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ORIGINAL ARTICLE
Year : 2015  |  Volume : 2  |  Issue : 4  |  Page : 333-336

An anatomical study of pterygoalar bar and its clinical relevance


Department of Anatomy, Christian Medical College, Ludhiana, Punjab, India

Date of Web Publication18-Sep-2015

Correspondence Address:
Neeru Goyal
Department of Anatomy, Christian Medical College, Ludhiana, Punjab
India
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Source of Support: Nil., Conflict of Interest: No.


DOI: 10.4103/2348-3334.165744

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  Abstract 

Objectives: Pterygoalar ligament extends from the root of lateral pterygoid plate to the under surface of greater wing of sphenoid. The ligament may ossify partly or completely leading to the formation of bony bar. Complete or incomplete pterygoalar bar may act as an obstacle for approaching retro-and para-paharyngeal spaces for various surgical procedures. Methods: A total of 55 dried adult skulls and 20 sphenoid bones were observed for the presence of complete or incomplete ossification of the pterygoalar ligament. Results: Totally, 17 bones (22.67%) showed partial ossification of the pterygoalar ligament. Complete ossification was not observed in any of the cases. Bilateral incomplete pterygoalar bar was seen in six skulls. Unilateral incomplete pterygoalar bar was seen in 11 cases (5 left and 6 right sides). Conclusions: Knowledge of complete or partial ossification of the various ligaments in the region is important for anesthetists, surgeons and dentists. Being closely related to foramen ovale, such ossified bars of bone may cause entrapment neuropathy of mandibular nerve and its branches.

Keywords: Neuralgia, ossification, pterygoalar ligament, sphenoid


How to cite this article:
Goyal N, Jain A. An anatomical study of pterygoalar bar and its clinical relevance. CHRISMED J Health Res 2015;2:333-6

How to cite this URL:
Goyal N, Jain A. An anatomical study of pterygoalar bar and its clinical relevance. CHRISMED J Health Res [serial online] 2015 [cited 2019 Aug 25];2:333-6. Available from: http://www.cjhr.org/text.asp?2015/2/4/333/165744


  Introduction Top


Certain parts of the sphenoid bone are connected by ligaments that occasionally ossify.[1] Ossification of such normally occurring ligaments produces new structures such as bony bridges and foramina.[2],[3] One such ligament is pterygoalar ligament (Hyrtl's ligament) which wasfirst described by Hyrtl in 1862. It extends from the under surface of the greater wing of the sphenoid to the lateral pterygoid plate.[3] The ligament is sometimes ossified and forms the pterygoalar bar. The ossification of this ligament can be complete or incomplete. Complete ossification of the ligament leads to the formation of pterygoalar foramen or porus crotaphytico-buccinatorius.[4],[5],[6] Through this foramen pass, some of the branches of the mandibular nerve that is, nerve to masseter and deep temporal nerves.[7]

Infratemporal fossa is one of the usual positions of mandibular nerve compression and ossified pterygoalar ligament, because of its close proximity to foramen ovale and is one of the anatomical landmarks responsible for such compression.[8] Hai et al.[9] stated that in 80% cases of trigeminal neuralgia, entrapment neuropathy or microvascular compression is responsible for the symptoms. Since the pterygoalar ligament is located close to the foramen ovale, its complete or incomplete ossification may obliterate the foramen ovale that may cause mandibular neuralgia. The pterygoalar bar may also alter the normal course of the mandibular nerve or its branches and hence may cause serious implications in surgical interventions of the region and may also lead to false neurological differential diagnosis.[10]

A good knowledge of incidence of pterygoalar bar is important for surgeons, anesthetists, and dentists. So, the present study was conducted to observe the incidence of pterygoalar bar in human dried skulls and sphenoid bones.


  Materials and Methods Top


The study was conducted on 55 adult dried skulls and 20 adult dried sphenoid bones. Presence and absence of the pterygoalar bar and foramen were observed. When present, its relationship with foramen ovale was observed.


