Carotid revascularization and medical management for asymptomatic carotid stenosis - Hemodynamics (CREST-H): Study design and rationale

Recent advances and controversial issues in the optimal management of asymptomatic carotid stenosis

OBJECTIVE

The optimal management of patients with asymptomatic carotid stenosis (AsxCS) is enduringly controversial. We updated our 2021 Expert Review and Position Statement, focusing on recent advances in the diagnosis and management of patients with AsxCS.

METHODS

A systematic review of the literature was performed up to August 1, 2023, using PubMed/PubMed Central, EMBASE and Scopus. The following keywords were used in various combinations: "asymptomatic carotid stenosis," "carotid endarterectomy" (CEA), "carotid artery stenting" (CAS), and "transcarotid artery revascularization" (TCAR). Areas covered included (i) improvements in best medical treatment (BMT) for patients with AsxCS and declining stroke risk, (ii) technological advances in surgical/endovascular skills/techniques and outcomes, (iii) risk factors, clinical/imaging characteristics and risk prediction models for the identification of high-risk AsxCS patient subgroups, and (iv) the association between cognitive dysfunction and AsxCS.

RESULTS

BMT is essential for all patients with AsxCS, regardless of whether they will eventually be offered CEA, CAS, or TCAR. Specific patient subgroups at high risk for stroke despite BMT should be considered for a carotid revascularization procedure. These patients include those with severe (≥80%) AsxCS, transcranial Doppler-detected microemboli, plaque echolucency on Duplex ultrasound examination, silent infarcts on brain computed tomography or magnetic resonance angiography scans, decreased cerebrovascular reserve, increased size of juxtaluminal hypoechoic area, AsxCS progression, carotid plaque ulceration, and intraplaque hemorrhage. Treatment of patients with AsxCS should be individualized, taking into consideration individual patient preferences and needs, clinical and imaging characteristics, and cultural, ethnic, and social factors. Solid evidence supporting or refuting an association between AsxCS and cognitive dysfunction is lacking.

CONCLUSIONS

The optimal management of patients with AsxCS should include BMT for all individuals and a prophylactic carotid revascularization procedure (CEA, CAS, or TCAR) for some asymptomatic patient subgroups, additionally taking into consideration individual patient needs and preference, clinical and imaging characteristics, social and cultural factors, and the available stroke risk prediction models. Future studies should investigate the association between AsxCS with cognitive function and the role of carotid revascularization procedures in the progression or reversal of cognitive dysfunction.

Evaluating the influence of altered cerebral hemodynamics on cognitive performance in asymptomatic carotid artery stenosis: A systematic review

OBJECTIVE

Substantial controversy exists regarding asymptomatic carotid stenosis (ACS) and its potential role in the pathophysiology of cognitive impairment. If proven, this hypothesis may suggest an additional definition for symptomatic carotid disease that would alter current management. This study aimed to synthesize the literature evaluating the relationship between impaired cerebral hemodynamics and cognition in patients with ACS.

METHODS

A literature search was performed using MEDLINE, Embase, and EBM Reviews through May 2022. We included prospective case-control studies that used validated, objective measure(s) of either global cognition or one or more domains of cognitive function and assessed cerebrovascular reserve (CVR).

RESULTS

Five studies were included, comprising a total of 782 patients with moderate (50%-69%) to severe (70%-99%) ACS. Patients with ACS and impaired ipsilateral CVR demonstrated significant cognitive impairment compared with controls. Patients with unilateral or bilateral ACS and normal CVR had cognitive scores similar to controls. Those with bilateral CVR impairment demonstrated the lowest cognitive scores.

CONCLUSIONS

This review lends support to the claim that cognitive impairment, likely the result of impaired cerebral hemodynamics, is an under-recognized morbidity in patients with ACS. CVR may serve as an additional tool to determine whether patients are in fact symptomatic from their carotid stenosis and warrant consideration for intervention.

