A challenging case of recurrent and progressive fusiform anterior circulation intracranial aneurysms: illustrative case

Abstract

BACKGROUND

Intracranial fusiform aneurysms are circumferential dilations of cerebral arteries that can lead to complications including ischemic stroke due to vessel occlusion, subarachnoid hemorrhage, or intracerebral hemorrhage. Treatment options for fusiform aneurysms have expanded significantly in recent years. Microsurgical treatment options include proximal and distal surgical occlusion and microsurgical trapping of the aneurysm, usually in association with high-flow bypass procedures. Endovascular treatment options include the placement of coils and/or flow diverters.

OBSERVATIONS

Here the authors report a case of aggressive surveillance and treatment of a man with multiple progressive, recurrent, and de novo fusiform aneurysms of the left anterior cerebral circulation over 16 years. Because the long-term course of his treatment coincided with the recent expansion of endovascular treatment options, he underwent every type of treatment listed above.

LESSONS

This case demonstrates the wide range of therapeutic options for fusiform aneurysms and how the treatment model for these lesions has evolved.

We present a case of a patient with progressive and de novo fusiform aneurysms limited to the left anterior cerebral circulation. Over the course of 16 years, he was treated with multiple modalities including clipping with extracranial-intracranial bypass, proximal occlusion, trapping, coil embolization, and flow-diverting embolization. We briefly discuss the etiology and natural history of fusiform aneurysms as well as the evolution of and role for new treatment options in these challenging aneurysms. The timeline of angiography and aneurysm interventions performed is detailed in Supplemental Figure 1.

Illustrative Case

A 43-year-old right-handed man with no past medical history, occasional tobacco use, and no family history of aneurysm was transferred to our facility with new right-sided hemiparesis and expressive aphasia. A noncontrast head computed tomography scan demonstrated a modified Fisher grade 2 diffuse subarachnoid with intraventricular hemorrhage (Fig. 1A), and magnetic resonance imaging confirmed an infarction in the left basal ganglia (Fig. 1B). Catheter angiography further characterized fusiform aneurysms involving the left middle cerebral artery (MCA) M1 (24 mm) and M2 (8 mm) segments, left anterior cerebral artery (ACA) A1 (12 mm) and callosal marginal (3 mm) segments, and fusiform dilation of the left internal carotid artery (ICA) terminus (7 mm) (Fig. 1D and E). Additional workup did not reveal an etiology for aneurysm formation (Supplemental Table 1).

FIG. 1.

Initial presentation with multiple fusiform dilations of the left MCA and ACA. Axial noncontrast head computed tomography (A) demonstrating diffuse subarachnoid blood in the basal cisterns, with a more focal hyperdensity in the region of the left MCA fusiform aneurysm (single arrow). Ten days later, magnetic resonance imaging demonstrated a subacute infarct in the left basal ganglia (double arrows), as seen on the apparent diffusion coefficient (B) sequence, and thrombosis within fusiform aneurysms of the left MCA and ACA (single and double arrowheads, respectively; C) on a T2-weighted sequence. Anteroposterior (D) and lateral (E) projections of catheter angiography demonstrating 5 fusiform aneurysms of the left-sided circulation: M1 (single black arrow), M2 (double black arrows), A1 (single white arrow), callosal marginal (double white arrows), and ICA terminus (white arrowhead).

The left MCA M1 segment was clipped proximal to the aneurysm and a flow-reversing bypass was performed with an autologous radial artery graft connecting the left external carotid artery (ECA) to the MCA M2 posterior division (Video 1). Intraoperative angiography confirmed bypass patency with anterograde M2 flow and slow retrograde filling of the M1 fusiform aneurysm distal to the clip. He was discharged on postoperative day 8 with modest improvement in aphasia and right hemiparesis.

VIDEO 1. Clip showing operative treatment of the left MCA M1 segment via proximal clipping and a flow-reversing bypass with an autologous radial artery graft. Click here to view.

A follow-up angiogram 4.5 months later revealed a new left MCA M2 temporopolar branch 7-mm aneurysm proximal to the prior distal anastomosis of the radial artery graft, patency of the bypass, and stability of the remaining aneurysms. Two weeks later, this M2 aneurysm was treated via endovascular coil embolization. Additionally, the previously identified left ACA callosal marginal artery aneurysm rapidly increased in size between the angiograms 2 weeks apart, prompting intervention via craniotomy for clipping. The aneurysm was partially thrombosed and a thrombectomy with vessel reconstruction via serial straight fenestrated clip placement was attempted (Video 2). Because anterograde flow could not be re-established, the aneurysm was then trapped, with subsequent robust retrograde collateral flow confirmed from the distal callosal marginal artery. Pathologic analysis of the aneurysm showed expected acute and organizing thrombus with myxoid changes, reactive fibroblasts, granulation tissue, hemosiderin-laden macrophages, and adhesive thrombus. Follow-up angiography at 9 and 15 months after initial presentation demonstrated robust patency of the bypass and stability of the remaining left ACA A1 fusiform aneurysm.

