic gene variations in three Chinese families associated with predicted MTS with or without X-linked agammaglobulinaemia. Methods Otologic examinations, vestibular, neurological, optical and other clinical evaluations were conducted on the family members. Targeted genes capture combining next generation sequencing (NGS) was performed, and then Sanger sequencing was used to confirm the causative variation. Results A novel variation, c.232_233insCAAT, in TIMM8A was identified as the pathogenic variation in one Chinese family. This variation co-segregated with the most frequent phenotypic deafness and was absent in the 1000 Genomes Project, ExAC and 1751 ethnicity-matched controls. Clinically, otological examinations illustrated the typical postsynaptic auditory neuropathy for the proband without the symptoms of dystonia or optic atrophy. MRI demonstrated abnormal small cochlear symmetric nerves, while the vestibular function appeared to be less influenced. Furthermore, we found another two TIMM8A variations, the deletion c.133_135delGAG and a copy number variation (CNV) including the TIMM8A gene, in two independent case, when we performed NGS on an auditory neuropathy population. Conclusion We identified two novel variations in the TIMM8A gene (c.232_233insCAAT and c.133_135delGAG) and a CNV including the TIMM8A gene in three independent Chinese families with predicted MTS. To our knowledge, this is the first report of TIMM8A variations being identified in a Chinese population. Our results enrich the variation spectrum of TIMM8A and clinical heterogeneity of MTS. Genetic detection and diagnosis is a powerful tool for better understanding and managing syndromic hearing impairments, such as MTS, before they become full-blown. Electronic supplementary material The online version of this article (10.1186/s12881-018-0741-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Hongyang Wang
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China
| | - Li Wang
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China
| | - Ju Yang
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China
| | | | - Lan Lan
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China
| | - Jin Li
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China
| | - Qiujing Zhang
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China
| | - Dayong Wang
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China
| | - Jing Guan
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China.
| | - Qiuju Wang
- Institute of Otolaryngology, Chinese PLA General Hospital, Medical School of Chinese PLA, Beijing, 100853, China.
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Alzhrani F, Alhussini R, Hudeib R, Alkaff T, Islam T, Alsanosi A. The outcome of cochlear implantation among children with genetic syndromes. Eur Arch Otorhinolaryngol 2017; 275:365-369. [PMID: 29204917 DOI: 10.1007/s00405-017-4832-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/28/2017] [Indexed: 10/18/2022]
Abstract
OBJECTIVE To assess the outcome and efficacy of cochlear implantation in children with genetic syndromes. METHOD Study design: case-control study. SETTING A cochlear implantation tertiary referral center. PATIENTS All pediatric cochlear implantation recipients with Waardenburg syndrome, Usher syndrome, Dandy-Walker syndrome, or albinism. A control group was appropriately matched to the syndromic group with regard to age at implantation and duration of device use. INTERVENTION Cochlear implantation. MAIN OUTCOME MEASURES Subjects' auditory abilities, speech intelligibility, and pure tone thresholds were compared between the syndromic and non-syndromic group. RESULTS A total of 25 subjects (13 syndromic and 12 non-syndromic) participated in the study. Neither auditory ability nor speech intelligibility scores differed significantly by group. The final PTA of both the groups showed normal-to-mild hearing loss: 26 dB HL in the syndromic group and 23 dB HL for the control group. CONCLUSIONS Cochlear implant recipients with genetic syndromes achieved similar levels auditory perception and speech intelligibility as their peers with a genetic syndrome. The presence of any of the genetic syndromes described herein should not be a contraindication to cochlear implant provision, as it would have a positive impact on the patients' sensory perception and lifestyle.
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Affiliation(s)
- Farid Alzhrani
- King Abdullah Ear Specialist Center (KAESC), College of Medicine, King Saud University, PO Box 245, Riyadh, 11411, Saudi Arabia.
