The Expanded Endoscopic Endonasal Approach to Anterior Communicating Artery Aneurysms: A Cadaveric Morphometric Study

Background: Aneurysms of the anterior communicating artery (ACoA) complex are of significant clinical relevance as they are the most frequent of all cerebral aneurysms. Within the past several years, the management of intracranial aneurysms has shifted from clip ligation via open craniotomies to endovascular coiling, with the latter increasingly being adopted as the preferred method of treatment whenever technically feasible. This shift has occurred because of the serious technical difficulties that surgical clipping presents. The endoscopic endonasal approach offers several benefits without the need for the brain retraction or gyrus rectus resection that is typical of traditional craniotomy approaches. In the recent years, the endoscopic endonasal approach has evolved dramatically, and it has been successfully applied to the clipping of intracranial aneurysms in several case reports.

Objective: The purpose of this study is to explore the endoscopic endonasal approach to the ACoA complex and delineate the limits of visualization and technicalities of aneurysm clip placement. We also address some of the shortcomings of this approach raised in previous anatomical studies.

Study Design: The study design is an anatomic and morphometric analysis of human cadaveric heads.

Methods: An expanded endoscopic endonasal dissection was performed on 15 latex-injected adult cadaveric heads. The anatomical boundaries of the endonasal corridor, operative field, optic chiasm, and their relationship to the ACoA complex were measured. The dimensions of the exposure of the ACoA complex, A1, and A2 segments were quantified, and the feasibility of aneurysm clip placement on each section was assessed.

Results: Exposure of the bilateral A1 and A2 segments was accomplished in all 15 cadaveric heads. The superior, inferior, and anterior aspects of the ACoA complex were exposed and accessible by operative instruments in all specimens. The average length of the exposed ACoA was 3 ± 1 mm. We were able to expose the A1 segment with an average of 5 ± 3 mm on the left, and 5 ± 1 mm on the right. We exposed the A2 segment with an average of 5 ± 2 mm on the left and right. The average distance from the alar floor to the ACoA was 95 mm, while the proximal lateral limit measured between the alar floor margins was 36 mm. The distal lateral limit as defined by the distance between the lateral most exposed margins of the chiasm was 19 mm. Clip placement was accomplished for the ACoA complex, and the A1 and A2 segments in all the specimens.

Conclusion: The endonasal endoscopic approach, specifically the transtubercular transplanum approach is a feasible and minimally disruptive alternative to treating select aneurysms of the ACoA complex. This approach avoids the traditional brain retraction, ventricular drainage, gyrectomy, and morbidity associated with a pterional, subfrontal, transcallosal, or anterior interhemispheric approach. It also avoids the complications from endovascular treatment such as coil compaction, migration, thromboembolic events, and the need for multiple treatments. We believe this approach is a feasible alternative to traditional methods, especially as expanded endoscopic endonasal techniques continue to evolve.