Approaches to the Jugular Foramen
The complex bony and neurovascular anatomy of the jugular foramen has created the reputation for this region as one of the most difficult areas to access surgically. Developments in neuroradiology, microsurgical skull base approaches, and postoperative intensive care have transformed surgery of lesions in the jugular foramen area into a routine procedure with predictable postoperative results.
Among skull base pathologies, tumors arising in the region of the jugular foramen are relatively common. A variety of tumors can originate from the structures in or next to the jugular foramen. The differential diagnosis of primary jugular foramen tumors principally includes schwannomas and glomus jugular tumors. Several other skull base tumors may secondarily involve the jugular foramen, such as meningiomas, chordomas, chondrosarcomas, and carcinoma of the tympanic cavity. Surgery is the primary treatment option for most of these tumors. The objective of this chapter is to describe the current surgical management of jugular foramen tumors, based on the senior author′s experience during the past four decades with more than 200 jugular foramen tumors among 5000 skull base lesions.
Surgical Anatomy of the Jugular Foramen
The jugular foramen is located between the lateral part of the occipital bone and the petrous part of the temporal bone. It usually has a triangular form, with the apex of the triangle situated anteriorly and medially.1,2 From an intracranial-toextracranial projection, the jugular foramen is described as a canal coursing anteriorly, inferiorly, and laterally. In earlier descriptions, the foramen was divided into two compartments: the anteromedial compartment, called the “pars nervosa,” and the posterolateral compartment, called the “pars venosa” or “pars vascularis.” The pars nervosa contained the inferior petrosal sinus, vena canaliculi cochleae, and glossopharyngeal nerve. The pars venosa contained the vagus and accessory nerves and the proximal part of the jugular bulb.
It is now recognized that the classic compartments of the jugular foramen are not always present. The cranial nerves IX to XI follow different patterns while traversing the foramen. The nerves are separated from the jugular bulb by bone, thick fibrous tissue, or thin connective tissue.3,4
The walls of the jugular bulb are very thin compared with the thick walls of the sigmoid sinus.5 The inferior petrosal sinus commonly drains into the jugular bulb by one or more openings and usually passes between cranial nerve IX and cranial nerves X and XI.
A posterior meningeal branch of the ascending pharyngeal artery typically runs through the sheath of connective tissue in the jugular foramen to supply the bone and the dura mater. This meningeal artery is responsible for the vascular supply of most tumors in this area.
Diagnostic Evaluation
Patients with primary jugular foramen tumors usually present with a unilateral palsy of one or more of the lower cranial nerves (IX, X, or XI).5,6 Patients can also present with hearing loss, raising the suspicion of a cerebellopontine angle (CPA) tumor. Patients with large tumors may present with involvement of cranial nerves VII and XII, increased intracranial pressure, papilledema, cerebellar symptoms, or brainstem signs.7,8 Glomus jugulare tumors may produce sensorineural, conductive, or mixed hearing loss.9 Pulsating tinnitus is present in several patients and may differentiate these tumors from schwannomas. The tumor may present as a neck mass, as a mass involving the lateral pharyngeal wall, or with a jugular foramen syndrome.
A variety of lesions other than schwannomas or glomus tumors may arise from the structures within or adjacent to the jugular foramen. Meningiomas, chordomas, chondromas, chondrosarcomas, metastases, and others lesions can often be differentiated on the basis of their radiological and imaging characteristics.6,10
Radiological Evaluation
The delineation of the tumor and its relationship with the bone, vessels, and neural tissues is essential for diagnosis and preoperative planning. The preoperative neuroradiological studies should include high-resolution computed tomography (CT), magnetic resonance imaging (MRI), and cerebral angiography.10,11
High-resolution CT is performed before and after intravenous administration of contrast material. Thin slice axial and coronal images (1.5-mm slice thickness) are preferred with bone windows to demonstrate the extent of bone involvement by the tumor. Enlargement or erosion of the foramen has a significant impact on the differential diagnosis of the lesion.
MRI studies are performed with intravenous administration of paramagnetic contrast medium. Sagittal, coronal, and axial projections allow for a three-dimensional delineation of tumor extension ( Fig. 32.1 ). The tumor size and its relationship to surrounding tissues can be defined. Magnetic resonance angiography (MRA) can demonstrate the vascular involvement by the lesion, including displacement or occlusion of the venous sinuses and arteries. In selected cases, MRA has replaced the use of cerebral angiography.
Cerebral angiography can be performed to evaluate the tumor vascularization, the type and number of feeding vessels, the displacement of major cerebral vessels, and the venous drainage ( Fig. 32.2 ). Angiography might be essential for decision making in tumor management.12,13 The most important role of cerebral angiography is for the preoperative embolization of highly vascularized tumors, such as glomus jugulare tumors.
