Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
GENERAL SCIENTIFIC SESSION 4 GENERAL SCIENTIFIC SESSION 4 Neuroendovascular Surgery for Acute Ischemic Stroke: All Patients All the Time Ashish Sonig, MD, MS, MCh*‡ Elad I. Levy, MD, MBA*‡§¶ Departments of *Neurosurgery and §Radiology, Jacobs School of Medicine and Biomedical Sciences, and ¶Toshiba Stroke and Vascular Research Center, University at Buffalo, State University of New York, Buffalo, New York ‡Department of Neurosurgery, Gates Vascular Institute at Kaleida Health, Buffalo, New York Correspondence: Elad I. Levy, MD, MBA, University at Buffalo Neurosurgery, 100 High St, Ste B4, Buffalo, NY 14203. E-mail: [email protected] Copyright © 2016 by the Congress of Neurological Surgeons. A cute stroke is one of the leading causes of death worldwide; an estimated 85% of acute strokes are caused by cerebral ischemia, and only 30% to 40% are large-vessel occlusions amenable to intervention.1,2 An analysis of the long journey of acute stroke management shows the substantial influence of technology on the safety and efficacy of intraarterial mechanical thrombectomy. Initial randomized controlled trials (RCTs) of acute stroke treatment focused on intra-arterial infusion of thrombolytic agents (Prolyse in Acute Cerebral Thromboembolism [PROACT] II1 and the Middle Cerebral Artery Embolism Local Fibrinolytic Intervention Trial [MELT]3). In the subsequent years, those trials were followed by mechanical thrombectomy trials, Interventional Management of Stroke (IMS) III,4 Synthesis Expansion: A Randomized Controlled Trial on Intra-Arterial vs Intravenous Thrombolysis in Acute Ischemic Stroke (SYNTHESIS Expansion),5 and Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE).6 These trials predominantly used a first-generation thrombectomy device, the Merci retriever (Stryker, Kalamazoo, Michigan). The IMS III trial was stopped prematurely because the results did not show any significant difference in functional outcomes after thrombectomy plus intravenous recombinant tissue-type plasminogen activator (tPA) compared with intravenous tPA alone. These mechanical thrombectomy trials had limitations, primarily that documentation of largevessel occlusion was not obligatory. In IMS III, 20% of patients randomized to the endovascular group had no large-vessel occlusion. Clearly, these patients would not benefit from endovascular therapy. Technology moved forward, and newer stent retrievers, the Solitaire (Covidien, Irvine, California) and the Trevo (Stryker), received Conformité Européenne approval in 2008 and 2009, respectively. In 2012, they were approved for use by the US Food and Drug Administration. However, retrievable stents were used in 64 | VOLUME 63 | NUMBER 1 | AUGUST 2016 only a minority of patients in the mechanical thrombectomy trials. For example, these stents were used in only 13% of cases in SYNTHESIS Expansion.5 The year 2015 can be unequivocally called a watershed moment in the management of acute stroke secondary to large-vessel occlusion. Five RCTs favoring mechanical thrombectomy over medical management with intravenous tPA alone for large-vessel occlusion in the setting of anterior circulation stroke were published. These RCTs (Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment [SWIFT PRIME],7 Multicenter Randomized Clinical Trial of Endovascular Treatment of Acute Ischemic Stroke in the Netherlands [MR CLEAN],8 Extending the Time for Thrombolysis in Emergency Neurological Deficits–Intra-Arterial [EXTEND-IA],9 Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion With Emphasis on Minimizing CT to Recanalization Times [ESCAPE],10 and Randomized Trial of Revascularization With Solitaire FR Device vs Best Medical Therapy in the Treatment of Acute Stroke Due to Anterior Circulation Large Vessel Occlusion Presenting Within Eight Hours of Symptom Onset [REVASCAT]11) endorsed the superiority of endovascular treatment over medical management alone. The patients underwent thrombectomy within a time frame of 6 to 12 hours after symptom onset.7,10 In view of the substantial and conclusive evidence stemming from these 5 trials, the