Is software-based measurement of cochlear duct length based on MRI images reliable in children before CI surgery?

The optimal electrode coverage of the cochlea by CIs is discussed controversially. Besides residual hearing, it is influenced by the cochelar duct length (CDL). The CDL is measured normally with CT images. In children, CT imaging bevor CI surgery is usually not performed for radiation protection. In this study, we used CT and MRI images to compare whether CDL in children can be reliably determined by MRI. A total of 56 cochleae of 12 adults and 16 children under 2 years of age were measured retrospectively using the Otoplan planning software (CAScination & MED-EL) and the CDL was determined using the software-based elliptic circular augmentation (ECA) equation. Thin-slice temporal bone CT or DVT and T2 weighted MRI ci3d images were used and compared for the measurement. The CDL in adults was 34.87 mm ± 2.43 (29.36 – 38.29 mm) in CT and DVT, respectively, and 34.40 mm ± 2.19 (29.6 – 37.21 mm) in MRI. The CDL in children was 35.97 mm ± 1.81 (32.96 – 39.96 mm) in CT and 35.25 ± 1.64 (32.12 – 37.58 mm) in MRI measurements. There was no significant difference in CDL between adults and children in CT and MRI measurements (CT: p= 0.077; MRI: p = 0.109). There were also no differences between CT and MRI measurements in both adults and children (adults: p = 0.496; children: p = 0.111). The CDL varies in both adults and children to an extent that may require individual electrode selection for optimal electrode coverage. Since there is no routine scan for children prior to CI surgery, the CDL can also be reliably determined by MRI in order to select the optimal electrode length.

Publication History

Article published online:
12 May 2023