Extracranial internal carotid artery aneurysm (ECCA) is a rare disease. Especially, the treatment of a giant thrombosed ECCA is technically challenging and unfamiliar to neurosurgeons. A giant thrombosed ECCA usually presents as a pulsatile neck mass and cause neurological events such as transient ischemic attack or ischemic stroke [3]. The treatment of these aneurysm is mandatory for symptomatic cases and some authors recommended to treat an aneurysm of more than 2-cm in size in asymptomatic case [2]. Although some authors have reported favorable short-term outcomes and low morbidity rate following endovascular treatment, the evidence to support favorable long-term outcomes and lower recurrence rate is still lacking [1,3,6,8,10,12]. Therefore, surgical resection and flow restoration are gold standard methods to treat this aneurysm. We report a case of a giant thrombosed ECCA which was treated by aneurysmectomy and graft interposition with technical details.

A 72-year-old woman presented with left side weakness and dysarthria. She had a medical history of hypertension, diabetes mellitus, osteoporosis, and thyroid cancer. Fourteen years ago, she underwent total thyroidectomy for thyroid cancer and subsequently received radioactive iodine ablation therapy. She also underwent craniotomy and aneurysmal neck clipping due to ruptured anterior communicating artery aneurysm 2 months later. Her brain diffusion weighted image showed high signal intensity in the right caudate nucleus and periventricular white matter (Fig. 1A). Cerebral angiography was performed following intravenous administration of recombinant tissue plasminogen activator which indicated a thrombosed ECCA and occlusion of the mid-portion of the right middle cerebral artery (Fig. 1B, C). Unfortunately, we could not perform mechanical thrombectomy due to ECCA and tortuous common carotid artery (CCA) (Fig. 1D). Thereafter, the patient’s motor weakness rapidly improved. Subsequent neck 3 dimensional angiography demonstrated complete recanalization of the right middle cerebral artery and 4 cm sized ECCA with contrast filling and thrombus (Fig. 1E, F). Taking into consideration a tortuous CCA and the thrombosed nature of ECCA, we decided to perform open surgery 4 months later.

The patient was administered 100 mg acetylsalicylic acid, starting 7 days before the surgery. The operation was performed under normocarbic, normotensive general anesthesia. The cerebral hemoglobin oxygen saturation was continuously monitored using near-infrared spectroscopy (Edwards ForeSight Brain Oxygenation Sensors^®, Edwards Lifesciences; Irvine, CA, USA) throughout the procedure. The patient was positioned supine with the head extended and turned away from the side of operation. A linear skin incision was made along the anterior border of the sternocleidomastoid muscle. The aneurysm, common carotid artery (CCA), external carotid artery (ECA), and distal internal carotid artery (ICA) were exposed (Fig. 2A). The aneurysm was firmly adhered to the external carotid artery and the posterior wall of carotid sheath. Prior to cross-clamping the CCA, ICA, and ECA, we administered systemic anticoagulation with unfractionated heparin and maintained activated clotting time >200 seconds throughout the operation. After cross-clamping, carotid shunt (Pruitt-Inahara^®, LeMaitre Vascular; Burlington, MA, USA) was first inserted into CCA via a small arteriotomy and secured by pulling up on the silk ties. The aneurysm was opened through a linear incision to the proximal and distal ends and a distal shunt tube was inserted into the orifice of the ICA. After confirming the flow to the carotid shunt, carotid shunt irrigation with mixed solution (20% albumin 20 ml+heparin 5000 IU+normal saline 200 ml) was performed every 10 minutes. The suture was performed with double armed 6-0 Prolene. Following suturing the graft (6 mm polytetrafluoroethylene (PTFE) standard wall type) into the proximal ICA with a continuous, non-locking fashion, the CCA clamp was released briefly to test the anastomosis being placed a separated clamp just distal to graft anastomosis (Fig. 2B). And then, the graft was pulled distally to match the appropriate length. Prior to completing distal anastomosis, the ICA clamp was released briefly to identify back bleeding to confirm distal thrombus and the carotid shunt was removed (Fig. 2C, D).

The patient discharged uneventfully and modified Rankin Scale score at 1 year was 0 points. A follow-up computed tomographic angiography taken 7 days after surgery and magnetic resonance angiography taken one year later showed no residual aneurysm and patent interposition graft (Fig. 2E, F).

