Introduction: Internal carotid artery-posterior communicating artery aneurysms (ICPCANs) are occasionally located under the anterior petroclinoid fold (tentorium). The tentorium must be resected to achieve safe and secure clipping of the ICPCAN. The surgeon performing the procedure must be careful not to damage the oculomotor nerve, which is usually located behind the aneurysm, to ensure that the patient's oculomotor function is preserved. In this article, we presented a surgical technique for the tentorium resection and oculomotor nerve mobilization during an ICPCAN clipping intervention. Additionally, the clinical features of the patients who underwent the procedure have been described.

Materials and Methods: Five patients who underwent tentorium resection for ICPCAN neck clipping were analyzed. The anterior clinoid process (ACP) was removed in three cases. When the aneurysm was under the tentorium and sufficient space to observe important structures around the aneurysm was lacking, we cut and resected the tentorium to the necessary extent and peeled the oculomotor nerve from the aneurysm. The following factors were analyzed in the five patients: age, sex, direction of the projection of the aneurysm, aneurysm size, position of the aneurysmal neck, degree of aneurysm exposure, whether an anterior clinoidectomy was performed, and presence and extent of oculomotor nerve deficit.

Results: The mean age of the patients was 68.0 years (54-83 years), and all five were female. The mean maximum aneurysm diameter was 6.6 mm (4.7-8.7 mm). The mean neck position of the aneurysms was 0.0 mm (-1.2 to 1.2 mm) superiorly, 2.8 mm (0.7-4.8) posteriorly, and 1.1 mm (-0.8 to 3.6 mm) medially from the tip of the ACP. Inconsistency in the relative position between the aneurysmal neck and ACP made it difficult to predict the need for tentorium resection before the surgery. In two cases, only the neck was exposed, without peeling the oculomotor nerve from the aneurysm, whereas the aneurysm was completely exposed in the other three cases. One of the patients who underwent neck clipping without peeling of the oculomotor nerve from the aneurysm experienced a transient worsening of oculomotor palsy. Two patients who underwent neck clipping with complete peeling of the oculomotor nerve from the aneurysm experienced transient oculomotor palsy and recovered in the 1st and 4th postoperative months, respectively.

Conclusion: We presented a surgical technique for tentorium resection and oculomotor nerve mobilization for ICPCAN clipping, as well as the clinical features of the patients who underwent the intervention. Although it is difficult to predict the need for these procedures preoperatively, the procedures are considered safe and effective for clipping aneurysms completely and preventing oculomotor nerve palsy.