31 December 2021: Articles
Challenging differential diagnosis, Unusual or unexpected effect of treatment, Rare diseaseMadeleine de Boer A* , Timothy P. Shiraev A , Jacky Loa A
Am J Case Rep 2021; 22:e935009
BACKGROUND: Extracranial carotid artery aneurysms are rare pathologies associated with an increased risk of neurological events and cranial nerve dysfunction. While they often require prompt intervention, the preferred surgical management remains unclear due to the rarity of this pathology, with described surgical and endovascular techniques having unique benefit and risk profiles in the current literature.
CASE REPORT: We report an interesting case of an internal carotid artery aneurysm successfully managed via open resection in a female patient in her 70s. Our patient, who was otherwise well, initially presented with an isolated episode of dysarthria associated with hypertension. Her pathology was identified on routine work-up for a presumed neurological event in the setting of her symptoms, and the patient referred to our center for definitive surgical management given the associated risk of embolic events. Under our care, the patient underwent an open resection of the ICA aneurysm with primary repair of the vessel. Her intra-operative and post-operative courses were unremarkable, and the patient remained well with no neurological deficits at follow-up at 4 months.
CONCLUSIONS: Our case demonstrates that select patients presenting with internal carotid artery aneurysms and tortuous internal carotid arteries, who may be otherwise ineligible for endovascular treatment, may be amenable to resection of the aneurysm followed by primary repair of the vessel, negating the requirement for interposition grafts.
Keywords: Aneurysm, Carotid Artery, Internal, embolic stroke
Extracranial carotid artery aneurysms (ECAA) are rare, representing only 0.9% of all arterial aneurysms [1,2]. While many internal carotid artery (ICA) aneurysms remain clinically silent, some manifest with neurological symptoms consistent with a transient ischemic attack (TIA) or stroke, a pulsatile neck mass, or cranial nerve dysfunction (resulting from mass effect of the aneurysm) [2–4]. Extracranial carotid artery aneurysms and ICA aneurysms are associated with a low risk of rupture, but they carry an increased risk of neurological episodes and cranial nerve dysfunction, and thus often require prompt management once diagnosed [3–5]. A study by El-Sabrout and Cooley described 65% of patients with ECAAs presenting with neurological events consistent with cerebral ischemia . Due to the rare occurrence of these aneurysms, the preferred surgical management of ECAAs remains unclear and debated within the literature . We present a case of this rare pathology, successfully managed via open surgical resection, detailing a primary repair of the ICA. The authors would like to thank the patient for providing consent for case publication.
A woman in her late 70s was transferred to our institution for further investigation and management of a left ICA aneurysm, discovered on imaging while being worked up for a presumed TIA. The patient initially presented to her local regional center with a 4-day history of a dull, frontal headache. This was associated with new-onset hypertension, with her systolic blood pressure measuring >200 mmHg at time of presentation, and an episode of dysarthria lasting a few minutes. She also described a new left-sided neck swelling, which was reported to have increased in size over the past 4 weeks. The patient denied additional neurological symptoms, specifically visual disturbances, facial droop, limb weakness, or pares-thesia. Her past medical history included a motor vehicle accident (MVA) 5 weeks prior, with her sustaining rib fractures while being a restrained passenger in a high-speed head-on collision, but there was no history of the patient sustaining either blunt or penetrating trauma to the neck. She denied a history of smoking, hypertension, ischemic heart disease, diabetes mellitus, or hypercholesterolaemia and was on no regular medications prior to presentation. The patient was commenced on atorvastatin 40 mg daily and aspirin 100 mg daily (without loading) at the peripheral center for a presumed neurological event.
As part of her initial work-up for a presumed stroke or TIA in the setting of dysarthria, a computed tomography (CT) brain and CT angiogram of the carotid arteries and circle of Willis was performed, with this demonstrating a 25×20×23 mm left internal carotid artery (ICA) aneurysm with minimal mural thrombus or atherosclerotic plaque within the wall of the aneurysm (Figure 1), and an intact circle of Willis. There was no evidence of recent infarction on these scans. Furthermore, no arrhythmias were observed on telemetry and no abnormalities were identified on the patient’s transthoracic echo-cardiogram, with both investigations performed as routine work-up for a presumed stroke. She was subsequently transferred to our tertiary institution for ongoing management. On arrival, the patient had experienced no further episodes of dysarthria and remained normotensive, with an unremarkable neurological examination. A pulsatile mass was palpated in her left neck below the angle of the mandible. A magnetic resonance imaging (MRI) brain and MRI angiogram was additionally conducted to further assess for ischemic cerebral events. Once again, the MRI angiogram demonstrated the internal carotid artery aneurysm (Figure 2), an intact circle of Willis, and no evidence of diffusion restriction to suggest an ischemic event. The patient’s inflammatory markers were un-remarkable, with her white cell count and c-reactive protein being within normal limits.
