Comparative anatomical and clinical evaluation of three surgical spaces for contralateral internal carotid artery C7-segment aneurysm clipping: the role of the subchiasmatic-preinfundibular space

OBJECTIVE: This study aims to anatomically define and clinically evaluate the subchiasmatic-preinfundibular space (SCPIS) as an alternative surgical space for clipping contralateral ICA C7-segment aneurysms, by comparing its outcomes with those of the standard prechiasmatic space (PCS) and contralateral opticocarotid space (OCS). METHODS: Basic Research: Five cadaveric heads were dissected via the pterional approach. Contralateral ICA exposure was measured through three spaces- PCS, contralateral OCS), and SCPIS-before and after anterior clinoid process (ACP) drilling. Clinical Research: A retrospective analysis of 53 patients with multiple intracranial aneurysms (MIAs) treated via unilateral craniotomy compared outcomes across three groups: SCPIS (Group 1), PCS (Group 2), and contralateral OCS (Group 3). Postoperative aneurysm occlusion rates, complications, discharge mRS scores, and 6-month neurological deficits were assessed. RESULTS: The lengths of the contralateral ICA exposure increased significantly post-ACP drilling: PCS (5.62 ± 0.91 mm vs. 7.11 ± 0.84 mm, p < 0.001), contralateral OCS (4.44 ± 2.33 mm vs. 6.03 ± 2.30 mm, p = 0.001), and SCPIS (4.98 ± 1.91 mm vs. 6.67 ± 2.01 mm, p < 0.001). Significant increases were also observed in the lengths of the inferior border of the optic chiasm and/or optic nerves, the deep superior border of the diaphragma sellae, and the area of this space after ACP drilling (p < 0.05). SCPIS clipping showed no significant differences in hospitalization duration, complications (pneumonia, electrolyte disturbances, optic nerve injury, cerebral infarction), or discharge mRS scores (p > 0.05) compared to other approaches. The rate of complete angiographic occlusion of the contralateral aneurysms was comparable among the three groups (PCS: 88.6%, OCS: 90.9%, SCPIS: 85.7%; p = 0.92). Six-month neurological outcomes were satisfactory. CONCLUSION: SCPIS is a viable alternative for contralateral ICA C7-segment aneurysm clipping. ACP drilling improves surgical access, and the approach is safe and effective.