Cochlear integrity and scalar translocation assessment after cochlear implantation based on three-dimensional anatomical reconstructions

PURPOSE: Three-dimensional (3D) reconstructions of the cochlea can improve accuracy of assessment of electrode localisation and scalar translocation (STL) of the electrode array of cochlear implants (CIs). The predictive power for STL of the electrode-to-modiolus distance (EMD), the angle of insertion depth (aDOI) and cochlear anatomical dimensions remain unclear.

METHODS: 3D cochlear reconstructions were developed in Materialise Mimics from cone beam CT (CBCT) scans of 28 human cadaveric temporal bones, of which histological assessment of STL was available. The EMD and aDOI were extracted in 3Matic. Cochlear diameter (A), width (B), and height (H) were extracted to calculate cochlear duct length (CDL) and cochlear volume (CV).

RESULTS: Larger EMD values for EMD 1-16 might be associated with increased odds of STL (B = 0.10-1.10, OR = 1.11-3.57, p = 0.07-0.93). Mean cochlear diameter (A) and cochlear height (H) between STL and non-STL cases were comparable (A: STL: 10.23 mm vs. non-STL: 10.10 mm, p = 0.626 and H: STL: 4.50 mm vs. non-STL: 4.33 mm, p = 0.432). Larger cochlear width (B) might be associated with increased odds for STL (B = 1.56, OR = 4.64, p = 0.066). Cochlear width (B) showed significant discriminative ability for STL (AUC 0.72, p = 0.032).

CONCLUSION: 3D cochlear reconstructions may support the CI surgeon in assessment of electrode array placement. No compelling risk factors for STL were identified. Further investigation in a large clinical cohort is advocated.