The Effect of Cochlear Size on Cochlear Implantation Outcomes

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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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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Radiographic Measurement of Cochlear Duct Length in an Indian Cadaveric Population - Importance of Custom Fit Cochlear Implant Electrodes

International Archives of Otorhinolaryngology ◽

10.1055/s-0040-1701272 ◽

2020 ◽

Vol 24 (04) ◽

pp. e492-e495

Author(s):

Anup Singh ◽

Rajeev Kumar ◽

Smita Manchanda ◽

Ashu Seith Bhalla ◽

Prem Sagar ◽

...

Keyword(s):

High Resolution ◽

Cochlear Implant ◽

Radiographic Measurement ◽

High Resolution Computed Tomography ◽

Insertion Depth ◽

Cochlear Duct ◽

Basal Turn ◽

Significant Difference ◽

Cochlear Duct Length ◽

Temporal Bones

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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Partial Deafness Cochlear Implantation at the University of Kansas: Techniques and Outcomes

Journal of the American Academy of Audiology ◽

10.3766/jaaa.21.3.8 ◽

2010 ◽

Vol 21 (03) ◽

pp. 197-203 ◽

Cited By ~ 30

Author(s):

Sandra Prentiss ◽

Kevin Sykes ◽

Hinrich Staecker

Keyword(s):

Hearing Loss ◽

Cochlear Implantation ◽

Signal To Noise Ratio ◽

Hearing Preservation ◽

Residual Hearing ◽

Speech Discrimination ◽

Insertion Depth ◽

Low Frequencies ◽

Hearing In Noise ◽

Electrode Insertion

Background: One of the most significant recent advances in cochlear implantation is the implantation of patients with residual hearing. These patients have a downsloping sensorineural hearing loss with poor speech discrimination and perform poorly with standard amplification. Studies using a variety of different electrode designs have demonstrated that it is possible to implant an inner ear and preserve residual hearing. Initial studies have demonstrated that a combination of residual acoustic hearing in the low frequencies with electrical stimulation in the mid- to high frequencies resulted in superior hearing performance in background noise. Purpose: The objective of this study was to determine the effect of electrode insertion depth on hearing preservation. Study Sample: Eighteen patients with mild to severe hearing loss in the low frequencies combined with poor word recognition were recruited for the study. Intervention: Cochlear implantation. Data Collection and Analysis: Pre- and postoperative hearing test, Hearing in Noise Test, and consonant–nucleus–consonant testing. Data analysis was performed with Kruskal Wallis and Mann-Whitney testing. Results: In our study of 18 patients implanted with a Med-El PulsarCI100 we demonstrated the ability to preserve residual hearing with implant insertion depths ranging from 20 to 28 mm, giving us the possibility of near complete cochlear frequency coverage with an implant array while preserving residual hearing. These patients performed well both in quiet and in 10 dB signal-to-noise ratio conditions. Conclusion: Hearing preservation was achievable even with deep implant insertion. Patients performed well in combined acoustic and electric conditions.

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