paragangliomas of the head and neck
Paragangliomas of the head and neck are rare, representing <0.5% of all head and neck tumors. They arise in a number of locations along the carotid sheath and middle ear including the carotid bifurcation, vagal ganglia, jugular bulb, and tympanic plexus.
For a general discussion of the pathology of these tumors please refer to the paraganglioma article.
Overall there is a 3:1 female predominance. Two-thirds of cases are diagnosed between the ages of 40 and 60. Approximately 25% are multicentric, and these tend to be familial.
Clinical presentation will depend on location.
When involving the middle ear cavity, the tumor may grow large and extend into the external ear: these may present with pulsatile tinnitus, cranial nerve palsies (typically IX-XI, Vernet syndrome), or conductive hearing loss. Direct otoscopic examination may reveal a retrotympanic vascular mass.
In the neck, the patient may present with a local mass.
Paragangliomas arise from neural crest cells, which can differentiate into cells of either the parasympathetic or sympathetic nervous system. In the head and neck, paragangliomas tend to be innervated by the parasympathetic system and do not secrete catecholamines and are thus termed nonchromaffin paragangliomas .
Multiple paragangliomas (both sporadic and familial subtypes) are commonly associated with mutations of the succinate dehydrogenase subunit genes .
Although often sporadically identified in otherwise normal individuals, paragangaliomas are seen associated with a number of systemic conditions including :
- multiple endocrine neoplasia (MEN)
- neurofibromatosis type 1 (NF1)
- paraganglioma syndrome
- succinate dehydrogenase mutations
- von Hippel-Lindau syndrome (vHL)
They are divided according to location:
- carotid body tumor (or chemodectoma)
- glomus tympanicum tumor
- glomus jugulotympanicum tumor
- glomus jugulare tumor
- glomus vagale tumor
- useful when bone erosion occurs
- a moth-eaten pattern is typical
- T1: may show a “salt and pepper” appearance; salt representing blood products from hemorrhage (uncommon) and pepper representing flow voids due to high vascularity (common)
- T1C+ (Gd): demonstrate rapid wash-in and wash-out (as opposed to the more slow and steady enhancement of a schwannoma)
- intense tumor blush
- the most common feeding vessel is the ascending pharyngeal artery
- high uptake on In labeled octreotide
Treatment and prognosis
Treatment is usually by excision. Preoperative endovascular embolization is often used to reduce tumor vascularity and aid excision. Radiotherapy may be used for palliation of unresectable lesions.
Malignant transformation is not terribly uncommon and has been reported in 16-19% of glomus vagale tumors, in 6% of carotid body tumors, and in 2-4% of glomus tympanicum tumors.
When completely imaged with CT and contrast-enhanced MRI usually little differential is present. During work-up, however, numerous entities should be considered.
In the middle ear/petrous temporal bone consider:
In the jugular and carotid region consider:
- jugular schwannoma
- lymph node metastasis/mass