Beneficial Remodeling of Small Saccular Intracranial Aneurysms after Staged Stent Only Treatment: A Case Series

Transcription

1 Beneficial Remodeling of Small Saccular Intracranial Aneurysms after Staged Stent Only Treatment: A Case Series Eric M. Nyberg, MD,* and Theodore C. Larson, MD Background: We evaluated the effect of stent alone treatment for small intracranial aneurysms that were not amenable to coil embolization without prior stent reconstruction. Methods: This case series was conducted in the neurosurgical service at a tertiary care hospital in Denver, Colorado. Nine patients were electively treated for intracranial aneurysms. All patients had a single low porosity stent reconstruction device placed across the neck of a small intracranial aneurysm. The main outcome measures were changes in aneurysm size and parent vessel morphology during follow-up. Results: Nine patients underwent stent alone treatment for unruptured intracranial aneurysms. The mean follow-up period was 9.6 months (range 6-17 months). There were no cases of periprocedural morbidity or aneurysm rupture during follow-up. All aneurysms decreased in size, and 3 of 9 aneurysms were gone at follow-up. In addition, at follow-up all parent vessels demonstrated straightening about the aneurysm site. Conclusions: Beneficial remodeling with a decrease in the size of small intracranial aneurysms may be seen after treatment with a single stent alone, particularly if the aneurysm arises at an arterial bend or bifurcation. This phenomenon may be related to a degree of straightening of the parent artery, improving hemodynamic conditions about the aneurysm site. Key Words: Intracranial aneurysm stent vascular remodeling. Ó 2014 by National Stroke Association From *Vista Radiology, Knoxville, Tennessee; and Intermountain Neurosugery, St. Anthony s Hospital, Denver, Colorado. Received May 30, 2012; revision received July 10, 2012; accepted September 19, Address correspondence to Eric M. Nyberg, MD, Vista Radiology, 2001 Laurel Avenue, Knoxville, TN ericmnyberg@ gmail.com /$ - see front matter Ó 2014 by National Stroke Association Endovascular treatment of intracranial aneurysms (IAs) often includes the placement of a Neuroform stent (Stryker, Kalamazoo, MI) or Enterprise vascular reconstruction device (VRD; Codman Neurovascular, Raynham, MA), particularly if the aneurysm has a wide neck or unfavorable dome to neck ratio. Stent reconstruction devices were originally designed to create a frame at the neck that prevents coil herniation 1 ; however, other mechanisms of aneurysm treatment with these devices have been investigated, including the creation of flow disruption or diversion and the provision of scaffolding for re-endotheliazation. 2 Computational flow dynamics analysis has suggested that stent reconstruction may reduce wall shear stress (WSS) and aneurysmal inflow. 3-5 We present 9 cases of staged, elective aneurysm treatment in which placement of a stent reconstruction device alone resulted in straightening of the parent artery with subsequent angiographic remodeling and decrease in aneurysm size. In each of these cases, at the time the patients returned for coiling, the aneurysm had decreased significantly in size and coiling was not attempted. Staging treatment in this manner may allow the aneurysm to shrink in some patients, thereby precluding the need to expose them to the risk of coil embolization. Methods Subjects and Data Collection Under an institutional review board approved protocol, a review of our institutional database yielded 45 aneurysms,7 mm that underwent endovascular treatment between July 2010 and June Of these, Journal of Stroke and Cerebrovascular Diseases, Vol. 23, No. 1 (January), 2014: pp 80-85

