Ossification of Ligaments Near the Foramen Ovale: An Anatomic Study With Potential Clinical Significance Regarding Transcutaneous Approaches to the Skull Base

Abstract

Abstract Objective: There is paucity of information regarding the specific anatomy and clinical significance of ossified ligaments near the foramen ovale (e.g., pterygospinous and pterygoalar ligaments). The present study was undertaken to define this anatomy in more detail and to review the literature regarding these anatomic variations. Methods: One hundred fifty-four adult human dry skulls were analyzed for the presence of ossified ligaments of pterygospinous (ligament of Civinini) and pterygoalar (ligament of Hyrtl). Measurements were made of these bony structures and observations made of their relationships to the inferior aspect of the foramen ovale and neighboring structures. Results: Two ossifications each (2.6%) of the ligaments of Civinini and Hyrtl were found. One of each of these (1.3%) was completely ossified, thereby resulting in 2 complete foramina (i.e., 1 foramen of Civinini and 1 foramen of Hyrtl). A significant correlation was found between the left and right sides, with either complete or incomplete ossification of these ligaments being found on left sides (75%) (incomplete Civinini on right side and all others on left side). The complete foramen of Civinini was found to have an area of 16.7 mm2, and the complete foramen of Hyrtl was found to have an area of 9.42 mm2. Conclusion: Such anomalous bony obstructions could interfere with transcutaneous needle placement into the foramen ovale or distort anatomic relationships during approaches to the cranial base.