Morphologic Analysis of the Scala Tympani Using Synchrotron: Implications for Cochlear Implantation

Objectives To use synchrotron radiation phase‐contrast imaging (SR‐PCI) to visualize and measure the morphology of the entire cochlear scala tympani (ST) and assess cochlear implant (CI) electrode trajectories. Methods SR‐PCI images were used to obtain geometric measurements of the cochlear scalar diameter and area at 5‐degree increments in 35 unimplanted and three implanted fixed human cadaveric cochleae. Results The cross‐sectional diameter and area of the cochlea were found to decrease from the base to the apex. This study represents a wide variability in cochlear morphology and suggests that even in the smallest cochlea, the ST can accommodate a 0.4 mm diameter electrode up to 720°. Additionally, all lateral wall array trajectories were within the anatomically accommodating insertion zone. Conclusion This is the first study to use SR‐PCI to visualize and quantify the entire ST morphology, from the round window to the apical tip, and assess the post‐operative trajectory of electrodes. These high‐resolution anatomical measurements can be used to inform the angular insertion depth that can be accommodated in CI patients, accounting for anatomical variability. Level of evidence N/A. Laryngoscope , 134:2889–2897, 2024