Pterion is the junction of the greater wing of the sphenoid,
squamous temporal, frontal, and parietal bones in the lateral wall
of the skull. Fracture of the pterion can be life-threatening
because it overlies the anterior branches of the middle meningeal
vessels, which lie in grooves on the internal aspect of the lateral
wall of the calvaria. The pterion is two fingers' breadth superior
to the zygomatic arch and a thumb's breadth posterior to the
frontal process of the zygomatic bone. A hard blow to the side of
the head may fracture the thin bones forming the pterion, producing
a rupture of the anterior branch of the middle meningeal artery
crossing the pterion. Middle meningeal artery is a branch of the
Maxillary artery; branch of the external carotid artery. As blood
is pumped against the gravity, pressure inside the external carotid
artery is high. Therefore in a fracture arteries can bleed
profusely. But the middle meningeal veins are more superficial.
According to experienced neurosurgeons veins are easily damaged due
to above reason. The resulting hematoma exerts pressure on the
underlying cerebral cortex. An untreated middle meningeal artery
hemorrhage may cause death in a few hours. Therefore it is wise to
mention that it damages to the middle meningeal vessels.