Safety and Efficacy of a 3-Dimensional Stent Retriever With Aspiration-Based Thrombectomy vs Aspiration-Based Thrombectomy Alone in Acute Ischemic Stroke Intervention: A Randomized Clinical Trial.

Importance: The treatment effects of individual mechanical thrombectomy devices in large-vessel acute ischemic stroke (AIS) remain unclear. Objective: To determine whether the novel 3-dimensional (3-D) stent retriever used in conjunction with an aspiration-based mechanical thrombectomy device (Penumbra System; Penumbra) is noninferior to aspiration-based thrombectomy alone in AIS. Design, Setting, and Participants: This randomized, noninferiority clinical trial enrolled patients at 25 North American centers from May 19, 2012, through November 19, 2015, with follow-up for 90 days. Adjudicators of the primary end points were masked to treatment allocation. Patients with large-vessel intracranial occlusion AIS presenting with a National Institutes of Health Stroke Scale (NIHSS) score of at least 8 within 8 hours of onset underwent 1:1 randomization to 3-D stent retriever with aspiration or aspiration alone. The primary analyses were conducted in the intention-to-treat population. Interventions: Mechanical thrombectomy using intracranial aspiration with or without the 3-D stent retriever. Main Outcomes and Measures: The primary effectiveness end point was the rate of a modified Thrombolysis in Cerebral Infarction (mTICI) grade of 2 to 3 with a 15% noninferiority margin. Device- and procedure-related serious adverse events at 24 hours were the primary safety end points. Results: Of 8082 patients screened, 198 patients were enrolled (111 women [56.1%] and 87 men [43.9%]; mean [SD] age, 66.9 [13.0] years) and randomized, including 98 in the 3-D stent retriever with aspiration group and 100 in the aspiration alone group; an additional 238 patients were eligible but not enrolled. The median baseline NIHSS score was 18.0 (interquartile range, 14.0-23.0). Eighty-two of 94 patients in the 3-D stent retriever and aspiration group (87.2%) had an mTICI grade of 2 to 3 compared with 79 of 96 in the aspiration alone group (82.3%; difference, 4.9%; 90% CI, -3.6% to 13.5%). None of the other measures were significantly different between the 2 groups. Device-related serious adverse events were reported by 4 of 98 patients in the 3-D stent retriever with aspiration group (4.1%) vs 5 of 100 patients in the aspiration only group (5.0%); procedure-related serious adverse events, 10 of 98 (10.2%) vs 14 of 100 (14.0%). A 90-day modified Rankin Scale score of 0 to 2 was reported by 39 of 86 patients in the 3-D stent retriever with aspiration group (45.3%) vs 44 of 96 patients in the aspiration only group (45.8%). Conclusions and Relevance: The present study provides class 1 evidence for the noninferiority of the 3-D stent retriever with aspiration vs aspiration alone in AIS. Future trials should evaluate whether these results can be generalized to other stent retrievers. Trial Registration: clinicaltrials.gov Identifier: NCT01584609.

Cross-circulation thrombectomy with use of a stent retriever: A case report.

Introduction The efficacy of the endovascular treatment of acute ischemic stroke has been substantiated by several recent randomized clinical trials. While intra-arterial therapy has significantly evolved in recent years, anatomic cerebrovascular variants and disease burden can present challenges to timely recanalization. We present the first reported case of anterior-to-posterior mechanical clot retrieval with use of a stent retriever. Case description A 53-year-old man presented with basilar artery thrombosis. Endovascular mechanical clot retrieval was performed. The typical, antegrade, access to the basilar artery thrombus was precluded by the findings of a hypoplastic left vertebral artery and an occluded proximal right vertebral artery. Given a number of factors including the patient's worsening symptoms and the high morbidity and mortality associated with basilar stroke, cross-circulation-anterior-to-posterior-intra-arterial therapy was performed. Thrombectomy of the basilar thrombus was achieved via the right internal carotid artery and right posterior communicating artery. Conclusion To our knowledge, we report the first case of cross-circulation, anterior-to-posterior thrombectomy, with the use of a stent-retriever device. Cross-circulation stroke treatment may be beneficial in cases of proximal vessel occlusion or anatomical constraints. Larger studies will need to evaluate the safety and efficacy of these approaches.

Consecutive Endovascular Treatment of 20 Ruptured Very Small (<3 mm) Anterior Communicating Artery Aneurysms.

