Anatomy Praba Antony Mary A and Venkatramaniah / JPBMS, 2012, 21 (04) Available online at www.jpbms.info ISSN NO- 2230 – 7885 CODEN JPBSCT ResearchJPBMS article NLM Title: J Pharm Biomed Sci. JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL SCIENCES Morphometric Study of different types of Pterion and It’s relation with middle meningeal artery in dry skulls of Tamil Nadu * A.Mary Antony Praba¹, C.Venkatramaniah². ¹Assistant Professor, Department of Anatomy, Tagore Medical College, Chennai, India. ²Assistant Professor, Department of Anatomy, Sri Lakshmi Narayana Institute of Medical Sciences, Pondy, India. Abstract: Pterion is a region in the anterior part of the floor of the temporal fossa where the greater wing of the sphenoid, the parietal, frontal and the squamous temporal bones meet and form a H shaped suture. Alternatively it is the meeting region of these 4 bones(1,2). It is an commonly used landmark to find the place of anterior division of middle meningeal artery inside. There are four different types of pterions they are the spenoparietal, frontotemporal, stellate and the epipteric varieties(3,2,4). Because the anatomical variation is been so much cared by the forensic anthropologists, neurosurgeons and the forensic pathologists, we find it necessary to study the occurrence of different types of pterion in the skulls of Tamil Nadu regions. So as to full fill the criteria the different types of pterion and it’s occurrence in relation with the middle meningeal artery is been studied. The most occurring type of pterion among tamil nadu skulls are found to be the spenoparietal variety and the frontotemporal the least. Each pterion has a little difference their association with the middle meningeal artery and is important for neurosurgeons and forensic anthropologists. Key Words : Pterion, frontozygomatic suture, meningeal. Introduction: The pterion is the weakest part of the skull and the most preventing the sphenoid and parietal bones making interesting bone meeting points in craniofacial osteology. It contact with one another. is the meeting point of four bones, the frontal, parietal, greater wing of sphenoid and the squamous temporal bone on the lateral side of the skull [3,1]. This pterion junction has been used as a common extra-cranial landmark for surgeons in microsurgeries and as an important landmark for the approach of anterior branch of middle meningeal artery, Broca’s motor speech area to the left, insula, the lateral (Sylvian) cerebral fissure, for the pathologies of optic nerve, orbit, sphenoidal ridge and for the anterior circulation aneurysm and tumours [5]. The pterion is also commonly used as an important guide for age by cranial stuture closure methodology. During the fetal period and at birth the region of pterion form large membranous areas called ("soft spots“) anterolateral fontanelles or the sphenoidal fontenelle [6,7]. It provide space the skull bones [7] to overlap while passing through the pelvis at birth . The fontanelles permit the skull to accommodate the rapid growth of the brain during infancy [6]. Complete ossification of anterolateral fontanelle normally occurs immediately after birth. Fourtypes of pterions were defined by Murphy. They are[3,1,2,8]:- The sphenoparietal type(fig.2) is defined as a sutural pattern in which the sphenoid and parietal bones are in direct contact, preventing the frontal and temporal bones making contact with one another. The frontotemporal type(fig.5) is a sutural pattern in which the frontal and temporal bones are in direct contact, 1 Journal of Pharmaceutical and Biomedical Sciences © (JPBMS), Vol. 21, Issue 21 Anatomy Praba Antony Mary A and Venkatramaniah / JPBMS, 2012, 21 (04) The stellate type(fig.4) is characterized by articulation of of pterion on both the right and left side based on the four bones (frontal, parietal, temporal and sphenoid) at a definition given by Murphy. point. Out of the 50 skull, 15 Male(Fig 10.) and 15 female(Fig 11.) skulls were selected and they are studied for the presence of different types of pterion in different gender. The epipteric type(fig.3) is defined by presence of a small sutural bone between the four bones articulating at pterion(9,10). Clinically, the pterion is relevant because the anterior division of the middle meningea artery runs beneath it, on the inner side of the skull which is quite thin at this point. The relation between