Arterial Spin Labeling (ASL) in Neuroradiological Diagnostics - Methodological Overview and Use Cases

BACKGROUND

 Arterial spin labeling (ASL) is a magnetic resonance imaging (MRI)-based technique using labeled blood-water of the brain-feeding arteries as an endogenous tracer to derive information about brain perfusion. It enables the assessment of cerebral blood flow (CBF).

METHOD

 This review aims to provide a methodological and technical overview of ASL techniques, and to give examples of clinical use cases for various diseases affecting the central nervous system (CNS). There is a special focus on recent developments including super-selective ASL (ssASL) and time-resolved ASL-based magnetic resonance angiography (MRA) and on diseases commonly not leading to characteristic alterations on conventional structural MRI (e. g., concussion or migraine).

RESULTS

 ASL-derived CBF may represent a clinically relevant parameter in various pathologies such as cerebrovascular diseases, neoplasms, or neurodegenerative diseases. Furthermore, ASL has also been used to investigate CBF in mild traumatic brain injury or migraine, potentially leading to the establishment of imaging-based biomarkers. Recent advances made possible the acquisition of ssASL by selective labeling of single brain-feeding arteries, enabling spatial perfusion territory mapping dependent on blood flow of a specific preselected artery. Furthermore, ASL-based MRA has been introduced, providing time-resolved delineation of single intracranial vessels.

CONCLUSION

 Perfusion imaging by ASL has shown promise in various diseases of the CNS. Given that ASL does not require intravenous administration of a gadolinium-based contrast agent, it may be of particular interest for investigations in pediatric cohorts, patients with impaired kidney function, patients with relevant allergies, or patients that undergo serial MRI for clinical indications such as disease monitoring.

KEY POINTS

  · ASL is an MRI technique that uses labeled blood-water as an endogenous tracer for brain perfusion imaging.. · It allows the assessment of CBF without the need for administration of a gadolinium-based contrast agent.. · CBF quantification by ASL has been used in several pathologies including brain tumors or neurodegenerative diseases.. · Vessel-selective ASL methods can provide brain perfusion territory mapping in cerebrovascular diseases.. · ASL may be of particular interest in patient cohorts with caveats concerning gadolinium administration..

Post-Stroke Brain Health Monitoring and Optimization: A Narrative Review

Significant advancements have been made in recent years in the acute treatment and secondary prevention of stroke. However, a large proportion of stroke survivors will go on to have enduring physical, cognitive, and psychological disabilities from suboptimal post-stroke brain health. Impaired brain health following stroke thus warrants increased attention from clinicians and researchers alike. In this narrative review based on an open timeframe search of the PubMed, Scopus, and Web of Science databases, we define post-stroke brain health and appraise the body of research focused on modifiable vascular, lifestyle, and psychosocial factors for optimizing post-stroke brain health. In addition, we make clinical recommendations for the monitoring and management of post-stroke brain health at major post-stroke transition points centered on four key intertwined domains: cognition, psychosocial health, physical functioning, and global vascular health. Finally, we discuss potential future work in the field of post-stroke brain health, including the use of remote monitoring and interventions, neuromodulation, multi-morbidity interventions, enriched environments, and the need to address inequities in post-stroke brain health. As post-stroke brain health is a relatively new, rapidly evolving, and broad clinical and research field, this narrative review aims to identify and summarize the evidence base to help clinicians and researchers tailor their own approach to integrating post-stroke brain health into their practices.

Cognition and Cerebral Blood Flow After Extracranial Carotid Revascularization for Carotid Atherosclerosis: A Systematic Review

PURPOSE

Extracranial atherosclerotic carotid stenosis is associated with inadequate cerebral blood flow (CBF) and cognitive dysfunction. The impact of extracranial carotid revascularization on cognition and how any cognitive change relates to changes in CBF are less clear. This review examines the effects of revascularization of extracranial carotid disease by carotid endarterectomy (CEA) or carotid stenting (CAS) on cognition, and how this relates to changes in CBF.

