ABSTRACT: This case report illustrates the role of high-resolution sonography in the preoperative assessment of a schwannoma of the vagus nerve in the neck.
Case Report
Sonographic Diagnosis of a Cervical Vagal Schwannoma Thomas Le Corroller, MD,1 Fre´deric Sebag, MD,2 Vincent Vidal, MD,1 Alexis Jacquier, MD,1 Pierre Champsaur, MD, PhD,1 Jean Michel Bartoli, MD,1 Guy Moulin, MD1 1 2
Department of Radiology, Hoˆpital La Timone, 254, Rue Saint-Pierre, 13385 Marseille, France Department of Endocrine Surgery, Hoˆpital La Timone, 254, Rue Saint-Pierre, 13385 Marseille, France
Received 8 August 2007; accepted 4 January 2008
ABSTRACT: This case report illustrates the role of high-resolution sonography in the preoperative assessment of a schwannoma of the vagus nerve in the neck. Sonography identified the tumor in the right carotid space and determined its origin from the right vagus nerve, facilitating the surgeon’s approach to C 2008 Wiley preserve nerve function. V Periodicals, Inc. J Clin Ultrasound 37:57–60, 2009; Published online in Wiley InterScience (www.interscience. wiley.com). DOI: 10.1002/jcu.20474 Keywords: ultrasonography; MRI; neck; schwannoma; vagus nerve
enign peripheral nerve sheath tumors are usually divided into 2 groups: schwannomas (neurilemmomas) and neurofibromas. Schwannomas are slightly less common than neurofibromas and make up about 5% of all benign soft tissue tumors.1 Schwannomas originate from Schwann cells and typically present a true capsule composed of epineurium, which facilitates surgical excision. In the neck, several neurogenic tumors may be encountered, including schwannomas of the vagus nerve or of the cervical sympathetic chain, paragangliomas of the carotid body or of the vagal body, neurofibromas, and neurofibrosarcomas. We report a case of vagal schwannoma correctly identified on sonography.
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CASE REPORT
A 43-year-old woman presented to our institution with a painless mass in the right side of the neck Correspondence to: T. Le Corroller ' 2008 Wiley Periodicals, Inc. VOL. 37, NO. 1, JANUARY 2009
that grew slowly over a 1-year period. Physical examination revealed a soft mobile mass and intact cranial nerves. The patient underwent sonographic examination of the neck performed with an HDI 5000 scanner (Philips Ultrasound, Bothell, WA) equipped with L12-5 and CL15-7 linear-array transducers. Sonographic examination revealed a 25-mm-long mass within the right carotid space that displaced the right jugular vein anteriorly (Figure 1A). The lesion was well circumscribed with a heterogeneous echotexture and was primarily hypoechoic, with a mild posterior acoustic enhancement (Figure 1B). Color Doppler examination did not reveal internal vascularity. A longitudinal sonogram showed a direct connection to the right vagus nerve, which was clearly seen abutting the margins of the mass (Figure 2). The controlateral vagus nerve was morphologically normal. MRI verified a sharply marginated mass in the right carotid space separating the common carotid artery from the jugular vein and displacing anteriorly the right jugular vein. On T1 SEweighted MR images, the lesion was homogeneous and isointense to skeletal muscle. Conventional T2 SE-weighted MR images demonstrated the lesion to be moderately heterogeneous and hyperintense relative to adjacent fat. After intravenous administration of gadolinium-based contrast material the lesion showed irregular peripheral enhancement and a myxoid center (Figure 3). Surgical exploration revealed a solid tumor eccentrically developed from the right vagus nerve. Surgical excision successfully preserved the vagus nerve. Pathologic evaluation 57
LE CORROLLER ET AL
FIGURE 1. Schwannoma of the vagus nerve. (A) Longitudinal and (B) transverse sonograms obtained with a L12-5 linear-array transducer show a 25-mm mass (arrows) within the right carotid space, between the common carotid artery (CA) and the internal jugular vein (JV), which is displayed anteriorly.
FIGURE 2. Longitudinal sonogram obtained with a CL 15-7 lineararray transducer demonstrates the well-defined mass developed eccentrically from the right vagus nerve (arrowheads).
demonstrated a well-circumscribed, xanthochromic, firm mass. Microscopic examination confirmed the preoperative diagnosis of schwannoma, demonstrating Antoni A areas (richly cellular, arranged in interlacing fascicles or in short bundles) and Antoni B areas (less cellular, with more myxoid component) (Figure 4). On immunohistochemistry, the tumor was S-100– positive. 58
FIGURE 3. T1 SE-weighted MRI scan after intravenous administration of gadolinium shows a sharply marginated mass (arrow) in the right carotid space between the common carotid artery and the jugular vein displaced anteriorly. The lesion exhibits irregular peripheral enhancement and a myxoid hypointense center.
