Pterion
Also known as: temple
An H-shaped junction on the side of the skull where the frontal, parietal, temporal (squamous part) and sphenoid (greater wing) bones meet. It is the thinnest part of the lateral skull and overlies the anterior branch of the middle meningeal artery.
Overview
The pterion lies in the temporal fossa about 4 cm above the midpoint of the zygomatic arch and about 3 cm behind the frontozygomatic suture (clinically two finger-breadths above the arch and a thumb's breadth behind the frontal process of the zygomatic bone). Its sutures — sphenofrontal, sphenoparietal and sphenosquamous — form an H, although the pattern varies (most commonly sphenoparietal, with the sphenoid meeting the parietal).
The bone here is thin and covered by temporalis. On its internal surface runs the anterior (frontal) branch of the middle meningeal artery, often in a bony groove or tunnel, so that a blow to the temple can fracture the bone and tear the vessel. It also overlies the lateral cerebral (Sylvian) fissure and the stem of the lesser wing — a key surgical landmark for the pterional (frontotemporal) craniotomy used to approach the circle of Willis.
- Location
Temporal fossa, ≈4 cm above the midpoint of the zygomatic arch.
Anatomy
- Relations
Deep: anterior branch of the middle meningeal artery and vein, lateral cerebral fissure, lesser wing of the sphenoid. Superficial: temporalis muscle and fascia, superficial temporal vessels.
Function
- Junction of four cranial bones
- Surface landmark for the middle meningeal artery, lateral sulcus and Broca area (left side)
Clinical significance
Extradural (epidural) haematoma
A temporal blow fractures the pterion and tears the middle meningeal artery. Arterial blood strips dura from bone, forming a biconvex (lentiform) collection on CT that is limited by sutures. Classic course: brief loss of consciousness, a lucid interval, then rapid deterioration with ipsilateral fixed dilated pupil (uncal herniation compressing CN III) and contralateral hemiparesis. A neurosurgical emergency.
Test yourself
A blow to the side of the head causes brief unconsciousness, a lucid interval and then rapid deterioration. CT shows a biconvex haematoma. Which bony landmark overlies the vessel most likely injured?
- Bregma
- Lambda
- Pterion
- Asterion
Answer: Pterion
The pterion — the H-shaped junction of the frontal, parietal, temporal and sphenoid bones — is the thinnest part of the lateral skull and overlies the anterior branch of the middle meningeal artery. Its rupture produces an extradural (epidural) haematoma, which is lens-shaped and limited by sutures.
Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.