Comparison of Location and Morphological of Pterion in Indian and Malaysian Skulls

 

Anas Bin Rosli

Saveetha Dental College, Chennai

 

ABSTRACT:

Pterion is a part of the skull which unites 4 cranium bones. It is situated posterior to the frontozygomatic suture and superior to the zygomatic arch. It is also an important cranial landmark which marks racial differences in its location and morphology. There are 4 types of pterion, sphenoparietal, frontotemporal, stellate and epipteric sutural pattern. In this research, dry skulls of both Indian and Malaysian are studied for the location and morphological of pterion, to be compared.

 

 

 

INTRODUCTION:

Pterion is defined as an H-shaped small circular area formed by the junction of four bones: frontal, parietal, temporal and sphenoid on norma lateralis of the skull being approximately 4.0 cm above the zygomatic arch and 3.5 cm behind frontozygomatic arch[1]. It also forms the floor of temporal fossa. This pterion junction has been used as a common extracranial landmark for surgeons in microsurgical and surgical approaches towards important pathologies of this region. However this point is an important landmark for anterior branch of middle meningeal artery, the most commonly related structure to extradural haemorrhage[2]. The pterion is also commonly used in cranial structure closure methodology as an important guide for age[3]. The sphenoparietal type is defined as a sutural pattern in which the sphenoid and parietal bones are in direct contact[4]. Conversely, the frontotemporal type is a sutural pattern in which the frontal and temporal bones are in direct contact[4]. The stellate type is characterized by articulation of four bones (frontal, parietal, temporal and sphenoid) at a point[4]. The epipteric type is defined by presence of a small sutural bone between the parietal bone and the greater wing of the sphenoid bone[4].

 

MATERIALS AND METHODS:

Twenty-five dry skulls of south Indian is collected from Department of Anatomy, Saveetha Dental College and another twenty-five from Hospital Universiti Kebangsaan Malaysia (HUKM). Broken skulls are excluded from the collected dry skulls. The skulls are from various races, especially the one from Malaysia because it is a multiracial country of Malays, Indians, Chinese, Kadazans, Ibans, Orang Asli, Bajaus, Sulus, Lundayehs and Baba dan Nyonya.The skulls are then overviewed once again to double check the condition of pterion, frontozygomatic suture and zygomatic arch.

 

The measurements and morphological of pterion are done in the following steps. First, collected Indian dry skulls of good condition is taken one by one to be measured. Then, the type of pterion is determined and data is recorded. Next, the measurement is taken from point of pterion to midpoint of frontozygomatic suture and to zygomatic arch, bilaterally by using a manual vernier callipers. After that, mean and standard deviation are calculated. Record data and repeat the first three steps by using Malaysian dry skulls.

 

RESULT:

The types of pterion in skulls distributions are presented in the Figure 1.

 

Figure 1 showing graph of type of pterion distribution

 

Figure 1 shows the graph of pterion distribution in Indian skulls. It shows that 68% are sphenoparietal, 12% frontotemporal, 16% stellate and 4% epipteric sutures. Meanwhile, the recorded data of Malaysian skulls show 60% are sphenoparietal, 12% frontotemporal, 12% stellate and 16% epipteric sutures types of pterion.

 

1. Sphenoparietal sutural pattern

2. Epipteric sutural pattern

3. Frontotemporal sutural pattern

4. Stellate sutural pattern

Figure 2 showing images of type of pterion

 

 

Figure 4 shows only good conditioned skulls are chosen to be measured the pterions

 

The measurements taken are recorded for the mean and standard deviation calculation.

 

Table of mean and standard deviation of both skulls are presented in Table 1. It compares the distance of the pterion from the midpoint of zygomatic arch (MPZ) and the frontozygomatic suture (FZS).

