Anatomical Study for the Trans-Oral Endoscopic Approach to the Dorsum Sellae and Posterior Clinoids

Objective: This study was conducted to investigate the feasibility of an endoscopic trans-oral surgical corridor to the sella turcica, dorsum sellae, and posterior clinoids, preserving the soft palate and the pituitary gland.

Methods: Three cadaveric dissections were performed. First, the soft palate was retracted with rubber catheters passing through both nasal cavities and exiting the mouth. This retraction allowed increased space for instrumentation and visualization between the soft palate and the posterior wall of the nasopharynx. Two 5 mm linear incisions were performed in the submandibular regions bilaterally, 2 cm anterior to the angle of the mandible and 2 cm inferior to its border. A Cottle elevator was used to sharply dissect until the border of the mandible was reached. Medially, a subperiosteal plane was elevated and progressed superiorly until exiting in the mucosa of the floor of the mouth. These tunnels allowed the use of straight endoscopic sinus instruments and drills for the dissection. Under visualization with 30-degree endoscopes through the mouth, the mucosa covering the roof of the nasopharynx was removed and the bone well exposed. Wide inferior sphenoidotomy was completed with the drilling of the sphenoid sinus floor. The intrasphenoidal septations were drilled and the sella turcica was exposed. The sella was subsequently opened using the drill and Kerrison rongeurs, exposing the dura. The dura was elevated posteriorly, revealing the dorsum sella. This was removed together with both posterior clinoids. Finally, the dura was opened and the posterior and inferior aspects of the pituitary gland were well exposed.

Results: It was possible to complete the dissection in all three specimens. The different view of the sphenoid and the sella represented a challenge during the first dissections. The drilling of the sphenoid sinus floor through the trans-oral approach required caution in the posterior-lateral aspect because of the lacerum segment of the internal carotid artery. The safest area to open the sphenoid sinus from below was drilling the vomer posteriorly where it attaches to the sphenoid bone.

The floor of the sella was easily removed. However care needs to be taken close to the posterior-lateral aspect because of the paraclival carotid artery. The bone of the anterior wall of the sella was also possible to be resected. The dorsum sella and the posterior clinoids were removed through this approach with preservation of the pituitary gland and intact dura. The increased distance between the tip of the endoscope and the surgical target during the trans-oral approach was a limitation compared with the shorter distance of endonasal approaches. Another limitation is the need for angled instruments to avoid submandibular incisions.

Conclusion: The trans-oral surgical corridor to the sella and parasellar areas seems to have adequate exposure and access for appropriately angled endoscopes and instruments. A 45-degree endoscope may offer improved visualization and flexibility. This may also be adaptable to trans-oral robotic surgery or the modification cervical trans-oral robotic surgery. Further investigations are warranted.