Surgery for Glomus Tumors and Other Lesions of the Jugular Foramen

Tympanic Tumor

Tympanic tumors arise from the glomus body of the promontory along the Jacobson nerve. The tumor is confined entirely to the mesotympanum, and all of its borders can be observed with routine otoscopy. This small tumor could not arise from the jugular bulb, or it would extend beyond the inferior margins of the tympanic annulus. Although the appearance of these lesions is characteristic, any vascular tumor of the middle ear must be differentiated from an aberrant carotid artery or dehiscent jugular bulb. An aberrant carotid artery lies more anteriorly and is paler than the glomus tumor. The jugular bulb lies more posteriorly and is darker blue. Computed tomography (CT) definitively excludes those vascular anomalies and ensures that the mesotympanic lesion is not the most lateral portion of an atypical jugular bulb tumor.

Tympanomastoid Tumor

Similar to tympanic tumors, tympanomastoid tumors arise from the glomus body on the promontory. However, they extend beyond the tympanic annulus inferiorly or posteriorly. Because there is no clinical way to delineate the tumor’s extent, any patient with a tumor that extends beyond the tympanic annulus must have a thorough radiographic evaluation. The key feature of this tumor category is that the lesion has been reported not to involve the jugular bulb itself. Tympanomastoid tumors may extend into the mastoid and into the retrofacial air cells.

Jugular Bulb Tumor

Jugular bulb tumors arise from the glomus body of the dome of the jugular bulb. Lesions may extend into the middle ear and into the bulb itself. This lesion is limited to involvement of the middle ear, mastoid, and jugular bulb. By definition, it does not extend onto the carotid artery or medially into the skull base or intracranially.

Carotid Artery Glomus Tumor

Carotid artery glomus tumors arise from the jugular bulb but extend beyond the confines of the jugular bulb and vein and contact the carotid artery. Small tumors of this category may involve only the carotid artery at the skull base, whereas larger tumors may extend far medially and may involve the horizontal portion of the internal carotid artery (ICA) and the petrous apex.

Transdural Tumor

Transdural tumors arise from the jugular bulb and extend not only to the ICA but also through the jugular foramen intracranially.

Glomus Vagale Tumor

Glomus vagale tumors arise from the glomus body along the vagus nerve at the base of the skull. Because glomus vagale tumors do not begin within the temporal bone, they are often larger than are glomus tumors of the temporal bone itself because they produce symptoms of pulsatile tinnitus and hearing loss later than do jugular bulb or middle ear lesions. Clinically, these lesions produce vocal cord paralysis before the onset of hearing loss or tinnitus or the appearance of a vascular middle ear mass. In contrast, glomus tumors of the temporal bone produce otologic symptoms before the onset of vocal cord paralysis.

Jugular Foramen Schwannoma

Although schwannomas are the second most frequently occurring tumor of the jugular foramen, they still are extremely rare. They arise from the Schwann cells of CNs IX, X, and XI. The most common cranial nerve affected is the vagus nerve. ^, The clinical distinction between glomus vagale tumors and vagale schwannomas is that glomus vagale tumors cause vocal cord paralysis earlier in their course than do schwannomas.

The clinical presentation of a jugular foramen schwannoma depends on the growth pattern. Kaye et al. categorized three different patterns: A, B, and C. Type A tumors occur primarily in the posterior fossa. Type A tumors with intracranial extension may manifest with CN IX, X, or XI palsies. Similar to most cerebellopontine angle tumors, hearing loss, imbalance, or both may be the only significant presenting symptoms. Type B tumors remain confined to the skull base with extension often into the clivus. Type C tumors begin in the jugular foramen and extend inferiorly into the neck. Type B and C tumors manifest more frequently with lower cranial neuropathies than do type A tumors.

Radiological assessment is performed with magnetic resonance imaging (MRI) and CT. MRI of the jugular foramen schwannoma reveals a smooth contoured mass that is isodense on T1-weighted images; high signal intensity is usually noted on T2-weighted images, and significant enhancement occurs on T1-weighted gadolinium scans. CT is helpful in differentiating schwannoma from glomus jugulare tumors. Schwannomas tend to produce smooth erosion of the jugular foramen. Glomus tumors tend to exhibit an irregular bone margin at the jugular foramen. The third most common lesions in this area are meningiomas of the jugular foramen. These lesions may be difficult to distinguish from schwannomas preoperatively. An enhancing dural tail on MRI is helpful. These lesions also tend to infiltrate the bone around the jugular foramen, rather than smoothly enlarge it.

Routine Hearing Tests

Air, bone, and speech audiometry are performed to assess the degree of conductive and sensorineural hearing impairment.

Computed Tomography (CT)

The mainstay of assessment of glomus tumors of the temporal bone is thin-section (1.0-mm thick) cranial CT using the bone algorithm. Tumors confined to the middle ear and mastoids are distinguished from those that involve the jugular bulb. Extensive lesions that extend onto or medial to the ICA and lesions that extend transdurally are also defined by this technique. Because the jugular bulb is the major consideration in preoperative planning, CT supplemented by flow-sensitive studies such as magnetic resonance venography (MRV) and computed tomography angiography (CTA) has supplanted retrograde jugular venography in assessing the involvement of the jugular bulb.

Magnetic Resonance Imaging (MRI)

Because bone involvement by tumor is not clearly shown on MRI, this technique provides only adjunctive information regarding the extent of tumor involvement. If the diagnosis is in question, MRI combined with CT provides exquisite preoperative guidance in the differential diagnosis of petrous apex lesions. MRI can indicate occlusion of the jugular bulb and vein because the normal flow signals are altered. In intradural tumors, MRI can delineate the tumor-brain interface and the relationship of the lesion to the intradural structures more clearly. MRI must be interpreted cautiously because T1 images of glomus tumors may overestimate the degree of tumor involvement. Marrow-containing bone of the petrous apex is hyperintense and indistinguishable from enhancing tumor in the petrous apex (unless specific fat suppression algorithms are employed). Magnetic resonance angiography (MRA) and MRV offer another diagnostic tool in evaluating glomus tumors. In their present form, however, MRA techniques cannot provide adequate imaging resolution to define the feeding vessels to the tumor. Similarly, CTA is another useful technology in evaluating vascular temporal bone lesions which often provides better resolution than does MRA ; however, the role of these techniques in the preoperative assessment of glomus tumors has not been fully clarified. ^,