Predicting Basal Cochlear Length for Electric-Acoustic Stimulation

Abstract

To assess the feasibility and accuracy of predicting electrode insertion depth necessary in cochlear implantations for electric-acoustic stimulation by means of preoperative high-resolution computed tomography (HRCT). Human temporal bone study with evaluation of cochlear dimensions. Tertiary care medical center. Eight fresh human temporal bones were scanned, and basal cochlear structures were reconstructed and measured. Standard cochlear implantations with a free-fitting array were performed, and the bones then underwent histologic analysis using a technique that allows sectioning of undecalcified bones. After embedding, all bones underwent conventional radiologic analysis with further insertion measurements. Preimplantation HRCT data were compared with radiologic and histologic data. Preimplantation HRCT-based measurements correlated very well with postimplantation radiologic data. A mean failure of 0.3 mm was found. Mean values for the first 360 degrees ranged from 18.8 to 22.0 mm. Preimplantation HRCT-based prediction of cochlear implant insertion depths is both feasible and accurate. It is especially useful when aiming for hearing preservation, where insertion depths of 360 degrees are necessary.