VIDEO 2. Clip showing operative treatment of the left ACA aneurysm via attempted clip reconstruction with distal flow reversal. Click here to view.

Twenty-four months after presentation, angiography demonstrated a recurrent left ACA A2 aneurysm proximal to the prior clip ligation (Fig. 2A and B). A third left frontal craniotomy for trapping and excision of the recurrent ACA aneurysm was performed. The fusiform left ACA A1 aneurysm was thrombosed and approximately 10 times larger than its luminal angiographic appearance. Intraoperative angiography following clip placement demonstrated a proximal left ACA occlusion (Fig. 2C and D). Further operative dissection revealed extensive involvement of the proximal left ACA. An end-to-end anastomosis of the proximal A2 segment to the distal pericallosal artery was not feasible secondary to distance, so the aneurysm was trapped with robust retrograde collateral flow from the distal pericallosal artery. Surgical pathology showed a luminal organizing thrombus with inflammation but no infectious or granulomatous components, and patchy loss of the internal elastic lamina.

FIG. 2.

Catheter angiography performed 24 months after presentation with anteroposterior (A) and lateral (B) views demonstrating a new left A2 junction aneurysm (arrow) and a patent ECA-MCA bypass (double arrows). Following a craniotomy for aneurysm clipping, an intraoperative angiogram with anteroposterior (C) and lateral (D) views demonstrated proximal left ACA occlusion (arrowhead).

An 8-month postclipping angiogram demonstrated stability of the patient’s left ACA A1 aneurysm but revealed a new 4-mm left ACA orbitofrontal fusiform aneurysm. A 19-month postclipping angiogram demonstrated a decrease in luminal caliber of the left ACA A1 aneurysm to 7 mm, suggesting thrombosis or remodeling of this segment. Fourteen months later, the left ACA A1 fusiform aneurysm luminal diameter increased to 10 mm, with an inferior excrescence and more dysplastic configuration. These dysplastic changes prompted intervention to secure the left ACA aneurysmal segment (Fig. 3A and B).

FIG. 3.

Catheter angiography with anteroposterior (A) and 3D-reconstructed (B) views demonstrating interval growth of the left A1 fusiform aneurysm (arrow), with an inferior excrescence (arrowhead). Following a balloon occlusion test, endovascular coil embolization at the level of the ICA terminus was performed, resulting in cessation of flow through the ACA aneurysm (double arrows) on anteroposterior (C) and lateral (D) projections. Catheter angiography 1-year postintervention demonstrated no recanalization or aneurysm recurrence on anteroposterior (E) and lateral (F) views.

After passing a left ICA temporary balloon occlusion test, the patient underwent coil embolization of the left ICA terminus occluding the left ACA A1 aneurysm (Fig. 3C and D). An angiogram 1 year later demonstrated complete occlusion of the left ICA and ACA aneurysms and robust filling of the ECA-MCA bypass to MCA branches and posterior cerebral artery to ACA pial and pericallosal collaterals (Fig. 3E and F).

Three years after this last intervention, and 8.5 years after presentation, angiography demonstrated subtle fusiform dilation of an early frontal MCA branch and the ECA-MCA bypass angular recipient branch. Subsequent angiography demonstrated interval dilation of the MCA angular branch to 7.5 mm with a new focal MCA M2 segment dilation over 1 year (Fig. 4A and B). This growth prompted consideration for endovascular flow diversion with a Pipeline embolization device (PED). Successful placement of 2 PEDs across the separate MCA fusiform dilations distal to the bypass anastomosis was performed (Fig. 4C and D). Eight-month follow-up angiography demonstrated favorable remodeling of the proximal PED-treated fusiform aneurysm and mild persistent fusiform dilation of the distal segment of the distal PED (Fig. 4E and F).

FIG. 4.

Catheter angiogram showing fusiform aneurysm of the MCA (arrow), distal to the prior ECA-MCA bypass on anteroposterior (A) and lateral (B) projections. Treatment of the MCA aneurysm with flow- diverting stent (double arrows, C and D). Catheter angiogram 1 year following treatment showed favorable remodeling of the treated MCA aneurysm (arrowhead), as seen on anteroposterior (E) and lateral (F) views.

After several stable angiograms, a follow-up 5.5 years later revealed multiple M2 segments of fusiform dilation, including between the 2 previously placed PEDs, in an anterior M2 branch arising from the intervening dilated segment, and a separate frontal M2 branch arising from the previously PED-treated segment (Fig. 5). Given the favorable vascular remodeling of the previously PED-treated segments, PED placement bridging the prior PEDs as well as flow diversion of the anterior M2 branch aneurysm were performed uneventfully. Continued close follow-up angiography is planned to assess for treatment response and any concerning dilation.

