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 Table of Contents  
ORIGINAL ARTICLE
Year : 2014  |  Volume : 20  |  Issue : 4  |  Page : 189-190

Inca bones at asterion


1 Department of Anatomy, Bambolim, Goa, India
2 Goa Medical College, Bambolim, Goa, India

Date of Web Publication13-Dec-2014

Correspondence Address:
Prashant E Natekar
Department of Anatomy, Goa Medical College, Bambolim 403 202, Goa
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-7749.146936

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  Abstract 

Background: Surgical approach towards asterion has to be done with caution as many surgeons are unfamiliar with the anatomical variations. The asterion corresponds to the site of the posterolateral (mastoid) fontanelle of the neonatal skull which closes at the end of the first year. Inca bones provide information as markers for various diseases, and can mislead in the diagnosis of fractures. Observation and Results: 150 dry skull bones from the Department of Anatomy at Goa Medical College, India and other neighboring medical colleges by examining the asterion, and its sutural articulations with parietal, temporal and occipital bones and also anatomical variations if any in adults. Discussion: The anatomical landmarks selected must be reliable and above all easy to identify. Bony structures are more suitable than soft tissue or cartilaginous landmarks because of their rigid and reliable location. Presence of these bones provides false impressions of fractures or the fractures may be interpreted for inca bones especially in the region of asterion either radiologically or clinically which may lead to complications during burr hole surgeries.

Keywords: Asterion, Inca bone, Posterolateral fontanelle, Wormian bones


How to cite this article:
Natekar PE, Natekar SE, De Souza FM. Inca bones at asterion. Indian J Otol 2014;20:189-90

How to cite this URL:
Natekar PE, Natekar SE, De Souza FM. Inca bones at asterion. Indian J Otol [serial online] 2014 [cited 2020 Feb 22];20:189-90. Available from: http://www.indianjotol.org/text.asp?2014/20/4/189/146936


  Introduction Top


The asterion is the junction of the parietal, temporal, and occipital bones. [1] The asterion corresponds to the site of the posterolateral (mastoid) fontanelle of the neonatal skull, which closes at the end of the 1 st year. [2] 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.

Inca bones provide information as markers for various diseases, brittle bone disease osteogenesis imperfecta, [3] neurocranial variables [4],[5] and can mislead in the diagnosis of fractures. [6] This study is carried out so as to keep ourselves abreast in the diagnosis of fractures at the site of asterion its anatomical variations and also trephing of the skull during operation.


  Materials and Methods Top


This study is carried out on 150 dry skull bones from the Department of Anatomy at Goa Medical College, India and other neighboring medical colleges by examining the asterion, and its sutural articulations with parietal, temporal, and occipital bones and also anatomical variations if any in adults.


  Observation and Results Top


In this study, it was observed that 12.6% of the asterion showed presence of single inca bone as shown in [Table 1] and [Figure 1].
Figure 1: Multiple inca bones at asterion of right side

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Table 1: Percentage distribution of inca bone at asterion in different population

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In our study, it was seen that inca bones at the asterion was 12.6%, whereas in North Americans 12%, South Americans 7.5%, Egyptians 14.4%, Indians-Burma 14.7%, Indians-Punjab 16.9%, [4] Australian aborigines 19.82%, [7] Turks 9.92%, [8] and Kenyans was 20%. [9]


  Discussion Top


Asterion is an important anatomical landmark which is situated at the junction of parietal, temporal, and occipital bones. One or more inca bones may appear at the mastoid fontanelle. They vary greatly in size but 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 reveal presence of epipteric bones at pterion. [10] Studies also reveal that the wormian bones are located in the lambdoid suture and fontanelle (masto-occipital suture). The second most common occurrence (about 25%) is in the coronal suture. The rest occur in any remaining sutures and fontanelles. [11] The presence of these inca bones at asterion may also complicate surgical orientation leading to pitfalls.

