Cochlear duct length and cochlear distance on preoperative CT: imaging markers for estimating insertion depth angle of cochlear implant electrode

Abstract Introduction Successful cochlear implantation requires an appropriate insertion depth of the electrode, which depends on cochlear duct length CDL). The CDL can vary due to ethnic factors. Objective The objective of the current study was to determine the CDL in an Indian adult cadaveric population. Methods The present was a cadaveric study using the temporal bones obtained after permission of the Institutional Review Board. The temporal bones were subjected to high-resolution computed tomography (HRCT), and the double oblique reformatted CT images were reconstructed through the basal turn of the cochlea. The reformatted images were then viewed in the minimum-intensity projection (minIP) mode, and the ‘A’ value (the diameter of the basal turn of the cochlea) was calculated. The CDL was then measured using the formula CDL = 4.16A - 4 (Alexiades et al). The data analysis was performed using the Microsoft Excel software, version 2016. Results A total of 51 temporal bones were included for imaging analysis. The CDL varied from 27.6 mm to 33.4 mm, with a mean length of 30.7 mm. There was no statistically significant difference between the two sides. Conclusion The CDL can be calculated with preoperative high-resolution CT, and can provide a roadmap for effective cochlear implant electrode insertion. The population-based anatomical variability needs to be taken into account to offer the most efficient and least traumatic insertion of the electrode.

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Cone beam CT for perioperative imaging in hearing preservation Cochlear implantation – a human cadaveric study

Journal of Otolaryngology - Head and Neck Surgery ◽

10.1186/s40463-019-0388-x ◽

2019 ◽

Vol 48 (1) ◽

Cited By ~ 2

Author(s):

Kayvan Nateghifard ◽

David Low ◽

Lola Awofala ◽

Dilakshan Srikanthan ◽

Jafri Kuthubutheen ◽

...

Keyword(s):

Radiation Dose ◽

Cochlear Implantation ◽

Lateral Wall ◽

Cone Beam ◽

Insertion Depth ◽

Cochlear Duct ◽

Low Radiation Dose ◽

A Value ◽

Cochlear Duct Length ◽

Temporal Bones

Abstract Background Knowledge of the cochlear implant array’s precise position is important because of the correlation between electrode position and speech understanding. Several groups have provided recent image processing evidence to determine scalar translocation, angular insertion depth, and cochlear duct length (CDL); all of which are being used for patient-specific programming. Cone beam computed tomography (CBCT) is increasingly used in otology due to its superior resolution and low radiation dose. Our objectives are as followed: Validate CBCT by measuring cochlear metrics, including basal turn diameter (A-value) and lateral wall cochlear duct length at different angular intervals and comparing it against microcomputed CT (uCT).Explore the relationship between measured lateral wall cochlear duct length at different angular intervals and insertion depth among 3 different length electrodes using CBCT. Methods The study was performed using fixed human cadaveric temporal bones in a tertiary academic centre. Ten temporal bones were subjected to the standard facial recess approach for cochlear implantation and imaged by CBCT followed by uCT. Measurements were performed on a three-dimensional reconstructed model of the cochlea. Sequential insertion of 3 electrodes (Med-El Flex24, 28 and Soft) was then performed in 5 bones and reimaged by CBCT. Statistical analysis was performed using Pearson’s correlation. Results There was good agreement between CBCT and uCT for cochlear metrics, validating the precision of CBCT against the current gold standard uCT in imaging. The A-value recorded by both modalities showed a high degree of linear correlation and did not differ by more than 0.23 mm in absolute values. For the measurement of lateral wall CDL at various points along the cochlea, there was a good correlation between both modalities at 360 deg and 720 deg (r = 0.85, p < 0.01 and r = 0.79, p < 0.01). The Flex24 electrode displayed consistent insertion depth across different bones. Conclusions CBCT reliably performs cochlear metrics and measures electrode insertion depth. The low radiation dose, fast acquisition time, diminished metallic artifacts and portability of CBCT make it a valid option for imaging in cochlear implant surgery.

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The Effect of Cochlear Size on Cochlear Implantation Outcomes

BioMed Research International ◽

10.1155/2019/5849871 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8 ◽

Cited By ~ 3

Author(s):

Jafri Kuthubutheen ◽

Amandeep Grewal ◽

Sean Symons ◽

Julian Nedzelski ◽

David Shipp ◽

...

