Acute infectious pseudoaneurism of the carotid bifurcation

Clinical History

An 88-year-old woman presented to the Emergency Department with general malaise, stable vital signs and 5-day-history of a left-sided cervical mass that showed signs of inflammation. Physical examination revealed no other abnormality.

Imaging Findings

We carried out neck ultrasound which showed a 7-cm collection on the left side of the neck with a pulsatile mass in the middle of it.
A double-phase contrast-enhanced 64-MD-CT scan of the neck and chest was performed.
The arterial phase revealed a 7 cm partially thrombosed pseudoaneurysm arising from the left carotid bifurcation, near a calcified atheromatous plaque.
The walls of the pseudoaneurysm were irregular and the thrombus was hyperdense as a sign of recent contained rupture. These findings were embedded in a 9-cm collection that was interpreted as a contained haematoma with signs of infection. Thrombophlebitis of the left internal jugular vein (thrombus, wall enhancement and bubbles) was seen.
No extension of the collection into the thorax was shown.
No significant adenopathy was observed on the CT scan.
Angiography confirmed an aneurysm of the left carotid artery bifurcation.

Discussion

Pseudoaneurysms can be due to a variety of causes including blunt or penetrating trauma, arterial dissection, vasculitides (e.g. Behçet disease) [1], infection or iatrogenic complications after procedures.
Mycotic aneurysms of the extracranial carotid artery are rare and difficult to diagnose.
Their incidence is relatively stable, with approximately 20 cases reported per decade over the past 30 years [2].
The most common aetiology of mycotic pseudoaneurysms is bacteraemia, leading to bacteria colonising arterial wall irregularities via the vasa-vasorum, generally in an atheromatous plaque.
In our case Methillicin Resistant Staphylococcus aureus (MRSA) was isolated both on blood culture and in the excised specimen.
In terms of frequency, the most common microbe found in such cases is Staphylococcus aureus followed by Streptococcus pyogenes when there is a cardiac origin (endocarditis) and Salmonella sp. in cases of extracardiac origin [3].

This type of mycotic pseudoaneurysm is usually found in elderly patients with comorbidities such as in our case.

Possible treatment options in this condition include endovascular repair (stent placement with or without coil embolisation) or surgery (excision of the pseudoaneurysm and bypass with great saphenous vein) [4].
In our patient, due to carotid elongation, endovascular treatment with endoprothesis was impossible. Therefore surgical treatment was performed with excision of the aneurysm, ligation of the external carotid artery and a common-to-internal carotid artery bypass using the greater right saphenous vein.

Differential Diagnosis List

Final Diagnosis

Mycotic pseudoaneurysm of the carotid bifurcation

URL:	https://eurorad.org/case/13434
DOI:	10.1594/EURORAD/CASE.13434
ISSN:	1563-4086