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Wu YL, Chen L, Zhu HY, Luo WY, Shi K, Hou XY, Sun JW, Sun JQ, Guo XT. Relationships between bilateral auditory brainstem activity and inter-implant interval in children with cochlear implants. Eur Arch Otorhinolaryngol 2024; 281:1735-1743. [PMID: 37924365 DOI: 10.1007/s00405-023-08285-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 10/09/2023] [Indexed: 11/06/2023]
Abstract
PURPOSE To investigate the effect of the interval between bilateral cochlear implantation on the development of bilateral peripheral auditory pathways as revealed by the electrically evoked auditory brainstem response (EABR). METHODS Fifty-eight children with profound bilateral sensorineural hearing loss were recruited. Among them, 33 children received sequential bilateral cochlear implants (CIs), and 25 children received simultaneous bilateral CIs. The bilateral EABRs evoked by electrical stimulation from the CI electrode were recorded on the day of second-side CI activation. RESULTS The latencies of wave III (eIII) and wave V (eV) were significantly shorter on the first CI side than on the second CI side in children with sequential bilateral CIs but were similar between the two sides in children with simultaneous bilateral CIs. Furthermore, the latencies were prolonged from apical to basal channels along the cochlea in the two groups. In children with sequential CIs, the inter-implant interval was negatively correlated with the eV latency on the first CI side and was positively correlated with bilateral differences in the eIII and eV latencies. CONCLUSIONS Unilateral CI use promotes the maturation of ipsilateral auditory conduction function. However, a longer inter-implant interval results in more unbalanced development of bilateral auditory brainstem pathways. Bilateral cochlear implantation with no or a short interval is recommended.
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Affiliation(s)
- Yan-Lin Wu
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Li Chen
- Department of Otolaryngology-Head and Neck Surgery, The Fifth Affiliated Hospital of Zunyi Medical University, Zhuhai, 519100, Guangdong, China
| | - Han-Yu Zhu
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Wen-Yun Luo
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Kai Shi
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Xiao-Yan Hou
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Jing-Wu Sun
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China.
| | - Jia-Qiang Sun
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China.
| | - Xiao-Tao Guo
- Department of Otolaryngology-Head and Neck Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, 230001, Anhui, China.
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Swords C, Geerardyn A, Zhu M, O'Malley JT, Wu P, Arenberg JG, Podury A, Brassett C, Bance M, Quesnel AM. Incomplete Partition Type II Cochlear Malformations: Delineating the Three-Dimensional Structure from Digitized Human Histopathological Specimens. Otol Neurotol 2023; 44:881-889. [PMID: 37621122 PMCID: PMC10803064 DOI: 10.1097/mao.0000000000003999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/26/2023]
Abstract
HYPOTHESIS There are clinically relevant differences in scalae anatomy and spiral ganglion neuron (SGN) quantity between incomplete partition type II (IP-II) and normal cochleae. BACKGROUND IP-II is a commonly implanted cochlear malformation. Detailed knowledge of intracochlear three-dimensional (3D) morphology may assist with cochlear implant (CI) electrode selection/design and enable optimization of audiologic programming based on SGN maps. METHODS IP-II (n = 11) human temporal bone histological specimens were identified from the National Institute on Deafness and Other Communication Disorders National Temporal Bone Registry and digitized. The cochlear duct, scalae, and surgically relevant anatomy were reconstructed in 3D. A machine learning algorithm was applied to map the location and number of SGNs. RESULTS 3D scalae morphology of the basal turn was normal. Scala tympani (ST) remained isolated for 540 degrees before fusing with scala vestibuli. Mean ST volume reduced below 1 mm 2 after the first 340 degrees. Scala media was a distinct endolymphatic compartment throughout; mean ± standard deviation cochlear duct length was 28 ± 3 mm. SGNs were reduced compared with age-matched norms (mean, 48%; range, 5-90%). In some cases, SGNs failed to ascend Rosenthal's canal, remaining in an abnormal basalward modiolar location. Two forms of IP-II were seen: type A and type B. A majority (98-100%) of SGNs were located in the basal modiolus in type B IP-II, compared with 76 to 85% in type A. CONCLUSION Hallmark features of IP-II cochleae include the following: 1) fusion of the ST and scala vestibuli at a mean of 540 degrees, 2) highly variable and overall reduced SGN quantity compared with normative controls, and 3) abnormal SGN distribution with cell bodies failing to ascend Rosenthal's canal.
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Affiliation(s)
| | | | | | | | | | | | | | - Cecilia Brassett
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Manohar Bance
- Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
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Mohamed T, Melfi V, Colciago A, Magnaghi V. Hearing loss and vestibular schwannoma: new insights into Schwann cells implication. Cell Death Dis 2023; 14:629. [PMID: 37741837 PMCID: PMC10517973 DOI: 10.1038/s41419-023-06141-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 09/05/2023] [Accepted: 09/08/2023] [Indexed: 09/25/2023]
Abstract
Hearing loss (HL) is the most common and heterogeneous disorder of the sensory system, with a large morbidity in the worldwide population. Among cells of the acoustic nerve (VIII cranial nerve), in the cochlea are present the hair cells, the spiral ganglion neurons, the glia-like supporting cells, and the Schwann cells (SCs), which alterations have been considered cause of HL. Notably, a benign SC-derived tumor of the acoustic nerve, named vestibular schwannoma (VS), has been indicated as cause of HL. Importantly, SCs are the main glial cells ensheathing axons and forming myelin in the peripheral nerves. Following an injury, the SCs reprogram, expressing some stemness features. Despite the mechanisms and factors controlling their biological processes (i.e., proliferation, migration, differentiation, and myelination) have been largely unveiled, their role in VS and HL was poorly investigated. In this review, we enlighten some of the mechanisms at the base of SCs transformation, VS development, and progression, likely leading to HL, and we pose great attention on the environmental factors that, in principle, could contribute to HL onset or progression. Combining the biomolecular bench-side approach to the clinical bedside practice may be helpful for the diagnosis, prediction, and therapeutic approach in otology.
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Affiliation(s)
- Tasnim Mohamed
- Department of Pharmacological and Biomolecular Sciences "Rodolfo Paoletti", Università degli Studi di Milano, Via G. Balzaretti 9, 20133, Milan, Italy
| | - Valentina Melfi
- Department of Pharmacological and Biomolecular Sciences "Rodolfo Paoletti", Università degli Studi di Milano, Via G. Balzaretti 9, 20133, Milan, Italy
- Fondazione IRCCS Istituto Nazionale dei Tumori, Via G. Venezian 1, 20133, Milan, Italy
| | - Alessandra Colciago
- Department of Pharmacological and Biomolecular Sciences "Rodolfo Paoletti", Università degli Studi di Milano, Via G. Balzaretti 9, 20133, Milan, Italy
| | - Valerio Magnaghi
- Department of Pharmacological and Biomolecular Sciences "Rodolfo Paoletti", Università degli Studi di Milano, Via G. Balzaretti 9, 20133, Milan, Italy.
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Hughes ML. Electrically evoked compound action potential polarity sensitivity, refractory-recovery, and behavioral multi-pulse integration as potential indices of neural health in cochlear-implant recipients. Hear Res 2023; 433:108764. [PMID: 37062161 PMCID: PMC10322179 DOI: 10.1016/j.heares.2023.108764] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Revised: 03/26/2023] [Accepted: 04/05/2023] [Indexed: 04/18/2023]
Affiliation(s)
- Michelle L Hughes
- University of Nebraska-Lincoln, Dept. of Special Education and Communication Disorders, 276 Barkley Memorial Center, 4072 East Campus Loop, Lincoln, NE, 68583, USA.
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Zamaninezhad L, Mert B, Benav H, Tillein J, Garnham C, Baumann U. Factors influencing the relationship between cochlear health measures and speech recognition in cochlear implant users. Front Integr Neurosci 2023; 17:1125712. [PMID: 37251736 PMCID: PMC10213548 DOI: 10.3389/fnint.2023.1125712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 03/27/2023] [Indexed: 05/31/2023] Open
Abstract
Background One factor which influences the speech intelligibility of cochlear implant (CI) users is the number and the extent of the functionality of spiral ganglion neurons (SGNs), referred to as "cochlear health." To explain the interindividual variability in speech perception of CI users, a clinically applicable estimate of cochlear health could be insightful. The change in the slope of the electrically evoked compound action potentials (eCAP), amplitude growth function (AGF) as a response to increased interphase gap (IPG) (IPGEslope) has been introduced as a potential measure of cochlear health. Although this measure has been widely used in research, its relationship to other parameters requires further investigation. Methods This study investigated the relationship between IPGEslope, demographics and speech intelligibility by (1) considering the relative importance of each frequency band to speech perception, and (2) investigating the effect of the stimulus polarity of the stimulating pulse. The eCAPs were measured in three different conditions: (1) Forward masking with anodic-leading (FMA) pulse, (2) Forward masking with cathodic-leading (FMC) pulse, and (3) with alternating polarity (AP). This allowed the investigation of the effect of polarity on the diagnosis of cochlear health. For an accurate investigation of the correlation between IPGEslope and speech intelligibility, a weighting function was applied to the measured IPGEslopes on each electrode in the array to consider the relative importance of each frequency band for speech perception. A weighted Pearson correlation analysis was also applied to compensate for the effect of missing data by giving higher weights to the ears with more successful IPGEslope measurements. Results A significant correlation was observed between IPGEslope and speech perception in both quiet and noise for between-subject data especially when the relative importance of frequency bands was considered. A strong and significant correlation was also observed between IPGEslope and age when stimulation was performed with cathodic-leading pulses but not for the anodic-leading pulse condition. Conclusion Based on the outcome of this study it can be concluded that IPGEslope has potential as a relevant clinical measure indicative of cochlear health and its relationship to speech intelligibility. The polarity of the stimulating pulse could influence the diagnostic potential of IPGEslope.
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Affiliation(s)
| | - Berkutay Mert
- ENT/Audiological Acoustics, University Hospital, Goethe University Frankfurt, Frankfurt, Germany
| | | | | | | | - Uwe Baumann
- ENT/Audiological Acoustics, University Hospital, Goethe University Frankfurt, Frankfurt, Germany
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Human cochlear microstructures at risk of electrode insertion trauma, elucidated in 3D with contrast-enhanced microCT. Sci Rep 2023; 13:2191. [PMID: 36750646 PMCID: PMC9905077 DOI: 10.1038/s41598-023-29401-6] [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: 10/14/2022] [Accepted: 02/03/2023] [Indexed: 02/09/2023] Open
Abstract
Cochlear implant restores hearing loss through electrical stimulation of the hearing nerve from within the cochlea. Unfortunately, surgical implantation of this neuroprosthesis often traumatizes delicate intracochlear structures, resulting in loss of residual hearing and compromising hearing in noisy environments and appreciation of music. To avoid cochlear trauma, insertion techniques and devices have to be adjusted to the cochlear microanatomy. However, existing techniques were unable to achieve a representative visualization of the human cochlea: classical histology damages the tissues and lacks 3D perspective; standard microCT fails to resolve the cochlear soft tissues; and previously used X-ray contrast-enhancing staining agents are destructive. In this study, we overcame these limitations by performing contrast-enhanced microCT imaging (CECT) with a novel polyoxometalate staining agent Hf-WD POM. With Hf-WD POM-based CECT, we achieved nondestructive, high-resolution, simultaneous, 3D visualization of the mineralized and soft microstructures in fresh-frozen human cochleae. This enabled quantitative analysis of the true intracochlear dimensions and led to anatomical discoveries, concerning surgically-relevant microstructures: the round window membrane, the Rosenthal's canal and the secondary spiral lamina. Furthermore, we demonstrated that Hf-WD POM-based CECT enables quantitative assessment of these structures as well as their trauma.
