GENERAL SCIENTIFIC SESSION III: OUR FUTURE IS NOW!: Chapter 10
Flow diversion as a treatment concept for giant and wide-necked intracranial aneurysms has become a reality with Food and Drug Administration approval of the Pipeline embolization device (PED; Covidien Neurovascular, Irvine, California).1 When deployed over the neck of an intracranial aneurysm, this stentlike device discourages flow within the aneurysm and results in a gradual involution of the aneurysm. After a well-designed trial2 showed acceptable perioperative morbidity (5.6% perioperative incidence of major ipsilateral stroke or neurological death) and good occlusion rates (82% occlusion at 180 days and 86% occlusion at 1 year) for previously difficult-to-treat intracranial aneurysms, the Food and Drug Administration approved use of the PED for treatment of intracranial aneurysms of the internal carotid artery (ICA) at or proximal to the superior hypophyseal segment measuring > 10 mm in the greatest dimension.1 This treatment strategy now represents our treatment option of choice for large, wide-necked, and fusiform ICA aneurysms, which were conventionally the most difficult to treat with surgical or endovascular techniques.
To demonstrate this new technology, 2 live cases were presented from the Gates Vascular Institute in Buffalo, New York, at a plenary session during the 2012 Congress of Neurological Surgeons Annual Meeting.
THE DEVICE AND DELIVERY TECHNIQUE
The PED is a braided mesh cylinder consisting of 48 filaments, each composed of 25% platinum and 75% nickel-cobalt chromium alloy (Figure 1). At its nominal configuration, metallic coverage of the parent vessel is 30% to 35%. This is sufficient to cause a diversion of flow away from the aneurysm fundus; ultimately, occlusion of the aneurysm after flow stasis, aneurysm thrombosis, and endoluminal reconstruction occur. The PED has a relatively low radial force; for this reason, we typically choose a device the size of the proximal parent vessel or slightly larger (available diameters are 2.5-5.0 mm in 0.25-mm increments). Apposition of the PED to the parent vessel, particularly proximal to the aneurysm, will help ensure appropriate diversion of flow and endoluminal reconstruction of the vessel, encouraging complete obliteration of the aneurysm while allowing patency of arterial perforators. We choose a PED length sufficient to cover the aneurysm neck and extend approximately 5 to 10 mm proximal and distal to the aneurysm.
The PED is among the most difficult intracranial devices to deliver because of the friction created during delivery and its malleable nature requiring careful deployment. Bringing the device into position distal to the aneurysm before deployment requires a microcatheter with a 0.027-in inner diameter, which we deliver through a 6F or larger guide catheter placed as close as possible to the aneurysm. Because a significant amount of friction is encountered during PED delivery, either a relatively stiff guide catheter system or distally placed guide catheter system (or both in cases of severe tortuosity) is preferred to facilitate its delivery. Once the PED is ready for deployment in position distal to the aneurysm, delivery is initiated by unsheathing the distal 5 to 10 mm of the device (Figure 2A). The next step entails pushing the delivery catheter while holding the delivery wire steady, which causes a pillowing of the unsheathed portion of the device as a result of friction of the microcatheter tip against the exposed PED segment (Figure 2B). At this point, the distal tip of the PED, which is enclosed within a nose cone, may be released, or a clockwise turning of the delivery catheter may be required to encourage its release (Figure 2C). Once the distal segment of the device is released, the stent portion may be dragged from its position to a more proximal site if required (eg, to avoid unnecessary covering of the posterior communicating artery). The stent can then be deployed by simply unsheathing the rest of the device. This result may be sufficient if vessel tortuosity is minimal; however, to ensure wall apposition, we typically perform a partial unsheathing by withdrawing the catheter (Figure 2D), followed by pushing the delivery wire or advancing the delivery microcatheter distally, which causes longitudinal compaction and radial expansion of the device because of friction caused by the microcatheter tip against the unsheathed device (Figure 2E). This maneuver (partial unsheathing followed by device compaction with microcatheter advancement) may be repeated several times to ensure appropriate wall apposition before the device is completely delivered. Furthermore, we make an effort to increase metallic coverage of the parent vessel at the site of the aneurysm neck with this technique. Once the device is completely delivered, the delivery microwire remains in position through the device in the parent vessel. If apposition of the device is suboptimal, bringing the microcatheter over the delivery wire and through the device will frequently cause sufficient shortening to improve wall apposition. Additionally, a second PED may be deployed, although we have found that this is generally not required. If device apposition is sufficient after delivery, the microcatheter need not be advanced through the device and should simply be removed with the wire.
