Bilateral tripartite dural septation of the jugular foramen

Joastin Naidoo; Carmen Olivia Rennie; Lelika Lazarus

doi:10.4103/JASI.JASI_123_19

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CASE REPORT

Year : 2022 | Volume : 71 | Issue : 3 | Page : 245-247

Bilateral tripartite dural septation of the jugular foramen

Joastin Naidoo, Carmen Olivia Rennie, Lelika Lazarus
Discipline of Clinical Anatomy, School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal

Date of Submission	04-Sep-2019
Date of Decision	10-Mar-2021
Date of Acceptance	24-Nov-2021
Date of Web Publication	20-Sep-2022

Correspondence Address:
Prof. Lelika Lazarus
Discipline of Clinical Anatomy, School of Laboratory Medicine and Medical Sciences, College of Health Sciences, University of KwaZulu-Natal, Natal Westville Campus, Private Bag X54001, Durban 4000

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JASI.JASI_123_19

Abstract

We present a case of bilateral tripartite dural septation on the internal aspect of the jugular foramen (JF) in a 71-year-old White South African male. Dura mater at the intracranial aspect of the JF forms the neurovascular compartment, which houses the cranial nerves (viz. glossopharyngeal (9^th), vagus (10^th), and accessory (11^th) cranial nerves), as well as the jugular vein. In the present case, a dural septation was seen between the 9^th and 10^th cranial nerves and between the 10^th and 11^th cranial nerves; therefore, the 9^th cranial nerve traversed the anterior compartment, the 10^th cranial nerve traversed the intermediate compartment, and the 11^th cranial nerve traversed the posterior compartment. Clinical implications of this variation of the JF arise due to the occurrence of glomus jugulare tumors, as well as other pathologies such as meningiomas and neuroinomas, and these tumors occur in the region in which the neurovasculature exits the cranium. The tumors then lead to compression of these structures within the foramen. Since two dural septa at the intracranial aperture of the JF are reported bilaterally, the rootlets of the cranial nerves were more tethered within the JF. This has surgical implications as substantial tethering of these rootlets requires additional dissection during surgery, thereby increasing the risk of iatrogenic injury to the cranial nerves. It has also been reported that compartmentalization of the JF accentuates the clinical presentation of the glomus jugulare tumor. Thus, a knowledge of variations within the JF becomes imperative to ENT and neurosurgeons.

Keywords: Cranial nerves, dural septation, glomus jugulare tumor, jugular foramen, Vernet's syndrome

How to cite this article:
Naidoo J, Rennie CO, Lazarus L. Bilateral tripartite dural septation of the jugular foramen. J Anat Soc India 2022;71:245-7

How to cite this URL:
Naidoo J, Rennie CO, Lazarus L. Bilateral tripartite dural septation of the jugular foramen. J Anat Soc India [serial online] 2022 [cited 2023 Mar 28];71:245-7. Available from: https://www.jasi.org.in/text.asp?2022/71/3/245/356487

Introduction

Foramina are anatomically considered openings which transmit various structures such as nerves, arteries, and veins.^[1] The jugular foramen (JF) has been considered the most complex cranial foramen and the foramen with the most difficult surgical access; this is due to the location of the foramen which lies as a canal between the petrous part of the temporal bone and the occipital bone.^[2],[3] Various neurovascular structures traverse the JF including the glossopharyngeal, vagus, and accessory cranial nerves.^[4],[5] Therefore, due to the location of the JF and the cranial nerves passing through, among other structures such as the internal jugular vein and inferior petrosal sinus, safe surgical access to the foramen is encumbered.^[2]

Tubbs et al. highlighted the paucity of the literature with respect to detailed anatomical studies defining the dural septations of the intracranial aspect of the JF and thus aimed to “fill the gap” in the literature. Tubbs et al. also stated that the dura mater at the inner aperture of the JF formed compartments housing neurovasculature; the study conducted by Tubbs et al. then classified the dural septations of the JF on the premise that these dural relationships are of interest in the surgical treatment of meningiomas associated with the JF, as well as providing additional knowledge to assist the neurosurgeon in manipulating the nerves as they enter the JF.

Clinically, a thorough knowledge of the anatomy of the JF and the variations thereof become relevant when dealing with cases such as glomus jugulare tumors, as well as other pathologies such as meningiomas and neurinomas, since careful preoperative investigations and planning are important due to the complexity of the JF.^[3],[6],[7]

Case Report

A case of bilateral tripartite dural septation on the internal aspect of the JF in a 71-year old White South African male is found during dissection in an anatomy laboratory. Each cranial nerve is seen to be passing through its own compartment. A dural septation was seen between the glossopharyngeal and vagus nerves and between the vagus and accessory nerves; therefore, the glossopharyngeal nerve traversed the anterior compartment, the vagus nerve traversed the intermediate compartment, and the accessory nerve traversed the posterior compartment. The anteroposterior diameter of the right JF was 9.87 mm, and the mediolateral diameter was 4.54 mm; the anteroposterior diameter of the left JF was 9.39 mm and the mediolateral diameter was 3.28 mm.

