Application Value of Cochlear Size Assessment in Cochlear Implantation Surgery

Numerous studies using 3D Slicer have enhanced the authors' understanding of anatomical variations in the inner ear. Yet, there is no single report that has analyzed the correlation between cochlear size and cochlear duct length.

High-resolution computed tomography (HRCT) images of 164 structurally normal cochleae underwent reconstruction and threshold segmentation. The reconstructed images yielded measurements of values A, B, C, and D, cochlear height (CH), total cochlear duct length (CDL), length of the 1/2 basal turn (180° CDL), and full length of the basal turn (360° CDL). These cochlear parameters were analyzed and compared between patients with sensorineural hearing loss (SNHL) and individuals with normal bone-conduction (NBC) hearing.

In this study, 82 ears were included in patients with SNHL, the same quantity as NBC cochlear. Age and side showed no significant effect on cochlear dimensions, with males exhibiting larger cochleae than females in both groups. Except for C-value and 180° CDL, all other cochlear parameters differed between groups, indicating a degree of micro-malformation in cochleae of SNHL patients. The A-value, B-value, and CH all showed a positive correlation with cochlear duct length, and the highest correlation was observed for the B-value.

Patients with SNHL are usually accompanied by varying degrees of mild cochlear deformity. The difference in the size of the cochlea between individuals suggests the need for personalized cochlear implantation. The A, B, and D values and CH measurement values can predict CDL, thus guiding the determination of the best implant electrode insertion depth.