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Croner AM, Heshmat A, Schrott-Fischer A, Glueckert R, Hemmert W, Bai S. Effects of Degrees of Degeneration on the Electrical Excitation of Human Spiral Ganglion Neurons Based on a High-Resolution Computer Model. Front Neurosci 2022; 16:914876. [PMID: 35873813 PMCID: PMC9298973 DOI: 10.3389/fnins.2022.914876] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 06/13/2022] [Indexed: 11/13/2022] Open
Abstract
After hearing loss retrograde degeneration of spiral ganglion neurons (SGNs) has been described. Studies modeling the effects of degeneration mostly omitted peripheral processes (dendrites). Recent experimental observations indicated that degenerating SGNs manifested also a reduced diameter of their dendrites. We simulated populations of 400 SGNs inside a high resolution cochlear model with a cochlear implant, based on μCT scans of a human temporal bone. Cochlear implant stimuli were delivered as biphasic pulses in a monopolar configuration. Three SGN situations were simulated, based on our previous measurements of human SGN dendrites: (A) SGNs with intact dendrites (before degeneration), (B) degenerating SGNs, dendrites with a smaller diameter but original length, (C) degenerating SGNs, dendrites omitted. SGN fibers were mapped to characteristic frequency, and place pitch was estimated from excitation profiles. Results from degenerating SGNs (B, C) were similar. Most action potentials were initiated in the somatic area for all cases (A, B, C), except for areas near stimulating electrodes in the apex with intact SGNs (A), where action potentials were initiated in the distal dendrite. In most cases, degenerating SGNs had lower thresholds than intact SGNs (A) (down to -2 dB). Excitation profiles showed increased ectopic activation, i.e., activation of unintended neuronal regions, as well as similar neuronal regions excited by different apical electrodes, for degenerating SGNs (B, C). The estimated pitch showed cases of pitch reversals in apical electrodes for intact SGNs (A), as well as mostly identical pitches evoked by the four most apical electrodes for degenerating SGNs (B, C). In conclusion, neuronal excitation profiles to electrical stimulation exhibited similar traits in both ways of modeling SGN degeneration. Models showed degeneration of dendrites caused increased ectopic activation, as well as similar excitation profiles and pitch evoked by different apical electrodes. Therefore, insertion of electrodes beyond approximately 450° may not provide any benefit if SGN dendrites are degenerated.
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Affiliation(s)
- Albert M Croner
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany.,Munich Institute of Biomedical Engineering, Technical University of Munich, Garching, Germany
| | - Amirreza Heshmat
- Laboratory for Inner Ear Biology, Medical University of Innsbruck, Innsbruck, Austria
| | | | - Rudolf Glueckert
- Laboratory for Inner Ear Biology, Medical University of Innsbruck, Innsbruck, Austria
| | - Werner Hemmert
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany.,Munich Institute of Biomedical Engineering, Technical University of Munich, Garching, Germany
| | - Siwei Bai
- Department of Electrical and Computer Engineering, Technical University of Munich, Munich, Germany.,Munich Institute of Biomedical Engineering, Technical University of Munich, Garching, Germany
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8
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Sismono F, Leblans M, Mancini L, Veneziano A, Zanini F, Dirckx J, Bernaerts A, de Foer B, Offeciers E, Zarowski A. 3D-localisation of cochlear implant electrode contacts in relation to anatomical structures from in vivo cone-beam computed tomography. Hear Res 2022; 426:108537. [DOI: 10.1016/j.heares.2022.108537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 03/18/2022] [Accepted: 05/23/2022] [Indexed: 12/11/2022]
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9
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Zhu HY, Chen L, Hou XY, Tang ZQ, Sun JQ, Sun JW, Guo XT. Electrically evoked auditory brainstem responses in deaf patients with Mondini malformation during cochlear implantation. Eur Arch Otorhinolaryngol 2022; 279:4847-4852. [PMID: 35247096 DOI: 10.1007/s00405-022-07307-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/08/2022] [Indexed: 11/30/2022]
Abstract
PURPOSE To investigate the auditory pathway functions in deaf patients with Mondini malformation using the electrically evoked auditory brainstem response (EABR) during cochlear implantation (CI). METHODS A total of 58 patients with severe to profound sensorineural hearing loss (SNHL) were included in this study. Of these patients, 27 cases had Mondini malformation and 31 control cases had no inner ear malformations (IEMs). Intraoperative EABRs evoked by electrical stimulation at the round window niche (RWN) and round window membrane (RWM) were recorded. RESULTS Patients with Mondini malformation showed significantly lower EABR extraction rates than those with no IEMs did. However, for patients who showed EABRs, no significant difference in EABR thresholds, wave III (eIII) latencies, wave V (eV) latencies or eIII-eV latency intervals was found between two groups. CONCLUSION The physiological functions of the peripheral auditory system in patients with Mondini malformation may divide into opposite extremes, as revealed by a robust EABR and the absence of the EABR, respectively. The auditory conduction function should be objectively and individually evaluated for patients with Mondini malformation by the EABR.
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Affiliation(s)
- Han-Yu Zhu
- Department of Otolaryngology-Head and Neck Surgery, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Li Chen
- Department of Otolaryngology-Head and Neck Surgery, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Xiao-Yan Hou
- Department of Otolaryngology-Head and Neck Surgery, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, 230001, Anhui, China
| | - Zheng-Quan Tang
- School of Life Sciences, Anhui University, Hefei, 230601, Anhui, China.,Key Laboratory of Human Microenvironment and Precision Medicine of Anhui Higher Education Institutes, Anhui University, Hefei, 230601, Anhui, China
| | - Jia-Qiang Sun
- Department of Otolaryngology-Head and Neck Surgery, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, 230001, Anhui, China.
| | - Jing-Wu Sun
- Department of Otolaryngology-Head and Neck Surgery, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, 230001, Anhui, China.
| | - Xiao-Tao Guo
- Department of Otolaryngology-Head and Neck Surgery, Division of Life Sciences and Medicine, The First Affiliated Hospital of USTC, University of Science and Technology of China, Hefei, 230001, Anhui, China. .,CAS Key Laboratory of Brain Function and Diseases, School of Life Sciences, University of Science and Technology of China, Hefei, 230027, Anhui, China.
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Langlie J, Finberg A, Bencie NB, Mittal J, Omidian H, Omidi Y, Mittal R, Eshraghi AA. Recent advancements in cell-based models for auditory disorders. BIOIMPACTS 2022; 12:155-169. [PMID: 35411298 PMCID: PMC8905588 DOI: 10.34172/bi.2022.23900] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 10/09/2021] [Accepted: 11/15/2021] [Indexed: 11/24/2022]
Abstract
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Introduction: Cell-based models play an important role in understanding the pathophysiology and etiology of auditory disorders. For the auditory system, models have primarily focused on restoring inner and outer hair cells. However, they have largely underrepresented the surrounding structures and cells that support the function of the hair cells.
Methods: In this article, we will review recent advancements in the evolution of cell-based models of auditory disorders in their progression towards three dimensional (3D) models and organoids that more closely mimic the pathophysiology in vivo.
Results: With the elucidation of the molecular targets and transcription factors required to generate diverse cell lines of the components of inner ear, research is starting to progress from two dimensional (2D) models to a greater 3D approach. Of note, the 3D models of the inner ear, including organoids, are relatively new and emerging in the field. As 3D models of the inner ear continue to evolve in complexity, their role in modeling disease will grow as they bridge the gap between cell culture and in vivo models.
Conclusion: Using 3D cell models to understand the etiology and molecular mechanisms underlying auditory disorders holds great potential for developing more targeted and effective novel therapeutics.
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Affiliation(s)
- Jake Langlie
- Department of Otolaryngology, Cochlear Implant and Hearing Research Laboratory, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Ariel Finberg
- Department of Otolaryngology, Cochlear Implant and Hearing Research Laboratory, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Nathalie B. Bencie
- Department of Otolaryngology, Cochlear Implant and Hearing Research Laboratory, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Jeenu Mittal
- Department of Otolaryngology, Cochlear Implant and Hearing Research Laboratory, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Hossein Omidian
- Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL 33328, USA
| | - Yadollah Omidi
- Department of Pharmaceutical Sciences, College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL 33328, USA
| | - Rahul Mittal
- Department of Otolaryngology, Cochlear Implant and Hearing Research Laboratory, University of Miami Miller School of Medicine, Miami, Florida, USA
| | - Adrien A. Eshraghi
- Department of Otolaryngology, Cochlear Implant and Hearing Research Laboratory, University of Miami Miller School of Medicine, Miami, Florida, USA
- Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, Florida, USA
- Department of Biomedical Engineering, University of Miami, Coral Gables, Florida, USA
- Department of Pediatrics, University of Miami Miller School of Medicine, Miami, Florida, USA
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11
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Hughes ML. Characterizing Polarity Sensitivity in Cochlear Implant Recipients: Demographic Effects and Potential Implications for Estimating Neural Health. J Assoc Res Otolaryngol 2022; 23:301-318. [PMID: 34988867 DOI: 10.1007/s10162-021-00824-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Accepted: 11/17/2021] [Indexed: 11/29/2022] Open
Abstract
Stimulus polarity can affect both physiological and perceptual measures in cochlear-implant recipients. Large differences between polarities for various outcome measures (e.g., eCAP threshold, amplitude, or slope) theoretically reflect poorer neural health, whereas smaller differences reflect better neural health. Therefore, we expect large polarity effects to be correlated with other measures shown to contribute to poor neural health, such as advanced age or prolonged deafness. Our earlier studies using the electrically evoked compound action potential (eCAP) demonstrated differences in polarity effects between users of Cochlear and Advanced Bionics devices when device-specific clinical pulse designs were used. Since the stimuli differed slightly between devices, the first goal of this study was to determine whether small, clinically relevant differences in pulse phase duration (PD) have a significant impact on eCAP polarity effects to potentially explain the device differences observed previously. Polarity effects were quantified as the difference in eCAP thresholds, mean normalized amplitudes, and slope of the amplitude growth function obtained for anodic-first versus cathodic-first biphasic pulses. The results showed that small variations in PD did not explain the observed differences in eCAP polarity effects between devices. Therefore, eCAP polarity sensitivity measures are relatively robust to small differences in pulse parameters. However, it remains unclear what underlies the observed manufacturer differences, which may limit the utility of eCAP polarity sensitivity measures. The second goal was to characterize polarity sensitivity in a large group of CI recipients (65 ears) to relate polarity sensitivity to age and duration of deafness as a proxy for neural health. The same pulse parameters were used for both device groups. The only significant predictors of eCAP polarity effects were age for threshold and amplitude polarity effects for Cochlear recipients and age and duration of deafness for slope for AB recipients. However, three of these four correlations were in the opposite direction of what was expected. These results suggest that eCAP polarity sensitivity measures likely reflect different mechanisms than the effects that age and duration of deafness induce on the peripheral auditory system.
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Affiliation(s)
- Michelle L Hughes
- Department of Special Education and Communication Disorders, University of Nebraska-Lincoln, 276 Barkley Memorial Center, Lincoln, NE, 68583, USA.
