Clinical UM Guideline

This document addresses the use of mechanical thrombectomy for acute ischemic stroke. Mechanical thrombectomy is an endovascular technique for removal of a thrombus or embolus from an intracranial blood vessel to reestablish blood flow.

Medically Necessary:

Intra-arterial mechanical embolectomy or thrombectomy is considered medically necessary in the treatment of ischemic stroke when any of the following criteria sets (I, II, III, IV or V) have been met:

1. Anterior cerebral artery (A1 or A2), middle cerebral artery (M1 or M2) or intracranial carotid artery occlusion when all criteria are met:
   1. Mechanical embolectomy is performed within 6 hours of onset of symptoms; and
   2. NIH Stroke Scale (NIHSS) score of 2 or greater; and
   3. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.
2.  Intracranial internal carotid artery or middle cerebral artery (M1) occlusion when all criteria are met:
   1. Mismatch between the severity of the clinical deficit and the infarct volume, as defined in any of the following situations:
      1. 80 years of age or older: NIHSS score of 10 or higher and an infarct volume of less than 21 ml; or
      2. Less than 80 years of age: NIHSS score of 10 or higher and an infarct volume of less than 31 ml; or
      3. Less than 80 years of age: NIHSS score of 20 or higher and an infarct volume from 31 to 50 ml;
         and
   2. Last known to be well 6 to 24 hours earlier; and
   3. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.
3. Intracranial internal carotid artery or proximal middle cerebral artery (M1) occlusion when all criteria are met:
   1. Mismatch between ischemic tissue and infarct volume, as defined by both of the following:
      1. Initial infarct volume of less than 70 ml; and
      2. A ratio of the volume of ischemic tissue to infarct volume of 1.8; and
   2. Last known to be well 6 to 16 hours earlier; and
   3. Baseline NIHSS score greater than or equal to 6; and
   4. Modified Rankin Scale (mRS) score less than or equal to 2 prior to qualifying stroke; and
   5. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.
4. Large ischemic core infarct due to intracranial internal carotid artery or proximal middle cerebral artery (M1) occlusion (or both) when all criteria are met:
   1. Infarct as defined by any of the following:
      1. Alberta Stroke Program Early Computed Tomography Score (ASPECTS) value of 3 to 5 on non-contrast CT; or
      2. An estimated ischemic-core volume of 50 ml or greater; and
   2. Last known to be well up to 24 hours earlier; and
   3. Baseline NIHSS score of greater than 6; and
   4. mRS score less than or equal to 2 prior to qualifying stroke; and
   5. Neuroimaging has ruled out intracranial hemorrhage or dissection.
5. Basilar artery occlusion when all of the following criteria are met:
   1. Last known to be well up to 24 hours earlier; and
   2. Baseline NIHSS falls into any of the following categories:
      1. NIHSS score of greater than or equal to 10 if presenting within 12 hours of when last known to be well; or
      2. NIHSS score of greater than or equal to 6 if presenting between 12 - 24 hours of when last known to be well; and
   3. mRS score less than or equal to 2 prior to qualifying stroke; and
   4. Neuroimaging has ruled out intracranial hemorrhage or arterial dissection.

Not Medically Necessary:

Intra-arterial mechanical embolectomy or thrombectomy is considered not medically necessary in the treatment of stroke in all other circumstances when the criteria above have not been met.

The following codes for treatments and procedures applicable to this guideline are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services may be Medically Necessary when criteria are met:

When services are Not Medically Necessary:
For the procedure and diagnosis codes listed above when criteria are not met, for the following diagnosis codes, or when the code describes a procedure indicated in the Clinical Indications section as not medically necessary.

When services are also Not Medically Necessary:
For the following procedure and diagnosis codes, or when the code describes a procedure indicated in the Clinical Indications section as not medically necessary.