2 SMALL SACCULAR IAS AFTER STAGED STENT ONLY TREATMENT 81 aneurysms were treated with coil embolization alone, including 6 aneurysms treated in the setting of subarachnoid hemorrhage. Three were treated with stent and coil embolization and 9 were treated with stent remodeling alone. Therefore, 9 of 39 (23%) electively treated small aneurysms during this period underwent presumed staged treatment with stent remodeling; these cases are described herein. These 9 cases were performed in 6 patients (3 men and 3 women) who were between 42 and 70 years of age (average 57 years; Table 1). All cases were elective, but 2 patients had previously suffered subarachnoid hemorrhage from other, previously treated aneurysms, and 2 other patients reported remote histories suspicious for a sentinel bleed. A staged approach to treatment was preferred in these patients to allow the stent to become endothelialzed, reducing the risk of stent migration along curvatures and allowing for increased stability during coil embolization. All patients were premedicated with dual antiplatelet therapy consisting of 75 mg of clopidogrel and 325 mg of aspirin per day for 5 days before treatment. Clopidogrel was continued for 1 month postprocedure, and aspirin was continued indefinitely. Of the 9 aneurysms, 2 were located at the anterior communicating artery complex, 4 were located in the intracranial vertebral arteries, 1 at the superior cerebellar artery origin, and 1 on the posterior cerebral artery P2 segment. All IAs were small (,7 mm). All patients presented for staged elective aneurysm treatment and were treated with either an Enterprise VRD (4 cases), Neuroform stent (2 cases), or a Wingspan stent (Stryker; 3 cases). Volumetric aneurysmal filling was estimated using Angiosuite software (Cascade Medical LLC, Knoxville, TN). Indications for treatment included history of subarachnoid hemorrhage from other, previously treated aneurysms (cases 7, 8, and 9); recurrence of previously ruptured and coiled aneurysm (case 6); and history suspicious for sentinel bleed several weeks earlier (case 1). Cases 2, 3, 4, and 5 were in patients with multiple aneurysms, potentially putting them at increased risk of hemorrhage. Discussion regarding the use of Humanitarian Device Exemption devices was part of the consent process for each patient, and additional device-specific consent forms were completed per the institutional review board protocol. A Wingspan stent was used in cases with perianeurysmal stenosis of the parent artery. Description of Technique All procedures were performed under general anesthesia. Systemic heparinization was initiated before stent deployment with the goal of maintaining the activated clotting time at 2 to 3 times the baseline. A 6-Fr Envoy guide catheter (Codman Neurovascular) was placed in the distal cervical internal carotid artery for the anterior communicating artery aneurysms or the proximal cervical vertebral artery for posterior circulation aneurysms. Working projections were obtained from reconstructed 3-dimensional rotational angiography in most cases. Under roadmap conditions, a Prowler Select Plus catheter (Codman Neurovascular, Raynham, MA), Neuro Renegade Hi Flo catheter (Stryker, Kalamazoo, MI), or Wingspan system was advanced into the parent artery distal to the neck of the aneurysm over a inch Synchro wire. The stent reconstruction device was then advanced across the neck of the aneurysm and deployed according to the manufacturer s guidelines. Final control angiography was performed and all catheters were removed. Hemostasis was obtained with a closure device. All patients returned 4 to 8 weeks later for coil embolization; however, diagnostic angiography revealed that the aneurysms were found to have decreased in size such that coiling would have been challenging if not impossible. Therefore, they were scheduled for follow-up Table 1. Aneurysm size pre and post stent reconstruction Case no. Age (y) Location Device* Largest diameter (mm)/volume (mm 3 ) Follow-up interval (months) Result at follow-up Volumetric decrease 1 56 IC vertebral Wingspan 6.2/ Complete resolution 100% 2 54 IC vertebral Enterprise 3.2/ / % 3 54 IC vertebral Enterprise 3.3/ / % 4 70 IC vertebral (proximal) Wingspan 2.4/ / % 5 70 IC vertebral (distal) Wingspan 5.9/ Complete resolution 100% 6 42 Ant comm complex Enterprise 4.0/ / % 7 63 Ant comm complex Enterprise 2.6/ / % 8 59 Superior cerebellar Neuroform 2.2/ / % 9 59 Postcerebral P2 Neuroform 1.2/ Complete resolution 100% Abbreviations: Ant comm, anterior communicating; IC, Intracranial. *Wingspan and Neuroform stents are manufactured by Stryker (Kalamazoo, MI). The Enterprise vascular reconstruction device is manufactured by Codman Neurovascular (Raynham, MA).