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12
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ExplantAnalyzer: An advanced automated neurite outgrowth analysis evaluated by means of organotypic auditory neuron explant cultures. J Neurosci Methods 2021; 363:109341. [PMID: 34474047 DOI: 10.1016/j.jneumeth.2021.109341] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 07/30/2021] [Accepted: 08/25/2021] [Indexed: 12/17/2022]
Abstract
BACKGROUND Neuronal outgrowth assays using organotypic explant cultures are commonly utilized to study neuroregenerative and -protective effects of drugs such as neurotrophins. While this approach offers higher organized tissue compared to single cell cultures and less experimental effort than in-vivo studies, quantitative evaluation of the neuronal network is often time consuming. Thus, we developed ExplantAnlayzer, a time-saving high-throughput evaluation method, yielding numerous metrics to objectively describe neuronal outgrowth. NEW METHOD Spiral ganglion explants were cultured in 24-well plates, mechanically fixed in a collagen matrix and immunolabeled against beta-III-tubulin. The explants were imaged using a fluorescent tile-scan microscope and resulting images were stitched. The evaluation was developed as an open-source MATLAB routine and involves several image processing steps, including adaptive thresholding. The neurite network was eventually converted to a graph to track neurites from their terminals back to the explant body. COMPARISON WITH EXISTING METHOD(S) We compared ExplantAnlayzer quantitatively and qualitatively to common existing methods, such as Sholl analyses and manual fiber tracing, using representative explant images. ExplantAnlayzer is able to achieve similar and as detailed results as manual tracing while decreasing manual interaction and required time dramatically. RESULTS After an initial setup phase, the explant images could be batch-processed altogether. Bright bundles as well as faint fibers were reliably detected. Several metrics describing the outgrowth morphology, including total outgrowth, neurite numbers and length estimations, as well as their growth directions, were computed. CONCLUSIONS ExplantAnalyzer is a time-saving and objective method for an in-depth evaluation of organotypic explant outgrowth.
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Hosoya M, Fujioka M, Murayama AY, Ozawa H, Okano H, Ogawa K. Neuronal development in the cochlea of a nonhuman primate model, the common marmoset. Dev Neurobiol 2021; 81:905-938. [PMID: 34545999 PMCID: PMC9298346 DOI: 10.1002/dneu.22850] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/25/2021] [Accepted: 09/13/2021] [Indexed: 01/02/2023]
Abstract
Precise cochlear neuronal development is vital to hearing ability. Understanding the developmental process of the spiral ganglion is useful for studying hearing loss aimed at aging or regenerative therapy. Although interspecies differences have been reported between rodents and humans, to date, most of our knowledge about the development of cochlear neuronal development has been obtained from rodent models because of the difficulty in using human fetal samples in this field. In this study, we investigated cochlear neuronal development in a small New World monkey species, the common marmoset (Callithrix jacchus). We examined more than 25 genes involved in the neuronal development of the cochlea and described the critical developmental steps of these neurons. We also revealed similarities and differences between previously reported rodent models and this primate animal model. Our results clarified that this animal model of cochlear neuronal development is more similar to humans than rodents and is suitable as an alternative for the analysis of human cochlear development. The time course established in this report will be a useful tool for studying primate‐specific neuronal biology of the inner ear, which could eventually lead to new treatment strategies for human hearing loss.
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Affiliation(s)
- Makoto Hosoya
- Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Masato Fujioka
- Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Ayako Y Murayama
- Department of Physiology, Keio University School of Medicine, Tokyo, Japan.,Laboratory for Marmoset Neural Architecture, Center for Brain Science, RIKEN, Wako, Japan
| | - Hiroyuki Ozawa
- Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, Tokyo, Japan
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, Tokyo, Japan.,Laboratory for Marmoset Neural Architecture, Center for Brain Science, RIKEN, Wako, Japan
| | - Kaoru Ogawa
- Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, Tokyo, Japan
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14
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Hough K, Verschuur CA, Cunningham C, Newman TA. Macrophages in the cochlea; an immunological link between risk factors and progressive hearing loss. Glia 2021; 70:219-238. [PMID: 34536249 DOI: 10.1002/glia.24095] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 09/08/2021] [Accepted: 09/09/2021] [Indexed: 02/06/2023]
Abstract
Macrophages are abundant in the cochlea; however, their role in hearing loss is not well understood. Insults to the cochlea, such as noise or insertion of a cochlear implant, cause an inflammatory response, which includes activation of tissue-resident macrophages. Activation is characterized by changes in macrophage morphology, mediator expression, and distribution. Evidence from other organs shows activated macrophages can become primed, whereby subsequent insults cause an elevated inflammatory response. Primed macrophages in brain pathologies respond to circulating inflammatory mediators by disproportionate synthesis of inflammatory mediators. This signaling occurs behind an intact blood-brain barrier, similar to the blood-labyrinth barrier in the cochlea. Local tissue damage can occur as the result of mediator release by activated macrophages. Damage is typically localized; however, if it is to structures with limited ability to repair, such as neurons or hair cells within the cochlea, it is feasible that this contributes to the progressive loss of function seen in hearing loss. We propose that macrophages in the cochlea link risk factors and hearing loss. Injury to the cochlea causes local macrophage activation that typically resolves. However, in susceptible individuals, some macrophages enter a primed state. Once primed, these macrophages can be further activated, as a consequence of circulating inflammatory molecules associated with common co-morbidities. Hypothetically, this would lead to further cochlear damage and loss of hearing. We review the evidence for the role of tissue-resident macrophages in the cochlea and propose that cochlear macrophages contribute to the trajectory of hearing loss and warrant further study.
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Affiliation(s)
- Kate Hough
- Faculty of Engineering and Physical Sciences, University of Southampton, Southampton, UK
| | - Carl A Verschuur
- Faculty of Engineering and Physical Sciences, Auditory Implant Centre, University of Southampton, Southampton, UK
| | - Colm Cunningham
- School of Biochemistry & Immunology, Trinity Biomedical Sciences Institute & Trinity College Institute of Neuroscience (TCIN), Dublin, Ireland
| | - Tracey A Newman
- Clinical and Experimental Sciences, Faculty of Medicine, IfLS, University of Southampton, Southampton, UK
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15
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Eckert MA, Harris KC, Lang H, Lewis MA, Schmiedt RA, Schulte BA, Steel KP, Vaden KI, Dubno JR. Translational and interdisciplinary insights into presbyacusis: A multidimensional disease. Hear Res 2021; 402:108109. [PMID: 33189490 PMCID: PMC7927149 DOI: 10.1016/j.heares.2020.108109] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 10/19/2020] [Accepted: 10/25/2020] [Indexed: 12/18/2022]
Abstract
There are multiple etiologies and phenotypes of age-related hearing loss or presbyacusis. In this review we summarize findings from animal and human studies of presbyacusis, including those that provide the theoretical framework for distinct metabolic, sensory, and neural presbyacusis phenotypes. A key finding in quiet-aged animals is a decline in the endocochlear potential (EP) that results in elevated pure-tone thresholds across frequencies with greater losses at higher frequencies. In contrast, sensory presbyacusis appears to derive, in part, from acute and cumulative effects on hair cells of a lifetime of environmental exposures (e.g., noise), which often result in pronounced high frequency hearing loss. These patterns of hearing loss in animals are recognizable in the human audiogram and can be classified into metabolic and sensory presbyacusis phenotypes, as well as a mixed metabolic+sensory phenotype. However, the audiogram does not fully characterize age-related changes in auditory function. Along with the effects of peripheral auditory system declines on the auditory nerve, primary degeneration in the spiral ganglion also appears to contribute to central auditory system aging. These inner ear alterations often correlate with structural and functional changes throughout the central nervous system and may explain suprathreshold speech communication difficulties in older adults with hearing loss. Throughout this review we highlight potential methods and research directions, with the goal of advancing our understanding, prevention, diagnosis, and treatment of presbyacusis.
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Affiliation(s)
- Mark A Eckert
- Medical University of South Carolina, Department of Otolaryngology - Head and Neck Surgery, Charleston, SC 29425, USA.
| | - Kelly C Harris
- Medical University of South Carolina, Department of Otolaryngology - Head and Neck Surgery, Charleston, SC 29425, USA
| | - Hainan Lang
- Medical University of South Carolina, Department of Pathology and Laboratory Medicine, Charleston, SC 29425, USA
| | - Morag A Lewis
- King's College London, Wolfson Centre for Age-Related Diseases, London SE1 1UL, United Kingdom
| | - Richard A Schmiedt
- Medical University of South Carolina, Department of Otolaryngology - Head and Neck Surgery, Charleston, SC 29425, USA
| | - Bradley A Schulte
- Medical University of South Carolina, Department of Pathology and Laboratory Medicine, Charleston, SC 29425, USA; Medical University of South Carolina, Department of Otolaryngology - Head and Neck Surgery, Charleston, SC 29425, USA
| | - Karen P Steel
- King's College London, Wolfson Centre for Age-Related Diseases, London SE1 1UL, United Kingdom
| | - Kenneth I Vaden
- Medical University of South Carolina, Department of Otolaryngology - Head and Neck Surgery, Charleston, SC 29425, USA
| | - Judy R Dubno
- Medical University of South Carolina, Department of Otolaryngology - Head and Neck Surgery, Charleston, SC 29425, USA; Medical University of South Carolina, Department of Pathology and Laboratory Medicine, Charleston, SC 29425, USA
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16
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Gärtner L, Klötzer K, Lenarz T, Scheper V. Correlation of Electrically Evoked Compound Action Potential Amplitude Growth Function Slope and Anamnestic Parameters in Cochlear Implant Patients-Identification of Predictors for the Neuronal Health Status. Life (Basel) 2021; 11:life11030203. [PMID: 33807687 PMCID: PMC7999542 DOI: 10.3390/life11030203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 02/26/2021] [Accepted: 03/01/2021] [Indexed: 01/04/2023] Open
Abstract
Cochlear implants (CI) are the treatment of choice in profoundly deaf patients. Measuring the electrically evoked compound action potential (ECAP) has become an important tool for verifying the function of the spiral ganglion neurons (SGN), which are the target cells of the CI stimulation. ECAP measurement is only possible after electrode insertion. No information about the neuronal health status is available before cochlear implantation. We investigated possible correlations between the ECAP amplitude growth function (AGF) slope and anamnestic parameters to identify possible predictors for SGN health status and therefore for CI outcome. The study included patients being implanted with various electrode array lengths. Correlation analysis was performed for the mean AGF slope of the whole array, for separate electrodes as well as for grouped electrodes of the apical, medial, and basal region, with duration of deafness, age at implantation, residual hearing (grouped for electrode length), and etiology. The mean ECAP AGF slopes decreased from apical to basal. They were not correlated to the length of the electrode array or any etiology. For the mean of the full array or when grouped for the apical, middle, and basal part, the ECAP AGF slope was negatively correlated to the duration of hearing loss and the age at implantation. Since a significant negative correlation of the ECAP AGF slope and age at cochlear implantation and duration of deafness was observed, this study supports the statement that early implantation of a CI is recommended for sensorineural hearing loss. Additional factors such as the cochlear coverage and insertion angle influence the ECAP AGF slope and performance of the patient and should be included in future multifactorial analysis to study predictive parameters for the CI outcome.
