Cath Lab Digest

Introduction
True aneurysms of the extracranial internal carotid artery (EICA) are extremely rare and have been thought to be secondary to atherosclerosis.¹ Other less common causes include fibromuscular dysplasia, Takayasu’s Arteritis, neurofibromatosis and Marfan’s syndrome.^2,3 In addition, pseudoaneurysms may arise after trauma, carotid surgery, infection and radiation. Rupture is rare with this form of aneurysm, however, neurological symptoms are relatively common and conservative therapies carry significant risk.

Case Report
A 39-year-old non-smoking woman presented with a pulsatile swelling in her left neck immediately below the angle of the mandible. She had a history of degenerative lumbar spine disease, chronic low back pain and spinal canal stenosis associated with mild, right-sided lower limb weakness. There was no prior history of atherosclerotic disease, fibromuscular dysplasia, neck trauma, hypertension or hyperlipidemia. Physical examination revealed a 4 cm pulsatile neck mass with normal contralateral carotid and peripheral pulses.

Contrast-enhanced magnetic resonance angiography was performed with 3-D reconstructions that demonstrated two fusiform aneurysms of the left EICA, each measuring approximately 3 cm in diameter. There was no thrombus visible within the aneurysms. Because the aneurysms extended close to the base of the skull, we decided to use an endovascular treatment approach.

The patient was premedicated with 300 mg of clopidogrel on the evening prior to the intervention. The procedure was performed under general anesthesia. Right femoral access was obtained, and diagnostic angiography confirmed the presence of a bilobed EICA aneurysm. The intracranial circulation was unremarkable, and 5000 U of heparin was given intravenously. The left external carotid artery was selectively cannulated and coil embolized. The left internal carotid was selectively cannulated and the aneurysmal segments were crossed using a 5F vertebral catheter and a 0.035" glide wire. The 5F sheath was exchanged for a 10F, 80 cm (Arrow International, Reading, Pennsylvania) sheath over an Amplatz wire. The aneurysm was excluded using two overlapping covered stents (Gore Viabahn 6 mm x 5 cm, Gore Hemabahn 8 mm x 10 cm, W.L. Gore, Flagstaff, Arizona). The proximal stent extended several centimeters into the common carotid artery. A 6 mm x 40 mm balloon was gently inflated at the site of stent overlap. Completion angiography confirmed brisk flow through the stents with no filling of the aneurysms. There was no evidence of distal embolization on the intracranial views.

Post-procedurally, the patient was noted to have apparent worsening of her right-sided weakness with development of expressive dysphasia. Computed tomography of the brain was normal. An urgent computed tomography angiogram of the carotid arteries demonstrated patent stents with no evidence of thrombus or endoleak. The intracranial circulation was normal. After a neurological consultation, she was returned to the angiography suite for cerebral angiography. No evidence of intracranial embolization was identified. In view of the patient’s symptoms, an empirical decision was made to selectively infuse the left middle cerebral artery with 300,000 U of urokinase over 15 minutes. After the procedure, the patient was anticoagulated with heparin and warfarin. The patient gradually returned to her pre-procedural level of limb weakness over a 10-day period. A follow-up duplex scan at two weeks confirmed patency of the left carotid vessels and complete exclusion of the internal carotid artery aneurysms, which had also significantly reduced in size.

Discussion
Aneurysms of the extracranial EICA comprise between 0.4 and 1% of all arterial aneurysms.^4,5 Men are twice as likely to be affected, with the average age of 56 years. Occasionally they may be bilateral and associated with other arterial aneurysms, especially when saccular.

There is considerable discrepancy in the literature with regard to aetiological factors responsible for this disease. The most common causes quoted are atherosclerosis (9.5–83%), fibromuscular dysplasia (17–35%), trauma (4.1–47.6%) and pseudoaneurysm (11.1–51.3%). Of those pseudoaneurysms described, there is an even distribution of post surgical (3.6–26%), mycotic (2.6–23.8%), congenital (7.1–16.7%) and dissecting (9.5–15.8%).⁶

Most EICA aneurysms will present with neurological symptoms related to either thromboembolic events or compressive cranial nerve palsies, including Horner’s syndrome. Less common presentations include dysphagia, pharyngeal hemorrhage or otorrhagia, and some present as an asymptomatic neck swelling.
Conservative treatment of EICA aneurysms had been reported to be associated with a significant incidence of neurological complications. Several studies reported death and stroke rates between 16 and 71%, from either thromboembolic neurological events or intracerebral bleeds secondary to anticoagulation.^7–9 Sir Astley Cooper was the first to publish a technique for surgical ligation of carotid aneurysms in 1808.¹⁰ However, this approach has been associated with a risk of neurological deficit of between 34.3 and 50%^11–13 Most recent surgical options include resection of the aneurysm with primary repair, patch angioplasty, interposition graft or excision of aneurysm with reimplantation of the EICA into the external or common carotid arteries.^6,14 Two thirds of EICA aneurysms are located at or near the bifurcation, allowing relatively safe surgical access, whereas the remaining third are found in the distal EICA and present a considerable challenge to the surgeon, as well as additional risk of morbidity for the patient.¹⁵