METHODS

A systematic review of existing reports in the Medline, Embase, and Cochrane databases was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis statement recommendations. All original retrospective or prospective studies and clinical trials that compared pre- and postoperative cognitive function and CBF in patients with extracranial carotid stenosis who underwent CEA or CAS versus a control group, published between January 1985 and December 2022, were identified and considered eligible for inclusion in this study.

FINDINGS

Seven studies (661 participants; 460 CEA or CAS) were identified. All were observational studies and of moderate to good methodologic quality. Six studies (619 participants; follow-up range 1 month to 2 years) demonstrated improvement in some cognitive domains following CEA or CAS, improvement in CBF following revascularization, and correlated some of these cognitive changes with changes in CBF. One study (42 participants; 3 months follow-up) found cognitive improvement following CEA, but found no improvement in CBF or any correlation between cognitive and CBF change. The literature however represented heterogenous study populations examining asymptomatic and/or symptomatic carotid stenosis, differing in treatment modality and criteria for control groups ranging from healthy volunteers to those with stenosis but not who underwent surgical revascularization, and finally, differing reporting methods. This heterogeneity precluded meta-analysis.

IMPLICATIONS

Definitive conclusions are limited by variation in cognitive function assessment, timing of testing, and how these are correlated to CBF. However, research suggests a potential improvement in cognition which may be associated with improvement in CBF, particularly in those patients who have more significant CBF deficit at baseline. Further studies are required to better understand this association and provide a clearer picture of the cognitive effects of carotid revascularization.

Cognitive functions and sense of coherence in patients with carotid artery stenosis-Preliminary report

Background

There is scarcely any data in the available literature on the relationship between sense of coherence (SOC) and cognitive functioning, and no information on the relationship between SOC and cognitive parameters in patients with carotid atherosclerosis.

Aim

The aim of this paper was to determine the relationship of SOC measured prior to carotid artery stenting (CAS) with neurocognitive functioning in patients with carotid atherosclerosis 12 months after CAS.

Methods

A total of 35 patients with carotid atherosclerosis completed the SOC-29 Orientation to Life Questionnaire (SOC-29) and completed a cognitive test battery twice, i.e., before (baseline-T1) and 12 months after stent implantation (follow-up-T2). Selected cognitive functions such as memory, attention, perception, visuospatial and executive functions and non-verbal fluency were assessed.

Results

One year after the procedure, patients with a higher SOC and sense of manageability present better performance in visual memory. Higher SOC and sense of meaningfulness are positively related to the speed of understanding the changing rules of card sorting (WCST).

Conclusion

Higher overall SOC and a component of sense of meaningfulness and manageability may be related to better cognitive functioning 1 year after the procedure.

Greater burden of white matter lesions and silent infarcts ipsilateral to carotid stenosis

OBJECTIVES

Carotid stenosis may cause silent cerebrovascular disease (CVD) through atheroembolism and hypoperfusion. If so, revascularization may slow progression of silent CVD. We aimed to compare the presence and severity of silent CVD to the degree of carotid bifurcation stenosis by cerebral hemisphere.

MATERIALS AND METHODS

Patients age ≥40 years with carotid stenosis >50% by carotid ultrasound who underwent MRI brain from 2011-2015 at Mayo Clinic were included. Severity of carotid stenosis was classified by carotid duplex ultrasound as 50-69% (moderate), 70-99% (severe), or occluded. White matter lesion (WML) volume was quantified using an automated deep-learning algorithm applied to axial T2 FLAIR images. Differences in WML volume and prevalent silent infarcts were compared across hemispheres and severity of carotid stenosis.

RESULTS

Of the 183 patients, mean age was 71±10 years, and 39.3% were female. Moderate stenosis was present in 35.5%, severe stenosis in 46.5% and occlusion in 18.0%. Patients with carotid stenosis had greater WML volume ipsilateral to the side of carotid stenosis than the contralateral side (mean difference, 0.42±0.21cc, p=0.046). Higher degrees of stenosis were associated with greater hemispheric difference in WML volume (moderate vs. severe; 0.16±0.27cc vs 0.74±0.31cc, p=0.009). Prevalence of silent infarct was 23.5% and was greater on the side of carotid stenosis than the contralateral side (hemispheric difference 8.8%±3.2%, p=0.006). Higher degrees of stenosis were associated with higher burden of silent infarcts (moderate vs severe, 10.8% vs 31.8%; p=0.002).