| | - Rayan Alhussini
- King Abdullah Ear Specialist Center (KAESC), College of Medicine, King Saud University, PO Box 245, Riyadh, 11411, Saudi Arabia
| | - Rawan Hudeib
- King Abdullah Ear Specialist Center (KAESC), College of Medicine, King Saud University, PO Box 245, Riyadh, 11411, Saudi Arabia
| | - Tuqa Alkaff
- College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Tahera Islam
- College of Medicine and Research Center, King Saud University, Riyadh, Saudi Arabia
| | - Abdulrahman Alsanosi
- King Abdullah Ear Specialist Center (KAESC), College of Medicine, King Saud University, PO Box 245, Riyadh, 11411, Saudi Arabia
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14
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Sagers JE, Landegger LD, Worthington S, Nadol JB, Stankovic KM. Human Cochlear Histopathology Reflects Clinical Signatures of Primary Neural Degeneration. Sci Rep 2017; 7:4884. [PMID: 28687782 PMCID: PMC5501826 DOI: 10.1038/s41598-017-04899-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 05/22/2017] [Indexed: 01/22/2023] Open
Abstract
Auditory neuropathy is a significant and understudied cause of human hearing loss, diagnosed in patients who demonstrate abnormal function of the cochlear nerve despite typical function of sensory cells. Because the human inner ear cannot be visualized during life, histopathological analysis of autopsy specimens is critical to understanding the cellular mechanisms underlying this pathology. Here we present statistical models of severe primary neuronal degeneration and its relationship to pure tone audiometric thresholds and word recognition scores in comparison to age-matched control patients, spanning every decade of life. Analysis of 30 ears from 23 patients shows that severe neuronal loss correlates with elevated audiometric thresholds and poor word recognition. For each ten percent increase in total neuronal loss, average thresholds across patients at each audiometric test frequency increase by 6.0 dB hearing level (HL). As neuronal loss increases, threshold elevation proceeds more rapidly in low audiometric test frequencies than in high frequencies. Pure tone average closely agrees with word recognition scores in the case of severe neural pathology. Histopathologic study of the human inner ear continues to emphasize the need for non- or minimally invasive clinical tools capable of establishing cellular-level diagnoses.
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Affiliation(s)
- Jessica E Sagers
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States.,Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, 02114, United States
| | - Lukas D Landegger
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States.,Department of Otolaryngology, Vienna General Hospital, Medical University of Vienna, Vienna, 1090, Austria.,Department of Otolaryngology, Harvard Medical School, Boston, MA, 02114, United States
| | - Steven Worthington
- Harvard Institute for Quantitative Social Science, Harvard University, Cambridge, MA, 02138, USA
| | - Joseph B Nadol
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States.,Department of Otolaryngology, Harvard Medical School, Boston, MA, 02114, United States
| | - Konstantina M Stankovic
- Eaton-Peabody Laboratories, Department of Otolaryngology, Massachusetts Eye and Ear, Boston, MA, 02114, United States. .,Program in Speech and Hearing Bioscience and Technology, Harvard Medical School, Boston, MA, 02114, United States. .,Department of Otolaryngology, Harvard Medical School, Boston, MA, 02114, United States.
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15
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Xq22.1 contiguous gene deletion syndrome of X-linked agammaglobulinemia and Mohr-Tranebjærg syndrome. Ann Allergy Asthma Immunol 2016; 116:578-9. [PMID: 27048950 DOI: 10.1016/j.anai.2016.03.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Revised: 03/10/2016] [Accepted: 03/14/2016] [Indexed: 11/24/2022]
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16
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Maison SF, Yin Y, Liberman LD, Liberman MC. Perinatal thiamine deficiency causes cochlear innervation abnormalities in mice. Hear Res 2016; 335:94-104. [PMID: 26944177 DOI: 10.1016/j.heares.2016.02.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 02/03/2016] [Accepted: 02/12/2016] [Indexed: 01/19/2023]
Abstract
Neonatal thiamine deficiency can cause auditory neuropathy in humans. To probe the underlying cochlear pathology, mice were maintained on a thiamine-free or low-thiamine diet during fetal development or early postnatal life. At postnatal ages from 18 days to 22 wks, cochlear function was tested and cochlear histopathology analyzed by plastic sections and cochlear epithelial whole-mounts immunostained for neuronal and synaptic markers. Although none of the thiamine-deprivation protocols resulted in any loss of hair cells or any obvious abnormalities in the non-sensory structures of the cochlear duct, all the experimental groups showed significant anomalies in the afferent or efferent innervation. Afferent synaptic counts in the inner and outer hair cell areas were reduced, as was the efferent innervation density in both the outer and inner hair cell areas. As expected for primary neural degeneration, the thresholds for distortion product otoacoustic emissions were not affected, and as expected for subtotal hair cell de-afferentation, the suprathreshold amplitudes of auditory brainstem responses were more affected than the response thresholds. We conclude that the auditory neuropathy from thiamine deprivation could be produced by loss of inner hair cell synapses.
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Affiliation(s)
- Stéphane F Maison
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA; Harvard Program in Speech and Hearing Bioscience and Technology, Boston MA, USA.
