Modifications of the transoral approach to the craniovertebral junction: anatomic study and clinical correlations

This study was designed to more precisely characterize the changes in exposure achieved by modifying the standard transoral approach by sequential mandibulotomy and mandibuloglossotomy with or without palatotomy.

A series of cadaveric dissections was performed and the operative distance and angle of exposure in both axial and sagittal planes was evaluated for each approach, with and without palatotomy. Intraoperative measurements were made in patients undergoing transoral approaches to assess the validity of the anatomic model. The use of this model was then assessed by a retrospective analysis of a group of 19 patients operated on through transoral approaches between 1991 and 2006.

The simple transoral approach exposed the region from the lower third of the clivus to the middle of the C2 vertebral body at an operative distance of 12.9 +/- 1.0 cm from the dura. The axial and sagittal angles of exposure were 39.4 +/- 3.5 degrees and 36.8 +/- 3.5 degrees, respectively. Mandibulotomy significantly increased the sagittal exposure to 59.0 +/- 1.0 degrees (P < 0.001), exposing the area from the midclivus to the C2-C3 interspace while simultaneously increasing the axial angle of exposure to 51.9 +/- 7.4 degrees (P < 0.01) and decreasing the operative distance to the dura to 10.7 +/- 1.7 cm (P < 0.05). Mandibuloglossotomy augmented sagittal exposure to 85.3 +/- 0.3 degrees (P < 0.001), revealing the region between the upper one-third of the clivus and the C4-C5 interspace (P < 0.001) while decreasing the operative distance to the dura to 8.7 +/- 0.3 cm (P < 0.05). Palatotomy significantly increased the rostral exposure achieved by each approach by 8.5 to 12.3 degrees (P < 0.01) without altering caudal or axial exposure or the operative distance.

The cadaveric data correlated well with intraoperative measurements and the need for modifications of the transoral approach in 15 of the 16 adult patients (93.8%). Pediatric patients, patients with limited mouth opening, elevated craniovertebral junctions, and particularly deep lesions required more extensive exposure. This analysis may be useful for determining the optimal approach for patients undergoing transoral surgery.