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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 7  |  Issue : 1  |  Page : 47-50

Bony outgrowths on the base of skull near foramen spinosum


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

Date of Submission08-Mar-2019
Date of Decision26-May-2019
Date of Acceptance25-Jun-2019
Date of Web Publication19-Jun-2020

Correspondence Address:
Neeru Goyal
Department of Anatomy, Christian Medical College, Ludhiana, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cjhr.cjhr_28_19

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  Abstract 


Objectives: Ossification of the various ligaments at the base of the skull is quite common. Ossified pterygospinous and pterygoalar ligaments have been extensively described in the literature. We observed some bony outgrowths extending from the bar of bone between foramen spinosum (FS) and foramen ovale (FO). The objective of the present study was to report the incidence of these bony outgrowths near the FS. Materials and Methods: Fifty-five dried adult skulls and 20 sphenoid bones were examined for the bony outgrowths (if present) near the FS. Results: Bony outgrowths extended posteriorly from the bar of bone between FO and FS in 60% of cases. These bony outgrowths when long were seen meeting the spine extending from the spine of the sphenoid, forming a complete or incomplete bar of the bone. At times, a thick bony plate joined the bar of bone between FO and FS to the spine of the sphenoid. Conclusions: The bony outgrowths near FS become clinically important in surgeries involving middle meningeal artery. In spite of such implications, these bony outgrowths are neither named nor have they received the due attention in the literature. Detailed studies of these bony outgrowths could be of interest to radiologists, anesthetists, and neurosurgeons.

Keywords: Bony outgrowths, foramen ovale, foramen spinosum, sphenoid


How to cite this article:
Goyal N, Jain A. Bony outgrowths on the base of skull near foramen spinosum. CHRISMED J Health Res 2020;7:47-50

How to cite this URL:
Goyal N, Jain A. Bony outgrowths on the base of skull near foramen spinosum. CHRISMED J Health Res [serial online] 2020 [cited 2020 Jul 16];7:47-50. Available from: http://www.cjhr.org/text.asp?2020/7/1/47/286885




  Introduction Top


Infratemporal fossa is one of the most difficult regions of the skull base to be accessed surgically.[1] There are many ligaments at the base of the skull, and ossification of these ligaments is quite common. Ossification of these ligaments becomes important due to their close relationship to the neighboring structures, specially nerves and vessels.[2] Ossification of the ligaments is considered to be an age-dependent process.[3] However, the presence of ossified ligaments in children suggests the possibility of genetic factors.[4] The sphenoid bone presents a series of intrinsic ligaments: interclinoid, caroticoclinoid, pterygospinous, and pterygoalar. Ossification of these ligaments with different clinical implications has been reported.[5]

While studying some ossified ligaments (pterygospinous and pterygoalar) of the base of the skull,[6],[7] we noticed some bony outgrowths in the region of foramen spinosum (FS). These bony outgrowths were clearly different from the ossified pterygospinous and pterygoalar ligaments. Even after extensive search in the available literature, we could not find any mention of these bony outgrowths in the vicinity of the FS.

FS is a small foramen present in the medial aspect of the greater wing of the sphenoid, posterolateral to the foramen ovale (FO). The spine of the sphenoid projects posterolateral to the FS. The foramen transmits the middle meningeal vessels and a recurrent meningeal branch of the mandibular nerve (nervus spinosus).[8] Ellwanger and Campos[9] reported a case of variation in FS due to a variation in the trajectory of the middle meningeal artery and stated that the detailed knowledge of the variations in FS and of the origin and course of the middle meningeal artery is of clinical significance in the fractures of the squamous and petrous parts of the temporal bones, as well as in surgical interventions involving the nerve of the pterygoid canal and maxillary artery. This artery, or its branches, and other large intracranial extracerebral vessels have been implicated in the pathophysiology of migraine by theories, suggesting neurogenic inflammation or cranial vasodilatation, or both, as explanations for the pain of migraine.[10] The bony outgrowths at the base of the skull in the vicinity of FS could compress these structures, leading to symptoms. In spite of these implications, the bony outgrowths in the region of FS have not received the due attention in the literature. Hence, the present study was conducted to report the incidence of these unnamed bony outgrowths near the FS.


  Materials and Methods Top


The study was conducted on 55 adult dried skulls and 20 adult dried sphenoid bones. Base of the skull and the sphenoid bones were carefully observed for the presence of bony outgrowths in the vicinity of FS. Special attention was given to the bony outgrowths extending from the bar of bone between FO and FS. These bony outgrowths were carefully differentiated from the pterygospinous bar (stretches between the spine of the sphenoid and the pterygospinous process on the posterior border of the lateral pterygoid plate [LPP]) and from the pterygoalar bar (extends from the undersurface of the greater wing of the sphenoid to the LPP).

Ethical approval

The permission was taken from Institutional Ethics Committee prior to starting the project. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.


