Morphometric Study of Jugular Foramen and Jugular Fossa of Dried Adult Human Skull Amudha et al.THIEME

160 Original Article

Morphometric Study of Jugular Foramen and Jugular Fossa of Dried Adult Human Skulls and Its Clinical SignificanceGovindarajan Amudha1 Chandrasekaran Nandhini Aishwarya1 Deborah Joy Hepzibah1 Vaujapuri Anandhavadivel Kesavan1 Anaimalai Kandavadivelu Manicka Vasuki1

Address for correspondence A.K. Manicka Vasuki, MD (Anat), Department of Anatomy, PSG Institute of Medical Sciences & Research, Coimbatore 641004, Tamil Nadu, India (e-mail: vasukikalyan01@gmail.com).

Introduction Jugular foramen is one of the most fascinating foramina of the human skull. It is a complex, irregular bony canal located between the occipital bone and petrous part of the temporal bone. Many important structures, like 9th, 10th, 11th cranial nerves, meningeal branch of occipital and ascending pharyngeal arteries, inter-nal jugular vein, and inferior petrosal sinus, are passing through it. The jugular fossa has a septum and a dome. The septum divides the foramen into two compartments: anteromedial compartment (pars nervosa) and posterolateral compartment (pars vas-cularis). The dome contains superior bulb of internal jugular vein. The architecture of the foramen varies in size, shape, and laterality besides differences related to sex and race. The morphometric measurements of jugular foramen are very important for neu-rosurgeries and head and neck surgeries.Objectives The aim of the present study is to study the morphology of jugular fora-men along with its dimensions, compartments, presence of partial or complete septa and dome.Materials and Methods A total number of 60 jugular foramina were examined from 30 adult dry human skulls of unknown age and sex from the Department of Anatomy, PSG Institute of Medical Sciences and Research, Coimbatore. Measurements were taken using Digital Vernier calipers. Results were analyzed statistically.Results The length, width, and surface area of jugular foramen of right side were measured and compared with the left side. Length and width of the jugular foramen was significantly higher on the right side. The presence of partial septum was found in 27 skulls (90%) on the right side and 29 skulls (99.7%) on the left side, respectively. Dome was present in 100% of the jugular foramina on the right side and 90% of the jugular foramina on the left side. Separate opening for inferior petrosal sinus was found in eight skulls (27%) on the right side and four skulls (13%) on the left side.Conclusion This study provides a clear understanding of anatomy of jugular foramen and supports the reported morphometric variations. The morphometric variations of jugular foramen in the parameters of the skull are probably due to ethnic and racial factors. Knowledge of these variations is important for neurosurgeons and radiologists who deal with space occupying lesions of the structures surrounding jugular foramen. This study may be helpful for ENT surgeons while performing middle ear surgeries.

Abstract

Keywords ► jugular foramen ► internal jugular vein ► dome ► septum ► cranial nerves

DOI https://doi.org/ 10.1055/s-0039-3401071 ISSN 2277-4025.

©2019 Society of Clinical Anatomists

Natl J Clin Anat 2019;8:160–164

1Department of Anatomy, PSG Institute of Medical Sciences & Research, Coimbatore, Tamil Nadu, India

Published online: 2019-12-31

161 Morphometric Study of Jugular Foramen and Jugular Fossa of Dried Adult Human Skull Amudha et al.

National Journal of Clinical Anatomy Vol. 8 No. 4/2019

IntroductionThe jugular foramen (JF) is a bony canal in the floor of the posterior cranial fossa, posterolateral to carotid canal located between the petrous part of the temporal bone and the occip-ital bones at the posterior end of the petro-occipital fissure, above and lateral to the foramen magnum. The upper bor-der of the foramen contains an intrajugular process, which divides the foramen into a small anteromedial compartment (pars nervosa), the petrosal part which transmits inferior petrosal sinus accompanied by a meningeal branch of occip-ital artery and posterolateral compartment (pars vascularis), the sigmoid part transmits sigmoid sinus as internal jugular vein. Glossopharyngeal nerve, vagus nerve, spinal part of the accessory nerve course between petrosal part and sigmoid part lie medial to the intrajugular process.1

Versalius2 referred JF as posterior foramen lacerum and studied variations in shape and compartmentalization.