| | - Yanbo Yin
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA
| | - Leslie D Liberman
- Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA
| | - M Charles Liberman
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston MA, USA; Harvard Program in Speech and Hearing Bioscience and Technology, Boston MA, USA
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17
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Viana LM, O'Malley JT, Burgess BJ, Jones DD, Oliveira CACP, Santos F, Merchant SN, Liberman LD, Liberman MC. Cochlear neuropathy in human presbycusis: Confocal analysis of hidden hearing loss in post-mortem tissue. Hear Res 2015; 327:78-88. [PMID: 26002688 DOI: 10.1016/j.heares.2015.04.014] [Citation(s) in RCA: 267] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 04/03/2015] [Accepted: 04/28/2015] [Indexed: 11/29/2022]
Abstract
Recent animal work has suggested that cochlear synapses are more vulnerable than hair cells in both noise-induced and age-related hearing loss. This synaptopathy is invisible in conventional histopathological analysis, because cochlear nerve cell bodies in the spiral ganglion survive for years, and synaptic analysis requires special immunostaining or serial-section electron microscopy. Here, we show that the same quadruple-immunostaining protocols that allow synaptic counts, hair cell counts, neuronal counts and differentiation of afferent and efferent fibers in mouse can be applied to human temporal bones, when harvested within 9 h post-mortem and prepared as dissected whole mounts of the sensory epithelium and osseous spiral lamina. Quantitative analysis of five "normal" ears, aged 54-89 yrs, without any history of otologic disease, suggests that cochlear synaptopathy and the degeneration of cochlear nerve peripheral axons, despite a near-normal hair cell population, may be an important component of human presbycusis. Although primary cochlear nerve degeneration is not expected to affect audiometric thresholds, it may be key to problems with hearing in noise that are characteristic of declining hearing abilities in the aging ear.
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Affiliation(s)
- Lucas M Viana
- Faculty of Health Sciences, University of Brasilia, Brasilia, Distrito Federal, Brazil
| | | | - Barbara J Burgess
- Department of Otolaryngology, Massachusetts Eye and Ear, Boston MA, USA
| | - Dianne D Jones
- Department of Otolaryngology, Massachusetts Eye and Ear, Boston MA, USA
| | - Carlos A C P Oliveira
- Faculty of Health Sciences, University of Brasilia, Brasilia, Distrito Federal, Brazil
| | - Felipe Santos
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Department of Otolaryngology, Massachusetts Eye and Ear, Boston MA, USA
| | - Saumil N Merchant
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary, Boston MA, USA; Department of Otolaryngology, Massachusetts Eye and Ear, Boston MA, USA
| | - Leslie D Liberman
- Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary, Boston MA, USA; Department of Otolaryngology, Massachusetts Eye and Ear, Boston MA, USA
| | - M Charles Liberman
- Department of Otology and Laryngology, Harvard Medical School, Boston MA, USA; Eaton-Peabody Laboratories, Massachusetts Eye & Ear Infirmary, Boston MA, USA; Department of Otolaryngology, Massachusetts Eye and Ear, Boston MA, USA.
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18
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Abstract
Neural disorders of the auditory nerve are associated with particular disorders of auditory perceptions dependent on processing of acoustic temporal cues. These include: (1) speech perception; (2) localizing a sound's origin in space; and (3) identifying sounds in background noise. Auditory neuropathy (AN) is a consequence of: (1) presynaptic disorders affecting inner hair cell ribbon synapses; (2) postsynaptic disorders of auditory nerve dendrites; and (3) postsynaptic disorders of auditory nerve axons. The etiologies of these disorders are diverse, similar to other cranial or peripheral neuropathies. The pathologies cause attenuated and dyssynchronous auditory nerve discharges. Therapies and management of patients with AN are reviewed.
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Affiliation(s)
- Arnold Starr
- Departments of Neurology and Neurobiology, University of California, Irvine, CA, USA.
| | - Gary Rance
- School of Audiology, University of Melbourne, Melbourne, Australia
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19
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Nishimura K, Weichert RM, Liu W, Davis RL, Dabdoub A. Generation of induced neurons by direct reprogramming in the mammalian cochlea. Neuroscience 2014; 275:125-35. [PMID: 24928351 DOI: 10.1016/j.neuroscience.2014.05.067] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 04/15/2014] [Accepted: 05/14/2014] [Indexed: 01/27/2023]
Abstract
Primary auditory neurons (ANs) in the mammalian cochlea play a critical role in hearing as they transmit auditory information in the form of electrical signals from mechanosensory cochlear hair cells in the inner ear to the brainstem. Their progressive degeneration is associated with disease conditions, excessive noise exposure and aging. Replacement of ANs, which lack the ability to regenerate spontaneously, would have a significant impact on research and advancement in cochlear implants in addition to the amelioration of hearing impairment. The aim of this study was to induce a neuronal phenotype in endogenous non-neural cells in the cochlea, which is the essential organ of hearing. Overexpression of a neurogenic basic helix-loop-helix transcription factor, Ascl1, in the cochlear non-sensory epithelial cells induced neurons at high efficiency at embryonic, postnatal and juvenile stages. Moreover, induced neurons showed typical properties of neuron morphology, gene expression and electrophysiology. Our data indicate that Ascl1 alone or Ascl1 and NeuroD1 is sufficient to reprogram cochlear non-sensory epithelial cells into functional neurons. Generation of neurons from non-neural cells in the cochlea is an important step for the regeneration of ANs in the mature mammalian cochlea.