American Heart Association/American Stroke Association guidelines were updated.12 According to the 2015 guidelines update, there is a Class I (strong) recommendation (Level of Evidence A) for stent-retriever thrombectomy if all the following criteria are met: prestroke modified Rankin Scale (mRS) score of 0 to 1, acute ischemic stroke receiving intravenous recombinant tPA within 4.5 hours of onset according to guidelines from professional medical societies, causative occlusion of the internal carotid artery (ICA) or proximal middle cerebral www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited NEUROENDOVASCULAR SURGERY FOR ACUTE ISCHEMIC STROKE artery (MCA; M1 segment), age $ 18 years, National Institutes of Health Stroke Scale (NIHSS) score of $ 6, Alberta Stroke Program Early CT Score (ASPECTS)13 of $ 6, and treatment can be initiated (groin puncture) within 6 hours of symptom onset. The guidelines included IMS III,4 SYNTHESIS Expansion,5 and MR RESCUE6 in their assessment. As mentioned, these trials preferentially used first-generation embolectomy devices (predominantly the Merci retriever) for mechanical thrombectomy compared with the stent retrievers used in recent trials (SWIFT PRIME,7 MR CLEAN,8 EXTEND-IA,9 ESCAPE,10 and REVASCAT11). For thrombectomies in patients with occlusions of the M2 or M3 portion of the MCA, anterior cerebral artery, vertebral artery, basilar artery, or posterior cerebral artery, the guidelines provided a Class IIb, Level of Evidence C recommendation.12 In the journey of mechanical thrombectomy over the years, it took 96 to 104,5 years for the Merci stent retriever from its Conformité Européenne certification in 2002 (US Food and Drug Administration approval in 2004) to 2012, when enrollment in different RCTs (IMS III,4 SYNTHESIS Expansion,5 and MR RESCUE6) was completed. Similarly, it took 7 years for the Solitaire and Trevo stent retrievers to find legitimate application in acute stroke intervention. This brings us to an important question: Do we need to conduct RCTs to extend the benefit of this proven technology to other patients with large-vessel occlusions such as the pediatric population, those with strokes in a different location (ie, the posterior circulation), and those experiencing the onset of symptoms outside the therapeutic window (eg, wake-up strokes)? In an attempt to answer this question, we examine these subsets through a review of relevant literature and the presentation of illustrative cases. POSTERIOR CIRCULATION STROKE Posterior circulation stroke has the highest reported mortality and morbidity of all strokes.14 With intravenous tPA and intraarterial tPA, recanalization can be achieved in only 50% of patients, and only 45% to 55% of survivors regain functional independence.15 It is imperative to find an alternative treatment approach. Excellent results are found in the literature of mechanical thrombectomy with modern stent retrievers. The results of mechanical thrombectomy in the setting of acute vertebrobasilar occlusion across the globe are summarized in the Table.16-22 In our single-center series, 75% of patients achieved an mRS score of 0 to 2.22 Similarly, in a multicenter series that included 100 patients with posterior circulation strokes, good recanalization (Thrombolysis in Cerebral Infarction [TICI] grade 2b or 3) was associated with favorable outcome.23 In this series, both stent retrieval and aspiration thrombectomy as primary treatment approaches were effective in achieving successful recanalization. Illustrative Case 1 A 34-year-old woman sustained a 30-ft fall. Initially, she developed neck pain and then left-sided weakness, slurred speech, and left-sided CLINICAL NEUROSURGERY facial droop with progressive onset of quadriparesis (NIHSS score . 