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Fröhlich M, Schurzig D, Rau TS, Lenarz T. On the interdependence of insertion forces, insertion speed, and lubrication: Aspects to consider when testing cochlear implant electrodes. PLoS One 2024; 19:e0295121. [PMID: 38266033 PMCID: PMC10807833 DOI: 10.1371/journal.pone.0295121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Accepted: 11/14/2023] [Indexed: 01/26/2024] Open
Abstract
OBJECTIVES During the insertion of cochlear implant (CI) electrode arrays, forces occur which may cause trauma and poorer hearing outcomes. Unfortunately, research groups investigating factors influencing insertion forces come to contradicting results, especially regarding insertion speed. This study was conducted to investigate the origin of these contradicting results and to determine how different testing conditions influence experimental findings. METHODS Repeated, automated insertions with three different FLEX28 CI electrode arrays (MED-EL, Innsbruck, Austria) were performed into a newly developed, anatomically correct and 3D-printed mean scala tympani phantom. The testing protocol for each electrode included variations in insertion speed (v = 0.1-2.0 mm/s) and lubrication (90%, 50%, and 10% liquid soap), resulting in 51 insertions per electrode array and a total of 153 insertions. RESULTS The test setup and protocol allowed for repeatable insertions with only minimal change in the morphology of the insertion force profiles per testing condition. Strong but varying dependencies of the maximal insertion forces and work were found regarding both lubrication and speed: work-speed dependency is constant for the 10% lubricant, negative for the 50% lubricant and positive for the 90% lubricant. CONCLUSION Our results can explain part of the contradicting results found within previous studies by translating interrelations known from lubricated rubber friction to the field of CI electrode array insertion. We show that the main driver behind measured bulk forces are most likely the generated friction forces, which are strongly dependent on insertion speed and lubrication. The employed test setup allows for conducting repeatable and comparable insertion studies, which can be recapitulated by other centers due to the detailed explanation of the test setup as well as the developed and freely available insertion phantom. This study hence represents another important step toward standardizing CI array insertion testing.
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Affiliation(s)
- Max Fröhlich
- MED-EL Medical Electronics GmbH, MED-EL Research Center, Hannover, Germany
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Daniel Schurzig
- MED-EL Medical Electronics GmbH, MED-EL Research Center, Hannover, Germany
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
| | - Thomas S. Rau
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
- Cluster of Excellence EXC 2177/1 “Hearing4all”, Hannover, Germany
| | - Thomas Lenarz
- Department of Otolaryngology, Hannover Medical School, Hannover, Germany
- Cluster of Excellence EXC 2177/1 “Hearing4all”, Hannover, Germany
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Blanc F, Blanchet C, Sicard M, Merklen F, Venail F, Mondain M. Audiological Outcomes and Associated Factors after Pediatric Cochlear Reimplantation. J Clin Med 2022; 11:jcm11113148. [PMID: 35683535 PMCID: PMC9181352 DOI: 10.3390/jcm11113148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 05/29/2022] [Accepted: 05/30/2022] [Indexed: 12/10/2022] Open
Abstract
Cochlear implants are the most common and successful sensory neuroprosthetic devices. However, reimplantation can be required for medical reasons, device failure, or technological upgrading. Resolving the problem driving the intervention and offering stable or better audiological results are the main challenges. We aimed to analyze the success rate of this intervention and to identify factors influencing speech perception recovery after reimplantation in the pediatric population. We retrospectively collected the causes and the outcomes of 67 consecutive reimplantations in one cochlear implant center over 30 years. Reimplantation resolved the cause without recurrence for 94% of patients. The etiology of deafness, time since implantation, indication of reimplantation, sex, and age did not influence word discrimination test scores in silence, 3 years after surgery. However, adherence to a speech rehabilitation program was statistically associated with gain in perception scores: +8.9% [−2.2; +31.0%] versus −19.0% [−47.5; −7.6%] if no or suboptimal rehabilitation was followed (p = 0.0037). Cochlear reimplantation in children is efficient and is associated with predictable improvement in speech perception, 3 years after intervention. However, good adherence to speech rehabilitation program is necessary and should be discussed with the patient and parents, especially for the indication of reimplantation for technological upgrading.
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Affiliation(s)
- Fabian Blanc
- Department of Otolaryngology and Head and Neck Surgery, Gui de Chauliac Hospital, 80 Avenue Augustin-Fliche, 34090 Montpellier, France; (F.B.); (C.B.); (M.S.); (F.M.); (F.V.)
- Institute for Neurosciences of Montpellier (INM), Institut National de la Santé et de la Recherche Médicale U1289, University of Montpellier, 80 Avenue Augustin-Fliche, BP 74103, CEDEX 5, 34091 Montpellier, France
| | - Catherine Blanchet
- Department of Otolaryngology and Head and Neck Surgery, Gui de Chauliac Hospital, 80 Avenue Augustin-Fliche, 34090 Montpellier, France; (F.B.); (C.B.); (M.S.); (F.M.); (F.V.)
| | - Marielle Sicard
- Department of Otolaryngology and Head and Neck Surgery, Gui de Chauliac Hospital, 80 Avenue Augustin-Fliche, 34090 Montpellier, France; (F.B.); (C.B.); (M.S.); (F.M.); (F.V.)
| | - Fanny Merklen
- Department of Otolaryngology and Head and Neck Surgery, Gui de Chauliac Hospital, 80 Avenue Augustin-Fliche, 34090 Montpellier, France; (F.B.); (C.B.); (M.S.); (F.M.); (F.V.)
| | - Frederic Venail
- Department of Otolaryngology and Head and Neck Surgery, Gui de Chauliac Hospital, 80 Avenue Augustin-Fliche, 34090 Montpellier, France; (F.B.); (C.B.); (M.S.); (F.M.); (F.V.)
- Institute for Neurosciences of Montpellier (INM), Institut National de la Santé et de la Recherche Médicale U1289, University of Montpellier, 80 Avenue Augustin-Fliche, BP 74103, CEDEX 5, 34091 Montpellier, France
| | - Michel Mondain
- Department of Otolaryngology and Head and Neck Surgery, Gui de Chauliac Hospital, 80 Avenue Augustin-Fliche, 34090 Montpellier, France; (F.B.); (C.B.); (M.S.); (F.M.); (F.V.)
- Institute for Neurosciences of Montpellier (INM), Institut National de la Santé et de la Recherche Médicale U1289, University of Montpellier, 80 Avenue Augustin-Fliche, BP 74103, CEDEX 5, 34091 Montpellier, France
- Correspondence:
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Dohr D, Wulf K, Grabow N, Mlynski R, Schraven SP. A PLLA Coating Does Not Affect the Insertion Pressure or Frictional Behavior of a CI Electrode Array at Higher Insertion Speeds. MATERIALS 2022; 15:ma15093049. [PMID: 35591381 PMCID: PMC9104964 DOI: 10.3390/ma15093049] [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: 02/25/2022] [Revised: 04/14/2022] [Accepted: 04/14/2022] [Indexed: 01/27/2023]
Abstract
To prevent endocochlear insertion trauma, the development of drug delivery coatings in the field of CI electrodes has become an increasing focus of research. However, so far, the effect of a polymer coating of PLLA on the mechanical properties, such as the insertion pressure and friction of an electrode array, has not been investigated. In this study, the insertion pressure of a PLLA-coated, 31.5-mm long standard electrode array was examined during placement in a linear cochlear model. Additionally, the friction coefficients between a PLLA-coated electrode array and a tissue simulating the endocochlear lining were acquired. All data were obtained at different insertion speeds (0.1, 0.5, 1.0, 1.5, and 2.0 mm/s) and compared with those of an uncoated electrode array. It was shown that both the maximum insertion pressure generated in the linear model and the friction coefficient of the PLLA-coated electrode did not depend on the insertion speed. At higher insertion speeds above 1.0 mm/s, the insertion pressure (1.268 ± 0.032 mmHg) and the friction coefficient (0.40 ± 0.15) of the coated electrode array were similar to those of an uncoated array (1.252 ± 0.034 mmHg and 0.36 ± 0.15). The present study reveals that a PLLA coating on cochlear electrode arrays has a negligible effect on the electrode array insertion pressure and the friction when higher insertion speeds are used compared with an uncoated electrode array. Therefore, PLLA is a suitable material to be used as a coating for CI electrode arrays and can be considered for a potential drug delivery system.
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Affiliation(s)
- Dana Dohr
- Department of Otorhinolaryngology, Head and Neck Surgery “Otto Körner”, Rostock University Medical Center, 18057 Rostock, Germany; (R.M.); (S.P.S.)
- Correspondence: author
| | - Katharina Wulf
- Institute for Biomedical Engineering, Rostock University Medical Center, 18119 Rostock, Germany; (K.W.); (N.G.)
| | - Niels Grabow
- Institute for Biomedical Engineering, Rostock University Medical Center, 18119 Rostock, Germany; (K.W.); (N.G.)
| | - Robert Mlynski
- Department of Otorhinolaryngology, Head and Neck Surgery “Otto Körner”, Rostock University Medical Center, 18057 Rostock, Germany; (R.M.); (S.P.S.)
| | - Sebastian P. Schraven
- Department of Otorhinolaryngology, Head and Neck Surgery “Otto Körner”, Rostock University Medical Center, 18057 Rostock, Germany; (R.M.); (S.P.S.)
