Study of the Location and Morphology of the Pterion in Adult Nigerian Skulls

The pterion which marks the union of 4 bones of the cranium is located superior to the zygomatic arch and posterior to the frontozygomatic suture. It is an important neurosurgical landmark for the lateral/pterional approach and has racial differences in both its location and pattern of union of the bones. This study aims to analyze the location and types of pterion in adult Nigerian skulls. Bilateral sides of 37 adult dry skulls were studied. The pterion types were classified; linear distances from the centre of the pterion to the midpoint of the zygomatic arch and to the frontozygomatic suture were measured; these were analyzed for side and gender differences. Sphenoparietal was the most common pterion type (86.1%) followed by frontotemporal (8.3%), stellate (5.6%), and epipteric types (0%). The mean distances from the pterion to the midpoint of zygomatic arch were ？mm and ？mm in males and females, respectively, while the distances to the frontozygomatic suture were ？mm and ？mm. The vertical position of the pterion was significantly higher in males than females. Bilateral occurrence is statistically insignificant. This information will be of neurosurgical and anthropological importance. 1. Introduction The pterion is a craniometric point near the sphenoid fontanelle of the skull. It is a point of convergence of the sutures between the frontal, sphenoid, parietal, and squamous temporal bones [1]. There are varied patterns of articulation of these bones and sometimes a small epipteric bone may be present. There are four types of sutural pattern: sphenoparietal, the sphenoid and parietal bones are in direct contact; frontotemporal, the frontal and temporal bones are in direct contact; stellate, all the four bones meet at a point; and epipteric, where there is a small sutural bone uniting all the bones [2]. The pterion is located superior to the zygomatic arch and posterior to the frontozygomatic suture. This area is known as the weakest part of the skull, yet it overlies the course of the anterior division of the middle meningeal artery [1], thus making it vulnerable to rupture, leading to extradural hematoma in the event of a blunt trauma to the side of the head [3]. In addition, it acts as an important landmark for locating the Broca’s motor speech area, anterior pole of the insula, and middle cerebral artery [4]. The “pterional” or lateral approach is occasionally used in operations involving the Broca’s motor speech area [5] and repairing aneurysms of the middle cerebral artery [6]. Differences in the exact location of the pterion have been observed