Assessment of preoperative computed tomography and magnetic resonance imagings in cochlear implant candidates

Cochlear implantation is considered an acceptable treatment for severe to profound sensorineural hearing loss in patients who are refractory to conventional hearing aids. The assessment with preoperative computed tomography (CT) and magnetic resonance imaging (MRI) is very important, because absence of the cochlea or cochlear nerve is a contraindication for implantation. Moreover, the etiology of the hearing loss, and variations can be determined by radiographic assessment, thus the probable complications and success of implantation can be estimated. Our aim in this retrospective study was to present our preoperative CT and MRI findings, and to discuss possible inner ear pathologies, variations and our results under the light of the literature.A hundred cochlear implant candidates who underwent CT or MRI in our Radiology Department were evaluated. In our archive, we had only CT records of 44 patients, and both CT and MRI records of 56 patients. After the assessment of CT examinations, we detected congenital cochleovestibular anomalies in 46 ears of 23 patients (23%), and acquired cochleovestibular pathologies in 9 ears of 5 patients (4.5%). There was no difference between the modalities in classification and determination of cochlear anomalies. Bony detail of the temporal bone, position of facial nerve in the temporal bone, and the jugular bulb can only be demonstrated by CT. Direct viewing of cochlear nerve, and detecting central brain lesions were possible only by MRI, which also had advantages in detecting early obliteration of the cochlea.As a result, both modalities offer different but complimentary information on inner ear anatomy. Thus, we think both CT and MRI should be performed for preoperative radiologic assessment of cochlear implant candidates.