the pterion point and the anterior It lies 4cm above the midpoint of the zygomatic arch and division of middle meningeal is been found by marking 3.5 behind the frontozygomatic suture. The combination of 4cm above the midpoint of the zygomatic arch and 3.5 both a vital artery in this area and the relatively thin bone behind the frontozygomatic suture by using a stainless structure has lent itself to the name "God's little joke" by steel vernier and all the results were tabulated and the some physicians. percentage of the occurrence of each type of pterion is been found. Material and Methods: 50 dry adult skulls without considering the sex is been Results: taken from the Department of anatomy, Tagore Medical The Table 1. shows the occurrence of different types of College for this study (Fig 1.). pterion on the skulls of Tamil Nadu population. The most predominating variety is the spenoparietal variety followed by the epipteric, the stellate and the least the frontotemporal. The Table 2. The same order was there with the male skulls and in female skulls the spenoparietal dominates, second came the epipteric variety followed by the stellate type and the frontotemporal was not seen within the selected range of female skulls. Table 1. Shows the percentage of different types of pterion in 50 skulls belongs to the region of Tamil Nadu Side of spenoparietal epipteric stellate frontotemporal skull Right 78% 10% 10% 2% Left 70% 18% 8% 4% The normal skulls were selected without any known Total 74% 14% 9% 3% abnormalities. All the skulls are analysed for the presence 2 Journal of Pharmaceutical and Biomedical Sciences© (JPBMS), Vol. 21, Issue 21 Anatomy Praba Antony Mary A and Venkatramaniah / JPBMS, 2012, 21 (04) Table 2. Shows the percentage of different types of pterion in 15 male and 15 female skulls belongs to the region of Tamil Nadu. Side of skull spenoparietal epipteric stellate frontotempor al Right 66.6% 6.6% 13.3% 6.6% Male Left 53.3% 26.6% 13.3% 0% Total 60% 16.6% 13.3% 3.3% Right 80% 20% 6.6% 0% Female Left 93.3% 6.6% 0% 0% 86.6% 13.3% 3.3% 0% The relation with the pterions and the anterior division of middle meningeal artery is been analysed in all the types. In sphenoparietal variety it predominately present either a few mms. above or below, or on the suture of the pterion(Fig 6 ). Discussion: In epipteric variety the point of middle meningeal artery is been inside or on the borders of the sutural bone(Fig 7). The result shows that the spenoparietal pterion is predominately present among the skulls of Tamil Nadu as like in other Indian skulls. There is considerable variation between the types of pteion and the point of the anterior division of middle meningeal artery. So the pterion types and the point the anterior division of middle meningeal artery can be used in minimum invasive keyhole surgeries with maximum access [17,18]. Conclusion: Relationship between the middle meningeal artery and the pterion is of great importance in the field of surgery, anthropology and in forensic medicine. This study is also been conducted in primate skulls that shows the same pattern as in human [19]. The relationship between the point of middle meningeal artery and the pterion is not only playing roles in approaching the anterior division of middle meningeal artery, it is also useful in approaching the Brocca’s area on the left side of brain and the lateral (Sylvian) cerebral fissure[20,9]. Acknowledgement: In frontotemporal variety the point of the middle We are so thankful to the Dean of Tagore Medical College - meningeal artery was behind the pterion(Fig.8.) and in Chennai, for provided us with the necessary facilities to stellate type it was below the pterion(Fig 9). The table conduct the study. We are also thankful to the technical shows the occurrence of different types of pterion in staff belongs to the department of Anatomy for their kind different regions of the world for comparison [11-16]. cooperation. 3 Journal of Pharmaceutical and Biomedical Sciences© (JPBMS), Vol. 21, Issue 21 Anatomy Praba Antony Mary A and Venkatramaniah / JPBMS, 2012, 21 (04) References: 1. Murphy T. The pterion in the Australian aborigine. Am J 11. Asala SA, Mbajiorgu FE. Epigenetic variation in the Phys Anthropol 1956;14:225-44. Nigerian skull: sutural pattern at the pterion. East Afr 2. Mwachaka PM, Hassanali J, Odula P. 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