Case report

An individual who had progressive dysphagia over the course of a few months was referred to our institution with an unruptured giant aneurysm identified on non-invasive imaging. The past medical history included hypertension, abdominal aortic aneurysm, hypothyroidism, hyperlipidemia and depression. Cranial nerve dysfunction was not appreciated on the clinical examination. A diagnostic angiogram showed a giant cavernous internal carotid artery (ICA) aneurysm (figures 1A,B and 2A,B) with flow directed into the aneurysm dome. A balloon occlusion test was performed to assist in the treatment decision making process. The patient failed the occlusion test, and carotid artery sacrifice was therefore not considered a therapeutic option. After a thorough discussion of options with the patient and family, including continued radiographic surveillance and endovascular and microsurgical approaches, endovascular stent assisted coiling was chosen as the best primary treatment option for this patient. Surgical occlusion of the carotid artery with an extracranial–intracranial bypass was reserved for possible endovascular therapy failure.

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Figure 1

Right internal carotid artery angiogram showing giant aneurysm before (A, B) and after (C, D) coiling.

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Figure 2

Magnified view of the neck and parent vessel (A, B) showing the inlet and outlet vessels (*) and the acute angle between these vessels at the aneurysm neck. (C) Microwire access of the distal vessel with redundant coils in the aneurysm sac. C2–C4 show the balloon anchor in the distal vessel and release of the redundant loops (arrows) to form a wire bridge at the aneurysm neck to facilitate stent assisted coiling.

Technique

Transfemoral access was obtained with a 6 French sheath. A 6 French Envoy guide catheter (Codman Neurovascular, Raynham, Massachusetts, USA) was positioned in the right ICA. The patient was heparinized with 3500 units of heparin, resulting in an activated coagulation time of 297 s. Navigation of the microcatheter across the neck of the aneurysm to access the distal vasculature was difficult because of the location, large size of the aneurysm and considerable inflow jet into the aneurysm dome away from the distal parent vessel. Additionally, an adequate buttress was not present to maneuver a microwire or catheter into the distal vessel because the wide aneurysm neck was located along the outer curvature of the ICA. Distal access failed after multiple attempts using microcatheters of variable stiffness and with different tip shapes in combination with different microwires (figure 3A–E).

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Figure 3

Illustration of the balloon anchor technique. (A) A fusiform aneurysm with different inlet and outlet flow directions. This makes directing the microwire into the distal parent vessel difficult. (B) The microwire is allowed to follow the inlet flow and curve around in the aneurysm to exit at the outlet. (C) A balloon is inflated in the distal parent vessel to serve as an anchor, and the wire is slowly pulled to bridge the neck of the aneurysm. (D) A stent is placed across the aneurysm neck. (E) Stent assisted coiling of the aneurysm.

After multiple failed attempts, the microwire was allowed to follow the flow into the aneurysm, looping around the aneurysm dome to reemerge from the aneurysm neck in an orientation that allowed for distal parent vessel access (figure 2C1). This was accomplished with a Synchro2 standard microwire (Boston Scientific, Natick, Massachusetts, USA) advanced through an Excelsior SL-10 microcatheter (Boston Scientific). The Synchro2 wire was then removed, and an Asahi Prowater exchange length microwire (Abbott Vascular Devices, Abbott Park, Illinois, USA) was placed in the distal middle cerebral artery vasculature. The hydrophobic tip of the Asahi Prowater yielded additional anchoring of the microwire during exchange of the microcatheter for a 3.5×15 mm over-the-wire Gateway balloon (Boston Scientific). The Gateway balloon was inflated in the proximal M1, and the shear force generated against the endothelial wall was used as an anchor point to slowly unravel the microwire from within the aneurysm dome. This allowed the microwire to be straightened into the parent vessel and recreated a virtual neck (shortest distance between the aneurysm inlet and outlet) across the aneurysm (figure 2C2–C4). The Gateway balloon was deflated and exchanged for a Prowler select plus microcatheter (Codman Neurovascular) and a 4.5×28 mm Enterprise stent (Codman Neurovascular) was deployed across the aneurysm neck in a standard fashion (figure 2B). A 45° Excelsior 1018 microcatheter (Boston Scientific) and a Synchro2 standard microwire were then used to catheterize the aneurysm. The aneurysm was embolized with multiple Trufill coils (Codman Neurovascular) to obtain >95% coil embolization of the aneurysm sac (figure 1C). Catheters were removed in a standard fashion. A Mynx closure device (AccessClosure, Inc, Mountain View, California, USA) was used to remove the sheath and close the arteriotomy. The patient was then transferred from the angiography suite in a condition the same as at neurologic baseline; there was no sign of groin hematoma and distal pulses in the leg were preserved. The patient remained neurologically intact throughout the hospital stay and was discharged 2 days after the procedure. The 6 month follow-up angiogram demonstrated 100% coil occlusion (figure 1D).