BACKGROUND: Small aneurysms located at the anterior communicating artery carry significant procedural challenges due to a complex anatomy. Recent advances in endovascular technologies have expanded the use of coil embolization for small aneurysm treatment. However, limited reports describe their safety and efficacy profiles in very small anterior communicating artery aneurysms. OBJECTIVE: We sought to review and report the immediate and long-term clinical as well as radiographic outcomes of consecutive patients with ruptured very small anterior communicating artery aneurysms treated with current endovascular coil embolization techniques. METHODS: A prospectively maintained single-institution neuroendovascular database was accessed to identify consecutive cases of very small (<3 mm) ruptured anterior communicating artery aneurysms treated endovascularly between 2006 and 2013. RESULTS: A total of 20 patients with ruptured very small (<3 mm) anterior communicating artery aneurysms were consecutively treated with coil embolization. The average maximum diameter was 2.66 ± 0.41 mm. Complete aneurysm occlusion was achieved for 17 (85%) aneurysms and near-complete aneurysm occlusion for 3 (15%) aneurysms. Intraoperative perforation was seen in 2 (10%) patients without any clinical worsening or need for an external ventricular drain. A thromboembolic event occurred in 1 (5 %) patient without clinical worsening or radiologic infarct. Median clinical follow-up was 12 (±14.1) months and median imaging follow-up was 12 (±18.4) months. CONCLUSION: This report describes the largest series of consecutive endovascular treatments of ruptured very small anterior communicating artery aneurysms. These findings suggest that coil embolization of very small aneurysms in this location can be performed with acceptable rates of complications and recanalization.

Stenting and angioplasty for idiopathic intracranial hypertension: a case series with clinical, angiographic, ophthalmological, complication, and pressure reporting.

BACKGROUND: Previous studies have demonstrated that cerebral dural sinus stenosis (DSS) may be a potential patho-physiological cause of idiopathic intracranial hypertension (IIH). Endovascular therapy for DSS is emerging as a potential alternative to treat IIH. Here, we present the results of our case series. METHOD: We prospectively collected angiographic and manometric data on patients that underwent angioplasty/stenting for IIH. All patients had failed maximal medical therapy (MMT) and had confirmed sinus stenosis. Demographic, clinical and radiological presentation, and outcomes were collected retrospectively. RESULTS: A total of 18 patients underwent 25 procedures. Demographics revealed a mean age of 30 (range 15-59), 83% (15/18) were female, 72% (13/18) were white, and mean body mass index of 36 (range 23-59.2). All patients presented with classic IIH. Symptom improvement or resolution was reported in 94% (17/18) of patients. All patients had resolution and/or stabilization/improvement of their papilledema. Headaches related to increased pressure improved in 56% (10/18). Re-stenosis and retreatment occurred in 33% (6/18). No procedural related complications were reported. CONCLUSION: Dural sinus angioplasty and stenting is relatively safe, feasible, and clinically efficacious for patients with symptomatic sinus stenosis who have failed standard therapy. The long-term durability of patency and clinical improvement remains unknown.

Endovascular reconstruction for progressively worsening carotid artery dissection.

BACKGROUND: Carotid artery dissection is an important cause of stroke in young patients. Selection criteria for endovascular repair have not been well defined and limited data exist on long-term outcomes of stent reconstruction. OBJECTIVE: To report the immediate and long-term clinical and radiographic outcomes of patients treated with stent placement for progressively worsening symptomatic carotid arterial dissection despite antithrombotic therapy. METHODS: A single institution neuro-endovascular database was accessed to identify consecutive cases in which carotid artery dissection was treated with endovascular repair between 2006 and 2012. Clinical, demographic, radiographic, and procedural data were obtained through chart review. RESULTS: A total of 22 patients were identified and included 27 carotid artery dissection repairs with stent implantation. The mean age was 43 years (±8.7) with 13 patients being women. Traumatic dissections were seen in 9 (40.9%) patients and spontaneous dissections in 13 (59.1%) patients. All patients were symptomatic and were started on antithrombotic therapy on diagnosis. Most common indications for treatment included recurrent ischemia despite antithrombotic therapy in 15 (55.5%) arteries and enlarging dissecting aneurysm in 4 (14.8%) arteries. Mean degree of stenosis was 79.1%. Mean number of stents used was 1.88 (range 1-4). There was 1 (4.5%) asymptomatic peri-procedural thromboembolic event. Median clinical follow-up was 14 months (range 3-40) and median imaging follow-up was 14 months (range 3-38). There was 1 (4.5%) case of recurrent transient ischemic attack. There was no death, significant restenosis or stroke in the territory of the treated vessel during the duration of the follow-up. CONCLUSIONS: Endovascular stent reconstruction for the treatment of selected patients with progressively worsening carotid dissection despite medical management is feasible with acceptable immediate and long-term clinical and radiographic outcomes. To be able to draw more robust conclusions, further evaluation with larger number of patients and longer follow-up is needed.

