Case of the Month
Section Editor: Nicholas Stence, MD
Children's Hospital Colorado, Aurora, CO
September 2015
Next Case of the Month coming October 5 . . .
Jugular Foramen Cystic Schwannoma
- Background:
- Schwannoma is the second most common tumor arising from the jugular foramen, with glomus jugulare paraganglioma being the most common, comprising approximately 90% of masses found at this location.
- Tumors are classified by location into one of four groups. Type A is primarily intracranial, with minimal extension into the jugular foramen; Type B is centered at the jugular foramen; Type C is mostly within the extracranial carotid space; and Type D is both intra- and extracranial.
- Clinical Presentation:
- Clinical presentation of schwannomas of the jugular foramen typically result from mass effect upon the involved cranial nerves, with by far the most common presentation being unilateral sensorineural hearing loss, mimicking vestibular schwannoma. Patients may also present with the so-called jugular foramen syndrome (Vernet syndrome), which consists of unilateral dysgeusia to the posterior two-thirds of the tongue, ipsilateral vocal cord paralysis, and muscular weakness of the sternocleidomastoid/trapezius due to the respective palsy of cranial nerves IX, X, and XI.
- Key Diagnostic Features:
- On bone algorithm CT, the jugular foramen is symmetrically expanded, with a sharp, peripherally sclerotic margin, correlating with slow tumor growth. Isolated expansion of the pars nervosa portion of the jugular foramen may be seen in small masses, as the glossopharyngeal nerve (CN IX) is the most commonly involved nerve. Associated soft tissue mass is typically isodense to brain.
- On MRI, tumors are typically T1-isointense and T2-hyperintense to brain parenchyma, and may show fluid intensity T2 signal if there is associated cystic degeneration in larger lesions. There is homogeneous moderate-to-marked contrast enhancement of the solid tumor components, with variable areas of nonenhancement corresponding to cystic change.
- On angiography, there is relatively little associated tumor vascularity, with characteristic peripheral puddling on midarterial, capillary, and venous phases.
- Differential Diagnosis:
- An important imaging feature differentiating schwannoma from paraganglioma at the jugular foramen includes relative angiographic hypovascularity in comparison to the highly vascular paraganglioma. This correlates with a lack of vascular internal flow voids on MRI — the pepper of the characteristic “salt and pepper” appearance classically seen in paraganglioma. Tumor growth vector is also helpful in differentiating these two lesions. Paragangliomas normally extend superolaterally from the jugular foramen toward the middle ear, and schwannomas typically extend superomedially toward the brain stem, following the course of the caudal cranial nerves. Bone CT appearance is helpful with schwannoma, its having well-defined, peripherally sclerotic margins, while paragangliomas usually demonstrate destructive margins.
- Other tumors that less commonly involve the jugular foramen include meningiomas, metastases, chondrosarcomas, and nasopharyngeal carcinomas with perineural spread. These tumors lack the characteristic well-defined sclerotic borders typical of schwannomas on CT.
- When large, the far more common vestibular schwannoma may also extend into the jugular foramen. However, these patients will rarely have normal internal auditory canals on imaging.
- Treatment:
- Treatment of jugular foramen schwannomas is primarily based on surgical resection, with the goal of complete removal of the tumor in a single procedure. Potential surgical approach varies greatly and is guided by the specific location of the tumor and the presence of an extracranial component. For intracranial portions of the tumor, a lateral suboccipital approach is usually preferred. Radiosurgical treatment has also been shown to have promising outcomes.
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