Internal Carotid Artery Aneurysms Demonstrated With Computed Tomography Angiography,Ultrasound,and Angiography: Case Series

Abstract

Extracranial carotid artery aneurysms (ECAAs) are rare clinical findings, representing less than 1% of all arterial aneurysms. While often asymptomatic, they pose significant risks of cerebrovascular accidents, nerve compression, or fatal hemorrhage if left untreated. Effective diagnosis and management of internal carotid artery (ICA) aneurysms rely on a multi-modal imaging approach. This article explores the diagnostic pathways and management of ICA aneurysms through a case series. Two clinical examples of ICA aneurysms are explored with carotid duplex ultrasound with color Doppler and spectral analysis, as well as multi-slice computed tomography angiography (CTA) with 3-dimensional reformations. The first case demonstrates the benefits of multi-modality correlation, and the second case highlights both the initial detection of the pathology and post-surgical follow-up.

Introduction

Extracranial carotid artery aneurysms (ECAAs) are an uncommon pathology, accounting for less than 1% of all arterial aneurysms.^1,2 They comprise approximately 0.4% to 1% of arterial aneurysms overall and up to 4% of peripheral arterial aneurysms.^3,4 Extracranial carotid artery aneurysms are most often defined as a dilation of the common carotid artery (CCA) or internal carotid artery (ICA) in which the diameter is greater than 150% of the diameter of a normal or uninvolved segment of the CCA or ICA. ⁵ While any segment of the carotid arteries may be involved, the ICA is the most common site for ECAAs. ⁴

Extracranial carotid artery aneurysms may be classified as true aneurysms or false aneurysms depending on their etiology. ⁶ A pseudoaneurysm, or false aneurysm, is a vascular mass that forms when a perforation in the arterial wall allows blood to escape from the vessel, but the blood remains contained by an adjacent hematoma. ⁷ Conversely, a true aneurysm occurs when the arterial wall remains intact but becomes stretched or dilated. ⁷ Some pseudoaneurysms contain large regions of thrombus, only demonstrating a small amount of blood flow. While some lesions may show larger areas of swirling blood flow with small amounts of thrombus. ⁷ The swirling characteristics of the color flow Doppler patterns seen in pseudoaneurysms may occasionally be present in true aneurysms, making the diagnosis between a true or false aneurysm equivocal.

The causes of ECAAs may include atherosclerosis, fibromuscular dysplasia, trauma, infection (eg, syphilis), radiation therapy, spontaneous dissection, Ehlers-Danlos syndrome, Marfan’s syndrome, and medial degeneration, or they may stem from an iatrogenic origin.^1-3,5-7 It is also suspected, though there is no direct evidence, that kinking and coiling of the carotid arteries may lead to ECAAs. ⁷ Atherosclerotic aneurysms are usually found in elderly patients, and are fusiform, mostly involving the bifurcation region. ⁸

Extracranial carotid artery aneurysms are generally asymptomatic and may present as a pulsatile neck mass. ¹ Symptomatic cases can manifest with dysphagia or hoarseness due to nerve compression, as well as transient ischemic attack (TIA), or minor stroke secondary to embolization from intra-aneurysmal thrombus.^1,2,6 These symptoms may affect the patient’s quality of life. ⁶ If left untreated, ECAAs may lead to dissection, hemorrhage due to rupture, cerebrovascular accidents, and, in some cases, they may become fatal.^1,6,9 However, the development of rupture of ECAAs is considered rare. ²

Anticoagulation and antiplatelet drug therapies are included in the list of conservative, non-surgical medical treatments. ¹ Historically, the primary method of treatment was open surgery. However, in more recent cases, the preferred method is endovascular treatment, which has diminished post-operative complications and mortality. ³

Two cases are presented below that demonstrate examples of ECAAs. In Case 1, a patient underwent carotid duplex ultrasound as the first diagnostic examination to rule out cerebrovascular disease. After suspecting an ECAA using carotid duplex ultrasound, a computed tomography (CT) was ordered to confirm its diagnosis. In Case 2, carotid duplex ultrasound, accompanied by CT and X-ray, was used as a follow-up diagnostic imaging examination to demonstrate patency and normal arterial flow after an initial diagnosis of ECAA using CT, followed by endovascular stenting and coiling of the aneurysm.