Keyword(s):

Cochlear Implantation ◽

Outer Wall ◽

X Rays ◽

Speech Discrimination ◽

Insertion Depth ◽

Basal Diameter ◽

Cochlear Duct ◽

Significant Difference ◽

Cochlear Duct Length ◽

Electrode Insertion

Objectives. To determine if cochlear duct length and cochlear basal diameter, measured using routinely available radiology software, affect hearing outcomes after cochlear implantation with two different length electrodes. Methods. 55 patients who received a Med-El Flex electrode were retrospectively reviewed. 34 patients received the Flex 31 electrode (31mm) and 21 patients received the Flex 28 electrode (28mm). Preoperative high-resolution CT scans of the temporal bone were reformatted in the axial and coronal plane. The basal diameter of the cochlear (A-value) and the outer-wall lengths of the cochlear duct were measured using readily available imaging software. Postoperative plane X-rays were used to determine the degree of electrode insertion and the number of electrodes within the cochlea and speech discrimination scores at 6 months were evaluated. Results. The cochlear metrics obtained were comparable with those previously published in the literature. There was no significant difference in the degree of insertion or speech outcomes between the two electrode lengths. However, when the group who had received the shorter electrode were analysed, there was an association seen between both cochlear duct length and cochlear diameter and speech outcomes. Conclusions. Cochlear size may be a factor in determining speech outcomes that cannot be explained solely by insertion depth or degrees of insertion. Further studies are required to determine if cochlear duct length is an independent predictor of speech outcomes.

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Automatic Cochlear Duct Length Estimation for Selection of Cochlear Implant Electrode Arrays

Otology & Neurotology ◽

10.1097/mao.0000000000001329 ◽

2017 ◽

Vol 38 (3) ◽

pp. 339-346 ◽

Cited By ~ 23

Author(s):

Alejandro Rivas ◽

Ahmet Cakir ◽

Jacob B. Hunter ◽

Robert F. Labadie ◽

M. Geraldine Zuniga ◽

...

Keyword(s):

Cochlear Implant ◽

Electrode Arrays ◽

Cochlear Duct ◽

Length Estimation ◽

Cochlear Duct Length ◽

Selection Of

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Incidence of Complete Insertion in Cochlear Implant Recipients of Long Lateral Wall Arrays

Otolaryngology ◽

10.1177/0194599820987456 ◽

2021 ◽

pp. 019459982098745

Author(s):

Michael W. Canfarotta ◽

Margaret T. Dillon ◽

Kevin D. Brown ◽

Harold C. Pillsbury ◽

Matthew M. Dedmon ◽

...

Keyword(s):

Cochlear Implant ◽

Electrode Array ◽

Lateral Wall ◽

Electrode Arrays ◽

Tertiary Referral ◽

Insertion Depth ◽

Future Studies ◽

Tertiary Referral Center ◽

Cochlear Duct Length ◽

Cochlear Morphology

Objective High rates of partial insertion have been reported for cochlear implant (CI) recipients of long lateral wall electrode arrays, presumably caused by resistance encountered during insertion due to cochlear morphology. With recent advances in long-electrode array design, we sought to investigate (1) the incidence of complete insertions among patients implanted with 31.5-mm flexible arrays and (2) whether complete insertion is limited by cochlear duct length (CDL). Study Design Retrospective review. Setting Tertiary referral center. Methods Fifty-one adult CI recipients implanted with 31.5-mm flexible lateral wall arrays underwent postoperative computed tomography to determine the rate of complete insertion, defined as all contacts being intracochlear. CDL and angular insertion depth (AID) were compared between complete and partial insertion cohorts. Results Most cases had a complete insertion (96.1%, n = 49). Among the complete insertion cohort, the median CDL was 33.6 mm (range, 30.3-37.9 mm), and median AID was 641° (range, 533-751°). Two cases of partial insertion had relatively short CDL (31.8 mm and 32.3 mm) and shallow AID (542° and 575°). Relatively shallow AID for the 2 cases of partial insertion fails to support the idea that CDL alone prevents a complete insertion. Conclusion Complete insertion of a 31.5-mm flexible array is feasible in most cases and does not appear to be limited by the range of CDL observed in this cohort. Future studies are needed to estimate other variations in cochlear morphology that could predict resistance and failure to achieve complete insertion with long arrays.

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