The dome represents jugular bulb. There may be a dural septum which separates the glossopharyngeal nerve from vagus nerve and spinal part of the accessory nerve.3

Intracranial and extracranial lesions may affect the JF in addition to the intrinsic abnormalities. Pathological condi-tions affecting the JF include intracranial meningiomas, para-gangliomas, schwannoma, metastatic lesions, and infiltrative inflammatory lesions from the surrounding structures such as middle ear.4

Surgical resection is the treatment of choice in majority of these cases. Advances in microsurgical techniques made it possible to remove advanced JF lesions, which were once assumed as inoperable.5

As neurosurgeons become bolder in approaching this region, knowledge regarding anatomy of this region becomes important. Knowledge regarding the anatomy of JF will help surgeons to avoid internal jugular vein while doing ligation during radical neck dissection, the risk of venous infarction.6

As per previous studies, JF is larger on the right side compared with left and its size, height, and volume vary in different racial groups and sexes. The foramen’s com-plex shape, its formation by two bones, and the numerous nerves and venous channels that pass through it further make its anatomy very important.7,8

The present study was performed to analyze the dimensions, compartments, presence of partial or com-plete septa, dome and bony spicules of JF in view of the

surgical importance of JF which was previously considered as unapproachable.

Materials and MethodsA total of sixty jugular foramina were examined from 30 dry human skulls of unknown age, sex from the Department of Anatomy, PSG Institute of Medical Sciences and Research, Coimbatore. The length (lateromedial diameter—from sum-mit of dome to inferior border of the jugular fossa), breadth (anteroposterior diameter), and depth of the JF of both sides were measured using digital Vernier calipers with a preci-sion of 0.1 mm. Presence of septa whether partial or com-plete was noted. Presence of dome and spicules was noted. Results were analyzed statistically.

ResultsThe mean lengths of JF on the right and left sides were 16.5 mm (13–19 mm) and 1.54 mm (13–18 mm), respectively, while their mean widths measured 9.03 mm (6–12 mm) and 8.01 mm (7–11 mm) on the right and left sides, respectively. The mean area on the right side was 148.9 mm2 and on the left side was 123.2 mm2 (►Table 1). There was a highly sig-nificant correlation between the lengths on both sides and significant correlation between the widths and areas on both the sides. There were significant differences between the length and width on each side.

Partition of JF by the presence of septum was found in all the skulls. It was partial septum and was found in 27 (90%) on the right side and 29 (97%) on the left side (►Fig.  1), whereas the presence of complete septum was found in three (10%) on the right side and one (3%) on the left side (►Fig. 2; ►Table 2).

A dome indicating the presence of jugular bulb was pres-ent in 100% on the right side and 90% on the left side, whereas it was present bilaterally in 90% of the skulls and was absent in 10% on the left side of skulls (►Table 3).

Separate openings for inferior petrosal sinus were found in eight (27%) skulls on the right side and four (13%) skulls on the left side, respectively (►Fig. 3).

Bony spicules were found in six (20%) skulls on the right side and two (7%) skulls on the left side, respectively (►Fig. 4).

Table 1 Comparison of dimensions of jugular foramina of two sides (all measurements are in millimeter)

Right length (mm)

Left length (mm)

Right width (mm)

Left width (mm)

Right area (mm2)

Left area (mm2)

Mean 16.5 15.4 9.03 8.01 148.9 123.2

Standard deviation 5.15 4.65 4.43 4.58 39.8 34.1

Minimum 13 13 6 6 78 78

Maximum 19 18 12 11 228 198

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Morphometric Study of Jugular Foramen and Jugular Fossa of Dried Adult Human Skull Amudha et al.

Fig. 1 Partial septum on both the sides of jugular foramen.

Fig. 2 Complete septum with dome on the right side of jugular foramen.

Table 2 Comparison of septum of jugular foramen

Side Complete-right side

Complete-left side

Partial-right side

Partial-left side

Number 3 1 27 29

% 10 3 90 97

Table 3 Comparison of dome of jugular foramina

Side Bilateral Right side

Left side

Absent-right side

Absent-left side

Number 27 30 27 0 3

% 90 100 90 0 10

DiscussionThe shape and size of the JF is related to the size of internal jug-ular vein and the presence or absence of its superior bulb. Previ-ous studies performed by many authors stated that the superior

sagittal sinus drains into the right transverse sinus, thus right foramen is expected to be larger than the left foramen. But vari-ations in the anatomy of intracranial venous sinuses will lead to variations in size and shape of the JF.