 

Table 1 shows the measurement of pterion to midpoint of zygomatic arch (MPZ) and to frontozygomatic suture (FZS) on both sides

Measurements	Sides	Indians (mm)	Malaysians (mm)
From pterion to MPZ	Right	40.87±0.515	37.09±0.721
	Left	39.31±0.962	36.51±0.186
From pterion to FZS	Right	31.93±0.976	30.81±418
	Left	32.16±0.156	31.65±0.189

 

The study shows a statistically significantly higher pterion in the Indian skulls when compared with the Malaysians. It also shows slightly little difference on the either side.

 

DISCUSSION:

The anatomic location of the pterion therefore is important in surgical interventions like extradural haemorrhagies as well as tumors involving inferior aspects of the frontal lobe, such as olfactory meningiomas. The middle meningeal artery may be torn in temporal fractures or trauma, resulting in separation of the dura mater from the bone leading to extradural hemorrhage[2]. The pterion is used as a surface landmark for the anterior branch of the middle meningeal artery and for the Sylvian[2]. The ‘pterional approach’ could be used during the operations of the Broca’s motor speech area and during repairing aneurysms of the middle cerebral artery[4]. A similar approach is also could be used, to treat aneurysms of the middle meningeal artery[5]. The types of pterions are derived from rhesus of various monkeys. The sphenoparietal sutural type is the most common in humans and orangutans. Meanwhile, the frontotemporal sutural pattern si common in chimpanzees, Japanese and babboons as well as macaques. Some questions arise regarding what factors influence the alteration of genes related to the sutural patterns.A limitation of the current study is that only maternal relationships were known for the animals studied. Nonetheless, familial aggregation of the less common variants was observed, suggesting a genetic effect on suture pattern variation at the pterion. Parts of the Cayo Santiago collections have blood samples besides bones, collected during annual physical examinations. Those materials are available for genetic studies. Starting from families of interest, it is possible to begin singling out the genes behind the variation at the pterion.

 

CONCLUSION:

Relationship between the middle meningeal artery and the pterion is of great importance in the field of surgery, anthropology and in forensic medicine. The pterional approach has been the most popular method for neurosurgeries. It is the standard approach for most lesions of anterior and middle cranial fossa like in surgical treatment of anterior circulation, tumours involving inferior aspect of frontal lobesuch as olfactory meningiomas, tumours in orbital, retroorbital , sellar and chiasmatic areas and operations on Broca’s motor speech area. The present study has shown that sphenoparietal variety is the commonest type of pterion observed in Indian skulls. Knowledge of morphological variants especially the epipteric becomes important when a burr hole placed over the anterior junction of bones may cause inadvertent penetration into orbit. A thorough knowledge of distance of various bony landmarks help in location of pterion. The data obtained will be useful for the clinicians during surgical planning and serves for success in the presence of variable topographic cranial anatomy.

 

 

 

 

REFERENCES:

1.       Zalawadia, D., et al., Morphometric study of pterion In dry skull of Gujarat Region. Njirm, 2010. 1(4): p. 25-29.

2.       Praba¹, A.M.A. and C. Venkatramaniah, Morphometric Study of different types of Pterion and It’s relation with middle meningeal artery in dry skulls of Tamil Nadu. Journal of Pharmaceutical and Biomedical Sciences©(JPBMS), 2012. 21(21).

3.       Saxena, S., S. Jain, and D. Chowdhary, A comparative study of pterion formation and its variations in the skulls of Nigerians and Indians. Anthropologischer Anzeiger, 1988: p. 75-82.

4.       Apinhasmit, W., et al., Anatomical consideration of pterion and its related references in Thai dry skulls for pterional surgical approach. Journal of the Medical Association of Thailand= Chotmaihet thangphaet, 2011. 94(2): p. 205-214.

5.       Lee, U.Y., et al., Morphological analysis of the pterion in Korean. Korean Journal of Physical Anthropology, 2001. 14(4): p. 281-289.

 

 

Accepted on 24.10.2016        © RJPT All right reserved

Research J. Pharm. and Tech 2018; 11(8): 3638-3640.