|Year : 2015 | Volume
| Issue : 4 | Page : 333-336
An anatomical study of pterygoalar bar and its clinical relevance
Neeru Goyal, Anjali Jain
Department of Anatomy, Christian Medical College, Ludhiana, Punjab, India
|Date of Web Publication||18-Sep-2015|
Department of Anatomy, Christian Medical College, Ludhiana, Punjab
Source of Support: Nil., Conflict of Interest: No.
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 Nov 23];2:333-6. Available from: http://www.cjhr.org/text.asp?2015/2/4/333/165744
| Introduction|| |
Certain parts of the sphenoid bone are connected by ligaments that occasionally ossify. Ossification of such normally occurring ligaments produces new structures such as bony bridges and foramina., 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. 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.,, Through this foramen pass, some of the branches of the mandibular nerve that is, nerve to masseter and deep temporal nerves.
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. Hai et al. 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.
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|| |
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|| |
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|| |
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.
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.,, 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. in Brazilian skulls and Peker et al. in Anatolian skulls. The incidence was found to be slightly higher in South Indian skulls.,, We could not find any previous studies and data from North Indian region except for a case report  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 , 14, ,, have calculated the incidence as: Number of skulls having partial or complete, unilateral or bilateral ossification/ Total number of skulls examined
- Chouke , has calculated incidence as: Number of sides showing ossification/ Total number of skulls examined
- Antonpoulou et al. 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. 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 ,,, 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. and Skrzat et al. observed the pterygoalar bar to be present medial, lateral or inferior to the foramen ovale while Kamath and Vasantha  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. However, the presence of such bony bridges in children suggests the possibility of genetic factors. 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. 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.
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[Figure 1], [Figure 2], [Figure 3]