Bulsara, Ketan R. MD*; Kuzmik, Gregory A. MD*; Hebert, Ryan MD*; Cheung, Vincent MD‡; Matouk, Charles C. MD*; Jabbour, Pascal MD§; Hasan, David MD¶; Pepper, Joshua MBBS*
Blister-like aneurysms (BLAs) represent significant therapeutic challenges.1-5 BLAs often arise from the internal carotid artery (ICA), typically at nonbranching sites, and have thin walls and wide, poorly defined necks.6 These vascular lesions are particularly dangerous because they are prone to intraoperative and postoperative rupture.6 Such characteristics make them difficult to treat, and, as a result, BLAs are associated with worse outcomes than their saccular counterparts.7-10
The optimal treatment for BLAs is uncertain. Microsurgical treatment has a high risk of perioperative rupture, and endovascular coiling is usually unsuccessful owing to the wide neck of these aneurysms with a high risk of rupturing their delicate wall.1,10-13 Flow-diverting stents have been used to treat BLAs with good early results.14,15 However, flow-diverting technology has been associated with delayed complications, and the long-term safety of flow diverters has yet to be proven.16
Oversized open-cell self-expanding endovascular stents have been used successfully to treat BLAs by redirecting flow away from the aneurysm.17 Yet, this approach remains under investigation. The long-term results of this treatment modality remain to be elucidated.
In this article, we report 5 consecutive patients with BLAs treated with open-cell self-expanding stents as stand-alone therapy.
PATIENTS AND METHODS
We identified 5 patients with BLAs treated with self-expanding stents alone by the senior author (K.R.B.) between 2008 and June 2012 (Table). Medical records were reviewed for patient characteristics and clinical status at the time of hospital discharge. A modified Rankin score of ≤2 was considered a good outcome, whereas a modified Rankin score of ≥3 was considered a poor outcome. The most recent radiographic studies were reviewed to assess aneurysm occlusion status.
TABLE Summary of Cas...Image Tools
Procedures were performed by using transfemoral arterial access. In each patient, a single oversized open-cell self-expanding Neuroform3 stent (Boston Scientific, Natick, Massachusetts) was placed across the aneurysm neck without coil embolization. All patients were fully heparinized for the procedures, and 4 of 5 patients were loaded preoperatively with aspirin and clopidogrel. Antiplatelet therapy was continued postoperatively with aspirin alone. In 1 patient who required placement of a carotid stent, both aspirin and clopidogrel were used postoperatively.
All patients presented with acute subarachnoid hemorrhage (SAH) and were treated within 1 week of presentation. Three patients were male, and 2 were female. Mean age was 54 years (range, 37-64 years) (Table). Mean follow-up time was 13.6 months (range, 1 month to 4.5 years). Aneurysm locations were middle cerebral artery (n = 1), ICA (n = 2), and posterior cerebral artery (n = 2).
A 64 year-old woman presented with diffuse SAH from a ruptured 2-mm left middle cerebral artery bifurcation BLA (Figure 1A). She was subsequently treated with placement of a 3 × 15 mm self-expanding stent. Follow-up angiography on postoperative day 4 demonstrated complete occlusion of the aneurysm (Figure 1B). The patient was discharged from the hospital in good condition. A follow-up computed tomography angiogram (CTA) obtained 4.5 years later showed stable occlusion of the aneurysm (Figure 1C).
A 56-year-old man awoke with the worst headache of his life, nausea, and vomiting. He was found to have diffuse SAH from a ruptured 1.8-mm BLA of the left supraclinoid ICA (Figure 1D). The patient also had a dissection of the left cervical ICA. A 4 × 20 mm self-expanding stent was placed across the aneurysm neck, and a 9 × 50 mm Wallstent (Boston Scientific, Natick, Massachusetts) was used to treat the dissection. Immediately following intracranial stent placement, stagnation of blood flow within the aneurysm was noted. Some thrombus formation around the stent tines was also noted at this time, and this was treated with an abciximab bolus and infusion. Of note, this patient was not pretreated with aspirin or clopidogrel. Repeat angiography on postoperative day 7 demonstrated decreased aneurysm filling without the evidence of thrombosis (Figure 1E). Follow-up CTA 4.5 months later showed complete aneurysm occlusion (Figure 1F). The patient was discharged in good neurological condition.
A 63-year-old man acutely experienced the worst headache of his life and lost consciousness. Head CT revealed prepontine SAH. A subsequent angiogram confirmed the presence of a 1.5-mm blister aneurysm at the right P1/P2 junction (Figure 1G). This lesion was treated via deployment of a 3 × 15 mm self-expanding stent across the neck of the aneurysm. Immediately following stent placement, stagnation of blood flow within the aneurysm lumen was evident (Figure 1H). A magnetic resonance angiogram obtained 1 month postoperatively demonstrated complete aneurysm thrombosis. Follow-up CTA obtained 2.5 months postoperatively demonstrated no residual aneurysm filling (Figure 1I). The patient was discharged to a rehabilitation facility in good condition.