Description

A stroke is a condition where blood flow to the brain is interrupted to the extent that proper brain function is disrupted. Approximately 795,000 strokes occur annually in the United States. Ischemic strokes, caused by blockage of the blood vessels to the brain, account for approximately 87% of all strokes, and frequently result in neurologic emergencies (Centers for Disease Control [CDC], 2024). Tissue plasminogen activators (tPAs), systemic thrombolytic agents, are frequently given intravenously (IV) within 3 hours of symptoms for treatment of strokes due to blocked blood vessels. Mechanical embolectomy has been used to reopen occluded vessels in the brain, either alone or in conjunction with tPA treatment, by physically extracting occlusive thrombi from the cerebral vasculature. Thrombectomy is considered an effective therapy in appropriate populations, the number needed to treat (NNT) to prevent disability in one individual is 2.3 (Fayad, 2023). The procedure does carry risks associated with potential reperfusion injury of necrotic brain tissue including hemorrhage, edema, disability and death (Fayad, 2023).

Emboli extraction devices are designed to be placed into the affected artery and advanced to the site of the thrombi in the brain via imaging guidance. The thrombi are extracted using one or a combination of mechanical embolectomy devices. Two types of devices can be used for mechanical thrombectomy. Stent retriever devices use a stent-like metal structure to ensnare the target clot and remove it. Aspiration devices use negative pressure to remove the targeted clot. The choice between which device is used depends upon provider preference and stroke center availability.

Mechanical Embolectomy in the Anterior Circulation

Retrospective studies have assessed the safety and efficacy of mechanical embolectomy for the treatment of anterior ischemic stroke (AIS) caused by intracranial artery occlusions (Brouwer, 2018; Pereira, 2013). Collectively, these studies indicate that mechanical embolectomy exhibits high efficacy and maintains a safety profile comparable with other treatment modalities. These findings are corroborated by multiple randomized controlled trials (RCTs), which have investigated the use of mechanical embolectomy across various time frames post-symptom onset. Specifically, these initial RCTs have focused on individuals with imaging-confirmed major intracranial vessel occlusions who underwent treatment within 6 hours of stroke onset, with outcomes assessed up to 2 years post-procedure (Berkhemer, 2015; Campbell, 2014; Campbell, 2015; van den Berg, 2017).

Jovin and colleagues (2015) published the results of the Randomized Trial of Revascularization with mechanical embolectomy versus Best Medical Therapy in the Treatment of Acute Stroke Due to Anterior Circulation large Vessel Occlusion Presenting within Eight Hours of Symptom Onset (REVASCAT) study. REVASCAT focused on individuals with radiologically confirmed intracranial occlusion who were treated with IV tPA alone or IV tPA plus mechanical embolectomy. Individuals were treated within 8 hours of symptom onset. Recruitment was stopped early due to loss of equipoise at the first interim analysis. The 1-year results of the REVASCAT study reported that at 12 months post-treatment the adjusted odds ratio (OR) for improvement in mRS score was 1.8 in favor of the device group (Dávalos, 2017). Al-Ajlan and colleagues (2018) reported on a follow-up study of data from the REVASCAT trial. The authors concluded, “Endovascular treatment saves brain and improves 90-day clinical outcomes primarily through a beneficial effect on the 24-hour stroke severity.”

The DAWN trial, an unblinded, multicenter RCT assessed individuals with an  occlusion of the intracranial carotid artery or proximal (first segment, M1) middle cerebral artery who had last been known to be well between 6 and 24 hours prior to treatment (Nogueira, 2017). Affected individuals were randomized to treatment with either mechanical embolectomy plus standard care or standard care alone. These arms were further stratified into three groups, with group A being 80 years of age or older, having a score of 10 or higher in the NIHSS and an infarct volume less than 21 ml. Group B was younger than 80, had a NIHSS score of 10 or higher, and an infarct volume less than 31 ml. Group C was younger than 80, had an NIHSS score of 20 or higher, and an infarct volume of 31 to less than 51 ml. At 31 months, enrollment in the trial was stopped because of the results of a prespecified interim analysis. The mean score on the utility-weighted mRS at 90 days was 5.5 in the thrombectomy group versus 3.4 in the control group  and the rate of functional independence at 90 days was 49% in the thrombectomy group versus 13% in the control group. The rate of symptomatic intracerebral hemorrhage (sICH) did not differ significantly between the two groups. The results of this study demonstrate significant benefit to the use of intra-arterial mechanical interventions in selected individuals within 6 to 24 hours of time last known to be well.