On admission, a neurology review was sought given the patient’s new-onset hypertension and dysarthria without evidence of ischemic events on imaging. The opinion of the neurology team was one of hypertensive encephalopathy, now resolved, as the cause of this patient’s dysarthria. However, early ischemic events not identified on imaging could not be excluded. A decision was made to proceed with resection of the ICA aneurysm given the high stroke rates associated with this pathology and the patient’s symptomatic presentation. Given the patent circle of Willis on both CT angiogram and MR angiogram, in addition to the plan to reconstruct the carotid artery, it was the decision of the operating surgeon to not perform a balloon occlusion test prior to surgery.
Our patient subsequently underwent resection of the left ICA aneurysm under general anesthesia with neuromonitoring via motor- and somatosensory-evoked potentials following nasotracheal intubation. The left ICA aneurysm was exposed via a longitudinal incision along the anterior border of the sterno-cleidomastoid, with the muscle belly retracted laterally to expose the internal jugular vein (IJV). After ligation of the common facial vein, the IJV was retracted laterally to expose the common carotid artery (CCA), which was looped with a silastic loop to gain proximal control. Dissection was then continued distally to expose the base of the ICA aneurysm and the external carotid artery (ECA), which was also looped with a silastic vessel loop. After adequate exposure of the inflow and out-flow vessels of the aneurysm and systemic heparinization (with 5000 IU administered), proximal and distal control of the ICA was obtained with clamps, with no change to the motor- and somatosensory-evoked potentials. Given the stable potential readings, a carotid shunt was not placed. The proximal and distal portions of the ICA were transected to exclude the aneurysm (Figure 3) and an end-to-end anastomosis of the vessel was performed using double-ended 6-0 prolene. After appropriate venting and closure of the arteriotomy, clamps from the ICA were removed and hemostasis was achieved. A 10-Fr Bellovac™ drain (Mediplast, SE) was placed, and the platysmal layer was subsequently closed with Vicryl sutures, followed by closure of the skin with monocryl. Minimal mural thrombus was noted within the aneurysm following on-table transection.
The most distal portion of the ICA aneurysm was high, at the distal end of the C3 vetebra. Surgical exposure of high carotid bifurcations is often limited by the angle of the mandible . As a result, a nasal intubation was performed to allow displacement of the angle of the mandible, facilitating distal ICA exposure. Given the location of the bifurcation, the ENT surgical team was also consulted in the event that mandibular subluxation, mandibulotomy, or division of the styloid process was also required to facilitate adequate exposure distal to the aneurysm to achieve proximal control.
The patient’s post-operative course was unremarkable. The drain was removed on post-operative day 1 after minimal output in a 24-h period, and the patient was discharged on post-operative day 2 with instructions to continue daily aspirin and atorvastatin.
On follow-up at 4 months, our patient remained well with no further episodes of dysarthria. Blood pressure readings with her general practitioner demonstrated ongoing hypertension, necessitating the commencement of an angiotensin-converting enzyme inhibitor (ACEi), and her wound had healed well. Arterial duplex imaging at this time demonstrated a patent left common carotid artery, external carotid artery, and internal carotid artery, with no stenosis at the anastomotic site.
The most common underlying cause of the pathogenesis of ECAAs is atherosclerosis (37–42%), closely followed by trauma.
Such aneurysms may also result from connective tissue disorders (such as Marfans syndrome or Ehlers-Danlos syndrome) or infection (mycotic aneurysms), although these etiologies are less common [1,3,4]. Extracranial carotid artery aneurysms are most commonly located within the CCA, near the bifurcation . The case described occurred in the rarer location of the mid-internal carotid artery and was attributed to athero-sclerotic causes, given the absence of trauma to the region or connective tissue disorders.