20). The patient was intubated at an outside hospital, and by the time she arrived at the emergency room at our institute, she was outside the therapeutic window for intravenous tPA therapy. A computed tomographic (CT) angiogram showed basilar artery dissection and occlusion. The patient underwent a diagnostic catheter angiogram that showed basilar and left vertebral artery dissections (Figure 1A). She subsequently underwent reconstruction of the basilar artery with 5 Enterprise stents (Codman Neuro, Raynham, Massachusetts; Figure 1B and 1C), and an Xpert stent (Abbott Vascular, Santa Clara, California) was deployed to repair the vertebral artery dissection (Figure 1D-1F). In the first week, the patient slowly regained trace movements on her left side. She then continued to improve with overall increased mobility. After 6 months, she became ambulatory with near-normal speech. At the 2year follow-up evaluation, she had an mRS score of 1. Illustrative Case 2 An 82-year-old woman was referred from an outside hospital where she was recovering from open reduction and internal fixation of a right hip fracture. She was unresponsive on examination. Rightsided hemianopia was noticed with left gaze preferences. Palate elevation was examined and was significant for a left curtain sign and left tongue deviation. The gag reflex was weak. The corneal reflex was decreased in the left eye. Strength was 3/5 in both the upper and lower extremities. The NIHSS score was 21. Her medical history was significant for atrial fibrillation, status after coronary artery bypass grafting, type 2 diabetes mellitus, hypertension, hyperlipidemia, and essential tremor. tPA could not be administered because of her recent surgery. The patient underwent a CT stroke study (consisting of noncontrast CT scanning, CT angiography, and CT perfusion imaging), and an acute basilar artery occlusion was found (Figure 2A). She then underwent a diagnostic cerebral angiogram and mechanical thrombectomy with the Solitaire stent retriever (Figure 2B and 2C). A TICI grade 3 flow was achieved (Figure 2D). On postprocedural day 1, her NIHSS score was 1. In view of her recent hip surgery, she was discharged to a rehabilitation facility. ACUTE ICA OCCLUSION WITH OR WITHOUT TANDEM LESIONS Acute ICA occlusion carries significant mortality and morbidity and is more resistant to recanalization with intravenous tPA than are MCA occlusions.24 The recanalization rate associated with intravenous tPA for ICA occlusion is similar to the natural history of these occlusions.25 Recent trials7-11 have shown that intravenous tPA has a lower recanalization rate compared with stent retrievers in the setting of large-vessel occlusion. These trials did not study extracranial ICA occlusions and tandem lesions. In another study,26 50 consecutive patients with complete or near-total occlusion of the ICA were treated with aspiration, angioplasty, and/or stent placement in conjunction with retrieval devices. Successful recanalization (TICI grade . 2) was obtained in 45 of 50 patients VOLUME 63 | NUMBER 1 | AUGUST 2016 | 65 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited SONIG AND LEVY 66 | VOLUME 63 | NUMBER 1 | AUGUST 2016 TABLE 1. Stent Retrievers for Acute Basilar Artery Occlusiona Series, Year Stent Retriever Used for Treatment Mourand et al,21 2014 Baek et al,16 2014 Mohlenbruch et al,19 2014 Dorn et al,17 2012 Espinosa de Rueda et al,18 2013 Mordasini et al,20 2013 Patients, n Median NIHSS Score at Presentation Occlusion TICI Grade 0 Flow, % of cases Intravenous tPA, % of cases 31 25 24 24 18 14 15 11 24 16 20.4 21 31 (100) 25 (100) 22 (91.7) NA 16 (88.8) 14 (100) 19 (61) NA 21 (87.5) NA NA 5 (35.7) 12 20 12 (100) 5 (41.5) Sonig et al,22 2015 Solitaire FR Solitaireb Solitaire FR or Revive SE Solitaire FR Solitaire AB, Solitaire FR, or Trevo Solitaire FR in 10 patients, permanent stent/ angioplasty in 4 Solitaire FR-10 cases, Trevo-2 cases Series, Year Postprocedural TICI Grade 2-3 Flow, % of cases Time From Symptom Onset to Groin Puncture, min Time From Arterial Puncture to Recanalization, min mRS Score of 0-2 at 90Day or Last Follow-up, n (%) Mortality (mRS Score, 6), n (%) Perioperative Intracerebral Hemorrhage, n (%) 23 (74.2) 24 (96) 21 (87.5) 17 (77.9) 17 (94.4) 14 (100) 11 (91.7) 444 (median) 285 (median) 254 (median) NA 365.9 (mean) 414 (median) 211.25 (mean), 146 (median) 61 (mean) 30 (median) 77 (median) NA 75.1 (mean) 47 (median) 49.9 (mean), 44 (median) 11 (35) 12 (48) 8 (33) NA 9 (50) 4 (28.6) 