3 82 catheter angiography at 6 months to monitor aneurysm changes. Illustrative Cases Case 1 The angiogram Fig 1A shows a 42-year-old man at 12 months postcoiling of a ruptured aneurysm arising from the anterior communicating artery complex; there is a 4.0-mm recurrence at the neck (Raymond 2). The anterior communicating artery complex in this patient gave rise to an azygous pericallosal artery, and the bilateral callosomarginal arteries had anomalous proximal origins. An Enterprise VRD was placed across the neck of the aneurysm from the right A1 to the distal A2 segment of the azygous pericallosal artery. Six weeks later, aneurysm patency had regressed and coiling was deferred. Vessel curvature at the A1 A2 junction had greatly diminished after VRD placement. There is mild stenosis near the distal portion of the VRD (Fig 1B). Case 2 A 70-year-old man with multiple vascular risk factors presented for evaluation of an unruptured 5.9-mm left vertebral IA. A Wingspan stent was used for stent reconstruction in this case because the aneurismal segment was associated with atherosclerotic stenosis and both calcified and noncalcified plaques on the computed tomographic angiogram (not shown; Figs 2A and 2B). The patient returned 7 weeks later for coil embolization, whichwasdeferreduponreevaluationoftheia,which had greatly diminished in size and had a height of,1 mm (Figs 2C and 2D). The stent straightened the curvature of the vessel near the proximal neck, best seen on the lateral view (Figs 2B and2d). Results All devices were placed uneventfully without complications such as thromboemboli, aneurysm rupture, or parent vessel dissection. Immediate post stent placement control angiography revealed subjective decreased aneurysmal flow in all cases. All patients were asymptomatic perioperatively and remained asymptomatic through the follow-up period (6-17 months). At follow-up, all patients showed significant improvement, with decreases in volumetric filling ranging from 23% to complete resolution (Table 1). At no point was there an increase in size. In addition, parent vessel straightening occurred as a result of stent device placement in all cases. Discussion E.M. NYBERG AND T.C. LARSON Stent reconstruction devices, including Neuroform and Enterprise, are often used to aid or augment elective treatment of IAs, particularly those with challenging characteristics including unfavorable dome to neck ratios. Stent reconstruction devices were originally designed for the mechanical benefits of preventing coil herniation and enabling increased packing density. However, other benefits may be both hemodynamic and physiologic (i.e., through flow diversion, reduced WSS, and the provision of a scaffolding to support endothelialization across the aneurysm neck). We present 9 cases in which vascular reconstruction was performed for staged, elective treatment of IAs, and in all cases within 4 to 8 weeks the parent vessels had straightened and the aneurysms had decreased in size such that it was felt that additional coiling was no longer necessary. We surmise that stent reconstruction alone created favorable hemodynamic changes enabling aneurismal shrinkage and, potentially, reendotheliazation and healing. This may have been accomplished both directly by deflection and impedance of flow into the aneurysm and provision of a scaffold by the device struts, as well as indirectly by straightening of the vessel, thereby decreasing hemodynamic stress at the neck, altering anuerysmal inflow and redirecting flow away from the aneurysm. Flow diversion represents an important component of endovascular aneurysm treatment and constitutes the basis of the new Pipeline Embolization Device (PED; ev3/ Chestnut Medical, Menlo Park, CA) that was recently approved by the US Food and Drug Administration for the Figure 1. Internal carotid artery angiogram in (A) demonstrates a 4.0 mm recurrence at the neck of a previously coiled anterior communicating artery aneurysm. Stent reconstruction was performed with an Enterprise VRD. Pre coiling angiogram performed six weeks later (B) demonstrated approximately 65% volumetric decrease in aneurysm size and straightening of the parent artery across the neck.

