Role of High-Resolution CT and MRI in Predicting the Degree of Difficulty in Patients undergoing Cochlear Implant Surgery: An Institutional Experience
Introduction Preoperative imaging is a standard practice for cochlear implant candidacy. We are discussing association between surgical feasibility and various anatomical details of middle and inner ear by both high-resolution computed tomography (HRCT) and 3T magnetic resonance imaging (MRI) in patients with bilateral sensorineural hearing loss (SNHL) and are used as a guide during surgery as well as foresee complications in cochlear implantation.
Materials and Methods A total of 56 patients of aged 1 to 5 years (prelingual) and > 1 years (postlingual or perilingual) having bilateral SNHL were included in the study. HRCT temporal bone and MRI head was done in all candidates. Based on the imaging findings of CT and MRI, patients were divided into two categories (normal and abnormal). Demographic and clinical values were compared between two groups. Binary logistic regression analysis was used to identify the predictors of the outcome variable (surgical difficulty).
Results Out of 56 patients, 55 underwent cochlear implantation by Veria technique, one patient having Michel’s deformity was denied surgery and was advised brain stem implant. Note that 69.1% patients had no radiological abnormality, while 30.9% patients showed abnormality including acquired disease and malformation. Out of the total study patients, 18% (n = 10) showed various type of congenital inner ear malformation. Large size of the external auditory canal (EAC), high basal turn angle (BTA), and increased distance between tympanic segment of facial canal to EAC (midpoint between level of I-S joint corresponding to EAC and exit of chordae tympanic at level of EAC), all these factors showed inverse relationship with difficulty in surgery, which were found to be statistically significant.
Conclusion The imaging in cochlear implant patients is an essential tool for preoperative assessment of candidacy, surgical planning, and avoid intra- and postoperative complications. BTA and distance between tympanic segment of facial nerve and EAC (midpoint between level of I-S joint corresponding to EAC and exit of chordae tympanic at level of EAC) are important predictors for evaluating intra- and postoperative complications.
Keywordscochlear implant - imaging - HRCT - MRI - temporal bone - Veria technique - basal turn angle
26 August 2020 (online)
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