Extracranial-Intracranial Bypass with Reconstruction Clip Surgery Following Failed Flow Diverter Therapy for a Giant Internal Carotid Aneurysm: A Case Report

Abstract

Flow diverter (FD) is often the first-line treatment for giant internal carotid artery aneurysms, with a high rate of aneurysm occlusion. However, up to 10% of giant cerebral aneurysms increase in size after FD treatment. Surgery is usually considered if the giant internal carotid artery aneurysm continues to enlarge and cause compression. We report a case of a giant internal carotid artery aneurysm that continued to increase in size after FD treatment and was subsequently treated surgically. We also review the literature on the management of giant cerebral aneurysms that increased in size after FD. A 41-year-old female patient was diagnosed with a right giant internal carotid artery aneurysm and was initially treated with FD. After FD, the patient's vision in the right eye did not improve. Despite medical treatment, her vision continued to deteriorate. The patient presented at our hospital with reduced vision in both eyes. Magnetic resonance imaging and digital subtraction angiography with balloon test occlusion confirmed the presence of a giant thrombosed aneurysm in the right internal carotid artery, compressing the right optic nerve and optic chiasm. The patient underwent external carotid artery-middle cerebral artery bypass surgery using a radial artery graft, aneurysm sac dissection with thrombus removal, and reconstructive clipping of the aneurysm neck. After surgery, the patient's vision in both eyes improved immediately and did not develop any new neurological symptoms. Extracranial-intracranial arterial reconstructive surgery is a viable option for treating giant internal carotid artery aneurysms that have undergone FD treatment but continue to present with progressive mass effects.

Keywords

giant internal carotid artery aneurysm - reconstructive clips - EC-IC bypass - flow diversion devices - cerebral revascularizations - vision loss

Introduction

Giant aneurysms, with a diameter of ≥ 25 mm, account for approximately 5% of all cerebral aneurysms. They typically cause symptoms in patients over 40 years old. The cumulative risk of rupture within 5 years if the aneurysm is located in the anterior and posterior circulation is up to 40 and 50%, respectively.[1]

Treatment of giant cerebral aneurysms includes surgical intervention, and, more recently, treatment with flow diverters (FDs) has increasingly become widely used. Despite advancements in surgical techniques and technological improvements in endovascular interventions, treating giant cerebral aneurysms remain challenging.[2]

Endovascular intervention with FD has been increasingly indicated for the treatment of cerebral aneurysms over the past decade, demonstrating high rates of aneurysm occlusion with low disability/mortality rates.[3] However, for giant internal carotid artery (ICA) aneurysms, FD is often associated with poor outcomes, with complication rates reaching up to 25%.[4]

Complications following FD may include in-stent thrombosis, aneurysm rupture, and stent migration.[5] In symptomatic giant cerebral aneurysms, treatment with FD can result in a prolonged mass effect due to thrombosis within the aneurysm sac.[6]

To optimize the advantages and minimize the limitations of FD, a combined treatment strategy involving both FD and surgery has been proposed, with surgery being performed proactively.[7] [8] Furthermore, strategies for treatment after FD failure or complications have been discussed, with surgery being considered a viable option.[9] [10]

We report a case of a symptomatic giant ICA aneurysm with visual disturbances that was unsuccessfully treated with FD. The patient subsequently underwent bypass surgery combined with aneurysm clipping to remove the aneurysm sac, which relieved the optic nerve compression.

Case Presentation

Clinical Features

A 41-year-old right-handed female patient with no significant history of cerebral vascular conditions. The patient has no other significant medical history. The patient noticed blurred vision in her left eye in September 2023 and was diagnosed with a left giant ICA aneurysm at another hospital ([Fig. 1A]). She underwent FD stent placement on November 17, 2023. However, visual acuity in her left eye did not recover after the procedure.

Fig. 1 (A) Digital subtraction angiography (DSA) scan of a left giant internal carotid artery aneurysm, measuring 25 × 27 mm. (B–D) A magnetic resonance imaging (MRI) brain scan 3 months after flow diverter (FD) treatment. The aneurysm has thrombosed, but the size has decreased insignificantly (22 × 25 mm). (E–G) Some T2 sequences show a partially thrombosed aneurysm but with persistent blood flow. (H) The location of the FD after placement, with blood flow entering the aneurysm.

In January 2024, the patient began experiencing severe headaches and decreased visual acuity in her right eye. She returned to the hospital, where her FD stent was placed, and they confirmed that the aneurysm had not reduced in size. Since February 2024, the patient has visited several hospitals in Vietnam seeking alternative treatments. However, she only received internal medicine treatments with steroids and was advised to await the effectiveness of FD stent treatment. At the end of February 2024, the patient came to our hospital and was confirmed on magnetic resonance imaging (MRI) a giant left ICA aneurysm (diameter of 27 × 25 mm) compressing the optic chiasm and bilateral optic nerves ([Fig. 1B–D]), with thrombus within the aneurysm sac ([Fig. 1E–H]). We recommended further diagnostic imaging tests to determine the treatment plan, but the patient was not ready and preferred continuing pharmacologic treatment. However, the patient's right eye visual acuity continued to decline, and the patient returned to our hospital at the end of March 2024 (1 month after the MRI).

