|Year : 2011 | Volume
| Issue : 2 | Page : 83-85
Pterion: An anatomical variation and surgical landmark
Prashant E Natekar, Fatima M DeSouza, Suhit P Natekar
Department of Anatomy, Goa Medical College, Bambolim, Goa, India
|Date of Web Publication||20-Dec-2011|
Prashant E Natekar
Department of Anatomy, Goa Medical College, Bambolim, Goa-403202
Source of Support: None, Conflict of Interest: None
Introduction : The frontal and the parietal bones superiorly and the greater wing of the sphenoid and the squamous temporal inferiorly of one side meet at an H-shaped sutural junction termed the pterion. This is an important anatomical and anthropological landmark as it overlies both the anterior branch of middle meningeal artery and the lateral fissure of the cerebral hemisphere. The knowledge of sutural joints between frontal, parietal, sphenoid and temporal bones at pterion is clinically, radiologically and surgically important during surgical interventions involving burr hole surgeries. Materials and Methods : Study performed on 150 dry temporal bones. The pterion, and its sutural articulations with frontal, parietal, sphenoid and temporal bones and also anatomical variations, if any, were studied. Results : Four types of pterion, i.e. sphenoparietal, frontotemporal, stellate and epipteric, were observed. Conclusions : The knowledge of the variations of pterion and its surgical anatomy, in Indian population are important for surgeons operating in the fieldThe present study will also contribute additional information of skull bone fractures in infancy and early childhood, which may be associated with large intersutural bones giving false appearance of fracture radiologically and also during surgical interventions involving burr hole surgeries, as their extensions may lead to continuation of fracture lines.
Keywords: Epipteric bones, Pterion, Pterion ossicle, Pterion types
|How to cite this article:|
Natekar PE, DeSouza FM, Natekar SP. Pterion: An anatomical variation and surgical landmark. Indian J Otol 2011;17:83-5
| Introduction|| |
The pterion corresponds to the site of the anterolateral fontanelle of the neonatal skull which closes at third month after birth.  The joints of the cranial vault are sutural joints which ossify in membranes. As the bones are growing, the unossified sutural membranes intervene between their apposed margins. These sutural membranes connect the periosteum covering the outer and inner surfaces of the bone, which helps in growth as well as binding the bones together at their apposed margins.
A study reveals that there are four types of pteria: sphenoparietal, frontotemporal, stellate and epipteric.  Epipteric (wormian) bones are small, irregular ossicles formed due to additional ossification centers in or near the lambdoid suture, pterion and asterion. These wormian bones are also called ossa wormiana, intersutural bones or Inca bones. Studies reveal that the wormian bones are markers for various diseases and are important in the primary diagnosis of brittle bone disease (osteogenesis imperfecta)  neurocranial variables , which can be misleading in the diagnosis of fractures.  The present study was carried out to keep ourselves abreast with the diagnosis of fractures at the site of pterion, its anatomical variations and also trephing of the skull during operation.
| Materials and Methods|| |
The present study was carried out on 150 dry skull bones from the Department of Anatomy at Goa Medical College and other neighboring medical colleges in India by examining the pterion, and its sutural articulations with frontal, parietal, sphenoid and temporal bones and also anatomical variations, if any, in adults.
| Results|| |
In the present study, four types of pterion, i.e. sphenoparietal, frontotemporal, stellate and epipteric, were observed, as shown in [Table 1]. When the data were compared among different populations, the percentage of types of pterion was found to be as given in [Table 1].
|Table 1: Percentage distribution of types of pterion in different populations|
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| Discussion|| |
Pterion is an important anatomical landmark which is situated 4 cm above the midpoint of the zygomatic arch and 1 inch behind the frontozygomatic suture. One or more pterion ossicles or epipteric bones may appear between the sphenoidal angle, parietal and the greater wing of the sphenoid. They vary greatly in size, but are more or less symmetrical. Sutural bones appear in great numbers in hydrocephalic skulls and they have been linked with rapid cranial expansion. Our earlier studies also reveal the presence of epipteric bones at pterion.  The presence of these wormian bones at pterion may also complicate surgical orientation, leading to pitfalls.
The wormian bones can also cause weakness of the cranium and help in extension of the fractures according to their location. Hence, presence of these bones provides false impressions of fractures or the fractures may be interpreted for wormian bones, especially in the region of pterion or asterion, either radiologically or clinically which may lead to complications during burr hole surgeries. Although their occurrence is less frequent, their presence may serve as a marker for the identification of various anomalies of the central nervous system, dysmorphic features and syndromes. It is, therefore, relevant to surgeons and radiologists to have this essential information before and during surgical intervention. The frequencies of types of pterion have also been observed in different populations such as Australian aborigines,  Turkish males,  Japanese,  and Matsuyama Kenyans.  The present study reveals the percentage of sphenoparietal type of pterion 85.33% [Table 1],[Figure 1], frontotemporal 8% [Table 1],[Figure 2], stellate 10.6% [Table 1],[Figure 3], and epipteric 51.4% [Table 1],[Figure 4].
The present study will also contribute additional information of skull bone fractures in infancy and early childhood, which may be associated with large intersutural bones giving false appearance of fracture radiologically and also during surgical interventions involving burr hole surgeries, as their extensions may lead to continuation of fracture lines.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]