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Affiliation(s)
- K Nishimura
- Biological Sciences, Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada.
| | - R M Weichert
- Department of Surgery/Otolaryngology, UCSD School of Medicine, La Jolla, CA 92093, USA.
| | - W Liu
- Department of Cell Biology and Neuroscience, Nelson Laboratories, Rutgers University, 604 Allison Road, Piscataway, NJ 08854, USA.
| | - R L Davis
- Department of Cell Biology and Neuroscience, Nelson Laboratories, Rutgers University, 604 Allison Road, Piscataway, NJ 08854, USA.
| | - A Dabdoub
- Biological Sciences, Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada; Department of Otolaryngology - Head and Neck Surgery, University of Toronto, Toronto, ON, Canada; Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
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21
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Vele O, Schrijver I. Inherited hearing loss: molecular genetics and diagnostic testing. ACTA ACUST UNITED AC 2013; 2:231-48. [PMID: 23495655 DOI: 10.1517/17530059.2.3.231] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Hearing loss is a clinically and genetically heterogeneous condition with major medical and social consequences. It affects up to 8% of the general population. OBJECTIVE This review recapitulates the principles of auditory physiology and the molecular basis of hearing loss, outlines the main types of non-syndromic and syndromic deafness by mode of inheritance, and provides an overview of current clinically available genetic testing. METHODS This paper reviews the literature on auditory physiology and on genes, associated with hearing loss, for which genetic testing is presently offered. RESULTS/CONCLUSION The advent of molecular diagnostic assays for hereditary hearing loss permits earlier detection of the underlying causes, facilitates appropriate interventions, and is expected to generate the data necessary for more specific genotype-phenotype correlations.
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Affiliation(s)
- Oana Vele
- Stanford University School of Medicine, Department of Pathology and Pediatrics, L235, 300 Pasteur Drive, Stanford, CA 94305, USA +1 650 724 2403 ; +1 650 724 1567 ;
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22
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Abstract
Among the various central nervous system (CNS) manifestations of mitochondrial disorders (MIDs), cognitive impairment is increasingly recognized and diagnosed (mitochondrial cognitive dysfunction). Aim of the review was to summarize recent findings concerning the aetiology, pathogenesis, diagnosis and treatment of cognitive decline in MIDs. Among syndromic MIDs due to mitochondrial DNA (mtDNA) mutations, cognitive impairment occurs in patients with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes syndrome, myoclonus epilepsy with ragged-red fibres syndrome, mitochondrial chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, neuropathy, ataxia and retinitis pigmentosa syndrome and maternally inherited diabetes and deafness. Among syndromic MIDs due to nuclear DNA (nDNA) mutations, cognitive decline has been reported in myo-neuro-gastro-intestinal encephalopathy, mitochondrial recessive ataxia syndrome, spinocerebellar ataxia with encephalopathy, Mohr-Tranebjaerg syndrome, leuko-encephalopathy; brain and spinal cord involvement and lactic acidosis, CMT2, Wolfram syndrome, Wolf-Hirschhorn syndrome and Leigh syndrome. In addition to syndromic MIDs, a large number of non-syndromic MIDs due to mtDNA as well as nDNA mutations have been reported, which present with cognitive impairment as the sole or one among several other CNS manifestations of a MID. Delineation of mitochondrial cognitive impairment from other types of cognitive impairment is essential to guide the optimal management of these patients. Treatment of mitochondrial cognitive impairment is largely limited to symptomatic and supportive measures. Cognitive impairment may be a CNS manifestation of syndromic as well as non-syndromic MIDs. Correct diagnosis of mitochondrial cognitive impairment is a prerequisite for the optimal management of these patients.