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Frictional Behavior of Cochlear Electrode Array Is Dictated by Insertion Speed and Impacts Insertion Force. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11115162] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Background: During cochlear implantation, the electrode array has significant friction with the sensitive endocochlear lining and causes mutual mechanical trauma while the array is being inserted. Both, the impact of insertion speed on electrode friction and the relationship of electrode insertion force and friction have not been adequately investigated to date. Methods: In this study, friction coefficients between a CI electrode array (31.5 mm) and a tissue simulating the endocochlear lining have been acquired, depending on different insertion speeds (0.1, 0.5, 1.0, 1.5, and 2.0 mm/s). Additionally, the electrode insertion forces during the placing into a scala tympani model were recorded and correlated with the friction coefficient. Results: It was shown that the friction coefficient reached the lowest value at an insertion speed of 0.1 mm/s (0.24 ± 0.13), a maximum occurred at 1.5 mm/s (0.59 ± 0.12), and dropped again at 2 mm/s (0.45 ± 0.11). Similar patterns were observed for the insertion forces. Consequently, a high correlation coefficient (0.9) was obtained between the insertion forces and friction coefficients. Conclusion: The present study reveals a non-linear increase in electrode array friction, when insertion speed raises and reports a high correlation between friction coefficient and electrode insertion force. This dependence is a relevant future parameter to evaluate and reduce cochlear implant insertion trauma. Significance statement: Here, we demonstrated a dependence between cochlear electrode insertion speed and its friction behavior and a high correlation to insertion force. Our study provides valuable information for the evaluation and prevention of cochlear implant insertion trauma and supports the optimization of cochlear electrode arrays regarding friction characteristics.
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Finite Element Modelling of Cochlear Electrode Arrays. JOURNAL OF BIOMIMETICS BIOMATERIALS AND BIOMEDICAL ENGINEERING 2021. [DOI: 10.4028/www.scientific.net/jbbbe.49.47] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The implant of cochlear electrode arrays is standard nowadays as a result of the improvement of medical surgery, equipment, and material properties. In this paper, the finite element modeling FEM will be utilized to characterize the mechanical properties of the electrode arrays. The results show that a good agreement between the finite element results and the experimental. Besides, it shows that no significant difference between the tapered and uniform correctional electrodes.
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Frick C, Fink S, Schmidbauer D, Rousset F, Eickhoff H, Tropitzsch A, Kramer B, Senn P, Glueckert R, Rask-Andersen H, Wiesmüller KH, Löwenheim H, Müller M. Age-Dependency of Neurite Outgrowth in Postnatal Mouse Cochlear Spiral Ganglion Explants. Brain Sci 2020; 10:brainsci10090580. [PMID: 32839381 PMCID: PMC7564056 DOI: 10.3390/brainsci10090580] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Revised: 08/18/2020] [Accepted: 08/19/2020] [Indexed: 12/22/2022] Open
Abstract
Background: The spatial gap between cochlear implants (CIs) and the auditory nerve limits frequency selectivity as large populations of spiral ganglion neurons (SGNs) are electrically stimulated synchronously. To improve CI performance, a possible strategy is to promote neurite outgrowth toward the CI, thereby allowing a discrete stimulation of small SGN subpopulations. Brain-derived neurotrophic factor (BDNF) is effective to stimulate neurite outgrowth from SGNs. Method: TrkB (tropomyosin receptor kinase B) agonists, BDNF, and five known small-molecule BDNF mimetics were tested for their efficacy in stimulating neurite outgrowth in postnatal SGN explants. To modulate Trk receptor-mediated effects, TrkB and TrkC ligands were scavenged by an excess of recombinant receptor proteins. The pan-Trk inhibitor K252a was used to block Trk receptor actions. Results: THF (7,8,3′-trihydroxyflavone) partly reproduced the BDNF effect in postnatal day 7 (P7) mouse cochlear spiral ganglion explants (SGEs), but failed to show effectiveness in P4 SGEs. During the same postnatal period, spontaneous and BDNF-stimulated neurite outgrowth increased. The increased neurite outgrowth in P7 SGEs was not caused by the TrkB/TrkC ligands, BDNF and neurotrophin-3 (NT-3). Conclusions: The age-dependency of induction of neurite outgrowth in SGEs was very likely dependent on presently unidentified factors and/or molecular mechanisms which may also be decisive for the age-dependent efficacy of the small-molecule TrkB receptor agonist THF.
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Affiliation(s)
- Claudia Frick
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen Medical Center, 72076 Tübingen, Germany; (C.F.); (A.T.); (B.K.); (H.L.); (M.M.)
- Department of Microbiome Science, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Stefan Fink
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen Medical Center, 72076 Tübingen, Germany; (C.F.); (A.T.); (B.K.); (H.L.); (M.M.)
- Correspondence: ; Tel.: +49-7071-2988192
| | - Dominik Schmidbauer
- Inner Ear Laboratory Innsbruck, Medical University Innsbruck, 6020 Innsbruck, Austria; (D.S.); (R.G.)
| | - Francis Rousset
- The Inner Ear & Olfaction Lab, Department of Clinical Neurosciences, Faculty of Medicine, University of Geneva, 1206 Geneva, Switzerland; (F.R.); (P.S.)
| | - Holger Eickhoff
- EMC Microcollections GmbH, 72070 Tübingen, Germany; (H.E.); (K.-H.W.)
| | - Anke Tropitzsch
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen Medical Center, 72076 Tübingen, Germany; (C.F.); (A.T.); (B.K.); (H.L.); (M.M.)
| | - Benedikt Kramer
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen Medical Center, 72076 Tübingen, Germany; (C.F.); (A.T.); (B.K.); (H.L.); (M.M.)
- Department of Otolaryngology, Head and Neck Surgery, University Hospital Mannheim, 68167 Mannheim, Germany
| | - Pascal Senn
- The Inner Ear & Olfaction Lab, Department of Clinical Neurosciences, Faculty of Medicine, University of Geneva, 1206 Geneva, Switzerland; (F.R.); (P.S.)
| | - Rudolf Glueckert
- Inner Ear Laboratory Innsbruck, Medical University Innsbruck, 6020 Innsbruck, Austria; (D.S.); (R.G.)
- Tirol Kliniken Innsbruck, University Clinic of Otolaryngology, 6020 Innsbruck, Austria
| | - Helge Rask-Andersen
- Department of Surgical Sciences, Otorhinolaryngology and Head and Neck Surgery, University of Uppsala, 751 85 Uppsala, Sweden;
| | | | - Hubert Löwenheim
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen Medical Center, 72076 Tübingen, Germany; (C.F.); (A.T.); (B.K.); (H.L.); (M.M.)
| | - Marcus Müller
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, University of Tübingen Medical Center, 72076 Tübingen, Germany; (C.F.); (A.T.); (B.K.); (H.L.); (M.M.)
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Stock A, Bozzato V, Kloska SP, Bozzato A, Hoppe U, Hornung J, Dörfler A, Struffert T. Evaluation After Cochlear Implant Surgery : Correlation of Clinical Outcome and Imaging Findings using Flat-detector CT. Clin Neuroradiol 2020; 31:367-372. [PMID: 32556392 PMCID: PMC8410718 DOI: 10.1007/s00062-020-00922-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 05/27/2020] [Indexed: 11/14/2022]
Abstract
Purpose Assessment of the cochlear implant (CI) electrode array position using flat-detector computed tomography (FDCT) to test dependence of postoperative outcome on intracochlear electrode position. Methods A total of 102 patients implanted with 107 CIs underwent FDCT. Electrode position was rated as 1) scala tympani, 2) scala vestibuli, 3) scalar dislocation and 4) no deconvolution. Two independent neuroradiologists rated all image data sets twice and the scalar position was verified by a third neuroradiologist. Presurgical and postsurgical speech audiometry by the Freiburg monosyllabic test was used to evaluate auditory outcome after 6 months of speech rehabilitation. Results Electrode array position was assessed by FDCT in 107 CIs. Of the electrodes 60 were detected in the scala tympani, 21 in the scala vestibuli, 24 electrode arrays showed scalar dislocation and 2 electrodes were not placed in an intracochlear position. There was no significant difference in rehabilitation outcomes between scala tympani and scala vestibuli inserted patients. Rehabilitation was also possible in patients with dislocated electrodes. Conclusion The use of FDCT is a reliable diagnostic method to determine the position of the electrode array. In our study cohort, the electrode position had no significant impact on postoperative outcome except for non-deconvoluted electrode arrays.
