IP Indian Journal of Anatomy and Surgery of Head, Neck and Brain

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IP Indian Journal of Anatomy and Surgery of Head, Neck and Brain (IJASHNB) open access, peer-reviewed quarterly journal publishing since 2015 and is published under the Khyati Education and Research Foundation (KERF), is registered as a non-profit society (under the society registration act, 1860), Government of India with the vision of various accredited vocational courses in healthcare, education, paramedical, yoga, publication, teaching and research activity, with the aim of faster and more...


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Sucharitha A, Rao, Ashwini N S, and Beez: Study of anatomical variations of pterion in Karnataka population


Introduction

Pterion is a point of irregular H-shaped sutural confluence seen in the norma lateralis of skull, formed by the frontal, parietal, temporal and sphenoid bones. Pterion corresponds to the site of the antero-lateral fontanelle of the neonatal skull, which closes in the third month after birth.1

It is also known as the sylvian point. Fronto-zygomatic suture and midpoint of zygoma can reliably be used in locating pterion. It is located 4cms above midpoint of zygomatic arch and 3.5cms behind fronto-zygomatic suture.2 Pterion receives its name from the greek word “Pteron”, meaning wing. In greek mythology, Hermes, messenger of the gods, was enabled to fly by winged sandals, and wings on his head which were attached at the pterion.

One or more sutural bones appear between the sphenoidal angle of the parietal and the greater wing of the sphenoid known as pterion ossicles or epipteric bones,2 these sutural bones may be mistaken radiologically for fracture of the skull in the pterion region.3

Pterion is an important landmark for anterior branch of middle meningeal artery, broca’s motor speech area to the left, insula, lateral cerebral fissure, for the pathologies of optic nerve, orbit, sphenoid ridge and for the anterior circulation aneurysms and tumors.4

Classification

Murphy’s classification of pterion include 4 types of pterion namely,

Types of pterion

  1. Spheno-parietal type: Greater wing of sphenoid articulates with the parietal bone to form the letter ‘H’.

  2. Frontotemporal type: Squamous part of the temporal bone articulates with the frontal bone.

  3. Stellate type: Here all bones articulate at a point in the form of letter ‘K’.

  4. Epipteric type: A sutural bone is lodged between the 4 bones forming the pterion.5

Objectives of the Study

  1. To classify the types of pterion based on Murphy’s classification and

  2. Compare the right and left sides

Materials and Methods

The present study was conducted on 100 adult human skulls collected from the department of Anatomy and Forensic Medicine at Kempegowda Institute of Medical Sciences and from other Medical and Dental colleges in and around Bengaluru.

It is an observational study. All human skulls (irrespective of sex) with intact calvaria, well defined sutures and erupted third molar teeth are considered for study. Damaged skulls, old skulls with obliterated sutures and skulls of newborn, infants and children are excluded

Skulls were observed macroscopically with the naked eye for sutural pattern. Skulls are classified based on Murphy’s classification.

Findings of sutural pattern of pterion were noted. Values were recorded separately on right and left sides and compared. Values were also compared with previous studies for their statistical significance.

Statistical analysis

The data collected in this study were analysed statistically using descriptive statistics like percentages, mean and standard deviation. The statistical analysis was done using SPSS 16.0 software. To compare between right and left sides, One-Way ANOVA (Analysis of Variance) was used.

Results

Table 1

Type of pterion

Percentage of incidence (%)

Sphenoparietal

78

Frontotemporal

02

Stellate

04

Epipteric

16

In the present study, Sphenoparietal was found to be commonest (78%). Frontotemporal was seen in 02%, Stellate type was observed in 04% and epipteric type was seen in 16% of cases. In two skulls, ‘two’ epipteric bones were noticed. The same type of pterion occurred on both right and left sides in the same individual in 75% of the cases. SP type occurred more bilaterally where as FT, stellate and epipteric types occurred more unilaterally shown in Table 1. In the present study, sphenoparietal and stellate occurred more on right side whereas frontotemporal and epipteric types occurred more on left side shown in Table 2. Two sutural bones at pterional site were noted in two skulls, one on right side and other on left side.(Figure 3)

Table 2

Unilateral and bilateral presentations

Types of Pterion

Total

Bilateral

Unilateral

SP

156

66

24

FT

04

00

04

Stellate

08

01

06

Epipteric

32

08

16

[i] Note: SP – Spheno-parietal, FT – Fronto-temporal

Table 3

Right and left presentations

Types of Pterion

Total number of unilateral type

Right

Left

SP

24

14

10

FT

04

01

03

Stellate

06

04

02

Epipteric

16

06

10

[i] SP – Sphenoparietal, FT – Frontotemporal

Figure 1

Epipteric type of pterion

https://typeset-prod-media-server.s3.amazonaws.com/article_uploads/85d84f76-2147-4830-8522-b92a892897d1/image/2862970a-1edb-4119-91bf-a48091389e93-uimage.png

Figure 2

Fronto-temporal type of pterion

https://typeset-prod-media-server.s3.amazonaws.com/article_uploads/85d84f76-2147-4830-8522-b92a892897d1/image/80c0e6da-47d5-4e48-8d1c-0a1d7f151365-uimage.png

Figure 3

Pterion with two epipteric bones

https://typeset-prod-media-server.s3.amazonaws.com/article_uploads/85d84f76-2147-4830-8522-b92a892897d1/image/41b5267d-ef84-4560-a286-1761fb3e9ddf-uimage.png

Figure 4

Stellate type of pterion

https://typeset-prod-media-server.s3.amazonaws.com/article_uploads/85d84f76-2147-4830-8522-b92a892897d1/image/a93c1dee-7f71-4fbf-82aa-08bc54f7da40-uimage.png

Figure 5

Speno-parietal type of pterion

https://typeset-prod-media-server.s3.amazonaws.com/article_uploads/85d84f76-2147-4830-8522-b92a892897d1/image/659ad8c3-a6c3-4603-a8bf-1ef8e1b6fd8c-uimage.png

Table 4

Study / Population, n (skull) and Sex

Sphenoparital type (%)

Fronto-temporal type (%)

Stellate type (%)

Epipteric type (%)

Oguzetal, 2004, Turkish, n = 26. Male.