The DEFUSE 3 trial reported on the use of mechanical embolectomy beyond 6 hours of onset of symptoms (Albers, 2018). Individuals affected with an occlusion of the cervical or intracranial carotid artery or the proximal middle cerebral artery with an initial infarct volume of less than 70 ml and a ratio of volume of ischemic tissue to initial infarct volume of 1.8 or greater were treated with  mechanical embolectomy plus medical therapy or medical therapy alone. Treatment was initiated 6 to 16 hours after the subject was last known to be well. The study was stopped early due to the primary efficacy endpoint being met during an interim analysis. The authors concluded:

Endovascular thrombectomy for ischemic stroke 6 to 16 hours after a patient was last known to be well plus standard medical therapy resulted in better functional outcomes than standard medical therapy alone among patients with proximal middle-cerebral-artery or internal-carotid-artery occlusion and a region of tissue that was ischemic but not yet infarcted.

Mechanical Embolectomy in Large Ischemic Stroke

Large ischemic-core strokes, which account for approximately one-fifth of large-vessel occlusion strokes, have been underrepresented in clinical trials. The prognosis of affected individuals is poor, including progression of stroke symptoms, brain edema and death (Sarraj, 2023). Sarraj and associates (2023) performed a prospective, randomized, open-label, adaptive, international trial evaluating the safety and efficacy of endovascular thrombectomy in this population. Individuals diagnosed within the previous 24 hours with an acute large ischemic core stroke due to an occlusion of the internal carotid artery, the M1 segment of the middle cerebral artery or both, were included. Eligibility criteria included an ASPECTS value of 3-5 or an estimated ischemic core volume of 50 ml or greater, a pre-stroke mRS of 0 or 1 and no documented evidence of intracranial hemorrhage. Participants received either endovascular thrombectomy and standard medical care or standard medical care alone. The primary outcome was the ordinal mRS score, a measure of functional independence, at 90 days. At 90 days post-therapy, the median mRS score was 4 (interquartile range, 3 to 6) in the thrombectomy group and 5 (interquartile range, 4 to 6) in the standard medical care group. A total of 20% of individuals in the thrombectomy group achieved a mRS of 0 to 2 compared to 7.0% in the standard medical care group. Symptomatic intracranial hemorrhage was reported in 0.6% of the endovascular thrombectomy group compared to 1.1% in the standard medical care group. Procedural complications included arterial access-site (3%), vessel perforation (4%) and dissection (6%). The trial was stopped early due to the reported efficacy of endovascular thrombectomy. At 1 year follow-up, 45% (77/170) of the individuals in the thrombectomy group and 52% (83/159) of the usual care group had died. The thrombectomy group reported a significant benefit in functional outcomes over the usual care group (Sarraj, 2024).

Huo and colleagues (2023) conducted a multicenter, prospective, open-label, randomized trial to evaluate the efficacy and safety of endovascular therapy and medical management compared to standard medical management alone in individuals diagnosed with an acute large-vessel occlusion in the anterior circulation within the previous 24 hours. Other inclusion criteria included NIHSS score of 6-30, a pre-stroke mRS score of 0-1 and a large-vessel occlusion of the initial segment of the middle cerebral artery, the intracranial segment of the distal internal carotid artery or both. The primary outcome was the mRS at 90 days. A total of 50 participants in the endovascular group and 45 in the medical management group died before 90 days. The primary distribution analysis showed a shift in the distribution of the mRS scores toward better outcomes in the endovascular group versus the medical management group. Symptomatic intracranial hemorrhage occurred in 14 individuals in the endovascular group (6.1%) and 6 individuals in the medical management group (2.7%). The trial was stopped early based upon second interim analysis showing the efficacy of endovascular therapy over medical management alone.