Upon admission to our hospital: The patient was alert, left eye visual acuity was almost completely lost (“hand motion” classification), right eye visual acuity was 20/25, with temporal vision field damaged. The patient experienced intermittent headaches and had no signs of focal neurological deficits. A digital subtraction angiography (DSA) was performed for the patient, identifying a giant left ICA aneurysm with a thrombus found within and blood flow still entering the aneurysm sac ([Fig. 2A, B]). A balloon occlusion test (BOT) without hypotension challenge revealed neurological symptoms in the patient ([Fig. 2C]).

Fig. 2 (A) Digital subtraction angiography (DSA) of the left internal carotid artery shows persistent blood flow into the aneurysm. (B) Flow diverter (FD) was placed in the internal carotid artery from the cavernous segment, with no coils present in the aneurysm sac.

We performed a high-flow extracranial-intracranial (EC-IC) bypass using a radial artery graft (EC-RA-M3 bypass), connecting from the superior thyroid artery to the M3 branch of the middle cerebral artery (MCA) using the side-to-end anastomosis technique. After completing the bypass, we dissected into the aneurysm sac and exposed the aneurysm and the distal segment of the ICA behind the aneurysm. The aneurysm was large, firmly compressing the left optic nerve and the posterior-inferior aspect of the optic chiasm. We temporarily clipped the cervical segment and distal segment (posterior to the aneurysm) of the ICA. The dome of the aneurysm was incised, and an intra-aneurysmatic thrombectomy was performed to relieve compression on the optic nerve and optic chiasm. Clips were inserted to reshape the aneurysm neck proximal to the ICA containing the flow-diverting stent ([Fig. 3A]). Finally, we removed the temporary clips from the cervical and distal segments of the ICA to confirm that the reconstructive clip had completely occluded the neck of the aneurysm.

Fig. 3 (A) After opening the aneurysm and removing the thrombus to relieve the optic nerve and optic chiasm, the aneurysm neck was closed with reconstructive clips. (B) Postoperative digital subtraction angiography (DSA) imaging confirmed good flow through the bypass, and the left internal carotid artery was preserved. (C and D) Magnetic resonance imaging (MRI) 1 month after surgery confirmed no ischemic or hemorrhagic brain injury.

The patient emerged from anesthesia and regained consciousness on the first day after surgery without neurological symptoms or perioperative strokes. Visual acuity in the right eye improved significantly immediately after surgery, and the patient could perceive light in the left eye.

The postoperative clinical course was stable, with no postoperative neurological symptoms. Clinical visual examination 2 weeks after surgery showed a complete recovery of visual acuity in the right eye (20/20); the left eye could perceive “hand motions” at 0.5 m. Postoperative DSA taken 3 days after surgery confirmed good patency within the bypass; the aneurysm sac was completely removed without any damage to the left ICA ([Fig. 3B]). After 1 month, the patient returned for a follow-up with a stable clinical presentation and no new neurological symptoms. Vision in the right eye is 20/20 and in the left eye is 1/10. A brain MRI confirmed no new areas of ischemia or bleeding ([Fig. 3C, D]).

Discussion

Giant ICA aneurysms account for about 5% of all cerebral aneurysms, usually symptomatic in patients aged 40 to 70 years,[1] though it can occur at all ages. In children, the incidence of cerebral aneurysms is lower than in adults, but giant cerebral aneurysms are more frequently seen in children compared to adults.[1]

Giant ICA aneurysms have a higher risk of enlarging compared to the overall rate of cerebral aneurysms (19.2% vs. 7.4%).[11] Two-thirds of giant cerebral aneurysms are located in the anterior circulation of the circle of Willis, while the remaining one-third are in the posterior circulation.[1]

Clinical manifestations of giant ICA aneurysms arise from mass effects, including optic and oculomotor nerve compression.[12] Less commonly, these masses can compress the hypothalamic region, leading to hypopituitarism or diabetes insipidus.[13] Other symptoms of giant aneurysms may include hemispheric compression due to a giant MCA aneurysm[14] or posterior fossa syndrome caused by a vertebrobasilar system giant aneurysm.[15] Brain ischemia is also seen in giant ICA aneurysms, with an incidence rate of up to 5%.[16]

The risk of rupture of giant ICA aneurysms is significantly higher than that of smaller aneurysms, and the ICA or internal carotid-posterior communicating artery has also been reported as a higher rupture risk site than other locations.[17] The rupture risk of unruptured giant cerebral aneurysms is as high as 40 to 50% within 5 years.[18]

The treatment of giant ICA aneurysms, despite many advancements, remains a challenge in neurosurgery.[4] [19] [20] [21] Treatment modalities include endovascular interventions, in which flow diverters (FD) are the preferred option,[8] [20] [22] surgery,[9] or a combination of both approaches.[2] [23] Wang et al. suggested combining FD with coiling to alleviate symptoms associated with compression from giant internal carotid artery aneurysms.[24]

