OBJECTIVE:The aim of this study was to determine and classify inner ear abnormalities in patients who had cochlear implants because of congenital sensorineural hearing loss using preoperative temporal bone computed tomography and magnetic resonance imaging. MATERIALS and METHODS:Patients in the otolaryngology department who had cochlear implants because of congenital sensorineural hearing loss between January 2011 and December 2013 were included in the study. There were 167 male and 133 female patients, a total of 300. All of the patients were evaluated with 4-detector-row computed tomography and 1.5 Tesla magnetic resonance imaging. RESULTS:Inner ear abnormalities were found in 136 of 600 ears (20.3%). There were six ears with incomplete partition-II (4.4%), five ears with incomplete partition-I (3.6%), two ears with Michel deformity (1.4%), two ears with cochlear hypoplasia (1.4%), two ears with cochlear otosclerosis (1.4%), and one ear with common cavity deformity (0.7%). Dilatation of the internal acoustic canal was found in 42 ears (30.9%); also, 21 ears with cochlear nerve aplasia/hypoplasia (15.4%), 5 ears with internal acoustic canal aplasia, and 1 ear with internal acoustic canal hypoplasia (0.73%) were detected. There were 10 ears with posterior semicircular canal (7.3%), 10 ears with lateral semicircular canal (7.4%), 8 ears with superior semicircular canal aplasia/hypoplasia (5.9%), and 8 ears with lateral semicircular canal-vestibular dysplasia. An enlarged vestibular aqueduct was found in 16 ears (11.7%). High jugular bulbs were found in 21 ears; however, this variation was not considered to be an inner ear abnormality. CONCLUSION:Computed tomography and magnetic resonance imaging are essential for the evaluation, determination, and classification of inner ear abnormalities in patients with congenital sensorineural hearing loss who are candidates for cochlear implant operations. Also, these radiological instruments aid in determining contraindications and predicting intraoperative difficulties. Computed tomography and magnetic resonance imaging findings for these patients should be evaluated by an experienced radiologist before the operation.