Axial and Coronal Cochlear Aperture Measurements and their relationship with Internal Auditory Canal and Cochlear Nerve.

Abstract

Background: the relationship of the cochlear aperture, internal auditory canal and the cochlear nerve, has not been finalized as there is a wide range for normative values for cochlear aperture between 1.2 mm and 1.9 mm. Materials and Methods This study was performed between 2020-2024 on 1241 ears with Incomplete partitions (types I, II and III), cochlear hypoplasia and normal cochlea with cochlear aperture abnormalities. There were 158 ears with normal anatomy as the control group. Cochlear aperture is measured on axial midmodiolar section and coronal sections. Internal acoustic canal midpoint measurement is made perpendicular to the canal at the midpoint. Cochlear nerve was graded under 4 categories: 1-Normal 2-Mild hypoplasia 3-Hardly visible 4-Aplastic Results: Cochlear nerve hypoplasia and aplasia are most frequently encountered in cochlear hypoplasia and cochlear aperture abnormality groups. There is statistically significant, positive and strong relationship between axial and coronal measurements of cochlear aperture. However, both axial and coronal measurements show significant differences among groups: values for normal group are significantly higher than cochlear hypoplasia and cochlear aperture abnormality groups, and lower than Incomplete partition groups (types I, II and III). There is a strong relationship between cochlear aperture and the status of the cochlear nerve. Conclusion There is a relationship between cochlear aperture measurements and cochlear nerve status. If the axial measurement is less than 1.26 mm and coronal measurement less than 1.30 mm there is a high chance of CN aplasia.

Key words: inner ear malformations, cochlear aperture, internal auditory canal, cochlear nerve deficiency, cochlear nerve aplasia.