Discussion

Giant intracranial aneurysms are a rare entity, comprising approximately 5% of all intracranial aneurysms.1 Giant saccular aneurysms, as in the case presented here, have a predilection for locations with high hemodynamic stresses. The natural history of these aneurysms is quite ominous.2 3 Drake and Peerless4 reported mortality rates of 66% at 2 years and >80% at 5 years among patients with untreated giant aneurysms. The treatment of these lesions remains a challenge for both surgical and endovascular techniques.3–16 Surgical options for giant aneurysm treatment include clip reconstruction, parent vessel sacrifice and trapping with or without bypass. The objective of these methods is exclusion of the aneurysm from the normal vasculature and reduction of mass effect. Morbidity rates of 26–35% and mortality rates of 7–21% have been reported for open surgical treatment of giant aneurysms.4 9 10 14 17 18

Giant aneurysms are one of the most difficult lesions to treat endovascularly because of their size, flow characteristics, wide or complex necks, friable parent vessels, involvement of perforators and high recurrence rates. As previously outlined by Parkinson et al,19 endovascular techniques can be thought of as either deconstructive strategies (exclusion of the aneurysm and parent vessel from the cerebral circulation) or reconstructive strategies (exclusion of the aneurysm only). The reconstructive approach requires distal access and can pose a significant technical challenge due to strong jets of blood flow that are directed into the aneurysm dome.

Endovascular approaches are preferred when there is perforator involvement, heavy calcification, deep location, proximity to eloquent brain, anticipated surgical morbidity, lack of symptoms from mass effect, need for bypass after surgical occlusion and if there is fairly favorable geometry for stent assisted coiling. Parkinson et al19 reviewed the current endovascular literature and reported rates of morbidity (27–38%) and mortality (7.5–9.6%) that were similar to those for surgical techniques but were associated with less successful occlusion rates. In a recently reported retrospective review of 39 consecutive giant intracranial aneurysms treated endovascularly, an average of 1.9±1.1 sessions were required to treat each aneurysm and >95% occlusion was achieved in 64% of aneurysms at the time of the last angiographic follow-up, with parent vessel preservation maintained in 74% of cases.1 The cumulative per patient mortality rate was 16% and morbidity was 32%. Other authors reported mortality rates of 24–27% and morbidity rates of 12–42%.6–8 11–13 15 16 Complications of endovascular treatment include poor occlusion rates secondary to delayed coil compaction, coil herniation, stent occlusion or thrombus formation, and late rebleeding.

Recently, there has been increasing interest in using a flow diverter stent for giant aneurysms with a segmental defect in the parent vessel for parent vessel reconstruction. The Pipeline embolization device (ev3, Irvine, California, USA), a CE mark approved device, is being evaluated for safety and efficacy in trials in the USA and has shown promising results.20 The Silk stent (Balt, Montmorency, France) is another CE mark approved flow diverter stent that is being tested in Europe for the treatment of intracranial aneurysms. When the use of these devices increases, more giant aneurysms will be treated with endovascular means and advanced techniques of achieving safe distal access will become important for decreasing the morbidity and increasing the success of these procedures.

The patient reported here failed the balloon occlusion test, and a bypass procedure would have been necessary to surgically occlude this aneurysm. To avoid this added morbidity, a decision was made to attempt to treat this patient with stent assisted coiling. Significant difficultly was encountered in crossing the neck of this lesion because of the constant redirection of the microwire and microcatheter into the aneurysm dome. Various strategies were attempted to gain distal access, none of which was successful. To avoid progressive use of stiffer microwire–microcatheter combinations that increase the potential for dissection or aneurysm rupture, a soft microwire was allowed to follow the preferential path of the flow into and around the aneurysm, re-emerging at the neck, thereby allowing navigation into the distal parent vessel. Once distal access was obtained, the next technical challenge was to uncoil the loops of microwire from within the aneurysm in order to facilitate stent deployment. A balloon with a well defined radial dimension (ie, the Gateway balloon) was inflated in the distal parent vessel, which produced gentle traction while tension was placed on the microwire to remove the redundancy of the microwire loops from within the aneurysm. This novel technique could be used for other circumstances in which local hemodynamic forces limit navigation into distal parent vessels.