Vagal Paragangliomas



Vagal Paragangliomas


Mark S. Persky



INTRODUCTION

Paragangliomas represent highly vascular neoplasms embryologically arising from the paraganglia of neural crest origin and most commonly occur in the head and neck region. Paraganglia are part of the diffuse neuroendocrine system, previously known as the amine precursor decarboxylate system, and have the potential to secrete neuropeptides and catecholamines. Vagal paraganglia are normal structures that are intimately associated with the perineurium of the vagus nerve. While they may occur anywhere along the course of the vagus nerve, they are most often located within or just below the nodose (inferior) ganglion, which is just inferior to the skull base at the jugular foramen, and less often within the middle and jugular (superior) ganglion. Its location in this area predisposes vagal paragangliomas to early involvement of the other lower cranial nerves, including the glossopharyngeal, accessory, and hypoglossal nerves, and dysfunction of these multiple lower cranial nerves may be apparent with larger or long-standing tumors. Multicentric paragangliomas are common in familial cases (78% to 87%) but also occur in 10% of sporadic tumors, and appropriate studies should be performed to identify the presence of additional paragangliomas. Malignant vagal paragangliomas are uncommon, and their diagnosis can only be confirmed by the presence of metastatic tumor, usually within regional lymph nodes. There are no strict histologic criteria within the primary tumor that can differentiate between benign and malignant paragangliomas. Paragangliomas are highly vascular, and they characteristically demonstrate early neural involvement in addition to skull base and potential intracranial extension. These factors all contribute to the challenging nature of effectively treating these tumors. Traditionally, surgery has been the preferred method of treatment, especially with the evolution of more sophisticated cervical and skull base approaches. Postoperative cranial nerve dysfunction may be anticipated in patients with larger tumors and skull base involvement; therefore, a focus on rehabilitation efforts is necessary.

Approximately 1% to 3% of paragangliomas secrete catecholamines. A fivefold increase in catecholamines is sufficient to produce symptoms. Symptoms consistent with a functioning tumor are tachycardia, excessive sweating, weight loss, and hypertension. Secreting paragangliomas account for approximately 2% of all instances of secondary hypertension. Twenty-four-hour urine collection in these patients will show elevated levels of the catecholamine metabolites, metanephrine and vanillylmandelic acid. Serum catecholamines will show elevated levels of norepinephrine in functioning extra-adrenal paragangliomas. Elevated serum epinephrine is indicative of a concurrent pheochromocytoma. Paraganglioma familial syndrome subtypes 1 and 4 (PGL1 and PGL4) are associated with a higher incidence of concurrent pheochromocytoma. Conversely, multiple endocrine neoplasia type IIA (pheochromocytoma, medullary thyroid carcinoma, and parathyroid hyperplasia) and type IIB (pheochromocytoma, medullary thyroid carcinoma, parathyroid hyperplasia, and mucosal neuroma) are associated with head and neck paragangliomas.





PHYSICAL EXAMINATION

Vagal paragangliomas present as slowly growing, firm masses in level II of the neck. Although these represent vascular tumors, they generally do not present as pulsatile masses although there may be associated bruits. The mobility of the tumor to palpation reveals that it is fixed in a vertical direction due to its intimate involvement with the vagus nerve. Medial parapharyngeal extension may cause a bulge of the lateral wall of the oropharynx and medial displacement of the tonsil. With enlargement of the tumor, both the vagus and adjacent cranial nerves are involved. The vagus nerve is affected most commonly, followed by the hypoglossal and spinal accessory nerves; therefore, ipsilateral vocal cord paresis/paralysis, weakness of the tongue, and atrophy of the sternocleidomastoid and trapezius muscles may be presenting findings. Involvement of the sympathetic plexus may cause Horner syndrome.






FIGURE 12.1 Illustration of the anatomy of the superior aspect of the vagus nerve with adjacent structures at risk for involvement with an enlarging vagal paraganglioma.







FIGURE 12.2 MRI of a patient with bilateral vagal paragangliomas and typical anterior-medial displacement of the internal carotid arteries.




Jun 15, 2016 | Posted by in OTOLARYNGOLOGY | Comments Off on Vagal Paragangliomas

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