Cervical Schwannoma of the Vagus Nerve: Systematic Review and Two Illustrative Cases

Background: Cervical schwannoma is a rare and benign tumor exclusively developed from the cell of Schwann that rarely involve the vagus nerve. Methods: We have conducted a retrospective review with strategy of the consulted references and database included articles published in Portuguese, English and French in PUBMED, MEDLINE, EMBASE, LILACS and SciELO, since 1936 until the present day, associated with a description of two illustrative cases. Both patients presented with a history of painless palpable mass in the cervical region. Results: About 160 cases has been described in literature. Most cases of manifest between the third and sixth decades of the patient's life as a slow growing firm, painless mass in the lateral neck. Imaging is essential to management. Histopathological examination can reveals encapsulated, biphasic spindle cell neoplasia. The best choice of treatment for this type of tumor is complete surgical removal with preservation of the vagus nerve by means of intracapsular resection. In both ilustrative cases the lesions were diagnosed by means of imaging studies and were totally ressected. Surgical findings and histopathology confirmed the diagnosis of vagus nerve schwannoma. There was no recurrence at five years of follow-up. In one case there was disphonya that solved within six months after the surgery. Conclusion: Vagus nerve schwannomas are rare benign tumors. The enucleation technique is used to obtain the most functional preservation and complete excision without permanent deficit is possible even with the occurrence of large lesions. Introduction Schwannoma is a benign tumor exclusively developed from the cells of Schwann surrounding nerve fibers in the peripheral nervous system. These lesions may occur in the cervical region by up to 25% of cases and should be suspected in the presence of an isola ted lateral cervical mass. Surgical treatment is the best choice, especially with a growing mass. The preservation of nerve function with complete resection is often possible since tumor develops extrinsically and displaces the remaining fascicles. The pur pose of this report is present a systematic review associated with a description of two illustrative cases of this uncommon disease. Methods The search strategy of the consulted references and database included articles published in Portuguese, English an d French in PUBMED, MEDLINE, EMBASE, LILACS and SciELO. They were evaluated review articles, systematic reviews and meta - analyzes. The keywords used to find such results were: vagus nerve, schwannoma, peripheral nerve tumor, cervical vagus nerve. Papers ex cluded with cervical sympathetic chain schwannoma, jugular forame schwannoma, glossopharyngeal schwannoma, middle mediastinum, malignant cases, intrathoracic vagal nerve schwannoma, retroperitoneal schwannoma of the vagus nerve and papers containing vagus and other schwannomas without distinction. This paper presents description of two illustrative cases of this disease. Illustrative cases Case 1 L.C.M.S., 34- year- old male, perceived the tumor in the right cervical region two years ago. There has been rapid growth of the lesion. The physical exam revealed a painless nodule upon palpation in right cervical region, firm, insensitive and mobile. There was no associated dysphagia, dysphonia or neurologic deficit . Biopsy by fine - needle aspiration cytology was performed and the histological findings were compatible with schwannoma. Nuclear magnetic resonance imaging (MRI) of the cervical region was solicited and revealed expansive tumor measuring 7,7 x 3,4 x 3,0 solid with foci of heterogeneity in the inner compatible with cystic degeneration. In June 2 013, L.C.M.S. underwent microsurgery in which the lesion was totally resected by intracapsular enucleation and the nerve was preserved. Surgical exploration found a heterogeneous 8.0 x 4.0 cm mass causing anterior displacement of the internal jugular vein and vagus nerve and medial displacement of the carotid vessels, diagnosis pointed to benign schwannoma. The immediate postoperative coursed with dysphonia. Case 2 R.M.N.C., 35 - year - old female, perceived the tumor in the right cervical region. The physical exam revealed a painless nodule upon palpation in right cervical region, firm, mobile in the horizontal but not in vertical direction. There was no neurologic deficit . This case was not underwent to biopsy fine - needle aspiration cytology. Computerized tomography showed a well - defined mass with anterior displacement of the common and internal carotid artery ( 4,0 x 2,0 cm) solid, located in the carotid space, displacing previously vascular structures. Using a skin crease incision, surgical exploration found displacement of the external jugular, a well encapsulated tumor arising from the vagus nerve was noted. Tumor was enucleated with sparing of the nerve, the lesion was totally resected and the nerve preserved. In the immediate postoperative there was no neurological deficit. Histopathology showed Antoni A pallisading nucleus and verruca bodies suggestive of schwanoma. Table Discussion Cervical vagus schwannoma was first reported by Ritter in 1899 (apud Yumoto et al). 