9 (75) (9 of 10 or 90% at last follow-up) 10 (32) 3 (12) 7 (29) 11 (47.8) 4 (22.2) 5 (35.7) 2 (16.67) 5 (16) 2 (8) 2 (8) NA 1 (5) 0 0 Mourand et al,21 2014 Baek et al,16 2014 Mohlenbruch et al,19 2014 Dorn et al,17 2012 Espinosa de Rueda et al,18 2013 Mordasini et al,20 2013 Sonig et al,22 2015 a mRS, modified Rankin Scale; NA, not available; NIHSS, National Institutes of Health Stroke Scale; TICI, Thrombolysis in Cerebral Infarction; tPA, tissue plasminogen activator. Manufacturers: Revive, Codman, Raynham, Massachusetts; Solitaire AB and FR, Covidien, Irvine, California; and Trevo, Stryker, Kalamazoo, Michigan. b Type of Solitaire device (ie, AB or FR) unknown. Table reproduced with permission from Sonig A, Krishna C, Natarajan SK, et al. Stent retriever-assisted mechanical thrombectomy for acute basilar artery occlusion: single U.S. institution experience [published online ahead of print November 28, 2015]. Oper Neurosurg. doi: 10.1227/NEU.0000000000001163.22 www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited NEUROENDOVASCULAR SURGERY FOR ACUTE ISCHEMIC STROKE CLINICAL NEUROSURGERY VOLUME 63 | NUMBER 1 | AUGUST 2016 | 67 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited SONIG AND LEVY FIGURE 1. A, catheter angiography images (left, anteroposterior view; right, lateral view) show basilar artery dissection and thrombus (arrows). In view of the dissection and associated clot burden, the patient underwent stenting of the basilar artery. B, deployed Enterprise stent (Codman Neuro, Raynham, Massachusetts; left, arrow) and the remaining basilar occlusion (right). C, left vertebral artery angiographic run after subsequent placement of 4 additional Enterprise stents (arrows), followed by repair of the left vertebral artery dissection by placement of an Xpert stent (Abbott Vascular, Santa Clara, California; D, left, before reconstruction; arrow, dissection; right, after reconstruction). E, final injection from the left vertebral artery. F, follow-up computed tomographic angiogram on postoperative day 7 shows normal flow through the left vertebral and basilar arteries. (90%), and good outcome (mRS score , 2) at 6 months was obtained in 30 of 50 patients (60%). Similarly, our previously published systematic review27 showed that endovascular therapy for ICA occlusion results in more favorable clinical outcomes than intravenous tPA therapy alone. In our study, we analyzed a total of 969 patients. Favorable outcomes (mRS score of # 2 or Barthel Index of 90-100) were significantly more frequent in patients who underwent endovascular treatment than in those treated with intravenous thrombolysis alone (33.6% vs 24.9%; P = .004). A convoluted situation arises when a tandem occlusion is encountered along with an ICA occlusion: The extracranial carotid artery may or may not be completely occluded. In this situation, placement of an extracranial carotid stent may be necessary to obtain distal access. This extra step increases the complexity of the procedure,28 and the addition of antiplatelet medications, required in conjunction with carotid stent placement, carries an additional risk of hemorrhage. However, the risks and benefits of the procedure must be taken into consideration. Intravenous tPA alone in a such a situation may yield a poor recanalization rate and functional outcome compared with mechanical thrombectomy and extracranial carotid stenting.29 In one of the largest case series of stent implantation for proximal ICA occlusion and intra-arterial thrombolysis for tandem occlusion, 26 of 35 consecutively treated patients (74.3%) had a TICI grade of 2b or 3 after intervention.30 Symptomatic intracerebral hemorrhage occurred in only 1 patient. At the 3-month follow-up, the median NIHSS score was 4. Illustrative Case 3 A 64-year-old man presented with right leg weakness, difficulty with word finding, and blurring of vision in the left eye. His NIHSS score was 15. His medical history was remarkable for type 2 diabetes mellitus and atrial fibrillation. CT perfusion imaging showed an increase in time to peak in the left MCA territory with minimal loss of cerebral blood volume (Figure 3A). CT angiography (Figure 3B and 3C) showed left ICA dissection, M2 MCA occlusion, and occlusion at the origin of the left ICA. However, the venous phase of 4-dimensional CT angiography showed pseudo-occlusion of the left ICA (Figure 3B). The patient underwent diagnostic angiography (Figure 3D), proceeded by stenting of the left ICA for the dissection and thrombectomy of the superior and inferior MCA divisions (Figure 3E-3G). The immediate postprocedural angiogram showed TICI grade 3 flow in the superior and inferior 68 | VOLUME 63 | NUMBER 1 | AUGUST 2016 divisions of the left MCA (Figure 3H). After the procedure, the patient’s NIHSS score improved to 6. The 3-month follow-up CT angiogram showed patency of the left ICA and MCA (Figure 3I). At the last follow-up at 6 months, the patient’s mRS score was 1 and NIHSS score was 2. WAKE-UP STROKE Studies have shown that the time of stroke symptom onset is uncertain for between 8% and 25% of patients who arrive at the emergency room.31,32 Most such patients are those who were sleeping and woke up with a neurological deficit. The current guidelines (Level 1 evidence) advocate mechanical thrombectomy for large-vessel occlusion within 6 hours of symptom onset.12 Thus, patients with wake-up stroke cannot reap the full benefit of intervention. In such cases, viable brain tissue can be reliably identified only through neuroimaging. Recently conducted RCTs (ie, EXTEND-IA9 and SWIFT PRIME7) used CT perfusion imaging for the assessment of brain tissue viability. Another trial, ESCAPE,10 extended the intervention to 12 hours from symptom onset. The assessment of viability was based on the ASPECTS on noncontrast brain CT images. In this trial, 49 patients had symptom onset for $ 6 hours before intervention. The mRS scores at 90 days after intervention for this cohort and the cohort with time of onset of , 6 hours were not significantly different (rate ratio, 1.7; 95% confidence interval, 0.7-4.0). We performed a multicenter retrospective analysis of 52 consecutive patients with wake-up stroke who underwent mechanical thrombectomy.33 In our study, 46 patients (88%) were treated with stent retrievers, and 6 (12%) were treated with primary aspiration thrombectomy alone. TICI grade 2b or 3 recanalization was achieved in 36 patients (69%), and a 90-day mRS score of 0 to 2 was achieved in 25 patients (48%). Currently, a randomized trial, Trevo and Medical Management vs Medical Management Alone in Wake Up and Late Presenting Strokes (DAWN; NCT02142283), is underway in the United States. Enrollment depends on the viability of brain tissue identified with CT perfusion imaging and is extended to patients in whom treatment is initiated up to 24 hours from the onset of symptoms. Illustrative Case 4 An 86-year-old woman was found unresponsive in the morning; her NIHSS score was 12 at the time of presentation to the www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited NEUROENDOVASCULAR SURGERY FOR ACUTE ISCHEMIC STROKE FIGURE 2. A, computed tomographic (CT) angiographic reconstruction shows basilar artery occlusion (arrow). B, diagnostic angiogram, left vertebral artery injection, shows midbasilar occlusion. C, microcatheter injection (left, anteroposterior projection; right, lateral projection) shows good distal flow in the right posterior cerebral artery. D, final angiographic run shows Thrombolysis in Cerebral Infarction grade 3 flow after thrombectomy with the Solitaire stent retriever (Covidien, Irvine, California). emergency room. She had last been seen in normal condition 14 hours earlier. Her medical history was remarkable for hypertension, dyslipidemia, reflux disease, and osteoporosis. CT perfusion imaging (Figure 4A) showed increased time to peak in the left MCA territory with preserved cerebral blood volume and cerebral blood flow. CT angiography showed a left M1 occlusion (Figure 4B). The patient underwent a diagnostic angiogram and mechanical thrombectomy, which resulted in TICI grade 3 flow (Figure 4C). Postthrombectomy magnetic resonance imaging obtained on postoperative day 1 showed a small left basal ganglia infarct and a left