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Affiliation(s)
- Annika Stock
- Department of Neuroradiology, University Hospital Erlangen-Nuremberg, Erlangen, Germany. .,Department of Neuroradiology, University Hospital Würzburg, Josef-Schneider-Straße 11, 97080, Würzburg, Germany.
| | - Victoria Bozzato
- Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Saarland Medical School, Homburg, Germany
| | - Stephan P Kloska
- Department of Neuroradiology, University Hospital Erlangen-Nuremberg, Erlangen, Germany.,Department of Radiology, Hospital Fuerth, Fürth, Germany
| | - Alessandro Bozzato
- Department of Otorhinolaryngology, Head and Neck Surgery, University Hospital Saarland Medical School, Homburg, Germany
| | - Ulrich Hoppe
- Department of Otorhinolaryngology, Head & Neck Surgery, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Joachim Hornung
- Department of Otorhinolaryngology, Head & Neck Surgery, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Arnd Dörfler
- Department of Neuroradiology, University Hospital Erlangen-Nuremberg, Erlangen, Germany
| | - Tobias Struffert
- Department of Neuroradiology, University Hospital Erlangen-Nuremberg, Erlangen, Germany.,Department of Neuroradiology, University Hospital Gießen, Gießen, Germany
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Shepherd RK, Villalobos J, Burns O, Nayagam DAX. The development of neural stimulators: a review of preclinical safety and efficacy studies. J Neural Eng 2018; 15:041004. [PMID: 29756600 PMCID: PMC6049833 DOI: 10.1088/1741-2552/aac43c] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Given the rapid expansion of the field of neural stimulation and the rigorous regulatory approval requirements required before these devices can be applied clinically, it is important that there is clarity around conducting preclinical safety and efficacy studies required for the development of this technology. APPROACH The present review examines basic design principles associated with the development of a safe neural stimulator and describes the suite of preclinical safety studies that need to be considered when taking a device to clinical trial. MAIN RESULTS Neural stimulators are active implantable devices that provide therapeutic intervention, sensory feedback or improved motor control via electrical stimulation of neural or neuro-muscular tissue in response to trauma or disease. Because of their complexity, regulatory bodies classify these devices in the highest risk category (Class III), and they are therefore required to go through a rigorous regulatory approval process before progressing to market. The successful development of these devices is achieved through close collaboration across disciplines including engineers, scientists and a surgical/clinical team, and the adherence to clear design principles. Preclinical studies form one of several key components in the development pathway from concept to product release of neural stimulators. Importantly, these studies provide iterative feedback in order to optimise the final design of the device. Key components of any preclinical evaluation include: in vitro studies that are focussed on device reliability and include accelerated testing under highly controlled environments; in vivo studies using animal models of the disease or injury in order to assess efficacy and, given an appropriate animal model, the safety of the technology under both passive and electrically active conditions; and human cadaver and ex vivo studies designed to ensure the device's form factor conforms to human anatomy, to optimise the surgical approach and to develop any specialist surgical tooling required. SIGNIFICANCE The pipeline from concept to commercialisation of these devices is long and expensive; careful attention to both device design and its preclinical evaluation will have significant impact on the duration and cost associated with taking a device through to commercialisation. Carefully controlled in vitro and in vivo studies together with ex vivo and human cadaver trials are key components of a thorough preclinical evaluation of any new neural stimulator.
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Affiliation(s)
- Robert K Shepherd
- Bionics Institute, East Melbourne, Australia. Medical Bionics Department, University of Melbourne, Melbourne, Australia
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Abstract
BACKGROUND There are no data on cochlear duct lengths (CDL) among Middle East populations. OBJECTIVES The main aims of this study were to estimate the average CDL in the Saudi population and to compare it with the reported CDL in other regions/ethnic groups outside the Middle East. DESIGN Retrospective study. SETTING Tertiary otolaryngology head and neck surgery center. SUBJECTS AND METHODS Temporal bone CT scans were reviewed to determine CDL. We excluded any CT scan of an ear with a congenital inner ear anomaly or acquired pathology. MAIN OUTCOME MEASURES CDL. SAMPLE SIZE 441 temporal bone CT scans. RESULTS The overall CDL mean was 31.9 mm (range 20.3-37.7 mm). The cochleae of males was significantly longer than of females and cochleae from the left side were significantly longer than of the right side. No significant difference was found between children and adults. Inter-study comparison revealed a significant difference in CDL between the Saudi population in our study and European and Australian studies, but not between the present study and North American studies. CONCLUSIONS The CDL differed significantly according to side of the cochlea and sex, but not by age. Geographically and ethnically, the mean CDL for Saudis was significantly different from the CDL of subjects of some ethnic backgrounds, but not others. Due to this diversity, we recommend that the CDL be measured before cochlear implant surgery. LIMITATIONS All the measurements were done by one person, and the subjects' physical measurements, such as height or head circumference, were not included. CONFLICT OF INTEREST None.
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Affiliation(s)
- Alaa Alanazi
- Alaa Alanazi, College of Medicne,, King Saud University,, PO Box 245, Riyadh 11411, KSA, alaa.a.alanazi@gmail. com, ORCID: http://orcid.org/0000.0001-8096-9118
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Abstract
OBJECTIVE Recent studies demonstrated the utility of high-resolution computed tomography (HRCT) scans in measuring basal cochlear length and cochlear insertion depths. These studies showed significant variations in the anatomy of the cochlea amongst humans. The aim of our study was to investigate for gender and racial variations in the basal turn length of the human cochlea in an Asian population. METHOD HRCT temporal bone data from year 1997 till 2012 of patients with normally developed cochleae who reported with otologic disease was obtained. Reconstruction of the full basal turn was performed for both ears. The largest distance from the midpoint of the round window, through the midmodiolar axis, to the lateral wall was measured (distance A). Length of the lateral wall of the cochlea to the first turn (360°) was calculated and statistically analyzed. RESULTS HRCT temporal bone data from 161 patients was initially obtained. Four patients were subsequently excluded from the study as they were of various other racial groups. Study group therefore comprised of 157 patients (314 cochleae). Mean distance A was statistically different between the two sides of the ear (right 9.09mm; left 9.06mm; p=0.0069). Significant gender and racial differences were also found. Mean distance A was 9.17mm in males and 8.97mm in females (p=0.0016). The racial groups were Chinese (39%), Malay (38%) and Indian (22%). Between racial groups, mean distance A was 9.11mm (Chinese), 9.11mm (Malays) and 8.99mm (Indians). The mean basal turn lengths ranged from 19.71mm to 25.09mm. With gender factored in, significant variation in mean basal turn lengths was found across all three racial groups (p=0.04). CONCLUSION The view of the basal turn of the cochlea from HRCT is simple to obtain and reproducible. This study found significant differences in basal cochlear length amongst male and female Asian patients, as well as amongst various racial groups. This has implications for cochlear electrode insertion as well as electrode array design.
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Three-Dimensional Force Profile During Cochlear Implantation Depends on Individual Geometry and Insertion Trauma. Ear Hear 2017; 38:e168-e179. [DOI: 10.1097/aud.0000000000000394] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Clifford AR, Gibson WPR. Anatomy of the round Window with Respect to Cochlear Implant Surgery. Ann Otol Rhinol Laryngol 2016. [DOI: 10.1177/00034894870960s106] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Twenty-three human temporal bones were dissected to study the anatomy of the round window with respect to cochlear implantation. Information was also gathered concerning the passage of a 22-channel electrode array along the cochlear duct by using cochlear surface dissection preparations. The insertion length and any insertion trauma were noted both by observation at the time of insertion and by careful analysis of video recordings. The crista semilunaris did not interfere with smooth electrode insertion. The recommendation is made that enlarging the round window anteroinferiorly is unnecessary and potentially hazardous in most cases.
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Clark GM, Pyman BC, Webb RL, Franz BKHG, Redhead TJ, Shepherd RK. Surgery for the Safe Insertion and Reinsertion of the Banded Electrode Array. Ann Otol Rhinol Laryngol 2016. [DOI: 10.1177/00034894870960s102] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Adhering to the surgical technique outlined in the protocol for the Nucleus implant has resulted in over 100 patients worldwide obtaining significant benefit from multichannel stimulation. A detailed analysis of the results in 40 patients shows that it improves their awareness of environmental sounds and their abilities in understanding running speech when combined with lipreading. In addition, one third to one half of the patients also understand significant amounts of running speech without lipreading and some can have interactive conversations over the telephone. It is clear that any insertion trauma is not significant, which is confirmed by the excellent clinical results.
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Frick C, Müller M, Wank U, Tropitzsch A, Kramer B, Senn P, Rask-Andersen H, Wiesmüller KH, Löwenheim H. Biofunctionalized peptide-based hydrogels provide permissive scaffolds to attract neurite outgrowth from spiral ganglion neurons. Colloids Surf B Biointerfaces 2016; 149:105-114. [PMID: 27736723 DOI: 10.1016/j.colsurfb.2016.10.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 09/03/2016] [Accepted: 10/03/2016] [Indexed: 12/15/2022]
Abstract
Cochlear implants (CI) allow for hearing rehabilitation in patients with sensorineural hearing loss or deafness. Restricted CI performance results from the spatial gap between spiral ganglion neurons and the CI, causing current spread that limits spatially restricted stimulation and impairs frequency resolution. This may be substantially improved by guiding peripheral processes of spiral ganglion neurons towards and onto the CI electrode contacts. An injectable, peptide-based hydrogel was developed which may provide a permissive scaffold to facilitate neurite growth towards the CI. To test hydrogel capacity to attract spiral ganglion neurites, neurite outgrowth was quantified in an in vitro model using a custom-designed hydrogel scaffold and PuraMatrix®. Neurite attachment to native hydrogels is poor, but significantly improved by incorporation of brain-derived neurotrophic factor (BDNF), covalent coupling of the bioactive laminin epitope IKVAV and the incorporation a full length laminin to hydrogel scaffolds. Incorporation of full length laminin protein into a novel custom-designed biofunctionalized hydrogel (IKVAV-GGG-SIINFEKL) allows for neurite outgrowth into the hydrogel scaffold. The study demonstrates that peptide-based hydrogels can be specifically biofunctionalized to provide a permissive scaffold to attract neurite outgrowth from spiral ganglion neurons. Such biomaterials appear suitable to bridge the spatial gap between neurons and the CI.
