Ruptured aneurysms at the distal superior cerebellar artery successfully treated by combining occipital artery–superior cerebellar artery anastomosis and endovascular therapy: illustrative case

Abstract

BACKGROUND

Distal superior cerebellar artery (SCA) aneurysms are rare and are treated using various treatment strategies. Treatment often requires parent artery occlusion, which raises concerns regarding the potential risk of ischemia in the distal territory.

OBSERVATIONS

An 81-year-old woman presented with subarachnoid hemorrhage. Diagnostic cerebral angiography revealed two tiny distal SCA aneurysms. Because significant ischemic damage following parent artery occlusion was concerned, two bypasses between the occipital artery and SCA branches were first performed with the patient in the prone position in a hybrid operating room. Each aneurysm was successively treated in the same position with endovascular internal trapping and intra-aneurysmal embolization. After adequate hemostasis was confirmed, the wound was closed. Both aneurysms were successfully occluded without symptomatic ischemic complications.

LESSONS

This combined surgical and endovascular approach would be helpful in cases with notable concerns regarding ischemia after sacrificing the parent artery.

Distal superior cerebellar artery (SCA) aneurysms are quite rare, and various treatment strategies for these entities have been described in the literature.^1–7 The fusiform morphology of many distal SCA aneurysms is one factor influencing the diversity in treatment options. Although parent artery sacrifice is a reasonable option if sufficient collateral circulation is present, poor collateral flow may necessitate bypass surgery to prevent a large amount of ischemia.^6,7

In this report, we describe a case of two tiny distal SCA aneurysms presenting with subarachnoid hemorrhage (SAH). Because parent artery occlusion could have been followed by major ischemic damage, two bypasses between the occipital artery (OA) and SCA branches distal to the two aneurysms were performed first. Both aneurysms were then successively occluded by endovascular internal trapping and intra-aneurysmal embolization in a hybrid operating room. To our knowledge, this is the first report describing the treatment of distal SCA aneurysms by a combined surgical and endovascular approach, and we hope that these findings will provide new insights into the treatment options for distal SCA aneurysms.

Illustrative Case

An 81-year-old woman with disturbance of consciousness was transferred to our hospital. On admission, her Glasgow Coma Scale score was 14. No other neurological deficits were noted. Computed tomography revealed a localized SAH from the cerebellomesencephalic cistern to the upper surface of the left cerebellum and a slight intraventricular hematoma in both lateral ventricles (Fig. 1A). Diagnostic cerebral angiography revealed two tiny aneurysms in the left distal portion of the SCA (Fig. 1B–D). The aneurysm located proximally in the cerebellomesencephalic segment was a wide-neck saccular aneurysm. The other distal aneurysm in the cortical segment was fusiform. We could not initially determine which aneurysm was ruptured.

FIG. 1.

Admission computed tomography (A) shows SAH from the cerebellomesencephalic cistern to the upper surface of the left cerebellum. Computed tomography angiography (B) and cerebral angiography (C) show two tiny aneurysms on the distal portion of the left SCA (arrows and arrowheads). Three-dimensional rotation angiography (D) shows a wide-neck saccular aneurysm at the cerebellomesencephalic segment (arrow) and a fusiform aneurysm at the cortical segment (arrowhead).

Endovascular treatment of both SCA aneurysms was planned first. Parent artery occlusion was required for the distal fusiform aneurysm. Intra-aneurysmal embolization was first considered for the proximal saccular aneurysm; however, sacrificing the parent artery would potentially be required because the aneurysm had a wide neck. The left SCA was well developed and covered wide perfusion areas in the cerebellum; the left posterior inferior cerebellar artery and anterior inferior cerebellar artery were not sufficiently developed to cover the SCA perfusion area (Fig. 1B and C). Therefore, simple parent artery sacrifice at the portion of the proximal aneurysm in addition to the distal aneurysm would likely have resulted in substantial ischemic damage (Fig. 1B). To prevent large ischemia, two bypasses between the two SCA branches and the OA were planned before endovascular treatment. To bypass one OA to the two SCA branches, a superficial temporal artery (STA)-free graft was planned to connect the side of the OA to one of the two SCA branches (Fig. 2A). A hybrid operating room was chosen to allow simultaneous surgical and endovascular treatments.

FIG. 2.

Schematic of bypass surgery (A) and intraoperative view (B) after completion of anastomosis. The lateral branch of the SCA (double arrows) was directly anastomosed to the OA (arrow), and the medial branch (double arrowheads) was connected to the OA by interposing the STA-free graft (arrowhead). Superselective angiography (C) of the left SCA revealed both aneurysms. The distal fusiform aneurysm was occluded by internal trapping of the parent artery (D), and the proximal wide-neck saccular aneurysm was occluded by intra-aneurysmal embolization (E). Angiography of the left common carotid artery (F) confirmed patency of the bypasses (arrowheads). Distal territories of the medial and lateral branches were perfused via OA (arrows). AN = aneurysm; BA = basilar artery.