4 SMALL SACCULAR IAS AFTER STAGED STENT ONLY TREATMENT 83 Figure 2. AP (A) and oblique (B) vertebral angiography demonstrating a distal vertebral artery aneurysm located at a bend in the rather tortuous distal vertebral segment. A Wingspan stent was placed across the neck of the aneurysm. Pre coiling angiogram in AP (C) and oblique (D) projections performed seven weeks later showed substantially complete resolution of the aneurysm and straightening of the tortuous segment. endovascular treatment of large or giant wide-necked IAs in the petrous to superior hypophyseal segments of the internal carotid artery, but has also been used in nonsaccular aneurysms of the posterior circulation. 6 However, this device is not currently indicated for treatment of small aneurysms or aneurysms arising from more distal vessels. In contrast, stent-assisted coiling has been reported in vessels as small as 1.0 mm in diameter. 7 The theoretical effect of flow diversion exerted by the Enterprise VRD has been simulated using computational flow dynamics. 3 Results of these simulations suggest favorable hemodynamic changes, including decreased flow velocity within the aneurysm, increased stasis, and decreased WSS. Similar studies have been performed with the Neuroform stent using particle flow velocitrometry, and the results are comparable. 4,5 Several case reports and case series have documented the potential of single and multiple telescoping VRDs/stents to successfully treat dissecting fusiform aneurysms in the posterior circulation The results of these studies are based on the effects of the overlay of various permutations of metal to vessel surface ratios and show increased benefits as that ratio increases. Previous authors have reported success with stent only treatment of aneurysms, noting shrinkage or occlusion on follow-up angiography. Fiorella et al 11 reported stent monotherapy for blister-like aneurysms with good success and vascular remodeling in 90% of patients at follow-up. Cekirge et al 12 recently demonstrated shrinkage of middle cerebral artery bifurcation and basilar summit bifurcation aneurysms with Y-stent bifurcation remodeling, and Yavuz et al 13 reported treatment of side wall aneurysms with Wingspan stents alone. Nyberg et al 14 recently described 2 cases in which the placement of 2 overlapping Neuroform stents in the basilar artery resulted in the disappearance of tiny, previously ruptured aneurysms arising from basilar artery perforators. These changes presumably resulted from beneficial changes in the parent artery hemodynamics. 14 Patients in our series, by comparison, presented with aneurysms at branch points or along vascular curvature.

5 84 Therefore, another strategy for ameliorating the hemodynamic stresses on the vessel wall may be to change the morphologic relationship between aneurysm and the parent vessel. IAs commonly arise at bifurcation and branch points, and Meng et al 15 showed how the combination of high WSS and high WSS gradients, found near bifurcations, lead to aneurysm development. 15 Other computational flow dynamics studies have shown how elevated WSS and their gradients can lead to aneurysm development at vessel branch points and curvatures. 16,17 The cases presented here suggest that these effects may be reversible through parent vessel straightening and presumably with diminished aneurismal WSS and WSS gradients. Finally, despite recently published data suggesting that the safety profile of coiling has improved in recent years, especially when performed at high volume centers, 18,19 exposing patients to the risk associated with elective coil embolization of small, unruptured IAs remains controversial. 20,21 Data from the International Study of Unruptured Intracranial Aneurysms 2 suggest that the 5-year risk of rupture of incidentally discovered aneurysms,7 mm in size in the anterior circulation is very small, 22 and that the risk of intraprocedural hemorrhage may be higher during coil embolization of small aneurysms. 23 However, clinical application of these data is challenging given the high prevalence of small aneurysms in several series of ruptured cases, and other metrics have been published in order to provide better risk stratification. 24,25 Patients and neurointerventionists alike are often uncomfortable foregoing treatment, particularly when there has been a history of subarachnoid hemorrhage in a different aneurysm, as seen in several of our cases. Therefore, although vascular reconstruction alone with devices other than primary flow diverters is not an approved or recommended definitive treatment of IAs, the hemodynamic benefits of this staged approach may spare some patients the added risk associated with coil embolization. In addition, these benefits may increase as future devices with smaller cell size and increases in metal to surface ratio become available. Our study was limited by the retrospective design, small sample size, and short-term angiographic follow-up. In conclusion, we present a small series of patients who experienced a decrease in aneurysm size after stent reconstruction alone in the course of staged, elective aneurysm treatment. Improving hemodynamic conditions by changing parent artery morphology may play a role in the benefits of stent reconstruction. Potential mechanisms that may lead to aneurysm healing from vascular reconstruction alone deserve additional research. References 1. 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