B. Cerebral vein thrombosis
A CT scan of the patient’s neck with contrast showed venous thrombosis of the right sigmoid-jugular complex (Figure 1, C and D), and she was diagnosed with incomplete posttraumatic Collet-Sicard syndrome (CSS) with compression of the vagus nerve (CN [cranial nerve] X).
The jugular foramen is divided into 2 portions, separated by a temporal intrajugular process that continues with a fibrous intrajugular septum (Figure 2).1 The anteromedial petrous part (historically pars nervosa) contains the glossopharyngeal nerve (CN IX) and the inferior petrosal sinus (IPS). The IPS crosses CN IX inferiorly, then CN X superiorly before flowing into the jugular bulb (JB). The posterolateral sigmoid part (historically pars vascularis) contains CN X and the accessory nerve (CN XI) anteriorly, which are closely connected during their course through the jugular foramen, and the JB posteriorly, which is the junction between the sigmoid sinus and the internal jugular vein (IJV). The CN X and XI pass through a dura-matter duplication attached to the intrajugular process, which defines the intrajugular compartment; the ascending pharyngeal artery provides a posterior meningeal artery, which also passes through this compartment. As it exits the jugular foramen, the CN IX is tethered to the internal carotid artery and the JB by dense connective tissue,2 and thus is vulnerable to vessel injuries. The cranial accessory nerve (cXI) separates from the spinal accessory nerve (sXI) to rejoin the middle ganglion of the vagus nerve, to further become the recurrent laryngeal nerve. Finally, the hypoglossal nerve (CN XII) exits from the hypoglossal canal medially to the jugular foramen, then descends between the IJV and the internal carotid artery (ICA) before crossing the ICA laterally while heading forward. Hence, the last 4 CNs share close relations to neck vessels as they exit the skull base.