Neural Response Telemetry Thresholds in Patients with Cochlear Nerve Canal

Objective. To explore neural response telemetry (NRT) thresholds in patients with stenotic versus normal cochlear nerve canals. Study Design. Case series with chart review. Setting. Tertiary referral center. Subjects and Methods. Thirty pediatric patients with profound sensorineural hearing loss in at least 1 ear and no benefit from amplification underwent computed tomography imaging of the temporal bones. They were divided into 3 groups according to the diameter of the cochlear nerve canal: group A, \1.5 mm; group B, 1.5 to 1.7 mm; group C, 1.8 to 2.1 mm. All patients underwent cochlear implantation with full insertion of all electrodes. NRT was performed both intraoperatively and 6 months postoperatively in all patients; thresholds of electrodes 1, 11, and 22 were compared. Results. Per analysis of variance, intraoperative and 6-month postoperative NRT thresholds were both significantly different among groups A, B, and C at electrodes 1 and 22 but not at electrode 11. On intergroup analysis, group A showed statistically higher thresholds than those of groups B and C; however, no difference was found between groups B and C. Conclusion. Cochlear nerve canal stenosis, defined as a canal diameter \1.5 mm, is associated with significantly increased NRT thresholds, which may play a role in postimplant performance.