88

10

0

02

Mwachaka P.M et al, 2009, Kenyan, n=90, Known gender.

66.7

15.5

11.1

6.7

Ankur Zalwadia et al, 2010, Western Indians, n=42, unknown gender.

91.7

2.4

1.2

4.8

Hussain Saheb et al, 2011, Indians, n=125, Known Gender

69.25

17.35

9.7

3.7

Present Study, 2011, South Indians, n=100, Unknown gender

78

02

04

16

Table 5

Percentage distribution of symmetrical and asymmetrical distribution in different studies

Study / Population

Symmetrical (%)

Asymmetrical (%)

Mwachaka P.M et al, 2009, Kenyan, n=90, Known gender.

78

22

Ankur Zalwadia et al, 2010, Western Indians, n=42, unknown gender.

99

01

Wandee C, et al, 2011, Thailand, n = 268, Known gender.

84.7

15.8

Present Study, 2011, South Indians, n=100, Unknown gender

75

25

Table 6

Study / Population

Spheno parietal

Fronto-temporal

Stellate pterion

Epipteric

Right (%)

Left (%)

Right (%)

Left (%)

Right (%)

Left (%)

Right (%)

Left (%)

Ankur Zalwadia et al, 2010, Western Indians, n=42, unknown gender.

92.9

90.5

2.4

2.4

0

2.4

4.8

4.8

Hussain Saheb et al, 2011, Indians, n=125, Known Gender.

69.25

69.25

11.3

23.4

12.1

7.3

5.2

2.2

Wandee C, et al, 2011, Thailand, n = 268, Known gender.

81.0

81.3

1.5

0.7

0

0.7

17.5

17.2

Present Study, 2011, South Indians, n=100, Unknown gender

58.33

41.67

25

75

66.67

33.33

37.5

62.5

Discussion

In the present study the occurrence of SP type was 78% which is high when compared to Hussain Saheb et al., Mwachaka P.M et al. and Oguzetal studies. The high occurrence of SP type could have an evolutionary basis. The SP type of pterion is the dominant form in humans whereas the fronto-temporal type is dominant in non-human primates. In primate evolution, the antero-superior segment of the squamous part of the temporal bone of lower primates become detached from its parent and gets incorporated into the postero-superior angle of the greater wing of the sphenoid bone of humans, thereby changing the pterion pattern from the fronto-temporal type of non-human primates to the spheno-parietal type of humans. Frontotemporal type is least commonly seen in the present study. This is similar to Ankur Zalwadia et al. study but low when compared to Oguzetal, Mwachaka P.M et al. and Hussain Saheb et al. studies. The occurrence of fronto-temporal pterion in man is considered to be atavism due to a natural reversion of a stage in the phylogenetic development of man in which the fronto-temporal type was the normal and constant.

From the present study it was seen that the same type of pterion occurs more bilaterally than unilaterally. This is in agreement with the findings among kenyans but differs with that among turks, where the occurrence of pterionic type varied significantly on the left and right sides. These differences could be due to the different sample sizes used in the study. In the present study, sphenoparietal type was the predominant type. This is in agreement with other studies.

Present study has shown that the same type of pterion occurs more bilaterally than unilaterally. This is in agreement with Wandee C et al., Mwachaka PM et al. and Ankur Zalwadia et al.

Conclusion

Spheno-parietal was the most common type observed. Bilateral presentation of this type is more common when compared to unilateral presentation. This type of pterion was present more on right side than left side. Fronto-Temporal was least commonly observed. This type was seen unilaterally only. It was seen more on left side. In Stellate type unilateral presentations were more common than bilateral presentation. This was seen more on right side. Epipteric type was the second most common type observed. This type was seen more commonly on left side. Asymmetrical presentation was more common than symmetrical presentation. The present study has shown no significant side difference for the types of pterion. Is useful for anthropologists, forensic pathologists, neurosurgeons and maxillofacial surgeons.

Source of Funding

None.

Conflict of Interest

The author declares no conflict of interest.

References

1 

PL Williams LH Bannister MM Collins P Collins M Dyson JE Dussek Gray’s AnatomyChurchill Livingstone20064128

2 

TS Ranganathan A textbook of human Anatomy5th editionS.chand & Company1946744

3 

N Satheesha KV Sowmya Unusual sutural bones at pterionInt J Anat Variation200811920

4 

MEAydin C Kopuz MT Demir U Çorumlu AH Kaya Localization of pterion in neonatal cadavers: a morphometric studySurg Radiol Anat20103265455010.1007/s00276-009-0615-7

5 

P Mwachaka J Hassanali P Odula Sutural Morphology of the pterion and asterion among adult KenyansBraz J Morphol Sci200926147



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© This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Article type

Original Article


Article page

54-58


Authors Details

Sucharitha A*, Chairtha Rao, Ashwini N S, Rameeza Beez


Article History

Received : 02-04-2021

Accepted : 19-04-2021

Available online : 09-08-2021


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