Surgical anatomy of the superior hypophyseal artery and its relevance for endoscopic endonasal surgery.

OBJECTIVE: The endoscopic endonasal approach has become a routine corridor to the suprasellar region. The superior hypophyseal arteries (SHAs) are intimately related to lesions in the suprasellar space, such as craniopharyngiomas and meningiomas. Here the authors investigate the surgical anatomy and variations of the SHA from the endoscopic endonasal perspective.

METHODS: Thirty anatomical specimens with vascular injection were used for endoscopic endonasal dissection. The number of SHAs and their origin, course, branching, anastomoses, and areas of supply were collected and analyzed.

RESULTS: A total of 110 SHAs arising from 60 internal carotid arteries (ICAs), or 1.83 SHAs per ICA (range 0-3), were found. The most proximal SHA always ran in the preinfundibular space and provided the major blood supply to the infundibulum, optic chiasm, and proximal optic nerve; it was defined as the primary SHA (pSHA). The more distal SHA(s), present in 78.3% of sides, ran in the retroinfundibular space and supplied the stalk and may also supply the tuber cinereum and optic tracts. In the two sides (3.3%) in which no SHA was present, the territory was covered by a pair of infundibular arteries originating from the posterior communicating artery. Two-thirds of the pSHAs originated proximal to the distal dural ring; half of these arose from the carotid cave portion of the ICA, whereas the other half originated proximal to the cave. Four branching patterns of the pSHA were recognized, with the most common pattern (41.7%) consisting of three or more branches with a tree-like pattern. Descending branches were absent in 25% of cases. Preinfundibular anastomoses between pSHAs were found in all specimens. Anastomoses between the pSHA and the secondary SHA (sSHA) or the infundibular arteries were found in 75% cases.

CONCLUSIONS: The first SHA almost always supplies the infundibulum, optic chiasm, and proximal optic nerve and represents the pSHA. Compromising this artery can cause a visual deficit. Unilateral injury to the pSHA is less likely to cause an endocrine deficit given the artery's abundant anastomoses. A detailed understanding of the surgical anatomy of the SHA and its many variations may help surgeons when approaching challenging lesions in the suprasellar region.