Magnetic Resonance Imaging Evaluation for Predictive Factors of Cochlear Nerve Deficiency in Pediatric Cochlear Implant Candidates

The presence of a functioning cochlear nerve fiber is a crucial issue in the preoperative evaluation of pediatric cochlear implant candidates. Correlations between cochlear nerve deficiency and bony abnormalities of the labyrinth or internal acoustic canal (IAC) have not been well elucidated. The purpose of this study was to determine whether an inner ear or IAC anomaly could serve as a reliable predictive factor for the presence of cochlear nerve deficiency. We retrospectively reviewed magnetic resonance imaging (MRI) images of 88 patients with sensorineural hearing loss (SNHL) for the presence of cochlear nerve deficiency, cochlear, vestibular or semicircular canal (SCC) anomalies, endolymphatic duct enlargement, and IAC stenosis. Generalized estimating equations (GEE) logistic regression models were used to determine the predictive factors of cochlear nerve deficiency. MRI demonstrated inner ear or IAC anomalies in 60 of 149 ears (40%) with SNHL, among which 37 presented with cochlear nerve deficiency, 16 had cochlear anomaly, 10 had vestibular/SCC anomaly, 28 demonstrated IAC stenosis, and 18 presented with endolymphatic duct enlargement. Multivariate GEE model demonstrated IAC stenosis and cochlear dysplasia to be positive predictive factors for cochlear nerve deficiency with odds ratios of 23.0 and 16.0, respectively. We concluded that most ears with cochlear nerve deficiency have concurrent anomaly of the bony labyrinth or IAC. In those children with IAC stenosis or cochlear dysplasia which may be detected by CT in advance, MRI should be performed for evaluation of cochlear nerve deficiency.