Glomus tympanicum tumor.

A 42-year-old woman presented with pulsatile tinnitus and some difficulty hearing in her left ear. Otoscopic examination detected a reddish retrotympanic mass. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed findings consistent with a glomus tympanicum tumor (figure). The lesion was removed surgically via tympanotomy, and the patient experienced an uncomplicated and complete recovery.

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Glomus tympanicum tumors are benign, highly vascular masses that typically arise from glomus bodies on the cochlear promontory. (1,2) Glomus bodies are made up of paraganglionic tissue that is present at birth, and they are part of the extra-adrenal neuroendocrine system. They are usually associated with autonomic nervous tissue, and they function as chemoreceptors. A progressive involution to complete obliteration at puberty is the rule for most paraganglionic cells--one exception being the carotid bodies. (1) Glomus tumors are thought to arise as an over-response to changes in body homeostasis.

Glomus tympanicum tumors are the most common primary neoplasms of the middle ear. (1) They arise from chemoreceptors along Jacobson's nerve and the tympanic branch of the glossopharyngeal nerve. While most are found on the cochlear promontory, they can arise anywhere along the course of Jacobson's nerve. (1-3)

Clinically, the two most common presenting symptoms of a glomus tympanicum tumor are, in order, pulsatile tinnitus and conductive hearing loss. (1-4) Otoscopic examination will usually detect a pulsatile, red, anteroinferior retrotympanic mass. (1-3) Patients typically present between the ages of 40 and 60 years, and the female-to-male ratio is 3:1. (1,2)

It can be difficult to distinguish a glomus tympanicum tumor from a glomus jugulare tumor or an aberrant internal carotid artery (ICA) on the basis of the clinical presentation alone. Differentiation from a glomus jugulare tumor, which arises in the adventitia of the dome of the jugular bulb, is important because the two tumors require different surgical approaches for complete resection? (1,3,4) Differentiation from an aberrant ICA is important because an unnecessary biopsy can have disastrous consequences. (2) Thus, imaging plays an important role in the evaluation of these lesions. CT and MRI will show a glomus tympanicum tumor as a focal, well-circumscribed mass with a flat base on the cochlear promontory; MRI will show a strong homogenous enhancement with contrast administration. (2,3) CT will show an aberrant ICA as a tubular mass that can be followed as it crosses the middle ear cavity and joins the horizontal petrous ICA. (2) A glomus jugulare tumor can be identified radiographically by its jugular fossa epicenter and associated permeating, destructive changes in the adjacent bone. (2,3)

The treatment of choice for glomus tympanicum tumors is surgical: tympanotomy for smaller lesions and mastoidectomy for larger lesions. Postoperative complications are uncommon, and recurrent or residual tumor is found in fewer than 5% of patients. (2,4,5)

References

(1.) Koenigsberg RA, Dastur C, Kim R. Glomus tumor (head and neck). Available at http://www.emedicine.com/radio/topic309.htm (access verified Feb. 26, 2007).

(2.) Harnsberger HR, ed. Diagnostic Imaging: Head and Neck. Salt Lake City: Amirsys; 2004:82-5.

(3.) Weissman JL, Hirsch BE. Imaging of tinnitus: A review. Radiology 2000;216:342-9.

(4.) O'Leary MJ, Shelton C, Giddings NA, et al. Glomus tympanicum tumors: A clinical perspective. Laryngoscope 1991; 101:1038-43.

(5.) Rohit, Jain Y, Caruso A, et al. Glomus tympanicum tumour: An alternative surgical technique. J Laryngol Otol 2003;117:462-6.

From the Department of Radiology, Tulane University Hospital and Clinics, New Orleans.

Troy Hutchins, MD; Enrique Palacios, MD