Contralateral vs. Ipsilateral Approach to Superior Hypophyseal Artery Aneurysms: An Anatomical Study and Morphometric Analysis

Abstract

IntroductionSurgical clipping of superior hypophyseal artery (SHA) aneurysms is a challenging task for neurosurgeons due to their close anatomical relationships. The development of endovascular techniques and the difficulty in surgery have led to a decrease in the number of surgical procedures and thus the experience of neurosurgeons in this region. In this study, we aimed to reveal the microsurgical anatomy of the ipsilateral and contralateral approaches to SHA aneurysms and define their limitations via morphometric analyses of radiological anatomy, three-dimensional (3D) modeling, and surgical illustrations.MethodFive fixed and injected cadaver heads underwent dissections. In order to make morphometric measurements, 75 cranial MRI scans were reviewed. Cranial scans were rendered with a module and used to produce 3D models of different anatomical structures. In addition, a medical illustration was drawn that shows different sizes of aneurysms and surgical clipping approaches.ResultsFor the contralateral approach, pterional craniotomy and sylvian dissection were performed. The contralateral SHA was reached from the prechiasmatic area. The dissected SHA was approached with an aneurysm clip, and maneuverability was evaluated. For the ipsilateral approach, pterional craniotomy and sylvian dissection were performed. The ipsilateral SHA was reached by mobilizing the left optic nerve with left optic nerve unroofing and left anterior clinoidectomy. MRI measurements showed that the area of the prechiasm was 90.4 ± 36.6 mm2 (prefixed: 46.9 ± 10.4 mm2, normofixed: 84.8 ± 15.7 mm2, postfixed: 137.2 ± 19.5 mm2, p < 0.001), the distance between the anterior aspect of the optic chiasm and the limbus sphenoidale was 10.0 ± 3.5 mm (prefixed: 5.7 ± 0.8 mm, normofixed: 9.6 ± 1.6 mm, postfixed:14.4 ± 1.6 mm, p < 0.001), and optic nerves’ interneural angle was 65.2° ± 10.0° (prefixed: 77.1° ± 7.3, normofixed: 63.6° ± 7.7°, postfixed: 57.7° ± 5.7°, p: 0.010).ConclusionAnatomic dissections along with 3D virtual model simulations and illustrations demonstrated that the contralateral approach would potentially allow for proximal control and neck control/clipping in smaller SHA aneurysm with relatively minimal retraction of the contralateral optic nerve in the setting of pre- or normofixed chiasm, and ipsilateral approach requires anterior clinodectomy and optic unroofing with considerable optic nerve mobilization to control proximal ICA and clip the aneurysm neck effectively.

Extended endoscopic endonasal approach to the chiasmatic cistern: An anatomical study of the arachnoid

“…In the IOM, the arterioles supplying the proximal ON move forward along the medial edge of the ON (Figure 3B,D). During surgery, the IOM should be dissected carefully from the middle part to avoid accidentally injuring blood vessels and causing visual impairment (Otawa et al, 2021; Sahin et al, 2022).…”

“…Meningiomas of the tuberculum sellae, craniopharyngioma, suprasellar pituitary adenoma, and SHA aneurysm are the most common lesions found in the CC and adjacent area (Ceylan et al, 2021; Mohyeldin et al, 2020; Sahin et al, 2022; Salek et al, 2020; Yilmaz et al, 2022). The arachnoid of the CC influences the growth pattern of these lesions.…”

Narrative review of patient-specific 3D visualization and reality technologies in skull base neurosurgery: enhancements in surgical training, planning, and navigation

“…These methods convert the segmented 2D slices into digital 3D models, which then undergo refinement. Available software tools (e.g., Materialise 3-matic) allow for smoothing, optimizing mesh structures, and making anatomical adjustments to ensure the digital model's alignment with the original anatomy ( 31 , 34 , 35 ).…”