FD is usually the first-line treatment for giant ICA aneurysms, as it redirects blood flow away from the aneurysm.[6] A reduction in cranial nerve compression after FD treatment of giant ICA aneurysms has been reported in several studies.[24] [25] [26] Recovery of pituitary function following treatment of a giant ICA aneurysm compressing the sella turcica has also been reported.[27] Bender et al reported a complete occlusion rate of 72, 78, and 87% for large and giant ICA aneurysms treated with FD at 6, 12, and 24 months after surgery, respectively.[28] A meta-analysis by Ye et al reported an overall aneurysm occlusion rate of 78.8% following FD, with a median follow-up time of 6.3 months.[20]

However, FD is not the only treatment choice for giant ICA aneurysms, as it also has several limitations. Due to its mechanism of vascular remodeling without directly addressing the aneurysm sac, there remains a risk of aneurysm rupture after FD treatment. Bender et al reported a 1.1% mortality rate following FD treatment of giant ICA aneurysms.[28] Theoretically, FD will redirect the blood flow within the vessel to limit blood entry into the aneurysm, gradually reducing its size. However, the opposite can occur, where blood continues to flow through the FD into the aneurysm, causing the aneurysm to enlarge and compress surrounding structures. Visual impairment is one of the most frequently mentioned symptoms in reports on this topic.[6] [19] In a patient with a cavernous segment giant ICA aneurysm treated by Misra et a,[19] not only did vision not improve after two flow-diverting stents were placed, but the patient also became blind 3 months after the second stent placement. This phenomenon is also seen in other reports. A study by Moon et al[6] found aneurysm enlargement after FD treatment occurred in 9.4% of patients with large and giant ICA aneurysms in the cavernous and paraclinoid regions. Moon et al also identified the duration of initial symptoms over 2 months as a factor associated with an increased risk of enlargement of large/giant ICA aneurysms, both in univariate and multivariate regression analyses.[6]

There are several treatment options when ICA aneurysms continue to enlarge, causing mass effects after FD treatment.[7] [9] [19] [24] [25] The patient in the report by Misra et al[19] was treated with an EC-IC arterial bypass, alleviating headache and nausea symptoms; however, vision loss (which occurred 3 months after the second FD placement) was not recoverable. In another patient reported by Campos et al, despite stenting, coiling, and then FD placement, neurological deterioration continued.[7] Straus et al[9] discussed the role of EC-IC arterial reconstruction surgery for cases of failure or worsening neurological clinical course after endovascular intervention. A study by Wang et al[24] on the role of FD in symptomatic large/giant ICA aneurysms did not provide information on management after FD placement. The authors suggested a window period from the time of FD placement to the reduction of large/giant aneurysm compression symptoms. In cases of visual impairment following FD treatment of compressive intracranial aneurysms, Szikora et al[25] treated with aggressive steroid therapy, but compression symptoms only began to improve after 6 months.

We chose to perform EC-IC revascularization surgery, then aneurysm sac excision and thrombectomy to relieve mass compression, and reconstructive clipping of the aneurysm neck for the following reasons: (1) the patient's vision was progressively worsening despite steroid treatment, necessitating relief of compression on the visual pathway (right optic nerve and optic chiasm) and (2) the patient exhibited neurological symptoms during the preoperative BOT, indicating that the left ICA could not be ligated. A bypass procedure would need to be performed before clipping the ICA aneurysm to mitigate the risk of litigating the carotid artery.

The bypass strategy selected at our center has been previously described,[29] where the high-flow bypass is chosen when BOT induces neurological symptoms. We usually select the radial artery as the first choice due to its relative size compatibility with the MCA. The saphenous vein is also another option. The M3 branch of the MCA is often the recipient artery for a high-flow bypass at our center to minimize the risk of cerebral hyperperfusion syndrome.

Our initial surgical plan was to perform a high-flow bypass, followed by trapping the aneurysm to relieve compression on the optic chiasm. However, after dissecting and opening the aneurysm, we altered our surgical strategy by placing a clip at the aneurysm neck to preserve the ICA ([Fig. 2]). This approach successfully relieved the compression on the optic nerve and chiasm while preserving the anatomy of the ICA.

Conclusion

FD stent is the first-line treatment, highly effective and safe, for treating large/giant ICA aneurysms. However, visual impairment due to aneurysm enlargement is not uncommon. Surgery to relieve optic nerve compression (with or without EC-IC revascularization) is an appropriate option, especially when visual impairment continues to worsen.

Conflict of Interest

None declared.

Author's Contributions

H.M.N., the primary doctor, conceived the original idea, performed the surgeries, and was responsible for writing and revising the manuscript. M.Q.N. conducted patient follow-ups and contributed to writing the manuscript. All authors participated in interpreting and discussing the results, and they collectively reviewed and approved the final manuscript for submission.

Ethical Approval

The study was approved by the Research Ethics Committee of University of Medicine and Pharmacy, Vietnam National University, Hanoi, Vietnam. The procedures used in this study adhere to the tenets of the Declarations of Helsinki.

Patients' Consent

The patient's parents have consented to the submission of the case report for submission to the journal. Written consent form is available upon request.

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Publication History

Article published online:
20 March 2025