The TESLA trial, an open-label, blinded-end point, Bayesian-adaptive randomized trial, aimed to evaluate the effect of thrombectomy in individuals with a large infarct within 24 hours of stroke onset (Writing Committee for the TESLA Investigators, 2024). Individuals with anterior circulation, large vessel occlusion identified on noncontrast CT who presented within 24 hours of the initiation of symptoms were included (n=300). Additional inclusion criteria included a NIHSS score of 6 or higher, ASPECTS score of 2-5, and a pre-stroke mRS score of 0-1. Individuals were randomized to undergo endovascular thrombectomy (n=152) or receive usual medical care (n=148). The primary outcome was the 90-day functional outcome assessed by the utility-weighted mRS (UW-mRS), with a minimum clinically important difference set at 0.3. The results showed that the mean 90-day UW-mRS score was 2.93 in the intervention group compared to 2.27 in the control group, with an adjusted difference of 0.63. Mortality rates at 90 days were similar between the two groups: 35.3% for the intervention group and 33.3% for the control group. Symptomatic intracranial hemorrhage occurred in 4.0% of the intervention group compared to 1.3% in the control group. The study concluded that thrombectomy did not significantly improve functional outcomes in individuals with large infarcts identified by noncontrast CT within 24 hours of stroke onset.

Randomized studies have reported positive clinical outcomes when endovascular embolectomy is used to treat large core ischemic stroke. Generally, these studies have included individuals with an ASPECTS score of 2 or 3 to 5. A limited number of studies focused on very large ischemic core strokes with an ASPECTs score of 0 to 1 or 2. These studies are limited by study design, consisting of prospective or registry studies or analysis of a subgroup of a larger study (Xie, 2024). The reported clinical outcomes have been inconsistent regarding improved functional outcomes compared to the standard medical treatment. The current evidence does not show that endovascular therapy to treat very large core ischemic stroke provides consistent clinical benefit over standard medical therapy (Uchida, 2022; Xie, 2024).

Mechanical Embolectomy to Treat AIS in the Posterior Circulation

The effectiveness of embolectomy therapy to treat AIS within the anterior circulation is well established; recent studies have focused on the role of mechanical embolectomy for posterior circulation occlusions continues to be evaluated (Meyer, 2020; Stambo, 2020; Watson, 2020; Zhao, 2020). While initial studies generally reported similar reperfusion rates in anterior and posterior recanalization therapy, there was conflicting results regarding complication and mortality rates between the groups (Langezaal 2021; Liu, 2020; Meinel, 2019).

Meyer and colleagues (2021) reported the results of the TOPMOST study, a multicenter case-control trial involving individuals with primary distal occlusion of the P2 or P3 segments of the posterior cerebral artery treated with either mechanical embolectomy or medical therapy. Of the 313 individuals with posterior circulation distal medium vessel occlusion (DMVO) receiving treatment, 243 met inclusion criteria, and 184 individuals were compared by treatment group after 1:1 propensity score matching (n=92 individuals in each group, thrombectomy versus medical therapy). At baseline, diabetes as a cardiovascular risk factor was significantly higher in the control group versus the thrombectomy group (30 versus 14, respectively). Additionally, the medical therapy group received IV thrombolysis significantly more frequently than the thrombectomy group, both before and after propensity matching, (39% versus 56%, p=0.01 and 40% versus 57.7%, p=0.01, respectively). A total of 141 individuals received mechanical thrombectomy, with a successful first pass reperfusion (mTICI 3) reported in 45.5% of cases. Additional passes increased the overall success rate to 76.2%. Distal embolization to another vessel was reported in 5 individuals (3.5%), with successful recanalization of those locations in 3 individuals. Post-propensity score matching, mean baseline NIHSS scores had decreased from admission in both groups, with there being no significant differences between groups (-2 in the thrombectomy group versus -1.5 in the medical group). However, there was a significant benefit in favor of individuals in the thrombectomy group with > 10 NIHSS score on admission versus the medical group (mean difference 5.6). No significant differences between groups were also noted in the subgroup of individuals with an mTICI of 2a or lower. In the thrombectomy group, two independent factors were identified for predicting successful early neurological improvement, higher NIHSS scores and successful first pass effect. In the medical group, only the presence of P3 occlusions were predictive of successful early neurological improvement. At 90 days, excellent neurological outcomes (mRS ≤ 1) were reported in 66.2% of thrombectomy group individuals versus 54.4% of medical group individuals. sICH was reported in 4.3% of individuals in both groups. Similarly, overall mortality was 4.9% in both groups at 90 days. The authors concluded that the study suggested that “…mechanical thrombectomy for posterior circulation DMVO is a safe, and technically feasible treatment option for occlusions of the P2 or P3 segment of the PCA compared with standard medical treatment with or without IVT.” Rigorous studies should be conducted to confirm the findings of this case control trial.

