Microsurgical anatomy of the arteries of the pituitary stalk and gland as viewed from above.

The microsurgical anatomy of the arteries of the pituitary stalk and gland as viewed from above was studied in 50 adult cadaveric hemispheres using the operating microscope. There were three types of vessels to the pituitary from above: the superior hypophyseal artery originating from the internal carotid artery, the infundibular artery from the posterior communicating artery, and the prechiasmal artery from the ophthalmic artery. The superior hypophyseal artery originated from the medial to posterior aspect of the internal carotid artery. The average number of vessels of the superior hypophyseal artery was 2.2 per hemisphere, and the diameter was 0.25 mm on average. The majority (76%) of superior hypophyseal arteries arose from the proximal half of the segment between the origins of the ophthalmic and posterior communicating arteries of the internal carotid artery. The infundibular artery originated mainly from the medial side (69%) of the posterior communicating artery. Its diameter was 0.22 mm, and number 0.23 per hemisphere. The number of prechiasmal arteries was 0.06 per hemisphere. As a result, there were on average 2.5 vessels per hemisphere, totally 5 per brain, with the average diameter 0.25 mm, supplying the pituitary stalk and gland from above. The clinical application of these anatomical data to the diagnosis and treatment of suprasellar tumours and carotid-ophthalmic aneurysms is discussed.