  Results Top


Of the 55 adult dried skulls and 20 sphenoid bones studied, 17 bones (22.67%) showed partial ossification of the pterygoalar ligament. Complete ossification was not observed in any of the cases.

  • Bilateral incomplete pterygoalar bar was seen in 6 skulls
  • Unilateral incomplete pterygoalar bar was seen in 11 cases (5 left and 6 right sides).


In most of the cases (73.91%), small spine was extending from the infratemporal surface of the greater wing of sphenoid [Figure 1]. In 4 cases (2 skulls on right side and in one skull bilaterally), a long spine extended from the greater wing of sphenoid and was just short of joining the lateral pterygoid plate [Figure 2]. In 2 cases (both on right side), a wide spine extended from the greater wing of sphenoid [Figure 3].
Figure 1: Inferior aspect of skull (right side) showing a small spine (Arrow) extending from the greater wing of sphenoid. LPP- Lateral pterygoid plate, FO- Foramen ovale, FS- Foramen spinosum

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Figure 2: Basal aspect of skull (left side) showing a long spine (Arrow) extending from the greater wing of sphenoid. The spine is just short of joining the lateral pterygoid plate (LPP). This partial pterygoalar bar is passing lateral to foramen ovale

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Figure 3: Inferior aspect of skull (left side) showing a wide spine (S) extending from the greater wing of sphenoid. The spine is almost covering the foramen ovale (FO) from lateral side. LPP- Lateral pterygoid plate, FS- Foramen spinosum, FL- Foramen lacerum

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Relationship with foramen ovale

In 14 cases, foramen ovale was present medial to the pterygoalar bar; while in 7 cases, the bar was passing just below the foramen ovale. Only in 2 cases, foramen ovale was present lateral to the pterygoalar bar.


  Discussion Top


The fascia that separates the medial and lateral pterygoid muscles is thickened at its cranial attachments and resultant fibrous bands are known as pterygospinous and pterygoalar ligaments. Pterygospinous ligament extends from the posterior free margin of the lateral pterygoid plate to the spine of the sphenoid. Relation of the posterior attachment of the two bars to the foramen spinosum serves to distinguish between the bars. The pterygospinous bar is always medial, and pterygoalar bar is always lateral to foramen spinosum. Pterygoalar bar is clinically important because of its more lateral position. It may prevent or cause more difficulty in horizontal or lateral approaches for mandibular nerve injections. Ossified stylohyoid ligament should not be confused with pterygoalar bar as ossified stylohyoid ligament is attached more medially and posteriorly.[11]

Although the presence of pterygoalar bar and foramen has many clinical implications, neither the pterygoalar ligament nor the bar or foramen has been mentioned in standard textbooks of Anatomy.[1],[12],[13] On studying the available literature on pterygospinous and pterygoalar bars, it was observed that the pterygoalar bar is more frequently observed and being present lateral to the foramen ovale it is clinically more significant.

The variable incidence of pterygoalar bar has been reported in different races [Table 1]. The incidence observed in the present study is comparable to the findings of Suazo et al.[14] in Brazilian skulls and Peker et al.[15] in Anatolian skulls. The incidence was found to be slightly higher in South Indian skulls.[10],[16],[17] We could not find any previous studies and data from North Indian region except for a case report [6] which described a very interesting finding of double pterygoalar foramen.
Table 1: The incidence (% age) of pterygoalar bar in various populations

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Different workers have calculated the incidence in different ways:

  • Most authors [4], 14, [17],[18],[19] have calculated the incidence as: Number of skulls having partial or complete, unilateral or bilateral ossification/ Total number of skulls examined
  • Chouke [5],[20] has calculated incidence as: Number of sides showing ossification/ Total number of skulls examined
  • Antonpoulou et al.[21] have calculated incidence as: Number of sides showing ossification/ Total number of sides examined. We have followed the methodology used by the majority.


Rosa et al.[4] described the cases with complete ossification on one side and incomplete on the other as "mixed variety." We did not observe any case of complete ossification in our study.

