MATERIAL and METHODS: The endoscopic anatomy of the nasal cavity, sphenoid sinus and the sellar region was studied in 30 fresh cadavers (mean age 42.1 / range 18-66) and dissections were performed in a stepwise manner to simulate EETSA to the sellar region.

RESULTS: The sphenoid ostium, located 14.9 mm superior to the choana, was identified at the midpoint between the nasal septum and the superior turbinate in 23 specimens. The shape of the sphenoid ostium was linear (35%), fusiform (30%), oval(22%) or circular (13%). The mean width of the pituitary gland was 14.3 mm and the average minimum distance between the internal carotid arteries on both sides ranged between 13 to 22 mm. Following total hypophysectomy in 12 specimens, the width and length of diaphragma sellae was measured 10.83 and 5.83 mms respectively.

CONCLUSION: This study documents that variations are common in nasal, sphenoidal and sellar phases of the trans-sphenoidal approach. Detailed knowledge of the basic anatomical relationships through the view of the endoscope and performing endoscopic dissections in large number of specimens will facilitate the endoscopic surgical procedures and decrease the rate of surgical complications. Keywords : Endoscopic approach, Pituitary tumour, Transsphenoidal surgery, Skull-base surgery, Surgical anatomy