Correlation of Cochlear Nerve Size and Auditory Performance After Cochlear Implantation in Postlingually Deaf Patients

Abstract

MPORTANCE: Cochlear implantation (CI) yields outstanding results in postlingual deafness, but outcomes of auditory performance after CI are variable. Thus far, it has been difficult to accurately predict patient prognoses after CI. OBJECTIVE: To assess whether cochlear nerve (CN) size as measured with parasagittal magnetic resonance imaging (MRI) is correlated with auditory performance after CI in postlingually deaf patients. DESIGN: Retrospective study. All MRI results were reviewed by the same observer, who was blinded to the participants' information. SETTING: A university tertiary care center. PARTICIPANTS: All 102 postlingually deaf adults who underwent CI during the period August 2010 through June 2012 were eligible to participate. Thirty-four patients were excluded because MRI was not performed or was not of sufficient quality for assessment. Sixty-eight postlingually deaf adults (mean [range] age, 49 [16-77] years) were enrolled. EXPOSURE: Cochlear implantation. MAIN OUTCOMES AND MEASURES: Size of the CN and auditory performance. RESULTS: The mean (SD) cross-sectional area (CSA) of the CN was 0.922 (0.229) mm2 and tended to decrease with age; however, there was no significant correlation between the size of the CN and age. The cause of deafness also did not affect the size of the CSA. However, CSA was negatively associated with both the duration of deafness (P < .001) and degree of hearing loss (P = .008 for the difference in CSA between ears with no more than 80-dB hearing loss [n = 25] and ears with at least 101-dB hearing loss [n = 65]). Interestingly, CSA was positively correlated with auditory performance after CI (P = .04). CONCLUSIONS AND RELEVANCE: We suggest that measuring the size of the CN with parasagittal MRI can yield information that is helpful in preoperative counseling of patients.