DISCUSSION
Schwannoma is a commonly encountered benign soft tissue tumor, most frequently occurring between the age of 20 and 50 years.1 Sites of involvement include nerves of the head and neck, the flexor surface of the upper limbs and the posterior area of the lower limbs (particularly the peroneal and the ulnar nerves), the posterior JOURNAL OF CLINICAL ULTRASOUND
CERVICAL VAGAL SCHWANNOMA
FIGURE 4. Photomicrograph shows confirmed Antoni B areas, which are moderately cellular with a myxoid component (hematoxylineosin saffron 320).
mediastinum, and the retroperitoneum.2 Schwannomas typically present clinically as a slowly growing and painless mass, without neurologic symptoms. In almost 5% of cases, schwannomas are not solitary and can be associated with neurofibromatosis. Pathologically, schwannomas are fusiform masses contained within a true fibrous capsule and develop eccentrically from the nerve.3 Residual intact nerves fascicles are usually displaced to the periphery of the mass, allowing successful surgical resection.4 Clinical presentation of schwannomas is usually nonspecific. Differential diagnosis in the neck includes other neurogenic tumors (neurofibroma, paraganglioma, neurosarcoma), enlarged lymph node, thyroid or parathyroid nodule, branchial cleft cyst, and lipoma. An appropriate diagnostic tool remains essential in the preoperative diagnosis, allowing the surgeon to plan the correct operative procedure. Several imaging modalities provide information about the nerve tumor preoperatively. CT and MRI offer useful morphologic and topographic data about the nerve tumor and adjacent structures. High-resolution realtime sonography is known to be effective in imaging large normal nerve trunks and nerve masses in the extremities.5 Sonography provides detailed images of nerves during static and dynamic examinations with flexion and extension maneuvers, showing the nerve as immobile structure on longitudinally oriented sonograms.5 Doppler evaluation may help distinguish a nerve tumor from a thrombosed aneurysm or from an enlarged lymph node.6 Sonograms of schwannoma typically show a well-defined, ovoid or round, hypoechoic, generally homogeneous solid mass with a moderate to VOL. 37, NO. 1, JANUARY 2009
marked posterior acoustic enhancement and eccentric positioning of the nerve trunk relative to the schwannoma.5,7 The homogeneous and decreased echogenicity of schwannomas may be explained by the uniform cellular pattern, allowing a moderate to marked sound-through transmission.8 A heterogeneous pattern of the mass (as observed in our case) is probably due to internal cystic or necrotic changes. The associated nerve may show thickening and loss of anisotropy. Color Doppler examination shows various degrees of vascularity ranging from minimal to abundant. It is easily obliterated with excessive pressure from the ultrasound probe.9 Threedimensional sonography may provide volumetric data containing all the information needed by a surgeon: volume, morphology, and anatomic relationships of the lesion.10 In our case, the lesion was clearly identified on both sonography and MRI in the right carotid space, displacing the jugular vein anteriorly. The lesion separated the right common carotid artery from the right jugular vein, as may be observed in vagal schwannomas but not in schwannomas of the cervical sympathetic chain.11 Sonography showed the direct continuity of the tumor with the right vagus nerve. Identification of such a nerve entering and exiting a mass is pathognomonic for a peripheral nerve sheath tumor.2,12 Dynamic examination confirmed in real-time the fixation of the mass to the vagus during changes of the head’s position. In conclusion, high-resolution sonography can be very useful in the preoperative diagnosis of schwannoma of the vagus nerve in the neck and can facilitate treatment planning.13
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types of imaging diagnostically useful? Clin Imaging 2006;30:201. 11. Furukawa M, Furukawa MK, Katoh K, et al. Differentiation between schwannoma of the vagus nerve and schwannoma of the cervical sympathetic chain by imaging diagnosis. Laryngoscope 1996; 106:1548. 12. Suh JS, Abenoza P, Galloway HR, et al. Peripheral (extracranial) nerve tumors: correlation of MR imaging and histologic findings. Radiology 1992; 183:341. 13. Kehagias DT, Bourekas EC, Christoforidis GA. Schwannoma of the vagus nerve. AJR Am J Roentgenol 2001;177:720.
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