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Biomedical Research

A study of sutural morphology of the pterion and asterion among human adult Indian skulls

Author(s): Hussain Saheb S , Mavishetter GF, Thomas ST, Prasanna LC, Muralidhar P, Magi

Vol. 22, No. 1 (2011-01 - 2011-03)

Hussain Saheb S , Mavishetter GF, Thomas ST, Prasanna LC, Muralidhar P, Magi

Department of Anatomy, JJM Medical College, Davangere, Karnataka, India

Abstract

The pterion and asterion are points of sutural confluence seen in the norma lateralis of the skull. Their patterns of formation exhibit population based variations. The sutural mor-phology of the pterion and asterion is important in surgical approaches to the cranial fossae. 125 human skulls of known gender (83 male, 42 female) were examined on both sides. Four types of pterion were observed – sphenoparietal 69.25%, frontotemporal 17.35%, stellate 9.7% and epipteric 3.7%. Two types of asterion were also observed – type I in 23.15% cases and type II 76.85% cases. These findings should be of use in surgical approaches and inter-ventions via the pterion and asterion.

Key words: Pterion, asterion, sutural bones
Accepted September 07 2010

Introduction

The pterion is one of the most interesting bone meeting points in craniofacial osteology and its complex morphology derives from the fact that is the contact point of the facial skeletal elements, skull base and calvarium. Knowledge of its peculiar morphology is mandatory for the pterional approach used in microsurgery and surgery[1]. The importance of the pterion is its relation to the middle meningeal artery, Broca’s motor speech area on the left side and surgical intervention relating to pathologies of the sphenoid ridge and optic canal [2]. Murphy has described four types of pterion – sphenoparietal type where the greater wing of sphenoid articulates with parietal bone to form letter H; frontotemporal type where the squamous part of temporal articulates with frontal bone; stellate type where all bones articulate in the form of letter K and epipteric type where a sutural bone is lodged between the four bones forming the pterion[3]. Presence of epiteric bone in the pterion may be a surgical pitfall [4].

The asterion is the junction of the parietal, temporal and occipital bones. The asterion is a surgical landmark to the transverse sinus location which is of great importance in the surgical approaches to the posterior cranial fossa [5]. The sutural morphology was classified into two types: Type I where a sutural bone was present and type II was where sutural bone was absent.

Material and Methods

125 dry adult human skulls of known sex (83 male and 42 female) constituted the material for the present study. The skulls belong to the Department of Anatomy, JJM Medical College, Davangere, Karnataka, India. Each was studied for the pattern of the pterion and asterion on each side and recorded.

Results

Four types of pterion were observed in the 125 skulls (250 sides) examined. Sphenoparietal type 72.3% in males, 66.2% in females and 69.25% in total; frontotemporal type 16.4% in males, 18.3% in females and 17.35 in total; stellate type 9.2% in males, 10.2% in females and 9.7% in total; epiteric type 2.1% in males, 5.3% in females and 3.7% in total (Table 1). Sphenoparietal type was observed in more cases – 69.25% on both sides: frontotemporal type was seen in 11.3% of cases on right and 23.4% on left; stellate type in 12.1% on right and 7.3% on left; epipteric type in 5.2% on right and 2.2% on left (Table 2).

Two types of asterion were observed – type I in 25% cases in males and 75% in females and type II in 21.3% in males and 78.7% in females (Table 1).

Table 1. Types of pterion and asterion in males and females.

  Type of Pterion Type of Asterion
  Sphenoparietal Frontotemporal Stellate Epipteric Type I Type II
Male n= 83 72.3% 16.4% 9.2% 2.1% 25% 75%
Female n=42 66.2% 18.3% 10.2% 5.3% 21.3% 78.7%
Total n=125 69.25% 17.35% 9.7% 3.7% 23.15% 76.85%

Table 2. Types of pterion observed on the right and left side.

Side Sphenoparietal_. Frontotemporal Stellate Epipteric
Right 69.25% 11.3% 12.1% 5.2%
Left 69.25% 23.4% 7.3% 2.2%

Table 3. Frequency of pterion types observed in different populations.

Population Number Types of pterion
SP FT St Ep
Australian aborigines (Murphy– 1956) 388 73% 7.5% 18.5% 1%
Japanese (Matsumura – 1991) 614 79.1% 2.6% 17.7% 0.6%
Indians (Saxena – 2003 ) 203 84.72% 10.01% 0% 5.17%
Turks (Ersoy -2003 ) 300 87.35% 3.47% 8.98% 0.2%
Turkish males (Oguz – 2004) 26 88% 10% 2% 0%
Kenyans (Mwachaka PM – 2009) 79 66% 15% 12% 7%
Indians (present study) 125 69.25% 17.35% 9.7% 3.7%

SP–sphenoparietal, FT–frontotemporal, St–stellate, and Ep-Epipteric.

