The "Inferior" Petrolingual Ligament for Endoscopic Endonasal "Lateral" Transpetrosal Approach

Endoscopic endonasal approach to the petrous apex is feasible but presents challenges due to the obstruction posed by the internal carotid artery (ICA). Medial or inferomedial approaches, which involve ICA transposition or contralateral transmaxillary visualization, provide only limited lateral exposure of the apex. This study introduces a novel endoscopic endonasal "lateral" transpetrosal approach (EELPA) to the petrous apex.

Endoscopic endonasal transpterygoid anatomical dissections were performed bilaterally on nine formalin-fixed cadaveric heads. The study focused on the endosurgical identification of the dural layers and ligaments of the middle fossa. The extradural lateral petrosectomy through these dural layers and ligaments was assessed. A representative clinical case illustrates the findings.

A newly identified anatomical structure, termed the "inferior" petrolingual ligament (IPLL), was described. This ligament spans from the ventral middle cranial fossa to the ventrolateral aspect of the foramen lacerum, surrounding the inferior part of the lingula. It is located above the junction of the greater superficial petrosal nerve into the Vidian nerve. Transection and detachment of the IPLL provide access to the lateral extradural space of the petrous apex. Following superior and lateral petrosectomy, critical structures such as the tentorium, trigeminal nerve, superior petrosal vein, facial and vestibulocochlear nerves, and abducens nerve can be exposed.

This study introduces the IPLL as a consistent and reliable anatomical landmark for EELPA. Identifying the IPLL facilitates extradural exposure and resection of the lateral petrous apex while minimizing disruption to the ICA and cranial nerves.