The consequences of neural degeneration regarding optimal cochlear implant position in scala tympani: A model approach

The removal of an indwelling cochlear implant electrode followed by reinsertion of a new device has been a maneuver of uncertain cosequences to the cochlea and its surviving neural population. The present study was conducted in an attempt to elucidate the factors at determine whether a reimplantation procedure will be successful. Cochlear implantation followed by explanation and subsequent implantation was performed in eight adult cats. Evaluation of cochlear histopathology suggested a significant increase in electrode insertion trauma when there was proliferation of granulation tissue in the round window area and scala tympani. In other cases, atraumatic insertion was achieved without apparent injury to the cochlea. The results of a survey of cochlear implant manufacturers and surgeons indicate that electrode replacement can usually be accomplished without adverse effects. Difficulties have been encountered, however, in moving implants with protuberant electrodes and when reimplantation was attempted on a delayed basis following explanation.

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Neural Tissue Degeneration in Rosenthal’s Canal and Its Impact on Electrical Stimulation of the Auditory Nerve by Cochlear Implants: An Image-Based Modeling Study

International Journal of Molecular Sciences ◽

10.3390/ijms21228511 ◽

2020 ◽

Vol 21 (22) ◽

pp. 8511

Author(s):

Kiran Kumar Sriperumbudur ◽

Revathi Appali ◽

Anthony W. Gummer ◽

Ursula van Rienen

Keyword(s):

Cochlear Implant ◽

Cochlear Implants ◽

Auditory Nerve ◽

Ganglion Cells ◽

Spiral Ganglion ◽

Sensorineural Deafness ◽

Neural Tissue ◽

Neural Degeneration ◽

Tissue Degeneration ◽

Ganglion Neurons

Sensorineural deafness is caused by the loss of peripheral neural input to the auditory nerve, which may result from peripheral neural degeneration and/or a loss of inner hair cells. Provided spiral ganglion cells and their central processes are patent, cochlear implants can be used to electrically stimulate the auditory nerve to facilitate hearing in the deaf or severely hard-of-hearing. Neural degeneration is a crucial impediment to the functional success of a cochlear implant. The present, first-of-its-kind two-dimensional finite-element model investigates how the depletion of neural tissues might alter the electrically induced transmembrane potential of spiral ganglion neurons. The study suggests that even as little as 10% of neural tissue degeneration could lead to a disproportionate change in the stimulation profile of the auditory nerve. This result implies that apart from encapsulation layer formation around the cochlear implant electrode, tissue degeneration could also be an essential reason for the apparent inconsistencies in the functionality of cochlear implants.

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Scala-Tympani Phantom With Cochleostomy and Round-Window Openings for Cochlear-Implant Insertion Experiments

Journal of Medical Devices ◽

10.1115/1.4027617 ◽

2014 ◽

Vol 8 (4) ◽

Cited By ~ 8

Author(s):

Lisandro Leon ◽

Matt S. Cavilla ◽

Michael B. Doran ◽

Frank M. Warren ◽

Jake J. Abbott

Keyword(s):

Cochlear Implant ◽

Coordinate System ◽

Round Window ◽

Scala Tympani ◽

Electrode Arrays ◽

Angular Measurements ◽

Insertion Techniques

Experiments with scala-tympani (ST) phantoms are used to evaluate new electrode arrays and cochlear-implant insertion techniques. To date, phantoms have not accounted for clinical orientations and geometric differences between round-window (RW) insertions and anteroinferior cochleostomy insertions. For improved assessments of insertion experiments, we present a scala-tympani phantom that offers three distinct benefits over previous phantoms: it mimics the standard otologic position, it accommodates for both round-window and anteroinferior cochleostomy insertions, and it incorporates a visual coordinate system based on industry consensus making standardized angular measurements possible.

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In vitro modifications of the scala tympani environment and the cochlear implant array surface

The Laryngoscope ◽

10.1002/lary.23408 ◽

2012 ◽

Vol 122 (9) ◽

pp. 2057-2063 ◽

Cited By ~ 6

Author(s):

Georgios Kontorinis ◽

Verena Scheper ◽

Kirsten Wissel ◽

Timo Stöver ◽

Thomas Lenarz ◽

...

Keyword(s):

Cochlear Implant ◽

Scala Tympani

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Computed-tomography estimates of interaural mismatch in insertion depth and scalar location in bilateral cochlear-implant users

10.1101/2021.02.26.21252533 ◽

2021 ◽

Author(s):

Matthew J Goupell ◽

Jack H Noble ◽

Sandeep A Phatak ◽

Elizabeth Kolberg ◽

Miranda Cleary ◽

...