Under general anesthesia, before craniotomy, the patient was secured in the supine position to prepare for endovascular treatment and harvest the STA-free graft. A 6-Fr Super Arrow-Flex Sheath (Teleflex) was inserted from the right brachial artery toward the right subclavian artery. Subsequently, the left STA-free graft was harvested under a microscope. After these procedures, the patient was placed in a prone position. The left OA was dissected from suboccipital muscles. A suboccipital craniotomy was performed, and two cortical branches distal to the aneurysms were identified on the suboccipital surface of the left cerebellar hemisphere. The lateral cortical branch was anastomosed to the OA directly, and the medial cortical branch was connected to the OA by interposing the STA-free graft (Fig. 2A and B).

After confirming the patency of bypasses by common carotid artery angiography, heparin was administered intravenously, and endovascular treatment was performed with the patient in the same prone position. A 6-Fr Cerulean catheter (Medikit Co.) was advanced to the right vertebral artery, and a 4.2-Fr Fubuki catheter (Asahi Intecc Co.) was advanced to the basilar artery under fluoroscopic guidance. An SL10 microcatheter (Stryker) was first advanced to the distal fusiform aneurysm, and the aneurysm was occluded by internal trapping of the parent artery using Axium coils (Medtronic). The microcatheter was then drawn back to the proximal saccular aneurysm, and the aneurysm was embolized using Axium coils (Medtronic) (Fig. 2C–E). Despite our concerns, coil embolization of the proximal aneurysm was completed without sacrificing the parent artery. After confirming the patency of the bypasses by common carotid artery angiography, adequate hemostasis was confirmed, and the wound was closed (Fig. 2F).

We confirmed the patency of the bypass using magnetic resonance imaging on postoperative day 2 without any symptomatic cerebral infarction. The patient recovered clinically after rehabilitation and could walk independently at the 6-month follow-up.

Discussion

Observations

Distal SCA aneurysms are reported to be quite rare, representing no more than 0.2% of cerebellar aneurysms.¹ Although surgical trapping of the parent artery has traditionally been the first choice for the treatment of distal SCA aneurysms, an increasing number of case reports in the past decade have described endovascular approaches because of the better occlusion and lower complication rates.^2–4 Moreover, the endovascular approach can be more easily performed for parent artery occlusion in one session in cases with two aneurysms, similar to the present case.

Because many distal SCA aneurysms are fusiform, the parent artery often has to be sacrificed. Although the distal segment of SCA can often be sacrificed with little clinical consequence, there are sometimes notable concerns regarding insufficient collateral flow after simple parent artery occlusion, as in the present case. However, there is no reliable test to predict the extent of ischemia after sacrificing the parent arteries of such distal aneurysms. Thus, parent artery occlusion by either direct surgery or endovascular procedures is sometimes accompanied by a potential risk of ischemia. To avoid ischemia following parent artery occlusion, combined bypass surgery has been attempted.^6,7 Although there are only a limited number of case reports, fusiform aneurysms at the distal segment of the SCA can be managed with OA-SCA anastomosis.⁶ Because the two aneurysms were located in different segments in our case, direct surgical trapping following bypass surgery was not feasible. Therefore, we used a combination of surgical and endovascular approaches. By anastomosing the two SCA branches distal to the aneurysms with the OA, the retrograde flow from the OA could provide sufficient blood flow to prevent ischemia after parent artery occlusion. To provide the two OA bypasses, we used a free graft harvested from the STA, as described.

One of the problems in combined surgical and endovascular approaches is the scheduling of the two treatments. In our case, a single-stage treatment in a hybrid operating room was chosen. A major concern associated with combined treatment is hemorrhagic complications caused by heparinization. The potential for incidence of intracranial hemorrhage, such as subdural hematoma, is a concern associated with two-stage treatments performed soon after bypass surgery. In this regard, single-stage treatment is considered beneficial because adequate hemostasis can be confirmed before wound closure after endovascular treatment.

Although our combined treatment strategy provided new insights, it had several limitations. First, endovascular treatment in the prone position is a relatively complex procedure and not suitable for cases involving difficult access. Second, an additional approach might be restricted in cases involving intraprocedural complications, such as embolic occlusion of vessels. These risks should be balanced with their benefits.

Lessons

A combined surgical and endovascular approach is an effective treatment option for distal SCA aneurysms when there are notable concerns regarding ischemia following parent artery occlusion.

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: Ogura, Hatano. Acquisition of data: Ogura, Hatano, Kitamura, Yamada. Analysis and interpretation of data: Hatano. Drafting the article: Ogura, Hatano, Koyanagi. Critically revising the article: Hatano, Koyanagi. Reviewed submitted version of manuscript: Hatano, Koyanagi. Approved the final version of the manuscript on behalf of all authors: Ogura.