Endoscopic Endonasal Aneurysm Clip Ligation: An Anatomical Feasibility Study

Introduction: The goal of making aneurysm surgery less invasive has led to the successful development and implementation of endovascular therapy. Another method for avoiding craniotomy would be an endonasal endoscopic transsphenoidal approach. Although scattered cases have been reported in the literature, the indications and anatomic constraints involved in choosing patients for such surgery are unknown. We present the first anatomical study to evaluate the feasibility of an endoscopic endonasal approach for placement of aneurysm clips in a variety of aneurysm locations and orientations.

Methods: 2D HD and 3D HD endoscopy were used in 10 human cadaveric head specimens for dissection and clip ligation with Aesculap titanium clips. Measurements of trajectories were completed using a navigation system to calculate craniectomy size, corridor space, and ability to gain proximal and distal control of vessels for both the vertebrobasilar and anterior circulation.

Results: Application of aneurysm clips was feasible for the ophthalmic artery, proximal A2 segment of the anterior cerebral artery, anterior communicating (ACOM) artery complex, paraclinoid, and parasellar and paraclival ICAs, as well as to the proximal branches of the vertebrobasilar system and basilar tip. Proximal and distal control with good visualization of the perforators during clip application was most favorable at the ACOM artery complex. Anterior-superiorly projecting ACOM aneurysms were most ideal for this approach. Downward or anterior projecting aneurysms at this location should not be attempted due to the difficulty of visualizing the aneurysm neck and the projection of the aneurysm dome toward the dural opening. The median sizes of craniectomy for the anterior communicating artery complex and basilar tip were 4.07 cm² and 5.23 cm², respectively. Mean angles of surgical corridors to the ACOM artery complex and basilar tip were 11.6 and 13.4 degrees, respectively. Although clip placement was feasible to the basilar artery and its branches, perforating branches behind the aneurysm dome can be difficult to visualize.

Conclusion: In this cadaveric study, we determined that the most feasible aneurysms for the endonasal endoscopic approach are ACOM and basilar tip aneurysms. Although the ophthalmic artery segment, proximal AICA and PICA, vertebrobasilar junction, and proximal A2 anterior artery segments can also be exposed, difficulty with visualization of the tips of the aneurysm clips and perforators make this approach less applicable in the clinical setting. Initial endoscopic endonasal clip ligation in patients should be preferentially performed in a hybrid angiography operative room with endovascular control for patient safety.