Contralateral Nasofrontal Trephination: A Novel Corridor for a “Dual Port” Approach to the Petrous Apex

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Objective: Expanded endonasal approaches (EEAs) have proven safe and effective in treating select petrous apex (PA) pathologies. Angled endoscopes and instruments have expanded the indications of such approaches. However, the complex neurovascular anatomy surrounding the petrous region still poses a significant challenge. This study seeks to evaluate the feasibility, anatomical aspects, and limitations of a novel contralateral nasofrontal trephination (CNT) route as a complementary corridor improving access to the PA.

Methods: EEA and CNT approaches to the petrous apex were carried out bilaterally in 15 cadaveric heads with endovascular latex injections. An initial EEA was performed by removing the contralateral right middle turbinate, followed by bilateral complete spheno-ethmoidectomies. A contralateral Draf IIb was completed delineating the frontal recess. This was followed by a posterior septectomy and removal of sphenoid rostrum. The floor of the sphenoid sinus was drilled flush with the clivus which was drilled exposing posterior fossa dura. Subsequently, the nasofrontal incision was carried down to the bone exposing the suture lines demarcating the confluence between three bony processes (the glabella of the frontal bone, the frontal process of the maxilla, and the nasal bone) and a bony window was drilled. The orbit was not entered; thus, the lamina papyracea was preserved. Then, removal of the petrosal process of the sphenoid bone facilitated the visualization of the retrocarotid window to the medial aspect of the petrous apex and the bony dissection was advanced laterally towards the IAC. Inferior limit was also extended to expose the foramen lacerum, the jugular foramen and lower cranial nerves. The distance to the petrous apex, angle between instruments through the two approach portals and surgical freedom were obtained and compared.

Results: 3D DICOM based modeling and visualization indicate that a CNT portal reduces the distance to the target PA by an average of 3.33cm (19%), and affords a significantly increase in the angle between instruments (15.60 degrees; 54%). Furthermore, a vector of approach on the vertical axis that is superior by 28.97 degrees yielded a caudal reach advantage of 2 cm.

The area of surgical freedom afforded by three different approaches (endonasal, endonasal and CNT with 2 full nostrils, and endonasal and CNT with 3 quadrants of nostrils was compared at four points: dural exit point (DEP) of the 6th cranial nerve, jugular foramen, foramen lacerum, and the petroclival fissure. The mean area of surgical freedom provided by both of the approaches incorporating the CNT corridor was superior to that of the EEA at each of the surgical targets (p = <0.001).

Conclusions: The addition of a CNT portal affords an intriguing avenue for reducing the anatomical limitations of the classical EEA to the petrous apex. This study provides new insights into the anatomical nuances and potential benefits of a dual-port anterior petrosectomy, albeit, within the limitations of a cadaveric preclinical study.

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Artikel online veröffentlicht:
05. Februar 2024