The mainstay of treatment described in the current literature is open surgical repair, often with an interposition graft, excision of the aneurysms, and primary anastomosis or carotid ligation [1–3]. However, open intervention carriers a significant risk of cranial nerve damage and intra-operative stroke (particularly in aneurysms with high burdens of intramural thrombus). Throughout the literature, open surgical repair is favored in patients experiencing symptoms of mass effect, bleeding, or ischemic complications due to the presence of the aneurysm [1–3]. Ligation of the ICA distal to the aneurysm is often employed as a last resort due to the high risk of stroke and mortality associated with this intervention (25% and 20%, respectively) . In cases where ligation is anticipated, balloon occlusion tests should be performed pre-operatively to evaluate cerebral ischemic tolerability in the setting of ICA ligation or permanent occlusion of the carotid artery, particularly as up to 26% of patients who undergo sacrifice of the carotid artery experience cerebral infarction [8,9]. A recent study by Wong et al reviewed the efficacy of pre-operative balloon occlusion tests in the management of 23 carotid artery aneurysms and pseudoaneurysms prior to main trunk occlusion. The authors reported it to be an effective screening tool to identify patients at risk for ischemia, with the results of the investigation altering the management plan of 21% of the cohort .
Endovascular techniques have been described in a small number of cases, with covered stents being employed to exclude the aneurysm from circulation and bare metal stents employed for stent-assisted coiling of the aneurysm sac . Aneurysms most amenable to endovascular management include those of the distal cervical segment of the ICA and those occurring in patients with hostile necks (due to prior surgery or radiation) in which scar tissue may increase the risk of cranial nerve damage . Complications reported with endovascular management of extracranial aneurysms include instent thrombosis, stenosis or occlusion, stent fracture, and persistent endoleak from poor stent apposition . Given the tortuosity of the ICA in the described case, it was the opinion of the operating surgeon that placement of a covered stent or bare metal stent to assist with coiling would predispose to stent kinking or occlusion.
A case series by Huyzer et al described 3 patients with extra-cranial carotid aneurysms, all successfully managed by aneurysmectomy and repair with interposition grafts. Complication rates were low, with only 2 patients sustaining temporary paresis of the facial nerve and vocal cord . The tortuosity of the ICA in our patient excluded the possibility of endovascular repair but facilitated the excision of the aneurysm with a primary end-to-end anastomosis of the ICA with relative ease, negating the need for an interposition graft. A case report by Abbas et al described a patient with a large internal carotid artery aneurysm managed via open resection in a similar fashion to our patient, with a mild complication of residual numbness over the incision site, likely resulting from transection of the transverse cervical nerve .
While the preferred technique (open vs endovascular) is still debated within the literature, surgical management of extra-cranial carotid aneurysms remains the first-line treatment, given the increased risk of embolic events from such aneurysms [1,2]. However, a recent study by Frankhauser et al reviewed 141 extracranial carotid artery aneurysms and pseudoaneurysms, with 56% of the cohort undergoing medical management. The authors reported that no patient undergoing medical management, which consisted of antiplatelets or anticoagulation, suffered mortality or major morbidity as a result of the aneurysm. However, it is also important to note that medical management was the preferred treatment method in asymptomatic patients . Thus, medical management may be appropriate in asymptomatic patients who would otherwise be too comorbid to undergo surgical intervention, or be at high risk of cranial nerve damage due to previous radiotherapy or surgical intervention (ie, patients with hostile necks).
While rare, ECAAs confer significant stroke risks and should therefore be promptly treated. Cases of ECAA with tortuous ICAs may be amenable to resection of the aneurysm, followed by primary repair of the vessel as described, negating the need for interposition grafts. Best practice in terms of surgical management remains unclear, largely due to the rarity of the condition, which makes large-sample randomized controlled trials and multicenter studies difficult; therefore, case reports such as this are required to add to the body of evidence surrounding treatment practices.
FiguresFigure 1.. CT Angiogram demonstrating the ICA aneurysm in axial (A), coronal (B), and sagittal (C) planes. The inflow of the aneurysm (green arrow) and outflow (blue arrow) is best appreciated in the sagittal plane. Figure 2.. MRI angiogram demonstrating the ICA aneurysm and filling within the aneurysm sac. The internal carotid artery is indicated by the blue arrow, the aneurysm sac by the star, and the external carotid artery by the red arrow. Figure 3.. (A, B) Left internal carotid artery aneurysm post excision. LIGACLIPs™ (Ethicon Medical, OH) are seen on the proximal ICA, and a tie on the distal ICA.
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