Radiological spectrum of temporal bone, inner ear and brain parenchymal abnormalities in the preoperative cross-sectional imaging of sensorineural hearing loss in cochlear implant candidates: A prospective study
Cochlear implantation is a prudent method of rehabilitation in severe sensorineural hearing loss where other means like hearing aids fail. Not everybody with severe sensorineural hearing loss benefits from implantation, in fact is contraindicated in some. A thorough pre-surgical imaging evaluation of inner ear, temporal bone and cerebral parenchyma is important in decision making, more so as the implants and costs involved are quite expensive. Limited studies exist in the Indian setting. Aim was to evaluate the role of combined computed tomography (CT) and Magnetic Resonance imaging (MRI) in pre operative imaging assessment for cochlear implantation, a prospective study was concluded at the Department of Radiodiagnosis over 30 months (2017 to 2019). Patients with severe hearing loss underwent HRCT temporal bone on 128 slice MDCT and MRI with BFFE, T2/Flair etc. Sequences targeting inner ear, cochlear nerve and brain on 3 Tesla scanner. Data was entered in MS EXCEL and analyzed in SPSS software using cross tabulations or correlation coefficient to compare the two imaging modalities. Chi square and P values were obtained for the cross tabulation data of comparison of CT and MRI in assessment of inner ear structures. The study focused on cochleovestibular malformations, patency of the cochlea-vestibule, cochlear nerve status on MRI and to see if there was any correlation with the bony cochlear nerve canal diameter on CT, isolated or associated brain parenchymal abnormalities and important surgical access criteria like normal variants and altered middle ear anatomy. Abnormal imaging findings were seen in 15 of 32 patients, on the basis of which 5 were rejected for implantation; suboptimal results were predicted in 5 other abnormal cases. Side selection and predicting ease of electrode insertion could also be ascertained in unilateral pathologies. Seventeen cases had normal imaging, twelve of which were operated. Eleven of these had uneventful surgery. All three cases with abnormal imaging, taken for surgery under varied risk of suboptimal results had mild and manageable intraoperative complications. Tailored protocol of MRI with BFFE, T2/FLAIR axials and HRCT temporal bone is an indispensable tool and radiologist plays key role in candidate selection and exclusion, surgical planning and warning surgeon about potential intraoperative complications in cochlear implant surgery.