| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
The Ohio State University Medical Center Columbus, OH 43210
A 19-year-old man presented with a 2-year history of an asymptomatic swelling of the right side of his neck. At physical examination, a soft and nontender mass was noted. Cranial nerves II-XII were intact. Sonographic examination (not shown) revealed a 5 x 2.7 x 3 cm mass of mixed echogenicity within the right carotid space that displaced the jugular vein anteriorly. Doppler evaluation did not reveal signs of vascularity or flow. Enhanced-contrast CT scans of the neck (Fig. 2) revealed a mass within the right posterior triangle that displaced the internal jugular vein anteriorly. The lesion was well circumscribed, with irregular peripheral enhancement and a necrotic center. At surgery, the tumor was found to arise from the right vagus nerve. The tumor was excised, and the vagus nerve was preserved. At histopathologic examination, the lesion proved to be a schwannoma.
|
Tumors of the parapharyngeal space are rare, with neurogenic tumors being the most common. Neurilemomas (also known as schwannomas or neuromas) account for 55% of these tumors [1]. Approximately half of the reported parapharyngeal schwannomas arise from the vagus nerve [1]. Neoplasms of the vagus nerve include paragangliomas (50%), schwannomas (31%), neurofibromas (14%), and neurofibrosarcomas (6%) [2]. Most schwannomas of the vagus nerve are benign tumors. Most cases of schwannomas manifest between the third and sixth decades of the patient's life as a firm, painless mass in the lateral neck, with slow enlargement. Hoarseness, tenderness, or cough may be presenting complaints. Schwannomas are usually confined to the retrostyloid parapharyngeal space, although patients with schwannomas that extend into the posterior cranial fossa through the jugular foramen have been reported [1]. Schwannomas are well-encapsulated tumors with distinctive cylindrical structures (Antoni type A tissue), which are set into a nondistinctive, loose stroma of fibers and cells (Antoni type B tissue). Typical features include necrosis, hemorrhage, and cystic degeneration.
The preoperative imaging diagnosis is often difficult. Anterior displacement of the common or internal carotid artery is a characteristic finding of parapharyngeal neurogenic tumors [3]. On CT images, vagal schwannomas appear as well-defined masses, usually of higher attenuation than muscle on contrast-enhanced images. MR evaluation typically shows masses of intermediate signal on T1-weighted images and increased signal intensity on T2-weighted images, with smooth, well-delineated margins and a homogeneous overall appearance [4]. Occasionally, as in our patient, necrosis and cystic degeneration are seen. Furukama et al. [5] found that vagal schwannomas separate the common or internal carotid artery from the jugular vein, whereas schwannomas of the cervical sympathetic chain do not. This finding was not evident in our patient, in whom the jugular vein was displaced anteriorly and the common and internal carotid artery were not displaced at all (Fig. 2).
Schwannomas of the vagus nerve must be differentiated from the carotid body and glomus vagale tumors because the distinction may influence treatment planning. Carotid body tumors arise at the carotid bifurcation, splaying the external and internal carotid arteries, whereas glomus vagale tumors usually displace the internal carotid artery anteriorly or medially or both. Both glomus tumors enhance intensely on both CT and MR images and reveal a characteristic "salt-and-pepper" appearance on enhanced T1-weighted MR images because of flow voids frequently noted within the mass. This salt-and-pepper appearance is not a feature of schwannomas.
Surgical excision is the treatment of choice for both schwannomas and glomus tumors of the carotid space. Because of the care necessary to preserve important nerve functions, the surgical planning is often influenced by lesion size, location, vascularity, and relation to adjacent structures such as the vagus nerve, sympathetic chain, carotid artery, and jugular vein. Imaging can be very useful in differentiating vagal schwannomas from other lesions in this area, allowing the surgeon to plan the operative procedure to remove these tumors.
References
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