Table 4. Types of asterion in different populations.

Population Number Type of asterion
Type I Ttpe II
North Americans (Berry – 1967) 50 12% 88%
South Americans (Berry – 1967) 53 7.5% 92.5%
Egyptians (Berry – 1967) 250 14.4% 85.6%
Indians – Burma (Berry – 1967) 51 14.7% 85.3%
Indians – Punjab (Berry – 1967) 53 16.9% 83.1%
Turks (Gumusburun – 1997) 302 9.92% 90.08%
Kenyans (Mwachaka – 2009) 79 20% 80%
Indians (present study) 125 23.15% 76.85%

Discussion

The type and location of the pterion and its relation to surrounding bony landmarks is important. Such detailed information can only readily be obtained from an examination of dry skulls. However, as imaging techniques continue to develop, it may become possible to use these to determine more precise relationships between bony landmarks and the underlying soft tissues. Since the shape and location of the sutures associated with the pterion are variable, the pterion has been classified according to its shape, with four groups being described depending on the shape of the sutures between the associated bones: sphenoparietal, frontotemporal, stellate and epipteric. An accurate knowledge of the location and relations of the pterion is important in relation to surgical intervention, particularly with respect to the course of the branches of the middle meningeal artery and Broca’s motor speech area on the left side. The distances between the pterion and the lesser wing of the sphenoid and optic canal are of practical importance in surgical approaches to these regions via the pterion. Both the type of pterion and the associated measurements variations present between different racial groups, and hence the need for accurate and up-to-date data when performing intracranial surgery guided by recognizable bony landmarks[2].

The findings of the present study are in agreement with those of previous studies (Table 3). Although the control of the pattern of articulation of bones forming the pterion and asterion is not known, genetic factors may play some role. The MSX2 gene, which encodes a home domain transcription factor, plays a crucial role in craniofacial morphogenesis by influencing fusion of sutures[6]. The high occurrence of the sphenoparietal pterion could have an evolutionary basis. Sphenoparietal variety was predominant in Indians[7]. It has been shown that the development of calvarial bones is tightly co-ordinated with the growth of the brain and requires interactions between different tissues in the sutures[8]. The present study has shown that the same type of pterion occurs more bilaterally than unilaterally.

In the present study type I asterion occurred in 23.15% of the cases. This frequency is higher than other studies (Table 4). The population with findings nearer to those of the present study is the Kenyans (20%), while the farthest is South Americans (7.5%). The mechanism of formation of sutural bones is not fully understood. Some authors suggest that these bones develop from pathological influence such as hydrocephalus [9], while others believe that sutural bones develop from normal process and are gener-ally determined.

Conclusion

Sutural morphology of the pterion and asterion in the Indian population does not differ much from that of other populations. These findings should be of use in surgical approaches and interventions via the pterion or asterion.

References

  1. Urzi F, Iannello A, Torrisi A, et al. Morphological variability of pterion in the human skulls. Ital J Anat 2003; 108 (2); 83-117.
  2. Oguz O, Gurarslan Sanli S, Bozkir MG, Soames RW. The pterion in Turkish male skulls. Surg Radiol Anat 2004: 26; 220-224.
  3. Murphy T. The pterion in Australian Aborigine. Ameri-can Journal of Physical Anthropology 1956; 14 (2): 225-244.
  4. Ersoy M., Evliyaoglu C, Bozkurt M, et al. Epipteric bones in the pterion may be a surgical pitfall. Mini-mally Invasive Neurosurgery 2003:46 (6); 363-365.
  5. Martinez F, Laxaque A, Vida L, Prinzo H, Sqarbi N, Soria VR, Bianchi C. Topographic anatomy of the aste-rion. Neurocirugia (astur) 2005 Oct; 16 (5); 441-446.
  6. Liu Y, Tang Z, Kundu, et al. Msx2 gene dosage influ-ences the number of proliferative oesteogenic cells in growth centres of the developing murine skull: a possi-ble mechanism for MSX2-mediated craniosynostosis in humans. Dev Bio 1999; 205; 260-274.
  7. Bilodi Arun kumar S, Gupta SC, Saxena RC. Pterion formation its variations in Indo-Nepalese skulls. J Nepalgunj Medical College 2002; 2;1-3.
  8. Kim HJ, Rice DP, Kettunen PJ, et al. Shh-mediated sig-nalling pathways in the regulation of cranial suture morphogenesis and calvarial bone development. De-velopment, 1998; 125 (7): 1241-1251.
  9. Hess L, Ossicula wormiana. Human Biology 1946; 18: 61-80.

Correspondence to:
Hussain Saheb S

Assistant professor
Department of Anatomy
JJM Medical College, Davangere
Karnataka 577004, India

Biomedical Research 2011, 22 (1): 73-75

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