Previous studies [7],[17],[18],[20] have reported the presence of pterygoalar bar more frequently on left side but no explanation for this is given in literature. We did not observe any such difference in the pterygoalar bar as in the present study; of 11 cases of unilateral pterygoalar bar, 5 were present on left side while 6 were on right side.

Rosa et al.[4] and Skrzat et al.[3] observed the pterygoalar bar to be present medial, lateral or inferior to the foramen ovale while Kamath and Vasantha [17] did not find the bar passing lateral to foramen ovale in any of their cases. In the present study, the bar was mostly seen lateral or inferior to the foramen ovale except for two cases where the bar was present medial to the foramen.

Osseous bridging in various parts of the body is a frequent age-dependent process and represents the outcome of secondary ossification of fibrous structures.[22] However, the presence of such bony bridges in children suggests the possibility of genetic factors.[8] The presence of obliterated pterygoalar bar may obliterate the space between the lateral pterygoid plate and spine of sphenoid (pterygospinous gate) and the narrowness of this gate may restrict the access to retropharyngeal and parapharyngeal space by surgeons.[23] Therefore, these bony bars should be identified radiologically prior to the procedure.

In the present study, we observed partial ossification of the pterygoalar ligament in 22.67% cases. Most (91.30%) of these ossified elements were present either lateral or just below the foramen ovale. Hence, knowledge of such ossified ligaments is important for physicians, anesthetists, dentists and oral and maxillofacial surgeons[26].

 
  References Top

1.
Standring S. Neck. In: Gray's Anatomy. 40th ed. Edinburgh: Elsevier, Churchill Livingstone; 2008. p. 530.  Back to cited text no. 1
    
2.
Srisopark SS. Ossification of some normal ligaments of the human skull which produce new structures: The pterygospinous and pterygoalar bars and foramina, and the caroticoclinoid foramen. J Dent Assoc Thai 1974;24:213-24.  Back to cited text no. 2
    
3.
Skrzat J, Walocha J, Srodek R, Nizankowska A. An atypical position of the foramen ovale. Folia Morphol (Warsz) 2006;65:396-9.  Back to cited text no. 3
    
4.
Rosa RR, Faig-Leite H, Faig-Leite FS, Moraes LC, Moraes ME, Filho EM. Radiographic study of ossification of the pterygospinous and pterygoalar ligaments by the Hirtz axial technique. Acta Odontol Latinoam 2010;23:63-7.  Back to cited text no. 4
    
5.
Chouke KS. On the incidence of the foramen of Civinini and the porus crotaphitico-buccinatorius in American whites and Negroes; observations on 2745 additional skulls. Am J Phys Anthropol 1947;5:79-86.  Back to cited text no. 5
    
6.
Patnaik VV, Singla RK, Bala S. Bilateral pterygoalar bar and porus crotaphitico buccinatorius – A case report. J Anat Soc India 2001;50:161-2.  Back to cited text no. 6
    
7.
Tubbs RS, May WR Jr, Apaydin N, Shoja MM, Shokouhi G, Loukas M, et al. Ossification of ligaments near the foramen ovale: An anatomic study with potential clinical significance regarding transcutaneous approaches to the skull base. Neurosurgery 2009;65:60-4.  Back to cited text no. 7
    
8.
Piagkou MN, Demesticha T, Piagkos G, Androutsos G, Skandalakis P. Mandibular nerve entrapment in the infratemporal fossa. Surg Radiol Anat 2011;33:291-9.  Back to cited text no. 8
    
9.
Hai J, Li ST, Pan QG. Treatment of atypical trigeminal neuralgia with microvascular decompression. Neurol India 2006;54:53-6.  Back to cited text no. 9
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10.
Chakravarthi KK, Venumadhav N, Gandrakota R. Abnormal bone outgrowths and osseous structures around the foramen ovale may lead to mandibular compression or entrapment neuropathy. Int J Bioassays 2013;2:922-5.  Back to cited text no. 10
    