A 50-year-old woman experienced acute onset of the worst headache of her life and subsequently experienced a generalized tonic clinic seizure. CTA demonstrated SAH and a 1- to 2-mm outpouching of the medial supraclinoid right ICA in the area of the superior hypophyseal artery (Figure 2A), which was confirmed by diagnostic angiography. A self-expanding stent was placed across the affected vessel segment, with stagnation of blood flow immediately seen within the aneurysm. An attempt was made to place a second stent using a “stent-in-stent” technique to increase coverage of the aneurysm neck. In the process, however, the deployed stent became entangled in the microguidewire and was withdrawn into the femoral artery where it was retrieved. A second femoral puncture was accessed to redeploy a 3 × 15 mm stent across the aneurysm neck without incident. There was no angiographic evidence of injury to the cerebrovasculature, and the patient had no adverse sequelae from this complication. The patient was discharged neurologically intact and in good condition. CTA at 6 months follow-up demonstrated no residual aneurysm filling (Figure 2B).
A 37-year-old man with sickle cell disease acutely experienced the worst headache of his life and subsequently lost consciousness. A head CT revealed SAH. A CTA and subsequent traditional angiogram demonstrated a 3-mm lobulated aneurysm of the left posterior cerebral artery at the P1/P2 junction (Figure 2C). A 3 × 15 mm self-expanding stent was placed across the aneurysm neck, and moderate stagnation of blood flow within the aneurysm lumen was immediately noted (Figure 2D). CTA performed at 1 month follow-up demonstrated no residual aneurysm filling (Figure 2E). The patient was discharged neurologically intact and in good condition. This patient has been previously described in the medical literature.18
Overall, 1 patient (case 4) had a device-related procedural complication, but experienced no adverse clinical sequelae. A second patient (case 2) developed immediate intraprocedural stent thrombosis that resolved with intravenous abciximab. There were no other thromboembolic complications perioperatively or at follow-up. To date, no patients have experienced rehemorrhage of the stented aneurysm or required re-intervention for the aneurysm. At the time of most recent radiographic follow-up, there was no evidence of in-stent stenosis or thrombosis.
Five patients with ruptured BLAs were successfully treated with open-cell self-expanding stents. This treatment resulted in total aneurysm occlusion at follow-up and good neurological outcomes in all cases.
We observed 2 complications in our series, neither of which resulted in neurological sequelae. One patient (case 4) experienced a technical complication during an attempt to deploy a second stent by using the stent-in-stent technique. Although the patient experienced no adverse clinical outcomes as a result, this occurrence underscores the technical complexity of this approach. A second patient (case 2) experienced intraprocedural partial stent thrombosis that resolved with intravenous abciximab. This was likely secondary to inadequate antiplatelet therapy, because this patient was not preoperatively treated with aspirin or clopidogrel. Stent thrombosis is a known risk of monostenting therapy, particularly in the setting of insufficient platelet inhibition.17 In the setting of acute SAH and aneurysm stenting, preoperative antiplatelet therapy must be administered with caution and represents a balance between hemorrhagic and thromboembolic complications. Nonetheless, our experience demonstrates that antiplatelet agents can be administered safely and should be used to reduce thromboembolic risk.
The optimal treatment approach to BLAs remains unclear. Traditional microsurgical clipping can produce excellent clinical and radiographic results. However, the procedural risks are higher, with perioperative rupture rates between 30% and 40%.6-8 Intraoperative rupture secondary to surgical manipulation is of particular concern with BLAs because of their fragile walls that lack the normal intimal and adventitial layers of saccular aneurysms.7
Endovascular techniques for BLA treatment include stent-assisted coiling. Meckel et al3 describe this technique in 11 patients with BLAs. More than 80% of their patients had a good clinical outcome, 1 one reported death and 1 patient disabled. In 8 of their cases, there was no aneurysm recurrence; partial recurrence was noted in 2 patients. Nonetheless, coiling of a BLA has the inherent disadvantage of having to enter the delicate BLA lumen and risks aneurysm rupture.