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Affiliation(s)
- Lutz Gärtner
- Department of Otolaryngology, Hannover Medical School, 30625 Hannover, Germany; (L.G.); (K.K.); (T.L.)
| | - Katharina Klötzer
- Department of Otolaryngology, Hannover Medical School, 30625 Hannover, Germany; (L.G.); (K.K.); (T.L.)
| | - Thomas Lenarz
- Department of Otolaryngology, Hannover Medical School, 30625 Hannover, Germany; (L.G.); (K.K.); (T.L.)
- Cluster of Excellence “Hearing4All”, 30625 Hannover, Germany
| | - Verena Scheper
- Department of Otolaryngology, Hannover Medical School, 30625 Hannover, Germany; (L.G.); (K.K.); (T.L.)
- Cluster of Excellence “Hearing4All”, 30625 Hannover, Germany
- Correspondence: ; Tel.: +49-511-532-4369
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17
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Neural Tissue Degeneration in Rosenthal's Canal and Its Impact on Electrical Stimulation of the Auditory Nerve by Cochlear Implants: An Image-Based Modeling Study. Int J Mol Sci 2020; 21:ijms21228511. [PMID: 33198187 PMCID: PMC7697226 DOI: 10.3390/ijms21228511] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/06/2020] [Accepted: 11/09/2020] [Indexed: 11/24/2022] Open
Abstract
Sensorineural deafness is caused by the loss of peripheral neural input to the auditory nerve, which may result from peripheral neural degeneration and/or a loss of inner hair cells. Provided spiral ganglion cells and their central processes are patent, cochlear implants can be used to electrically stimulate the auditory nerve to facilitate hearing in the deaf or severely hard-of-hearing. Neural degeneration is a crucial impediment to the functional success of a cochlear implant. The present, first-of-its-kind two-dimensional finite-element model investigates how the depletion of neural tissues might alter the electrically induced transmembrane potential of spiral ganglion neurons. The study suggests that even as little as 10% of neural tissue degeneration could lead to a disproportionate change in the stimulation profile of the auditory nerve. This result implies that apart from encapsulation layer formation around the cochlear implant electrode, tissue degeneration could also be an essential reason for the apparent inconsistencies in the functionality of cochlear implants.
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18
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Potrusil T, Heshmat A, Sajedi S, Wenger C, Johnson Chacko L, Glueckert R, Schrott-Fischer A, Rattay F. Finite element analysis and three-dimensional reconstruction of tonotopically aligned human auditory fiber pathways: A computational environment for modeling electrical stimulation by a cochlear implant based on micro-CT. Hear Res 2020; 393:108001. [PMID: 32535276 DOI: 10.1016/j.heares.2020.108001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 05/14/2020] [Accepted: 05/23/2020] [Indexed: 01/01/2023]
Abstract
The application of cochlear implants can be studied with computational models. The electrical potential distribution induced by an implanted device is evaluated with a volume conductor model, which is used as input for neuron models to simulate the reaction of cochlear neurons to micro-stimulation. In order to reliably predict the complex excitation profiles it is vital to consider an accurate representation of the human cochlea geometry including detailed three-dimensional pathways of auditory neurons reaching from the organ of Corti through the cochlea-volume. In this study, high-resolution micro-CT imaging (Δx = Δy = Δz = 3 μm) was used to reconstruct the pathways of 30 tonotopically organized nerve fiber bundles, distributed over eight octaves (11500-40 Hz). Results of the computational framework predict: (i) the peripheral process is most sensitive to cathodic stimulation (CAT), (ii) in many cases CAT elicits spikes in the peripheral terminal at threshold but with larger stimuli there is a second spike initiation site within the peripheral process, (iii) anodic stimuli (ANO) can excite the central process even at threshold, (iv) the recruitment of fibers by electrodes located in the narrowing middle- and apical turn is complex and impedes focal excitation of low frequency fibers, (v) degenerated cells which lost the peripheral process are more sensitive to CAT when their somata are totally covered with 2 membranes of a glial cell but they become ANO sensitive when the myelin covering is reduced.
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Affiliation(s)
- Thomas Potrusil
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria
| | - Amirreza Heshmat
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria; TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
| | - Sogand Sajedi
- TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
| | - Cornelia Wenger
- TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
| | - Lejo Johnson Chacko
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria
| | - Rudolf Glueckert
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria
| | - Anneliese Schrott-Fischer
- Innsbruck Medical University, Department of Otorhinolaryngology, Laboratory for Inner Ear Biology, Anichstrasse 35, A-6020, Innsbruck, Austria.
| | - Frank Rattay
- TU Wien, Institute for Analysis and Scientific Computing, Wiedner Hauptstraße 8-10, A- 1040, Vienna, Austria
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19
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Dhanasingh A, N Jolly C, Rajan G, van de Heyning P. Literature Review on the Distribution of Spiral Ganglion Cell Bodies inside the Human Cochlear Central Modiolar Trunk. J Int Adv Otol 2020; 16:104-110. [PMID: 32209520 PMCID: PMC7224428 DOI: 10.5152/iao.2020.7510] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 12/23/2019] [Accepted: 12/26/2019] [Indexed: 11/22/2022] Open
Abstract
This study aims to obtain a better understanding of the number and distribution of spiral ganglion cell bodies (SGCBs) in the central modiolar trunk of the human cochlea with normal hearing as well as with hearing loss due to various pathological conditions. A detailed PubMed search was performed using the key words "human spiral ganglion cell population," "analysis of spiral ganglion cell population," "survival of human spiral ganglion cells," "human Rosenthal's canal," "human ganglion cell counts," and "distribution of human spiral ganglion cells" to identify articles published between 1931 and 2019. The articles were included if the number of SGCBs in the four segments of the human cochlea and angular depth distribution of the SGCBs were mentioned. Out of the 237 articles that were initially identified, 20 articles met the inclusion criteria. The presence of SGCBs inside the Rosenthal's canal (RC) in the modiolar trunk extended to an angular depth of 630°-680°, which is close to the end of the second turn of the cochlea. SGCBs in Segment-IV of the cochlea account for approximately 25-30% of the entire SGCB population, regardless of the cochlear condition (normal vs. pathologic). In normal-hearing subjects, the total number of SGCB cases ranged between 23,910 and 33,702; in patients with hearing loss, the same was between 5,733 and 28,220. This literature review elaborates on the current state of knowledge regarding the number and distribution of SGCBs in the human cochlea.
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Affiliation(s)
| | | | - Gunesh Rajan
- Klinik für Hals, Nasen, Ohren (HNO), Luzerner Kantonsspital, Luzern, Switzerland
| | - Paul van de Heyning
- Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University Hospital, Antwerp, Belgium
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20
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Kleinlogel S, Vogl C, Jeschke M, Neef J, Moser T. Emerging approaches for restoration of hearing and vision. Physiol Rev 2020; 100:1467-1525. [DOI: 10.1152/physrev.00035.2019] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Impairments of vision and hearing are highly prevalent conditions limiting the quality of life and presenting a major socioeconomic burden. For long, retinal and cochlear disorders have remained intractable for causal therapies, with sensory rehabilitation limited to glasses, hearing aids, and electrical cochlear or retinal implants. Recently, the application of gene therapy and optogenetics to eye and ear has generated hope for a fundamental improvement of vision and hearing restoration. To date, one gene therapy for the restoration of vision has been approved and undergoing clinical trials will broaden its application including gene replacement, genome editing, and regenerative approaches. Moreover, optogenetics, i.e. controlling the activity of cells by light, offers a more general alternative strategy. Over little more than a decade, optogenetic approaches have been developed and applied to better understand the function of biological systems, while protein engineers have identified and designed new opsin variants with desired physiological features. Considering potential clinical applications of optogenetics, the spotlight is on the sensory systems. Multiple efforts have been undertaken to restore lost or hampered function in eye and ear. Optogenetic stimulation promises to overcome fundamental shortcomings of electrical stimulation, namely poor spatial resolution and cellular specificity, and accordingly to deliver more detailed sensory information. This review aims at providing a comprehensive reference on current gene therapeutic and optogenetic research relevant to the restoration of hearing and vision. We will introduce gene-therapeutic approaches and discuss the biotechnological and optoelectronic aspects of optogenetic hearing and vision restoration.
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Affiliation(s)
| | | | | | | | - Tobias Moser
- Institute for Auditory Neuroscience, University Medical Center Goettingen, Germany
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21
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Polarity Sensitivity as a Potential Correlate of Neural Degeneration in Cochlear Implant Users. J Assoc Res Otolaryngol 2020; 21:89-104. [PMID: 32020417 DOI: 10.1007/s10162-020-00742-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 01/16/2020] [Indexed: 12/19/2022] Open
Abstract
Cochlear implant (CI) performance varies dramatically between subjects. Although the causes of this variability remain unclear, the electrode-neuron interface is thought to play an important role. Here we evaluate the contribution of two parameters of this interface on the perception of CI listeners: the electrode-to-modiolar wall distance (EMD), estimated from cone-beam computed tomography (CT) scans, and a measure of neural health. Since there is no objective way to quantify neural health in CI users, we measure stimulus polarity sensitivity, which is assumed to be related to neural degeneration, and investigate whether it also correlates with subjects' performance in speech recognition and spectro-temporal modulation detection tasks. Detection thresholds were measured in fifteen CI users (sixteen ears) for partial-tripolar triphasic pulses having an anodic or a cathodic central phase. The polarity effect was defined as the difference in threshold between cathodic and anodic stimuli. Our results show that both the EMD and the polarity effect correlate with detection thresholds, both across and within subjects, although the within-subject correlations were weak. Furthermore, the mean polarity effect, averaged across all electrodes for each subject, was negatively correlated with performance on a spectro-temporal modulation detection task. In other words, lower cathodic thresholds were associated with better spectro-temporal modulation detection performance, which is also consistent with polarity sensitivity being a marker of neural degeneration. Implications for the design of future subject-specific fitting strategies are discussed.
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22
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Kaur C, Saini S, Pal I, Kumar P, Chandra Sati H, Jacob TG, Bhardwaj DN, Roy TS. Age-related changes in the number of cresyl-violet-stained, parvalbumin and NMDAR 2B expressing neurons in the human spiral ganglion. Hear Res 2020; 388:107883. [PMID: 31981822 DOI: 10.1016/j.heares.2020.107883] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 12/12/2019] [Accepted: 12/31/2019] [Indexed: 01/11/2023]
Abstract
Animal-studies associate age-related hearing loss (presbycusis) with decreasing number of spiral ganglion neurons (SGNs) in Rosenthal's canal (RC) of cochlea. The excitatory neurotransmitter for SGNs is glutamate (through its receptor NMDAR 2B), which can be neurotoxic through Ca2+ overload. Neurotoxicity is balanced by calcium-binding proteins (CBPs) like Parvalbumin (PV), which is the predominant CBP of the SGNs. To estimate the volume of the RC and total number of SGNs that are immunoreactive to PV and NMDAR 2B, we used unbiased stereology in 35 human cochleae derived from cadavers of persons from 2nd to 8th decade of life (subsequently statistically divided into two groups) and compared them to the total number of cresyl violet (CV) stained SGNs. We also estimated the volume of individual neurons and their nuclei. Regression analysis was made on estimated parameters against age. Hierarchical-cluster analysis was done on the neuronal against neuronal nuclear volumes.The average volume of the RC did not change with increasing age (p = 0.4115). The total number of SGNs (CV-stained and those separately expressing PV and NMDAR 2B) significantly decreased with age (p < 0.001). We identified three distinct populations of neurons on the basis of their volumes among SGNs. Thus, there is significant age-related decline in the total number of SGNs, which starts early in life. It may be due to ambient noise and inadequate neutralisation of excitotoxicity.