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Affiliation(s)
- Claudia Frick
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Eberhard Karls University Tübingen, DE-72076 Tübingen, Germany.
| | - Marcus Müller
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Eberhard Karls University Tübingen, DE-72076 Tübingen, Germany.
| | - Ute Wank
- EMC microcollections GmbH, DE-72070 Tübingen, Germany.
| | - Anke Tropitzsch
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Eberhard Karls University Tübingen, DE-72076 Tübingen, Germany.
| | - Benedikt Kramer
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Eberhard Karls University Tübingen, DE-72076 Tübingen, Germany.
| | - Pascal Senn
- Department of Clinical Neurosciences, Service of Otorhinolaryngology, Head & Neck Surgery, HUG, University Hospital of Geneva, CH-1211 Genève 14, Switzerland.
| | - Helge Rask-Andersen
- Department of Surgical Sciences, Head and Neck Surgery, Section of Otolaryngology, Uppsala University Hospital, Departments of Otolaryngology, Uppsala University Hospital, SE-751 85 Uppsala, Sweden.
| | | | - Hubert Löwenheim
- Department of Otolaryngology, Head and Neck Surgery, Tübingen Hearing Research Centre, Eberhard Karls University Tübingen, DE-72076 Tübingen, Germany.
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Skinner MW, Holden TA, Whiting BR, Voie AH, Brunsden B, Neely JG, Saxon EA, Hullar TE, Finley CC. In Vivo Estimates of the Position of Advanced Bionics Electrode Arrays in the Human Cochlea. Ann Otol Rhinol Laryngol 2016. [DOI: 10.1177/00034894071160s401] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objectives: A new technique for determining the position of each electrode in the cochlea is described and applied to spiral computed tomography data from 15 patients implanted with Advanced Bionics HiFocus I, Ij, or Helix arrays. Methods: ANALYZE imaging software was used to register 3-dimensional image volumes from patients' preoperative and postoperative scans and from a single body donor whose unimplanted ears were scanned clinically, with micro computed tomography and with orthogonal-plane fluorescence optical sectioning (OPFOS) microscopy. By use of this registration, we compared the atlas of OPFOS images of soft tissue within the body donor's cochlea with the bone and fluid/tissue boundary available in patient scan data to choose the midmodiolar axis position and judge the electrode position in the scala tympani or scala vestibuli, including the distance to the medial and lateral scalar walls. The angular rotation 0° start point is a line joining the midmodiolar axis and the middle of the cochlear canal entry from the vestibule. Results: The group mean array insertion depth was 477° (range, 286° to 655°). The word scores were negatively correlated (r = −0.59; p = .028) with the number of electrodes in the scala vestibuli. Conclusions: Although the individual variability in all measures was large, repeated patterns of suboptimal electrode placement were observed across subjects, underscoring the applicability of this technique.
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Skinner MW, Holden TA, Whiting BR, Voie AH, Brunsden B, Neely JG, Saxon EA, Hullar TE, Finley CC. In Vivo Estimates of the Position of Advanced Bionics Electrode Arrays in the Human Cochlea. Ann Otol Rhinol Laryngol 2016. [DOI: 10.1177/000348940711600401] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Objectives: A new technique for determining the position of each electrode in the cochlea is described and applied to spiral computed tomography data from 15 patients implanted with Advanced Bionics HiFocus I, Ij, or Helix arrays. Methods: ANALYZE imaging software was used to register 3-dimensional image volumes from patients' preoperative and postoperative scans and from a single body donor whose unimplanted ears were scanned clinically, with micro computed tomography and with orthogonal-plane fluorescence optical sectioning (OPFOS) microscopy. By use of this registration, we compared the atlas of OPFOS images of soft tissue within the body donor's cochlea with the bone and fluid/ tissue boundary available in patient scan data to choose the midmodiolar axis position and judge the electrode position in the scala tympani or scala vestibuli, including the distance to the medial and lateral scalar walls. The angular rotation 0° start point is a line joining the midmodiolar axis and the middle of the cochlear canal entry from the vestibule. Results: The group mean array insertion depth was 477° (range, 286° to 655°). The word scores were negatively correlated (r = −0.59; p = .028) with the number of electrodes in the scala vestibuli. Conclusions: Although the individual variability in all measures was large, repeated patterns of suboptimal electrode placement were observed across subjects, underscoring the applicability of this technique.
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17
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Effect of embedded optical fibres on the mechanical properties of cochlear electrode arrays. Med Eng Phys 2016; 38:155-62. [DOI: 10.1016/j.medengphy.2015.11.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 11/11/2015] [Accepted: 11/24/2015] [Indexed: 11/22/2022]
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18
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Ryu KA, Lyu AR, Park H, Choi JW, Hur GM, Park YH. Intracochlear Bleeding Enhances Cochlear Fibrosis and Ossification: An Animal Study. PLoS One 2015; 10:e0136617. [PMID: 26308864 PMCID: PMC4550248 DOI: 10.1371/journal.pone.0136617] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Accepted: 07/12/2015] [Indexed: 12/22/2022] Open
Abstract
The aim of this study was to investigate the effects of intracochlear bleeding during cochleostomy on cochlear inflammatory response and residual hearing in a guinea pig animal model. Auditory brainstem response threshold shifts were greater in blood injected ears (p<0.05). Interleukin-1β, interleukin-10, tumor necrosis factor-α and nitric oxide synthase 2, cytokines that are related to early stage inflammation, were significantly increased in blood injected ears compared to normal and cochleostomy only ears at 1 day after surgery; with the increased IL-1β being sustained until 3 days after the surgery (p<0.05). Hair cells were more severely damaged in blood injected ears than in cochleostomy only ears. Histopathologic examination revealed more extensive fibrosis and ossification in blood injected ears than cochleostomy only ears. These results show that intracochlear bleeding enhanced cochlear inflammation resulting in increased fibrosis and ossification in an experimental animal model.
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Affiliation(s)
- Kyeung A. Ryu
- Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Ah-Ra Lyu
- Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Heesung Park
- Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Jin Woong Choi
- Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Gang Min Hur
- Department of Pharmacology, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
| | - Yong-Ho Park
- Department of Otolaryngology-Head and Neck Surgery, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
- Brain Research Institute, College of Medicine, Chungnam National University, Daejeon, Republic of Korea
- * E-mail:
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Cochlear length determination using Cone Beam Computed Tomography in a clinical setting. Hear Res 2014; 316:65-72. [DOI: 10.1016/j.heares.2014.07.013] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Revised: 07/14/2014] [Accepted: 07/29/2014] [Indexed: 10/24/2022]
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Wade SA, Fallon JB, Wise AK, Shepherd RK, James NL, Stoddart PR. Measurement of Forces at the Tip of a Cochlear Implant During Insertion. IEEE Trans Biomed Eng 2014; 61:1177-86. [DOI: 10.1109/tbme.2013.2296566] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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22
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Clark G. The multi-channel cochlear implant: Past, present and future perspectives. Cochlear Implants Int 2013; 10 Suppl 1:2-13. [DOI: 10.1179/cim.2009.10.supplement-1.2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Tykocinski M, Cowan RSC. Poly-vinyl-alcohol (PVA) coating of cochlear implant electrode arrays: an in-vivo biosafety study. Cochlear Implants Int 2013; 6:16-30. [DOI: 10.1179/cim.2005.6.1.16] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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24
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Kha H, Chen B. Finite element analysis of damage by cochlear implant electrode array's proximal section to the basilar membrane. Otol Neurotol 2013; 33:1176-80. [PMID: 22872176 DOI: 10.1097/mao.0b013e318263545f] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
HYPOTHESIS This study aims to examine the mechanism of damage to the basilar membrane caused by the proximal section of the cochlear implant electrode array. BACKGROUND The electrode array has been found to severely damage the basilar membrane. Most previous studies on cochlear implant insertion damage largely focused on the injury by the front section (tip) of the electrode array to the membrane. Little attempt has been made to investigate the damage caused by the array's proximal section. METHODS A computational model using the finite element method has been developed for assessing the likelihood of the damage based on two criteria: 1) frequency of contact between the proximal section of the electrode array and the upper wall of the scala tympani where the basilar membrane is located, and 2) magnitude of the associated shear stresses at the contact areas. The model has been validated and used for studying the effect of electrode array's stiffness properties on the damage. RESULTS The proximal section of the contour array is most likely to hit the basilar membrane, compared with its previous versions (the straight array and the single wire electrode). In terms of shear stress magnitude, the proximal section of the contour array exerts higher stresses on the scala tympani's upper wall and, thus, is more likely to damage the basilar membrane, compared with that of the straight array. CONCLUSION Results from this study are useful for cochlear implant surgeons in better understanding the mechanism of damage by the electrode array's proximal section to the basilar membrane and in establishing advanced insertion techniques for reducing the damage (in particular, the results strongly support the "advance off-stylet" technique). The outcomes of the study also are beneficial for cochlear implant designers in selecting appropriate stiffness profiles for future electrode arrays, which are expected to cause minimal damage to the basilar membrane (a new design of the contour array with stiffness increasing from the front to the proximal section is highly recommended).