Keyword(s):

Computed Tomography ◽

Cochlear Implant ◽

Surgical Techniques ◽

Superior Olivary Complex ◽

Negative Consequences ◽

Scala Tympani ◽

Insertion Depth ◽

Binaural Processing ◽

Bilateral Cochlear Implant ◽

Interaural Differences

Hypothesis: We hypothesized that the bilateral cochlear-implant (BI-CI) users would have a range of interaural insertion-depth mismatch because of different physical placements or characteristics of the arrays, but less than half of electrodes would have less than 75° or 3 mm of interaural insertion-depth mismatch. We also hypothesized that interaural insertion-depth mismatch would be more prevalent nearer the apex, when electrodes were located outside of scala tympani (i.e., possible interaural scalar mismatch), and when the arrays were a mix of pre-curved and straight types. Background: Brainstem neurons in the superior olivary complex are exquisitely sensitive to interaural differences, the cues to sound localization. These binaurally sensitive neurons rely on interaurally place-of-stimulation-matched inputs at the periphery. BI-CI users may have interaural differences in insertion depth and scalar location, causing interaural place-of-stimulation mismatch that impairs binaural abilities. Methods: Insertion depths and scalar locations were calculated from temporal-bone computed-tomography (CT) scans of 107 BI-CI users (27 Advanced Bionics, 62 Cochlear, and 18 Med-El). Each subject had either both pre-curved, both straight, or one of each type of array (mixed). Results: The median interaural insertion-depth mismatch was 23.4° or 1.3 mm. Relatively large interaural insertion-depth mismatch sufficient to disrupt binaural processing occurred for about 15% of electrode pairs [defined as >75° (13.0% of electrode pairs) or >3 mm (19.0% of electrode pairs)]. There was a significant three-way interaction of insertion depth, scalar location, and array type. Interaural insertion-depth mismatch was most prevalent when electrode pairs were more apically located, electrode pairs had interaural scalar mismatch (i.e., one in Scala Tympani, one in Scala Vestibuli), and when the arrays were both pre-curved. Conclusion: Large interaural insertion-depth mismatch can occur in BI-CI users. For new BI-CI users, improved surgical techniques to avoid interaural insertion-depth and scalar mismatch is recommended. For existing BI-CI users with interaural insertion-depth mismatch, interaural alignment of clinical frequency allocation tables by an audiologist might remediate any negative consequences to spatial-hearing abilities.

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Use of Multichannel Cochlear Implants in Obstructed and Obliterated Cochleas

Otolaryngology ◽

10.1177/019459988809800113 ◽

1988 ◽

Vol 98 (1) ◽

pp. 72-81 ◽

Cited By ~ 120

Author(s):

Bruce J. Gantz ◽

Brian F. Mccabe ◽

Richard S. Tyler

Keyword(s):

Cochlear Implant ◽

Cochlear Implants ◽

Middle Ear ◽

External Auditory Canal ◽

Single Channel ◽

Scala Tympani ◽

Radiographic Evidence ◽

Early Experiences ◽

Channel Electrode ◽

Gain Access

Obstruction that occurs within the scala tympani (after meningitis or otosclerosis) has been considered a contraindication for placement of a multichannel cochlear implant electrode. Two patients who exhibited radiographic evidence of intracochlear narrowing and obliteration were implanted with multichannel electrodes. Implantation involved creation of a channel for the electrode to wrap around the modiolus. The middle ear cavity and the external auditory canal also had to be removed to gain access. The response of one of the patients was similar to that of patients with normal cochlear anatomy who use multichannel devices. These early experiences, along with one case in which a single-channel electrode was placed, is presented.

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Surgical anatomy of the round window with special reference to cochlear implantation

The Journal of Laryngology & Otology ◽

10.1017/s0022215100101343 ◽

1987 ◽

Vol 101 (2) ◽

pp. 97-102 ◽

Cited By ~ 37

Author(s):

Burkhard K. H. Franz ◽

Graeme M. Clark ◽

David M. Bloom

Keyword(s):

Cochlear Implant ◽

Special Reference ◽

Cochlear Implantation ◽

Round Window ◽

Surgical Anatomy ◽

Round Window Membrane ◽

Scala Tympani ◽

Good View ◽

Posterior Tympanotomy ◽

Round Window Niche

AbstractWhen the multi-channel cochlear implant electrode is inserted into the scala tympani through the round window the operation is best performed via a posterior tympanotomy. The view of the round window membrane, however, is incomplete because of its orientation and the fact that it has a conical shape. Nevertheless, a good view along the basal turn is obtained after the antero-inferior overhang of the round window niche and the crista fenestrae have been removed. It might be damaging to drill away the postero-superior overhang as the osseous spiral lamina lies extremely close to the round window membrane.

