Abstract
Five patients with small ophthalmic segment aneurysm arising from the postero (infero)-medial wall of the internal carotid artery were operated on through a contralateral pterional approach. Based on the angiographic and operative findings, the generation of the aneurysms in this location was examined with reference to the origin of the superior hypophyseal artery (SHA).The aneurysm necks were less than 7 mm in size and located a little distal to the origin of the ophthalmic artery. Through the contralateral approach after securing the internal carotid artery at the neck, dissection and clipping of the aneurysms were performed without difficulty. The SHA was clearly recognized in close proximity to the aneurysm in every patient. However, the SHAs were so fine and intimately related with aneurysms that it was impossible to preserve them in 3 patients. Postoperative recoveries were uneventful in all of the patients, though the internal carotid artery was occluded at the aneurysmal clip in 1 patient in whom nasal lower quadrant anopsia in the ipsilateral eye remained.
The operative findings revealed that the SHA originated from the posteromedial wall of the internal carotid artery just proximal to an aneurysm in 4 cases and from the medial wall a little apart from aneurysm in 1 case. The SHAs ran posteriorly around the aneurysmal dome and uniformly terminated in 2 branches, 1 to the inferior aspect of the optic nerve and chiasma, another to the pituitary stalk. These findings indicate the aneurysms are generated mainly based on a vulnerability of the arterial wall at the crotch of the SHA rather than a hemodynamic stress, and support the terminology 'superior hypophyseal artery aneurysm' for the aneurysms in this location.
Clinically, neither pituitary dysfunction nor visual disturbance was caused by an operative occlusion of the unilateral SHA in almost all the reported cases of ophthalmic segment aneurysms, including the present cases. Abundant arterial anastomoses in the suprasellar region as were demonstrated in detail by Marincovic et al. may account for the favorable surgical results. Thus, at the operation of ophthalmic segment aneurysms projecting posteromedially, surgeons should concentrate on complete neck clipping without being overcautious in preserving the superior hypophyseal artery.