A 68-year-old woman presented with a chief complaint of blurred vision in the right eye. Ophthalmological examination revealed optic nerve atrophy and right eye visual field cut. Magnetic resonance imaging was consistent with a cerebral aneurysm, and diagnostic angiography (Figure 3) confirmed a right cavernous segment aneurysm measuring 13 mm. After discussion of treatment options, the patient desired treatment of the aneurysm with flow diversion. Aspirin (325 mg daily) and clopidogrel (75 mg daily) were started 5 days before the procedure. In anticipation of the procedure, measurements of the ICA proximal and distal to the aneurysm were made for selection of the PED (Figure 4). With an approximate diameter of 4.5 to 4.7 mm and a relatively small neck of 6 mm, a 4.75-mm (diameter) × 18-mm (length) device was selected.
Standard femoral artery access was obtained after administration of fentanyl (50 μg) and midazolam (2 mg) for conscious sedation. Because of the tortuosity of the aortic arch, common carotid artery, and ICA (Figure 5), a flexible distal access catheter (Reflex 072, Covidien Neurovascular) was inserted within a supporting guide catheter (Cook Shuttle, Cook Inc, Bloomington, Indiana), and these catheters were placed within the ICA with the use of fluoroscopic visualization. A microcatheter with a 0.027-in inner diameter (Marksman, Covidien Neurovascular) was then directed into the intracranial ICA distal to the aneurysm over a flow-directed 0.016-in microwire (Guide Wire M, Terumo, Tokyo, Japan). With the microcatheter in position distal to the aneurysm, the microwire was removed, and the PED was advanced to the distal end of the microcatheter for delivery. The device was deployed in position, covering the aneurysm neck (Figure 6). After delivery, an angiographic run was performed that displayed stasis of contrast material within the aneurysm, suggestive of successful flow diversion (Figure 7). With the PED in good position, the delivery wire and catheter were removed, and the arteriotomy was closed percutaneously.
The patient was admitted to the neurosurgical intensive care unit for postoperative monitoring in accordance with routine protocol. Her postoperative course was notable for headache with greatest intensity behind the right eye. Her symptoms improved after a short course of oral steroid therapy. Dual antiplatelet therapy was continued at the time of discharge, to be continued for a total of 6 months. An angiogram performed 2 months postoperatively was consistent with complete obliteration (Figure 8).
A 50-year-old woman presented with a Hunt-Hess grade III and Fisher grade 3 subarachnoid hemorrhage (SAH; Figure 9). A ventriculostomy was placed, with improvement of examination to a Glasgow Coma Scale score of 13 (from a score of 7). After ventriculostomy placement, no focal neurological deficits were present. Angiography confirmed the presence of an irregular, 15-mm ophthalmic artery aneurysm (Figure 10). No other aneurysm was appreciated, and this lesion was considered the likely source of her hemorrhage. Coil embolization was performed, with dome protection and partial obliteration of the aneurysm (Figure 11). She was admitted postoperatively for monitoring and prescribed medications for vasospasm prophylaxis, including nimodipine (60 mg orally every 4 hours), magnesium (intravenous infusion of 12 g magnesium sulfide in 500 mL normal saline daily), and aspirin (325 mg orally on a daily basis). Her postoperative course was remarkable for asymptomatic radiographic cerebral vessel spasm, which required no treatment. On SAH day 10, a computed tomographic scan showed no evidence of hydrocephalus, and the ventriculostomy was removed. With good recovery from her SAH, the patient was offered treatment with flow diversion because, in our experience, the location and size of her aneurysm placed her at high risk for recurrence.3 After discussion of the risks and benefits of flow diversion, she consented to this procedure. In anticipation of the procedure, aspirin (325 mg daily after a 650-mg loading dose) and clopidogrel (75 mg daily after a 600-mg loading dose) were prescribed 1 day preoperatively. Measurements for the PED were made on the basis of previous angiography (Figure 12), and a PED with sufficient length and diameter (4.5 × 18 mm) approximated to the diameter of the ICA proximal to the aneurysm (4.3 mm) was selected.
On SAH day 15, the patient was brought to the angiography suite for definitive treatment of her aneurysm with flow diversion. Standard femoral artery access was obtained with a 6F sheath after administration of fentanyl (25 μg) and midazolam (2 mg) for conscious sedation. Because arterial access was straightforward (Figure 13), a 6F guide catheter (Envoy, DePuy Synthes-Codman) was advanced directly into the ICA with the use of fluoroscopic visualization. A microcatheter with a 0.027-in inner diameter (Marksman) was directed into position within the parent vessel distal to the aneurysm with a 0.016-in-diameter Guide Wire M microwire (Terumo) after failure to navigate distal to the aneurysm with a steerable 0.014-in-diameter microwire (Figure 14). Under direct fluoroscopic visualization, the PED was delivered in position, covering the aneurysm neck but not the posterior communicating artery. After delivery, an angiogram was performed, which revealed good patency of the PED and no evidence of residual aneurysm filling (Figure 15).
