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Waring NA, Chern A, Vilarello BJ, Cheng YS, Zhou C, Lang JH, Olson ES, Nakajima HH. Hampshire Sheep as a Large-Animal Model for Cochlear Implantation. J Assoc Res Otolaryngol 2024; 25:277-284. [PMID: 38622382 PMCID: PMC11150341 DOI: 10.1007/s10162-024-00946-1] [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: 09/01/2023] [Accepted: 03/28/2024] [Indexed: 04/17/2024] Open
Abstract
BACKGROUND Sheep have been proposed as a large-animal model for studying cochlear implantation. However, prior sheep studies report that the facial nerve (FN) obscures the round window membrane (RWM), requiring FN sacrifice or a retrofacial opening to access the middle-ear cavity posterior to the FN for cochlear implantation. We investigated surgical access to the RWM in Hampshire sheep compared to Suffolk-Dorset sheep and the feasibility of Hampshire sheep for cochlear implantation via a facial recess approach. METHODS Sixteen temporal bones from cadaveric sheep heads (ten Hampshire and six Suffolk-Dorset) were dissected to gain surgical access to the RWM via an extended facial recess approach. RWM visibility was graded using St. Thomas' Hospital (STH) classification. Cochlear implant (CI) electrode array insertion was performed in two Hampshire specimens. Micro-CT scans were obtained for each temporal bone, with confirmation of appropriate electrode array placement and segmentation of the inner ear structures. RESULTS Visibility of the RWM on average was 83% in Hampshire specimens and 59% in Suffolk-Dorset specimens (p = 0.0262). Hampshire RWM visibility was Type I (100% visibility) for three specimens and Type IIa (> 50% visibility) for seven specimens. Suffolk-Dorset RWM visibility was Type IIa for four specimens and Type IIb (< 50% visibility) for two specimens. FN appeared to course more anterolaterally in Suffolk-Dorset specimens. Micro-CT confirmed appropriate CI electrode array placement in the scala tympani without apparent basilar membrane rupture. CONCLUSIONS Hampshire sheep appear to be a suitable large-animal model for CI electrode insertion via an extended facial recess approach without sacrificing the FN. In this small sample, Hampshire specimens had improved RWM visibility compared to Suffolk-Dorset. Thus, Hampshire sheep may be superior to other breeds for ease of cochlear implantation, with FN and facial recess anatomy more similar to humans.
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Affiliation(s)
- Nicholas A Waring
- Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
- Department of Otolaryngology-Head & Neck Surgery, NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY, USA
| | - Alexander Chern
- Department of Otolaryngology-Head & Neck Surgery, NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY, USA
| | - Brandon J Vilarello
- Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
- Department of Otolaryngology-Head & Neck Surgery, NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY, USA
| | - Yew Song Cheng
- Department of Otolaryngology-Head & Neck Surgery, University of California San Francisco, San Francisco, CA, USA
| | - Chaoqun Zhou
- Department of Otolaryngology-Head & Neck Surgery, NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY, USA
- Department of Mechanical Engineering, Columbia University, New York, NY, USA
| | - Jeffrey H Lang
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Elizabeth S Olson
- Department of Otolaryngology-Head & Neck Surgery, NewYork-Presbyterian/Columbia University Irving Medical Center, New York, NY, USA.
- Department of Biomedical Engineering, Columbia University, New York, NY, USA.
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Azees AA, Thompson AC, Thomas R, Zhou J, Ruther P, Wise AK, Ajay EA, Garrett DJ, Quigley A, Fallon JB, Richardson RT. Spread of activation and interaction between channels with multi-channel optogenetic stimulation in the mouse cochlea. Hear Res 2023; 440:108911. [PMID: 37977051 DOI: 10.1016/j.heares.2023.108911] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 10/19/2023] [Accepted: 11/02/2023] [Indexed: 11/19/2023]
Abstract
For individuals with severe to profound hearing loss resulting from irreversibly damaged hair cells, cochlear implants can be used to restore hearing by delivering electrical stimulation directly to the spiral ganglion neurons. However, current spread lowers the spatial resolution of neural activation. Since light can be easily confined, optogenetics is a technique that has the potential to improve the precision of neural activation, whereby visible light is used to stimulate neurons that are modified with light-sensitive opsins. This study compares the spread of neural activity across the inferior colliculus of the auditory midbrain during electrical and optical stimulation in the cochlea of acutely deafened mice with opsin-modified spiral ganglion neurons (H134R variant of the channelrhodopsin-2). Monopolar electrical stimulation was delivered via each of four 0.2 mm wide platinum electrode rings at 0.6 mm centre-to-centre spacing, whereas 453 nm wavelength light was delivered via each of five 0.22 × 0.27 mm micro-light emitting diodes (LEDs) at 0.52 mm centre-to-centre spacing. Channel interactions were also quantified by threshold changes during simultaneous stimulation by pairs of electrodes or micro-LEDs at different distances between the electrodes (0.6, 1.2 and 1.8 mm) or micro-LEDs (0.52, 1.04, 1.56 and 2.08 mm). The spread of activation resulting from single channel optical stimulation was approximately half that of monopolar electrical stimulation as measured at two levels of discrimination above threshold (p<0.001), whereas there was no significant difference between optical stimulation in opsin-modified deafened mice and pure tone acoustic stimulation in normal-hearing mice. During simultaneous micro-LED stimulation, there were minimal channel interactions for all micro-LED spacings tested. For neighbouring micro-LEDs/electrodes, the relative influence on threshold was 13-fold less for optical stimulation compared electrical stimulation (p<0.05). The outcomes of this study show that the higher spatial precision of optogenetic stimulation results in reduced channel interaction compared to electrical stimulation, which could increase the number of independent channels in a cochlear implant. Increased spatial resolution and the ability to activate more than one channel simultaneously could lead to better speech perception in cochlear implant recipients.