FIG. 5.

Catheter angiography 5.5 years after MCA fusiform aneurysm treatment with flow-diverting stents demonstrated interval fusiform dilation between the stents (arrow) on anteroposterior (A) and 3D-reconstructed (B) views. An additional flow-diverting stent was placed across the new MCA fusiform dilation (double arrows), as shown on anteroposterior (C) and lateral (D) projections of catheter angiography.

Discussion

Observations

Here we report a patient with multiple and recurrent fusiform cerebral aneurysms. Cases of multiple and recurrent fusiform cerebral aneurysms are rare. A few groups have reported cases of multiple primary aneurysms,¹ recurrent aneurysms,² and formation of multiple recurrent secondary aneurysms.^3,4 While all of these cases highlight multiple or recurrent aneurysms, the current case is unique due to multiple aneurysms confined to the left anterior circulation without a clear etiology or clear risk factors. Furthermore, this patient underwent many treatment modalities, including surgical trapping and bypass, endovascular deconstruction, and endovascular flow diversion. This variety of treatments in 1 patient has not been previously reported.

Lessons

Unlike saccular aneurysms that arise from arterial segments with a normal circumferential diameter, fusiform aneurysms are circumferential dilations of the parent artery.^5,6 An early event in fusiform aneurysm formation is rupture of the internal elastic lamina.⁷ This arterial dissection may lead to bleeding within the vessel wall, followed by intramural clot formation, clot expansion, and vessel occlusion. Recanalization results in the focal fusiform dilation of the arterial wall that may expand laterally or longitudinally. Compared with saccular aneurysms, fusiform aneurysms are rare and most often affect males younger than 50 years old.⁸ Approximately 80% of fusiform aneurysms arise in the posterior circulation, while anterior circulation fusiform aneurysms most commonly arise in the MCA, followed by the ICA and ACA.^8–10

Nonatherosclerotic fusiform aneurysms generally have a more benign natural history than atherosclerotic fusiform aneurysms.¹¹ Potential etiologies include genetic collagen disorders, von Recklinghausen’s disease, fibromuscular dysplasia, systemic lupus erythematosus, and tumor invasion of the vessel wall.¹⁰ However, patients with larger diameter aneurysms or symptomatic presentation are more likely to progress with aneurysm enlargement.¹¹

Fusiform aneurysm treatment has evolved considerably in the last 2 decades. Microsurgical treatment of these aneurysms may include proximal occlusion, distal occlusion, and complete microsurgical occlusion depending on the anatomy, and may often involves extracranial-intracranial bypass. Often, intimal flaps that occur in fusiform dissecting aneurysms can occlude blood flow, which can be especially problematic during clip reconstruction of these lesions. Frequently, these microsurgical treatments are combined with endovascular techniques. Endovascular deconstruction of a fusiform aneurysm involves coil occlusion of the diseased segment but requires adequate collateral flow to the downstream cerebral parenchyma. Endovascular flow diversion may preserve flow through the parent, but it also may not control progressive dilation of the aneurysmal segment as well as surgical approaches and endovascular deconstruction.^12,13 Although small case series have described equipoise between deconstructive and reconstructive treatments for fusiform aneurysms, further research is needed to elucidate their relative merits.¹⁴

The patient presented has been followed by our team for over 16 years for progressive, recurrent, and de novo fusiform aneurysms of the left anterior circulation. Despite ongoing testing for a genetic predisposition to dissection or aneurysm formation, we have not identified a clear etiology for this patient’s unique presentation. Given the restriction of these aneurysms to the left anterior circulation, and the shared embryologic origin of the ACA and MCA from the anterior division of the ICA during development,¹⁵ it is possible that more focal genetic or epigenetic factors during development underlie these progressive, recurrent, and de novo aneurysms in this patient. This case illustrates the range of therapeutic approaches to these challenging lesions and how the treatment paradigms have evolved over time. Our team proposes that the aggressive surveillance and treatment of this patient’s aneurysms were especially warranted given his history of progression and recurrences.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: all authors. Acquisition of data: Coxon, Chatterjee. Analysis and interpretation of data: all authors. Drafting of the article: Coxon, Huguenard, Chatterjee. Critically revising the article: all authors. Reviewed submitted version of the manuscript: all authors. Administrative/technical/material support: Dacey. Study supervision: Dacey.

Supplemental Information

Videos

Video 1. https://vimeo.com/781131759.

Video 2. https://vimeo.com/781134112.

Online-Only Content

Supplemental material is available with the online version of the article.

Supplemental Figure and Table. https://thejns.org/doi/suppl/10.3171/CASE22497.