Anatomical Variations of the Human Cochlea Determined from Micro-CT and High-Resolution CT Imaging and Reconstruction.

Understanding the anatomical variations in the human cochlea is important for cochlear implants. This study examined these variations using a reconstructed fusion model of the skull and temporal bone. The three-dimensional (3D) digital model of the temporal bone was reconstructed from multiple axial micro-computed tomography (CT) scans of temporal bone and high resolution CT of the skull from 15 cadavers. A skull model was reconstructed and merged with the reconstructed temporal bone. The 3D relationship between the cochlea and the skull's mid-sagittal plane was analyzed. The α and β angles of the cochlear autogenous rotation and bottom position, respectively, further subdivided the cochlear spatial orientation. The relationship between the base of the cochlea and the round window was evaluated with the Φ angle. Cochlear size was measured and the relationship was statistically analyzed. Cochlear implant electrode arrays were observed in five cases of right-temporal bone specimens. The α, β, and Φ angles were 46.01 ± 9.65, 56.79 ± 3.58, and 44.41 ± 7.23, respectively. The α angle varied greatly and was negatively correlated to the Φ angle (correlation coefficient = -0.211, P < 0.05). Among the five specimens, the α and Φ angle of the 2R and 4R cochlear specimens was lower and higher than the mean value, respectively. These measurements revealed variations in the size and position of the cochlea. Some of these variations may require surgical adjustments for insertion of electrodes with cochlear implants and present a greater challenge for implantation of cochlear electrode implantation. These data also provide a better understanding of variations in human cochlear anatomy. Anat Rec, 301:1086-1095, 2018.