Outcomes of cochlear implantation in children with the narrow bony cochlear nerve canal.

Objectives: To investigate the diameter of bony cochlear nerve canal (BCNC) as a prog-nostic value of cochlear implantation in children. Subjects and Methods: We collected 327 prelingual deaf children who received coch-lear implantation before five years of age. We reviewed the preoperative temporal bone com-puted tomography (TBCT) and divided into three groups according to the diameter of BCNC: narrow BCNC (Group 1), normal (Group 2), and other anomalies (Group 3). Narrow BCNC group was divided into three groups according to the degree of stenosis: complete stenosis (Group A), less than 0.8mm (Group B), and from 0.8mm to 1.4mm (Group C). For each group, postoperative auditory performances are analyzed according to the diameter of BCNC using the Mann-Whitney U-test. Results: Among the 327 children, 38 children (11.6%) were found to have narrow BCNC (Group 1), 185 children (56.6%) had normal BCNC and inner ear structure (Group 2), and 104 children (31.8%) had other anomalies (Group 3). Group 1 showed less significant improvement in Category of Audiological Performance (CAP) score compared with Group 2 and Group 3. Open-set monosyllabic words test was more deficient in Group 1 than Group 2 and Group 3. Open-set sentence identification test was lower in Group 1 than Group 2 and Group 3. Among the 38 children with narrow BCNC (Group 1), five children had complete stenotic BCNC (Group A), 21 children had BCNC less than 0.8mm (Group B), and 12 children's BCNC di-ameter were from 0.8mm to 1.4mm (Group C). The CAP score of Group A was poorer than the Group B and Group C, and CAP score of Group B was also lower than Group C. Conclusion: The improvement of auditory performance was limited in children with nar-row BCNC and the narrower the BCNC, the more severe the limitation. However, gradual im-provement can be expected. Through these, even children with narrow BCNC need early coch-lear implantation and rehabilitation. This study evidenced the speech perception performance in children having BCNC, which are useful information for preoperative counseling of CI candi-dates and family. [ABSTRACT FROM AUTHOR]