Pterion

Pterion
Side view of head, showing surface relations of bones. (Pterion labeled at center.)
Side view of the skull. (Pterion visible but not labeled. Arrow points to sphenoparietal suture, and pterion is slightly to the right of the tip of arrow.)
Gray's	subject #46 182

The pterion is the point corresponding with the posterior end of the sphenoparietal suture.

Location

It is situated about 3 cm. behind, and a little above the level of the zygomatic process of the temporal bone.

It marks the junction between four bones:

• the parietal bone
• the squamous part of temporal bone
• the greater wing of sphenoid bone
• the frontal bone

Clinical significance

The pterion is known as the weakest part of the skull.

In the clinical setting, the pterion is relevant because the anterior division of the middle meningeal artery runs beneath it, on the inner side of the skull, which is quite thin at this point. The combination of both a vital artery in this area and the relatively thin bone structure has lent itself to the name "God's little joke" by some physicians.^[1]

A blow to the pterion (e.g., in boxing) may rupture the artery causing an epidural haematoma. The pterion may also be fractured indirectly. Blows to the top or back of the head may not cause fracture at the site of impact, but may place sufficient force on the skull that its weakest part, the pterion, will fracture.

Etymology

The pterion receives its name from the Greek root pteron, meaning wing.

In Greek mythology, Hermes, messenger of the gods, was enabled to fly by winged sandals, and wings on his head, which were attached at the pterion.

References

External links

• Diagram at shoshinryu.com
• SUNY Figs 22:01-04
• Diagram - look for #24 (source here)
• Pterion at eMedicine Dictionary

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 As such, some of the information contained within it may be outdated.