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Affiliation(s)
- Hung Kha
- College of Engineering and Computer Science, Australian National University, Acton, Canberra, Australia.
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25
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Richard C, Fayad JN, Doherty J, Linthicum FH. Round window versus cochleostomy technique in cochlear implantation: histologic findings. Otol Neurotol 2012; 33:1181-7. [PMID: 22892806 PMCID: PMC3425957 DOI: 10.1097/mao.0b013e318263d56d] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS Cochleostomy or round window enlargement techniques for cochlear implant electrode insertion result in more abnormal tissue formation in the basal cochlea and are more apt to produce endolymphatic hydrops than round window electrode insertion. METHODS Twelve temporal bones from implanted patients were examined under light microscopy and reconstructed with 3-dimensional reconstruction software to determine cochlear damage and volume of neo-ossification and fibrosis after electrode insertion. Amount of new tissue was compared between 3 groups of bones: insertion through the round window (RW), after enlarging the RW (RWE) and cochleostomy (Cochl). The probable role of the electrode was evaluated in each case with hydrops. RESULTS More initial damage occurred in the Cochl and RWE groups than in the RW group, and the difference was significant between RWE and RW in cochlear segment I (p < 0.026). The volume of new bone in Segment I differed significantly between groups (p < 0.012) and was greater in the RWE group than in either the Cochl or RW groups (post hoc p's < 0.035 and 0.019, respectively). Hydrops was seen in 5 cases, all in the Cochl and RWE groups. Blockage of the duct was because of new tissue formation in 4 of the 5 hydrops cases. CONCLUSION With the electrodes in this series, implantation through the RW minimized initial intracochlear trauma and subsequent new tissue formation, whereas the RW extension technique used at the time of these implantations produced the greatest damage. Future studies may clarify whether today's techniques and electrodes will produce these same patterns of damage.
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Affiliation(s)
- Céline Richard
- Research Scholar, House Research Institute, Los Angeles; CHU of St Etienne, University of Saint -Etienne, France
| | - Jose N. Fayad
- House Clinic and House Research Institute; Keck School of Medicine of the University of Southern California
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Development of a surgical approach for a wide-view suprachoroidal retinal prosthesis: evaluation of implantation trauma. Graefes Arch Clin Exp Ophthalmol 2011; 250:399-407. [PMID: 21874343 DOI: 10.1007/s00417-011-1794-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Revised: 07/12/2011] [Accepted: 07/28/2011] [Indexed: 10/17/2022] Open
Abstract
BACKGROUND Our research goal is to develop a safe, reproducible surgical approach for implantation of a wide-field retinal stimulating array. The aim of this study was to evaluate the pathological response to acute implantation of a functional prototype electrode array in the suprachoroidal space. METHODS The surgical techniques to implant a 72 platinum electrode array fabricated on 8 × 13 × 0.4 mm polyimide and silicone substrate were developed in a pilot study in anesthetized cats. For the main study, nine eyes were implanted in vivo and unoperated eyes were used as controls. Surgery consisted of a temporal approach with a full-thickness scleral incision 5 mm posterior to the limbus. A suprachoroidal "pocket" was created, the electrode array inserted to sit beneath the area centralis, and placement was confirmed visually. The eyes were collected subsequently for histopathology. RESULTS The array was consistently inserted into the suprachoroidal space beneath the area centralis in nine eyes. There was a significant hemorrhage in two cases where implantation was complicated by choroidal congestion. Retinal folding occurred only when the array tip was within 2.6 mm of the optic disc (p < 0.01). There was choroidal incarceration at the incision in six eyes and scleral distortion at the array edges in five. No cases were found where the implant breached the retina, choroid, or sclera. CONCLUSIONS A large stimulation array can be reliably inserted into the suprachoroidal space without trauma to the neuroretina. These findings suggest that this is an appropriate surgical approach for the placement of an electrode array for use in retinal stimulation.
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von Ilberg CA, Baumann U, Kiefer J, Tillein J, Adunka OF. Electric-Acoustic Stimulation of the Auditory System: A Review of the First Decade. ACTA ACUST UNITED AC 2011; 16 Suppl 2:1-30. [DOI: 10.1159/000327765] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Accepted: 02/21/2011] [Indexed: 11/19/2022]
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Briggs RJ, Tykocinski M, Saunders E, Hellier W, Dahm M, Pyman B, Clark GM. Surgical implications of perimodiolar cochlear implant electrode design: avoiding intracochlear damage and scala vestibuli insertion. Cochlear Implants Int 2009; 2:135-49. [PMID: 18792095 DOI: 10.1179/cim.2001.2.2.135] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
OBJECTIVE To review the mechanisms and nature of intracochlear damage associated with cochlear implant electrode array insertion, in particular, the various perimodiolar electrode designs. Make recommendations regarding surgical techniques for the Nucleus Contour electrode to ensure correct position and minimal insertion trauma. BACKGROUND The potential advantages of increased modiolar proximity of intracochlear multichannel electrode arrays are a reduction in stimulation thresholds, an increase in dynamic range and more localized neural excitation. This may improve speech perception and reduce power consumption. These advantages may be negated if increased intracochlear damage results from the method used to position the electrodes close to the modiolus. METHOD A review of the University of Melbourne Department of Otolaryngology experience with temporal bone safety studies using the Nucleus standard straight electrode array and a variety of perimodiolar electrode array designs; comparison with temporal bone insertion studies from other centres and postmortem histopathology studies reported in the literature. Review of our initial clinical experience using the Nucleus Contour electrode array. RESULTS The nature of intracochlear damage resulting from electrode insertion trauma ranges from minor, localized, spiral ligament tear to diffuse organ of Corti disruption and osseous spiral lamina fracture. The type of damage depends on the mechanical characteristics of the electrode array, the stiffness, curvature and size of the electrode in relation to the scala, and the surgical technique. The narrow, flexible, straight arrays are the least traumatic. Pre-curved or stiffer arrays are associated with an incidence of basilar membrane perforation. The cochleostomy must be correctly sited in relation to the round window to ensure scala tympani insertion. A cochleostomy anterior to the round window rather than inferior may lead to scala media or scala vestibuli insertion. CONCLUSION Proximity of electrodes to the modiolus can be achieved without intracochlear damage provided the electrode array is a free fit within the scala, of appropriate size and shape, and accurate scala tympani insertion is performed.
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Affiliation(s)
- R J Briggs
- Department of Otolaryngology, Cooperative Research Centre for Cochlear Implant and Hearing Aid Innovation, The University of Melbourne, Australia.
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Abstract
HYPOTHESIS Suboptimal cochlear implant (CI) electrode array placement may reduce presentation of coded information to the central nervous system and, consequently, limit speech recognition. BACKGROUND Generally, mean speech reception scores for CI recipients are similar across different CI systems, yet large outcome variation is observed among recipients implanted with the same device. These observations suggest significant recipient-dependent factors influence speech reception performance. This study examines electrode array insertion depth and scalar placement as recipient-dependent factors affecting outcome. METHODS Scalar location and depth of insertion of intracochlear electrodes were measured in 14 patients implanted with Advanced Bionics electrode arrays and whose word recognition scores varied broadly. Electrode position was measured using computed tomographic images of the cochlea and correlated with stable monosyllabic word recognition scores. RESULTS Electrode placement, primarily in terms of depth of insertion and scala tympani versus scala vestibuli location, varies widely across subjects. Lower outcome scores are associated with greater insertion depth and greater number of contacts being located in scala vestibuli. Three patterns of scalar placement are observed suggesting variability in insertion dynamics arising from surgical technique. CONCLUSION A significant portion of variability in word recognition scores across a broad range of performance levels of CI subjects is explained by variability in scalar location and insertion depth of the electrode array. We suggest that this variability in electrode placement can be reduced and average speech reception improved by better selection of cochleostomy sites, revised insertion approaches, and control of insertion depth during surgical placement of the array.
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Clark G. The multi-channel cochlear implant: Past, present and future perspectives. Cochlear Implants Int 2009. [DOI: 10.1002/cii.378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Todd CA, Naghdy F, Svehla MJ. Force Application During Cochlear Implant Insertion: An Analysis for Improvement of Surgeon Technique. IEEE Trans Biomed Eng 2007; 54:1247-55. [PMID: 17605356 DOI: 10.1109/tbme.2007.891937] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Highly invasive surgical procedures, such as the implantation of a prosthetic device, require correct force delivery to achieve desirable outcomes and minimize trauma induced during the operation. Improvement in surgeon technique can reduce the chances of excessive force application and lead to optimal placement of the electrode array. The fundamental factors that affect the degree of success for cochlear implant recipients are identified through empirical methods. Insertion studies are performed to assess force administration and electrode trajectories during implantations of the Nucleus 24 Contour and Nucleus 24 Contour Advance electrodes into a synthetic model of the human Scala Tympani, using associated methods. Results confirm that the Advance Off- Stylet insertion of the soft-tipped Contour Advance electrode gives an overall reduction in insertion force. Analysis of force delivery and electrode positioning during cochlear implantation can help identify and control key factors for improvement of insertion method. Based on the findings, suggestions are made to enhance surgeon technique.
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Affiliation(s)
- Catherine A Todd
- School of Electrical, Computer and Telecommunications Engineering, Faculty of Informatics, University of Wollongong, NSW 2500 Australia.
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Kha HN, Chen BK, Clark GM. 3D finite element analyses of insertion of the Nucleus standard straight and the Contour electrode arrays into the human cochlea. J Biomech 2007; 40:2796-805. [PMID: 17408675 DOI: 10.1016/j.jbiomech.2007.01.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2005] [Accepted: 01/16/2007] [Indexed: 10/23/2022]
Abstract
Previous experimental studies of insertion of the Nucleus standard straight and the Contour arrays into the scala tympani have reported that the electrode arrays cause damage to various cochlear structures. However, the level of insertion-induced damage by these electrode arrays to cochlear structures (the spiral ligament, the basilar membrane and the osseous spiral lamina) has not been quantified. Although it has been suggested that rotation can overcome this resistance and prevent the basilar membrane from being pierced by the tip of the Nucleus standard straight array, there has not been any attempt to study the relationship between the rotation and the reduction of damage to the basilar membrane. In this study, 3D finite element analyses of insertions of the Nucleus standard straight array and the Contour array into the scala tympani have been undertaken. The perforation of the basilar membrane by the tip of the Nucleus standard straight array at the region of 11-14 mm from the round window appears to be compounded by the geometry of the spiral passage of the scala tympani. Anti-clockwise rotations between 25 degrees and 90 degrees applied at the basal end of the electrode array (for the right cochlea) were shown to significantly reduce the contact stresses exerted by the tip on the basilar membrane which support the practice of applying small rotation partway through insertion of electrode array to minimize damage to the basilar membrane. Although the Contour array (with its stylet intact) is stiffer than the Nucleus standard straight array, a slight withdrawal of the stylet from the Contour array before insertion was found to significantly reduce damage by the electrode array to the spiral ligament and the basilar membrane.
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Affiliation(s)
- H N Kha
- Department of Mechanical Engineering, Monash University, Wellington Road, Clayton Victoria 3800 Melbourne, Australia.
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Clark GM. The multiple-channel cochlear implant: the interface between sound and the central nervous system for hearing, speech, and language in deaf people-a personal perspective. Philos Trans R Soc Lond B Biol Sci 2006; 361:791-810. [PMID: 16627295 PMCID: PMC1609401 DOI: 10.1098/rstb.2005.1782] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The multiple-channel cochlear implant is the first sensori-neural prosthesis to effectively and safely bring electronic technology into a direct physiological relation with the central nervous system and human consciousness, and to give speech perception to severely-profoundly deaf people and spoken language to children. Research showed that the place and temporal coding of sound frequencies could be partly replicated by multiple-channel stimulation of the auditory nerve. This required safety studies on how to prevent the effects to the cochlea of trauma, electrical stimuli, biomaterials and middle ear infection. The mechanical properties of an array and mode of stimulation for the place coding of speech frequencies were determined. A fully implantable receiver-stimulator was developed, as well as the procedures for the clinical assessment of deaf people, and the surgical placement of the device. The perception of electrically coded sounds was determined, and a speech processing strategy discovered that enabled late-deafened adults to comprehend running speech. The brain processing systems for patterns of electrical stimuli reproducing speech were elucidated. The research was developed industrially, and improvements in speech processing made through presenting additional speech frequencies by place coding. Finally, the importance of the multiple-channel cochlear implant for early deafened children was established.
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Affiliation(s)
- Graeme M Clark
- The Bionic Ear Institute 384-388 Albert Street, East Melbourne, Vic. 3002, Australia.
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Abstract
Cochlear Limited (Cochlear) released the fourth-generation cochlear implant system, Nucleus Freedom, in 2005. Freedom is based on 25 years of experience in cochlear implant research and development and incorporates advances in medicine, implantable materials, electronic technology, and sound coding. This article presents the development of Cochlear's implant systems, with an overview of the first 3 generations, and details of the Freedom system: the CI24RE receiver-stimulator, the Contour Advance electrode, the modular Freedom processor, the available speech coding strategies, the input processing options of Smart Sound to improve the signal before coding as electrical signals, and the programming software. Preliminary results from multicenter studies with the Freedom system are reported, demonstrating better levels of performance compared with the previous systems. The final section presents the most recent implant reliability data, with the early findings at 18 months showing improved reliability of the Freedom implant compared with the earlier Nucleus 3 System. Also reported are some of the findings of Cochlear's collaborative research programs to improve recipient outcomes. Included are studies showing the benefits from bilateral implants, electroacoustic stimulation using an ipsilateral and/or contralateral hearing aid, advanced speech coding, and streamlined speech processor programming.
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Wright CG, Roland PS, Kuzma J. Advanced bionics thin lateral and Helix II electrodes: a temporal bone study. Laryngoscope 2006; 115:2041-5. [PMID: 16319621 DOI: 10.1097/01.mlg.0000181461.63392.49] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE This study was performed to evaluate the insertional properties of two cochlear implant electrodes recently developed by Advanced Bionics Corporation. STUDY DESIGN Anatomic study using human cadaveric temporal bones. METHODS The electrode prototypes we tested are the Thin Lateral and Helix II arrays, which incorporate features designed to minimize insertional trauma. A total of eight electrodes (4 of each prototype) were evaluated after insertion into freshly fixed temporal bones. The electrodes were inserted by way of standard cochleostomies, and the specimens were subsequently dissected to assess electrode position, insertion depth, and intracochlear trauma. RESULTS Quantitative data regarding insertion depths and contact distances from the modiolus are presented for all electrodes tested. The mean insertion depths were 368 degrees for the Thin Lateral electrodes, which are designed to approximate the lateral cochlear wall, and 436 degrees for the Helix II electrodes, which occupy a more medial position in the scala tympani. No evidence of insertional trauma was observed with either electrode. The ease of insertion and absence of trauma were confirmed during additional trials in which electrode behavior was directly observed during insertion into previously opened cochleas. CONCLUSION Both electrodes performed favorably in our human temporal bone trials, and both arrays appear promising for clinical use, especially in patients with residual hearing in whom atraumatic insertion is an important objective.
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Affiliation(s)
- Charles G Wright
- Department of Otolaryngology, Head and Neck Surgery, Southwestern Medical Center, Dallas, TX 75390, USA.
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Kha HN, Chen BK. Determination of frictional conditions between electrode array and endosteum lining for use in cochlear implant models. J Biomech 2006; 39:1752-6. [PMID: 15982662 DOI: 10.1016/j.jbiomech.2005.04.031] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Accepted: 04/30/2005] [Indexed: 11/17/2022]
Abstract
Frictional conditions between the electrode array (in cochlear implants) and the endosteum lining covering the walls of the interior scala tympani structure strongly influence the sliding behaviour of the electrode array. Friction coefficients, determined by a simple but effective method based on the impending slippage model of electrode arrays sliding over the endosteum lining are reported in this paper. In this study, friction coefficients of the Nucleus standard straight and the Contour arrays have been determined with and without lubricants applied on the endosteum lining. In the absence of applied lubricants, friction coefficients were found to be 0.19 for the Nucleus standard straight array and 0.12 for the Contour array. Application of lubricants (glycerin and sorbelene) has the potential to lower the friction coefficient for Nucleus standard straight array (0.12 and 0.15) and for the Contour array (0.04 and 0.08). These results are used in finite element models to predict accurately the trajectories of electrode arrays and sliding contact pressures on cochlear structures to evaluate the likelihood of damage sustained during insertion.
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Affiliation(s)
- H N Kha
- Department of Mechanical Engineering, Monash University, 900 Dandenong Road, Caulfield East, Vic. 3145, Melbourne, Australia.
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Wardrop P, Whinney D, Rebscher SJ, Roland JT, Luxford W, Leake PA. A temporal bone study of insertion trauma and intracochlear position of cochlear implant electrodes. I: Comparison of Nucleus banded and Nucleus Contour electrodes. Hear Res 2005; 203:54-67. [PMID: 15855030 DOI: 10.1016/j.heares.2004.11.006] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2004] [Accepted: 11/14/2004] [Indexed: 12/01/2022]
Abstract
In recent years, new designs of cochlear implant electrodes have been introduced in an attempt to improve efficiency and performance by locating stimulation sites closer to spiral ganglion neurons and deeper into the scala tympani. The goal of this study was to document insertion depth, intracochlear position and insertion trauma with the Nucleus Contour electrode and to compare results to those observed with the earlier generation Nucleus banded electrode. For this comparison eight Nuclears banded electrodes and 18 Contour electrodes were implanted in cadaver temporal bones using a realistic surgical exposure. Two experienced cochlear implant surgeons and two otology fellows with specialized training in cochlear implant surgery were selected for the study to represent a range of surgical experience similar to that of surgeons currently performing the procedure throughout the world. Following insertion of the electrodes, specimens were imaged using plain film X-ray, embedded in acrylic resin, cut in radial sections with the electrodes in place, and each cut surface was polished. Insertion depth was measured in digitized X-ray images, and trauma was assessed in each cross-section. The Contour electrode inserted more deeply (mean depth=17.9 mm or 417 degrees ) than the banded electrode (mean depth=15.3 mm or 285 degrees ). The incidence and severity of trauma varied substantially among the temporal bones studied. However, the nature and frequency of injuries observed with the two devices were very similar. The Contour electrode was clearly positioned closer to the modiolus than the banded model, and also appeared easier to use. Based on this difference in position and data from previous studies we conclude that the Contour electrode may provide lower thresholds and improved channel selectivity, but the incidence of trauma remains a problem with the newer design. The relative influences of electrode positioning and neural degeneration that may result from trauma are as yet unclear.
