Carotid Body Paraganglioma

Axial CECT showing CCA proximal to its bifurcation.

A 24-year-old female presented with painless, slowly enlarging mass lesion at the angle of mandible on right side of 14 months duration. There was no history of dysphagia/ hoarseness/ headache. She did not have symptoms or signs of Horner’s syndrome or catecholamine excess. Her past medical history was insignificant and there was no family history of similar complaints.

The patient was moderately built and her general physical examination was unremarkable except for pallor. Her vitals were within normal limits. On local examination, there was an ovoid, firm, non-tender, pulsatile mass lesion, 3 x 1.8 cm size, located along the anterior border of sternomastoid at the level of hyoid bone on right side. The swelling was freely movable laterally than vertically (Fontaine’s sign positive). There was no audible bruit or palpable lymph nodes.
Routine lab investigations were normal.

Axial CECT showing CCA proximal to its bifurcation Axial CECT revealing the paraganglioma sitting at carotid bifurcation

Axial CECT showing completely encased ECA and partially encased ICA. Two intersecting lines are drawn between the centre of ICA and the points of contact of the circumference of the vessel with the edges of the tumor to obtain the angle.

Oblique sagittal MPR image showing the tumor at Y of carotid bifurcation Sagittal MIP image demonstrating the relation of tumor to vessels.

Oblique sagittal MPR image showing the tumor at Y of carotid bifurcation Sagittal MIP image demonstrating the relation of tumor to vessels.

Coronal MIP image

CECT was done which showed a lobulated soft tissue mass located at carotid bifurcation extending cephalad and measuring 3.9(craniocaudal) x 1.9(transverse) x 2.2(anteroposterior) cm. There was intense blush on administering iv contrast and splaying of internal and external carotid arteries (Lyre sign) was noted which suggested carotid body paraganglioma. The lesion was seen to completely encase ECA and had 1690 circumferential contact with ICA classifying it as Shamblin type I tumor.

She underwent surgery and histopathology confirmed the lesion as paraganglioma. Her post-operative period was uneventful.

Discussion: Paragangliomas are slow growing hypervascular tumors arising from neural crest derivatives. They occur at multiple levels in the head and neck including the carotid bifurcation, along the nodose ganglia of vagus nerve (glomus vagale tumors), in the jugular bulb region (glomus jugulare) and in middle ear cavity (glomus tympanicum).

Carotid body paraganglioma is the most common location for head and neck paragangliomas (60 percent to 67 percent) typically occurring in the fourth and fifth decade with female predilection. They usually present as painless pulsatile mass in the angle of mandible, with about 20 percent having symptoms of vagal or hypoglossal neuropathy. They rarely secrete catecholamines. A small number are familial and multicentric. So, the radiologist must always look for the 2nd lesion in jugular foramen or nasopharyngeal carotid space.

CT and MRI are usually required to assess the extent of lesion and to rule out other masses mimicking these tumors. On Non-contrast CT, the density is similar to neck muscles. On CECT, the characteristic location at carotid bifurcation and the splaying of vessels and its avid enhancement aid in diagnosis. On MR, they have intermediate signal intensity on all sequences. Large tumors (>2 cm) give the ‘salt and pepper appearance’ due to serpentine flow void of small vessels and subacute hemorrhages.

Angiography is the most specific diagnostic technique and features include moderate enlargement of feeding arteries (ascending pharyngeal artery is the main feeder), early intense parenchymal blush, and rapid venous filling.

The addition of diffusion weighted MRI and calculation of ADC values to routine MR protocols is valuable as it has been observed that depending on the tumor size, the DWI and ADC show a high signal in paragangliomas.

The preferred treatment for carotid body tumors is surgery. Shamblin classified them into three types based on operative notes and gross specimen examination depending on the relationship of the tumor with carotid vessels. Because the relation of the tumor to the ICA is most critical for surgical planning, the circumferential degree of contact of the tumor with the ICA is used to classify the tumor radiologically into 3 types in an attempt to predict the Shamblin group of the tumors: type I- less than or equal to 180°; type II- greater than 180° and less than 270°; and type III- greater than or equal to 270°.

Differential diagnosis: Neurogenic tumors are the most common carotid space lesions. A tumor arising from vagus nerve displaces ICA/CCA anteromedially and IJV posterolaterally and does not splay ICA – ECA at carotid bifurcation. Vagal schwannoma present as a fusiform enhancing carotid space mass in CT/MR without flow voids on MR. Intramural cystic changes may be present. Vagal neurofibromas have characteristic low density (near water) on CT due to lipid rich Schwann and fat cells scattered in the tumor and there is no appreciable contrast enhancement. On MRI, an area of relatively hypointense central signal with peripheral hyperintense signal – ‘target sign’ might be seen on T2W sequences.

Glomus jugular tumor are centered more rostrally than carotid body tumors, approximately 2 cm below the skull base.

Vascular nodal metastases from RCC, papillary thyroid carcinoma show flow voids on MR but do not cause displacement of vessels.

Parthasarathy Ganesan, MD, GTB Hospital, Delhi, India

References:

1. Diagnostic Imaging- Head & Neck, Harnsberger, 1st edition, 2004.
2. S. Arya, V. Rao, S. Juvekar, A.K. Dcruz. Carotid Body Tumors: Objective Criteria to Predict the Shamblin Group on MR Imaging. AJNR 2008 29:1349-1354.
3. Nader M.A et al. Carotid Body Paraganglioma Management and Outcome. European Journal of Scientific Research 2009, 37; 4:567-574.
4. Aschenbach R, Basche S et al. Diffusion weighted imaging and ADC mapping of head and neck paragangliomas. Clin Neuroradiol 2009;19:215-9.