Teaching Case

An asymptomatic 70-year-old woman who has undergone a cervical computed tomography (CT) as a control of a parotid pleomorphic adenoma, was accidentally found a hypervascular mass at left carotid bifurcation. On examination, mobile swelling was noted on left side, with horizontal mobility and restricted vertical mobility (fontaine sign).

CT angiography demonstrated a well-circumscribed soft tissue mass, that showed heterogeneously intensely enhancing after intravenous contrast administration, measuring 15 x 21 x 18 mm. (figure 1, 2, 3) It was located in the left carotid artery bifurcation, causing splaying of the internal and external carotid arteries (Lyre sign). It was established the diagnosis of a carotid body paraganglioma and based on imaging findings was classified as a Shamblin type I. (figure 1b).

Paragangliomas (PGLs) are rare tumours that arise from paraganglion cells, which form the basis of the extra-adrenal neuroendocrine system. It can have several locations, such as in the head and neck, where they usually appear at the carotid bifurcation in close association with the vagus nerve, middle ear or along with the jugular bulb, which are typically from parasympathetic and non-functioning paraganglia.[1] PGLs of head and neck are bilateral and multifocal in 25% of the cases, typically in the hereditary forms.[1] The majority are benign and only locally invasive, with metastasis in less than 5%.[2]

Carotid body paraganglioma (CBP) often remain clinically silent before presenting as a painless, slowly enlarging mass in the lateral neck.[3, 4] Characteristically they can be moved horizontally and not vertically, a finding known as a positive Fontaine’s sign.[3]

Ultrasound is frequently the first imaging step for CBP, that usually appears as a solid, well-defined, hypoechoic mass with a splaying of the carotid bifurcation and separation of the internal and external carotid arteries and hypervascular on the colour Doppler.[5]

CT and magnetic resonance (MR) angiography form the mainstay of diagnosis of carotid body tumour, which shows a mass at the carotid artery bifurcation that causes splaying of the internal and external carotid arteries (Lyre sign). In addition, they are excellent methods for demonstrating your relationship to adjacent structures, crucial for it staging into the appropriate Shamblin classification, which is an important predictor of neurovascular morbidity.[8] It typically presents as an avidly enhancing soft-tissue mass, related to the presence of many arterio-venous shunts. Larger CBP has the characteristic “salt and pepper” appearance on T1-weighted MR imaging due to slowly flowing blood products and vascular flow voids.[7, 8]

Molecular imaging is often required to stage and monitor treatment response of PGLs, providing high specificity and sensitivity for the detection of PGLs, as well as the additional lesions, which is important for surgical planning.[9] Recently Ga-68 DOTATATE has been used and has shown superior tumour contrast when compared to FDG PET/CT. [10]

Treatment depends on several factors, including the location and extent of the tumour, patient age and comorbidities.

The treatment of choice is surgical resection, the only with curative potential, however, due to the potential serious vascular and neurological complications it is not always used. The endovascular preoperative embolization is often used due to the highly vascular nature of PGLs. Polyvinyl alcohol (PVA) particles are commonly used, but other agents are available, such as alcohol conjugates, liquid embolics (glue) and gel foam. Various studies have been demonstrated that this procedure is very safe and efficacious that may reduce intra-operative bleeding, operative times and associated morbidity. [11, 12]

Other treatment options include radiotherapy, particularly used in patients at higher surgical risk or with advanced/unresectable disease, and stereotactic radiosurgery, which role and indications are still in debate. Both are associated a high likelihood of local control and improvement of the symptoms related to the tumour with promising results, paving the way to reconsider their role as alternative treatments to surgery as a primary treatment option for PGLs. [13-16]

Surgical resection was proposed to this patient.

Take-Home Message / Teaching Points

• CT angiography is an excellent imaging technique to establish the diagnosis.
• Surgical excision is the treatment of choice and the only potentially curative.
• Endovascular preoperative embolization is often used and it is associated with a reduction in hemorrhage and comorbidities associated with surgery.
• Other treatment options include radiotherapy and stereotactic radiosurgery.