Although the cranial and spinal portions of the accessory nerve most frequently enter the vagal meatus together, a dural septum may separate them. "Parapharyngeal Masses: Their Diagnosis and Management". Anat Clin 5:41–56, 1983. FIGURE 9.4. Surgical anatomy and nuances of the expanded endonasal transdorsum sellae and posterior clinoidectomy approach to the interpeduncular and prepontine cisterns: a stepwise cadaveric dissection of various pituitary gland transpositions.

A lesion in the retropharyngeal space is responsible for Villaret's syndrome, which involves cranial nerves IX, X, XI, and XII and produces anesthesia of the palate, larynx, and pharynx; weakness of the trapezius and sternocleidomastoid muscles; atrophy and weakness of the tongue; and Horner's syndrome. 9.5 and 9.6) (24). The hypoglossal nerve passes forward across the external and internal carotid artery. If an accessory nerve injury is diagnosed or suspected it may be assessed further with electromyography and physical therapy. 9.3–9.5).

The nerve exits the inferolateral part of the hypoglossal canal and passes adjacent to the vagus nerve, descends between the internal carotid artery and the internal jugular vein to the level of the transverse process of the atlas, where it turns abruptly forward along the lateral surface of the internal carotid artery toward the tongue, leaving only the ansa cervicalis to descend with the major vessels. The superior and lateral margins of both meatus project downward and medially over the nerves entering the meatus. The zygomatic arch is removed or reflected downward with the temporalis muscle, taking care to preserve the frontal branch of the facial nerve. The lateral approach directed through a mastoidectomy, used alone or in combination with other approaches, is the route most commonly selected for lesions extending through the jugular foramen (7, 12, 22). JUGULAR FORAMEN, Neurosurgery, Volume 61, Issue suppl_4, October 2007, Pages S4–229–S4–250, https://doi.org/10.1227/01.NEU.0000296227.70319.6E. The jugular foramen is positioned below the internal acoustic meatus and superolateral to the hypoglossal nerves entering the hypoglossal canal. 9.4). The jugular foramen is located between the temporal and the occipital bones.

The inferior petroclival vein courses along the extracranial surface of the petroclival fissure and is a mirror image of the inferior petrosal sinus, which courses along the intracranial surface of the fissure (Fig. C, enlarged view of the mastoidectomy.

The glossopharyngeal, vagus, and accessory nerves arise from the medulla as a line of rootlets situated along the posterior edge of the inferior olive in the postolivary sulcus (Figs. The lower vagal and accessory roots pass across the surface of the jugular tubercle. FIGURE 9.3. Displacement of the digastric muscles exposes the transverse process of C1 (where the superior and inferior oblique muscles attach). The jugular process of the condylar portion of the occipital bone, which extends behind the jugular foramen and connects the clival and squamosal parts of the occipital bone, forms the posteromedial wall of the foramen. On bone algorithm CT, the jugular foramen is symmetrically expanded, with a sharp, peripherally sclerotic margin, correlating with slow tumor growth. Access to the jugular foramen from a lateral trajectory is obstructed by the mastoid and styloid processes, the transverse process of C1, and the mandibular ramus.42 The deep potential spaces along the foramen include the middle layer of the deep cervical fascia (buccopharyngeal fascia) anteromedially, the deep layer of the deep cervical fascia (prevertebral fascia) posterolaterally, and the superficial layer of the deep cervical fascia laterally.44 These potential spaces are important in understanding the spread of tumors in this region. The vaginal process of the tympanic bone, which separates both the carotid canal and sigmoid part of the foramen from the glenoid fossa, is the site of attachment of the styloid process to the skull base. The upward bulging of the superior margin of the jugular bulb creates a rounded fossa in the lower surface of the temporal bone below the internal auditory canal. The tensor tympany muscle passes backward above the eustachian tube and gives rise to a tendon that turns sharply lateral around the trochleiform process to attach to the malleus. The glossopharyngeal, vagus, accessory, and hypoglossal nerves exit the skull on the medial side of the internal carotid artery and jugular vein. The deep and greater petrosal nerves join to form the vidian nerve, which passes forward through the vidian canal to join the maxillary nerve and pterygopalatine ganglion in the pterygopalatine fossa. The intrajugular process of the temporal bone protrudes farther into the jugular foramen than the opposite process from the occipital bone, and may infrequently reach the smaller intrajugular process of the occipital bone, dividing the jugular foramen into two bony foramina. This is because the main function of the trapezius muscle is to elevate and retract the scapula. The walls of the jugular foramen are formed anterolaterally by the petrous bone and posteromedially by the occipital bone.42,43 The foramen is directed in an anterior, lateral, and inferior direction. In it are joined the sigmoid and the inferior petrosal sinuses. The
internal carotid artery ascends to enter 
the carotid canal in front of the jugular 
foramen. The accessory nerve departs the vagal ganglion after it exits the jugular foramen and descends obliquely laterally between the internal carotid artery and internal jugular vein and then backward across the lateral surface of the vein to reach its muscles. This coiled configuration is thought to protect the nerve from traction injury secondary to routine range of motion in the upper extremity (Tubbs et al., 2010). The lateral wall of the vestibule and cochlea have been removed. According to morphometric studies, the jugular foramen can be more accurately described as a triangular canal with an endocranial (~14.5 × 7 mm) and an exocranial opening (~9 × 17 mm). Drilling can be extended to the posterior fossa through Kawase’s triangle or through the clivus to the contralateral internal carotid artery (14). FIGURE 9.4. A more specific physical exam finding, the “triangle sign,” has been proposed by Levy et al. Hakuba A, Hashi K, Fujitani K, Ikuno H, Nakamura T, Inoue Y: Jugular foramen neurinomas. apical foramen an opening at or near the apex of the root of a tooth. Occasionally, the edge of this ridge extends medially toward the adjacent part of the temporal bone to create a deep groove in which the nerve courses or it may reach the temporal bone to form a canal, which surrounds the glossopharyngeal nerve as it passes through the jugular foramen. It is located behind the carotid canal and is formed in front by the petrous portion of the temporal, and behind by the occipital; it is generally larger on the right than on the left side. Rarely it arises from the origin of the occipital artery. The facial and vestibulocochlear nerves and labyrinthine artery enter the internal acoustic meatus. Katsuta T, Rhoton AL Jr, Matsushima T: The jugular foramen: Microsurgical anatomy and operative approaches. 1918. In a review of SAN injury malpractice cases, it was discovered that the rate of plaintiff compensation was 84% (Morris, Ziff, & Delacure, 2008). 9.5).

Neurosurgery 47(3), 2000, 10.1097/00006123-200105000-00065. BACKGROUND: Surgery plays a crucial role in the management of jugular foramen schwannomas (JFSs). M. Devereaux, B. Katirji, in Encyclopedia of the Neurological Sciences (Second Edition), 2014.