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Affiliation(s)
- J. Finsterer
- Danube University Krems; Krems and Krankenanstalt Rudolfstiftung; Vienna; Austria
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Ha AD, Parratt KL, Rendtorff ND, Lodahl M, Ng K, Rowe DB, Sue CM, Hayes MW, Tranebjaerg L, Fung VS. The phenotypic spectrum of dystonia in Mohr-Tranebjaerg syndrome. Mov Disord 2012; 27:1034-40. [DOI: 10.1002/mds.25033] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 03/17/2012] [Accepted: 04/08/2012] [Indexed: 11/08/2022] Open
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Werner M, Van De Water TR, Andersson T, Arnoldsson G, Berggren D. Morphological and morphometric characteristics of vestibular hair cells and support cells in long term cultures of rat utricle explants. Hear Res 2011; 283:107-16. [PMID: 22127330 DOI: 10.1016/j.heares.2011.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 10/31/2011] [Accepted: 11/03/2011] [Indexed: 11/27/2022]
Abstract
A method for long term culture of utricular macula explants is demonstrated to be stable and reproducible over a period of 28 days in vitro (DIV). This culture system for four-day-old rat utricular maculae is potentially suitable for studies of hair cell loss, repair and regeneration processes as they occur in post-natal mammalian inner ear sensory epithelia. The cellular events that occur within utricular macula hair cell epithelia during 28 days of culture are documented from serial sections. Vestibular hair cells (HCs) and supporting cells (SCs) were systematically counted using light microscopy (LM) and the assistance of morphometric computer software. Ultrastructural observations were made with transmission electron microscopy (TEM) for describing the changes in the fine detailed morphological characteristics that occurred in the explants related to time in vitro. After 2 DIV the density of HCs was 77%, at 21 DIV it was 69%, and at 28 DIV it was 52% of HCs present at explantation. Between 2 DIV and 28 DIV there was a 1.7% decrease of the vestibular macula HC density per DIV. The corresponding decrease of SC density within the utricular explants was less than 1% per DIV. The overall morphology of the epithelia, i.e. relationship of HCs to SCs, was well preserved during the first two weeks in culture. After this time a slight deterioration of the epithelia was observed and although type I and type II HCs were identified by TEM observations, these two HC types could no longer be distinguished from one another by LM observations. In preparations cultured for 21 DIV, SC nuclei were located more apical and further away from the basal membrane compared to their position in macula explants fixed immediately after dissection. The loss of cells that occurred was probably due to expulsion from the apical (i.e. luminal) surface of the sensory epithelia, but no lesions of the apical lining or ruptures of the basal membrane were observed. There were no significant changes in the volume of the vestibular HC comprising macular epithelium during the observation period of 28 DIV.
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Affiliation(s)
- Mimmi Werner
- Department of Clinical Sciences/Otolaryngology, University of Umeå, Umeå, Sweden
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Selective inner hair cell loss in prematurity: a temporal bone study of infants from a neonatal intensive care unit. J Assoc Res Otolaryngol 2011; 12:595-604. [PMID: 21674215 DOI: 10.1007/s10162-011-0273-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Accepted: 05/10/2011] [Indexed: 01/19/2023] Open
Abstract
Premature birth is a well-known risk factor for sensorineural hearing loss in general and auditory neuropathy in particular. However, relatively little is known about the underlying causes, in part because there are so few relevant histopathological studies. Here, we report on the analysis of hair cell loss patterns in 54 temporal bones from premature infants and a control group of 46 bones from full-term infants, all of whom spent time in the neonatal intensive care unit at the Hospital de Niños in San Jose, Costa Rica, between 1977 and 1993. The prevalence of significant hair cell loss was higher in the preterm group than the full-term group (41% vs. 28%, respectively). The most striking finding was the frequency of selective inner hair cell loss, an extremely rare histopathological pattern, in the preterm vs. the full-term babies (27% vs. 3%, respectively). The findings suggest that a common cause of non-genetic auditory neuropathy is selective loss of inner hair cells rather than primary damage to the cochlear nerve.
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The genetic basis of auditory neuropathy spectrum disorder (ANSD). Int J Pediatr Otorhinolaryngol 2011; 75:151-8. [PMID: 21176974 DOI: 10.1016/j.ijporl.2010.11.023] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Revised: 11/24/2010] [Accepted: 11/24/2010] [Indexed: 11/21/2022]
Abstract
OBJECTIVE Auditory neuropathy is a hearing disorder where outer hair cell function within the cochlea is normal, but inner hair cell and/or the auditory nerve function is disrupted. It is a heterogeneous disorder which can have either congenital or acquired causes. Furthermore, the aetiology of auditory neuropathy is vast, which may include prematurity, hyperbilirubinaemia, anoxia, hypoxia, congenital brain anomalies, ototoxic drug exposure, and genetic factors. It is estimated that approximately 40% of cases have an underlying genetic basis, which can be inherited in both syndromic and non syndromic conditions. This review paper provides an overview of the genetic conditions associated with auditory neuropathy spectrum disorders (ANSDs) and highlights some of the defective genes that have been found to be linked to the pathological auditory changes. METHOD Literature search was conducted using a number of resources including textbooks, professional journals and the relevant websites. RESULTS The largest proportion of auditory neuropathy spectrum disorders (ANSDs) is due to genetic factors which can be syndromic, non-syndromic or mitochondrial related. The inheritance pattern can include all the four main types of inheritances such as autosomal dominant, autosomal recessive, X-linked and mitochondrial. CONCLUSION This paper has provided an overview of mutation with some of the genes and/or loci discovered to be the cause for auditory neuropathy spectrum disorders (ANSDs). It has been noted that different gene mutations may trigger different pathological changes in patients with this disorder. These discoveries have provided us with vital information as to the sites of pathology in auditory neuropathy spectrum disorders (ANSDs), and the results highlight the heterogeneity of the disorder.
