Surgery for superior hypophyseal artery aneurysms: A new classification and surgical considerations

Superior hypophyseal artery (SHA) aneurysms form a unique subgroup of paraclinoid aneurysms having a propensity to grow to a large size in the suprasellar region resulting in compression of the optic nerve, chiasma, and/or tract.

A new classification of SHA aneurysms is proposed that helps in identifying the surgical issues encountered during surgical clipping of these medially directed aneurysms located at different segments of the medial surface of the internal carotid artery (ICA).

This descriptive study was conducted at a tertiary care university hospital.

In 14 patients operated for a SHA (mean age: 49.43 ± 11.28 years; presenting either with subarachnoid hemorrhage (n = 11; 78.57%) or mass effect (n = 3; 21.42%), 4 parameters having a bearing on surgery [a. size: (small <1 cm n = 5, large 1-2.5 cm n = 7, giant >2.5 cm n = 2); b. origin of SHA aneurysmal neck and direction of its fundus; c. relationship of the aneurysm to important neurovascular structures; and, d. whether the aneurysms were saccular or fusiform] were used to divide SHA aneurysms into 7 categories a. Antero-supero-medial (n = 2); b. Antero-infero-medial (n = 1); c. Supero-medial (n = 3); d. Infero-medial (n = 3); e. Postero-medial (n = 2); f. Fusiform (n = 1); and, g. Giant (n = 2). Modified Rankin Scale (MRS) score was utilized to assess outcome [favorable: mRS 0-2; unfavorable: mRS 3-6] at discharge and follow up.

Modified Hunt and Hess grade at admission was 0 = 3; I = 3; II = 3; III = 2; IV = 3 (favorable mRS: 10; 71.42%; unfavorable mRS: 4; 28.57%); and, Fisher grade was I = 3; II = 6; III = 2; IV = 3. Twelve patients required anterior clinoid process drilling/carotid collar opening to facilitate optic nerve mobilization, for proximal ICA control, and to assess the proximal part of the neck of aneurysm for aneurysmal clipping (n = 13) or wrapping (n = 1). Fenestrated clip was applied in 5 patients. In the supero-medial group (antero-supero-medial, supero-medial, and postero-supero-medial), the aneurysmal fundus was found directly below the ipsilateral optic apparatus, elevating it; in the postero-supero-medial group, the fundus often lay in close proximity to A1 artery, Heubner's recurrent artery, ICA bifurcation, or dorsum sellae. Optic pathway, hypothalamic, and medial lenticulostriate perforators also required careful separation. Antero-infero-medial SHA aneurysm was hidden from view, embedded in the anterior wall of sella below tuberculum sellae. At a median follow-up of 17.5 ± 26.78 months (range: 8-84 months), 9 (64.28%) patients had a favorable mRS and 5 (35.71%) an unfavorable one.

Systematically classifying SHA aneurysms and anticipating the surgical risk based upon their anatomical variations helps in achieving a good surgical outcome.