34 years old female Patient presented to our department with swelling below right side of mandible for two to three months without pain.She had her MRI and digital subtraction angiography of neck done.
On MRI rounded lobulated mass lesion was identified in the right carotid sheath. It appeared hyper to isointense on T2-weighted imaging, isointense on T1- and showed heterogeneous post contrast enhancement and showed typical salt and pepper appearance. Multiple Flow voids were seen within the lesion. It measured approximately 35 x 32 x 40 mm . It was located at the level of carotid bifurcation and caused splaying the right ICA and ECA similar smaller enhancing lesion was identified in the left carotid sheath at the level of the bifurcation, measuring approximately 13 x 12 x 18 mm. Findings were consistent with bilateral carotid body paragangliomas .
Angiographic images showed splaying of right ICA and ECA by a large carotid body tumor. The carotid body tumor had its major supply from occipital artery. Approximately 80% of occipital artery branches were embolised using PVA particles.
A) Carotid body tumors are rare type of extradrenal paragangliomas often called as chemodectomas, glomus jugulare and glomus vagale. 
The carotid body, tumor was first described by von Haller in 1743, .It arises from neural crest tissue within the adventitia of the CCA near its bifurcation. There has been increased incidence of these tumors in people living at high altitudes. Some reports have shown a female predominance with women to men ratio of 5:1. 
B) Patients often present with a syndrome called the carotid sinus syndrome they typically have bradycardia, hypotension and loss of consciousness. Patients with extradrenal paragangliomas may present with signs and symptoms of excessive catecholamine production like skin flushing, weight loss and vomiting. Patients having such symptoms, should undergo vanillyl mandelic acid estimations, adrenaline and noradrenaline assays.
C) Duplex Ultrasound, CT Computed Tomography, MRI ( magnetic resonance imaging), MRA
(magnetic resonance Angiography) and DSA (Digital Subtraction Angiography) have been requested for patients with suspected carotid body tumors. DSA is the gold standard in carotid body tumor for diagnosis and treatment planning..DSA can identify the dominant feeding vessel, thereby allowing for preoperative embolization. On MRI tumors have intermediate signal on T1 and high signal on T2-weighted images and show intense contrast enhancement. Larger tumors have a typical salt-and-pepper appearance which results from the fast-flowing blood pools and large tumor vessels present within these lesion.
Shamblin classification system has been devised and is based on tumor size and difficulty of resection. Group I tumors are small tumors that can be easily dissected away from the vessels. Group II tumors includes medium sized paragangliomas that seem to be closely associated with the vessels, but are separable with careful subadventitial dissection. Group III are those tumors that are large and typically encase the carotid vessels, they require partial or complete vessel resection and replacement.
For carotid body tumors three treatment options have been advocated  Surgical excision, Embolization and radiotherapy. Surgical excision seems to be the best option and the Shamblin grading helps us in assessing degree of difficulty .Because of the close proximity of these tumors to important vessels and nerves( X to XII ) in neck there is increased risk of morbidity and mortality.
E)Carotid body tumors are rare vascular tumors that are diagnosed by imaging and angiography and MRI provide a good road map for tumor evaluation and management.
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Differential Diagnosis List
carotid body tumor
lymph node mass