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Affiliation(s)
- Charanjeet Kaur
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Shubhi Saini
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Indra Pal
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Punit Kumar
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Hem Chandra Sati
- Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Tony George Jacob
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Daya Nand Bhardwaj
- Department of Forensic Medicine and Toxicology, All India Institute of Medical Sciences, New Delhi, 110029, India.
| | - Tara Sankar Roy
- Department of Anatomy, All India Institute of Medical Sciences, New Delhi, 110029, India.
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23
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Dhanasingh AE, Rajan G, van de Heyning P. Presence of the spiral ganglion cell bodies beyond the basal turn of the human cochlea. Cochlear Implants Int 2019; 21:145-152. [PMID: 31771498 DOI: 10.1080/14670100.2019.1694226] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The purpose of this study was to obtain a better understanding of the number and distribution of spiral ganglion cell bodies (SGCB) in the central modiolus trunk of the human cochlea with normal hearing as well as with hearing loss due to various pathological conditions. A literature review was performed using the key words 'human spiral ganglion cell population', 'analysis of spiral ganglion cell population', 'survival of human spiral ganglion cells', 'human Rosenthal's canal', 'human ganglion cell counts', and 'distribution of human spiral ganglion cells' to identify articles published between 1968 and 2018. Articles were included if the number of SGCB in the four segments of the human cochlea and angular depth distribution of the SGCB were stated. Of 236 articles initially identified, 19 articles met the inclusion criteria. SGCB inside the Rosenthal's canal (RC) in the modiolus trunk extended to an angular depth of 630-680° which is near the end of the second turn of the cochlea. SGCBs in Segment IV of the cochlea account for approximately 25-30% of the entire SGCB population irrespective of the cochlear condition (normal vs. pathologic). In normal hearing subjects, the total number of SGCB ranged between 23,910 and 33,702 and in patients with hearing loss between 5733 and 28,220. This literature review elaborates on the current state of knowledge about the number and distribution of SGCB in the human cochlea.
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Affiliation(s)
| | - Gunesh Rajan
- Klinik für Hals, Nasen, Ohren (HNO), Luzerner Kantonsspital, Luzern, Switzerland
| | - Paul van de Heyning
- Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University Hospital, Antwerp, Belgium
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24
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Ohlemiller KK. Mouse methods and models for studies in hearing. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:3668. [PMID: 31795658 DOI: 10.1121/1.5132550] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Laboratory mice have become the dominant animal model for hearing research. The mouse cochlea operates according to standard "mammalian" principles, uses the same cochlear cell types, and exhibits the same types of injury as found in other mammals. The typical mouse lifespan is less than 3 years, yet the age-associated pathologies that may be found are quite similar to longer-lived mammals. All Schuknecht's types of presbycusis have been identified in existing mouse lines, some favoring hair cell loss while others favor strial degeneration. Although noise exposure generally affects the mouse cochlea in a manner similar to other mammals, mice appear more prone to permanent alterations to hair cells or the organ of Corti than to hair cell loss. Therapeutic compounds may be applied systemically or locally through the tympanic membrane or onto (or through) the round window membrane. The thinness of the mouse cochlear capsule and annular ligament may promote drug entry from the middle ear, although an extremely active middle ear lining may quickly remove most drugs. Preclinical testing of any therapeutic will always require tests in multiple animal models. Mice constitute one model providing supporting evidence for any therapeutic, while genetically engineered mice can test hypotheses about mechanisms.
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Affiliation(s)
- Kevin K Ohlemiller
- Department of Otolaryngology, Central Institute for the Deaf at Washington University School of Medicine, Washington University School of Medicine, Fay and Carl Simons Center for Hearing and Deafness, Saint Louis, Missouri 63110, USA
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25
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Hügl S, Scheper V, Gepp MM, Lenarz T, Rau TS, Schwieger J. Coating stability and insertion forces of an alginate-cell-based drug delivery implant system for the inner ear. J Mech Behav Biomed Mater 2019; 97:90-98. [DOI: 10.1016/j.jmbbm.2019.05.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 04/01/2019] [Accepted: 05/03/2019] [Indexed: 12/20/2022]
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26
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Pinyon JL, von Jonquieres G, Crawford EN, Duxbury M, Al Abed A, Lovell NH, Klugmann M, Wise AK, Fallon JB, Shepherd RK, Birman CS, Lai W, McAlpine D, McMahon C, Carter PM, Enke YL, Patrick JF, Schilder AG, Marie C, Scherman D, Housley GD. Neurotrophin gene augmentation by electrotransfer to improve cochlear implant hearing outcomes. Hear Res 2019; 380:137-149. [DOI: 10.1016/j.heares.2019.06.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/07/2019] [Accepted: 06/12/2019] [Indexed: 12/14/2022]
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Abstract
Hearing loss is present in millions of people worldwide. Current treatment for patients with severe to profound hearing loss consists of cochlear implantation. Providing the cochlear nerve is intact, patients generally benefit greatly from this intervention, frequently achieving significant improvements in speech comprehension. There are, however, some cases where current technology does not provide patients with adequate benefit. Ongoing research in cell transplantation and gene therapy promises to lead to new developments that will improve the function of cochlear implants. Translation of these experimental approaches is presently at an early stage. This review focuses on the application of biological therapies in severe hearing loss and discusses some of the barriers to translating basic scientific research into clinical reality. We emphasize the application of these novel therapies to cochlear implantation.
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Affiliation(s)
- A Roemer
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Germany.
| | - H Staecker
- Department of Otolaryngology - Head and Neck Surgery, University of Kansas School of Medicine, Kansas City, KS, USA
| | - S Sasse
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - T Lenarz
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
| | - A Warnecke
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Germany
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Dhanasingh A. Why Pre-Curved Modiolar Hugging Electrodes Only Cover The Basal Turn of The Cochlea and Not Beyond that? J Int Adv Otol 2018; 14:376-381. [PMID: 30644378 PMCID: PMC6354519 DOI: 10.5152/iao.2018.5831] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 09/14/2018] [Accepted: 09/14/2018] [Indexed: 11/22/2022] Open
Abstract
The question of why pre-curved modiolar hugging (MH) electrodes only cover the basal turn of the cochlea and not beyond that is unanswered yet in the CI field. Therefore the aim of this article is to show what the practical limitations are with the pre-curved MH electrode design in not being able to fabricate beyond one full turn. Every CI electrode design needs a metal mold with grooves for placing the platinum wires and for injecting with the silicone elastomer. Limitations in making a mold with groove that goes beyond one full turn of curvature along with the mechanical deformation of the curved silicone elastomer, prevents making a pre-curved MH electrode beyond one full turn. Electrode tip fold-over, electrode scalar deviation and the inconsistent electrode to modiolus wall proximity are the reported issues with this electrode type which does not help by any means to the operating surgeon and the pediatric candidates especially. If intra-operative imaging is recommended to confirm the proper placement of the electrode for one particular electrode design, then how many clinics in the world may have this facility and is it ethical to put the patient under more radiation risk are the natural questions that needs to be answered in the interest of the patient. Every CI brand should come out of their marketing philosophy and innovate what is essential in bringing the full benefit of the device to the patients.
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Glueckert R, Johnson Chacko L, Schmidbauer D, Potrusil T, Pechriggl EJ, Hoermann R, Brenner E, Reka A, Schrott-Fischer A, Handschuh S. Visualization of the Membranous Labyrinth and Nerve Fiber Pathways in Human and Animal Inner Ears Using MicroCT Imaging. Front Neurosci 2018; 12:501. [PMID: 30108474 PMCID: PMC6079228 DOI: 10.3389/fnins.2018.00501] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 07/03/2018] [Indexed: 12/18/2022] Open
Abstract
Design and implantation of bionic implants for restoring impaired hair cell function relies on accurate knowledge about the microanatomy and nerve fiber pathways of the human inner ear and its variation. Non-destructive isotropic imaging of soft tissues of the inner ear with lab-based microscopic X-ray computed tomography (microCT) offers high resolution but requires contrast enhancement using compounds with high X-ray attenuation. We evaluated different contrast enhancement techniques in mice, cat, and human temporal bones to differentially visualize the membranous labyrinth, sensory epithelia, and their innervating nerves together with the facial nerve and middle ear. Lugol’s iodine potassium iodine (I2KI) gave high soft tissue contrast in ossified specimens but failed to provide unambiguous identification of smaller nerve fiber bundles inside small bony canals. Fixation or post-fixation with osmium tetroxide followed by decalcification in EDTA provided superior contrast for nerve fibers and membranous structures. We processed 50 human temporal bones and acquired microCT scans with 15 μm voxel size. Subsequently we segmented sensorineural structures and the endolymphatic compartment for 3D representations to serve for morphometric variation analysis. We tested higher resolution image acquisition down to 3.0 μm voxel size in human and 0.5 μm in mice, which provided a unique level of detail and enabled us to visualize single neurons and hair cells in the mouse inner ear, which could offer an alternative quantitative analysis of cell numbers in smaller animals. Bigger ossified human temporal bones comprising the middle ear and mastoid bone can be contrasted with I2KI and imaged in toto at 25 μm voxel size. These data are suitable for surgical planning for electrode prototype placements. A preliminary assessment of geometric changes through tissue processing resulted in 1.6% volume increase caused during decalcification by EDTA and 0.5% volume increase caused by partial dehydration to 70% ethanol, which proved to be the best mounting medium for microCT image acquisition.
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Affiliation(s)
- Rudolf Glueckert
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria.,University Clinics Innsbruck, Tirol Kliniken, University Clinic for Ear, Nose and Throat Medicine Innsbruck, Innsbruck, Austria
| | - Lejo Johnson Chacko
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Dominik Schmidbauer
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria.,Department of Biotechnology and Food Engineering, Management Center Innsbruck (MCI), Innsbruck, Austria
| | - Thomas Potrusil
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - Elisabeth J Pechriggl
- Department of Anatomy, Histology and Embryology, Division of Clinical and Functional Anatomy, Medical University of Innsbruck, Innsbruck, Austria
| | - Romed Hoermann
- Department of Anatomy, Histology and Embryology, Division of Clinical and Functional Anatomy, Medical University of Innsbruck, Innsbruck, Austria
| | - Erich Brenner
- Department of Anatomy, Histology and Embryology, Division of Clinical and Functional Anatomy, Medical University of Innsbruck, Innsbruck, Austria
| | - Alen Reka
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | | | - Stephan Handschuh
- VetImaging, VetCore Facility for Research, University of Veterinary Medicine, Vienna, Austria
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Glueckert R, Johnson Chacko L, Rask-Andersen H, Liu W, Handschuh S, Schrott-Fischer A. Anatomical basis of drug delivery to the inner ear. Hear Res 2018; 368:10-27. [PMID: 30442227 DOI: 10.1016/j.heares.2018.06.017] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 06/16/2018] [Accepted: 06/25/2018] [Indexed: 12/19/2022]
Abstract
The isolated anatomical position and blood-labyrinth barrier hampers systemic drug delivery to the mammalian inner ear. Intratympanic placement of drugs and permeation via the round- and oval window are established methods for local pharmaceutical treatment. Mechanisms of drug uptake and pathways for distribution within the inner ear are hard to predict. The complex microanatomy with fluid-filled spaces separated by tight- and leaky barriers compose various compartments that connect via active and passive transport mechanisms. Here we provide a review on the inner ear architecture at light- and electron microscopy level, relevant for drug delivery. Focus is laid on the human inner ear architecture. Some new data add information on the human inner ear fluid spaces generated with high resolution microcomputed tomography at 15 μm resolution. Perilymphatic spaces are connected with the central modiolus by active transport mechanisms of mesothelial cells that provide access to spiral ganglion neurons. Reports on leaky barriers between scala tympani and the so-called cortilymph compartment likely open the best path for hair cell targeting. The complex barrier system of tight junction proteins such as occludins, claudins and tricellulin isolates the endolymphatic space for most drugs. Comparison of relevant differences of barriers, target cells and cell types involved in drug spread between main animal models and humans shall provide some translational aspects for inner ear drug applications.