Predictors and Outcomes Associated with Rescue Therapy in SWIFT.

INTRODUCTION: In the Solitaire With the Intention For Thrombectomy (SWIFT) trial, rescue therapy was used when the Solitaire or Merci device was unable to restore vessel patency. Markers for nonrecanalization in acute stroke have been reported for intravenous tissue plasminogen activator; however, similar predictors are not known for endovascular therapy. We sought to identify predictors and outcomes associated with rescue therapy in the SWIFT trial. METHODS: Rescue therapy included the use of an alternative device, agent, or maneuver following failure to recanalize with three retrieval attempts using the initial device. Clinical, angiographic, and demographic data was reviewed. RESULTS: Among a total of 144 patients enrolled, 43 (29.9%) required rescue therapy. We used the same baseline demographics for patients with and without rescue therapy. Rescue therapy was used in a higher percentage of patients randomized to the Merci group compared with the Solitaire group (43 vs. 21%, p = 0.009). Patients with rescue therapy experienced a longer recanalization time (p < 0.001), a lower percentage of successful recanalization (p < 0.001), and a lower percentage of good outcome (p = 0.009). In multivariate analysis, patients randomized to the Merci group (OR 3.99, 95% CI 1.58, 10.10) and age >80 years (OR 3.51, 95% CI 1.06, 11.64) were predictors of rescue therapy. CONCLUSIONS: Merci treatment group and age were predictors of rescue therapy, while a trend toward an increased need of rescue therapy was observed with hypertension and proximal clot location. Rescue therapy was associated with fewer good outcomes. These findings may reflect targets for improvement in endovascular therapy.

Stenting and angioplasty of small cerebral arteries in symptomatic intracranial atherosclerotic disease.

BACKGROUND: Intracranial atherosclerotic disease (ICAD) is a common cause of stroke with a poor natural history despite medical therapy. Few studies have investigated endovascular therapies for the treatment of symptomatic ICAD in distal intracranial arteries. Here, we present the feasibility and safety of balloon angioplasty with and without stenting in patients with medically refractory small artery symptomatic ICAD. METHOD: Personal logs were reviewed to identify patients who were treated for small artery ICAD (stenosis > 50%) using angioplasty ± stenting. Small cerebral arteries were defined by a diameter ≤ 2 mm or any branch distal to a large intracranial vessel (i.e. distal to ICA, M1, A1, Vertebrobasilar trunk). Patient characteristics, clinical manifestations, treatment, hospital course, and follow up data was collected and analyzed. RESULTS: Ten patients (12 arteries) were treated with either primary balloon angioplasty (58.3%) or angioplasty with stenting (41.6 %) with 100% technical success rate. Mean pre-treatment stenosis was 79.9% while mean post-treatment stenosis was 19.0%. There were no major peri-procedural complications including symptomatic intracranial hemorrhage or mortality; three cases were complicated by groin hematoma. Patients were followed for a mean total of 18.6 months with only one symptomatic restenosis which was re-treated successfully. All patients had good functional outcome with a mRS of either 0 (80%) or 1 (20%) on follow up. CONCLUSION: In our case series, treatment of symptomatic small artery ICAD with angioplasty ± stenting was safe and effective. These interventions should be considered as an alternative treatment for ICAD patients refractory to medical therapy.

The natural history of vertebral artery origin stenosis.