Discussion

The JF has been an area that has attracted the attention of radiologists, ear, nose, and throat (ENT) surgeons, and neurosurgeons since safe surgical access to the JF is hindered by the contents of the foramen and local surrounding structures.^[2],[7] Dura mater at the intracranial aspect of the JF forms a distinct compartment for the venous structures and cranial nerves that traverse the foramen.^[3] These dural relationships are of potential interest with respect to surgical treatment of lesions associated with the JF, such as paragangliomas.^[3]

Dural septations divide the intracranial JF into three compartments; dura overlying the intrajugular compartment has two perforations, one of which is the glossopharyngeal meatus and the other being the vagal meatus.^[2] The glossopharyngeal nerve passes through glossopharyngeal meatus, whereas the vagus and accessory nerves pass through the vagal meatus; these are separated by a dural septum which provides a clear separation of the glossopharyngeal and vagus nerves as they enter the JF.^[2] Sethi et al. stated that the compartmentalization of the foramen could be the reason for compression on the structures traversing the foramen, which presents as various symptoms that are grouped together as the JF syndrome, also known as Vernet's syndrome.

Findings of the study conducted by Tubbs et al. indicated four types of dural septation of the JF. A single septation present between the glossopharyngeal nerve (anteriorly) and the vagus and accessory nerves (posteriorly) was considered Type 1, no septations present was considered Type 2, a single septation present between the glossopharyngeal and vagus nerves (anteriorly) and the accessory nerve (posteriorly) was considered Type 3, and multiple septations (ranging from three to seven septa) was considered Type 4.

The tripartite septation of the present study, in which three dural septa are present [Figure 1]; thus, falls under the category of Type 4 septation as defined by Tubbs et al. who recorded this variation in 25% of the sample size. However, this study reports on a bilateral occurrence of the tripartite septation.

Figure 1: Bilateral tripartite dural septation of the jugular foramen. (a) Left jugular foramen, (b) right jugular foramen, IX: Glossopharyngeal nerve, X: Vagus nerve, XI: Accessory nerve, *: Dural septa

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Tubbs et al. further noted that the meningeal relations of a Type 4 septation have smaller rootlets of each of the cranial nerves of the JF that were septated and thus are more tethered within the JF. This significant tethering would then require additional dissection, thereby increasing the risk of iatrogenic injury to the cranial nerves following manipulation of the nerves by the surgeon.^[3] Furthermore, due to the differences with regard to intracranial dural sleeves of the JF, tumors in this region may have different growth patterns, for example, the Type 4 septation, or tripartite septation in the present study, has a likelihood of inhibiting significant growth of tumors into the JF.^[3]

Glomus jugulare tumors, which are found in the tunica adventitia of the jugular bulb, grow in and around the JF and cause compression of the structures that traverse the foramen.^[7] The compression of the neurovasculature results in difficulty swallowing, loss of voice, facial palsy, and pulsatile tinnitus.^[7],[8] Sethi et al. stated that compartmentalization of the JF may heighten the clinical presentations of the glomus jugulare tumor. Daley and Colliver theorized that Vernet's syndrome was caused by compression of the cranial nerves at the JF; however, Shapiro stated that large neurinomas of the glossopharyngeal, vagus, and accessory nerves passing through the JF may enlarge the JF.

The present study also recorded anteroposterior and mediolateral diameters of the JF. The right JF had an anteroposterior diameter of 9.87 mm and a mediolateral diameter of 4.54mm, whereas the left JF had an anteroposterior diameter of 9.39 mm and a mediolateral diameter of 3.28mm. This supports the trend of the previous studies in which the right JF is larger than the left JF such as Tahir and Anil (61.7%) and Sethi et al. (53.5%). Tahir and Anil reported that the size of the JF is related to the size of the transverse sinus; thus, the right JF appears to be larger than the left since the superior sagittal usually drains into the right transverse sinus.^{[9],[10],[11]}

Conclusion

The bilateral occurrence of the tripartite dural septation, as reported in the present study, highlights the importance of knowledge of the variant anatomy of the JF. Furthermore, due to the complexity of the JF and the paucity of the literature regarding the intracranial dural septations of the JF, a knowledge of this area becomes imperative to ENT surgeons and neurosurgeons in the preoperative planning of cases such as Vernet's syndrome and glomus jugulare tumors to minimize iatrogenic injury.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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