European Journal of Cardiovascular Medicine

The jugular foramen is a bony canal in the posterior cranial fossa, located between the temporal and occipital bones at the posterior end of the petro-occipital fissure, above and lateral to the foramen magnum. The upper border of the foramen contains an intrajugular process, which divides the foramen into a large posterolateral compartment, the sigmoid part, which contains the sigmoid sinus accompanied by a meningeal branch of the occipital artery; and a small anteromedial compartment, the petrosal part, which contains the inferior petrosal sinus accompanied by a meningeal branch of the ascending pharyngeal artery. The glossopharyngeal, vagus, and accessory nerves course between the petrosal part and sigmoid part, lying medial to the intrajugular process[1,2].

It is generally said that, although the jugular foramen is larger on the right side compared to the left, its size as well as its height and volume vary in different racial groups and sexes. The jugular foramen is the main route of venous outflow from the skull and is characterized by laterality based on the predominance of one of the sides. Irregular shape of the foramen, its formation by two bones, and the numerous nerves and venous channels that pass through it contribute to the complex anatomy of the foramen. The jugular foramen lies between the occipital bone and the petrous part of the temporal bone, and it is elongated and irregularly shaped. It is the chief route for the venous outflow from the skull.

The glossopharyngeal, vagus and cranial part of spinal accessory nerve pass through this and exit the cranial cavity. The neural and vascular compartments are generally separated by a bone projection called the intrajugular process. The foramen can have many variations in its shape and size. The so-called anomalies of the jugular bulb such as glomic tumors are related with the jugular foramen, as they come in direct contact with structures that cross it, like the internal jugular vein, the internal carotid artery, and the cranial nerves. Moreover, schwannomas, metastatic lesions and infiltrating inflammatory processes can also occur in the jugular foramen[3,4,5]. The present study conducted to study morphological and morphometric features of jugular foramen , which will help to neurosurgeons, forensic experts and otolaryngologists.

The present study was conducted in 72 adult dry skulls, which were collected for study in multiple medical and dental institutions in Karnataka.  All the skulls were examined carefully and excluded damaged skulls. We have measured the jugular foramen - Anteroposterior diameter — maximum anteroposterior diameter of jugular foramen was taken into recorded. Mediolateral diameter of jugular foramen was measured by taking distance between medial-most and lateral most point of the foramen. We have also observed the fossa width and depth of fossa(Fig 1). All these measurement with help of vernier callipers. All the measurements were taken bilaterally. Statistical analysis was performed with SPSS version 11. The Mean+SD of each dimension was computed. A comparison between right and left jugular foramina was made by using Student’s t-test.

We have conducted this study in 72 skulls of multiple medical and dental institution of Karnataka. We have measured the anteroposterior diameter of jugular foramen and medial  to later diameter in all skulls right and left side. We have included undamaged skulls at any side, all the foramina were intact. We have observed that anteroposterior diameter was less than medial to lateral diameter. The anteroposterior diameter was ranged between 4 - 16 mm and medial to later diameter was 12 – 25mm.

Jugular foramen is normally divided in to three compartments by two septa, usually complete partition is not common feature. In present study we have observed in 2 skulls with complete separation with two septa in to three compartments. We have also observed in the skulls Jugular fossa, we have recoded width and depth of jugular fossa and tabulated. We have also seen about dome of jugular fossa, in 28(38.88%) skulls we have observed the presence of a prominent superior jugular bulb was present bilaterally. Depth of the fossa was measured. Most of the foramina were having depth between 5 and 20 mm(Table 1).