  Results Top


Of the 75 skull bones studied, we observed the presence of bony outgrowths at the base of the skull in the vicinity of the FS in 45 (60%) cases. When present, such bony outgrowths were seen extending posteriorly from the bar of bone between FO and FS. These bony outgrowths were clearly different from the ossified pterygospinous and pterygoalar ligaments. The pterygospinous bar stretches between the spine of sphenoid and the LPP, while the pterygoalar bar extends from the under surface of the greater wing of the sphenoid to the LPP. However, these bony outgrowths extended from the bar of bone between FO and FS and were directed posteriorly, toward the spine of the sphenoid. These bony outgrowths were quite variable in length. They were as small as a small bony spicule, while some were large enough to join the spine of the sphenoid and hence forming a complete or incomplete bar of bone near the FS.

The different types of bony outgrowths observed were in the form of:

  • Small bony spines extending posteriorly from the bar of bone between FO and FS
  • Incomplete bar of bone
  • Complete bar of bone
  • A thick bony plate.


Small bony spines

Of the 75 bones studied, 33 showed the presence of small spines on the bar of bone between FO and FS [Figure 1]. In nine cases, such spines were present bilaterally. In 18 cases, the spine was present only on the one side. In rest of the six cases, a small spine was seen extending from the bar of bone between FO and FS on the one side, while on the other side, a complete or incomplete bar of bone or a wide plate-like spine of the sphenoid was observed.
Figure 1: Basal aspect of the skull showing small spine (s) extending from the area between FO and FS toward the spine of sphenoid. FO: Foramen ovale, FS: Foramen spinosum, SS: Spine of sphenoid

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Incomplete bar

In four cases, unilaterally, a spine extended posteriorly from the bar of bone between FO and FS and ran just short of the spine extending from the spine of the sphenoid, and hence, an incomplete bar of bone was formed. Of these four cases, in two cases, no spinous bony outgrowth was observed on the other side, while in one case, a small spine was seen extending from the bar of bone between FO and FS, and in another case, the spine of the sphenoid looked wide plate-like on the other side.

Complete bar

In 11 cases, a large spine extended posteriorly from the bar of bone FO and FS. This large spine joined the spine extending from the spine of the sphenoid, and a complete bar of bone was formed [Figure 2]. Of these, the complete bar was present bilaterally in four cases, while in three cases, the bar was present only on the one side and the other side did not show the presence of bony outgrowth near FS. In four cases, a complete bar was present on the one side, while a small spine was observed on the other side.
Figure 2: Basal aspect of the skull showing a complete bar of bone extending from the area between FO and FS joining the spine of sphenoid (star). FO: Foramen ovale, FS: Foramen spinosum, LPP: Lateral pterygoid plate

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Thick bony plate

In four skulls, instead of the spines, a thick bony plate joined the bar of bone between FO and FS to the spine of the sphenoid [Figure 3]. In such cases, the spine of the sphenoid looked wide plate-like instead of being a spinous process. Of these four cases, this wide plate was seen bilaterally in one case, and in another case, it was seen only on the one side while the other side did not show any variation. In one case, this wide plate was seen on the one side while the other side showed the presence of a small spine. In another case, wide plate was seen on the one side while an incomplete bar of bone was seen on the other side.
Figure 3: Basal aspect of the skull showing a thick bony plate (arrow) joining the bar of bone between FO and FS to the spine of the sphenoid. FO: Foramen ovale, FS: Foramen spinosum

Click here to view



  Discussion Top


FO and FS are important openings on the infratemporal surface of the greater wing of the sphenoid bone. Usually, a thin bar of the bone separates the FS and FO. While studying the ossified pterygospinous and pterygoalar ligaments of the base of the skull, we observed that at times, bony outgrowths extended from the bar of bone separating FO and FS and such bony outgrowths when present extend posteriorly to join the spine of the sphenoid. However, these bony outgrowths cannot be classified either as pterygospinous bar (stretches between the spine of the sphenoid and the posterior border of the LPP) or as pterygoalar bar (extends from the under surface of the greater wing of the sphenoid to the LPP). Abundant literature is available regarding the pterygospinous and pterygoalar bars and also about the bony spicules in the FO.[11],[12] However, we could not find any description of the bony outgrowths extending posteriorly from the bar of bone between FO and FS.

Khan et al.[11] and Khairnar and Bhusari[12] reported the presence of bony growths in the margin of FO but did not describe the bony outgrowths near FS. Sharma et al.[13] observed bony spicules between FO and FS in 6.66% of cases, but they did not clearly describe the location and direction of the bony spicules. In the present study, we observed spinous bony outgrowths in the region of FS in 60% of cases. Such spinous outgrowths or complete or incomplete bar of bone near the FS could compress the middle meningeal artery.

