Treatment strategies for subarachnoid hemorrhage in a distal basilar dolichoectatic aneurysm: illustrative case

Abstract

BACKGROUND

Fusiform aneurysms of the distal basilar artery are challenging, with high morbidity and mortality. Brainstem perforating vessels, the lack of an aneurysm neck, critical anatomical location near the brainstem, and progression to a large size make any treatment difficult. They are usually treated in an elective planned setting. An acute rupture poses extra challenges. Treatment options are surgical or endovascular. Endovascular treatments have revolved around flow diversion, although given the irregular lumen, this is difficult. Open microsurgical techniques center around bypass and parent vessel occlusion.

OBSERVATIONS

A 54-year-old man was admitted to the authors’ hospital 4 days after experiencing a subarachnoid hemorrhage from a distal basilar fusiform aneurysm. The rupture point was clipped acutely. The aneurysm rupture point recurred quickly and required definitive treatment of the parent fusiform aneurysm with bypass and parent artery clipping.

LESSONS

This case illustrates challenging decision-making in the management of an acute subarachnoid hemorrhage from a complex aneurysm. The case was managed surgically with early treatment of the acute rupture and planned later definitive treatment of the parent aneurysm. Endovascular options are also discussed.

https://thejns.org/doi/10.3171/CASE25895

There is some evidence that fusiform and dolichoectatic aneurysms of the basilar artery are a different pathological entity¹ from saccular aneurysms, but they share intimal wall damage and thrombosis with more focal saccular aneurysms. Wall damage often leads to rupture, and this case illustrates both pathological processes and the complex decision-making required to initially treat a subarachnoid hemorrhage and its attendant sequelae, as well as later more definitive parent vessel occlusion with bypass grafting.

To our knowledge, this is an unusual presentation of dolichoectatic aneurysms with the added complexity of a difficult location of the rupture point surgically. It may be that the development of devices used in interventional neuroradiology will advance to provide more options, and certainly there are instances of the treatments being combined. Careful analysis of a number of factors such as mass effect, perforator location, flow from the anterior circulation, and aneurysm morphology will continue to be required in this heterogeneous group of patients to determine the best tailored treatment.

Illustrative Case

Presentation

A 54-year-old man was admitted to our hospital 4 days after experiencing a subarachnoid hemorrhage. He initially did not seek medical attention. CT imaging showed a heavy blood load (modified Fisher grade 3) and World Federation of Neurosurgical Societies grade III hemorrhage. CT angiography (CTA) and formal digital subtraction angiography showed a distal basilar dolichoectatic aneurysm with the rupture point of the saccular aneurysm on the right between the posterior cerebral artery (PCA) and superior cerebellar artery (SCA). We decided to treat the most imminent problem, the acute rupture, by securing the aneurysm rupture point with direct clipping. This would allow planning of the treatment of the parent aneurysm after the acute sequelae of the rupture, such as cerebral vasospasm, had resolved.

Endovascular Options

The aneurysm rupture point was not easy to see on formal angiography and did not appear to be in one of the commonly recognized arterial origins that we would expect. Some centers would have treated this by simple coiling. We decided to approach it surgically, as this would give a better appreciation of the anatomy and perforating vessels. Treatment by stent or flow diverter would not be indicated in the acute setting because of the requirement for antiplatelet therapy.

Treatment of the rupture point by either means would have been prone to the early recurrence that we eventually saw, and endovascular treatment would not have offered any treatment advantage.

Later definitive treatment of the fusiform parent artery by endovascular means remains uncertain, although with potential, dependent on future developments in implant design. There are problems sizing the implant in a vessel of variable diameter. Shapiro et al.² described this problem related to the lack of variable-diameter devices. Similar results were reported by Siddiqui et al.³ Mammadinova et al.⁴ described a potential solution using a stent-within-a-stent technique to overcome this.

An early case series⁵ reported the outcomes of flow diverting devices in fusiform vertebrobasilar giant aneurysms in 6 patients with a mean follow-up of 13 months. Three patients had recurrent cerebral infarctions, 2 patients presented with thrombotic stent occlusion, and 4 of the patients died during follow-up, highlighting the morbidity and mortality of this condition.

Natarajan et al. reported better results with endovascular therapy a few years later, in 2016.⁶ It is likely that as techniques and devices improve, so will outcomes.

Surgical Details

Surgery for clipping the rupture point is illustrated in Video 1. CTA showed a rupture point on the right side between the PCA and SCA. A right-sided frontotemporal craniotomy was performed via a distal transsylvian/anterior temporal approach. There were no posterior communicating arteries. The rupture point was approximately 5 mm above the clinoidal line.

VIDEO 1. Video showing the patient’s history, initial investigations, and the aneurysm location, both radiologically and anatomically. There is a discussion of treatment options and our adopted surgical strategy. The surgical details are shown, including positioning, approach to the aneurysm, clipping of the aneurysm, the rupture point, and indocyanine green angiography. CN3 = cranial nerve III; Pcom = posterior communicating artery. Click here to view.