As an alternative endovascular approach, interest and experience in treating BLAs with flow-diverting stents is increasing. A handful of case reports describe this technique.14,15,19-21 Early outcomes have been favorable. One series of 26 wide-necked or blister aneurysms treated with flow-diverting stents reported an 18% procedural complication rate.21 Most procedural complications were related to stent thrombosis. Additionally, 27% of patients experienced late (>30 day) complications of parent vessel occlusion, stent stenosis, or stent thrombosis. This resulted in the death of 1 patient (overall mortality rate, 5%). This series underscores the nagging concerns of delayed complications with the use of flow diverters, as have recently been documented in the treatment of larger aneurysms.16,22 Furthermore, because of the high risk of thrombosis, flow diverters in their current state mandate the use of dual-antiplatelet therapy, which carries additional hemorrhagic risks. As experience with this technology accumulates, we will better understand the role of flow-diverting stents in the treatment of BLAs, but, at present, the long-term safety of this treatment option remains uncertain.
Endovascular monostenting with open-cell stents offers a relatively new approach to secure ruptured aneurysms and prevent rebleeding. Such stents are traditionally used to prevent coil prolapse in wide-necked aneurysms. However, early studies in animal models have demonstrated that open-cell stents could effectively stagnate flow within aneurysm lumens without the introduction of coils.22-24 A number of case reports and small series have since been published describing this technique in the treatment of intracranial aneurysms with promising early results.17,25-31 Fiorella et al17 successfully treated 2 patients with ruptured BLAs with telescoping Neuroform stents. One patient had intraoperative stent thrombosis in the setting of insufficient antiplatelet therapy that was treated by intra-arterial abciximab, but recovered without deficit. Both patients remained neurologically intact at follow-up.
Open-cell self-expanding stents have the benefit of preserving parent vessel patency with minimal manipulation of the surrounding anatomy. This is of particular importance in the treatment of BLAs because of their fragility and propensity for rupture. Open-cell stents also have the advantage of necessitating only single-antiplatelet therapy postoperatively rather than the dual-antiplatelet maintenance required with flow-diverting stents. This is a particularly important distinction in the setting of acute SAH. In addition, there has been little evidence to suggest that open-cell stents are prone to the same delayed complications as flow-diverting stents, particularly when adequate antiplatelet therapy is administered perioperatively.
The limitations of this case series are the small number of patients and the lack of a control group. This impairs our ability to draw definitive conclusions from our results. However, given the relative paucity of data on this treatment modality in the literature, we believe that our experience in the treatment of 5 consecutive patients with these aneurysms provides insight into a readily available treatment option that should be in the armamentarium of all neurovascular specialists. Furthermore, in the era in which flow diverters are being used with increasing frequency, it is important to remember that the placement of oversized self-expanding stents for the treatment of BLAs is an option. At present, the advantages of open-cell stents are the availability of long-term complication rates and a better understanding of the optimal antiplatelet regimen required for their safe use.
The optimal treatment modality for small blister aneurysms remains uncertain, and such lesions often have poor clinical outcomes. Open-cell self-expanding stents represent an important new therapeutic option for these difficult-to-treat cerebrovascular lesions. Nonetheless, long-term data on their efficacy have yet to be elucidated, and further studies are needed to assess the durability of this treatment modality.
The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
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The authors report their clinical and radiographic outcomes for five patients with small ruptured, blister-like aneurysms (BLAs) treated primarily with the Neuroform 3 stent as monotherapy. As noted, these are difficult and often heterogeneous lesions with no clear optimal treatment. Endovascular treatment of BLAs has consisted of stent-assisted coiling, stent monotherapy and, more recently, the use of flow diverters. In this series, four of the five patients were treated preoperatively with aspirin and clopidogrel without complication. There was one device delivery complication and one case of intraprocedural in-stent thrombosis that resolved with administration of abciximab, but these complications did not result in permanent deficits. A mean follow-up of 13.6 months demonstrated stable occlusion of each lesion.
As underscored in the report, these are rare lesions and even within this small series, the aneurysms are quite heterogeneous. Therefore, while the outcomes in this series are good, practitioners must be aware of the potential for publication bias, as other centers with a negative experience for the same therapy would not be inclined or expected to publish their results. Perhaps more importantly, the authors astutely note the problems centered on antiplatelet management in these patients. While the experience in this series was relatively positive, the challenge of balancing hemorrhagic versus thromboembolic risks is very difficult in the setting of an aneurysm not immediately secured with the placement of a stent. It is not at all clear how long patients remain at risk following placement of a stent in this situation, and the issue is further complicated with the use of external ventricular drains or patients resistant to antiplatelet therapy.
Inevitably, the development of stent technology is a moving target for outcomes research, and long-term clinical and radiographic follow-up will be necessary. While the issues of platelet inhibition are likely to be similar between open-cell stents and flow diverters, the benefits of flow diversion for these lesions may prove to be more substantial and favored as first-line therapy. Regardless, because safe and effective treatments for these rare lesions have been elusive, this report provides some support for a treatment that should be widely available and therefore quite useful in a situation where there may be few, if any, viable alternatives.