BACKGROUND: We sought to determine the long-term survival and natural history of vertebral artery origin stenosis (VAOS) as it relates to stroke. METHODS: We retrospectively reviewed clinical data on patients admitted at a single institution for possible stroke between 2004 and 2007 and selected subjects who underwent angiography of the neck. We classified VAOS subjects as having "moderate" to "severe" (≥50%) occlusion. Age-, sex-, and race-matched control subjects with no evidence of VAOS on angiography were selected from our study population. Long-term follow-up data were collected and death certificates were searched for comparison among cases and controls. A Kaplan-Meier curve was plotted based on time to event (stroke or death). RESULTS: Fifty-eight of the 358 subjects were found to have VAOS (16.2%). Four subjects were excluded because of stenting; therefore, 54 cases and 54 matched controls were included for long-term follow-up analysis. In our study population, we calculated that the relative risk of having a stroke or dying in patients with VAOS was 6 times that of patients without VAOS (P < .02). The observed 5-year survival rate for patients with VAOS was 67% (36/54) compared to 89% (48/54) in control subjects (P < .01). CONCLUSIONS: Patients with VAOS are at a significantly higher risk of having a stroke or dying. Subsequent prospective, multicenter studies are needed to validate our results.

Identifying delays to mechanical thrombectomy for acute stroke: onset to door and door to clot times.

Outcomes from endovascular therapy for acute stroke are time dependent. Delays in the administration of this therapy have not been extensively studied and no performance benchmarks have been established. There are limited data on the complex factors that can affect these delays. In this review, we discuss the existing literature on the delays involved in endovascular therapy and have presented them as prehospital and inhospital factors. Some of these factors are common to intravenous thrombolysis; in addition, there are some that are unique to endovascular therapy. These include the awareness of the first responders, emergency medical services, interhospital transfer and triage systems, activation of the endovascular team, complex imaging decisions, and intraprocedural delays. A thorough understanding of these delays can help identify areas of improvement which may affect clinical outcomes.

Safety and predictors of aneurysm retreatment for remnant intracranial aneurysm after initial endovascular embolization.

INTRODUCTION: Aneurysmal subarachnoid hemorrhage (SAH) is a rare but devastating form of stroke. Endovascular therapy has been criticized for its higher rate of recanalization and retreatment. The safety and predictors of retreatment are unknown. We report the clinical outcomes, imaging outcomes and predictors for aneurysm retreatment after initial endovascular embolization. METHOD: We identified patients who underwent endovascular retreatment from July 2005 through November 2011. Aneurysm and patient data were collected. Periprocedural complications were reported as intraoperative perforation (IOP) or thromboembolic event (TEE). Aneurysm and patient characteristics were compared between aneurysms requiring retreatment and those not requiring retreatment to evaluate aneurysm retreatment predictors. RESULTS: A total of 111/871 (13%) aneurysms underwent retreatment. Two (0.2%) were retreated for recurrent acute SAH, 82 (74%) aneurysms were located in the anterior circulation, 47 (42%) required stent and 5 (5%) required balloon assist during retreatment. There were a total of 5 (5%) IOP and 6 (5%) TEE from which 2 (2%) and 1 (1%) were symptomatic, respectively. Overall symptomatic events rate were 2.7%. Patients were followed up for an average of 15±14 months. Seven (0.8%) aneurysms required a second retreatment without any recurrent SAH. Multivariable analysis revealed an OR for aneurysms requiring retreatment of 2.965 for aneurysms presenting as aneurysmal SAH, 1.791 for aneurysms in the posterior circulation and 1.053 for aneurysms with large dome size. CONCLUSIONS: Aneurysm retreatment is a safe option without a significant increase in morbidity or mortality. SAH, posterior circulation aneurysms and larger aneurysm dome size are predictors of aneurysms requiring retreatment.

The diagnosis and management of brain arteriovenous malformations.

Although uncommon in the general population, cerebral arteriovenous malformations (AVMs) can pose a significant health risk if a rupture occurs. Advances in noninvasive imaging have led to an increase in the identification of unruptured AVMs, presenting new challenges in management, given their poorly understood natural history. Over the past decade, there have been significant developments in the management and treatment of intracranial AVMs. This article discusses the pathophysiology, natural history, clinical presentations, and current treatment options, including multimodal approaches, for these vascular malformations.

Angiographic lumen changes associated with oversized intracranial stent implantation for aneurysm treatment.

