Combined Endoscopic Endonasal Transpterygoid Supra- and Infrapetrosal Approach: Technical Feasibility, Anatomic Limitations, and Surgical Implications of the Supracondylar Groove for Sphenopetroclival Chondrosarcomas

Background: The endoscopic endonasal transpterygoid approach provides a unique ventral vantage between the surgeon and pertinent cranial nerves to access most skull base chondrosarcomas. Involvement of the petroclival fissure and cavernous sinus (sphenopetroclival chondrosarcoma [SPCC]) is associated with a lower extent of resection and higher rates of neurological deficits given to anatomic complexities and distortions. We detailed the limits of a single-stage combined infra- and suprapetrosal approach to SPCCs. The surgical implication of the supracondylar groove (SCG) was examined as a viable landmark for protecting the petrolacerum carotid artery and abducent nerve at transition planes in cases with condylar sparing.

Methods: The endoscopic endonasal transpterygoid approach was undertaken on seven silicon-injected cadaveric heads (14 sides). Combined transcavernous (TC), trans-quadrangular space (TQ), sublacerum transpetrosal (TP), and far-medial transjugular tubercle (TJT) approaches were utilized, and anatomic limits were identified under navigation guidance. Several relevant distances were measured and compared on both sides. A case of SPC with condylar sparing was illustrated to highlight the clinical applicability.

Results: The inferior petrosal sinus was exposed between the planned transpetrosal (TP) and far-medial trans-JT (TJT) corridors. The inferiormost point of lacerum carotid (LC) at the TP-TJT transition was exposed, and the anteroinferior petrosectomy was performed in the area bounded by the petroclival fissure medially, petrous carotid canal superolaterally, jugular tubercle inferomedially, and internal acoustic canal posteriorly. Following paraclival carotid mobilization, the lingual process laterally, Dorello’s canal superomedially, and pterygosphenoid fissure anteroinferiorly were used as the limits for anteromedial petrosectomy. The abducent nerve (VI) was then exposed at the border between the quadrangular area and the posterosuperior compartment of cavernous sinus. The VI dural entrance (viE) at the TC-TQ transition was identified proximally. The midpoint of supracondylar groove (MSCG) was located based on relevant muscular insertions and the mediolateral limit of the condyle, and perpendicular vertical (A-line) and horizontal (B-line) lines were drawn. viE was consistently lateral to A-line, with a mean viE-A-line distance of 3.52 ± 0.4 mm. The mean coronal LC-B-line distance was 12.74 ± 1.2 mm. The anteroinferior petrosectomy was then extended posterolaterally toward the first carotid genu to expose the midpoint of petrous carotid (MPC). The mean oblique MPC-MSCG distances were 18.25 ± 1.77 mm. There was no significant difference in measurements between the right and left sides. No vascular insult was observed in the patient, and abducent nerve palsy was improved.

Conclusion: The abducent nerve is not typically encountered during the medial clivectomy limited to the SCG mid-sagittal plane. Tumor removal from the cavernous sinus toward the anteromedial petrous apex and beyond should be performed cautiously within a 5 mm lateral to this plane to protect the interdural abducent nerve. Following inferolateral clivectomy, the foramen lacerum fibrocartilage should be sectioned within 1 cm above the mid-coronal plane of the SCG to protect the lacerum carotid. Additionally, anteroinferior petrosectomy toward the first carotid genu should be cautiously performed beyond 1.5 cm of mSCG to protect the petrous carotid. Applying these methods can potentially achieve safe maximal tumor removal in large SPCCs.