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Affiliation(s)
- R Glueckert
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria; University Clinics Innsbruck, Tirol Kliniken, University Clinic for Ear, Nose and Throat Medicine Innsbruck, Austria.
| | - L Johnson Chacko
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
| | - H Rask-Andersen
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, SE-751 85, Uppsala, Sweden
| | - W Liu
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, SE-751 85, Uppsala, Sweden
| | - S Handschuh
- VetImaging, VetCore Facility for Research, University of Veterinary Medicine, Vienna, Austria
| | - A Schrott-Fischer
- Department of Otolaryngology, Medical University of Innsbruck, Innsbruck, Austria
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Sriperumbudur KK, Pau HW, van Rienen U. Effect of Tissue Heterogeneity on the Transmembrane Potential of Type-1 Spiral Ganglion Neurons: A Simulation Study. IEEE Trans Biomed Eng 2018; 65:658-668. [DOI: 10.1109/tbme.2017.2700361] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Using Electrically-evoked Compound Action Potentials to Estimate Perceptive Levels in Experienced Adult Cochlear Implant Users. Otol Neurotol 2017; 38:1278-1289. [PMID: 28834942 DOI: 10.1097/mao.0000000000001548] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS The cochlear implant (CI) fitting level prediction accuracy of electrically-evoked compound action potential (ECAP) should be enhanced by the addition of demographic data in models. INTRODUCTION No accurate automated fitting of CI based on ECAP has yet been proposed. METHODS We recorded ECAP in 45 adults who had been using MED-EL CIs for more than 11 months and collected the most comfortable loudness level (MCL) used for CI fitting (prog-MCL), perception thresholds (meas-THR), and MCL (meas-MCL) measured with the stimulation used for ECAP recording. Linear mixed models taking into account cochlear site factors were computed to explain prog-MCL, meas-MCL, and meas-THR. RESULTS Cochlear region and ECAP threshold were predictors of the three levels. In addition, significant predictors were the ECAP amplitude for the prog-MCL and the duration of deafness for the prog-MCL and the meas-THR. Estimations were more accurate for the meas-THR, then the meas-MCL, and finally the prog-MCL. CONCLUSION These results show that 1) ECAP thresholds are more closely related to perception threshold than to comfort level, 2) predictions are more accurate when the inter-subject and cochlear regions variations are considered, and 3) differences between the stimulations used for ECAP recording and for CI fitting make it difficult to accurately predict the prog-MCL from the ECAP recording. Predicted prog-MCL could be used as bases for fitting but should be used with care to avoid any uncomfortable or painful stimulation.
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Roemer A, Staecker H, Sasse S, Lenarz T, Warnecke A. [Biological therapies in otology. German version]. HNO 2017; 65:571-585. [PMID: 28204850 DOI: 10.1007/s00106-016-0304-x] [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: 11/30/2022]
Abstract
Millions of people worldwide suffer from hearing loss. Current treatment for patients with severe to profound hearing loss consists of cochlear implants. Providing the cochlear nerve is intact, patients generally benefit enormously from this intervention, frequently achieving significant improvements in speech comprehension. There are, however, some cases where current technology does not provide patients with adequate benefit. New therapeutic concepts based on cell transplantation and gene therapy are developing rapidly, at least in the research sector. Compared to the wealth of basic research available in this area, translation of these new experimental approaches into clinical application is presently at a very early stage. The current review focuses on translatable treatment concepts and discusses the barriers that need to be overcome in order to translate basic scientific research into clinical reality. Furthermore, the first examples of clinical application of biological therapies in severe hearing loss are presented, particularly in connection with cochlear implants.
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Affiliation(s)
- A Roemer
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500 Hannover Medical School, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Deutschland.
| | - H Staecker
- Department of Otolaryngology - Head and Neck Surgery, University of Kansas School of Medicine, Kansas City, KS, USA
| | - S Sasse
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500 Hannover Medical School, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Deutschland
| | - T Lenarz
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500 Hannover Medical School, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Deutschland
| | - A Warnecke
- Klinik für Hals-Nasen-Ohren-Heilkunde OE 6500 Hannover Medical School, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Deutschland
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Ohlemiller KK, Jones SM, Johnson KR. Application of Mouse Models to Research in Hearing and Balance. J Assoc Res Otolaryngol 2016; 17:493-523. [PMID: 27752925 PMCID: PMC5112220 DOI: 10.1007/s10162-016-0589-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 09/15/2016] [Indexed: 01/10/2023] Open
Abstract
Laboratory mice (Mus musculus) have become the major model species for inner ear research. The major uses of mice include gene discovery, characterization, and confirmation. Every application of mice is founded on assumptions about what mice represent and how the information gained may be generalized. A host of successes support the continued use of mice to understand hearing and balance. Depending on the research question, however, some mouse models and research designs will be more appropriate than others. Here, we recount some of the history and successes of the use of mice in hearing and vestibular studies and offer guidelines to those considering how to apply mouse models.
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Affiliation(s)
- Kevin K Ohlemiller
- Department of Otolaryngology, Central Institute for the Deaf, Fay and Carl Simons Center for Hearing and Deafness, Washington University School of Medicine, 660 S. Euclid, Saint Louis, MO, 63110, USA.
| | - Sherri M Jones
- Department of Special Education and Communication Disorders, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA
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Munjal T, Roy AT, Carver C, Jiradejvong P, Limb CJ. Use of the Phantom Electrode strategy to improve bass frequency perception for music listening in cochlear implant users. Cochlear Implants Int 2016; 16 Suppl 3:S121-8. [PMID: 26561883 DOI: 10.1179/1467010015z.000000000270] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVES The Phantom Electrode strategy makes use of partial bipolar stimulation on the two most apical electrodes in an effort to extend the frequency range available to cochlear implant (CI) users. This study aimed to quantify the effect of the Phantom Electrode strategy on bass frequency perception in music listening in CI users. METHODS Eleven adult Advanced Bionics users with the Fidelity 120 processing strategy and 16 adult normal hearing (NH) individuals participated in the study. All subjects completed the CI-multiple stimulus with hidden reference and anchor (MUSHRA), a test of an individual's ability to make discriminations in sound quality following the removal of bass frequency information. NH participants completed the CI-MUSHRA once, whereas CI users completed the task twice - once with their baseline clinical program and once with the Phantom Electrode strategy, in random order. CI users' performance was assessed in comparison with NH performance. RESULTS The Phantom Electrode strategy improved CI users performance on the CI-MUSHRA compared with Fidelity 120. DISCUSSION Creation of a Phantom Electrode percept through partial bipolar stimulation of the two most apical electrodes appears to improve CI users' perception of bass frequency information in music, contributing to greater accuracy in the ability to detect alterations in musical sound quality. CONCLUSION The Phantom Electrode processing strategy may enhance the experience of listening to music and thus acoustic stimuli more broadly by improving perception of bass frequencies, through direction of current towards the apical portion of the cochlea beyond the termination of the electrode.
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Schwieger J, Esser KH, Lenarz T, Scheper V. Establishment of a long-term spiral ganglion neuron culture with reduced glial cell number: Effects of AraC on cell composition and neurons. J Neurosci Methods 2016; 268:106-16. [DOI: 10.1016/j.jneumeth.2016.05.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 04/29/2016] [Accepted: 05/02/2016] [Indexed: 01/13/2023]
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Hilly O, Smith L, Hwang E, Shipp D, Symons S, Nedzelski JM, Chen JM, Lin VYW. Depth of Cochlear Implant Array Within the Cochlea and Performance Outcome. Ann Otol Rhinol Laryngol 2016; 125:886-892. [PMID: 27443343 DOI: 10.1177/0003489416660111] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To evaluate whether the depth of cochlear implant array within the cochlea affects performance outcomes 1 year following cochlear implantation. METHODS A retrospective case review of 120 patients who were implanted with the Advanced Bionics HiFocus 1J. Post-implantation plain-radiographs were retrospectively reviewed, and the depth of insertion was measured in degrees from the round window to the electrode tip. Correlation between the depth of insertion and 1-year post-activation Hearing in Noise Test (HINT) scores was analyzed. Intrascala position was not assessed. RESULTS Depth of electrode insertion ranged from 180° to 720°, and HINT scores ranged from 0% to 100%. A Mann-Whitney U test demonstrated significantly improved 1-year post-activation HINT scores in patients with an insertion depth of 360° or more in comparison with patients with insertion depth of less than 360° (81% vs 61%, P = .048). Patients with 13 to 15 contacts within cochlear turns performed as well as patients with full insertion of all 16 contacts, while patients with only 12 contacts performed poorly. CONCLUSIONS Insertion depth of the AB HiFocus 1J electrode of less than 360° is associated with reduced 1-year post-activation HINT scores when compared with deeper insertions. Partial insertion of 13 active contacts or more led to similar results as full insertion.
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Affiliation(s)
- Ohad Hilly
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada Department of Otolaryngology and Head and Neck Surgery, Rabin Medical Center, Tel Aviv University, Tel Aviv, Israel
| | - Leah Smith
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada
| | - Euna Hwang
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada
| | - David Shipp
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada
| | - Sean Symons
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada Department of Medical Imaging, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada
| | - Julian M Nedzelski
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada
| | - Joseph M Chen
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada
| | - Vincent Y W Lin
- Department of Otolaryngology and Head and Neck Surgery, Sunnybrook Health Sciences Centre, University of Toronto, Toronto. ON, Canada
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Kurioka T, Lee MY, Heeringa AN, Beyer LA, Swiderski DL, Kanicki AC, Kabara LL, Dolan DF, Shore SE, Raphael Y. Selective hair cell ablation and noise exposure lead to different patterns of changes in the cochlea and the cochlear nucleus. Neuroscience 2016; 332:242-57. [PMID: 27403879 DOI: 10.1016/j.neuroscience.2016.07.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 06/14/2016] [Accepted: 07/01/2016] [Indexed: 01/21/2023]
Abstract
In experimental animal models of auditory hair cell (HC) loss, insults such as noise or ototoxic drugs often lead to secondary changes or degeneration in non-sensory cells and neural components, including reduced density of spiral ganglion neurons, demyelination of auditory nerve fibers and altered cell numbers and innervation patterns in the cochlear nucleus (CN). However, it is not clear whether loss of HCs alone leads to secondary degeneration in these neural components of the auditory pathway. To elucidate this issue, we investigated changes of central components after cochlear insults specific to HCs using diphtheria toxin receptor (DTR) mice expressing DTR only in HCs and exhibiting complete HC loss when injected with diphtheria toxin (DT). We showed that DT-induced HC ablation has no significant impacts on the survival of auditory neurons, central synaptic terminals, and myelin, despite complete HC loss and profound deafness. In contrast, noise exposure induced significant changes in synapses, myelin and CN organization even without loss of inner HCs. We observed a decrease of neuronal size in the auditory pathway, including peripheral axons, spiral ganglion neurons, and CN neurons, likely due to loss of input from the cochlea. Taken together, selective HC ablation and noise exposure showed different patterns of pathology in the auditory pathway and the presence of HCs is not essential for the maintenance of central synaptic connectivity and myelination.
