Endoscopic image-guided transoral approach to the craniovertebral junction: an anatomic study comparing surgical exposure and surgical freedom obtained with the endoscope and the operating microscope.

OBJECTIVE

The transoral approach is the most direct and commonly used method to access the ventral craniocervical junction. Recently, an endonasal, endoscopic approach to the craniovertebral junction was proposed. We reasoned that the coupling of the endoscope with the direct transoral approach and image guidance could result in a minimally invasive, simple approach to the ventral craniovertebral junction. We investigated the potential usefulness of such an approach in a cadaver model.

METHODS

A direct transoral approach to the craniovertebral junction was performed using computed tomography-based image guidance in 9 fresh adult head specimens. Endoscopic odontoidectomy was performed in 5 specimens. In the remaining 4 specimens, the surgical working area and surgical freedom associated with an endoscopic and a microscopic approach to the ventral craniovertebral junction were evaluated and compared. In these 4 specimens, we also measured and compared the exposure of the clivus provided by the endoscope and by the operating microscope without splitting the soft palate.

RESULTS

With variously angled endoscopic assistance and image guidance, it was possible to tailor the excision of the anterior arch of the atlas and to precisely identify the odontoid process and its related ligaments intraoperatively, resulting in a complete and controlled odontoidectomy. The surgical area exposed over the posterior pharyngeal wall was significantly improved using the endoscope (606.5 +/- 127.4 mm3) compared with the operating microscope (425.7 +/- 100.8 mm3), without any compromise of surgical freedom (P < 0.05). The extent of the clivus exposed with the endoscope (9.5 +/- 0.7 mm) without splitting the soft palate was significantly improved compared with that associated with microscopic approach (2.0 +/- 0.4 mm) (P < 0.05).

CONCLUSION

With the aid of the endoscope and image guidance, it is possible to approach the ventral craniovertebral junction transorally with minimal tissue dissection, no palatal splitting, and no compromise of surgical freedom. In addition, the use of an angled-lens endoscope can significantly improve the exposure of the clivus without splitting the soft palate. An endoscope-assisted transoral approach is a direct and powerful tool for the treatment of surgical pathology at the craniovertebral junction.