International Journal of Scientific Engineering and Science Volume 3, Issue 3, pp. 25-28, 2019. ISSN (Online): 2456-7361 25 http://ijses.com/ All rights reserved A Comparative Study of the Anatomy of the Jugular Foramen and Its Variations in Dried Adult Human Skulls in Sri Lankan Population D. V. Hasan 1 , R. Hasan 2 , B. G. Nanayakkara 3 , A. Dilrukshi 4 , E. Fernando 5 1 University of Western Sydney, Australia 2 Department of Anatomy, Faculty of Medicine-Ragama, University of Kelaniya, Sri Lanka 3 Department of Anatomy, Faculty of Medicine, University of Ruhuna 4 Faculty of Medical Sciences, University Of Sri Jayawardenapura 5 General Hospital (Teaching) Kandy Abstract—The jugular foramen known to have a wide variation among different ethnicities for its anatomical variations and is also a well known area for pathological lesions such as glomus tumours, Schwannomas etc. The treatment of such lesions often involves drilling the bony area around the jugular foramen. In this study the main intention of the authors are to describe the morphometry and anatomical variations of the jugular foramen and also explain the possible dimensional distinction between the jugular foramen and the jugular fossa. A descriptive study of 27 skulls was done regardless of the gender, to describe the morphometry of jugular foramen and jugular fossa along with scaled photographs. Comparisons between the right and left jugular foramen /Jugular fossa and comparison of jugular foramen and jugular fossa on the same side were done using the student t-test. The jugular foramen was present bilaterally in all the skulls studied. The mean ML diameter of the jugular foramen was larger in the right 12.62 mm than in the left 12 mm, which is compatible with previous studies; the mean AP diameters of jugular foramen were 7.62 mm on the left side and 6.92mm on the right side. It can be concluded from the above data that the jugular foramen is morphometrically different from the jugular fossa at least from the AP diameter (t<0.05 bilaterally) and should be considered as two distinct anatomical structures rather than the fossa being considered as part of the jugular foramen. The rest of the variations observed are possibly due to constitutional, racial, gender related or genetic factors which are supported by the data from previously performed studies. Keywords— Jugular foramen, jugular fossa. I. INTRODUCTION The jugular foramen (J.Fr) is a skull opening or a bony channel consisting of a complicated bony architecture which transmits multiple significant neurovascular structures out of the base of the skull to the carotid space. The organization of the foramen is difficult to put into perspective because it varies in size and shape in different skulls, from one side to another side in the same skull, from its intracranial to extra cranial end in the same foramen, because of its complex irregular shape, its curves course, its formation by combining two bones, and the various nerves and venous channels that pass through it. (B.N et al., 2015) Since the age of 1500 A.D many researchers including Vesalius were very intrigued by the variations in shape and form of the jugular foramen. Vesalius (1543) in his illustrations of the base of skull has mentioned about the compartmentation of the jugular foramen. Multiple studies including osteological, radiological and microdisections were performed to find the compartmentalization and variations in the anatomy of jugular foramen, which led to various conflicting observations. Most of the intracranial and extracranial lesions of posterior cranial fossa may have an effect on the structures in jugular foramen in addition to intrinsic abnormalities. Various Pathologies like meningiomas, paraganglionomas, schwanomas and other inflammatory lesions of inner ear are known to have an effect on the structures in jugular foramen. In radical dissection of neck, Internal jugular vein is ligated which is prone to infarctions and most of the researchers attribute it to the ligation of the dominant internal jugular vein. Since the field of neurosurgery has become bolder in approaching this region, so arises a need of familiarity with this region (Shifan et al., 2013). A well- known fact is the jugular foramen varies in shape and size in accordance to the jugular vein (Weber & Mckenna, 1994). Presence of an enlarged dome of the foramen which accommodates the jugular bulb is also a significant anatomical variation (Hatiboglu & Anil, 1992). In addition to that numerous intrinsic abnormalities, variations of adjacent vascular structures and pathological processes occurring in posterior cranial fossa such as intracranial meningiomas, paragangliomas, schwannomas, metastatic lesions and infiltrative inflammatory processes from the surrounding structures like the middle ear might be contributing to such variations in jugular bony canal (OE, 2019). Surgical resection is considered the main treatment of choice in the majority of the above mentioned cases. Jugular foramen lesions which were once considered inoperable are now being resected with the help of advanced microsurgical techniques (Hussain et al. 2010). As neurosurgeonS become bolder in the process of approaching this region, the need for familiarity with the detailed anatomy of this region becomes greater. Several studies which were done elsewhere have described variation in size of the foramen, variation of certain compartments such as the antero-medial compartment, bipartite and tripartite divisioning of the foramen, relations and bridging bony tissue in the foramen ( Weber & Mckenna, 1994). Only a few similar studies were undertaken in Sri