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Affiliation(s)
- Takaomi Kurioka
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA; Department of Otorhinolaryngology-Head and Neck Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan
| | - Min Young Lee
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Amarins N Heeringa
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa A Beyer
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Donald L Swiderski
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Ariane C Kanicki
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Lisa L Kabara
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - David F Dolan
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Susan E Shore
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Yehoash Raphael
- Kresge Hearing Research Institute, Department of Otolaryngology-Head and Neck Surgery, University of Michigan, Ann Arbor, MI, USA.
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Hellberg V, Gahm C, Liu W, Ehrsson H, Rask-Andersen H, Laurell G. Immunohistochemical localization of OCT2 in the cochlea of various species. Laryngoscope 2015; 125:E320-5. [PMID: 25892279 PMCID: PMC5132114 DOI: 10.1002/lary.25304] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Revised: 01/30/2015] [Accepted: 03/09/2015] [Indexed: 12/20/2022]
Abstract
Objective To locate the organic cation transporter 2 (OCT2) in the cochlea of three different species and to modulate the ototoxicity of cisplatin in the guinea pig by pretreatment with phenformin, having a known affinity for OCT2. Study Design Immunohistochemical and in vivo study. Methods Sections from the auditory end organs were subjected to immunohistochemical staining in order to identify OCT2 in cochlea from untreated rats, guinea pigs, and a pig. In the in vivo study, guinea pigs were given phenformin intravenously 30 minutes before cisplatin administration. Electrophysiological hearing thresholds were determined, and hair cells loss was assessed 96 hours later. The total amount of platinum in cochlear tissue was determined using mass spectrometry. Results Organic cation transporter 2 was found in the supporting cells and in type I spiral ganglion cells in the cochlea of all species studied. Pretreatment with phenformin did not reduce the ototoxic side effect of cisplatin. Furthermore, the concentration of platinum in the cochlea was not affected by phenformin. Conclusions The localization of OCT2 in the supporting cells and type I spiral ganglion cells suggests that this transport protein is not primarily involved in cisplatin uptake from the systemic circulation. We hypothesize that OCT2 transport intensifies cisplatin ototoxicity via transport mechanisms in alternate compartments of the cochlea. Level of Evidence N/A. Laryngoscope, 125:E320–E325, 2015
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Affiliation(s)
| | - Caroline Gahm
- Department of Clinical Science, Intervention and Technology
| | - Wei Liu
- Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - Hans Ehrsson
- Karolinska Pharmacy, Karolinska University Hospital, Stockholm
| | | | - Göran Laurell
- Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
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Effects of electrode position on spatiotemporal auditory nerve fiber responses: a 3D computational model study. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2015; 2015:934382. [PMID: 25755675 PMCID: PMC4338381 DOI: 10.1155/2015/934382] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 01/11/2015] [Accepted: 01/13/2015] [Indexed: 11/17/2022]
Abstract
A cochlear implant (CI) is an auditory prosthesis that enables hearing by providing electrical stimuli through an electrode array. It has been previously established that the electrode position can influence CI performance. Thus, electrode position should be considered in order to achieve better CI results. This paper describes how the electrode position influences the auditory nerve fiber (ANF) response to either a single pulse or low- (250 pulses/s) and high-rate (5,000 pulses/s) pulse-trains using a computational model. The field potential in the cochlea was calculated using a three-dimensional finite-element model, and the ANF response was simulated using a biophysical ANF model. The effects were evaluated in terms of the dynamic range, stochasticity, and spike excitation pattern. The relative spread, threshold, jitter, and initiated node were analyzed for single-pulse response; and the dynamic range, threshold, initiated node, and interspike interval were analyzed for pulse-train stimuli responses. Electrode position was found to significantly affect the spatiotemporal pattern of the ANF response, and this effect was significantly dependent on the stimulus rate. We believe that these modeling results can provide guidance regarding perimodiolar and lateral insertion of CIs in clinical settings and help understand CI performance.
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Liu W, Edin F, Atturo F, Rieger G, Löwenheim H, Senn P, Blumer M, Schrott-Fischer A, Rask-Andersen H, Glueckert R. The pre- and post-somatic segments of the human type I spiral ganglion neurons--structural and functional considerations related to cochlear implantation. Neuroscience 2014; 284:470-482. [PMID: 25316409 PMCID: PMC4300406 DOI: 10.1016/j.neuroscience.2014.09.059] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 09/24/2014] [Accepted: 09/25/2014] [Indexed: 12/21/2022]
Abstract
Human auditory nerve afferents consist of two separate systems; one is represented by the large type I cells innervating the inner hair cells and the other one by the small type II cells innervating the outer hair cells. Type I spiral ganglion neurons (SGNs) constitute 96% of the afferent nerve population and, in contrast to other mammals, their soma and pre- and post-somatic segments are unmyelinated. Type II nerve soma and fibers are unmyelinated. Histopathology and clinical experience imply that human SGNs can persist electrically excitable without dendrites, thus lacking connection to the organ of Corti. The biological background to this phenomenon remains elusive. We analyzed the pre- and post-somatic segments of the type I human SGNs using immunohistochemistry and transmission electron microscopy (TEM) in normal and pathological conditions. These segments were found surrounded by non-myelinated Schwann cells (NMSCs) showing strong intracellular expression of laminin-β2/collagen IV. These cells also bordered the perikaryal entry zone and disclosed surface rugosities outlined by a folded basement membrane (BM) expressing laminin-β2 and collagen IV. It is presumed that human large SGNs are demarcated by three cell categories: (a) myelinated Schwann cells, (b) NMSCs and (c) satellite glial cells (SGCs). Their BMs express laminin-β2/collagen IV and reaches the BM of the sensory epithelium at the habenula perforata. We speculate that the NMSCs protect SGNs from further degeneration following dendrite loss. It may give further explanation why SGNs can persist as electrically excitable monopolar cells even after long-time deafness, a blessing for the deaf treated with cochlear implantation.
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Affiliation(s)
- W Liu
- Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden; Department of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden.
| | - F Edin
- Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden; Department of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden.
| | - F Atturo
- Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden; Department of Neurology, Mental Health and Sensory Organs, Otorhinolaryngologic Unit, Medicine and Psychology, Sapienza, Rome, Italy.
| | - G Rieger
- Department of Otolaryngology, Medical University of Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria.
| | - H Löwenheim
- Department of Otorhinolaryngology-Head & Neck Surgery, European Medical School, University of Oldenburg, Steinweg 13-17, 26122 Oldenburg, Germany.
| | - P Senn
- University Department of ORL, Head & Neck Surgery, Inselspital and Department of Clinical Research, University of Bern, Switzerland; University Department of ORL, Head & Neck Surgery, HUG, Geneva, Switzerland.
| | - M Blumer
- Department of Anatomy, Histology and Embryology, Division of Clinical and Functional Anatomy, Medical University of Innsbruck, Müllerstrasse 59, 6020 Innsbruck, Austria.
| | - A Schrott-Fischer
- Department of Otolaryngology, Medical University of Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria.
| | - H Rask-Andersen
- Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden; Department of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden.
| | - R Glueckert
- Department of Otolaryngology, Medical University of Innsbruck, Anichstrasse 35, A-6020 Innsbruck, Austria.
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Kale S, Cervantes VM, Wu MR, Pisano DV, Sheth N, Olson ES. A novel perfusion-based method for cochlear implant electrode insertion. Hear Res 2014; 314:33-41. [PMID: 24882641 DOI: 10.1016/j.heares.2014.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 05/07/2014] [Accepted: 05/18/2014] [Indexed: 10/25/2022]
Abstract
A cochlear implant (CI) restores partial hearing to profoundly deaf individuals. CI electrodes are inserted manually in the cochlea and surgeons rely on tactile feedback from the implant to determine when to stop the insertion. This manual insertion method results in a large degree of variability in surgical outcomes and intra-cochlear trauma. Additionally, implants often span only the basal turn. In the present study we report on the development of a new method to assist CI electrode insertion. The design objectives are (1) an automated and standardized insertion technique across patients with (2) more apical insertion than is possible by the contemporary methods, while (3) minimizing insertion trauma. The method relies on a viscous fluid flow through the cochlea to carry the electrode array with it. A small cochleostomy (∼100-150 um in diameter) is made in scala vestibuli (SV) and the round window (RW) membrane is opened. A flow of diluted Sodium Hyaluronate (also known as Hyaluronic Acid, (HA)) is set up from the RW to the SV opening using a perfusion pump that sets up a unidirectional flow. Once the flow is established an implant is dropped into the ongoing flow. Here we present a proof-of-concept study where we used this technique to insert silicone implants all the way to the cochlear apex in rats and gerbils. In light-microscopic histology, the implantation occurred without cochlear trauma. To further assess the ototoxicity of the HA perfusion, we measured compound action potential (CAP) thresholds following the perfusion of HA, and found that the CAP thresholds were substantially elevated. Thus, at this point the method is promising, and requires further development to become clinically viable.
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Affiliation(s)
- Sushrut Kale
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, NY 10032, USA.
| | - Vanessa M Cervantes
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, NY 10032, USA
| | - Mailing R Wu
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, NY 10032, USA; Department of Biomedical Engineering, Columbia University, New York, NY 10025, USA
| | - Dominic V Pisano
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, NY 10032, USA
| | - Nakul Sheth
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, NY 10032, USA
| | - Elizabeth S Olson
- Department of Otolaryngology-Head & Neck Surgery, Columbia University, New York, NY 10032, USA; Department of Biomedical Engineering, Columbia University, New York, NY 10025, USA
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Edin F, Liu W, Boström M, Magnusson PU, Rask-Andersen H. Differentiation of human neural progenitor cell-derived spiral ganglion-like neurons: a time-lapse video study. Acta Otolaryngol 2014; 134:441-7. [PMID: 24702223 DOI: 10.3109/00016489.2013.875220] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
CONCLUSIONS Human neural progenitor cells can differentiate into spiral ganglion-like cells when exposed to inner ear-associated growth factors. The phenotype bears resemblance to human sphere-derived neurons. OBJECTIVE To establish an in vitro model for the human auditory nerve to replace and complement in vivo animal experiments and ultimately human in vivo transplantation. METHODS Human neural progenitors were differentiated under conditions developed for in vitro survival of human primary spiral ganglion culture with media containing growth factors associated with inner ear development. Differentiation was documented using time-lapse video microscopy. Time-dependent marker expression was evaluated using immunocytochemistry with fluorescence and laser confocal microscopy. RESULTS Within 14 days of differentiation, neural progenitors adopted neural phenotype and expressed spiral ganglion-associated markers.
