Endoscopic endonasal skull base surgery: part I - 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-de-gree 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 24-30mm) at the planum sphenoidale, 18mm (range 15-22mm) between the optic nerves, and 17mm (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.