Introduction: Endoscopic endonasal approaches (EEA) are being increasingly used for treatment of various skull base pathologies, including intracranial aneurysms. However, few anatomical assessments have been performed on the use of EEA for treating paraclinoid aneurysms.
Methods: Five cadaveric heads underwent endoscopic endonasal transplanum-transtuberculum approach to expose the paraclinoid area. Feasibility of obtaining proximal and distal control over the internal carotid artery (ICA), as well as the topographic location of the origin of the ophthalmic artery (OphA) using several dural landmarks were assessed bilaterally. Limitations of the EEA in exposing the supraclinoid ICA were recorded to identify favorable paraclinoid ICA aneurysm projections to be treated using EEA.
Results: Favorable segments of the ICA to obtain proximal control included the extracavernous paraclival and clinoidal ICA. Clipping the extracavernous ICA put the trigeminal and abducent nerves at risk, whereas clipping the clinoidal segment put the oculomotor nerve at risk. The OphA origin was found within 4mm of the medial opticocarotid point on a line connecting the mid-tubercular recess point to the medial vertex of the lateral opticocarotid recess. Safe application of a distal ICA clip was possible at an average length of 7.2mm of the supraclinoid ICA. Relatively small superiorly or medially projecting paraclinoid aneurysms were favorable candidates to be clipped via EEA.
Conclusions: When performed to approach paraclinoid aneurysms, EEA carries certain risks to adjacent neurovascular structures during proximal control, dural opening, and distal control. However, a small subset of these aneurysms may be amenable to clipping using EEA.
Patient Care: This project contributes to the assessment of the utility of EEA to treat paraclinoid aneurysms. Based on our analysis, we could establish safe sites for clip application for proximal and distal control of the ICA. Small superiorly or medially projecting paraclinoidal aneurysms can be more favorable to be treated via EEA.
Learning Objectives: (1) Providing a comprehensive anatomical assessment of the EEA for treatment of paraclinoid aneurysms.
(2) Designating safe sites for clip application to establish proximal and distal control of the ICA.
(3) Identifying favorable projections of paraclinoid aneurysms to be approached via EEA.