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Published on : Aug 02, 2021 | Views : 2013 | Downloads : 1

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Paragangliomas of the Head and Neck
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INTRODUCTION The extraadrenal neuroendocrine system com- prises an integrated and complex system of dis- persed tissue throughout the body that possesses unique regulatory functions A single collection of this tissue is called a paraganglion (coined by Kohn in 1903), and the entire chain of tissue con- stitutes the paraganglia
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Paraganglia in the head and neck migrate along a branchiomeric (of the branchial mesoderm) distribution, whereas those in the chest, abdomen, and pelvis follow the path of parasympathetic nerve fibers along the perivertebral-periaortic axis.
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Within the head and neck, the four most common sites are the carotid body at the common carotid artery (CCA) bifurcation, the jugular foramen, along the vagus nerve, and within the middle ear.
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ORIGIN, LOCATION, AND SPREAD Paragangliomas arise in the head and neck at four primary sites: the carotid body, the jugular foramen, along the path of the vagus nerve, and the middle ear. Less common sites include the sella turcica , pineal gland, cavernous sinus, larynx, orbit, thyroid gland, nasopharynx, mandible, soft palate, face, and cheek
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The carotid body is situated within or outside the adventitial layer of each CCA at the level of their bifurcation. A carotid body paraganglioma arises within the carotid body and characteristically splays the bifurcation of the CCA. As the tumor enlarges, it encases but does not narrow the caliber of the ECA and ICA.
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When a paraganglioma originates from the inferior ganglion, it appears spindle shaped, compresses the internal jugular vein (IJV), displaces the carotid vessels anteromedially, and typically pushes the lateral pharyngeal wall medially . There is typically minimal destruction of the skull base.
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When a paraganglioma originates from the superior ganglion, the tumor appears “dumbbell shaped,” extending superiorly into the posterior fossa and inferiorly into the infratemporal space . a vagal paraganglioma can grow medially to involve the arch of the atlas encase and displace the ICA , extend superiorly into the posterior fossa with compression of the brain stem , or extend laterally to involve the middle ear structures
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The classic manifestation of a carotid body tumor is a non tender, enlarging lateral neck mass which is mobile, pulsatile, and associated with a bruit. The jugulare and tympanicum tumors commonly cause pulsatile tinnitus and hearing loss and may cause cranial nerve compression. Vagal paraganglioms are the least common and present as a painless neck mass which may result in dysphagia and hoarseness
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Glomus Tympanicum Key Points Most common tumor of the middle ear. Mass arising from the middle ear and NOT involving the jugular foramen. Benign tumor arising from glomus bodies found along the inferior tympanic nerve (Jacobson nerve), a branch of the glossopharyngeal nerve on the cochlear promontory. Commonly presents in a middle aged (40-60 years of age) female with pulsatile tinnitus (90%), conductive hearing loss (50%), and facial nerve paralysis (5%) with a retrotympanic vascular mass. Treatment is tympanotomy for smaller lesions; mastoidectomy for larger lesions.
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Imaging Characteristics CT demonstrates a round mass with flat base on the cochlear promontory projecting into the mesotympanum. Larger lesion may resemble “New Jersey” on coronal image when they fill middle ear cavity. Focal enhancing mass on cochlear promontory.
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Carotid Body Paraganglioma Key Points Most common location for head and neck paragangliomas (60-67%) Benign vascular tumor arising in glomus bodies in the carotid body found between ECA and ICA at carotid bifurcation. Most common in the 4th and 5th decade. Pulsatile, painless mass at the angle of the mandible. Catecholamine-secreting carotid body paraganglioma is rare. Treatment is surgical removal. Multifocal paragangliomas: may occur with glomus jugulare or vagale paragangliomas. Radiologist must look for multiplicity. Look for a 2nd lesion
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Imaging Characteristics Vascular mass splaying the ICA posterolaterally and ECA anteromedially extending from the carotid artery bifurcation cephalad. Intense enhancement. Larger high velocity flow voids still visualized. T1WI Salt and pepper appearance: “Salt” appearance secondary to subacute hemorrhage. “Pepper” appearance due to flow voids. T2WI hyperintense with flow voids. Angiography: Prolonged, intense tumor blush between ICA and ECA. Main feeding branch is ascending pharyngeal artery, a branch of the ECA.
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Glomus Vagale Key Points Rarest of major head and neck paragangliomas (2.5%). Benign vascular tumor from glomus bodies associated with nodose ganglia of vagus nerve. Painless, pulsatile posterolateral pharyngeal mass. Vagal neuropathy, vocal cord paralysis with hoarseness, horner syndrome possible.
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Imaging Characteristics Avidly-enhancing ovoid carotid space mass. Anteromedial displacement of ICA and posteriolateral displacment of IJV. No widening of the carotid bifurcation. MRI imaging findings similar to carotid body paraganglioma.
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Glomus Jugulotympanicum Key Points Glomus Jugulotympanicum describes a paraganglioma involving both the jugular foramen and middle ear cavity. Jugular foramen mass extends superiolaterally into the floor of the middle ear cavity. Tumor spread vector is superiolateral.
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Imaging Characteristics Bone CT demonstrates mass in the jugular foramen with “permeative-destructive” changes along the superolateral margin of the jugular foramen. Mass invading the adjacent middle ear. MRI imaging findings similar to glomus jugulare.
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Glomus Jugulare Key Points Considered 2nd most common head and neck paraganglioma. Mass arising from the jugular foramen and NOT involving the middle ear. Arising in the jugular foramen from the tympanic branch (Jacobson nerve) of the glossopharyngeal nerve or the auricular branch (Arnold nerve) of the vagus nerve. Commonly presents in a middle aged (40-60 years of age) female with pulsatile tinnitus and retrotympanic vascular mass. Cranial neuropathy involving 9, 10 and 11th cranial nerves.
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Imaging Characteristics Bone CT demonstrates a mass in the jugular foramen with “permeative-destructive” changes of adjacent bone. T1WI greater than 2 cm demonstrates characteristic “salt and pepper” appearance. T2WI shows mixed hyperintense mass with flow voids. Intense enhancement.
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Summary Carotid body paraganglioma and glomus jugulare make up 80% of paragangliomas of the head and neck. MRI classic appearance of paragangliomas is “salt and pepper”. “Salt” due to hemorrhage (rare) and “pepper” due to flow voids. Paragangliomas are hypervascular masses therefore avidly enhancing. Carotid body mass splays the ICA posteriolaterally and the ECA anteromedially at the carotid bifurcation.
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Glomus vagale displaces the ICA anteromedially and the IJV posterolaterally. Glomus tympanicum classically found at the cochlear promontory arising from Jacobson nerve. Glomus jugulare arises from Jacobson nerve or Arnold nerve within the jugular foramen and not involving the middle ear.
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Thank you