frontal infarct (Figure 4D). At the time of CLINICAL NEUROSURGERY discharge, the patient’s NIHSS score was 3. At the last follow-up (6 weeks), her mRS score was 2. ABSENCE OF LEVEL 1 EVIDENCE DOES NOT MEAN ABSENCE OF CREDIBLE EVIDENCE With the current evidence in favor of thrombectomy for anterior circulation stroke, it may be unethical to randomize patients with posterior circulation stroke, wake-up stroke, or acute ICA with and without tandem occlusion or the pediatric VOLUME 63 | NUMBER 1 | AUGUST 2016 | 69 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited SONIG AND LEVY FIGURE 3. A, computed tomographic (CT) perfusion imaging shows preserved cerebral blood volume (left) and increased time to peak in the left middle cerebral artery (MCA) territory (right). B, CT angiographic reconstruction shows left internal carotid artery (ICA) occlusion and left M2 MCA occlusion. In the early phase of 4-dimensional CT angiography (left), the left ICA was not visualized, and occlusions of the inferior (arrowhead) and superior (arrow) divisions of the left MCA were evident. In the late venous phase of 4-dimensional CT angiography (right), the left ICA was visualized (arrow). C, axial CT angiography of the neck showed a dissection flap (arrow). D, right common carotid artery injection shows left MCA occlusion (left); early phase of left common carotid artery injection shows left ICA dissection (right, arrow). The dissection flap was navigated, and an inferior MCA thrombectomy was performed with a Solitaire stent retriever (Covidien, Irvine, California). E, partially occluded inferior MCA division before (left, black arrow) and after (right, white arrow) thrombectomy. F, Thrombolysis in Cerebral Infarction (TICI) grade 3 flow in the left superior MCA division after thrombectomy (arrow). G, owing to the tortuosity of the left proximal ICA, a Pipeline Embolization Device (Covidien) was deployed (left, arrow); subsequent complete reconstruction of the left ICA dissection is seen (right). H, final injection showing TICI grade 3 flow in the superior and inferior divisions of the left MCA. I, follow-up CT angiogram at 3 months shows normal flow through the left ICA and MCA. stroke population to receive medical management vs thrombectomy. Moreover, the prevalence of acute ischemic stroke in the pediatric population is so low34 that an RCT cannot be conceived. 70 | VOLUME 63 | NUMBER 1 | AUGUST 2016 Current trials have established the safety and efficacy of mechanical thrombectomy in the setting of acute stroke. The benefits must be extended to cover various populations, lesion locations, and extended time frames. There is good reason to www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited NEUROENDOVASCULAR SURGERY FOR ACUTE ISCHEMIC STROKE FIGURE 4. A, computed tomographic (CT) perfusion imaging shows preserved cerebral blood volume (left), increased time to peak (center), and preserved cerebral blood flow (right). B, CT angiographic reconstruction shows left middle cerebral artery (MCA) occlusion (arrow). The patient was taken for mechanical thrombectomy. C, left internal carotid artery injection showed a left MCA occlusion (left, arrow); Thrombolysis in Cerebral Infarction grade 3 flow was achieved after thrombectomy with the Solitaire stent retriever (right; Covidien, Irvine, California). D, postthrombectomy magnetic resonance imaging obtained on postoperative day 1 shows a small left basal ganglia infarct (left) and a left frontal infarct (right). think that the pace of change will increase with time as new technology brings the concept of disruptive innovation to the forefront. The older Merci retriever technology has largely been replaced by that of the current generation of stent retrievers. With time, endovascular intervention for acute stroke will become more efficacious and safer. RCTs will remain the gold standard and will help the physician to formulate practice patterns. However, in situations in which RCTs have unambiguously shown benefit in favor of the extension of certain device technology in the therapeutic spectrum on the basis of the results of multicenter retrospective