The developmental difference in the size of the right and left jugular veins, which could be detected at 23-mm stage of embryo (8 weeks postconception), might result in difference in the developmental pattern of right and left brachiocephalic veins.9 This may be the explanation for the larger diameter of right JF as compared with left JF. Many authors have reported the same in their studies (►Table 4).

With the previous studies, area (►Table  5), septum (►Table 6), jugular fossa (►Table 7), separate opening for the inferior petrosal sinus (►Table  8), and bony spicules (►Table 9) of JF were compared and tabulated.

The JF, because of its location, is difficult to access surgi-cally. The difficulties in exposing this foramen are caused by

Fig. 3 Separate opening for inferior petrosal sinus on the right side of jugular foramen.

163 Morphometric Study of Jugular Foramen and Jugular Fossa of Dried Adult Human Skull Amudha et al.

National Journal of Clinical Anatomy Vol. 8 No. 4/2019

Fig. 4 Bony spicules on the right side of jugular foramen.

Table 4 Comparison of size of jugular foramen with previous authors

Serial number

Author’s study Larger on the right side (in percentage)

Larger on the left side (in percentage)

Equal on both the sides (in percentage)

1. Khanday et al10 70 24 6

2. Sturrock11 68.6 23.1 8.3

3. Hatiboğlu and Anil12 61.6 26 12.4

4. Patel and Singel13 60.4 15.4 24.2

5. Hussain Saheb et al14 64.8 24.8 10.4

6. Vijisha et al15 76.6 10 6.6

7. Present study 55 35 20

Table 5 Comparison of area of jugular foramen with previous authors

Serial number

Author’s study More area on the right side (in percentage)

More area on the left side (in percentage)

Equal area on both the sides (in percentage)

1. Khanday et al10 70 24 6

2. Hatiboğlu and Anil12 61.6 78 37

3. Patel and Singel13 60.4 15.4 24.2

4. Hussain Saheb et al14 64.8 24.8 10.4

5. Present study 68 30 2

Table 6 Comparison of septum of jugular foramen with previous authors

Serial number

Author’s study Complete septum on the right side (in percentage)

Complete septum on the left side (in percentage)

Partial septum on the right side (in percentage)

Partial septum on the left side (in percentage)

1. Khanday et al10 – – 24 7

2. Sturrock11 3.2 3.2 1.3 10.9

3. Hatiboğlu and Anil12 5.6 4.3 2.6 19.6

4. Patel and Singel13 23 17.6 49.5 –

5. Hussain Saheb et al14 20.3 16.8 45.6 58.4

6. Vijisha et al15 10 6.7 63.3 70

7. Present study 10 3 90 97

the structures surrounding it, such as, carotid artery ante-riorly, facial nerve laterally, hypoglossal nerve medially, and vertebral artery inferiorly.10

ConclusionIn the present study, we found many variations in the mor-phology and morphometric measurements of JF and fossa which support reported morphometric variations. These variations are important for neurosurgeons to understand the clinical presentations and progression of lesions involv-ing JF and also to interpret the images of JF. These parame-ters play an important role in planning possible approaches and also in performing surgeries related to JF. This is also useful for ENT surgeons to avoid unwanted complications while performing middle ear surgeries. These variations may be useful for radiologists and anthropologists to interpret abnormalities in various jugular foramina. These variations reported may possibly be due to constitutional, racial, and genetic factors.

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Conflict of InterestNone declared.

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Table 7 Comparison of jugular fossa (dome) of jugular foramen with previous authors

Serial number

Author’s study Dome on the right side (in percentage)

Dome on the left side (in percentage)

Dome on both the sides (in percentage)

Absent dome on both the sides (in percentage)

1. Sturrock11 30.1 6.4 53.9 9.6

2. Hatiboğlu and Anil12 36 4.7 49 10.3

3. Patel and Singel13 38.5 14.3 21 25.3

4. Vijisha et al15 26.6 33.3 70 20

5. Present study 100 90 90 10

Table 8 Comparison of separate opening for inferior petrosal sinus with previous authors

Serial number

Author’s study Separate opening for inferior petrosal sinus(in percentage)

1. Khanday et al10 8.6 on the right side and 9.8 on the left side

2. Rhoton et al16 6

3. Dichero et al17 6

4. Partridge18 25

5. Present study 27 on the right side and 13.5 on the left side

Table 9 Comparison of bony spicules (bridge) of jugular fora-men with previous authors

Serial number

Author’s study Bony spicules (in percentage)

1. Khanday et al10 75

2. Rhoton et al16 26

3. Ekinci and Unur19 20

4. Present study 27