Glomus complex tumors, also called chemodectomas or nonchromaffin paragangliomas, are slow-growing lesions arising from nests of chemoreceptor tissue located in various parts of the body. The four main locations of glomus tissue within the head and neck are (1) at the carotid bifurcation (carotid body tumor); (2) in the inferior ganglion region (ganglion nodosum) and cervical portion of the vagus nerve (glomus vagale or vagal paraganglioma or vagal body tumor); (3) in the jugular bulb region (glomus jugulare); and (4) in the middle ear cavity (glomus tympanicum).1, 2, 3, 4, 5, 38, 39, 62 Less common locations include the larynx4; the nasal cavity and nasal sinuses6; nasopharynx28; orbit (ciliary ganglion)1, 19; sphenopalatine fossa40, 41; aortic arch (aortic arch bodies) and its branches; surface of the lungs; bladder20, 21, 40; and the facial canal.9, 15, 30 Functioning tumors of paraganglionic tissue, of which the pheochromocytoma or chromaffin paraganglioma or catecholamine-secreting adrenal intramedullary tumor20, 21, 40 is the best known, may be responsible for paroxysmal hypertension, severe hypertensive crisis, and uncontrollable hypertension. Ninty-three percent of the functioning paragangliomas are found in the adrenal medulla. Functional activity in extra-adrenal paragangliomas is rare.14 Active glomus jugulare,14 functioning carotid body tumor,7, 25 and functioning paraganglioma of the pterygopalatine ganglion region40, 41 have been reported.
Paraganglia are a group of specialized organs (chemoreceptors) that are distributed throughout the body. The paraganglion system includes the adrenal medulla, the chemoreceptors (i.e., carotid and aortic bodies); vagal body; and small groups of cells in association with the head and neck and thoracoabdominal autonomic ganglion cells. Each of these organs has common features, including a neural crest origin; a relationship to parasympathetic nerve fibers (parasympathetic innervation); a similar function; and essentially a similar histologic and histopathologic pattern.20, 21, 62 Although they share a common embryologic origin (primitive neural crest), they manifest certain anatomic differences and functional specialization.16 For example, the adrenal medulla is a neuroendocrine organ, producing epinephrine and norepinephrine (catecholamines); its cells are chromaffin positive, and tumors arising from the adrenal medulla, the pheochromocytomas, or catecholamine-secreting adrenal intramedullary tumors are often functionally active. On the other hand, the carotid and aortic bodies are chemoreceptors; their cells are usually chromaffin negative and paragangliomas arising from these organs are seldom functioning.
The nomenclature of paragangliomas is confusing and before the work of Glenner and Grimley20 was poorly standardized. Glomus tumors are the most common neoplasms of the middle ear and are second in frequency only to vestibular schwannomas within the temporal bone.38, 39 Glomus jugular tumors are indolent, locally destructive lesions arising from the paraganglionic tissue surrounding the jugular bulb, located in the jugular fossa.29 Glomus tympanicum tumors arise from glomus tissue in the middle ear. Jugulotympanic glomus bodies are closely associated with Jacobson's nerve, the tympanic branch of glossopharyngeal nerve, and the auricular branch of the vagus (Arnold's) nerve (Fig. 1). Both nerves are supplied by the anterior tympanic artery, a branch of the ascending pharyngeal artery.
CT scanning has been used extensively in the diagnosis of glomus tumors of the temporal bone. Dynamic CT scan can provide further information in the differential diagnosis of paragangliomas of the head and neck (Figs. 2 and 3).36, 37, 38, 39 Glomus complex tumors (paragangliomas) are highly vascular and, histologically, these tumors are composed of nests of cells separated by numerous vascular channels in a fibrous matrix. This is seen on MR images as multiple areas of low signal related to the high velocity of rapid arterial and venous blood flow present in the matrix of these tumors (Figs. 4 and 5).37 Olsen et al,44 in a review of 15 patients with paragangliomas, found this characteristic in 12 patients. MR imaging is superior to CT scanning in providing exact delineation of glomus tumors and better differentiation of tumor from inflammatory tissue and areas of hemorrhages. In addition, the relationship of glomus tumors to the adjacent jugular vein, carotid artery, membranous labyrinth, facial nerve, and intracranial structures is better demonstrated by MR imaging (Fig. 6).38