The Endovascular Treatment for Acute Basilar-Artery Occlusion (ATTENTION) RCT compared clinical outcomes of individuals who received endovascular thrombectomy or best medical care following basilar artery occlusion stroke (Tao, 2022). Participants had a moderate-to-severe acute ischemic stroke with a NIHSS score of 10 or higher, were seen within 12 hours of last known time to be well and had a prestroke mRS of 2 or less. Participants were randomized to either the endovascular thrombectomy treatment and best medical care group or the best medical care group alone. Best medical care included IV thrombolytic agents, antiplatelet drugs, anticoagulation or combinations of these treatments. The primary outcome was a good functional status as defined by a mRS of 0-3 at 90 days. Good functional status was achieved in 46% of the treatment group compared to 23% of the control group. A higher number of individuals in the control group died within 90 days compared to the treatment group (55% versus 37%). The treatment group had a 5% rate of sICH , there were no cases in the control group. A 14% procedural complication rate was reported in the treatment group. An analysis completed at 1-year post-procedure reported that the thrombectomy group experienced an increase in excellent outcomes (mRS score 0-1) between day 90 and 1 year, the control group did not. The authors concluded that the benefits experienced in the thrombectomy group with favorable outcomes (mRS 0-3) were sustained and in those with excellent outcomes (mRS 0-1) the benefit was magnified (Li, 2024).

A second randomized trial (Jovin, 2022) comparing thrombectomy plus best medical care to best medical care alone  in the Basilar Artery Occlusion Chinese Endovascular (BAOCHE) trial. Individuals were eligible if there was a confirmed occlusion of the basilar artery or intracranial segment of both vertebral arteries that could be treated within 6 to 24 hours after symptom onset. A prestroke mRS of 0 or 1 and a NIHSS score of 10 or higher was also required. The NIHSS score requirement was later reduced to 6 or higher due to slow recruitment. The primary outcome was a good functional status as defined by a mRS of 0-3 at 90 days. Good functional status was achieved in 46% of the treatment group compared to 24% of the control group. Mortality at 90 days was higher in the control group compared to the thrombectomy group. The incidence of sICH was higher in the thrombectomy group. The trial was stopped early based on the efficacy of the thrombectomy added to best medical care.

Basilar artery occlusion is typically associated with poor outcomes. The results of the ATTENTION and BAOCHE trials show that embolectomy along with best medical care provides improved clinical outcomes in stroke treatment caused by basilar artery occlusion in individuals with specific clinical characteristics. These studies were associated with increased risk of complications. Further studies are needed to determine whether the benefit of thrombectomy outweighs the risk in an expanded set of individuals who present with posterior circulation occlusions.

Other Information

The American Heart Association and American Stroke Association (AHA/ASA) 2019Update to the 2018 Guidelines for the Early Management of Patients with Acute Ischemic Stroke (Powers, 2019) notes the following recommendations:

