Defining the Caudal Limits and Predictors of the Endoscopic Endonasal Approach to the Craniovertebral Junction: A Cadaveric Study

Objective: The endoscopic endonasal approach (EEA), has become the preferred alternative to traditional open and transoral approaches to the intricate craniovertebral junction (CVJ) area. However, the preoperative prediction of the caudal surgical reach remains challenging. This cadaveric study aimed to quantify the CVJ area of exposure afforded by an EEA, evaluate the accuracy of previously described radiographic anthropometric lines, and identify the lowest limit of the EEA corridor.

Materials and Methods: Endoscopic endonasal dissections of the CVJ were completed in 35 cadaveric specimens. The area of exposure and caudal-most reach were measured using a navigation system. Radiographic measurements included the distance of the odontoid process from the hard palate, length of the hard palate, distance of the lowest point reached from the hard palate level, and angles such as the nasopalatine line (NPL) angle, nasoaxial line (NAxL) angle, nostril-hard palate line (NTL) angle, and rhinopalatine line (RPL) angle.

Results: The mean CVJ AoE was 931.22 ± 79.36 mm². The NPL, NAxL, and RPL angles showed significant negative correlations with the distance of the odontoid process from the hard palate line (r = −0.521, p = 0.001; r = −0.538, p = 0.001; r = −0.500, p = 0.002, respectively), while the NTL angle did not (r = −0.241, p = 0.162). No significant correlation was found between achieved AoE via EEA and NPL, NAxL, NTL, or RPL (p > 0.05). Importantly, hard palate length was the sole predictor of CVJ AoE variability (r = −0.416, p = 0.013), with shorter lengths associated with increased exposure. The mean distance of the lowest point reached in the AoE from the hard palate level was 9.47 ± 1.24 mm.

Conclusion: This cadaveric study highlights the variability in CVJ anatomy and the limitations of using previously defined radiographic anthropometric lines for predicting the caudal limits of the EEA. Hard palate length emerged as the only reliable predictor of the surgical area of exposure achievable via the endonasal corridor. Clinical studies are warranted to validate these findings and define the potential need for adjunctive surgical routes in managing complex CVJ pathologies.

 

MissingLinkText

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
07 February 2025