Paraganglioma of the carotid body: correlation of CEUS and MDCT findings

Clinical History

A 73 year-old man was referred to our department reporting episodes of dizziness and pallor. In his medical history he had arterial hypertension and had been admitted for coronary artery angioplasty and stenting. Vital signs on clinical examination were BP 130/75 mm Hg); neurological examination was without focal deficit.

Imaging Findings

Greyscale ultrasound examination of the carotid vessels detected a hypoechoic, inhomogeneous, well-defined solid mass, with anechoic tubular channels that represented small vessels. The mass was widening the bifurcation and splaying the vessels. Colour Doppler demonstrated significant internal vascularity. The ultrasound investigation was completed after the bolus administration of SonoVue 2.5 ml via an antecubital vein and followed by a 10 ml saline flush. The mass showed early arterial contrast enhancement with peripheral to central contrast filling and a distinct irregular hypervascularisation. The real time enhancement study revealed rapid early arterial uptake of contrast, high peak contrast uptake and rapid washout. Findings were consistent with a carotid body paraganglioma. To confirm the diagnosis, CT angiography was performed which showed splaying of the internal and external carotid arteries. The lesion showed intense enhancement on CT and did not narrow the lumen of the arteries.

Discussion

Background: The carotid body is situated within or outside the adventitia layer of the common carotid artery. It is most frequently sited in the posteromedial wall at the level of bifurcation, and less commonly along either the external carotid artery, or the internal carotid artery. Carotid body paragangliomas are highly vascularized lesions of the parasympathetic nervous system, which derive from the embryonic neural crest cells. Paragangliomas are relatively rare extra-adrenal tumours, originating from the neuroectoderm. They run an indolent course and most frequently are incidental findings. Their distribution in the head and neck follows a distinct chain of location, commonly originating in the carotid body, throughout the path of the vagus nerve, in the middle ear and jugular foramen [1].
Clinical perspective: clinical manifestation, if any, is due to mass effect exerted on neighbouring tissues by the slow growing lesion rather than excess catecholamine production. Due to its indolent course it is prone to late diagnosis and only comes to ones' attention when a gradually enlarging pulsatile neck mass appears [1].
Imaging perspective: gold standard diagnostic imaging procedures include CT angiography, magnetic resonance imaging, and conventional angiography [1]. The aim of this report is to introduce a new ultrasound diagnostic approach using CEUS and evaluating dynamic uptake and washout to characterise the lesion.
Outcome: About 6-10% of carotid body paragangliomas are known to be malignant. For diagnosis of malignant carotid body paragangliomas there are no clear imaging findings to differentiate it from benign lesion. This diagnosis is established by findings of local, regional and distant metastasis. The natural history of these lesions is subtle, allowing them to reach large dimensions and remain asymptomatic. Symptoms are usually caused by compression of nearby structures, resulting in neuropathy of the vagus and hypoglossal nerve, dysphagia and rarely a vascular murmur is present indicating severe carotid artery compression [2-5]. In our case, CT did not reveal any other tumours elsewhere. The patient underwent surgery. The postoperative course was uneventful.
Take home message: dynamic imaging exhibiting an enhancement curve that simulates arterial flow is characteristic of glomus tumours. A worthwhile study might prospectively evaluate the use of dynamic contrast enhanced ultrasound, dynamic magnetic resonance and serial CT images for the characterization of lesions of the carotid space.

Differential Diagnosis List

Final Diagnosis

Paraganglioma of the left carotid body

URL:	https://www.eurorad.org/case/13147
DOI:	10.1594/EURORAD/CASE.13147
ISSN:	1563-4086