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Affiliation(s)
- Ajmal A Azees
- The Bionics Institute, East Melbourne, VIC 3002, Australia; Department of Electrical and Biomedical Engineering, RMIT University, Melbourne, VIC 3000, Australia
| | - Alex C Thompson
- The Bionics Institute, East Melbourne, VIC 3002, Australia; Medical Bionics Department, University of Melbourne, East Melbourne, VIC, Australia
| | - Ross Thomas
- The Bionics Institute, East Melbourne, VIC 3002, Australia
| | - Jenny Zhou
- The Bionics Institute, East Melbourne, VIC 3002, Australia
| | - Patrick Ruther
- Department of Microsystems Engineering (IMTEK), University of Freiburg, Freiburg 79110, Germany; BrainLinks-BrainTools Center, University of Freiburg, Freiburg 79110, Germany
| | - Andrew K Wise
- The Bionics Institute, East Melbourne, VIC 3002, Australia; Department of Surgery (Otolaryngology), University of Melbourne, Melbourne, VIC 3002, Australia; Medical Bionics Department, University of Melbourne, East Melbourne, VIC, Australia
| | - Elise A Ajay
- The Bionics Institute, East Melbourne, VIC 3002, Australia; Faculty of Engineering and Information Technology, University of Melbourne, Melbourne, VIC, Australia
| | - David J Garrett
- Department of Electrical and Biomedical Engineering, RMIT University, Melbourne, VIC 3000, Australia
| | - Anita Quigley
- Department of Electrical and Biomedical Engineering, RMIT University, Melbourne, VIC 3000, Australia; Department of Medicine, University of Melbourne, St Vincent's Hospital, Melbourne, VIC 3065, Australia; The Aikenhead Centre for Medical Discovery, St Vincent's Hospital, Melbourne, VIC 3065, Australia
| | - James B Fallon
- The Bionics Institute, East Melbourne, VIC 3002, Australia; Department of Surgery (Otolaryngology), University of Melbourne, Melbourne, VIC 3002, Australia; Medical Bionics Department, University of Melbourne, East Melbourne, VIC, Australia
| | - Rachael T Richardson
- The Bionics Institute, East Melbourne, VIC 3002, Australia; Department of Surgery (Otolaryngology), University of Melbourne, Melbourne, VIC 3002, Australia; Medical Bionics Department, University of Melbourne, East Melbourne, VIC, Australia.
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Kirk JR, Smyth D, Dueck WF. A new paradigm of hearing loss and preservation with cochlear implants: Learnings from fundamental studies and clinical research. Hear Res 2023; 433:108769. [PMID: 37120894 DOI: 10.1016/j.heares.2023.108769] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 02/18/2023] [Accepted: 04/15/2023] [Indexed: 05/02/2023]
Abstract
In 2010 Cochlear initiated a coordinated preclinical research program to identify the factors and underlying mechanisms of acoustic hearing loss following cochlear implantation and device use. At its inception the program was structured around several major hypotheses implicated in the loss of acoustic hearing. The understanding of causes evolved over the course of the program, leading to an increased appreciation of the role of the biological response in post-implant hearing loss. A systematic approach was developed which mapped the cochlear implant journey along a timeline that considers all events in an individual's hearing history. By evaluating the available data in this context, rather than by discrete hypothesis testing, causative and associated factors may be more readily detected. This approach presents opportunities for more effective research management and may aid in identifying new prospects for intervention. Many of the outcomes of the research program apply beyond preservation of acoustic hearing to factors important to overall cochlear health and considerations for future therapies.
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Affiliation(s)
- Jonathon R Kirk
- Cochlear Limited, 1 University Avenue, Macquarie University, NSW 2109, Australia.
| | - Daniel Smyth
- Cochlear Limited, 1 University Avenue, Macquarie University, NSW 2109, Australia
| | - Wolfram F Dueck
- Cochlear Limited, 1 University Avenue, Macquarie University, NSW 2109, Australia
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