Dependability of Electrode to Modiolus Distance in Patients Specific Electrode Selection: A Cadaveric Model Study

• Published in: The Laryngoscope Vol. 134; no. 11; pp. 4736 - 4744
• Main Authors: Sharma, Vidhu, Das K, Nidhin, Jangra, Anupriya, Tiwari, Sarbesh, Khera, Pushpinder, Soni, Kapil, Dixit, Shilpi G., Nayyar, Ashish K., Goyal, Amit
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-11-2024; Wiley Subscription Services, Inc
• Subjects: cochleostomy; depth of insertion; depth of insertion‐cochlear perimeter ratio; electrode to modiolus distance; Electrodes; round window insertion; depth of insertion; electrode to modiolus distance; cochleostomy; round window insertion; depth of insertion‐cochlear perimeter ratio
• ISSN: 0023-852X; 1531-4995; 1531-4995
• DOI: 10.1002/lary.31565

Objective
This study aims to discern the disparities in the electrode‐to‐modiolus distance (EMD) between cochleostomy and round window approaches when performed sequentially in the same temporal bone. Additionally, the study seeks to identify the cochlear metrics that contribute to these differences.
Methodology
A cross‐sectional study was conducted, involving the sequential insertion of a 12‐electrode array through both round window and cochleostomy approaches in cadaveric temporal bones. Postimplantation high‐resolution CT scans were employed to calculate various parameters.
Results
A total of 12 temporal bones were included in the imaging analysis, revealing a mean cochlear duct length of 32.892 mm. The EMD demonstrated a gradual increase from electrode 1 (C1) in the apex (1.9 ± 0.07 mm; n = 24) to electrode 12 (C12) in the basal turn (4.6 ± 0.24 mm; n = 12; p < 0.01). Significantly higher EMD values were observed in the cochleostomy group. Correlation analysis indicated a strong positive correlation between EMD and cochlear perimeter (CP) (rs = 0.64; n = 12; p = 0.03) and a strong negative correlation with the depth of insertion (DOI) in both the middle and basal turns (rs = − 0.78; n = 20; p < 0.01). Additionally, EMD showed a strong negative correlation with the DOI‐CP ratio (rs = −0.81; n = 12; p < 0.01).
Conclusion
The cochleostomy group exhibited a significantly higher EMD compared with the round window group. The strong negative correlation between EMD and DOI‐CP ratio suggests that in larger cochleae with shallower insertions, EMD is greater than in smaller cochleae with deeper insertions.
Level of Evidence
NA Laryngoscope, 134:4736–4744, 2024
An article describing the variability of electrode to modiolus distance among various window of insertion in cochlear implantation, it's association with various cochlear parameters and its significance in the selection of patient specific electrode.