eRadiograph Volume 7: Imaging of Oral Cavity | Page 265

Paraganglionoma Paraganglionomas arise from paraganglionic cells (neuroectodermal origin) which secrete catecholamines helping the autonomic nervous system respond to physiologic stresses. These paraganglia are located in the adrenal gland. Extra adrenal location of paraganglia are in the adventitial layer of blood vessels. In the head and neck region these occur in four primary locations – at the carotid bifurcation (carotid body), along the nodose ganglia of the vagus nerve (vagal paraganglioma), in the region of the jugular bulb (glomus jugulare) and in the middle ear along tympanic plexus respectively known as (glomus tympanicum) These tumors are slow growing vascular tumors which are mostly benign – 10% may be malignant 10% may be multicentric, 10% of paraganglinoma are associated with MEN 1/2 Syndrome. Lesions may be synchronous or multicentric. Therefore all potential paraganglioma sites should be screened. On imaging these appear as densely enhancing soft tissue masses. On MRI they are hypointense on T1W1, hyperintense on T2W1 with internal flow voids due to hypervascularity resulting in a salt and pepper appearance. Carotid Body Paraganglionomas: develop from paraganglia cells in the adventia at the carotid bifurcation. These cause splaying of the internal and external carotid arteries. The presence of a lucent halo around the carotid artery indicates the carotid artery is not involved. Sympathetic Chain Paraganglionomas These are very rare tumors arising close to the carotid bifurcation. Since they are located posterior and medial to the carotid artery they displace the carotid artery anteriolaterally as compared to vagal paraganglionomas which displace the carotid artery anteromedially. Unlike vagal Paraganglionomas which do not cause splaying of the carotid arteries, sympathetic Paraganglionomas may splay the carotid arteries similar to a carotid body tumor. It is important preoperatively to differentiate a carotid body tumor from a sympathetic chain Paraganglionomas – because of the functional and cosmetic impact of Horner Syndrome. If the bulk of tumor is medial to the carotid bifurcation this would most likely represent a sympathetic chain ganglionoma. 265 Carotid Space Vagal Paraganglionomas: are rare accounting for less than 5% of all head and neck Paraganglionomas these generally arise high along the extra cranial course of the vagus nerve close to the skull base thus they may be firmly attached to the skull base as well as extend intracranially. Vagal paraganglionomas displace the internal carotid artery anteromedially and do not widen the carotid bifurcation like carotid body tumors do.