BACKGROUND: The effect of oversized intracranial stent implantation, and potential excessive neointimal hyperplasia from the chronic outward radial force, has not been reported. We sought to compare the angiographic narrowing associated with implantation of oversized stents. METHODS: We reviewed an aneurysm database and identified patients treated with stent-assisted embolization involving a vessel size transition. Demographics and lesion characteristics were extracted. The relationship between lumen diameter and stent oversizing was compared. RESULTS: Twenty vessels were identified in 18 patients, providing 80 paired data points. Mean follow-up time was 8 months (SD 6). The average oversizing in the smaller diameter parent vessel landing-zone was 1.75 mm. Mean change in lumen size from pre-stent implantation was not significantly different for any of the four sites. There was a significant difference in change of lumen size at the stent tines when compared with the respective mid-stent segment for both the proximal (P = 0.02) and distal (P = 0.0004) landing zones. CONCLUSIONS: A small significant lumen loss occurs at stent tines when compared to midstent struts. However, there is no overall significant stenosis from highly oversized stents. Persistent luminal gain from the oversized stent radial force likely predominates over any neointimal hyperplasia.

The effect of time of day on cold water ingestion by high-level swimmers in a tropical climate.

The authors tested the effect of cold water ingestion during high-intensity training in the morning vs the evening on both core temperature (TC) and thermal perceptions of internationally ranked long-distance swimmers during a training period in a tropical climate. Nine internationally ranked long-distance swimmers (5 men and 4 women) performed 4 randomized training sessions (2 in the evening and 2 in the morning) with 2 randomized beverages with different temperatures for 3 consecutive days. After a standardized warm-up of 1000 m, the subjects performed a standardized training session that consisted of 10 x 100 m (start every 1'20″) at a fixed velocity. The swimmers were then followed for the next 3000 m of the training schedule. Heart rate (HR) was continuously monitored during the 10 x 100 m, whereas TC, thermal comfort, and thermal sensation (TS) were measured before and after each 1000-m session. Before and after each 1000 m, the swimmers were asked to drink 190 mL of neutral (26.5 ± 2.5°C) or cold (1.3 ± 0.3°C) water packaged in standardized bottles. Results demonstrated that cold water ingestion induced a significant effect on TC, with a pronounced decrease in the evening, resulting in significantly lower mean TC and lower mean delta TC in evening cold (EC) than in evening neutral (EN), concomitant with significantly lower TS in EC than in EN and a significant effect on exercise HR. Moreover, although TC increased significantly with time in MN, MC, and EN, TC was stabilized during exercise in EC. To conclude, we demonstrate that a cold beverage had a significant effect on TC, TS, and HR during training in high-level swimmers in a tropical climate, especially during evening training.

Surveillance imaging after intracranial stent implantation: non-invasive imaging compared with digital subtraction angiography.

BACKGROUND: Digital subtraction angiography (DSA) is the gold standard imaging for detection of in-stent restenosis (ISR) but there is limited literature on optimal non-invasive surveillance imaging. In this study, the ability of CT angiography (CTA) and MR angiography (MRA) compared with DSA in recognizing ISR was assessed. METHODS: A single center database of patients treated with stent implantation for ICAD was accessed. All patients who underwent follow-up imaging with DSA paired with either MRA or CTA within 30 days were included. Two angiography readers and two non-invasive imaging readers measured restenosis with a submillimeter digital caliper. ISR was categorized as: none/minimal, mild (<50%), moderate (≥50-70%) or severe (≥70%). Analysis was performed with weighted κ statistics. RESULTS: 17 cases of individual stents that underwent surveillance imaging with paired DSA and CTA and five stents with paired DSA and MRA were identified. Of those undergoing DSA and CTA, inter-reader agreement produced κ=0.68 (95% CI 0.40 to 0.95) for DSA and κ=0.75 (95% CI 0.55 to 0.95) for CTA. Agreement across CTA and DSA was κ=0.36 (95% CI 0.26 to 0.52). Of those undergoing DSA and MRA, inter-reader agreement produced κ=0.71 (95% CI 0.27 to 1.00) for DSA and κ=1.00 (95% CI 1.00 to 1.00) for MRA. Agreement across MRA and DSA was κ=0.34 (95% CI 0.18 to 0.51). CONCLUSIONS: Good inter-reader agreement exists within DSA, CTA and MRA. However, when comparing non-invasive imaging (CTA and MRA) with DSA, only fair agreement exists. These data suggest that CTA and MRA are not comparable to DSA for evaluation of ISR.

Cerebral arteriovenous malformation diagnosis and management.

