Jugular foramen: Microscopic anatomic features and implications for neuralpreservation with reference to glomus tumors involving the temporal bone

OBJECTIVE: Our goals were to study the normal histological features of the jugular foramen, compare them with the histopathological features of glomus tumors involving the temporal bone, and thus provide insight into the surg ical management of these tumors with respect to cranial nerve function. METHODS: Ten jugular foramen blocks were obtained from five human cadavers after removal of the brain. Microscopic studies of these blocks were perfor med, with particular attention to fibrous or bony compartmentalization of t he jugular foramen, the relationships of the caudal cranial nerves to the j ugular bulb/jugular vein and internal carotid artery, and the fascicular st ructures of the nerves. In addition, we studied the histopathological featu res of 11 glomus tumors involving the temporal bone (10 patients), with res pect to nerve invasion, associated fibrosis, and carotid artery adventitial invasion. RESULTS: A dural septum separating the IXth cranial nerve from the fascicle s of Cranial Nerves X and XI, at the intracranial opening, was noted. Only two specimens, however, had a septum tone bony and one fibrous) producing i nternal compartmentalization of the jugular foramen. The cranial nerves rem ained fasciculated within the foramen, with the vagus nerve containing mult iple fascicles and the glossopharyngeal and accessory nerves containing one and two fascicles, respectively. All of these nerve fascicles lay medial t o the superior jugular bulb, with the IXth cranial nerve located anteriorly and the XIth cranial nerve posteriorly. All nerve fascicles had separate c onnective tissue sheaths. A dense connective tissue sheath was always prese nt between the IXth cranial nerve and the internal carotid artery, at the l evel of the carotid canal. The inferior petrosal sinus was present between the IXth and Xth cranial nerves, as single or multiple venous channels. The glomus tumors infiltrated between the cranial nerve fascicles and inside t he perineurium. They also produced reactive fibrosis. In one patient, in wh om the internal carotid artery was also excised, the tumor invaded the adve ntitia. CONCLUSION: Within the jugular foramen, the cranial nerves lie anteromedial to the jugular bulb and maintain a multifascicular histoarchitecture (part icularly the Xth cranial nerve). Glomus tumors of the temporal bone can inv ade the cranial nerve fascicles, and infiltration of these nerves can occur despite normal function. In these situations, total resection may not be p ossible without sacrifice of these nerves.