Foramen spinosum

Bone: Foramen spinosum of Sphenoid
Sphenoid bone. Upper surface. (foramen spinosum labeled left, second from bottom.)
Base of the skull. Upper surface. (Sphenoid is yellow, and foramen spinosum is at bottom right of sphenoid.)
Gray's	subject #35 150

The foramen spinosum is one of several foramina located in the base of the skull, on the sphenoid bone, situated lateral to the foramen ovale, in a posterior angle.

Contents

It permits the passage of certain arteries, veins and/or other structures:

• the parietal trunk of the middle meningeal artery
• a recurrent branch, the nervus spinosus, from the mandibular nerve (the mandibular nerve is the third branch (V₃) of the trigeminal nerve)
• the posterior trunk of the middle meningeal vein

Morphology and morphometry

The foramen may be absent (in approx. 2% of the cases), in which case the middle meningeal artery enters the cranial cavity through the foramen ovale.^[1]

The foramen spinosum and ovale may be continuous, and the foramen spinosum may be duplicated. Wood-Jones (1931) found the foramen spinosum to be more or less incomplete in approx. 44% of the cases. The foramen spinosum was small or altogether absent in 0.4% of Lindblom's (1936) cases. This is especially true when the middle meningeal artery arises from the ophthalmic artery (the foramen would be near to empty in that case). In rare cases, early division of the middle meningeal artery into a posterior and anterior division may result in a duplication of the foramen spinosum.^[1]

In the newborn, the foramen spinosum is about 2.25 mm and in the adults about 2.56 mm in length. The width of the foramen extends from 1.05 mm to about 2.1 mm in the adults.^[2] The average diameter of the foramen spinosum is 2.63 mm in the adult.^[3]

The earliest perfect ring-shaped formation of the foramen spinosum was observed in the 8th month after birth and the latest in 7 years after birth in a developmental study on the foramen rotundum, foramen ovale and foramen spinosum. The majority of the foramen in the skulls studies was round in shape.^[3] Ginsberg et al. (see reference below) observed asymmetry of size in 16% of their patients.

In a study under 123 CT studies, Ginsberg, Pruett, Chen and Elster did not find an inverse relationship between the size of the foramen spinosum and that of the foramen ovale (for instance, a smaller foramen spinosum did not correlate with the size of the foramen ovale).^[4]

References

1. ^ ^{a b} "Illustrated Encyclopedia of Human Anatomic Variation: Opus V: Skeletal Systems: Cranium - Sphenoid Bone". Illustrated Encyclopedia of Human Anatomic Variation. http://www.anatomyatlases.org/AnatomicVariants/SkeletalSystem/Text/SphenoidBone.shtml. Retrieved on 2006-04-10. 
2. ^ Lang J, Maier R, Schafhauser O (1984). "Postnatal enlargement of the foramina rotundum, ovale et spinosum and their topographical changes". Anatomischer Anzeiger 156 (5): 351–87. PMID 6486466. 
3. ^ ^{a b} Yanagi S (1987). "Developmental studies on the foramen rotundum, foramen ovale and foramen spinosum of the human sphenoid bone". The Hokkaido Journal of Medical Science 62 (3): 485–96. PMID 3610040. 
4. ^ Ginsberg LE, Pruett SW, Chen MY, Elster AD (February 1994). "Skull-base foramina of the middle cranial fossa: reassessment of normal variation with high-resolution CT". Americal Journal of Neuroradiology 15 (2): 283–91. PMID 8192074. 

See also

• Foramina of skull

Additional images

Horizontal section of nasal and orbital cavities.

External links

• SUNY Labs 22:os-0902 - "Osteology of the Skull: Internal Surface of Skull"
• SUNY Figs 27:02-03 - "Schematic view of key landmarks of the infratemporal fossa."
• Foramen+spinosum at eMedicine Dictionary
• Roche Lexicon - illustrated navigator, at Elsevier 34257.000-1
• Anatomy of the Skull - 27. Foramen spinosum

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated.