Objectives: The presence of a functional cochlear nerve is a key issue in the preoperative evaluation of pediatric candidates for cochlear implants. Correlations between cochlear nerve deficiency (CND) and bony abnormalities of the labyrinth or bony canal of the cochlear nerve are not yet well understood. The aim of this study was to determine whether the width of the bony cochlear canal (BCNC) can serve as a reliable predictive factor for the existence of a CND. Materials and methods: A total of 11 children with a confirmed diagnosis of prelingual, severe sensorineural hearing loss were included in this study. In all patients, indication for CI was confirmed and according to the preoperative protocol, high-resolution CT and MR were performed. Reconstructions at a distance of 0.6 mm of the axial plane and images from the HRCT of temporal bones were used for measuring the width of the BCNC. The cochlear nerves were evaluated on axial and sagittal – oblique T2 – MRI images and classified as normal, hypoplastic or aplastic. Two factors were reviewed retrospectively: the presence of inner ear anomalies and the relationship between BCNC stenosis and the existence of CND. Results: From a total of 22 temporal bones analyzed (22 ears in 11 patients), inner ear malformations were detected in 6 ears from 3 patients (27.27%). All three children had a bilateral malformation, in one it was Michel deformity and in two it was IP2 (incomplete partition 2). The BCNC diameter ranged from 0.1mm to 2.33mm with a mean value of 1.46±0.6mm. CND was recorded in 4 of 22 ears and all were associated with stenosis of the BCNC. In a total of three ears with a stenotic canal, we obtained a normal finding for the cochlear nerve on MR. Conclusion: Children with BCNC stenosis have a high incidence of CND. A narrowed BCNC on CT can be an indicator for the selection of children with sensorineural hearing loss who will need to be additionally referred for MRI in order to definitively assess the status of the cochlear nerve.

Introduction:The aim of this study was to evaluate the width of the bony cochlear nerve canal (BCNC) in children with congenital sensorineural hearing loss (SNHL) and "normal" findings on thin section temporal bone CT.Material and methods: The width of the BCNC was retrospectively evaluated in two groups of patients. The study group included 11 children (22 bone canals) aged 2-12 years, with congenital, bilateral SNHL who underwent cochlear implantation (CI) from July to December 2019 and no abnormalities of the inner ear were detected on their preoperative CT scans. Eleven patients (22 bone canals), aged 3-10 years, in whom no sensorineural hearing loss had been diagnosed were taken as controls and CT scan of the temporal bone was performed for another reason -suspected acute mastoiditis, chronic otitis media, or perforation of the tympanic membrane. Axial sections of their CT scans were used to measure the width of the BCNC.Results: BCNC width values in patients with bilateral, profound sensorineural hearing loss ranged from 1.0 to 2.3 mm and the mean value was 1.5±0.3 mm. In patients with normal hearing, the values for the canal width were higher, with mean value of 2.1±0.3 mm. Conclusion:The results obtained showed that the width of the BCNC in children with bilateral, profound sensorineural hearing impairment was significantly smaller than in the control group with normal hearing for p <0.05 (t-test=6.62912, p=0.000000).