CONCLUSIONS

WML and silent infarcts were greater on the side of severe carotid stenosis.

Cognitive function after carotid endarterectomy in asymptomatic patients

Asymptomatic carotid stenosis has been shown to be associated with progressive neurocognitive decline, but the effects of carotid endarterectomy (CEA) on this are not well defined. Due to the wide heterogeneity of studies and lack of standardization in cognitive function tests and study design, there is mounting scientific evidence to support the notion that CEA is effective in reversing or slowing neurocognitive decline; however, definitive conclusions are difficult to make. Further, while the association between ACS and cognitive decline has been well document, a direct etiological role has not been established. More research is required to elucidate the relationship between asymptomatic carotid stenosis and the benefit of carotid endarterectomy and its potential protective effects regarding cognitive decline. This article aims to review current evidence in preoperative and postoperative cognitive function in asymptomatic patients with carotid stenosis undergoing CEA.

Cortical Thinning in High-Grade Asymptomatic Carotid Stenosis

BACKGROUND AND PURPOSE

High-grade carotid artery stenosis may alter hemodynamics in the ipsilateral hemisphere, but consequences of this effect are poorly understood. Cortical thinning is associated with cognitive impairment in dementia, head trauma, demyelination, and stroke. We hypothesized that hemodynamic impairment, as represented by a relative time-to-peak (TTP) delay on MRI in the hemisphere ipsilateral to the stenosis, would be associated with relative cortical thinning in that hemisphere.

METHODS

We used baseline MRI data from the NINDS-funded Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis-Hemodynamics (CREST-H) study. Dynamic contrast susceptibility MR perfusion-weighted images were post-processed with quantitative perfusion maps using deconvolution of tissue and arterial signals. The protocol derived a hemispheric TTP delay, calculated by subtraction of voxel values in the hemisphere ipsilateral minus those contralateral to the stenosis.

RESULTS

Among 110 consecutive patients enrolled in CREST-H to date, 45 (41%) had TTP delay of at least 0.5 seconds and 9 (8.3%) subjects had TTP delay of at least 2.0 seconds, the maximum delay measured. For every 0.25-second increase in TTP delay above 0.5 seconds, there was a 0.006-mm (6 micron) increase in cortical thickness asymmetry. Across the range of hemodynamic impairment, TTP delay independently predicted relative cortical thinning on the side of stenosis, adjusting for age, sex, hypertension, hemisphere, smoking history, low-density lipoprotein cholesterol, and preexisting infarction (P=0.032).

CONCLUSIONS

Our findings suggest that hemodynamic impairment from high-grade asymptomatic carotid stenosis may structurally alter the cortex supplied by the stenotic carotid artery.

Carotid Sources of Stroke

The ancient Greeks used the term karotides for the great arteries in the neck, compression of which could plunge the victim into karoun: deep sleep or stupor. The artery name aside, studies of the patterns of brain infarction and their clinical severity have been an unbroken chain of growing sophistication in the past 150 years. Two main patterns emerged: perfusion failure with high-convexity infarction from hemodynamically important ipsilateral carotid stenosis or embolism from nonstenosing carotid plaque.

Does Current Evidence Support Carotid Artery Stenting for Asymptomatic Patients?

Carotid interventions, carotid endarterectomy and carotid artery stenting (CAS) have proven to be effective treatments for the prevention of ischaemic stroke in recently symptomatic patients. Most studies were conducted before the development of strict statin guidance and the systematic use of antiplatelet drugs. The advances in medical treatments have raised questions regarding the benefit of carotid endarterectomy or CAS, especially for high-grade asymptomatic internal carotid artery stenosis. Reviewing the literature indicates that carotid artery stenosis of any degree is a relatively weak predictor of ipsilateral stroke, in the absence of recent symptoms referable to the carotid disease. This risk does not appear reduced by revascularisation by CAS if added to modern day best medical therapy. On-going trials are key to understanding if current techniques can provide an additional benefit.