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Affiliation(s)
- Peter Wardrop
- Department of Otolaryngology, Crosshouse Hospital, Kilmarnock, Ayrshire, Scotland KA2 OBE, UK.
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Roland JT. A Model for Cochlear Implant Electrode Insertion and Force Evaluation: Results with a New Electrode Design and Insertion Technique. Laryngoscope 2005; 115:1325-39. [PMID: 16094101 DOI: 10.1097/01.mlg.0000167993.05007.35] [Citation(s) in RCA: 136] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES AND HYPOTHESIS This study has the specific aim of evaluating the insertion characteristics of a new cochlear implant electrode. Techniques for evaluation of fluoroscopic real time mechanical insertion dynamics, histologic electrode position and trauma results, hydraulic force, and mechanical insertion forces are presented. In addition, this study should serve to present a novel model for cochlear implant electrode insertion evaluations. STUDY DESIGN Prospective analysis using a series of analytical techniques. METHODS All studies are conducted in fixed cadaveric temporal bones. Real time fluoroscopic insertion evaluations, histologic evaluations for trauma and electrode position in embedded bones, hydraulic measures, and mechanical intracochlear force measurements are conducted with a current and new electrode. RESULTS The Contour Advance electrode provides a more reliable and less traumatic insertion when deployed with the Advance Off Stylet technique. This is largely because of a reduction in intracochlear outer wall force generation. Fluoroscopic and histologic analysis reveal a smooth insertion without reliance on cochlear outer wall contact. No hydraulic forces were detected when measured from the superior semicircular canal ampulla. CONCLUSION The model used for this study provides valuable information to cochlear implant surgeons and design engineers. The Contour Advance electrode, inserted with the Advance Off Stylet technique, represents an improvement over the Contour electrode inserted with the standard insertion technique.
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Affiliation(s)
- J Thomas Roland
- Department of Otolaryngology and Neurosurgery, New York University School of Medicine, 550 First Avenue, New York, NY 10016, U.S.A
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Roland PS, Gstöttner W, Adunka O. Method for hearing preservation in cochlear implant surgery. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.otot.2005.03.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Abstract
OBJECTIVES/HYPOTHESIS Cochlear implantation (CI) carries with it the potential risk for vestibular system insult or stimulation with resultant dysfunction. As candidate profiles continue to evolve and with the recent development of bilateral CI, understanding the significance of this risk takes on an increasing importance. STUDY DESIGN Between 1997 to 2001, a prospective observational study was carried out in a tertiary care medical center to assess the effects of unilateral CI on the vestibular system. METHODS Assessment was performed using the dizziness handicap inventory (DHI), vestibulo-ocular reflex (VOR) testing using both alternate bithermal caloric irrigations (ENG) and rotational chair-generated sinusoidal harmonic accelerations (SHA), and computerized dynamic platform posturography (CDP) at preoperative, 1-month, 4-month, 1-year and 2-year postimplantation visits. CI was carried out without respect to the preoperative vestibular function test results. RESULTS Specifically, 86 patients were entered into the study after informed consent. For the group as a whole, pair wise comparisons revealed few significant differences between preoperative and postoperative values for VOR testing (ENG and SHA) at any of the follow-up intervals. Likewise, DHI testing was also unchanged except for significant reductions (improvements) in the emotional subcategory scores at both the 4-month and 1-year intervals. CDP results demonstrated substantial improvements in postural sway in the vestibular conditions (5 and 6) as well as composite scores with the device "off" and "on" at the 1-month, 4-month, 1-year, and 2-year intervals. Device activation appeared to improve postural stability in some conditions. Excluding those patients with preoperative areflexic or hyporeflexic responses in the implanted ear (total [warm + cool] caloric response <or= 15 deg/s), substantial reductions (>or=21 deg/s maximum slow phase velocity) in total caloric response were observed for 8 (29%) patients at the 4-month interval. These persisted throughout the study period. These changes were accompanied by significant low frequency phase changes on SHA testing confirming a VOR insult. Of interest, no significant changes were detected in the DHI or CDP, and there were no effects of age, sex, device manufacturer, or etiology of hearing loss (HL) for these patients. CONCLUSIONS Unilateral CI rarely results in significant adverse effects on the vestibular system as measured by the DHI, ENG, SHA, and CDP. On the contrary, patients that underwent CI experienced significant improvements in the objective measures of postural stability as measured by CDP. Device activation in music appeared to have an additional positive effect on postural stability during CDP testing. Although VOR testing demonstrated some decreases in response, patients did not suffer from disabling vestibular effects following CI. The mechanism underlying these findings remains speculative. These findings should be considered in counseling patients about CI.
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Affiliation(s)
- Craig A Buchman
- Department of Otolaryngology, University of North Carolina at Chapel Hill, 27599-7600, USA.
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Adunka O, Kiefer J, Unkelbach MH, Lehnert T, Gstoettner W. Development and Evaluation of an Improved Cochlear Implant Electrode Design for Electric Acoustic Stimulation. Laryngoscope 2004; 114:1237-41. [PMID: 15235353 DOI: 10.1097/00005537-200407000-00018] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The objective of this study was to assess the intracochlear position and the extent of trauma to cochlear structures using a new prototype electrode carrier (Flex EAS). Special emphasis was placed on the practicality for combined electric and acoustic stimulation of the auditory system. STUDY DESIGN Human temporal bones were evaluated histologically after insertion of the electrodes, and insertion forces were measured in an acrylic model of the scala tympani. METHODS 1) Insertion forces with the regular C40+ array and the new electrode prototype were measured in an acrylic model of the scala tympani. 2) Ten human temporal bones were implanted using the same surgical procedure as in vivo. All bones underwent fixation methylmethacrylate embedding to allow cutting of the undecalcified bone with the electrode in situ. In addition, radiography of the implanted devices was performed and correlated to histologic results. Electrode positions and trauma to cochlear structures were then evaluated histologically. RESULTS All insertions of the new electrode array were performed in the scala tympani of the cochlea. All insertions were atraumatic and covered one cochlear turn. The only effect on cochlear structures that could be observed was a slight lifting of the basilar membrane in the middle turn limited to the tip of the electrode. In three bones, basal trauma, which resulted from the cochleostomy itself, could be observed as well. All neural structures remained intact. CONCLUSIONS The new electrode prototype provides very good mechanical properties for safe and atraumatic implantation. All criteria for the use in hearing-preservation cochlear implantation for electric and acoustic stimulation were fulfilled. Surgical measures to prevent basal trauma appear to be very important.
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Affiliation(s)
- Oliver Adunka
- ENT Department, J.W. Goethe University Frankfurt am Main, Frankfurt am Main, Germany.
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Deman PR, Dirckx JJ, Peeters SA, Zarowski AJ, Offeciers FE. Overview of safety imaging methods for newly designed cochlear implant electrodes. Cochlear Implants Int 2004; 5:58-70. [DOI: 10.1179/cim.2004.5.2.58] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Pfingst BE, Xu L. Across-site variation in detection thresholds and maximum comfortable loudness levels for cochlear implants. J Assoc Res Otolaryngol 2003; 5:11-24. [PMID: 14605920 PMCID: PMC2538372 DOI: 10.1007/s10162-003-3051-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2002] [Accepted: 07/14/2003] [Indexed: 10/26/2022] Open
Abstract
In cochlear implants, variation across stimulation sites in psychophysical detection thresholds (T levels) and maximum comfortable loudness levels (C levels) can be large when narrow-bipolar (BP) stimulation is used. This across-site variation is typically smaller when monopolar (MP) stimulation is used. At least two models can account for across-site variation and the effects of electrode configuration on the magnitude of the variation. According to one model, across-site variation reflects site-to-site differences in the distances between the stimulating electrodes and the sites of action-potential initiation. Under this model, the lower across-site variation with MP stimulation is due to shallower current versus distance gradients. An alternative model assumes that T and C levels depend on integration of activity across the whole population of neurons and that MP stimulation activates neurons over a larger spatial extent than does BP stimulation. If T and C levels are determined by integration of activity across large overlapping populations of neurons, then their values at adjacent sites should be more similar than if these levels result from integration across smaller, more independent populations. We tested the models by examining the effects on across-site variation of three variables believed to affect the spatial extent of activation: electrode configuration, stimulus level within the dynamic range, and electrode-array design. T levels and C levels were measured in 13 subjects with Nucleus CI24M (straight array) and 9 subjects with Nucleus CI24R(CS) (Contour) cochlear implants using bipolar (BP) and monopolar (MP) electrode configurations. Site-to-site variation in T and C levels for BP stimulation was 2.1-3.3 times larger than that for MP stimulation. Contrary to the across-neuron integration hypothesis, no significant differences were found between across-site variation for T levels and that for C levels for the BP configuration. There was considerable overlap in site-to-site variation values for the two types of implants but mean site-to-site variation in C levels for CI24M implants was significantly lower than that for CI24R(CS) implants. Control studies suggested that these results were not an artifact of the scale, and not due to differences in inherent variability of the psychophysical measures, or to the method of quantifying across-site variation.