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Cacace AT, Pinheiro JMB. The mitochondrial connection in auditory neuropathy. Audiol Neurootol 2011; 16:398-413. [PMID: 21266802 DOI: 10.1159/000323276] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 11/30/2010] [Indexed: 12/21/2022] Open
Abstract
'Auditory neuropathy' (AN), the term used to codify a primary degeneration of the auditory nerve, can be linked directly or indirectly to mitochondrial dysfunction. These observations are based on the expression of AN in known mitochondrial-based neurological diseases (Friedreich's ataxia, Mohr-Tranebjærg syndrome), in conditions where defects in axonal transport, protein trafficking, and fusion processes perturb and/or disrupt mitochondrial dynamics (Charcot-Marie-Tooth disease, autosomal dominant optic atrophy), in a common neonatal condition known to be toxic to mitochondria (hyperbilirubinemia), and where respiratory chain deficiencies produce reductions in oxidative phosphorylation that adversely affect peripheral auditory mechanisms. This body of evidence is solidified by data derived from temporal bone and genetic studies, biochemical, molecular biologic, behavioral, electroacoustic, and electrophysiological investigations.
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Affiliation(s)
- Anthony T Cacace
- Department of Communication Sciences and Disorders, Wayne State University, Detroit, Mich 48202, USA. cacacea @ wayne.edu
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Santarelli R. Information from cochlear potentials and genetic mutations helps localize the lesion site in auditory neuropathy. Genome Med 2010; 2:91. [PMID: 21176122 PMCID: PMC3025433 DOI: 10.1186/gm212] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Auditory neuropathy (AN) is a disorder characterized by disruption of auditory nerve activity resulting from lesions involving the auditory nerve (postsynaptic AN), inner hair cells and/or the synapses with auditory nerve terminals (presynaptic AN). Affected subjects show impairment of speech perception beyond that expected for the hearing loss, abnormality of auditory brainstem potentials and preserved outer hair-cell activities. Furthermore, AN can be identified either as an isolated disorder or as an associated disorder with multisystem involvement including peripheral and optic neuropathies (non-isolated AN). Mutations in several nuclear and mitochondrial genes have been identified as underlying these forms of AN. Recently, new genes have been identified as involved in both isolated (DIAPH3, OTOF) and non-isolated AN (OPA1). Moreover, abnormal cochlear potentials have been recorded from patients with specific gene mutations by using acoustic stimuli or electrical stimulation through cochlear implant. In this review, different types of genetically based auditory neuropathies are discussed and the proposed molecular mechanisms underlying AN are reviewed.
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Affiliation(s)
- Rosamaria Santarelli
- Department of Medical and Surgical Specialities, Service of Audiology and Phoniatrics, University of Padua, Via Giustiniani 2, I-35128 Padua, Italy.
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Auditory cortical N100 in pre- and post-synaptic auditory neuropathy to frequency or intensity changes of continuous tones. Clin Neurophysiol 2010; 122:594-604. [PMID: 20822952 DOI: 10.1016/j.clinph.2010.08.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Revised: 07/16/2010] [Accepted: 08/06/2010] [Indexed: 11/23/2022]
Abstract
OBJECTIVES Auditory cortical N100s were examined in ten auditory neuropathy (AN) subjects as objective measures of impaired hearing. METHODS Latencies and amplitudes of N100 in AN to increases of frequency (4-50%) or intensity (4-8 dB) of low (250 Hz) or high (4000 Hz) frequency tones were compared with results from normal-hearing controls. The sites of auditory nerve dysfunction were pre-synaptic (n=3) due to otoferlin mutations causing temperature sensitive deafness, post-synaptic (n=4) affecting other cranial and/or peripheral neuropathies, and undefined (n=3). RESULTS AN consistently had N100s only to the largest changes of frequency or intensity whereas controls consistently had N100s to all but the smallest frequency and intensity changes. N100 latency in AN was significantly delayed compared to controls, more so for 250 than for 4000 Hz and more so for changes of intensity compared to frequency. N100 amplitudes to frequency change were significantly reduced in ANs compared to controls, except for pre-synaptic AN in whom amplitudes were greater than controls. N100 latency to frequency change of 250 but not of 4000 Hz was significantly related to speech perception scores. CONCLUSIONS As a group, AN subjects' N100 potentials were abnormally delayed and smaller, particularly for low frequency. The extent of these abnormalities differed between pre- and post-synaptic forms of the disorder. SIGNIFICANCE Abnormalities of auditory cortical N100 in AN reflect disorders of both temporal processing (low frequency) and neural adaptation (high frequency). Auditory N100 latency to the low frequency provides an objective measure of the degree of impaired speech perception in AN.
