Anatomical significance of the vestibular aqueduct in posterior wall of the internal auditory canal drilling through the retrosigmoid approach: a study utilizing 3D reconstruction technology

The anatomical importance of the vestibular aqueduct and posterior semicircular canal is explored in this study, which utilizes three-dimensional(3D) image reconstruction and registration fusion technology through the retrosigmoid approach for drilling the posterior wall of the internal auditory canal. A total of 200 temporal bone high-resolution computed tomography (HRCT) scans were collected from 100 patients without inner ear diseases at the Central Hospital of the PLA's Neurosurgery and Radiology Department between 2016 and 2024. Additionally, temporal bone HRCT and brain MRI imaging data were also collected concurrently from 32 patients diagnosed with vestibular schwannomas. The primary focus of this research is on 3D reconstruction and fusion registration of temporal bone HRCT and brain MRI images to accurately display and measure the anatomical structures as well as provide spatial positioning data in 3D dimensions for important structures such as the vestibular aqueduct, posterior semicircular canal, tumors, among others. Several important anatomical measurements were obtained using the 3D Reconstruction and fusion Technology. In non-tumor patients, the internal auditory canal measures (8.408 +/- 1.078 mm), with P-1 (defined as the pole located near the posterior region on the long axis of an elliptical opening in the inner auditory canal) to vestibular aqueduct being (9.450 +/- 1.522 mm) and to posterior semicircular canal being (10.348 +/- 1.542 mm). In vestibular schwannoma patients, these dimensions change to (7.977 +/- 0.903) mm, (7.598 +/- 1.223 mm), and (8.687 +/- 1.061 mm) respectively. Statistical analysis shows significant differences (p = 5.7416e-10 < 0.05, p = 5.8961e-9 < 0.05, p = 6.0e-6 < 0.05). ROC analysis sets a threshold of 8.438 mm from the internal auditory canal to the vestibular aqueduct, warning of caution near 8 mm during surgery to prevent vestibular aqueduct damage. In patients with vestibular schwannoma, the distance from the posterior internal auditory canal to the vestibular aqueduct is shorter compared to that of the posterior semicircular canal, implying a higher likelihood of damaging the vestibular aqueduct when eroding the posterior internal auditory canal during surgery.