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Affiliation(s)
- Bryan E Pfingst
- Kresge Hearing Research Institute, Department of Otolaryngology, University of Michigan, Ann Arbor, MI 48109-0506, USA.
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Brors D, Aletsee C, Schwager K, Mlynski R, Hansen S, Schäfers M, Ryan AF, Dazert S. Interaction of spiral ganglion neuron processes with alloplastic materials in vitro(1). Hear Res 2002; 167:110-21. [PMID: 12117535 DOI: 10.1016/s0378-5955(02)00355-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The cochlear implant (CI) involves the introduction of alloplastic materials into the cochlea. While current implants interact with cochlear neurons at a distance, direct interactions between spiral ganglion (SG) neurites and implants could be fostered by appropriate treatment with neurotrophic factors. The interactions of fibroblasts and osteoblasts with alloplastic materials have been well studied in vitro and in vivo. However, interactions of inner ear neurons with such alloplastic materials have yet to be described. To investigate survival and growth behavior of SG neurons on different materials, SG explants from post-natal day 5 rat SG were cultured for 72 h in the presence of neurotrophin-3 (10 ng/ml) on titanium, gold, stainless steel, platinum, silicone and plastic surfaces that had been coated with laminin and poly-L-lysine. Neurite outgrowth was investigated after immunohistological staining for neurofilament, by image analysis to determine neurite extension and directional changes. Neurite morphology and adhesion to the alloplastic material were also evaluated by scanning electron microscopy (SEM). On titanium, SG neurites reached the highest extent of outgrowth, with an average length of 662 microm and a mean of 31 neurites per explant, compared to 568 microm and 21 neurites on gold, 574 microm and 24 neurites on stainless steel, 509 microm and 16 neurites on platinum, 281 microm and 12 neurites on silicone and 483 microm and 31 neurites on plastic. SEM revealed details of adhesion of neurites and interaction with non-neuronal cells. The results of this study indicate that the growth of SG neurons in vitro is strongly influenced by alloplastic materials, with titanium exhibiting the highest degree of biocompatibility with respect to neurite extension. The knowledge of neurite interaction with different alloplastic materials is of clinical interest, as development in CI technology leads to closer contact of implanted electrodes with surviving inner ear neurons.
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Affiliation(s)
- Dominik Brors
- Department of Otorhinolaryngology, Head and Neck Surgery, Bayerische Julius Maximilians Universität, 97080 Würzburg, Germany
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Saunders E, Cohen L, Aschendorff A, Shapiro W, Knight M, Stecker M, Richter B, Waltzman S, Tykocinski M, Roland T, Laszig R, Cowan R. Threshold, comfortable level and impedance changes as a function of electrode-modiolar distance. Ear Hear 2002; 23:28S-40S. [PMID: 11883764 DOI: 10.1097/00003446-200202001-00004] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The study investigated the hypothesis that threshold and comfortable levels recorded from cochlear implant patients would reduce, and dynamic range increase, as distance of the electrode from the modiolar wall (radial distance) decreases. Two groups of cochlear implant patients participated; one group using the Nucleus' 24 Contour electrode array, and one group using the Nucleus standard straight (banded) array. The Nucleus 24 Contour array has been shown in temporal bone studies to lie closer to the modiolus than the banded array. The relationship of electrode impedance and radial distance is also investigated. DESIGN The study, conducted at three centers, evaluated 21 patients using the Contour array, and 36 patients using the banded array. For each patient, threshold, comfortable levels and dynamic range were measured at four time points. Common ground electrode impedance was recorded clinically from each patient, at time intervals up to 12 wk. An estimate of the radial distance of the electrode from the modiolus was made by analysis of Cochlear view x-rays. RESULTS Threshold and comfortable levels were significantly lower for the Nucleus 24 Contour array than for the banded array. However, dynamic range measurements did not show the predicted increase. In a majority of subjects, a significant correlation was found between the estimated radial distance of the electrode from the modiolus and the measured threshold and comfortable levels. This trend was not observed for dynamic range. The analysis indicates that other factors than radial distance are involved in the resultant psychophysical levels. Clinical impedance measures (common ground) were found to be significantly higher for the Contour array. However, the electrodes on the Contour array are half-rings, which are approximately only half the geometric size of the full rings as electrodes of the standard array. When the geometric electrode area in the two array designs are normalized, the trends in the electrode impedance behavior are similar. CONCLUSIONS The results support the hypothesis that the relationship between the radial distance of the electrode and the psychophysical measures are influenced by patterns of fibrous tissue growth and individual patient differences, such as etiology and neural survival. Impedance measures for the Nucleus 24 Contour electrode array were higher than the banded electrode array, but this is primarily due to the reduction in electrode surface area. The different outcomes in impedance over time suggest differences in the relative contributions of the components of impedance with the two arrays.
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Affiliation(s)
- Elaine Saunders
- Co-operative Research Centre for Cochlear Implant & Hearing Aid Innovation, Melbourne, Australia
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Nadol JB, Shiao JY, Burgess BJ, Ketten DR, Eddington DK, Gantz BJ, Kos I, Montandon P, Coker NJ, Roland JT, Shallop JK. Histopathology of cochlear implants in humans. Ann Otol Rhinol Laryngol 2001; 110:883-91. [PMID: 11558767 DOI: 10.1177/000348940111000914] [Citation(s) in RCA: 219] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The insertion of an intrascalar electrode array during cochlear implantation causes immediate damage to the inner ear and may result in delayed onset of additional damage that may interfere with neuronal stimulation. To date, there have been reports on fewer than 50 temporal bone specimens from patients who had undergone implantation during life. The majority of these were single-channel implants, whereas the majority of implants inserted today are multichannel systems. This report presents the histopathologic findings in temporal bones from 8 individuals who in life had undergone multichannel cochlear implantation, with particular attention to the type and location of trauma and to long-term changes within the cochlea. The effect of these changes on spiral ganglion cell counts and the correlation between speech comprehension and spiral ganglion cell counts were calculated. In 4 of the 8 cases, the opposite, unimplanted ear was available for comparison. In 3 of the 4 cases, there was no significant difference between the spiral ganglion cell counts on the implanted and unimplanted sides. In addition, in this series of 8 cases, there was an apparent negative correlation between residual spiral ganglion cell count and hearing performance during life as measured by single-syllable word recognition. This finding suggests that abnormalities in the central auditory pathways are at least as important as spiral ganglion cell loss in limiting the performance of implant users.
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Affiliation(s)
- J B Nadol
- Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston 02114, USA
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Abstract
OBJECTIVE The objective of the article is to provide an accurate model of the human cochlea with which potential distributions and thus neural excitation patterns around cochlear implant electrodes can be determined. Improvements on previous models of the implanted cochlea are that this model 1) includes the spiral nature of the cochlea as well as many other anatomical details (and it is a model of the human cochlear rather than the guinea pig cochlea), and 2) facilitates modeling of different electrode geometries, array locations and electrode separations without changing the structure of the model. DESIGN A three-dimensional spiraling finite element model of the human cochlea was created. The model incorporates the effect of neighboring canals and conduction along the fluid-filled canals of the cochlea. Potential distributions are used as inputs to a nerve fiber model to investigate auditory nerve excitation patterns around intracochlear electrode arrays. RESULTS Potential distributions around intracochlear electrodes generated with the finite element model are presented. The effects of electrode separation, electrode geometry and array location on excitation threshold, excitation spread and ectopic excitation (i.e., excitation of nerve fibers at an undesirable location) are demonstrated. CONCLUSIONS The following conclusions should be considered preliminary, as their accuracy depends on the exactness of the underlying model. The spiraling geometry of the cochlea causes asymmetry in potential distributions. The location of electrodes along the length of the basilar membrane has a stronger influence on the site of excitation than the polarity of the leading phase of the stimulus. Array location is the primary parameter that controls excitation spread. Threshold currents and the effect of ongoing loss of peripheral dendrites on threshold currents can be limited by placing arrays close to the modiolus. Point electrode geometries are recommended above banded electrode geometries only when the array can be placed close to the modiolus. There is a tradeoff between array location and the degree of ectopic stimulation caused by a specific array location. Bimodal excitation patterns exist at comfortable stimulus intensities for longitudinal bipolar electrode configurations. It is shown that an electrode configuration with an electrode separation of approximately half that of the bipolar electrode separation of the Nucleus electrode can be used instead of radial and offset radial electrode configurations to create unimodal excitation patterns. The stimulation resolution of cochlear implant electrode arrays can potentially be improved by increasing the number of electrode contacts in an array.
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Affiliation(s)
- T Hanekom
- Department of Electrical, Electronic and Computer Engineering, University of Pretoria, South Africa
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