Cognitive Functions after Carotid Artery Stenting-1-Year Follow-Up Study

Background: The revascularization of carotid arteries minimizes the risk of future cerebral stroke and usually improves cognitive functions. The aim of this study was to assess changes in cognitive function and verify the hypothesis assuming an improvement of selected cognitive functions—psychomotor speed, visuospatial episodic memory, executive function and verbal fluency—in patients after carotid artery stenting during a 12-month follow-up. Methods: 47 persons subject to CAS, including 13 symptomatic persons, were examined before and 12 months after a procedure with a psychological test battery (digit symbol test—DS, Rey–Osterrieth complex figure test—ROCF, Wisconsin Card Sorting Test—WCST, letter verbal fluency—LVF). Sociodemographic data and clinical parameters were acquired from an author questionnaire. Results: The one-year follow-up, after the performed CAS procedure, demonstrated a significant improvement of psychomotor speed, visuospatial episodic memory, and executive function. No changes in the area of verbal fluency or decline in any of cognitive functions under analysis were observed. Conclusions: Carotid artery stenting improves cognitive functioning, both in the area of basic and more complex cognitive functions in persons with carotid atherosclerosis.

Lessons From ACST-2

The recent 130-center, international, second ACST trial (Asymptomatic Carotid Surgery Trial) involving 3625 patients found that regardless of whether a patient underwent stenting or endarterectomy, the periprocedural risk of disabling or fatal stroke was about 1% and the 5-year estimated risk of nonprocedural disabling or fatal stroke was 2.5%. With advances in technique, technology, and patient selection, stenting done by appropriately trained and experienced operators can achieve safety and efficacy comparable to endarterectomy for asymptomatic patients. The ongoing CREST-2 trial (Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial) will clarify whether revascularization, by either stenting or endarterectomy, remains an important therapeutic goal in the setting of modern intensive medical therapy.

Vascular Cognitive Impairment (VCI)

Vascular cognitive impairment (VCI) is predominately caused by vascular risk factors and cerebrovascular disease. VCI includes a broad spectrum of cognitive disorders, from mild cognitive impairment to vascular dementia caused by ischemic or hemorrhagic stroke, and vascular factors alone or in a combination with neurodegeneration including Alzheimer's disease (AD) and AD-related dementia. VCI accounts for at least 20-40% of all dementia diagnosis. Growing evidence indicates that cerebrovascular pathology is the most important contributor to dementia, with additive or synergistic interactions with neurodegenerative pathology. The most common underlying mechanism of VCI is chronic age-related dysregulation of CBF, although other factors such as inflammation and cardiovascular dysfunction play a role. Vascular risk factors are prevalent in VCI and if measured in midlife they predict cognitive impairment and dementia in later life. Particularly, hypertension, high cholesterol, diabetes, and smoking at midlife are each associated with a 20 to 40% increased risk of dementia. Control of these risk factors including multimodality strategies with an inclusion of lifestyle modification is the most promising strategy for treatment and prevention of VCI. In this review, we present recent developments in age-related VCI, its mechanisms, diagnostic criteria, neuroimaging correlates, vascular risk determinants, and current intervention strategies for prevention and treatment of VCI. We have also summarized the most recent and relevant literature in the field of VCI.

Optimal management of asymptomatic carotid stenosis in 2021: the jury is still out. An International, multispecialty, expert review and position statement

OBJECTIVES

The recommendations of international guidelines for the management of asymptomatic carotid stenosis (ACS) often vary considerably and extend from a conservative approach with risk factor modification and best medical treatment (BMT) alone, to a more aggressive approach with a carotid intervention plus BMT. The aim of the current multispecialty position statement is to reconcile the conflicting views on the topic.

MATERIALS AND METHODS

A literature review was performed with a focus on data from recent studies.

