Cochlear nerve deficiency and associated clinical features in patients with bilateral and unilateral hearing loss.

Objective: To clarify the prevalence and clinical characteristics of cochlear nerve deficiency (CND) in patients with congenital bilateral and unilateral hearing loss.

Study Design: Retrospective case review.

Setting: Tertiary referral center.

Patients: One hundred fourteen children with bilateral and 56 children with congenital unilateral sensoneural hearing loss.

Main Outcome Measures: Review of medical records, audiologic tests, and imaging studies. Imaging studies were evaluated for the presence or absence of abnormalities in the bony cochlear nerve canal (BCNC), internal auditory canal (IAC), and inner ear.

Results: The prevalence of CND, whether unilateral or bilateral, was much higher in the unilateral than in the bilateral hearing loss group: 50% (28/56) versus 5.3% (6/114). Among the 6 children with bilateral hearing loss and CND, 2 had bilateral BCNC stenosis alone, 2 had bilateral BCNC stenosis and unilateral IAC stenosis, 1 had unilateral BCNC stenosis alone, and 1 had unilateral IAC stenosis alone. All 28 children with unilateral hearing loss and CND had BCNC stenosis, whereas 9 (32.1%) also had concurrent IAC stenosis. Three of the 6 children with CND and bilateral hearing loss and 5 of the 28 children with CND and unilateral hearing loss also had other inner ear abnormalities.

Conclusion: Our results suggest differences in the causes and mechanisms of CND in children with bilateral versus unilateral hearing loss.