The Superior Hypophyseal Artery from the Endoscopic Endonasal Perspective: Anatomical Variations and Surgical Nuances for Its Mobilization and Preservation

Background The endoscopic endonasal approach (EEA) has become a routine corridor to the suprasellar region. The superior hypophyseal arteries (SHA) are intimately related to lesions in the suprasellar space, such as craniopharyngiomas, meningiomas, or pituitary adenomas with suprasellar extension. Previous studies on the SHA have mostly focused on the transcranial perspective as it applies for the treatment of paraclinoidal aneurysms. In this study, we investigate the surgical anatomy and variations of the SHA from the endoscopic endonasal route, and we describe the surgical nuances for safe and effective mobilization and preservation of the SHA when performing surgery in the suprasellar space.

Methods Thirty anatomical specimens with vascular injection were used for endoscopic endonasal dissection. Number of SHAs, origin, course, branching, anastomoses, and areas of supply were collected and analyzed. All medial ICA branches proximal to the origin of the posterior communicating artery (PComA) were defined as SHAs. Selected clinical cases are presented to illustrate the surgical application of the findings.

Results We found a total of 200 SHAs arising from 60 ICAs for an average of 3.3 SHAs arising from each ICA (range: 1–6). The most proximal SHA always coursed in the preinfundibular space, and provided the major blood supply to the infundibulum, inferior aspect of the optic chiasm, and cisternal segment of the optic nerve. We introduce the term primary SHA for this artery. Two-thirds of the primary SHAs originated proximal to the distal dural ring (DDR), with half of them arising from the carotid cave portion of the ICA and the other half proximal to the cave. The typical “candelabra” pattern in three branches (infundibular, recurrent optic, and descending) was found in just a third of primary SHAs. The most common pattern had three or more branches with a tree-like arrangement (42%). The descending branch was absent in 25%, and when present, it supplied the dural diaphragm in 50%, the gland in 43%, and both in 7%. A preinfundibular anastomosis between contralateral primary SHAs was found in all specimens. Distal or secondary SHAs run in the retroinfundibular space and provided supply to the posterior aspect of the pituitary stalk, optic tract, and hypothalamus, and they had anastomoses with primary SHAs and with perforators from PComA.

Conclusion The primary SHA constantly supplies the infundibulum, optic chiasm, and proximal optic nerve. Sacrifice of the primary SHA or its branches should be based on branching and anastomosing pattern. Compromising the main stem or the branches to the optic chiasm and optic nerve may cause a visual deficit. Unilateral injury to the primary SHA will less likely cause endocrine deficits given its abundant anastomoses. Selective sacrifice of the descending branch, when present, will untether the main stem of the SHA facilitating its superior mobilization with low risk of functional consequences. Detailed understanding of the surgical anatomy of SHAs is essential for safe and effective surgery in the suprasellar region.