RESULTS

Several clinical and imaging high-risk features have been identified that are associated with an increased long-term ipsilateral ischemic stroke risk in patients with ACS. Such high-risk clinical/imaging features include intraplaque hemorrhage, impaired cerebrovascular reserve, carotid plaque echolucency/ulceration/ neovascularization, a lipid-rich necrotic core, a thin or ruptured fibrous cap, silent brain infarction, a contralateral transient ischemic attack/stroke episode, male patients <75 years and microembolic signals on transcranial Doppler. There is growing evidence that 80-99% ACS indicate a higher stroke risk than 50-79% stenoses.

CONCLUSIONS

Although aggressive risk factor control and BMT should be implemented in all ACS patients, several high-risk features that may increase the risk of a future cerebrovascular event are now documented. Consequently, some guidelines recommend a prophylactic carotid intervention in high-risk patients to prevent future cerebrovascular events. Until the results of the much-anticipated randomized controlled trials emerge, the jury is still out regarding the optimal management of ACS patients.

Optimal Management of Asymptomatic Carotid Stenosis in 2021: The Jury is Still Out. An International, Multispecialty, Expert Review and Position Statement

OBJECTIVES

The recommendations of international guidelines for the management of asymptomatic carotid stenosis (ACS) often vary considerably and extend from a conservative approach with risk factor modification and best medical treatment (BMT) alone, to a more aggressive approach with a carotid intervention plus BMT. The aim of the current multispecialty position statement is to reconcile the conflicting views on the topic.

MATERIALS AND METHODS

A literature review was performed with a focus on data from recent studies.

RESULTS

Several clinical and imaging high-risk features have been identified that are associated with an increased long-term ipsilateral ischemic stroke risk in patients with ACS. Such high-risk clinical/imaging features include intraplaque hemorrhage, impaired cerebrovascular reserve, carotid plaque echolucency/ulceration/ neovascularization, a lipid-rich necrotic core, a thin or ruptured fibrous cap, silent brain infarction, a contralateral transient ischemic attack/stroke episode, male patients < 75 years and microembolic signals on transcranial Doppler. There is growing evidence that 80-99% ACS indicate a higher stroke risk than 50-79% stenoses.

CONCLUSIONS

Although aggressive risk factor control and BMT should be implemented in all ACS patients, several high-risk features that may increase the risk of a future cerebrovascular event are now documented. Consequently, some guidelines recommend a prophylactic carotid intervention in high-risk patients to prevent future cerebrovascular events. Until the results of the much-anticipated randomized controlled trials emerge, the jury is still out regarding the optimal management of ACS patients.

Cognitive Functions in Patients after Carotid Artery Revascularization-A Narrative Review

Carotid revascularization may lead to improved cognitive function beyond stroke prevention. This article summarizes the conclusions from available studies on the effects of carotid reperfusion procedures on cognitive function. The papers cited used different neuropsychological tests for cognitive assessment, resulting in different methodologies and the results obtained were not always convergent. However, most studies reported an improvement in neurocognitive abilities after both vascular interventions, but a more precise assessment of the specific benefits is still awaited. Clinical determinants to predict the effects of these treatments on cognitive function are still being sought, but results are not yet satisfactory. In view of these studies, carotid stenosis seems to be an independent risk factor for cognitive deterioration, and the main mechanisms responsible are embolism and cerebral hypoperfusion. The aim of this study is to order the knowledge about the effects of carotid artery stenting (CAS) and endarterectomy (CEA) on neurocognitive functions and to verify the usefulness of using these treatments.

Baseline Cognitive Impairment in Patients With Asymptomatic Carotid Stenosis in the CREST-2 Trial

BACKGROUND AND PURPOSE

Studies of carotid artery disease have suggested that high-grade stenosis can affect cognition, even without stroke. The presence and degree of cognitive impairment in such patients have not been reported and compared with a demographically matched population-based cohort.