The causes of ECCA include atherosclerosis, dissection, trauma, congenital and infection [3]. The exact pathophysiology of ECAA remain unclear, however Welleweerd et al. [11] suggested two distinct categories: dissection and degeneration in histological study of ECAA. Meanwhile, the pathogenesis of partially thrombosed aneurysms is different from the classical saccular aneurysms. The growth from repeated intramural thrombus in the aneurysmal wall has been suggested as its pathogenesis. Mural thrombus might act as a triggering factor for perivascular growth factors [5].

Two current management strategies of ECCA are conservative treatment or intervention. Asymptomatic small aneurysms may be managed conservatively, but symptomatic aneurysms are considered surgical or endovascular candidates. Although open surgery with aneurysm resection and flow restoration remains the gold standard, endovascular treatment is an alternative to open surgery [1,3,6,8,12].

In a single center study of 20 asymptomatic ECCA with conservative management, the ipsilateral stroke rate was 1.1 per 100 patient-years during median 46.5 months follow-up. The authors concluded conservative management seems justified in patients without growth [7]. Attigah et al. [1] reported long-term results (median follow-up 13.5 years) following surgical therapy of 64 ECCA. Perioperative stroke rate was 1.6%. Permanent and transient cranial nerve injury rates were 6.3% and 20.3%, respectively. The ipsilateral stroke-free times were 96%, 96%, 93%, and 87% after 5, 10, 15, and 20 years, respectively. Although there was a considerable risk of cranial nerve injury, the authors concluded that surgical reconstruction of ECCA is a safe procedure with good long-term results. A systematic review of endovascular stenting of ECCA included a total of 113 reports, involving 224 patients [6]. The incidence of strokes was 1.8% and the overall in-hospital mortality was 4.1%, but unrelated to procedures. Stent-graft patency was achieved in 93% with thrombosis of the aneurysmal sac during a mean follow-up period of 15.4 months. The authors concluded that endovascular treatment is feasible with a high success rate and relatively low complication rate. However, endovascular techniques need to be further evaluated due to little or no long-term follow-up results. In a recent review of 39 articles including a total of 1,239 patients, the 30 day mortality rate and stroke rate were 4.6% and 6.6% in conservatively treated patients (11%) and 1.9% and 5.1% in surgery group (89%), respectively [10]. The most common surgery-related complication was cranial nerve damage (11.8%). The authors concluded that due to limitations in reporting of results and confounding in indication, it was not possible to determine the optimal treatment strategy of ECAA and multicenter international registry is needed.

In this report, we selected surgical treatment due to tortuous proximal vessel and concerns regarding symptomatic recurrence. There are several technical points of view on performing aneurysmectomy and graft interposition. When end-to-end anastomosis is impossible due to no redundancy of ICA, graft interposition may be utilized. The femoral vein may be limited in its use in the routine procedure due to the time needed to harvest the vein or size mismatch. The artificial graft materials include polyester (Dacron) and PTFE. PTFE grafts may be more resistant to infection than Dacron. Although the use of carotid shunts remains controversial, we recommend its use for reducing cerebral ischemia in cases with poor collaterals and in the presence of recent stroke under monitoring with near-infrared spectroscopy. The proximal shunt tube may be inserted into the distal CCA via the orifice of resected ICA or separate small arteriotomy on the distal CCA [4]. We recommend inserting the proximal shunt tube through a separate small arteriotomy to facilitate anastomosis. If the proximal shunt tube is inserted into the orifice of the proximal ICA, the shunt tube passing through the graft remains inside the graft throughout the anastomosis and may hinder suturing. Some authors recommend complete excision of the aneurysm to minimize the risk of recurrence while others advocate leaving the posterior wall of the aneurysm, which reduces the risk of a cranial nerve injury [2,7]. Because the aneurysm was tightly adhered to the posterior wall of the carotid sheath and ECA, we left the back wall of the aneurysm intact. Furthermore, the aneurysm sac is helpful in preventing postoperative hematoma wrapping around stitch leakages.

Aneurysmectomy with graft interposition is feasible for the management of a giant thrombosed ECCA presenting with thromboembolic stroke. The vascular neurosurgeons need to know about surgical techniques in the management of ECCA.