studies, single-arm prospective registries are a very good option. Disclosures Dr Levy has shareholder/ownership interests in Intratech Medical Ltd, Blockade Medical LLC, and NeXtGen Biologics. He serves as a national principal investigator for the Covidien US SWIFT PRIME trials and receives honoraria for training and lecturing from that company. He receives compensation from Abbott for carotid training sessions for physicians. He serves as a consultant to Pulsar and Blockade Medical and on the Acute Ischemic Stroke Clinical Advisory Board for Stryker and the Advisory Board for NeXtGen Biologics and MEDX. Dr Sonig has no financial relationships to disclose. No funding was received directly in conjunction with this work. CLINICAL NEUROSURGERY REFERENCES 1. Furlan A, Higashida R, Wechsler L, et al; Prolyse in Acute Cerebral Thromboembolism Investigators. Intra-arterial prourokinase for acute ischemic stroke: the PROACT II study: a randomized controlled trial. JAMA. 1999;282 (21):2003-2011. 2. Mozaffarian D, Benjamin EJ, Go AS, et al. Heart disease and stroke statistics–2016 update: a report from the American Heart Association. Circulation. 2016;133(4): e38-e60. 3. Ogawa A, Mori E, Minematsu K, et al; MELT Japan Study Group. Randomized trial of intraarterial infusion of urokinase within 6 hours of middle cerebral artery stroke: The middle Cerebral Artery Embolism Local Fibrinolytic Intervention Trial (MELT) Japan. Stroke. 2007;38(10):2633-2639. 4. Broderick JP, Palesch YY, Demchuk AM, et al; Interventional Management of Stroke III Investigators. Endovascular therapy after intravenous t-PA versus t-PA alone for stroke. N Engl J Med. 2013;368(10):893-903. 5. Ciccone A, Valvassori L, Nichelatti M, et al; SYNTHESIS Expansion Investigators. Endovascular treatment for acute ischemic stroke. N Engl J Med. 2013; 368(25):904-913. 6. Kidwell CS, Jahan R, Gornbein J, et al; MR RESCUE Investigators. A trial of imaging selection and endovascular treatment for ischemic stroke. N Engl J Med. 2013;368(10):914-923. 7. Saver JL, Goyal M, Bonafe A, et al; SWIFT PRIME Investigators. Stent-retriever thrombectomy after intravenous t-PA vs. t-PA alone in stroke. N Engl J Med. 2015; 372(24):2285-2295. 8. Berkhemer OA, Fransen PS, Beumer D, et al; MR CLEAN Investigators. A randomized trial of intraarterial treatment for acute ischemic stroke. N Engl J Med. 2015;372(1):11-20. VOLUME 63 | NUMBER 1 | AUGUST 2016 | 71 Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited SONIG AND LEVY 9. Campbell BC, Mitchell PJ, Kleinig TJ, et al; EXTEND-IA Investigators. Endovascular therapy for ischemic stroke with perfusion-imaging selection. N Engl J Med. 2015;372(11):1009-1018. 10. Goyal M, Demchuk AM, Menon BK, et al; ESCAPE Trial Investigators. Randomized assessment of rapid endovascular treatment of ischemic stroke. N Engl J Med. 2015;372(11):1019-1030. 11. Jovin TG, Chamorro A, Cobo E, et al;REVASCAT Investigators. Thrombectomy within 8 hours after symptom onset in ischemic stroke. N Engl J Med. 2015;372 (24):2296-2306. 12. Powers WJ, Derdeyn CP, Biller J, et al. 2015 American Heart Association/ American Stroke Association focused update of the 2013 guidelines for the early management of patients with acute ischemic stroke regarding endovascular treatment: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2015;46(10):3020-3035. 13. Barber PA, Demchuk AM, Zhang J, Buchan AM. Validity and reliability of a quantitative computed tomography score in predicting outcome of hyperacute stroke before thrombolytic therapy: ASPECTS Study Group: Alberta Stroke Programme Early CT Score. Lancet. 2000;355(9216):1670-1674. 14. Mattle HP, Arnold M, Lindsberg PJ, Schonewille WJ, Schroth G. Basilar artery occlusion. Lancet Neurol. 2011;10(11):1002-1014. 15. Lindsberg PJ, Mattle HP. Therapy of basilar artery occlusion: a systematic analysis comparing intra-arterial and intravenous thrombolysis. Stroke. 2006; 37(3):922-928. 16. Baek JM, Yoon W, Kim SK, et al. Acute basilar artery occlusion: outcome of mechanical thrombectomy with Solitaire stent within 8 hours of stroke onset. AJNR Am J Neuroradiol. 2014;35(5):989-993. 