The patient was admitted to the neurosurgical intensive care unit postoperatively. Other than persistent mild headache, she had no complaints and was discharged home with a normal neurological examination on SAH day 17. Dual antiplatelet therapy for 6 months postoperatively is planned. A follow-up angiogram will be performed.
The cases presented display the technique of PED delivery for flow diversion. Both patients were treated for symptomatic large or giant aneurysms of the ICA proximal to the superior hypophyseal segment, and both patients had complete obliteration. Incomplete obliteration of the aneurysm on completion of the procedure, as presented in case 1, is a common finding.4 With experience, we have learned to be patient with the gradual involution process and have found that most aneurysms are completely obliterated on 2- or 3-month follow-up angiography after placement of a single PED.
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Dr Hopkins receives grant/research support from Toshiba; serves as a consultant to Abbott, Boston Scientific, Cordis, Micrus, and Silk Road; holds a financial interest in AccessClosure, Augmenix, Boston Scientific (Boston Scientific's neurovascular business has been acquired by Stryker), Claret Medical Inc, Endomation, Micrus, and Valor Medical; has a board/trustee/officer position with AccessClosure and Claret Medical Inc; serves on Abbott Vascular speakers’ bureau; and has received honoraria from Bard, Boston Scientific, Cleveland Clinic, Complete Conference Management, Cordis, Memorial Health Care System, and the Society for Cardiovascular Angiography and Interventions (SCAI). Dr Levy receives research grant support, other research support (devices), and honoraria from Boston Scientific and research support from Codman & Shurtleff, Inc and ev3/Covidien Neurovascular; has ownership interests in Intratech Medical Ltd and Mynx/Access Closure; serves as a consultant on the board of Scientific Advisors to Codman & Shurtleff, Inc; serves as a consultant per project and/or per hour for Codman & Shurtleff, Inc, ev3/Covidien Neurovascular, and TheraSyn Sensors, Inc; and receives fees for carotid stent training from Abbott Vascular and ev3/Covidien Neurovascular. Dr Levy receives no consulting salary arrangements. All consulting is per project and/or per hour. Dr Mokin has received an educational grant from Toshiba Medical System Corp. Dr Siddiqui has received research grants from the National Institutes of Health (coinvestigator: National Institute of Neurological Disorders and Stroke 1R01NS064592-01A1, Hemodynamic Induction of Pathologic Remodeling Leading to Intracranial Aneurysms; not related to the present article) and the University at Buffalo (Research Development Award; not related to the present article); holds financial interests in Blockade Medical, Hotspur, Intratech Medical, StimSox, and Valor Medical; serves as a consultant to Codman & Shurtleff, Inc, Concentric Medical, Covidien Vascular Therapies, GuidePoint Global Consulting, Penumbra, Inc., Pulsar Vascular, and Stryker Neurovascular. belongs to the speakers’ bureaus of Codman & Shurtleff, Inc and Genentech; belongs to the speakers' bureaus of Codman & Shurtleff, Inc. and Genentech; serves on National Steering Committees for Penumbra, Inc. 3D Separator and Covidien SWIFT PRIME trials; serves on an advisory board for Codman & Shurtleff and Covidien Vascular Therapies; and has received honoraria from American Association of Neurological Surgeon’s courses, Annual Peripheral Angioplasty and All That Jazz Course, Penumbra, Inc., and Abbott Vascular and Codman & Shurtleff, Inc for training other neurointerventionists in carotid stenting and for training physicians in endovascular stenting for aneurysms. Dr Siddiqui receives no consulting salary arrangements. All consulting is per project and/or per hour. Dr Snyder serves as a consultant to, has been a member of the speakers’ bureau of, and has received honoraria from Toshiba. He serves as a member of the speakers’ bureau for and has received honoraria from ev3 and The Stroke Group. The other authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article.
We thank Paul H. Dressel, BFA, for preparation of the illustrations and Debra J. Zimmer for editorial assistance.
2. Becske T, Kallmes DF, Saatchi I, et al.. Pipeline for uncoilable or failed aneurysms: results of a multicenter clinical trial. Radiology. 2013;267(3):858–868.
3. Hauck EF, Natarajan SK, Hopkins LN, Levy EI, Siddiqui AH. Salvage Neuroform stent-assisted coiling for recurrent giant aneurysm after waffle-cone treatment. J Neurointerv Surg. 2011;3(1):27–29.
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