0 to 6 hours from onset

1. Patients should receive mechanical thrombectomy with a stent retriever if they meet all the following criteria: (1) prestroke mRS score of 0 to 1; (2) causative occlusion of the internal carotid artery or MCA segment 1 (M1); (3) age ≥18 years; (4) NIHSS score of ≥6; (5) ASPECTS of ≥6; and (6) treatment can be initiated (groin puncture) within 6 hours of symptom onset. (Class I; Level of Evidence A). (Revised from the 2015 guideline)
2. Direct aspiration thrombectomy as first-pass mechanical thrombectomy is recommended as noninferior to stent retriever for patients who meet all the following criteria: (1) prestroke mRS score of 0 to 1; (2) causative occlusion of the internal carotid artery or M1; (3) age ≥18 years; (4) NIHSS score of ≥6; (5) ASPECTS ≥6; and (6) treatment initiation (groin puncture) within 6 hours of symptom onset (Class I; Level of Evidence B-R). (Revised from the 2015 guideline)
3. Although the benefits are uncertain, the use of mechanical thrombectomy with stent retrievers may be reasonable for carefully selected patients with AIS in whom treatment can be initiated (groin puncture) within 6 hours of symptom onset and who have causative occlusion of the MCA segment 2 (M2) or MCA segment 3 (M3) portion of the MCAs. (Class IIb; Level of Evidence B-R). (Revised from the 2015 guideline. LOE revised)
4. Although the benefits are uncertain, the use of mechanical thrombectomy with stent retrievers may be reasonable for carefully selected patients with AIS in whom treatment can be initiated (groin puncture) within 6 hours of symptom onset and who have causative occlusion of the anterior cerebral arteries, vertebral arteries, basilar artery, or posterior cerebral arteries (Class IIb; Level of Evidence C-LD).

6 to 24 Hours from onset

1. In selected patients with AIS within 6 to 16 hours of last known normal who have LVO in the anterior circulation and meet other DAWN or DEFUSE 3 eligibility criteria, mechanical thrombectomy is recommended. (Class I; Level of Evidence A). (New recommendation)
2. In selected patients with AIS within 16 to 24 hours of last known normal who have LVO in the anterior circulation and meet other DAWN eligibility criteria, mechanical thrombectomy is reasonable. (Class IIa; Level of Evidence B-R). (New recommendation)

Other Endovascular Therapies

1. Mechanical thrombectomy with stent retrievers is recommended over intra-arterial fibrinolysis as first-line therapy (Class I; Level of Evidence C-EO). (Revised from the 2015 guideline. )

In 2018 the American Heart Association Council on Cardiovascular Radiology and Intervention and Stroke Council published their indications for the performance of intracranial endovascular neurointerventional procedures (Eskey, 2018). In this document they provided the following recommendations:

2. Endovascular therapy with stent retrievers is recommended over intra-arterial fibrinolysis as first line therapy.
4. Use of stent retrievers is preferred over other mechanical thrombectomy devices. The use of mechanical thrombectomy devices other than stent retrievers may be reasonable in some circumstances but is not yet supported by large RCTs.
5. In carefully selected patients with anterior circulation occlusion who have contraindications to intravenous r-tPA, endovascular therapy with stent retrievers completed within 6 hours of stroke onset is reasonable. Inadequate data are available at this time to determine the clinical efficacy of endovascular therapy in such patients (eg, those with prior stroke, serious head trauma, hemorrhagic coagulopathy, or receiving anticoagulant medications).
8. When treatment is initiated beyond 6 hours from symptom onset, the effectiveness of endovascular therapy is uncertain for patients with AIS who have causative occlusion of the ICA or proximal MCA (M1). New trial results addressing this topic will be available in the near future.
9.  Patients should receive endovascular therapy with a stent retriever if they meet all the following criteria: (1) prestroke mRS score of 0 to 1, (2) AIS receiving intravenous r-tPA within 4.5 hours of onset according to guidelines from professional medical societies, (3) causative occlusion of the ICA or proximal MCA (M1), (4) age ≥18 years, (5) NIHSS score of ≥6, (6) ASPECTS of ≥6, and (7) ability to initiate treatment (groin puncture) within 6 hours of symptom onset.

