Facial recess size estimation using sagittal slices on cone-beam CT for cochlear implantation.

OBJECTIVE

To evaluate sagittal-plane cone-beam computed tomography (CBCT) as a reliable method for estimating facial recess (FR) width, enabling preoperative assessment of posterior tympanotomy (PT) size in cochlear implantation without complex image reconstruction.

BACKGROUND

Posterior tympanotomy provides the surgical corridor for cochlear implantation but carries risk of facial/chorda tympani nerve injury. Accurate preoperative imaging is essential for anticipating surgical difficulty. Although multiplanar and 3D reconstructions can estimate PT dimensions, these require additional technology. The sagittal plane may offer a more intuitive view aligned with the surgeon's operative perspective.

METHODS

A retrospective study of 100 adult cochlear implant candidates was conducted using a standardised CBCT temporal bone protocol. FR width was measured in the sagittal plane from the intraosseous chorda tympani to the second genu of the facial nerve. Measurements were compared with axial-plane values obtained by two consultant radiologists. Statistical analysis used a paired two-tailed t-test.

RESULTS

No statistically significant difference was found between sagittal and axial measurements (p = 0.3851, SEM = 0.02281). Measurements were consistent within 0.05 mm, demonstrating strong concordance.

CONCLUSION

Sagittal-plane CBCT offers a simple, reproducible, and widely accessible method for estimating PT size. It aligns radiological imaging with the surgeon's intraoperative perspective, improving preoperative planning and risk stratification in cochlear implantation.