Case Reports

Case 1

Radiologic Reports

A 74-year-old male patient presented to his primary care physician with discomfort and a palpable, pulsatile lump in the left neck. The patient’s medical history included prostate cancer, a history of deep vein thrombosis, and pulmonary embolism for which the patient had taken Xarelto, chronic venous insufficiency, nephrolithiasis, hypertension, and an abdominal aortic aneurysm (AAA) with a history of endoscopic AAA repair. A carotid duplex ultrasound, utilizing color Doppler and spectral analysis of the bilateral carotid arteries, was performed. A General Electric LOGIQ E9 (GE Healthcare, Wauwatosa, Wisconsin) was used with a 9L linear array transducer. Both common carotid arteries (CCAs) appeared free of stenosis. Both carotid bulbs demonstrated plaque that did not appear to be flow-limiting. The peak systolic velocity and internal carotid artery (ICA)/CCA ratio were within normal limits. Antegrade flow was identified in both vertebral arteries. A saccular vascular structure connecting to the left ICA (Figure 1) was identified during the examination, measuring approximately 1.9 × 1.4 cm. The color Doppler demonstrated a swirling flow pattern within the outpouching sac connecting to the ICA (Figure 2), suggestive of an ICA aneurysm. A computed tomography angiography (CTA) of the carotid arteries was recommended for correlation of the ICA aneurysm.

Figure 1.

Sagittal grayscale carotid duplex ultrasound image demonstrating the bulb region of the left carotid artery with a saccular outpouching (arrow) that communicates with the left internal carotid artery (ICA).

Figure 2.

Color Doppler image that demonstrates swirling arterial flow within the saccular outpouching (arrow) that communicates with the left ICA.

A CT angiogram of the carotid arteries was performed using a multi-slice CT scanner from the level of the aortic arch to the level of the ICA bifurcation. The study was obtained during the dynamic injection of intravenous (IV) contrast. The 3-dimensional reformatted images were reviewed. The milliamperage (mA) and kilovolt peak (kVp) were adjusted according to the patient’s size. The aortic arch appeared unremarkable. Both CCAs demonstrated opacification without significant stenosis. A dominant left vertebral artery was noted. There was a calcified atherosclerotic plaque of the left carotid bulb extending to the left ICA. There was an outpouching of the most proximal left ICA (Figure 3) measuring approximately 1.4 × 1.3 cm with a proximal left ICA aneurysm. Calcification of the right carotid bulb was noted consistent with atherosclerotic changes. No significant stenosis of the right ICA was noted. No follow-up diagnostic imaging or surgical report was available at the time of this case review.

Figure 3.

Coronal head computed tomography (CT) angiogram that demonstrates a saccular outpouching (arrow) that communicates with the left internal carotid artery.

Case 2

Pre-surgical Radiologic Reports

A 79-year-old female presented to her primary care physician with a palpable pulsatile mass in the right neck. A CT angiogram of the carotid arteries was performed using a multi-slice CT scanner from the level of the aortic arch to the level of the ICA bifurcation. The study was obtained during the dynamic injection of IV contrast. Serial and axial images of the neck were obtained during the administration of IV contrast. Reconstructions were performed in sagittal and coronal planes. There was no stenosis along the course of the vertebral arteries. The right vertebral artery was dominant. No stenosis was noted at the carotid bifurcations or along the course of the ICAs. There was no evidence of arterial dissection. At the right CCA bifurcation, there was a large saccular aneurysm (Figure 4A, B) measuring 1.8 × 1.5 cm in an axial dimension by 2.2 cm in a craniocaudal dimension. There was mild atherosclerotic calcification at the periphery of the aneurysm. When measured at the same location, this was unchanged. The aneurysm involved the origins of the right ICA and ECA.

Figure 4.

(A) Coronal head CT angiogram that demonstrates a large saccular aneurysm (arrow) near the right CCA. (B) Sagittal head CT angiogram that demonstrates a large saccular aneurysm (arrow) near the right CCA.

Surgical and Intraprocedural Radiologic Reports

The patient had a medical history of significant anxiety and prediabetes. The patient’s medication included oral use of Plavix (clopidogrel), 1 tablet daily; oral use of low-dose (81 mg) aspirin, 1 tablet daily; and 1 daily tablet of multi-vitamin, vitamin B, and vitamin D. The patient denied smoking and illicit drug use. The patient reported drinking wine 1 to 2 times per month. Vital signs during the patient’s latest physical examination demonstrated a temperature of 98.4, heart rate of 79, and blood pressure of 143/91. The patient’s weight was 184 pounds with a height of 65 inches.

Informed consent was obtained after discussing the risks and benefits of the procedure with the patient and the patient’s daughter. The patient was supine on the examination table. The right neck was prepped and draped according to surgical fashion. The left groin was prepped and draped in standard sterile fashion. A puncture was made in the left common femoral vein. This was performed under ultrasound guidance using the micro-puncture needle, and then an 8-French Enroute sheath was advanced.

