Cochlear implantation for inner ear malformations with facial nerve aberrations: A retrospective evaluation of eleven cases.

OBJECTIVE

This study aimed to retrospectively review the anatomical characteristics of aberrant facial nerves and the surgical management of patients undergoing cochlear implantation.

METHODS

Between 1997 and 2022, 658 ears of 485 patients underwent CI surgery at our institute. Among these, we retrospectively reviewed the files of patients with facial nerve aberrations that were confirmed during surgery. Specifically, types of FN aberrations, coexisting inner- or middle-ear malformations were examined using image analysis including three-dimensional computed tomography(3D-CT) images, and types of electrode insertion methods were examined based on operative notes and recorded videoclips for each case.

RESULTS

FN aberrations were observed in 11 ears of 6 cases (1.7%). Inner ear malformations and stapes deformities or absence were observed in all cases. Cochlear malformations and cochlear nerve hypoplasia were observed in six and eight ears, respectively. All cases exhibited inferior displacement of the horizontal segment and anterior dislocation of the vertical segment of the FN.

CONCLUSION

All the cases with FN aberrations identified during CI surgery had middle- or inner-ear or cochlear nerve malformations. Preoperative simulation using 3D-CT images was of great help for the successful electrode insertion in our patients, who had an abnormal FN course and inner ear malformations (IEMs).