Value of computed tomography in the evaluation of children with cochlear nerve deficiency

OBJECTIVE: To assess the predictive value of high-resolution computed tomography (HRCT) in the evaluation of children with cochlear nerve deficiency (CND). STUDY DESIGN: Retrospective review of medical records. SETTING: Tertiary referral center, hospital setting. PATIENTS: Nineteen children (31 ears) with CND. INTERVENTIONS: Magnetic resonance imaging (MRI), HRCT, and audiologic evaluation. MAIN OUTCOME MEASURES: Comparisons of the morphology of the internal auditory canal (IAC), the bony cochlear nerve canal (BCNC) as seen on HRCT, and audiologic data. RESULTS: Of 12 ears with MRI evidence of an absent cochlear nerve (CN) and a normal-size IAC, all had a patent BCNC as revealed by HRCT. Four of these ears failed auditory stimulation after cochlear implantation, confirming clinically significant CND. Of 15 ears with a narrow IAC and a single nerve visible on MRI, 2 (13.3%) had a normal-size BCNC, 4 (26.7%) were narrow, and 9 (60.0%) were absent. One ear with a narrow IAC, normal BCNC, and a single nerve as revealed by MRI has benefited from cochlear implantation. CONCLUSION: Using BCNC patency, as revealed by HRCT, as a means of identifying CND would miss all cases of absent CNs in the setting of a normal-size IAC. Thus, MRI should be the primary modality for imaging children with severe to profound sensorineural hearing loss. When MRI demonstrates a single nerve within a narrow IAC, the addition of HRCT can further identify more than half of these cases as involving absent CNs because of an absent BCNC. In a subset of patients, CN status remains indeterminate.