Comparison of Extraoral and Transoral Approaches to the Craniocervical Junction: Morphometric and Quantitative Analysis

BACKGROUND: The transoral (TO) approach to the craniocervical junction provides similar access to the periclival and subaxial spine compared with the extraoral anterolateral prevascular (EAP) approach, but the additional exposure gained by the EAP approach has not been quantified. This study quantitatively compared the two surgical exposures. METHODS: Ten silicon-injected fixed cadaver heads were used for the TO approach and another 5 heads (10 sides) were dissected for the EAP approach. For the TO approach, mouth opening was standardized to 5.5 cm using a Spetzler-Sonntag retractor, and the soft palate was split 1.5 cm to access the periclival area. A frameless stereotactic device was used to calculate the lengths, angles, and areas of surgical exposure for different anatomic targets. RESULTS: The vertical working length on the dura progressively increased 61% (336 +/- 26 mm to 539 +/- 16 mm [mean +/- standard deviation]; P < 0.001), and the vertical working angle increased 23% (98 +/- 3 degrees to 121 +/- 5 degrees; P < 0.0) using the TO versus the EAP approach. In the TO approach, the bilateral average horizontal working length on the C1 arch was less on the ipsilateral side than for the EAP approach (11 +/- 1 mm vs. 17 +/- 1 mm, 61%; P < 0.01). The mean periclival and subaxial exposures were 546 +/- 72 mm(2) and 932 +/- 70 mm(2) with the TO approach and 874 +/- 75 mm(2) and 1644 +/- 107 mm(2) with the EAP approach (mean increases 62% and 77%, respectively; both P < 0.001). CONCLUSIONS: Both the TO and EAP approaches improved surgical exposure, but the EAP approach provides more significant and consistent gains to the anterolateral periclival and subaxial areas.