Endoscopic endonasal skull base surgery: Part 2 - The cavernous sinus

Objective: An endoscopic endonasal approach to the cavernous sinus was developed with cadaver study and, subsequently, has been used in patient treatment. Methods: The endoscopic anatomy, surgical approaches, and ideal head positioning were studied with six cadaver head specimens in order to develop endoscopic endonasal surgery of the cavernous sinus. Three illustrative patient cases are also reported. Results: Horizontal placement of the forehead-chin line of head specimens provided the ideal head positioning for endoscopic endonasal cavernous sinus surgery. Three different surgical approaches were developed to access the cavernous sinus: the pa-raseptal, middle meatal and middle turbinectomy approaches. While the ipsilateral middle meatal approach provided straight anterior exposure, the contralateral paraseptal approach provided anteromedial exposure at the cavernous sinus. The middle turbinectomy approach rendered straight anterior exposure ipsilaterally and anteromedial exposure contralaterally. The sympathetic nerve climbed up on the surface of the carotid artery. When the dura mater was opened at the anterior wall of the cavernous sinus, the S-shaped carotid siphon was exposed. Cranial nerves III and IV were located inside the C-shaped carotid siphon. Cranial nerve VI was just lateral to the inferior arch of the carotid siphon. The ophthalmic branch of the trigeminal nerve was lateral to cranial nerve VI. When used in patient treatment, this technique was observed to be minimally invasive. Conclusion: Endonasal endoscopy for cavernous sinus surgery was studied in cadaver dissection, and subsequently, was used in patient treatment with satisfactory outcomes.