The parapharyngeal space (PPS) is one of the potential fascial planes of the head and neck that may become involved in various pathological processes: inflammatory and neoplastic. The latter represents less than 1% of all head and neck tumors. (1,2) Vagal paragangliomas are rare tumors that develop in the retrostyloid compartment. They arise from an island of paraganglion tissue derived from the neural crest that is located on the vagus nerve. Some of these tumors grow upward toward the skull base while others extend down into the neck. This disease is often monofocal but it may also be part of a multifocal disease that develops in either a metachronous or synchronous fashion. (3) The surgical management of this condition is associated with significant morbidity and this has prompted an expectant policy to be adopted in some patients. A difficult balance has to be struck between the effect of surgical intervention and the dangers of allowing the disease to progress. CT and MRI are commonly used in patients with suspected paraganglioma; characteristic features are evident with each modality. (4)
A 59-year-old woman presented with dysphagia and a mass on the left side of the neck (level IIa), which had grown in size over the previous 3 years. She related two episodes of syncope occurred one year before the major signs of the disease. She had no other symptoms like neck pain, hoarseness, nasal obstruction, epistaxis or tinnitus. No family history of glomus tumors was reported. On examination, a painless, semi-mobile anterior-posterior but no up and down mass was palpated in the left jugulodigastric region. Inspection of the oral cavity showed medial bulging of the left pharyngeal wall and tonsil. Indirect laryngoscopy revealed mobile vocal folds. Her blood pressure was within normal limits and the systemic physical examination findings were normal.
Transcutaneous ultrasonography with Doppler-effect showed a left parapharyngeal space tumor with rich bloody supply from the internal carotid artery. This was complete surrounded and displaced anteriorly by the tumor. External carotid artery was normally placed; internal jugular vein was posteriorly displaced by the vascular mass.
Because a paraganglioma was suspected we performed checking 24 hours urine for catecholamines: vanilmandelic acid was 6.5 mg/24 hours (normal limits for adults: 1-11 mg/24h); metanephrine was 65 mg/24 hours (normal limits for normotensive adults: 45-290 mg/24 hours).
Precontrast MR images (Fig. 1) demonstrated a large mass on the left side beginning at the level on the carotid artery bifurcation and extending superiorly and filling up the retrostyloid compartment of the parapharyngeal space. On post-contrast MR imaging (Fig. 2) prominent anteromedial displacement of the internal carotid artery and posterolateral displacement of the internal jugular vein were present. On MR angiography (Fig. 3) a large vascular mass on the left side with arterial pedicle from external carotid artery was noted. The left common carotid angiography confirmed the origin from external carotid artery of this tumor.
We performed a left transcervical approach: the tumor grown from the vagus nerve and the feeding supply was from fine arterial branches from internal carotid artery. The internal carotid artery was complete surrounded by the tumor with posterior displacement of internal jugular vein (who was resected). (Fig. 4) External carotid artery and ascending pharyngeal artery were uninvolved by the tumor. During the operation the large mass was dissected from internal carotid artery till to the jugular foramen on the skull base. We had to sacrifice the vagus and the hypoglossal nerves because the tumor could not be dissected from them. (Fig. 5)
Postoperative, the patient had left hypoglossal palsy and left vocal fold palsy in adduction position with satisfactory deglutition and no aspiration. The result of the histopathological examination of the surgical specimen was paraganglioma (glomus vagale). After one year is no recurrence of the tumor.
Paragangliomas are similar embryological to pheochromocytomas, but the term “paraganglioma” is reserved for lesions that arise in head and neck. Paragangliomas are most commonly identified at three distinct anatomic locations: 1) the carotid body, 2) the jugulo-tympanic region (glomus jugulare and glomus tympanicum, respectively), and 3) the vagus nerve (glomus vagale); however, other sites in head and neck have been described. Presenting symptoms are determined by the site of involvement, but most patients present with an asymptomatic neck mass. (5)
Perhaps the greatest advance in our understanding of the biology of paraganglioma in the past decade has been the identification of distinct genetic mutations that are directly linked to the pathogenesis of these tumors. While inherited patterns of paraganglioma - and the closely associated pheochromocytoma - have been observed and classified into four discrete clinical entities, it was not until recently that familial paraganglioma could be attributed to a germline mutation. In 2000, a genetic mutation in the succinate dehydrogenase subunit D (SDHD) gene was first implicated in familial paraganglioma, and, subsequently, two other germline mutations have been identified, in subunits B and C. (6,7) Several landmark studies have recently suggesting that up to 25% of all paragangliomas are hereditary (6). Based on the literature, only patients younger than 40 and those who have multiple tumors, a family history of paraganglioma, functional tumors or concomitant pheochromocitoma should be referred for genetic testing. (7)
Multiple imaging modalities have been advocated in the work-up of patients with PG, and what emerges from the literature is that these modalities are often complementary, and thus no single technique is optimal (8). CT and MRI are commonly used in patients with suspected paraganglioma. With iodinated contrast-enhanced CT, these tumors demonstrate intense hypervascularity. Anterior displacement of the great vessels from a vagal paraganglioma distinguishes these lesions from carotid body tumors. MRI is an ideal imaging modality for identifying small than 1 cm paragangliomas. The classically described “salt-and-pepper” appearance is related to differential flow within the tumor, representing areas of high and low flow. Use of 3D time-of flight magnetic resonance angiography can improve the sensitivity and specificity for tumor detection. Ultrasonography is of little value in paragangliomas. (4) Functional imaging (intra-arterial angiography) can clearly define the vascular supply of these tumors, which is most commonly the ascending pharyngeal artery. (9) Fluorodopa-positron emission tomography (18F-DOPA-PET) is a promising novel modality that utilizes a radioactively tagged catecholamine precursor that is readily incorporated by paragangliomas, regardless of their functional activity. (10)
With the advent of improved microsurgical techniques, novel surgical approaches, preoperative embolization and high-resolution axial imaging, surgical resection has become the standard treatment for paragangliomas. Vagal paragangliomas are approached transcervically, but lesions centered on the jugular foramen may require more extensive approaches. Regardless of the anatomic location and operative approach, the goals of surgery for PG remain the same: 1) gross total resection of disease, 2) preservation of critical neurovascular structures, and 3) soft tissue and vascular reconstruction. (4) However, due to the intimate relationship of paraganglionic tissue with the lower cranial nerves, postoperative neuropathies are common. Resection of the vagus nerve may be necessary for vagal paraganglioma, and will result in a permanent dysphagia, vocal cord paralysis, and aspiration. The facial nerve is at risk during the removal of both high vagal paraganglioma, as are the glossopharyngeal and hypoglossal nerves. Morbidity from lateral skull base and infratemporal fossa surgical approaches for large tumors involving the skull base includes meningitis, cerebrospinal fluid leak, permanent hearing loss and facial nerve palsy. (11) For this reason, some have advocated the use of external-beam radiation therapy (EBRT) for treatment of paraganglioma. Similar to conventional radiotherapy, stereotactic radiosurgery (gamma knife) neither does nor results in clinical or radio-graphic evidence of significant tumor regression, but typically results in tumor growth stabilization and improvement in neurological symptoms. (12)
Our case present a major discrepancy between the high-resolution imaging (magnetic resonance and MR angiography, carotid angiography) and the intraoperative findings. Only the ultrasonography with Doppler-effect (who was considered by all literature to be not important in diagnosis of parapharyngeal space tumor) showed the real feeding supply of this tumor. The sequelae of this operation (minor dysphagia and left vocal fold paralysis) were corrected with vocal therapy.
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