Summary

The available evidence addressing the use of mechanical embolectomy devices is extensive. A number of prospective, registry and retrospective studies focusing on specific devices have been published showing improved health outcomes over medical therapy in AIS of the anterior circulation (Binning, 2018;  Kaesmacher, 2019; Mattle, 2019; Mokin, 2018; Nogueira, 2022; Penumbra Pivotal Stroke Trial Investigators, 2009; Tarr, 2010; Tarr, 2018; Zaidat, 2018a; Zaidat, 2018c, Zaidat, 2022). Additionally, data from large, well-designed, and conducted studies (Berkhemer, 2014; Campbell, 2014, 2015; Goyal, 2015; Joval, 2015; Saver, 2015) have demonstrated significant benefits to mechanical embolectomy/thrombectomy in select individuals. Mechanical embolectomy, used in conjunction with medical therapy is associated with greater complications than medical therapy alone, but has the potential to prevent severe disability and improve mortality.

Alberta Stroke Program Early Computed Tomography Score (ASPECTS): A 10-point quantitative topographic CT scan score developed to assess early ischemic changes on pretreatment CT studies in individuals with acute ischemic stroke of the anterior circulation. ASPECTS is determined from evaluation of two standardized regions of the MCA territory, including the basal ganglia level and the supraganglionic level. The abnormality should be visible on at least two consecutive cuts to ensure that it is truly abnormal rather than a volume averaging effect. To compute the ASPECTS, 1 point is subtracted from 10 for any evidence of early ischemic change for each of the defined regions. A normal CT scan receives ASPECTS of 10 points. A score of 0 indicates diffuse involvement throughout the MCA territory.

Embolectomy: Surgical removal of an obstructing clot or foreign material which has been transported from a distant vessel by the bloodstream.

Emboli: Material (usually a blood clot but may be fat or a bone fragment, etc.) that travels through the circulation and eventually obstructs blood flow through a smaller caliber vessel.

Modified Rankin scale (mRS): A tool defining global disability which has been widely used as a measurement in stroke studies. The tool ranges from 0 (no symptoms at all) to 6 (death).

Modified Thrombolysis in Cerebral Infarction (mTICI) score: A qualitative scale used to evaluate an individual’s angiographic intracerebral inflow following endovascular thrombectomy. The AHA recommends a score of 2B or more as an angiographic goal following therapy on the anterior circulation.

National Institute of Health Stroke Scale (NIHSS): A systematic assessment tool that provides a quantitative measure of stroke-related neurologic deficit. The scale is widely used as a clinical assessment tool to evaluate acuity of stroke patients, determine appropriate treatment, and predict patient outcome. It is a 15-item neurologic examination evaluating the effect of acute cerebral infarction on the levels of consciousness, language, neglect, visual-field loss, extraocular movement, motor strength, ataxia, dysarthria, and sensory loss. The Score is intended to be used by a trained observer who rates an individual’s ability to answer questions and perform activities. Ratings for each item are scored with 3 to 5 grades with 0 as normal, and there is an allowance for untestable items. The single assessment requires less than 10 minutes to complete.

Neurovasculature: The blood vessel network of the neck and brain.

Plasmin: A proteolytic enzyme that is formed from plasminogen in blood plasma and dissolves the fibrin in blood clots; also called fibrinolysin.

Precerebral arteries: An arterial blood vessel leading to the cerebrum (but not in the cerebrum), including the vertebral artery, basilar artery, carotid artery, and ascending aorta.

Stroke: A condition where blood flow to the brain is interrupted to the extent that proper brain function is disrupted.

Thrombolytics: Drugs that dissolve blood clots.

Tissue plasminogen activator (tPA): An enzyme that dissolves blood clots. It can be produced naturally by cells in the walls of blood vessels or prepared through the use of genetic engineering. tPA is used in the coronary arteries during heart attacks and in the cranial arteries ischemic strokes when there is a low risk of hemorrhage.

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Embolus Retriever with Interlinked Cages (ERIC)
EmboTrap and EmboTrap II Revascularization Device
Mechanical embolectomy
Mechanical thrombectomy
Merci Retrieval System
Penumbra System
RECO Flow Restoration Device
ReVive SE Thrombectomy Device
Solitaire FR Revascularization Device
Stroke
Trevo Retriever

The use of specific product names is illustrative only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available.