CASE 15184 Published on 24.10.2017

Internal carotid artery intraluminal thrombus: demonstration with MDCTA and follow-up with US

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Vasileios Rafailidis, Ioannis Chryssogonidis, Irini Nikolaou, Anna Kalogera-Fountzila

Department of Radiology, AHEPA University General Hospital of Thessaloniki, Greece
Email:billraf@hotmail.com

Patient

66 years, male

Categories

Area of Interest Vascular ; Imaging Technique CT-Angiography, Ultrasound-Spectral Doppler, Ultrasound-Colour Doppler, Ultrasound-Power Doppler

Procedure Diagnostic procedure ; Special Focus Arteriosclerosis ;

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Clinical History

A 66-year-old male patient was referred for a multi-detector computed tomographic angiography (MDCTA) of the carotid system after incidental detection of a highly stenotic plaque on carotid ultrasound (US), performed for screening after detection of femoral artery atherosclerosis causing intermittent claudication. Past medical history was unremarkable except for hypertension.

Imaging Findings

The carotid system MDCTA examination revealed only mild stenosis of the left internal carotid artery. However, a highly stenotic plaque causing near-occlusion was identified in the origin of the right internal carotid artery. The plaque was partially calcified and partially hypodense. A short filling defect situated cranially to the plaque and centrally located within the lumen was also noted, which was completely surrounded by contrast medium (Fig. 1). This appearance, also known as “donut sign” was attributed to the presence of an intraluminal carotid thrombus. The patient was treated with a combination of antiplatelets and anticoagulation. Eight months after the first examination, the patient presented for a follow-up US examination. The right internal carotid artery plaque appeared predominantly echogenic, with a smooth surface and caused severe stenosis (70% diameter reduction). There was no evidence of any intraluminal filling defect on colour or power Doppler technique (Fig. 2).

Discussion

The entity of intraluminal carotid thrombus (ICT) has been recognised as a lesion with increased thromboembolic potential, either being adhered to an underlying ulcerated plaque or free-floating.[1-5] ICT is rare as identified in only 0.62% of endarterectomies, in 0.9% of US examinations and is symptomatic in 87.5-92% of cases. [3, 6] Patients with ICT are more frequently men and hypercoagulable in half of the cases. ICT affects the internal carotid artery in 75% of the cases, but cases affecting the common carotid have also been reported. [6, 7]
US visualises ICT in 62.5% of the cases, whereas DSA is up to 100% sensitive. [3] ICT appears on US attached to the arterial wall and surrounded by blood flow signals. [8] MDCTA visualises ICT as a filling defect within the contrast agent column, which is completely surrounded by the contrast agent for more than one axial source image. This circular appearance of contrast medium has led to the term “donut sign”, seen in 3.1% of MDCTA of patients with symptomatic carotid disease. [4] The “donut sign” has been reported to always affect the symptomatic side in stroke patients and has been associated with ulcerated atherosclerotic plaque, dissection, post-endarterectomy imaging, the presence of thrombus within the left ventricle and aneurysms. [4, 2, 6, 8, 5] Another MDCTA sign helping to differentiate ICT from a mere ulcerated carotid plaque is the “finger sign”, representing the cranial extension of the filling defect on sagittal or coronal images, with an extension length of more than 3.8 mm yielding a 0.86 area under the curve for the detection of ICT instead of ulcerated plaque. [1, 9] Shape analysis based on MDCTA has been recently used for differentiating ICT from atherosclerotic plaque. It was concluded that the use of shape characteristic achieves 87.5% sensitivity and 71.4% specificity in that respect. ICT was found to have lower convexity, in keeping with the subjective “finger sign” attributed to this entity. Moreover, plaques had more cavities on their surface, compared to ICT. [9]
MDCTA or MRA follow-up studies of patients with ICT being medically treated have shown thrombus resolution or reduction in luminal stenosis. [4] Thrombus resolution after medical treatment has been reported and even used by some as a criterion to establish the diagnosis of ICT compared to atherosclerotic plaques. Rarely, a medically treated ICT may persist or progress to occlusion. [9, 10, 6, 8, 11, 5] ICT treatment remains controversial, including either surgery with endarterectomy or stenting or medical treatment. [10, 4, 3, 6]

Differential Diagnosis List

Internal carotid artery intraluminal thrombus resolving after medical treatment.

ICA intraluminal thrombus

ICA pre-occlusive atherosclerotic plaque

ICA ulcerated atherosclerotic plaque (particularly type 4 ulcer)

ICA occlusion

ICA dissection

Final Diagnosis

Internal carotid artery intraluminal thrombus resolving after medical treatment.

