Anatomic and Computed Tomographic Analysis of the Petrous Portion of the Internal Carotid Artery: Landmarks for an Endoscopic Endonasal Approach

Objectives: While there are many benefits to the endoscopic endonasal approach to the infratemporal fossa, involvement of the petrous portion of the internal carotid artery (ICA) poses a unique challenge. The endoscopic endonasal approach requires establishing the relationship of the petrous ICA to anatomical landmarks that can guide the surgeon in an endoscopic approach to this region. This study evaluates the relationship of the petrous ICA to specific anatomic landmarks, both radiographically and through cadaveric dissections.

Study Design: Cadaveric and radiographic study.

Methods: An endoscopic endonasal approach was used to access the petrous carotid and infratemporal fossa. Dissections involved exposure of the petrous portion of the carotid artery and identification of the foramen rotundum, ovale, and spinosum. These anatomical landmarks were then evaluated in relationship to the petrous carotid and compared with radiographic evaluation of the same measures.

Results: The endoscopic endonasal approach to the infratemporal fossa with exposure of the petrous ICA afforded complete visualization of the entire segment of this portion of the ICA with limited anatomical obstruction. The foramen rotundum, ovale, and spinosum were successfully identified and dissected with preservation of their neuro/vascular contents. CT analysis calculated a mean distance to the petrous ICA of 16.34-mm from foramen rotundum, 4.88-mm from ovale, and 5.11-mm from spinosum in males. For females, the values were 16.40-mm from rotundum and 4.36-mm each from ovale and spinosum.

Conclusion: An endonasal endoscopic approach to the infratemporal fossa with exposure of the petrous ICA is feasible. The anatomical landmarks of the foramen rotundum, spinosum and ovale can serve as both radiographic and surgical landmarks in this approach.