11.
Newton TH, Potts DG. Radiology of the Skull and Brain. St. Louis: Mosby; 1971. p. 309-10.  Back to cited text no. 11
    
12.
Rose C, Gaddum-Rosse P. Hollinshead's Textbook of Anatomy. 5th ed. Philadelphia: Lippincott-Raven Publishers; 1997. p. 737-8.  Back to cited text no. 12
    
13.
Harrison RJ. The individual bones of the cranium. In: Romanes GJ, editor. Cunniingham's Textbook of Anatomy. 12th ed. Oxford: Oxford University Press; 1981. p. 143-5.  Back to cited text no. 13
    
14.
Suazo GI, Zavando MD, Smith RL. Anatomical study of pterygospinous and pterygoalar bony bridges and foramens in dried crania and its clinical relevance. Int J Morphol 2010;28:405-8.  Back to cited text no. 14
    
15.
Peker T, Karaköse M, Anil A, Turgut HB, Gülekon N. The incidence of basal sphenoid bony bridges in dried crania and cadavers: Their anthropological and clinical relevance. Eur J Morphol 2002;40:171-80.  Back to cited text no. 15
    
16.
Chakravarthi KK, Babu KS. An anatomical study of pterygoalar bar and porus crotaphitico buccinatorius. Int J Med Health Sci 2012;1:3-9.  Back to cited text no. 16
    
17.
Kamath BK, Vasantha K. Anatomical study of pterygospinous and pterygoalar bar in human skulls with their phylogeny and clinical significance. J Clin Diagn Res 2014;8:AC10-3.  Back to cited text no. 17
    
18.
Kapur E, Dilberovic F, Redzepagic S, Berhamovic E. Variation in the lateral plate of the pterygoid process and the lateral subzygomatic approach to the mandibular nerve. Med Arh 2000;54:133-7.  Back to cited text no. 18
    
19.
Jansirani DD, Mugunthan N, Anbalagan J, Rao S, Shivadeep S. A study on ossified pterygospinpous and pterygoalar ligaments in Indian skulls. Natl J Basic Med Sci 2012;3:103-8.  Back to cited text no. 19
    
20.
Chouke KS. On the incidence of the foramen of Civinini and the porus crotaphiticobuccinatorius in American whites and Negroes; observations on 1544 skulls. Am J Phys Anthropol 1946;4:203-26.  Back to cited text no. 20
    
21.
Antonopoulou M, Piagou M, Anagnostopoulou S. An anatomical study of the pterygospinous and pterygoalar bars and foramina – Their clinical relevance. J Craniomaxillofac Surg 2008;36:104-8.  Back to cited text no. 21
    
22.
Natsis K, Piagkou M, Skotsimara G, Totlis T, Apostolidis S, Panagiotopoulos NA, et al. The ossified pterygoalar ligament: An anatomical study with pathological and surgical implications. J Craniomaxillofac Surg 2014;42:e266-70.  Back to cited text no. 22
    
23.
von Lüdinghausen M, Kageyama I, Miura M, Alkhatib M. Morphological peculiarities of the deep infratemporal fossa in advanced age. Surg Radiol Anat 2006;28:284-92.  Back to cited text no. 23
    
24.
Pinar Y, Arsu G, Aktanlkiz ZA, Bilge O. Pterygospinous and pterygoalar bridges. Sendrom 2004;16:66-9.  Back to cited text no. 24
    
25.
Rossi AC, Freire AR, Manoel C, Prado FB, Botaci PR, Caria PH. Incidence of the ossified pterygoalar ligament in Brazilian human skulls and its clinical implications. J Morphol Sci 2011;28:69-71.  Back to cited text no. 25
    
26.
Daimi SR, Siddiqui AU, Gill SS. Analysis of foramen ovale with special emphasis on pterygoalar bar and pterygoalar foramen. Folia Morphol (Warsz) 2011;70:149-53.  Back to cited text no. 26
    


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  [Figure 1], [Figure 2], [Figure 3]
 
 
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