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Meyer E, Michaelides M, Tee LJ, Robson AG, Rahman F, Pasha S, Luxon LM, Moore AT, Maher ER. Nonsense mutation in TMEM126A causing autosomal recessive optic atrophy and auditory neuropathy. Mol Vis 2010; 16:650-64. [PMID: 20405026 PMCID: PMC2855733] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 04/06/2010] [Indexed: 11/21/2022] Open
Abstract
PURPOSE To define the phenotype and elucidate the molecular basis for an autosomal recessively inherited optic atrophy and auditory neuropathy in a consanguineous family with two affected children. METHODS Family members underwent detailed ophthalmologic, electrophysiological, and audiological assessments. An autozygosity mapping strategy using high-density single nucleotide polymorphism microarrays and microsatellite markers was used to detect regions of genome homozygosity that might contain the disease gene. Candidate genes were then screened for mutations by direct sequencing. RESULTS Both affected subjects had poor vision from birth and complained of progressive visual loss over time. Current visual acuity ranged from 6/60 to 6/120. Fundus examination revealed bilateral temporal optic nerve pallor in both patients with otherwise normal retinal findings. International-standard full-field electroretinograms were normal in both individuals, with no evidence of generalized retinal dysfunction. Pattern cortical visual evoked potentials were grossly abnormal bilaterally in both cases. The pattern electroretinogram N95:P50 ratio was subnormal, and the P50 was of shortened peak time bilaterally in both patients. The electrophysiological findings were consistent with bilateral retinal ganglion cell/optic nerve dysfunction. Audiological investigation in both siblings revealed abnormalities falling within the auditory neuropathy/dysynchrony spectrum. There were no auditory symptoms and good outer hair cell function (as demonstrated by transient evoked otoacoustic emissions) but impaired inner hair cell/neural function with abnormal stapedial reflex thresholds and abnormal or absent auditory brainstem-evoked responses. The single nucleotide polymorphism microarray data demonstrated a 24.17 Mb region of homozygosity at 11q14.1-11q22.3, which was confirmed by microsatellite marker analysis. The candidate target region contained the transmembrane protein 126A (TMEM126A) gene, and direct sequencing identified a previously described nonsense mutation (c.163C>T; p.Arg55X). CONCLUSIONS We describe the first detailed phenotyping of patients with autosomal recessive TMEM126A-associated optic atrophy and auditory neuropathy. These findings will facilitate the identification of individuals with this recently described disorder.
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MESH Headings
- Adolescent
- Audiometry, Pure-Tone
- Auditory Diseases, Central/complications
- Auditory Diseases, Central/genetics
- Auditory Diseases, Central/physiopathology
- Auditory Threshold/physiology
- Base Sequence
- Codon, Nonsense/genetics
- DNA Mutational Analysis
- Electroretinography
- Evoked Potentials, Auditory, Brain Stem/physiology
- Evoked Potentials, Visual/physiology
- Female
- Fundus Oculi
- Genes, Recessive/genetics
- Genetic Linkage
- Humans
- Male
- Membrane Proteins/genetics
- Molecular Sequence Data
- Nerve Fibers/pathology
- Optic Atrophies, Hereditary/complications
- Optic Atrophies, Hereditary/genetics
- Optic Atrophies, Hereditary/physiopathology
- Otoacoustic Emissions, Spontaneous/physiology
- Pedigree
- Retinal Neurons/pathology
- Young Adult
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Affiliation(s)
- Esther Meyer
- Department of Medical and Molecular Genetics, Institute of Biomedical Research, University of Birmingham, Birmingham, UK
| | - Michel Michaelides
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
- Moorfields Eye Hospital, City Road, London, UK
| | - Louise J. Tee
- Department of Medical and Molecular Genetics, Institute of Biomedical Research, University of Birmingham, Birmingham, UK
| | - Anthony G. Robson
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
- Moorfields Eye Hospital, City Road, London, UK
| | - Fatimah Rahman
- Department of Medical and Molecular Genetics, Institute of Biomedical Research, University of Birmingham, Birmingham, UK
| | - Shanaz Pasha
- Department of Medical and Molecular Genetics, Institute of Biomedical Research, University of Birmingham, Birmingham, UK
| | - Linda M. Luxon
- UCL Ear Institute, 332 Grays Inn Road, London, UK
- Great Ormond Street Hospital for Children, Great Ormond Street, London, UK
| | - Anthony T. Moore
- UCL Institute of Ophthalmology, 11-43 Bath Street, London, UK
- Moorfields Eye Hospital, City Road, London, UK
| | - Eamonn R. Maher
- Department of Medical and Molecular Genetics, Institute of Biomedical Research, University of Birmingham, Birmingham, UK
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Michalewski HJ, Starr A, Zeng FG, Dimitrijevic A. N100 cortical potentials accompanying disrupted auditory nerve activity in auditory neuropathy (AN): effects of signal intensity and continuous noise. Clin Neurophysiol 2009; 120:1352-63. [PMID: 19535287 DOI: 10.1016/j.clinph.2009.05.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 04/17/2009] [Accepted: 05/16/2009] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Auditory temporal processes in quiet are impaired in auditory neuropathy (AN) similar to normal hearing subjects tested in noise. N100 latencies were measured from AN subjects at several tone intensities in quiet and noise for comparison with a group of normal hearing individuals. METHODS Subjects were tested with brief 100 ms tones (1.0 kHz, 100-40 dB SPL) in quiet and in continuous noise (90 dB SPL). N100 latency and amplitude were analyzed as a function of signal intensity and audibility. RESULTS N100 latency in AN in quiet was delayed and amplitude was reduced compared to the normal group; the extent of latency delay was related to psychoacoustic measures of gap detection threshold and speech recognition scores, but not to audibility. Noise in normal hearing subjects was accompanied by N100 latency delays and amplitude reductions paralleling those found in AN tested in quiet. Additional N100 latency delays and amplitude reductions occurred in AN with noise. CONCLUSIONS N100 latency to tones and performance on auditory temporal tasks were related in AN subjects. Noise masking in normal hearing subjects affected N100 latency to resemble AN in quiet. SIGNIFICANCE N100 latency to tones may serve as an objective measure of the efficiency of auditory temporal processes.