Surgical Technique
The most frequent primary tumors of the jugular foramen are schwannomas of cranial nerves IX, X, and XI, followed by glomus jugulare tumors.7–9,14 Schwannomas may be localized mainly to the CPA with little extension into the jugular foramen (type A), may be located primarily in the jugular foramen with small intracranial extension (type B), may be primarily extracranial with extension into the jugular foramen (type C), or may become extensive dumbbell-shaped tumors extending from the CPA through the jugular foramen down into the cervical region (type D).14 Type A and some type B schwannomas are resected by a lateral suboccipital route. Schwannomas with a cervical extension or large foraminal part are resected by a combined cervical and lateral extradural transmastoid infralabyrinthine approach.12
Glomus jugulare tumors are benign, highly vascularized tumors that arise extracranially, but they may be complicated by intracranial extension and internal carotid artery involvement.9,15,16 The tumor is usually unilateral, but bilateral tumors may occur. Complete surgical tumor resection is the preferred treatment in the majority of cases. Preoperative embolization of major feeding vessels reduces intraoperative bleeding, facilitates obtaining a complete surgical resection, and shortens the time required for surgery. Preoperative medical treatment is required for catecholamine-secreting tumors. Radiation therapy is reserved for rare aggressive tumors or when surgery is contraindicated.
Surgical Approaches
The choice of surgical approach is determined by the location, extension pattern, and type of lesion.12–14,17 The tumor may be located primarily in the jugular foramen and grow outside it, or the tumor may arise from structures surrounding the jugular foramen and involve it secondarily.18 Depending on these factors, two major approaches to the jugular foramen can be considered: a primary intradural approach through the CPA and a primary extradural approach through a mastoidectomy. The approaches can be used separately or together to permit a multidirectional view.
Primary Intradural Approach to the Jugular Foramen
Prophylactic antibiotics are administered. Dexamethasone is initiated to reduce the risk of postoperative edema. The patient is usually intubated nasally. Monitoring for air embolism includes intraoperative electrocardiography, arterial oximetry, capnometry, precordial Doppler ultrasonography, catheterization of the right atrium, and central venous catheterization.
The patient is placed in the semi-sitting position, with the head flexed and rotated ~30 degrees toward the side of the tumor.14,19 The legs are elevated to the level of the right cardiac atrium, and the head is fixed in place with a Mayfield head holder. All body parts subject to pressure are supported with cushions. The legs are slightly flexed to avoid stretching the peroneal nerves. Sensory evoked potentials for the median nerve are monitored throughout surgery. Cochlear nerve function is monitored by measurement of brainstem auditory evoked potentials. Subdermal needle electrodes are implanted in the orbicularis oris and orbicularis oculi muscles for continuous electromyographic monitoring of the facial nerve. The glossopharyngeal, accessory, and hypoglossal nerves are monitored by placing the electrodes in the soft palate, trapezius muscle, and tongue, respectively.
Part of the occipital and suboccipital area of the scalp is shaved; the skin is prepared, and the drapes are stapled into position. A slightly curved incision is made behind the ear. The neck muscles are divided vertically and retracted. A burr hole is created and enlarged with rongeurs to form a craniectomy that exposes the transverse sinus superiorly and the sigmoid sinus laterally ( Fig. 32.3 ). The bone opening should extend to the floor of the posterior fossa.
The dura mater is then opened in a curvilinear manner 1.5 to 2 mm medial to the sigmoid and inferior to the transverse sinus. The cerebellum is not retracted primarily. First, cerebrospinal fluid (CSF) is released from the cerebellomedullary cistern, and then a retractor is inserted to gently support but not compress the cerebellar hemisphere ( Fig. 32.4 ).
The intracranial aspect of the tumor is exposed at the CPA. After identification of the main anatomical landmarks and cranial nerves, the tumor is debulked with ultrasonic aspiration, suction, or platelet knife. Dissection of cranial nerves is performed only when sufficient internal decompression has been achieved. A two-handed technique is used and performed always in the arachnoidal planes. Usually, the intraforaminal part of the tumor can be pulled out of the foramen, into the CPA, and removed. The access to this tumor part, if required, can be extended by opening the dorsal part of the jugular foramen in a technique similar to the opening of the internal auditory canal in a case of vestibular schwannoma ( Fig. 32.1 ). The dura overlying the dorsal part of the foramen is stripped off, and its bony wall is removed using high-speed diamond drills. The intraforaminal tumor part is initially debulked, and then its capsule is dissected from the cranial nerves. An angled endoscope is routinely used to “look around the corner” and inspect the entire jugular foramen ( Fig. 32.1 ). Tumor remnants can be readily viewed and removed under direct endoscopic or microscopic control.
After tumor removal, the dura is closed in a watertight fashion, and the mastoid air cells are sealed with fat and fibrin glue. If the jugular foramen has been opened, it should be sealed with several small pieces of fat and fixed with fibrin glue. The craniectomy is reconstructed with methyl methacrylate.
Related posts:
Posterior Neuroendoscopic Applications at the Craniovertebral Junction
Stereotactic Methods of Localization and Image-Guided Surgery
Transoral–Translabiomandibular Approach to the Craniovertebral Junction
Transfacial Approaches to the Craniovertebral Junction
Bypass Options for the Posterior Fossa
Suboccipital and Retrosigmoid Approaches
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
