Caroticoclinoid foramen

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The caroticoclinoid foramen is a bony variant in the sphenoid bone.

Historical

Alexander Monro (primus) is probably the first researcher to describe the caroticoclinoid foramen in his 1726 published work "The anatomy of the humane bones"[^1]. Monro referred to this bony structure as “a bony Cross-bridge under which the Carotide Arteries pass“ [^3]. According to Zdilla[^1], this structure is also found in the works of Carl Ernst Bock ("Handbuch der Anatomie des Menschen" from 1849) and Joseph Hyrtl ("Lehrbuch der Anatomie des Menschen, mit Rücksicht auf physiologische Begründung und praktische Anwendung: Histologie, Knochen-, Bänder- und Muskellehre" from 1850). Such a foramen was described as caroticoclinoid foramen by Jacob Henle or as foramen caroticum by Ferdinand Hochstetter[^2].

Anatomy

Between the anterior clinoid process and posterior clinoid process, an individual process, the middle clinoid process can be present. This middle clinoid process can then fuse with the anterior clinoid process via a ligament[^4], creating a distinct opening, a caroticoclinoid foramen. As a result, the incisura carotica located medially to the anterior clinoid process is transformed into an entirely bony delimited opening[^5].

Normal Values

The transverse diameter of the caroticoclinoid foramen is approximately 6.7 mm on the right side and 6.31 mm on the left side. The vertical diameter of the caroticoclinoid foramen is approximately 6.33 mm on the right side and 6.17 mm on the left side[^4].

Illustration

Processus clinoideus medius
Anatomical illustration of the processus clinoideus medius (#2 in the figure) and the foramen caroticoclinoideus (#3 in the figure). Illustration adapted from Platzer, Werner, and Thomas Shiozawa-Bayer. Pocket Atlas of Anatomy Volume 1: Musculoskeletal System. Thieme, 2018.