METHODS

We studied cognition in 1000 consecutive CREST-2 (Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Trial) patients, a treatment trial for asymptomatic carotid disease. Cognitive assessment was after randomization but before assigned treatment. The cognitive battery was developed in the general population REGARDS Study (Reasons for Geographic and Racial Differences in Stroke), involving Word List Learning Sum, Word List Recall, and Word List fluency for animal names and the letter F. The carotid stenosis patients were >45 years old with ≥70% asymptomatic carotid stenosis and no history of prevalent stroke. The distribution of cognitive performance for the patients was standardized, accounting for age, race, and education using performance from REGARDS, and after further adjustment for hypertension, diabetes, dyslipidemia, and smoking. Using the Wald Test, we tabulated the proportion of Z scores less than the anticipated deviate for the population-based cohort for representative percentiles.

RESULTS

There were 786 baseline assessments. Mean age was 70 years, 58% men, and 52% right-sided stenosis. The overall Z score for patients was significantly below expected for higher percentiles (P<0.0001 for 50th, 75th, and 95th percentiles) and marginally below expected for the 25th percentile (P=0.015). Lower performance was attributed largely to Word List Recall (P<0.0001 for all percentiles) and for Word List Learning (50th, 75th, and 95th percentiles below expected, P≤0.01). The scores for left versus right carotid disease were similar.

CONCLUSIONS

Baseline cognition of patients with severe carotid stenosis showed below normal cognition compared to the population-based cohort, controlling for demographic and cardiovascular risk factors. This cohort represents the largest group to date to demonstrate that poorer cognition, especially memory, in this disease.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02089217.

Cognitive Impairment and Dementia After Stroke: Design and Rationale for the DISCOVERY Study

Stroke is a leading cause of the adult disability epidemic in the United States, with a major contribution from poststroke cognitive impairment and dementia (PSCID), the rates of which are disproportionally high among the health disparity populations. Despite the PSCID's overwhelming impact on public health, a knowledge gap exists with regard to the complex interaction between the acute stroke event and highly prevalent preexisting brain pathology related to cerebrovascular and Alzheimer disease or related dementia. Understanding the factors that modulate PSCID risk in relation to index stroke event is critically important for developing personalized prognostication of PSCID, targeted interventions to prevent it, and for informing future clinical trial design. The DISCOVERY study (Determinants of Incident Stroke Cognitive Outcomes and Vascular Effects on Recovery), a collaborative network of thirty clinical performance clinical sites with access to acute stroke populations and the expertise and capacity for systematic assessment of PSCID will address this critical challenge. DISCOVERY is a prospective, multicenter, observational, nested-cohort study of 8000 nondemented ischemic and hemorrhagic stroke patients enrolled at the time of index stroke and followed for a minimum of 2 years, with serial cognitive evaluations and assessments of functional outcome, with subsets undergoing research magnetic resonance imaging and positron emission tomography and comprehensive genetic/genomic and fluid biomarker testing. The overall scientific objective of this study is to elucidate mechanisms of brain resilience and susceptibility to PSCID in diverse US populations based on complex interplay between life-course exposure to multiple vascular risk factors, preexisting burden of microvascular and neurodegenerative pathology, the effect of strategic acute stroke lesions, and the mediating effect of genomic and epigenomic variation.

Decreasing Spatial Variability of Individual Watershed Areas by Revascularization Therapy in Patients With High-Grade Carotid Artery Stenosis

BACKGROUND

Carotid artery stenosis can impair cerebral hemodynamics especially within watershed areas (WSAs) between vascular territories. WSAs can shift because of collateral flow, which may be an indicator for increased hemodynamic implications and hence higher risk for ischemic stroke. However, whether revascularization treatment can reverse the spatial displacement of individual WSAs (iWSAs) and impaired hemodynamics remains unknown.

HYPOTHESIS

That iWSAs spatially normalize because of hemodynamic improvement resulting from revascularization treatment.

STUDY TYPE

Prospective.

POPULATION

Sixteen patients with unilateral, high-grade carotid artery stenosis confirmed by duplex ultrasonography and 17 healthy controls.

