ABSTRACT
Paragangliomas, also known as chemodectomas and pheochromocytomas, are thought to represent neoplasms related to paraganglia, a complex of cellular structures widely distributed in the head, neck region, and thoracic and abdominal cavities (Coupland, 1965). Two major groups of paraganglia have been recognized including the sympathoadrenal neuroendocrine system and the paraganglia of the head and neck region (Lack, 1997). The sympathoadrenal paraganglia correspond to the adrenal medullae and groups of paraganglia cells closely related to the sympathetic nervous system that extend from the neck to the base of the pelvis. The adrenal medullae secrete the catecholamines epinephrine and norepinephrine and serotonin into the bloodstream. The adrenal medullae are the most common sites of paragangliomas. Most adrenal paragangliomas, also known as pheochromocytomas, are functioning tumors usually associated with the clinical triad of systemic hypertension, headaches and diaphoresis (Lack, 1997). The paraganglia in the head and neck region are mainly associated with the parasympathetic nervous system. Some paraganglia, such as the carotid body, function as chemoreceptors that monitor changes in the arterial oxygen tension and blood Paragangliomas of the head and neck region usually correspond to non-functioning tumors.
