Importance of preoperative HRCT temporal bone in the orientation of the cochlea and its relation to intra-operative difficulties in cochlear implantation – predicting the grades of difficulty

Abstract

Objective: This study emphasizes the role of preoperative high-resolution computed tomography (HRCT) temporal bone in evaluating the variation in cochlear orientation and proposes a grading system to determine the level of intraoperative difficulties encountered. Methods: Preoperative correlation of middle ear and inner ear structures along with the basal turn angle (BTA) was done to assess the orientation. Patients were divided into three groups depending on BTA and radiology findings. Results: Group A (BTA = 55°-60°) had statistically significant (p < 0.05) correlation between middle ear to inner ear structures on HRCT, whereas group B (BTA >60°) and C (BTA <55°) had variations in the alignment of middle ear structures to their corresponding inner ear structures. Conclusion: The association of BTA to the correlation between middle ear and inner ear structures can determine the orientation of the cochlea. This evaluation makes the surgeon aware of intraoperative challenges and helps in surgical planning.