Introduction: The management of complex paraclinoid aneurysms is challenging due to their relation to critical neurovascular structures. Both endovascular and microsurgical treatment may require parent artery sacrifice, leading to hypo-perfusion or occlusion of the ophthalmic artery (OpA). Despite the current therapeutic options and the extracranial collateral circulation to the intraorbital OpA, ischemia leads to irreversible visual sequelae in 3-38% of patients. In this anatomical study, we aimed to evaluate the feasibility of an intracanalicular OpA (iOpA) revascularization using the superficial temporal artery (STA) as a donor to prevent ischemic injury of the optic nerve.

Methods: A pterional approach was performed on ten cadaveric specimens, followed by an extradural anterior clinoidectomy and drilling of the of optic canal. Subsequently, the dura was opened and the intradural and iOpA were exposed. An end-to-end bypass was performed from the frontal branch of STA to the iOpA. The distal caliber of STA and iOpA was measured. The required length of donor artery and the lateral displacement of iOpA was recorded.

Results: Excellent exposure of the iOpA was achieved, in each specimen. The length of the iOpA was 9.48±2.0 mm. The mean calibers at the anastomotic site of STA were 1.92±0.4 mm and 1.63±0.3 mm of iOpA. The length of the required STA graft for a tension-free bypass construct was 89.9±9.7 mm with lateral iOpA displacement of 7.51±2.45 mm.

Conclusions: Till date, no revascularization techniques for the OpA are have been reported. In this novel study, we describe demonstrate the feasibility of an STA-iOpA bypass. This technique may be useful to avoid optic nerve ischemia while treating complex paraclinoid aneurysms, infiltrative tumors or OpA injury. The application applicability of this bypass, however, has is yet to be established with clinical studies.

Patient Care: This novel extracranial-intracranial revascularization technique could be a therapeutic option for blood flow preservation, if proximal occlusion of the ophthalmic artery is required while treating complex paraclinoid aneurysms.

Learning Objectives: 1. Surgical anatomy of the paraclinoid neurovascular structures. 2. Feasibility of superficial temporal artery-to-intracanalicular ophthalmic artery bypass 3. Morphometric description of the intracanalicular ophthalmic artery and the superficial temporal artery

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