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Affiliation(s)
- Henry J Michalewski
- Department of Neurology, Med. Surge I, Room 150, University of California, Irvine, CA 92697-4290, USA.
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Gardiner J, Barton D, Overall R, Marc J. Neurotrophic support and oxidative stress: converging effects in the normal and diseased nervous system. Neuroscientist 2009; 15:47-61. [PMID: 19218230 DOI: 10.1177/1073858408325269] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Oxidative stress and loss of neurotrophic support play major roles in the development of various diseases of the central and peripheral nervous systems. In disorders of the central nervous system such as Alzheimer's, Parkinson's, and Huntington's diseases, oxidative stress appears inextricably linked to the loss of neurotrophic support. A similar situation is seen in the peripheral nervous system in diseases of olfaction, hearing, and vision. Neurotrophic factors act to up-regulate antioxidant enzymes and promote the expression of antioxidant proteins. On the other hand, oxidative stress can cause down-regulation of neurotrophic factors. We propose that normal functioning of the nervous systems involves a positive feedback loop between antioxidant processes and neurotrophic support. Breakdown of this feedback loop in disease states leads to increased oxidative stress and reduced neurotrophic support.
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Affiliation(s)
- John Gardiner
- School of Biological Sciences, University of Sydney, Camperdown, Australia.
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Brookes JT, Kanis AB, Tan LY, Tranebjaerg L, Vore A, Smith RJH. Cochlear implantation in deafness-dystonia-optic neuronopathy (DDON) syndrome. Int J Pediatr Otorhinolaryngol 2008; 72:121-6. [PMID: 17936919 DOI: 10.1016/j.ijporl.2007.08.019] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 08/22/2007] [Accepted: 08/23/2007] [Indexed: 11/29/2022]
Abstract
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.
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Affiliation(s)
- James T Brookes
- Department of Surgery, Division of Pediatric Surgery, University of Calgary, Calgary, Alberta, Canada.
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Matsumoto M, Sekiya T, Kojima K, Ito J. An animal experimental model of auditory neuropathy induced in rats by auditory nerve compression. Exp Neurol 2007; 210:248-56. [PMID: 18178187 DOI: 10.1016/j.expneurol.2007.11.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Revised: 11/02/2007] [Accepted: 11/03/2007] [Indexed: 01/19/2023]
Abstract
Several animal models of auditory neuropathy (AN) have been produced by employing pharmacological agents to damage auditory neurons or hair cells selectively. The specificity of pharmacological lesions is generally assessed by observation of visible structural damage but it is difficult to localize the delivery, which could lead to functional side effects in other anatomical structures. Although genetic analyses of human AN patients have provided important information on the pathophysiology of AN, specific genetic defects have not been fully correlated with functional deficits in the auditory nervous system. To address this problem, we compressed rat auditory nerves to assess neural degeneration for up to 35 weeks. The method produced a good model of auditory neuropathy, including profound deterioration of the auditory brainstem response and preservation of both cochlear microphonics and distortion product otoacoustic emissions. Histological examination revealed that in spite of profound degeneration of the auditory nerve, the hair cells remained intact. The model provides a complementary alternative to those based on pharmacological lesions and genetic analyses of AN patients and should allow analysis of the pathophysiology of auditory neuropathy with less risk of the results being confounded by unknown deficits in other cell types.
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Affiliation(s)
- Masahiro Matsumoto
- Department of Otolaryngology, Head and Neck Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan
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