References

[1] Jaberi A, Lum C, Stefanski P, Thornhill R, Iancu D, Petrcich W, Momoli F, Torres C, Dowlatshahi D (2014) Computed tomography angiography intraluminal filling defect is predictive of internal carotid artery free-floating thrombus. Neuroradiology 56 (1):15-23 (PMID: 24212333)

[2] Sallustio F, Di Legge S, Marziali S, Ippoliti A, Stanzione P (2011) Floating carotid thrombus treated by intravenous heparin and endarterectomy. J Vasc Surg 53 (2):489-491 (PMID: 20934839)

[3] Ferrero E, Ferri M, Viazzo A, Labate C, Pecchio A, Berardi G, Piazza S, Cumbo P, Nessi F (2011) Free-floating thrombus in the internal carotid artery: diagnosis and treatment of 16 cases in a single center. Ann Vasc Surg 25 (6):805-812 (PMID: 21621967)

[4] Menon BK, Singh J, Al-Khataami A, Demchuk AM, Goyal M (2010) The donut sign on CT angiography: an indicator of reversible intraluminal carotid thrombus?. Neuroradiology 52 (11):1055-1056 (PMID: 20625710)

[5] Jaberi A, Lum C, Stefanski P, Thornhill RE, Dowlatshahi D (2012) Computed tomography angiography evaluation of internal carotid artery free-floating thrombus—single-center diagnosis, false-positives, and follow-up. Emerg Radiol 19 (4):359-362 (PMID: 22465998)

[6] Bhatti AF, Leon LR, Jr., Labropoulos N, Rubinas TL, Rodriguez H, Kalman PG, Schneck M, Psalms SB, Biller J (2007) Free-floating thrombus of the carotid artery: literature review and case reports. J Vasc Surg 45 (1):199-205 (PMID: 17210411)

[7] Kim JG Lee SJ (2015) Two Cases with Free-Floating Thrombus in the Common Carotid Artery. J Cardiol Clin Res 3 (2):1047

[8] Chua HC, Lim T, Teo BC, Phua Z, Eng J (2012) Free-floating thrombus of the carotid artery detected on carotid ultrasound in patients with cerebral infarcts: a 10-year study. Ann Acad Med Singapore 41 (9):420-424 (PMID: 23052437)

[9] Thornhill RE, Lum C, Jaberi A, Stefanski P, Torres CH, Momoli F, Petrcich W, Dowlatshahi D (2014) Can shape analysis differentiate free-floating internal carotid artery thrombus from atherosclerotic plaque in patients evaluated with CTA for stroke or transient ischemic attack?. Acad Radiol 21 (3):345-354 (PMID: 24507422)

[10] Pelz DM, Buchan A, Fox AJ, Barnett HJ, Vinuela F (1986) Intraluminal thrombus of the internal carotid arteries: angiographic demonstration of resolution with anticoagulant therapy alone. Radiology 160 (2):369-373 (PMID: 3726115)

[11] Graham R, Blaszczynski M (2013) pontaneous free floating carotid artery thrombosis. BMJ Case Rep 2013:bcr2013008710 (PMID: 23749854)

Case information

URL:	https://eurorad.org/case/15184
DOI:	10.1594/EURORAD/CASE.15184
ISSN:	1563-4086

License

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Figure 1

First MDCTA examination of the carotid system

Sagittal reformatted MDCTA image showing the right internal carotid artery atherosclerotic plaque causing near-occlusion. Note is made of a short round filling defect cranially to the plaque which can be attributed to intraluminal carotid thrombus.

Thick maximum intensity projection (MIP) sagittal image better visualising the pre-occlusive lesion and the down-stream filling defect.

Axial MDCTA image showing the filling defect being completely surrounded by contrast medium, in keeping with the “donut sign” (arrowhead).

Second contiguous axial MDCTA image showing the filling defect being completely surrounded by contrast medium, in keeping with the “donut sign” (arrowhead).

Volume Rendering (VR) technique image showing the near-occlusive plaque and the intraluminal filling defect cranially to the lesion (arrowhead).

Figure 2

Follow-up carotid US

Pulse-wave Doppler image showing the increase in peak systolic velocity at the point of maximum stenosis, within a severely stenotic lumen.

Colour Doppler image showing a predominantly echogenic plaque with smooth surface and severe luminal stenosis. The internal carotid artery lumen down-stream is normally filled with blood flow signals, showing no filling defect.