Angiography was performed, which demonstrated a large aneurysm at the carotid bifurcation with significant contrast filling (Figure 5). After reversal of flow, the interventional team was able to catheterize the ECA successfully and the wire and catheter were left in place. They were able to place a wire in the ICA successfully (Figure 6A). They then inserted a 7 mm × 40 mm and 7 mm × 30 mm Enroute stent in that location (Figure 6B) and performed coil embolization using multiple packing coils and Penumbra in the aneurysm. Follow-up angiography showed some filling of the inferior portion of the aneurysm and good flow of contrast through the ICA (Figure 7A). It was decided to place a 7 mm × 25 mm Viabahn stent graft more proximally to help seal the aneurysm further. Follow-up angiography showed good flow through the ICA system (Figure 7B). It showed some filling but less within the aneurysm. Surgical closure was performed after removal of the catheters and wires at the right neck and hemostasis by manual compression at the left groin. The patient tolerated the procedure well. There were no immediate complications.

Figure 5.

Angiogram demonstrates a large aneurysm at the carotid bifurcation that shows significant contrast filling (arrow).

Figure 6.

(A) Angiogram demonstrates the placement of guidewire (arrows) through the right carotid bulb that continues into the internal carotid artery. (B) Angiogram demonstrates the placement of an Enroute stent (arrow) through the right internal carotid artery.

Figure 7.

(A) Intraprocedural angiogram demonstrates some filling of the inferior portion of the aneurysm and good flow of contrast through the internal carotid artery. The coils can also be visualized in the image (arrow). (B) Post-procedural radiograph demonstrates placement of the Viabahn stent graft and coiling (arrow).

Post-surgical Radiologic Reports

A post-surgical CT angiogram of the carotid arteries was performed using a multi-slice CT scanner from the level of the aortic arch to the level of the ICA bifurcation. The images were obtained during the dynamic injection of IV contrast. The 3-dimensional reformatted images were reviewed. The milliamperage (mA) and kilovolt peak (kVp) were adjusted according to the patient’s size. The study was ordered as a follow-up to the pre-surgical CTA. There was no stenosis of the vessels arising from the aortic arch. There was no stenosis along the course of the vertebral arteries. The right vertebral artery remained dominant. The left vertebral artery arose from the aortic arch. The previously seen right carotid bifurcation aneurysm had been treated with coils and vascular stents. A vascular stent was noted extending from the right carotid bulb to the proximal right ICA, which appeared patent (Figure 8A, B). Intracranial portions of both ICAs, vertebral and basilar arteries, were patent. The proximal portions of the anterior, middle, and posterior cerebral arteries were patent without significant stenosis. The A1 segment of the right anterior cerebral artery was not visualized consistent with a normal variant.

Figure 8.

(A) Post-procedural coronal head CT angiogram showing placement of the Viabahn stent graft and coiling (arrow). (B) Post-procedural sagittal head CT angiogram showing placement of the Viabahn stent graft (arrow) and coiling.

The color Doppler and spectral analysis of the carotid arteries bilaterally were performed to compliment the results of the CT angiogram. A General Electric LOGIQ E9 (GE Healthcare) was used with a 9L linear array transducer. Both carotid bulbs demonstrated atherosclerotic plaque, which did not appear to be flow-limiting. The peak systolic velocity and ICA/CCA ratio were within normal limits. Antegrade flow was noted in both vertebral arteries. It was stated that an echogenic pattern and echogenic interrupted echoes adjacent to the right ICA represented coils and vascular stents (Figure 9A, B).

Figure 9.

(A) Post-procedural sagittal color Doppler image that demonstrates coiling (arrow) where the saccular aneurysm used to fill with contrast demonstrated on prior angiograms. (B) Post-procedural transverse color Doppler image that demonstrates patent arterial flow through the ICA stent (arrow).

Discussion

Carotid duplex ultrasound is the preferred initial diagnostic modality for ECAAs. Carotid duplex ultrasound is a noninvasive modality that provides an accurate assessment of stenosis that can be considered for initial diagnosis and follow-up after surgical or endovascular treatment. While most aneurysms can be identified using ultrasound, CTA, and magnetic resonance angiography (MRA) are complementary modalities used to confirm the diagnosis, evaluate disease extent, and guide treatment planning. ¹⁰ Digital subtraction angiography (DSA) provides the most accurate characterization of carotid angioarchitecture and aneurysm flow. ¹¹

Carotid duplex ultrasonography is a very operator-dependent modality. Therefore, it is crucial that sonographers understand proper scanning techniques when imaging the carotid arteries. For example, when using a transverse scanning plane, clear visualization of the lumen-intima interface indicates the plane is perpendicular to the vessel axis. ⁷ This lumina-intima interface is best visualized in a sagittal plane when the image plane passes through the center of the artery. ⁷ When imaging vessels that exhibit kinking, coiling, or tortuosity, scanning in inaccurate imaging planes may falsely give the appearance of one of the above variants vs an aneurysm. Therefore, it may be considered best practice to include the additional use of a lower-frequency curved array transducer. This can provide a greater field of view than linear array transducers alone and better visualize these kinks, coils, and tortuous vessels using a deeper and wider imaging footprint. ¹²