Although inca bones can be found as normal variants, various etiologies have been proposed are racial feature of Native American Indian populations. This etiology illustrates the longevity of some erroneous medical theory, even when they have long been disproved. [12] Consequence of skull deformation. Incidence of wormian bones in deformed and undeformed skulls of Southwestern Indians, concluded that there is no significant difference between these two groups. [13] An adaptation to cranial enlargement. There is a relationship with the total length of sutures. Greater the sutural length of skull greater the number of wormian bones. Metabolic disorders. Formation of wormian bones could result from metabolic disorders of the mesoderm. [14] An autosomal dominant trait. Wormian bones are inherited as a dominant trait with incomplete penetrance and variable expression. [15]

Presence of these bones provides false impressions of fractures or the fractures may be interpreted for inca bones, especially in the region of 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.

In our study, 12.6% of the inca bones were seen at the asterion when compared with that of the various populations as shown in [Table 1]. This 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.

 
  References Top

1.
Williams PL, Bannister LH, Berry MM, Collins P, Dyson M, Dussek JE, et al. The skull. In: Gray's Anatomy. 38 th ed. London: Churchill Livingstone; 1995. p. 583-606.  Back to cited text no. 1
    
2.
Datta AK. The skull. In: Essentials of Human Anatomy. 5 th ed. Kolkata: Current Book International; 2009. p. 64.  Back to cited text no. 2
    
3.
Glorieux FH. Osteogenesis imperfecta. Best Pract Res Clin Rheumatol 2008;22:85-100.  Back to cited text no. 3
[PUBMED]    
4.
Carolineberry A, Berry RJ. Epigenetic variation in the human cranium. J Anat 1967;101:361-79.  Back to cited text no. 4
[PUBMED]    
5.
Nayak S, Soumya KV. Unusual sutural bones at pterion. Int J Anat Vari 2008;1:19-20.  Back to cited text no. 5
    
6.
Oon CL, Yu SF. Posterior parietal fractures in infancy and early childhood. Singapore Med J 1971;12:13-7.  Back to cited text no. 6
[PUBMED]    
7.
Kellock WL, Parsons PA. A comparison of the incidence of minor nonmetrical cranial variants in Australian aborigines with those of Melanesia and Polynesia. Am J Phys Anthropol 1970;33:235-40.  Back to cited text no. 7
[PUBMED]    
8.
Gumusburun E, Sevim A, Katkici U, Adiguzel E, Gulec CE. A study of sutural bones in Anatolian-Ottoman skulls. Int J Anthropol 1997;12:43-8.  Back to cited text no. 8
    
9.
Mwachaka PM, Hassanali J, Odula P. Sutural morphology of the pterion and asterion among adult Kenyans. Braz J Morphological Sci 2009;26:4-7.  Back to cited text no. 9
    
10.
Natekar PE, De Souza FM. Epipteric bones at pterion. An anatomical study and its surgical significance. Indian J Otol 2010;16:44-6.  Back to cited text no. 10
    
11.
Chambellan V. Etude Anatomique et Anthropologique sur les os Wormiens. Inaugural Thèse; Paris, 1883. p. 66.  Back to cited text no. 11
    
12.
Kaplan SB, Kemp SS, Oh KS. Radiographic manifestations of congenital anomalies of the skull. Radiol Clin North Am 1991;29:195-218.  Back to cited text no. 12
    
13.
El-Najjar M, Dawson GL. The effect of artificial cranial deformation on the incidence of Wormian bones in the lambdoidal suture. Am J Phys Anthropol 1977;46:155-60.  Back to cited text no. 13
[PUBMED]    
14.
Hess L. Ossicula wormiana. Hum Biol 1946;18:61-80.  Back to cited text no. 14
[PUBMED]    
15.
Torgersen J. Hereditary factors in the sutural pattern of the skull. Acta Radiol 1951;36:374-82.  Back to cited text no. 15
[PUBMED]    


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1]


This article has been cited by
1 The Surface and Intracranial Location of Asterion
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Journal of Craniofacial Surgery. 2019; 30(8): e753
[Pubmed] | [DOI]



 

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