Endoscopic endonasal skull base surgery: Part 1--The midline anterior fossa skull base.

OBJECTIVE: An endonasal endoscopic surgery to the anterior fossa skull base was developed in cadaver dissection as a minimally invasive surgical technique and, subsequently, used in patient treatment. METHODS: Six cadaver head specimens were used. Ideal head positioning and various surgical routes were studied. To estimate the extent of surgical exposure provided by this technique, the width of the exposed anterior cranial fossa was measured between the medial margin of the orbits, the optic nerves and the carotid arteries. Three demonstrative patient cases are presented. RESULTS: Ideal head positioning was discovered to be at 15-degree extension of the forehead-chin line. Paraseptal, middle meatal and middle turbinectomy approaches were developed. The average width between the medial orbits was measured to be 24 mm (range 22-29 mm) at the crista galli level, 27 mm (range 24-30 mm) at the planum sphenoidale, 18 mm (range 15-22 mm) between the optic nerves, and 17 mm (range 13-21 mm) between the rostral carotid siphons. This technique, when it was applied in patient care, proved to be minimally invasive. CONCLUSIONS: This endoscopic endonasal approach provided a direct "short-cut" access to the midline anterior fossa skull base. This technique can be used for the surgical treatment of cerebrospinal fluid (CSF) leak, meningiomas, craniopharyngiomas, pituitary adenomas, and other midline intracranial anterior skull base lesions. This is the first report in the English literature describing endonasal endoscopy for the surgical treatment of primary intracranial anterior fossa skull base lesions.

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 paraseptal, 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.

Endoscopic endonasal skull base surgery: Part 3--The clivus and posterior fossa.

OBJECT: As a minimally invasive surgical strategy, endonasal endoscopy has been implemented for the surgical treatment of clival and midline posterior fossa lesions which conventionally require radical and extensive surgical exposures. A cadaver study was performed and, subsequently, this technique was adopted into patient treatment. METHODS: Six cadaver head specimens were used in this study. Anterior sphenoidotomy was attained by either a paraseptal or middle turbinectomy approach. The ideal head positioning was measured. The clival bone was removed with a high-speed drill from sella to foramen magnum in the vertical dimension and from carotid artery to carotid artery in the transverse dimension. The width of the clival bony window between the carotid arteries was measured at the level of the sellar floor and the caudal end of the carotid artery. The surgical anatomy was studied. RESULTS: Although the middle turbinectomy approach provided a wider surgical corridor, exposure with the paraseptal approach was sufficiently ample. Ideal head positioning was at 15-degree flexion of the forehead-chin line. The average width between carotid arteries at the sellar floor level was 16 mm (range 12-22 mm) and at the lower end of the carotid arteries it was 19 mm (range 14-23 mm). When the dura mater was opened, the anterior view of the pons and medulla with corresponding cranial nerves and vasculature was encountered. Four illustrative patient cases are presented. CONCLUSIONS: This endonasal endoscopy provided excellent surgical exposure from the sella to the foramen magnum at the midline clivus and posterior fossa. Surgical techniques and illustrations of four patients are presented.

Anterolateral approach for cervical spinal cord tumors via an anterior microforaminotomy: technical note.

A cervical spinal cord tumor located anteriorly to the spinal cord is conventionally approached through an anterior vertebrectomy followed by bone-graft reconstruction. In order to make a surgical approach minimally invasive, an anterior microforaminotomy technique is used for removal of a tumor located anterior to the spinal cord. When the senior author's experience increased with anterior microforaminotomy for cervical radiculopathy and myelopathy, it was observed that intradural pathology could also be taken care of through the anterior microforaminotomy which did not require bone fusion or postoperative immobilization. For tumor resection, the anterior foraminotomy is made like a flask-shaped hole, with a smaller outer opening similar to that for radiculopathy but incorporating a larger inner opening to accommodate the extent of the tumor in a longitudinal and transverse dimension. The surgical technique is described with two illustrated patients. Postoperatively, the patients did not require a cervical brace. Although their postoperative discomfort was minimal, they were kept in the hospital overnight postoperatively. Spinal stability was well maintained 6 weeks postoperatively. Postoperative imaging of the spine confirmed resection of the tumors. Anterior microforaminotomy is a minimally invasive microsurgical technique which can provide safe and successful removal of tumors located anteriorly to the spinal cord.