Due to the risk of fatal complications, treatment of ECAAs is often considered necessary. ⁴ Treatment methods will often depend on the location, length, and size of the aneurysm. ⁴ There are multiple types of treatment for ECAAs, including surgical, endovascular, and medical interventions. ¹³ Conservative treatment is associated with a 71% mortality rate. ⁴ Surgical resection has been considered the gold standard for several decades, yet these treatments have higher rates of complications compared with endovascular approaches. ¹ Surgical approaches include aneurysm excision with reconstruction of antegrade flow via end-to-end anastomosis or graft interposition. Partial resection and direct or patch closure may be employed in cases where complete excision is not achievable. ¹⁰

Endovascular therapy has emerged as an effective alternative to open surgery in selected patients, such as those with high cervical aneurysms near the skull base or who are poor surgical candidates. This approach is associated with lower cranial nerve injury risk and has comparable in-hospital mortality and stroke rates. ¹⁰ While earlier endovascular therapies relied on transfemoral access, transcarotid artery revascularization (TCAR) represents a newer technique using direct carotid artery access. ¹⁰ Transcarotid artery revascularization is performed through a small cervical incision and involves temporary reversal of cerebral blood flow into the femoral vein via a filtration system, followed by stent deployment to restore arterial patency, and is typically associated with rapid recovery. Given the risk of thrombosis, stent graft occlusion, and restenosis, anticoagulant therapy and continued monitoring of the grafts are advised following endovascular intervention. ¹ Hybrid procedures combining surgical resection of a tortuous ICA segment with subsequent aneurysm stenting may be required in patients with ECAAs and a kinked distal ICA. ¹⁰

The ACR Appropriateness Criteria Cerebrovascular Diseases-Stroke and Stroke-Related Conditions suggest ultrasound should be the highly prioritized choice of imaging modalities for cerebrovascular disease. ¹⁴ Carotid duplex ultrasound is considered very useful in the evaluation of carotid artery pathology. The advantages of carotid duplex ultrasound examinations are that they are noninvasive and accurate in evaluating the degree of stenoses associated with cerebrovascular disease. While sensitivity and specificity are high in the detection of extracranial vascular disease, carotid duplex ultrasound does not provide information necessary to determine if thrombolytic medications or endovascular interventions should be used. ¹⁴ Head CTs with and without contrast are considered essential in the initial evaluation of cerebrovascular disease, especially when ruling out stroke; it is also essential to rule out intracranial hemorrhage (ICH). ¹⁴ The reason why CT is the recommended modality to utilize prior to administering thrombolytic therapy or before deciding to use endovascular treatments is because if these treatments are used when patients have ICH, they may lead to irreversible tissue damage (Pannell et al ¹⁴ ).

The first patient in the above cases presented with a pulsatile cervical mass and was diagnosed with a saccular aneurysm of the left distal ICA on duplex ultrasound, which was subsequently confirmed by carotid CTA. The second patient, who presented with a palpable cervical mass, underwent CTA demonstrating a large aneurysm at the right CCA bifurcation and was treated with TCAR placement of 2 ICA stents and endovascular coil embolization to exclude the aneurysm. Post-procedural CTA confirmed patency of the stents and intracranial arteries, and follow-up carotid duplex ultrasound corroborated extracranial carotid artery patency.

Conclusion

Extracranial carotid artery aneurysms are a rare, but clinically significant, vascular pathology. Although many patients remain asymptomatic or present only with a pulsatile neck mass, the risk of untreated ECAAs is severe, with potential complications such as cerebrovascular accidents, nerve compression, or fatal hemorrhage. Treatment of ECAAs is essential due to high mortality rates associated with conservative management, with options ranging from traditional surgical resection to less invasive endovascular therapies. Modern endovascular techniques, such as TCAR, offer effective alternatives with lower risks and faster recovery, though long-term monitoring and anticoagulation are necessary to prevent complications like thrombosis.

Extracranial carotid artery aneurysms’ diverse etiology necessitates a comprehensive diagnostic approach with carotid duplex ultrasound being the preferred initial diagnostic modality, providing a noninvasive method of detection and long-term surveillance for both conservatively managed and post-procedural patients. Computed tomography angiography and MRA are often used to confirm the diagnosis and guide treatment planning based on aneurysm location, extent, and patient comorbidities. Ultimately, a tailored approach, integrating multi-modality imaging with individualized surgical or endovascular strategies, is vital to the diagnosis and treatment of ECAAs.