INTRODUCTION According to the degree of hearing loss, congenital sensorineural hearing loss (cSNHL) is observed in 1-3 of every 1,000 live births [1] [2] . Although the inner ear structures of 80% of these patients are detected to be normal by temporal bone computed tomography (CT) and magnetic resonance, inner ear malformation can be detected in 20% of those patients [3] . Radiological examination is used to establish cases with contraindications as well as the pathologies encountered during

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... rgery in patients with advanced hearing loss who are candidates for cochlear implants. Also, radiological examination has a role in the decision of which ear is preferable [4] [5] [6] . Computed tomography and magnetic resonance imaging (MRI) are the two most important radiological examination techniques to evaluate patients prior to implantation. To display the bone labyrinth and internal auditory canal (IAC), the high resolution temporal bone CT technique is the first priority. Temporal bone CT provides detailed information about the condition of the otic capsule, cochlea, vestibule, oval and round window, and semicircular canals as well as the course of the facial nerve, IAC, vestibular aquaduct (VA), and cochlear aqueduct (CA) [7] . To establish the presence of the nerves inside the IAC and to determine their diameters, a temporal bone MRI examination is performed [8] . Our aim in this study was to use temporal bone CT and MRI to evaluate the inner ear formations and malformations of patients due to receive cochlear implants (CIs) because of cSNHL and to determine the contraindications for CI. 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.