Cochlear Implant Outcomes of Cases with Temporal Bone Malformations

Abstract

Objective: 1) To reveal the relationship between cochlear implant (CI) outcomes and the types of temporal bone malformation.2) To establish a high-resolution CT (HRCT)- based classification of temporal bone malformations for predicting CI outcomes. Method: We retrospectively evaluated 23 deaf children with cochleovestibular and/or internal auditory canal (IAC) malformations who underwent cochlear implantation from 2004 to 2010 at our hospital. Their temporal bone malformations were assessed by HRCT and their CI outcomes were evaluated by speech discrimination scores and category of auditory performance scores. Results: We classified cochleovestibular and IAC malformations into 3 groups by 1) presence of a bony modiolus in the cochlea and 2) patency of cochlear nerve canal (CNC) and IAC. Eleven cases with a bony modiolus and patent CNC/IAC (Group 1) showed excellent CI outcomes and could communicate without visual language, while all of 6 cases with atresia of CNC or narrow IAC (Group 3) needed lipreading or sign language for understanding common phrases, even if their cochleae were well developed. The remaining 6 cases with a cystic cochlea and patent CNC/IAC (Group 2) showed varying CI outcomes depending on maturity of the cochlea. Conclusion: Our classification based on presence of a bony modiolus in the cochlea and patency of CNC/IAC covered the all types of temporal bone malformations including cochleovestibular and CNC/IAC abnormalities and was useful to predict CI outcomes of children with temporal bone malformations.