An Unusual Anatomic Variation of the Jugular Foramen with Doubled Posterior Condylar Canal

Abstract

SUMMARY:A case of unusual anatomical variation of the jugular foramen (JF) with doubled posterior condylar canal (PCC) is reported. According to the presence of bridging, the JF can be defined as Type I (one septation, two compartments) on the right side and Type IV (three septations, four compartments) on the left side. The dome of the jugular fossa is present on the right, absent on the left. The jugular foramen shows a canal-like structure with an external and an internal opening. The lengths of the longest and widest axes of the JFs are measured as 21.93 x 16.56 mm on the right and 16.75 x 15.14 mm on the left side. The right JF is larger. The PCC is doubled on the right side and there is only one on the left side. It is essential not only to know compartments per se but also to know the structures passing through the compartments, in order to achieve desired surgical outcomes and avoid complications. INTRODUCTIONThe jugular foramen (JF) is one of the important foramina of the skull base. The ninth, tenth, and eleventh cranial nerves and the majority of the venous blood drained from the cranial cavity courses through this foramen (Athavale, 2010). It is difficult to conceptualize because it varies in size and shape in different crania, from side to side in the same cranium, and from its intracranial to extracranial end in the same foramen, and because of its complex irregular shape, its curved course, its formation by two bones, and the numerous nerves and venous channels that pass through it. The difficulties in exposing this foramen are created by its deep location and the surrounding structures, such as the carotid artery anteriorly, the facial nerve laterally, the hypoglossal nerve medially, and the vertebral artery inferiorly, all of which block access to the foramen and require careful management (Rhoton, 2000). Attempts at skull base surgery in the JF region have underscored the anatomic complexities of this region (Van Loveren et al., 1986; Kveton & Cooper, 1988). Knowledge of complex anatomy and anatomic variability is, thus, crucial in determining surgical outcomes (Athavale).The goal of this report is to delineate an unusual morphology and bridging pattern of the JFs and emphasize the importance of surgery of lesions involving this area. CASE REPORTDuring osteology demonstration classes for medical undergraduates, right and left jugular foramina were found to be different from each other in the dry skull of a 40-year-oldfemale.According to the presence of bridging, we defined JF tip I on the right side (one septation, two compartments) and Type IV on the left side (three septations, four compartments). The dome of the jugular fossa was present on the right, absent on the left. We observed the canal-like structure of the JF with an external and an internal opening. The lengths of the longest and widest axis of the JFs were measured as 21.93 x 16.56 mm on the right and 16.75 x 15.14 mm on the left side. The right JF was larger than the left one. The posterior condylar canal was doubled on the righ...