Extended Endoscopic Endonasal Clipping of Intracranial Aneurysms: An Anatomical Feasibility Study

 

Background: Clipping of intracranial aneurysms of the anterior and posterior circulation that are located in the midline region represents a technical challenge owing to their deep location. The posterior circulation aneurysms are more challenging because of their rarity, large size, and close proximity to the brain stem, cranial nerves, and thalamic and brain stem perforators. Transcranial clip ligation of these aneurysms has many disadvantages including retraction to the brain and other neural structures, poor visualization, limited exposure, and limited maneuverability of surgical instruments. Recently, endoscopic endonasal approaches has been effectively used to treat midline skull base lesions. Studies in the literature concerning the application of these approaches for clip ligation of intracranial aneurysms are scarce. Their indications and limitation are not established yet.

Objective: The purpose of this detailed anatomical study is to assess the feasibility and to identify the limitations of endoscopic endonasal clip ligation of intracranial aneurysms and to describe the locations and characteristics of aneurysms that are candidate for endoscopic endonasal clipping, thus, outlining the indications of these approaches.

Methods: Fifteen fresh Latex injected cadaver heads are dissected in our skull base laboratory with the use of 0- and 45-degree rigid endoscopes (Karl Storz, Tuttlingen, Germany), and a neuronavigation device as well. We used an aneurysm simulator model with different sizes to imitate the situation in the real surgery. This is the first anatomical study, to the best of our knowledge, to be conducted with the use of an aneurysm simulator to assess the feasibility of endoscopic endonasal clip ligation. Anterior Circulation is approached via Transplanum/transtuberculum approach. Posterior circulation is approached via transclival approach. The key measured parameters to assess the feasibility are the exposure of vessels and their respective perforators, the ability to gain proximal and distal control, and the possibility of clip placement according to the size, direction, and location of the aneurysm. The maneuverability of the instruments while placing the clip and the need for pituitary transposition are also assessed.

Preliminary Results: endoscopic endonasal approaches are feasible for clipping of intracranial aneurysms only in very few selected cases. In general, clip ligation of small and medium-sized aneurysms is more achievable. Aneurysms in the anterior circulation which are more suitable for this approach include anterior communicating artery aneurysms which are directed superiorly, inferiorly, or ventrally, anterior cerebral artery aneurysms originating from distal A1 and proximal A2 segments if directed ventrally and medially. Regarding the posterior circulation, Basilar apex aneurysms, medially directed posterior communicating artery aneurysms are suitable for endoscopic endonasal clip ligation, however, pituitary transposition is required for optimum exposure. Aneurysms arising from the proximal segment of anteroinferior cerebellar artery, proximal segment of posteroinferior cerebellar artery, and intradural segment of vertebral artery are also suitable for this approach.