Surgery at the basilar apex is well established using modifications of the pterional and subtemporal approaches.^7,8 The versatile anterior temporal approach^9,10 with its medial and lateral options utilizes benefits of both and allows visualization of perforating vessels, the basilar bifurcation, and the PCA. It was chosen as it provides sufficient exposure of the PCA to allow bypass using the superficial temporal artery (STA).¹¹

Immediately after surgery, CT/CTA showed rupture point occlusion, but 3 days later, the temporal lobe became swollen and an anterior temporal decompression was required. Furthermore, CTA performed after the cerebral vasoconstriction period showed a recurrence of the rupture point aneurysm. We decided to perform definitive surgery for this unstable aneurysm (Video 2).

VIDEO 2. Video showing complications after the initial clipping of the aneurysm in the form of cerebral vasospasm, and the requirement for decompressive surgery. Subsequent definitive treatment of the fusiform aneurysm via surgery is shown. This consisted of STA bypasses to the PCA and SCA with parent vessel occlusion of the basilar artery under motor evoked potential monitoring. Postoperative imaging and outcome details are presented. Click here to view.

STA-PCA and STA-SCA bypasses were performed to augment terminal basilar flow because the posterior communicating arteries were absent. The basilar artery was treated with parent vessel occlusion, and this allowed flow out to the contralateral large SCA after securing blood flow at the tip of the basilar artery.

After surgery, the patient experienced a transient oculomotor nerve palsy and mild cognitive dysfunction, but improved with rehabilitation and was discharged home asymptomatic at 3 months postoperatively.

Informed Consent

The necessary informed consent was obtained in this study.

Discussion

Observations

This case illustrates complex decision-making in an unusual presentation of a rare aneurysm of the basilar artery.

It is likely that this case represents an early form of a dolichoectatic aneurysm with tortuosity and increase in diameter over a long segment of the artery—thought to indicate remodeling.¹ It does satisfy Smoker’s¹² criteria for the diagnosis of vertebrobasilar ectasia, with the basilar artery being > 4.5 mm in diameter. The definition proposed by Brinjikji et al.,¹³ however, proposes a diameter size of > 6 mm for vertebrobasilar dolichoectasia.

Fusiform aneurysms of the vertebrobasilar complex are a distinct entity that may share some common features (arteriomegaly and remodeling) with similar aneurysms in the aorta and carotid and coronary arteries.¹³ The majority usually present with mass effect, thrombosis, and ischemic effects on small perforating vessels. There are little data on the hemorrhage rate of this type of aneurysm, perhaps due to small numbers and a heterogeneous cohort. Giant basilar apex aneurysms are known to present with hemorrhage rate of 20.4%.¹⁴ The annual mortality is high¹⁵ at 13% (95% CI 8%–19%), and this indicates prompt treatment. Treatment for fusiform and dolichoectatic aneurysms in this location lacks clear options. Endovascular therapy, although unproven, but could be promising.¹⁶ Surgery centers around some form of parent vessel occlusion to reduce blood flow in the aneurysm, with or without bypass reconstruction to compensate flow by an alternative route, in effect flow diversion or reversal.¹⁷

We were concerned that this flow modeling, which would reduce flow in the aneurysm and therefore perforator vessels, could exacerbate the effects of cerebral vasospasm in the acute phase of a subarachnoid hemorrhage. The patient’s blood load was high, and he presented late at day 4. The emergency clipping of the rupture point with later planned definitive treatment of the aneurysm seemed a reasonable compromise. This was successful in avoiding a further early rebleed as far as we could tell. However, imaging a few days later showed expansion of the rupture point, indicating that the aneurysm was unstable. We proceeded to definitive treatment of the aneurysm by parent vessel occlusion and bypass to the PCA and SCA using the STA. Posttreatment imaging at 3 months showed that the aneurysm was successfully treated and the bypass grafts were working. The patient had a modified Rankin Scale score of 0 at discharge.

Lessons

The treatment priorities of fusiform basilar aneurysms depend on morphology and mode of presentation. Subarachnoid hemorrhage as presentation requires urgent treatment of any defined rupture point. It may illustrate more extensive vessel wall disease that mandates early definitive treatment of the parent aneurysm.

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: Suzuki. Acquisition of data: Suzuki. Analysis and interpretation of data: Phillips. Drafting the article: Phillips. Critically revising the article: both authors. Reviewed submitted version of manuscript: both authors. Approved the final version of the manuscript on behalf of both authors: Phillips. Administrative/technical/material support: both authors. Study supervision: Phillips.

Supplemental Information

Videos

  Video 1. https://vimeo.com/1169901219.

  Video 2. https://vimeo.com/1162206041.

Correspondence

Nick Phillips: Leeds General Infirmary, Leeds, United Kingdom. nickphillips@nhs.net.