FS as a complete bony canal is peculiar to a human. Primitively, the FS was merged in the foramen lacerum. With the partial subdivision of the foramen lacerum, the middle meningeal artery tended to form its own bony canal, and in many mammals, the posterior margin of the angle of sphenoid is notched for the artery. Hence, the appearance of FS in primates shows considerable variations. In tarsiers, the initiation of an independent canal has commenced. In platyrrhines, the artery passes through the FO. In old world monkeys, a notch can be detected near the entrance of the artery. In anthropoid apes, a notch is occasionally present at the entrance of the artery. It is only in human that a complete FS is observed. However, in human also, many variations are observed, and these variations represent stages that, to some degree, fall short of its completed human form.[14]

The variations observed in the FS become more significant as they may indicate the variations in the origin or course of the middle meningeal artery. Middle meningeal artery is the largest and the most important of the arteries supplying the meninges. In addition to the two terminal frontal and parietal trunks, middle meningeal artery gives (1) tiny ganglionic branches to the trigeminal ganglion and the roots of the trigeminal nerve; (2) a petrosal branch to the greater petrosal nerve runs through the hiatus for greater petrosal nerve, gives twigs to the facial nerve and the tympanic cavity, and anastomoses with the stylomastoid artery; (3) a superior tympanic artery runs in the canal for tensor tympani and supplies the muscle and the lining membrane of the canal; (4) temporal branches pass through the minute foramina in the greater wing of the sphenoid and anastomose in the temporal fossa with the deep temporal arteries; (5) an anastomotic branch with the lacrimal artery runs forward and enters the orbit through the lateral part of the superior orbital fissure. It anastomoses with a recurrent meningeal branch of the lacrimal artery, and an enlargement of this anastomosis explains the occasional origin of the lacrimal artery from the middle meningeal artery.[8] Liu and Rhoton[15] stated that variations in the middle meningeal artery have important clinical implications for endovascular therapy of skull base lesions. This artery represents the source of bleeding in 85% of the epidural hematomas. However, in the absence of brain injury, no functional impairments are known to be associated with the suppression of the middle meningeal vascularization.[16]


  Conclusion Top


Although the variations in the shape and size of the FS have been widely studied, more attention is required toward the bony outgrowths in the vicinity of the FS. The spines we observed in the present study can be clearly differentiated from the pterygospinous and pterygoalar bony bars. The close relationship of these bony outgrowths to FS may lead to symptoms of compression of middle meningeal vessels. In spite of such implications, these spines are neither named nor have they received the due attention in the literature. Detailed studies of these bony outgrowths could be of interest to radiologists, anesthetists, and neurosurgeons.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Nayak SR, Saralaya V, Prabhu LV, Pai MM, Vadgaonkar R, D'Costa S. Pterygospinous bar and foramina in Indian skulls: Incidence and phylogenetic significance. Surg Radiol Anat 2007;29:5-7.  Back to cited text no. 1
    
2.
Erdogmus S, Pinar Y, Celik S. A cause of entrapment of the lingual nerve: Ossified pterygospinous ligament – A case report. Neuroanatomy 2009;8:43-5.  Back to cited text no. 2
    
3.
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. 3
    
4.
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. 4
    
5.
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;8:405-8.  Back to cited text no. 5
    
6.
Goyal N, Jain A. An anatomical study of pterygoalar bar and its clinical relevance. CHRISMED J Health Res 2015;2:333-6.  Back to cited text no. 6
  [Full text]  
7.
Goyal N, Jain A. An anatomical study of the pterygospinous bar and foramen of Civinini. Surg Radiol Anat 2016;38:931-6.  Back to cited text no. 7
    
8.
Standring S. External skull. In: Gray's Anatomy. 40th ed. Spain: Churchill Livingstone, Elsevier; 2008. p. 415.  Back to cited text no. 8
    
9.
Ellwanger JH, Campos Dd. Abnormality of the foramen spinosum due to a variation in the trajectory of the middle meningeal artery: A case report in human. J Neurol Surg Rep 2013;74:73-6.  Back to cited text no. 9
    
10.
Hoskin KL, Zagami AS, Goadsby PJ. Stimulation of the middle meningeal artery leads to Fos expression in the trigeminocervical nucleus: A comparative study of monkey and cat. J Anat 1999;194 (Pt 4):579-88.  Back to cited text no. 10
    
11.
Khan AA, Asari MA, Hassan A. Anatomic variants of foramen ovale and spinosum in human skull. Int J Morphol 2012;30:445-9.  Back to cited text no. 11
    
12.
Khairnar KB, Bhusari PA. An anatomical study on the foramen ovale and the foramen spinosum. J Clin Diagn Res 2013;7:427-9.  Back to cited text no. 12
    
13.
Sharma S, Thakur C, Modi BS, Singh T. Study of anatomic variant of foramen ovale and spinosum in dried human skulls. Int J Anat Res 2016;4:2002-2006.  Back to cited text no. 13
    
14.
Wood-Jones F. The non-metrical morphological characters of the skull as criteria for racial diagnosis: Part I: General discussion of the morphological characters employed in racial diagnosis. J Anat 1931;65:179-95.  Back to cited text no. 14
    
15.
Liu Q, Rhoton AL Jr. Middle meningeal origin of the ophthalmic artery. Neurosurgery 2001;49:401-6.  Back to cited text no. 15
    
16.
Bruner E, Sherkat S. The middle meningeal artery: From clinics to fossils. Childs Nerv Syst 2008;24:1289-98.  Back to cited text no. 16
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]



 

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