Impact of cochlear nerve deficiency determined using 3-dimensional magnetic resonance imaging on hearing outcome in children with cochlear implants

Abstract

Objectives: 1) To review the radiologic and audiologic data of 656 children with sensorineural hearing impairment who underwent 3-dimensional magnetic resonance imaging (MRI) in our cochlear implant (CI) center to understand the incidence of cochlear nerve deficiency (CND); and 2) to compare postimplant auditory and speech intelligibility outcomes in implantees with cochlear nerve (CN) aplasia, CN hypoplasia, and normal CN.

Study design: A retrospective cohort study.

Setting: A tertiary medical center.

Patients: A total of 656 patients (aged 0-18 yr; mean, 4.5 ± 4.3 yr) who underwent MRI in our center during May 2000 to December 2012.

Main outcome measures: The radiologic/audiologic data were reviewed. The postimplant outcomes of 13 implantees with CND (7 aplasia and 6 hypoplasia) were compared with 50 non-CND implantees using the Categories of Auditory Performance (CAP) and the Speech Intelligibility Rating (SIR) scales.

Results: Upon MRI, 139 patients (21.2%) exhibited CND. Bilateral CN aplasia occurred in 4.3% of the patients with severe-to-profound deafness (588 cases) and in one-fifth of patients with CND. The aplasia group showed significantly worse postimplant CAP (p = 0.002) and SIR (p = 0.009) scores than the non-CND group. No significant difference was noted between the hypoplasia group and the non-CND group.

Conclusion: Although the audiologic and radiologic results may be incompatible, the majority of patients with CND may be well delineated preoperatively using MRI. The type of CND (aplasia/hypoplasia) may affect CI outcomes. Patients implanted on the side with CN hypoplasia are more likely to exhibit favorable results compared with patients implanted on the side with CN aplasia.