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Evaluation of the Relationship between the NRT-Ratio, Cochlear Anatomy, and Insertions Depth of Perimodiolar Cochlear Implant Electrodes

BioMed Research International ◽

10.1155/2015/706253 ◽

2015 ◽

Vol 2015 ◽

pp. 1-6 ◽

Cited By ~ 6

Author(s):

Philipp Mittmann ◽

Grit Rademacher ◽

Sven Mutze ◽

Frederike Hassepass ◽

Arneborg Ernst ◽

...

Keyword(s):

Cochlear Implant ◽

Electrode Array ◽

Scala Tympani ◽

Flat Panel ◽

Insertion Depth ◽

Tomography System ◽

Neural Response Telemetry ◽

Auditory Performance ◽

The Relationship ◽

Scala Vestibuli

The position of the cochlear implant electrode array within the scala tympani is essential for an optimal postoperative hearing benefit. If the electrode array changes in between the scalae intracochlearly (i.e., from scala tympani to scala vestibuli), a reduced auditory performance can be assumed. We established a neural response telemetry-ratio (NRT-ratio) which corresponds with the scalar position of the electrodes but shows within its limits a variability. The aim of this study was to determine if insertion depth angle or cochlea size influences the NRT-ratio. The intraoperative electrophysiological NRT data of 26 patients were evaluated. Using a flat panel tomography system, the position of the electrode array was evaluated radiologically. The insertion depth angle of the electrode, the cochlea size, and the NRT-ratio were calculated postoperatively. The radiological results were compared with the intraoperatively obtained electrophysiological data (NRT-ratio) and statistically evaluated. In all patients the NRT-ratio, the insertion depth angle, and the cochlea size could be determined. A significant correlation between insertional depth, cochlear size, and the NRT-ratio was not found. The NRT-ratio is a reliable electrophysiological tool to determine the scalar position of a perimodiolar electrode array. The NRT-ratio can be applied independent from insertion depth and cochlear size.

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Factors Predicting Postoperative Sentence Scores in Postlinguistically Deaf Adult Cochlear Implant Patients

Annals of Otology Rhinology & Laryngology ◽

10.1177/000348949210100410 ◽

1992 ◽

Vol 101 (4) ◽

pp. 342-348 ◽

Cited By ~ 144

Author(s):

Peter J. Blamey ◽

Brian C. Pyman ◽

Graeme M. Clark ◽

Richard C. Dowell ◽

Michael Gordon ◽

...

Keyword(s):

Regression Analysis ◽

Electrical Stimulation ◽

Cochlear Implant ◽

Electrode Array ◽

Frequency Discrimination ◽

Gap Detection ◽

Scala Tympani ◽

Central Institute ◽

Independent Variables ◽

Profound Deafness

A sample of 64 postlinguistically profoundly to totally deaf adult cochlear implant patients were tested without lipreading by means of the Central Institute for the Deaf (CID) sentence test 3 months postoperatively. Preoperative promontory stimulation results (thresholds, gap detection, and frequency discrimination), age, duration of profound deafness, cause of deafness, lipreading ability, postoperative intracochlear thresholds and dynamic ranges for electrical stimulation, depth of insertion of the electrode array into the scala tympani, and number of electrodes in use were considered as possible factors that might be related to the postoperative sentence scores. A multiple regression analysis with stepwise inclusion of independent variables indicated that good gap detection and frequency discrimination during preoperative promontory testing, larger numbers of electrodes in use, and greater dynamic ranges for intracochlear electrical stimulation were associated with better CID scores. The CID scores tended to decrease with longer periods of profound deafness.

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A Scalable Model for Human Scala-Tympani Phantoms

Journal of Medical Devices ◽

10.1115/1.4002932 ◽

2011 ◽

Vol 5 (1) ◽

Cited By ~ 11

Author(s):

James R. Clark ◽

Frank M. Warren ◽

Jake J. Abbott

Keyword(s):

Cochlear Implant ◽

In Vivo Studies ◽

Scala Tympani ◽

Anatomical Data ◽

Cadaver Studies

In cochlear-implant (CI) insertion experiments, scala-tympani (ST) phantoms are often used in place of in vivo studies or cadaver studies. During the development of novel CI technology, a scaled-up phantom is often desirable. In this paper, we create a scalable model of the human ST by synthesizing published anatomical data and images. We utilize the model to fabricate an accurate, inexpensive, and reproducible ST phantom at a 3:1 scale.

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