The sigmoid sinus, jugular bulb, inferior petrosal sinus, meningeal branches of the ascending pharyngeal and occipital arteries, the ninth through eleventh cranial nerves with their ganglia, the tympanic branch of the glossopharyngeal nerve, the auricular branch of the vagus, and the cochlear aqueduct are among the structures that cross the jugular foramen. The carotid artery anteriorly, the internal carotid artery, and other important nearby tissues make it difficult to expose this canal because of its deep placement. The size of the internal jugular vein and the existence or absence of a pronounced superior bulb is related to the size and form of the jugular foramen. Typically, the right foramen is larger than the left. The intracranial venous sinuses vary greatly from person to person. which explains the variance in jugular foramen size and form. At the 23mm stage of development, the human embryo already exhibits disparities in the size of the two internal jugular veins, which are likely due to variations in the pattern of development of the right and left brachiocephalic veins[6,7,8,9,10].

In present study the anterio-posterior diameter of right jugular foramen ranged between 4.16 -15.72 mm and mean value was 10.54+3.14 and in left it was ranged between 3.42 – 14.72 and average was 8.62+3.12 and t value was 0.02*. In present study the Medial to Lateral diameter of jugular foramen of right ranged between 12.12 -24.84mm and mean value was 16.62+4.42mm and in left it was ranged between 8.64 – 22.48 and average was 15.38+4.46 and t value was 0.05*. In present study the Width-jugular fossa of jugular foramen of right ranged between 4.84 -13.96 mm and mean value was 9.18+2.34mm and in left it was ranged between 3.65 – 12.76 and average was 8.26+2.88 and t value was 0.01*. In present study the Width-jugular fossa of jugular foramen of right ranged between 5.52 – 18.64 mm and mean value was 12.64+5.72mm and in left it was ranged between 4.76 -22.98 and average was 12.16+3.06 and t value was 0.16.

In previous studies of Osunwoke et al[11], Idowu[12], Vijisha et al[13]. found the mean length of the right and left jugular foramen as 15.76, 13.90, 17.33 mm and 13.39, 14.11, 15.3 mm respectively, while the mean width of the right and left jugular foramen was 9.34, 10.22, 12.13 mm and 7.54, 9.57, 9.27 mm respectively. In Gupta et al[3] study, found the mean length, width on right and left side as 11.22, 16.52 and 9.52, 16.02 mm. In these studies, also found that the right jugular foramen was larger than the left that we also got in our study. In present study we have seen about dome of jugular fossa, in 28(38.88%) skulls we have observed the presence of a prominent superior jugular bulb was present bilaterally. In study of Khanday et al [14], found that in 40% and 29% of cases dome was present on right and left side, they found the mean right and left A-P diameter, latero-medial diameter, area of jugular foramen as 10.06, 14.6, 118 mm and 8.9, 13.9, 90 mm.

In study of Singla et al[15]. found the mean right and left anterior – posterior diameter, latero-medial diameter of jugular foramen, width, depth of jugular fossa as 9.32, 15.67, 8.99, 11.11 mm and 7.34, 14.85, 7.54, 11.04 mm and his study reported that the domed bony roof in jugular foramen in 72% of cases. Pereira et al[4]. found the mean right and left A-P diameter, latero-medial diameter of jugular foramen as 9.21, 15.82 mm and 8.65, 15.86 mm in study Gupta et al[3] the values are 11.22, 16.52 mm and 9.52, 16.02 mm. The average width of jugular fossa in the Singla et al[15] study was found to be 8.99 and 7.54 mm on the right and left side respectively. In study of Anson[16] noted the depth of jugular fossa to range from 0-14 mm with most of the specimens with less than 7 mm. The variance in jugular fossa size may be caused by the elevated jugular bulb, which when in touch with the tympanic membrane interferes with the ossicular chain and ultimately blocks the round window niche, resulting in conductive hearing loss[15].

Understanding the morphology, compartmentation, and arrangement of the structures within the jugular foramen enables one to infer the locations of numerous structures from photographs of the area surrounding the jugular foramen. The jugular foramen's surgical anatomy is intricate, as are its components. Therefore, when surgically treating this complicated area, having a thorough understanding of its variations and the connections between the neurovascular structures is essential to maximizing the surgical result and minimizing postoperative problems. The results of this may be utilized in interpreting jugular foramen imaging and understanding how neurovascular structures are involved or spared in jugular foramen lesions.

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