17. Dorn F, Stehle S, Lockau H, Zimmer C, Liebig T. Endovascular treatment of acute intracerebral artery occlusions with the solitaire stent: single-centre experience with 108 recanalization procedures. Cerebrovasc Dis. 2012;34(1):70-77. 18. Espinosa de Rueda M, Parrilla G, Zamarro J, Garcia-Villalba B, Hernandez F, Moreno A. Treatment of acute vertebrobasilar occlusion using thrombectomy with stent retrievers: initial experience with 18 patients. AJNR Am J Neuroradiol. 2013; 34(5):1044-1048. 19. Mohlenbruch M, Stampfl S, Behrens L, et al. Mechanical thrombectomy with stent retrievers in acute basilar artery occlusion. AJNR Am J Neuroradiol. 2014;35 (5):959-964. 20. Mordasini P, Brekenfeld C, Byrne JV, et al. Technical feasibility and application of mechanical thrombectomy with the solitaire FR revascularization device in acute basilar artery occlusion. AJNR Am J Neuroradiol. 2013;34(1):159-163. 21. Mourand I, Machi P, Milhaud D, et al. Mechanical thrombectomy with the solitaire device in acute basilar artery occlusion. J Neurointerv Surg. 2014;6(3):200-204. 22. Sonig A, Krishna C, Natarajan SK, et al. Stent retriever-assisted mechanical thrombectomy for acute basilar artery occlusion: single U.S. institution experience [published online ahead of print November 28, 2015]. Oper Neurosurg. doi: 10. 1227/NEU.0000000000001163. Available at: http://journals.lww.com/onsonline/ 72 | VOLUME 63 | NUMBER 1 | AUGUST 2016 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. Abstract/publishahead/Stent_Retriever_Assisted_Mechanical_Thrombectomy.99984. aspx. Accessed January 29, 2016. Mokin M, Sonig A, Sivakanthan S, et al. Clinical and procedural predictors of outcomes from the endovascular treatment of posterior circulation strokes. Stroke. 2016;47(3):782-788. Linfante I, Llinas RH, Selim M, et al. Clinical and vascular outcome in internal carotid artery versus middle cerebral artery occlusions after intravenous tissue plasminogen activator. Stroke. 2002;33(8):2066-2071. Jansen O, von Kummer R, Forsting M, Hacke W, Sartor K. Thrombolytic therapy in acute occlusion of the intracranial internal carotid artery bifurcation. AJNR Am J Neuroradiol. 1995;16(10):1977-1986. Kwak JH, Zhao L, Kim JK, et al. The outcome and efficacy of recanalization in patients with acute internal carotid artery occlusion. AJNR Am J Neuroradiol. 2014;35(4):747-753. Mokin M, Kass-Hout T, Kass-Hout O, et al. Intravenous thrombolysis and endovascular therapy for acute ischemic stroke with internal carotid artery occlusion: a systematic review of clinical outcomes. Stroke. 2012;43(9):2362-2368. Nedeltchev K, Brekenfeld C, Remonda L, et al. Internal carotid artery stent implantation in 25 patients with acute stroke: preliminary results. Radiology. 2005; 237(3):1029-1037. Cohen JE, Gomori M, Rajz G, et al. Emergent stent-assisted angioplasty of extracranial internal carotid artery and intracranial stent-based thrombectomy in acute tandem occlusive disease: technical considerations. J Neurointerv Surg. 2013; 5(5):440-446. Kwak HS, Hwang SB, Jin GY, Hippe DS, Chung GH. Predictors of functional outcome after emergency carotid artery stenting and intra-arterial thrombolysis for treatment of acute stroke associated with obstruction of the proximal internal carotid artery and tandem downstream occlusion. AJNR Am J Neuroradiol. 2013; 34(4):841-846. Fink JN, Kumar S, Horkan C, et al. The stroke patient who woke up: clinical and radiological features, including diffusion and perfusion MRI. Stroke. 2002;33(4): 988-993. Wouters A, Lemmens R, Dupont P, Thijs V. Wake-up stroke and stroke of unknown onset: a critical review. Front Neurol. 2014;5:153. Mokin M, Kan P, Sivakanthan S, et al. Endovascular therapy of wake-up strokes in the modern era of stent retriever thrombectomy. J Neurointerv Surg. 2016;8(3): 240-243. Tsze DS, Valente JH. Pediatric stroke: a review. Emerg Med Int. 2011;2011: 734506. Acknowledgments We thank Paul H. Dressel, BFA, for preparation of the illustrations and Debra J. Zimmer for editorial assistance. www.neurosurgery-online.com Copyright © Congress of Neurological Surgeons. Unauthorized reproduction of this article is prohibited