Extracranial internal carotid artery aneurysm

Clinical History

A 77-year-old woman presented with a palpable and pulsatile neck mass, which had visibly grown in the past 6 months. There was a history of hypertension and diabetes mellitus. There were no other signs or symptoms and no previous neck surgery or trauma.

Imaging Findings

CT showed a fusiform mass in the cervical segment of the right internal carotid artery, located 2 cm above the carotid bifurcation. Before iodine administration the mass was isodense compared to the carotid artery lumen, with 5 cm extension and 3.8 cm of maximum axial diameter, compressing and pushing the adjacent structures, with contralateral displacement of the pharynx. The right common carotid artery was also tortuous and kinked and a few atheromatous deposits were found in the carotid bifurcation. After intravenous contrast agent administration, there was a complete and homogeneous enhancement of the mass, confirming the diagnosis of right extracranial carotid artery fusiform aneurysm.

Discussion

Extracranial internal carotid artery aneurysms are rarely seen, and are defined as a localized increase in calibre greater than 50% of the reference measurements (0.55 +/- 0.06 cm in men and 0.49 +/- 0.07 in women) [1]. They can be classified as true or pseudo- aneurysms, depending if the three arterial wall layers (intima, media and adventitia) are present or not, respectively.

True carotid artery aneurysm aetiologies include the following: congenital, infectious, irradiation, fibromuscular dysplasia, and atherosclerosis, the latter being the most common [1, 2, 3, 4]. There is also an overall male prevalence, especially in the atherosclerotic aetiology [2, 3]. The most frequent signs at presentation are neurological manifestations, mainly transient ischaemic attacks, but a palpable neck mass, like in the present case, is also a common presentation [2, 4]. Other reported manifestations of this type of aneurysm are: carotid bruit, cranial nerve dysfunction, pain, dysphagia, dizziness, tinnitus, and pharyngeal mass [2, 4].

There have been several comorbid factors associated with atherosclerotic aneurysms, such as hypertension, coronary artery disease, cardiac arrhythmia, diabetes mellitus, chronic obstructive pulmonary disease, hyperlipidaemia, smoking and hypothyroidism [2]. The case presented here is most probably of atherosclerotic aetiology, due to the fact that there was no history of previous neck surgery, trauma or irradiation, no associated fibromuscular dysplasia signs, the late onset of symptoms, the quick growth, and the associated history of hypertension and diabetes mellitus. Also, the CT findings of atherosclerotic plaques in the carotid bifurcation and the fusiform configuration of the aneurysm favour this aetiology [4].

The diagnosis can be done clinically if there is a pulsatile neck mass, but imaging is necessary to confirm the diagnosis and evaluate the extent and anatomical boundaries of the lesion [4]. Doppler-ultrasound is a good first choice imaging modality, because of its lower cost and absence of radiation. CT examinations may show a fusiform or saccular aneurysm. Peripheral eggshell calcifications may also be seen, being more frequently associated with the fusiform type [4]. Non-contrast-enhanced CT scans may therefore be useful to better visualize peripheral calcifications and atheromatous deposits. After contrast administration, the aneurysms typically show arterial enhancement [4], as observed in the present case.

The potential risks of cerebral ischemia and rupture and the satisfactory long-term results of surgical repair favour a surgical treatment approach, but endovascular procedures are an alternative [1, 2].

Differential Diagnosis List

Final Diagnosis

Extracranial internal carotid artery aneurysm.

URL:	https://www.eurorad.org/case/11350
DOI:	10.1594/EURORAD/CASE.11350
ISSN:	1563-4086