Concomitant Unruptured Intracranial Aneurysms and Carotid Artery Stenosis: An Institutional Review of Patients Undergoing Carotid Revascularization

Background

The incidence of concomitant carotid artery stenosis and unruptured intracranial aneurysms (UIAs) has been reported at between 0.5% and 5%. In these patients, treatment strategies must balance the risk of ischemic stroke with the risk of aneurysmal rupture. Several studies have addressed the natural course of UIAs in the setting of carotid revascularization; however, the final recommendations are not uniform. The purpose of this study was to review our institutional experience with concomitant UIAs and carotid artery stenosis.

Methods

We performed a retrospective review of all patients with carotid artery stenosis who underwent carotid artery endarterectomy (CEA) or carotid artery stenting (CAS) at our institution between 2003 and 2010. Only patients with preoperative imaging demonstrating intracranial circulation were included. Charts were reviewed for patients’ demographic and clinical data, duration of follow-up, and aneurysm size and location. Patients were stratified into 2 groups: carotid artery stenosis with unruptured intracranial aneurysm (CS/UIA) and carotid artery stenosis without intracranial aneurysm (CS).

Results

Three hundred five patients met the inclusion criteria and had a total of 316 carotid procedures (CAS or CEA) performed. Eleven patients were found to have UIAs (3.61%) prior to carotid revascularization. Male and female prevalence was 2.59% and 5.26% (P = 0.22), respectively. Patients’ demographics did not differ significantly between the 2 groups. The average aneurysm size was 3.25 ± 2.13 mm, and the most common location was the cavernous segment of the internal carotid artery. No patient in the study had aneurysm rupture, and the mean follow-up time was 26.5 months for the CS/UIA group.

Conclusions

Concomitant carotid artery stenosis and UIAs is a rare entity. Carotid revascularization does not appear to increase the risk of rupture for small aneurysms (<10 mm) in the midterm. Although not statistically significant, there was a higher incidence of aneurysms found in females in our patient population.

Introduction

The existence of concomitant carotid artery stenosis and unruptured intracranial aneurysms (UIAs) has been reported at between 0.5% and 5%.1, 2, 3, 4, 5, 6, 7 In these patients, the treatment strategy employed must balance the risk of embolic stroke secondary to carotid artery stenosis with the risk of subarachnoid hemorrhage (SAH) secondary to intracranial aneurysm rupture.

The prevalence of UIAs is approximately 2% and subsequent rupture occurs at a rate of 1–3% per year.8, 9, 10, 11 Notably, the resulting SAH is associated with a mortality rate of 40–55%.5, 9, 12, 13 The most common risk factors associated with the development of intracranial aneurysms are female gender, increasing age, smoking, hypertension, excessive alcohol use, family history of SAH, autosomal dominant polycystic kidney disease (ADPKD), and previous SAH.10, 11 The risk of rupture has been demonstrated to be related to active smoking, female gender, younger age, aneurysm size and location, and prior SAH.9, 14, 15, 16 After diagnosis, follow-up noninvasive imaging with magnetic resonance angiography (MRA) or computed tomographic angiography (CTA) is recommended at 6 and 12 months, followed by annual imaging for at least 3 years to monitor for enlargement.¹⁵ The annual growth rate for UIAs is variable, but has been reported at between 27% and 32% yearly.¹⁷ Importantly, universal treatment protocols for patients with UIAs have yet to be established. Surgical intervention is ultimately based on aneurysm-specific (size, rate of growth, and location) and patient-specific factors (age, medical comorbidities, family history of ruptured intracranial aneurysms, and prior SAH).8, 14, 15, 18 The International Study of Unruptured Intracranial Aneurysms investigators demonstrated an extremely low rate of rupture for patients with small UIAs of <7 mm in diameter (0% risk of SAH at 5 years).⁸

In reference to carotid artery stenosis, multiple studies have supported the use of surgical intervention, either carotid endarterectomy (CEA) or carotid artery stenting (CAS), for both symptomatic and/or asymptomatic disease.19, 20, 21, 22 Interestingly, the prevalence of UIAs has been documented to be greater in patients with CAS than in the general population.² Heman et al. suspected that this reason is multifactorial, citing common risk factors such as atherosclerosis, as well as alterations in blood flow patterns associated with internal carotid artery (ICA) stenosis.² As such, a therapeutic quandary develops when a patient presents with both of these clinical findings.

One concern is that if the carotid artery lesion is intervened upon first, then the intracranial aneurysm may rupture while the patients awaits carotid revascularization. Furthermore, there is a theoretical risk of aneurysm rupture during and after CEA secondary to cerebral hyperperfusion syndrome.3, 23, 24 Alternatively, if management is first focused on aneurysm repair, then the patient may subsequently be at risk for perioperative cerebral ischemia as a result of a reduction in perfusion pressure during anesthesia.3, 4 There is also continued risk for ischemic stroke while awaiting carotid revascularization in this scenario.

Many case reports and case series have examined the outcomes of patients treated for carotid artery stenosis in the setting of UIAs; however, the final recommendations are not uniform.1, 3, 4, 5, 25, 26, 27, 28, 29, 30, 31, 32, 33 A recent meta-analysis by Khan et al. included a compilation of all previously published data and concluded that CEA did not significantly increase the risk of concomitant intracranial aneurysm rupture. Yet, they recognized that there may be a significant proportion of underreporting in the literature due to the lack of secondary intracranial imaging.⁶

The purpose of the present study was the review our institutional experience with patients who have undergone carotid revascularization for carotid artery stenosis in the setting of concomitant UIAs.