Normal Cochlear Nerve Variation in Pediatric Unilateral Hearing Loss and Impact on Cochlear Implant Outcomes

Sunday, October 18, 2026

8:06 AM - 8:12 AM PT

Location: 409AB

Presenting Author(s)

DL

Doreen Lam, MD

Resident Physician
Cleveland Clinic Foundation
Cleveland, Ohio, United States

Co-Author(s)

SA

Samantha Anne, MD, MS

Professor
Cleveland Clinic Foundation
Chagrin Falls, OH, United States
JL

Jonathan Lee, MD

Attending Physcian
Cleveland Clinic Foundation, United States

Senior Author(s)

CK

Christopher Karakasis, MD

Attending Physician
Cleveland Clinic Foundation, United States

Disclosure(s):

Samantha Anne, MD, MS:

faculty for this accredited education activity has no relationship(s) with ineligible companies to disclose.

Introduction: Normal cochlear nerve (CN) size is approximately 1.07±0.3 mm². In bilateral hearing loss, CN size variation correlates with CI performance, and prolonged auditory deprivation is associated with smaller CNs. This study evaluates interaural CN size differences in UHL children, and whether ipsilateral CN size correlates with auditory outcomes after CI. Secondary outcomes include association with duration of deafness and age.

Methods: Retrospective review of UHL children who underwent CI from 2019–2025. Two neuroradiologists measured CN size on reconstructed parasagittal images from preoperative MRIs. Auditory performance was assessed with CNC, AZ Bio and SSQ. Acceptable outcomes are based on thresholds precluding CI candidacy (CNC >50%, SSQ >8, AZ Bio >60%). Logistic regression and Pearson correlation were used for analysis.

Results: 32 patients (mean age=7.7 years, range=2.2–17.1) and 64 ears were identified. Mean CN size of the hearing loss ear (ipsilateral) was 0.92 mm², compared to 1.09 mm² contralaterally. Ipsilateral and contralateral CN sizes were strongly correlated (n=27, r=0.55, p=0.003); however, mean ipsilateral CN size was 0.17 mm² smaller (95% CI=0.08–0.26, p=0.001). CN size difference did not significantly correlate with acceptable outcomes (n=18, OR=1.11, 95% CI=0.69–1.83, p=0.65). Increased age correlated with increased ipsilateral CN size (n=27, r=0.43, p=0.024). There was no significant correlation between ipsilateral CN size and duration of deafness (n=27, r=-0.27, p=0.17) or achievement of acceptable auditory outcomes (n=18, OR=0.70, 95% CI=0.35–1.23, p=0.24).

Conclusions: Children with UHL demonstrate smaller CNs in the affected ear compared to the contralateral ear. CN size increased with age and did not decrease with prolonged duration of deafness. Neither ipsilateral CN size nor interaural asymmetry correlated with acceptable auditory outcomes after CI, suggesting size variation among normal CNs do not influence CI performance. Larger studies are needed to corroborate these findings.