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Affiliation(s)
- Fredrik Edin
- Department of Surgical Sciences, Section for Otolaryngology and Head- and Neck surgery, Uppsala University and Uppsala University Hospital
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Nehmé A, El Zir E, Moukarzel N, Haidar H, Vanpoucke F, Arnold L. Measures of the electrically evoked compound action potential threshold and slope in HiRes 90KTMusers. Cochlear Implants Int 2014; 15:53-60. [DOI: 10.1179/1754762813y.0000000039] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Possible role of gap junction intercellular channels and connexin 43 in satellite glial cells (SGCs) for preservation of human spiral ganglion neurons : A comparative study with clinical implications. Cell Tissue Res 2013; 355:267-78. [PMID: 24241398 PMCID: PMC3921454 DOI: 10.1007/s00441-013-1735-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 09/19/2013] [Indexed: 12/22/2022]
Abstract
Human spiral ganglion (SG) neurons show remarkable survival properties and maintain electric excitability for a long time after complete deafness and even separation from the organ of Corti, features essential for cochlear implantation. Here, we analyze and compare the localization and distribution of gap junction (GJ) intercellular channels and connexin 43 (Cx43) in cells surrounding SG cell bodies in man and guinea pig by using transmission electron microscopy and confocal immunohistochemistry. GJs and Cx43 expression has been recognized in satellite glial cells (SGCs) in non-myelinating sensory ganglia including the human SG. In man, SG neurons can survive as mono-polar or "amputated" cells with unbroken central projections following dendrite degeneration and consolidation of the dendrite pole. Cx43-mediated GJ signaling between SGCs is believed to play a key role in this "healing" process and could explain the unique preservation of human SG neurons and the persistence of cochlear implant function.
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Rattay F, Potrusil T, Wenger C, Wise AK, Glueckert R, Schrott-Fischer A. Impact of morphometry, myelinization and synaptic current strength on spike conduction in human and cat spiral ganglion neurons. PLoS One 2013; 8:e79256. [PMID: 24260179 PMCID: PMC3832640 DOI: 10.1371/journal.pone.0079256] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 09/20/2013] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Our knowledge about the neural code in the auditory nerve is based to a large extent on experiments on cats. Several anatomical differences between auditory neurons in human and cat are expected to lead to functional differences in speed and safety of spike conduction. METHODOLOGY/PRINCIPAL FINDINGS Confocal microscopy was used to systematically evaluate peripheral and central process diameters, commonness of myelination and morphology of spiral ganglion neurons (SGNs) along the cochlea of three human and three cats. Based on these morphometric data, model analysis reveales that spike conduction in SGNs is characterized by four phases: a postsynaptic delay, constant velocity in the peripheral process, a presomatic delay and constant velocity in the central process. The majority of SGNs are type I, connecting the inner hair cells with the brainstem. In contrast to those of humans, type I neurons of the cat are entirely myelinated. Biophysical model evaluation showed delayed and weak spikes in the human soma region as a consequence of a lack of myelin. The simulated spike conduction times are in accordance with normal interwave latencies from auditory brainstem response recordings from man and cat. Simulated 400 pA postsynaptic currents from inner hair cell ribbon synapses were 15 times above threshold. They enforced quick and synchronous spiking. Both of these properties were not present in type II cells as they receive fewer and much weaker (∼26 pA) synaptic stimuli. CONCLUSIONS/SIGNIFICANCE Wasting synaptic energy boosts spike initiation, which guarantees the rapid transmission of temporal fine structure of auditory signals. However, a lack of myelin in the soma regions of human type I neurons causes a large delay in spike conduction in comparison with cat neurons. The absent myelin, in combination with a longer peripheral process, causes quantitative differences of temporal parameters in the electrically stimulated human cochlea compared to the cat cochlea.
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Affiliation(s)
- Frank Rattay
- Institute for Analysis and Scientific Computing, Vienna University of Technology, Vienna, Austria
| | - Thomas Potrusil
- Department of Otorhinolaryngology, Innsbruck Medical University, Innsbruck, Austria
- Faculty of Informatics, Vienna University of Technology, Vienna, Austria
| | - Cornelia Wenger
- Institute of Biophysics and Biomedical Engeneering, Faculty of Science, University of Lisbon, Lisbon, Portugal
| | | | - Rudolf Glueckert
- Department of Otorhinolaryngology, Innsbruck Medical University, Innsbruck, Austria
- University Clinics Innsbruck, Tiroler Landeskrankenanstalten, Innsbruck, Austria
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Sheep as a large animal model for middle and inner ear implantable hearing devices: a feasibility study in cadavers. Otol Neurotol 2012; 33:481-9. [PMID: 22410732 DOI: 10.1097/mao.0b013e318248ee3a] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
OBJECTIVE Currently, no large animal model exists for surgical-experimental exploratory analysis of implantable hearing devices. In a histomorphometric study, we sought to investigate whether sheep or pig cochleae are suitable for this purpose and whether device implantation is feasible. METHODS Skulls of pig and sheep cadavers were examined using high-resolution 128-slice computed tomography (CT) to study anatomic relationships. A cochlear implant and an active middle ear implant could be successfully implanted into the sheep's inner and middle ear, respectively. Correct device placement was verified by CT and histology. The cochlear anatomy of the sheep was further studied by micro-CT and histology. RESULTS Our investigations indicate that the sheep is a suitable animal model for implantation of implantable hearing devices. The implantation of the devices was successfully performed by access through a mastoidectomy. The histologic, morphologic, and micro-CT study of the sheep cochlea showed that it is highly similar to the human cochlea. The temporal bone of the pig was not suitable for these microsurgical procedures because the middle and inner ear were not accessible owing to distinct soft and fatty tissue coverage of the mastoid. CONCLUSION The sheep is an appropriate large animal model for experimental studies with implantable hearing devices, whereas the pig is not.
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Morphometric classification and spatial organization of spiral ganglion neurons in the human cochlea: consequences for single fiber response to electrical stimulation. Neuroscience 2012; 214:120-35. [PMID: 22516012 PMCID: PMC3377987 DOI: 10.1016/j.neuroscience.2012.03.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 02/13/2012] [Accepted: 03/11/2012] [Indexed: 11/20/2022]
Abstract
The unique, unmyelinated perikarya of spiral ganglion cells (SGCs) in the human cochlea are often arranged in functional units covered by common satellite glial cells. This micro anatomical peculiarity presents a crucial barrier for an action potential (AP) travelling from the sensory receptors to the brain. Confocal microscopy was used to acquire systematically volumetric data on perikarya and corresponding nuclei in their full dimension along the cochlea of two individuals. Four populations of SGCs within the human inner ear of two different specimens were identified using agglomerative hierarchical clustering, contrary to the present distinction of two groups of SGCs. Furthermore, we found evidence of a spatial arrangement of perikarya and their accordant nuclei along the cochlea spiral. In this arrangement, the most uniform sizes of cell bodies are located in the middle turn, which represents the majority of phonational frequencies. Since single-cell recordings from other mammalians may not be representative to humans and human SGCs are not accessible for physiological measurements, computer simulation has been used to quantify the effect of varying soma size on single neuron response to electrical micro stimulation. Results show that temporal parameters of the spiking pattern are affected by the size of the cell body. Cathodic stimulation was found to induce stronger variations of spikes while also leading to the lowest thresholds and longest latencies. Therefore, anodic stimulation leads to a more uniform excitation profile among SGCs with different cell body size.
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Abstract
OBJECTIVES This review examines evidence for potential benefits of using cochlear implant electrodes that extend into the apical regions of the cochlea. Most cochlear implant systems use electrode arrays that extend 1 to 1.5 turns from the basal cochleostomy, but one manufacturer (MED-EL GmbH) uses an electrode array that is considerably longer. The fundamental rationale for using electrodes extending toward the apex of the cochlea is to provide additional low-pitched auditory percepts and thereby increase the spectral information available to the user. Several experimental long arrays have also been produced by other manufacturers to assess potential benefits of this approach. DESIGN In addition to assessing the effects of deeply inserted electrodes on performance, this review examines several underlying and associated issues, including cochlear anatomy, electrode design, surgical considerations (including insertion trauma), and pitch scaling trials. Where possible, the aim is to draw conclusions regarding the potential from apical electrodes in general, rather than relating to the performance of specific and current devices. RESULTS Imaging studies indicate that currently available electrode arrays rarely extend more than two turns into the cochlea, the mean insertion angle for full insertions of the MED-EL electrodes being about 630°. This is considerably shorter than the total length of the cochlea and more closely approximates the length of the spiral ganglion. Anatomical considerations, and some modelling studies, suggest that fabrication of even longer electrodes is unlikely to provide additional spectral information. The issue of potential benefit from the most apical electrodes, therefore, is whether they are able to selectively stimulate discrete and tonotopically ordered neural populations near the apex of the spiral ganglion, where the ganglion cells are closely grouped. Pitch scaling studies, using the MED-EL and experimental long arrays, suggest that this is achieved in many cases, but that a significant number of individuals show evidence of pitch confusions or reversals among the most apical electrodes, presumably reducing potential performance benefit and presenting challenges for processor programming. CONCLUSIONS Benefits in terms of speech recognition and other performance measures are less clear. Several studies have indicated that deactivation of apical electrodes results in poorer speech recognition performance, but these have been mostly acute studies where the subjects have been accustomed to the full complement of electrodes, thus making interpretation difficult. Some chronic studies have suggested that apical electrodes do provide additional performance benefit, but others have shown performance improvement after deactivating some of the apical electrodes. Whether or not deeply inserted electrodes can offer performance benefits, there is evidence that currently available designs tend to produce more intracochlear trauma than shorter arrays, in terms of loss of residual acoustic hearing and reduction of the neural substrate. This may have important long-term consequences for the user. Furthermore, as it is possible that subjects with better low-frequency residual hearing are more likely to benefit from the inclusion of apical electrodes, there may be a potential clinical dilemma as the same subjects are those most likely to benefit from bimodal electroacoustic stimulation, requiring a relatively shallow insertion.
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Liu W, Boström M, Kinnefors A, Linthicum F, Rask-Andersen H. Expression of myelin basic protein in the human auditory nerve - an immunohistochemical and comparative study. Auris Nasus Larynx 2011; 39:18-24. [PMID: 21601398 DOI: 10.1016/j.anl.2011.04.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Revised: 04/20/2011] [Accepted: 04/22/2011] [Indexed: 11/28/2022]
Abstract
OBJECTIVE The aim of this study is to analyse the expression and distribution of myelin basic protein (MBP or Myelin A1 protein) in the human spiral ganglion and auditory nerve. MATERIALS AND METHODS Cryostat sections were made from freshly fixed human cochlear specimens removed at surgery in patients with life-threatening petro-clival meningiomas compressing the brain stem. The sections were subjected to immunohistochemistry using antibodies against MBP, S-100 and Tubulin. The immunoreaction was documented using laser confocal microscopy. RESULTS Type I spiral ganglion nerve somata (SGN) were surrounded by so-called "satellite glial cells" (SGCs) that lacked expression of MBP consistent with earlier light and electron microscopic findings indicating that these cells are non-myelinating. S-100 labeling showed that the SGCs form a continuous network in the apical region. CONCLUSIONS The pattern of myelination in human spiral ganglion is different from that in other species' spiral ganglion. The striking differences in myelin outline should be investigated further in combination with its influence on signal coding and preservation properties in man.
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Affiliation(s)
- Wei Liu
- Dept. of Otolaryngology, Uppsala University Hospital, 75185 Uppsala, Sweden.
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