110 Since that, 160 cases has been described in the literature. This tumor most often presents as a slow growing asymptomatic solitary neck mass. 61 Most cases of cervical schwannomas manifest between the third and sixth decades of the patient’s life as a slo w growing firm, painless mass in the lateral neck. Hoarseness, pain, or cough may be the presenting complaints. The tumor usually displace the carotid arteries anteriorly and medially, jugular vein laterally and posteriorly. Generally, these lesions are mo vable transversely but not vertically. 61 Those typical features were found in our two cases. Pre - operative diagnosis of schwannoma is difficult because many vagal schwannomas do not present with neurological deficits and several differential diagnoses for tumour of the neck may be considered, including paraganglioma, branchial cleft cyst, malignant lymphoma, metastatic cervical lymphadenopathy and neurofibromas. 110 Topographic features may be helpful in distinguishing origin nerve at initial presentation: the vagal schwannomas should be displaced between the internal jugular vein laterally and the carotid artery medially, where as schwannomas from the cervical sympathetic chain displace both the carotid artery and jugular vein without separating them . 43 In our case 2, the tumor displaced the internal jugular vein laterally and anteriorly. Imaging is essential to management. CT and nuclear MRI determine tumor size, extension and relation to the internal and external carotids. 109 The MRI is considered typ ical when the mass appears as a well - circumscribed tumor lying between the internal jugular vein and the carotid artery. 48 Radiological aspects in CT can show well defined mass compressed the internal jugular vein or internal carotid 19 or rare presentation with heterogenous enhancing mass lesion in right retro styloid parapharyngeal space extending up to carotid bifurcation deep to sternocleidomastoid causing antero medial displacement of carotid vessels with obscuration of ipsilateral cervical part of inte rnal jugular vein. 61 MRI can show more details: dimensions, polycyclic contours, low signal on T1, a heterogeneous hyperintense T2 and enhanced so late and progressive after gadolinium injection among other things. 19 The use of fine - needle aspiration an d cytology is still controversial; the majority of authors does not recommend open or needle biopsy for these masses. 68 In this study, only one case was biopsied. Histopathological examination can reveals encapsulated, biphasic spindle cell neoplasia. There are more cellular areas (Antoni A) where nuclei are sometimes palisaded around collagenized bands forming structures known as Verocay bodies, as well as collagen globules, often found in sheath - derived neoplasms peripheral nerve neural disease. In other less cellular and loose stromal areas (Antoni B) cystic degeneration is often observed and hyalinized vessels. Fibrous capsule evidenced by Masson's trichrome staining 98 In particular, cystic vagal schwannomas originating from the cervical vagus nerve are extremely rare 68 limited to 160 cases in the literature. The best choice of treatment for this type of tumor is complete surgical removal with preservation of th e vagus nerve by means of intracapsular resection. 79 The two patients here reported underwent surgery with intracapsular resection. Nerve palsy is a common complication of the vagal schwannoma removal, but in many cases it recovers spontaneously when the neural integrity is preserved. 79 In our case 1, there was vocal cord palsy, which fully recovered in six months after the operation. In case 2 there was no vocal cord palsy or another complication. Horner’s syndrome is also a usual postoperative complicati on 111 absent in our cases. Conclusion Vagus nerve schwannoma is a rare benign tumor to be suspected in the presence of an isolated lateral cervical mass. Imaging studies are essential to the management. Surgical treatment is the best choice, especially if the tumor is growing. The conservation of the original nerve is often possible