The Relationship Between Cochleovestibular Orientation, Age, and Sensorineural Hearing Loss: Implications for Cochlear Implantation.

OBJECTIVES

To determine if spatial orientation of the cochlea within the temporal bone is related to age or sensorineural hearing loss (SNHL) and describe the implications for cochlear implantation.

METHODS

Five angles of cochlear orientation were determined from computed tomography (CT) imaging of the temporal bones in adults with (n = 55) and without (n = 27) sensorineural hearing loss (SNHL) and children with (n = 45) and without (n = 12) SNHL: facial recess versus basal turn, posterior semicircular canal versus basal turn, round window versus basal turn (axial view), round window versus basal turn (coronal view), and the cochlear axis versus the mastoid facial nerve.

RESULTS

All angles showed substantial variation between subjects and between ears. The angles between the round window and basal turn (coronal view) and the posterior semicircular canal and basal turn were significantly correlated with age for all subjects with SNHL (r = 0.22, P = .002 and r = 0.15, P = .03, respectively). Patients with SNHL had significantly more acute angles (46.6° vs 55.8°) between the round window versus basal turn (axial orientation) compared to controls (P < .001).

CONCLUSIONS

Cochlear orientation within the temporal bone changes with age and the degree of SNHL. These results suggest that the approach to the round window for electrode insertion might differ between children and adults.