Arteriovenous malformations of the brain can carry considerable morbidity and mortality in the setting of rupture. The complex angioarchitecture and hemodynamic alteration requires careful consideration in diagnostic and management approaches. In this review, the authors define the pathophysiology, outline diagnostic methods, and highlight current management approaches.

Idiopathic Intracranial Hypertension. A Systematic Analysis of Transverse Sinus Stenting.

BACKGROUND: Idiopathic intracranial hypertension (IIH) is a disorder characterized by signs and symptoms of increased intracranial pressure without structural cause seen on conventional imaging. Hallmark treatment after failed medical management, has been CSF shunting or optic nerve fenestration with the goal of treatment being preservation of vision. Recently, there have been multiple case reports and case series on dural sinus stenting for this disorder. OBJECTIVE: We aim to review all published cases and case series of dural sinus stenting for IIH, with analysis of patient presenting symptoms, objective findings (CSF pressures, papilledema, pressure gradients across dural sinuses), follow-up of objective findings, and complications. METHODS: A Medline search was performed to identify studies meeting pre-specified criteria of a case report or case series of patients treated with dural sinus stent placement for IIH. The manuscripts were reviewed and data was extracted. RESULTS: A total of 22 studies were identified, of which 19 studies representing 207 patients met criteria and were included in the analysis. Only 3 major complications related to procedure were identified. Headaches resolved or improved in 81% of patients. Papilledema improved the (172/189) 90%. Sinus pressure decreased from an average of 30.3 to 15 mm Hg. Sinus pressure gradient decreased from 18.5 (n=185) to 3.2 mm Hg (n=172). Stenting had an overall symptom improvement rate of 87%. CONCLUSION: Although all published case reports and case series are nonrandomized, the low complication and high symptom improvement rate make dural sinus stenting for IIH a potential alternative surgical treatment. Standardized patient selection and randomization trials or registry are warranted.

Complications of endovascular therapy for acute ischemic stroke and proposed management approach.

Over the past decade, endovascular therapy has emerged as a promising therapeutic approach for select patients with acute ischemic stroke. However, the morbidity, mortality, and complication rates in intra-arterial recanalization trials are higher than in the National Institute of Neurological Disorders and Stroke trial of IV tissue plasminogen activator. This review discusses common complications associated with endovascular therapy for acute ischemic stroke, avoidance of complications, and management of some of the common complications.

Demand-supply of neurointerventionalists for endovascular ischemic stroke therapy.

OBJECTIVE: To estimate the needed workforce of trained neurointerventionalists (NIs) to perform endovascular therapy (ET) for eligible patients with acute ischemic stroke (AIS). METHOD: Population and ischemic stroke incidence data were extracted with use of US Census and Centers for Disease Control and Prevention 2009 estimates. The annual "demand" is defined as the proportion of AIS patients who would meet inclusion criteria and clinical standards for ET. The "supply" is defined as the number of trained NIs and NIs in training. The "workforce" is the number of NIs needed to meet the demand (the number of eligible AIS patients) within an accessible geographic diameter. Data on NIs and NI fellowships were collected (Society of Neurointerventional Surgery [SNIS], Society of Vascular & Interventional Neurology [SVIN], Concentric Medical, and Penumbra Inc.). RESULTS: The estimated number of NIs is close to 800, practicing within a 50-mile radius of major metropolitan areas in the United States, covering more than 95% of the US population. Approximately 40 NI fellows are graduating yearly from US training programs. In 5 years and 10 years, the number of NIs may reach 1,000 and 1,200, respectively. Currently, there are approximately 14,000 thrombectomy procedures performed in the United States each year. However, the percentage of AIS patients who may be eligible for ET in our estimation is 4% to 14%, or about 25,000 to 95,000 patients. This means that cases will occur at a rate of 26 to 97 per year in 5 years, or 22 to 81 per year in 10 years, for each NI. Providing 24/7 AIS coverage requires 2 to 3 NIs per medical center, adding to the challenge of providing manpower without diluting experience in areas of lower population density. CONCLUSION: The current and projected number of NIs would adequately supply the future need if the proportion of patients requiring AIS endovascular therapy increases. However, 2 to 3 NIs per comprehensive stroke center would be needed to provide 24/7 AIS therapy with a sufficient number of cases per NI. A tertiary stroke center model similar to the trauma model may provide the manpower solution without compromising the quality of care.