Applied Microanatomy of the Petrous Internal Carotid Artery, Greater Superficial Petrosal Nerve, and Tensor Tympani Muscle to Improve Safety during Middle Fossa Surgery—Laboratory Cadaveric Investigation

Background: Surgery of the middle cranial fossa is risky due to the proximity of several neurovascular structures, such as the otic capsule, greater superficial petrosal nerve (GSPN), and petrous internal carotid artery (pICA). The concept of middle fossa triangles helps with the recognition of landmarks and increases the safety of middle fossa surgery. However, a detailed description of the interrelationship between pICA, tensor tympani, and GSPN applicable to middle fossa surgery is lacking.

Objective: This article aims to investigate the relationship between the GSPN, pICA, and tensor tympani to improve safety during surgery of the middle fossa.

Methods: The middle fossa of five cadaveric heads (10 sides) was drilled to expose the GSPN, pICA, and tensor tympani. The crossing points between pICA, GSPN, and tensor tympani were recorded for proximal and distal pICA using a stereotactic navigation system. Distances between the crossing points and the borders of the horizontal pICA were calculated.

Results: The GSPN and pICA crossed in all specimens. The mean distance between the GSPN and pICA was 3.0 mm proximally, and 5.3 mm distally. Tensor tympani was lateral to pICA with a mean distance of 4.2 mm in all specimens (proximally and distally) except in one specimen where it crossed only the proximal pICA ([Fig. 1]).

Fig. 1 Results of the measurements on individual specimens assessed in this study. The left column lists the caliber of the pICA (D). The measurements are shown for the posterior (proximal) and anterior (distal) ends of the pICA. The last two columns show the trajectory of TT and GSPN in relation to the pICA from posterior to anterior. Leftward and rightward arrows mean that the structure courses medially and laterally in relation to pICA from anterior to posterior, respectively. All numbers are in millimeters. GSPN, greater superficial petrosal nerve; pICA, petrous internal carotid artery; TT, tensor tympani.

Conclusion: Drilling the Kawase triangle on the medial side of the GSPN is not universally safe as the pICA and GSPN cross frequently on along the course of horizontal pICA. The tensor tympani muscle may be used as a reliable landmark to systematically localize the pICA.

 

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No conflict of interest has been declared by the author(s).

Publication History

Article published online:
07 February 2025