FIELD STRENGTH/SEQUENCES

A 3 T-magnetization-prepared rapid acquisition gradient echo (MPRAGE), gradient-echo echo planar dynamic susceptibility contrast (DSC), and fluid-attenuated inversion recovery (FLAIR) sequences. Additionally, contrast-enhanced 3D gradient echo magnetic resonance angiography (MRA) and diffusion-tensor imaging (DTI) spin-echo echo planar imaging were performed.

ASSESSMENT

iWSAs were delineated by a recently proposed procedure based on time-to-peak maps from DSC perfusion MRI, which were also used to evaluate perfusion delay. We spatially compared iWSAs and perfusion delay before and after treatment (endarterectomy or stenting). Additionally, the Circle of Willis collateralization status was evaluated, and basic cognitive testing was conducted.

STATISTICAL TESTS

Statistical tests included two-sample t-tests and Chi-squared tests. A P value < 0.05 was considered to be statistically significant.

RESULTS

After revascularization, patients showed a significant spatial shift of iWSAs and significantly reduced perfusion delay ipsilateral to the stenosis. Spatial shift of iWSA (P = 0.007) and cognitive improvement (P = 0.013) were more pronounced in patients with poor pre-existing collateralization. Controls demonstrated stable spatial extent of iWSAs (P = 0.437) and symmetric perfusion delays between hemispheres over time (P = 0.773).

DATA CONCLUSION

These results demonstrate the normalization of iWSA and impaired hemodynamics after revascularization in patients with high-grade carotid artery stenosis.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Surface-based Cortical Morphometry, White Matter Hyperintensity, and Multidomain Cognitive Performance in Asymptomatic Carotid Stenosis

Carotid stenosis is a major contributor to vascular dementia. Recent studies suggest that even clinically "asymptomatic" carotid stenosis is linked with cognitive decline and neuroimaging changes. Here we examined surface-based cortical morphometry, white matter hyperintensity (WMH), and multidomain cognitive performance in unilateral severe (>70% narrowing) asymptomatic carotid stenosis (SACS). We included 24 SACS patients (19 males/5 females; 64.25 ± 7.18 years) and 24 comorbidities-matched controls (19 males/5 females; 67.16 ± 6.10 years), and measured cortical thickness, sulcal depth, gyrification, cortical complexity, and WMH loads with structural MRI images. The SACS patients exhibited: (1) thinner cortex in bilateral somatosensory/motor, bilateral inferior frontal, bilateral fusiform, and left lateral temporal areas; (2) shallower sulci in left lateral temporal, parietal, insular and somatosensory/motor areas; (3) both hyper- and hypo-gyrification in lateral temporal and frontal cortices; (4) lower complexity (fractal dimension) in left insular and right superior temporal areas. Further association analyses showed that the cortical alterations were significantly correlated with verbal memory and WMH burden in SACS. These results suggest that SACS patients present a left-dominated damage tendency, especially in the Perisylvian cortices that span across several large-scale systems of somatosensory/motor and language. Our findings also provide cortical anatomy evidence for cognitive impairment in SACS, suggesting a neuroanatomical predisposition to dementia and cerebrovascular events.

Changes in Cognition and Hemodynamics 1 Year after Carotid Endarterectomy for Asymptomatic Stenosis

OBJECTIVES

 The impact of a change in hemodynamics on cognitive skills in patients with asymptomatic carotid stenosis (ACS) after carotid endarterectomy (CEA) remains unclear. The aim of this study was to evaluate the results of CEA for ACS at 1 year by assessing the changes in anterior, middle, and posterior cerebral artery blood flow in tandem with changes in cognitive efficiency.

METHODS

 Flow volume in cerebral arteries using quantitative magnetic resonance angiography was measured in a group of 14 males and 5 females before and at 1 year after CEA for ACS. Cognitive efficiency was assessed by Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The values of flow volume were processed using simple ratio (SR) and were used for covariance analyses with changes in cognitive skills after CEA.

RESULTS

 A significant improvement in cognitive efficiency indexes of immediate memory and visuospatial perception at 1 year after CEA for ACS was observed. Simultaneously, a significant deterioration of speech index was noted. During the analysis of association between flow and cognition, the highest correlation could be seen between the middle cerebral artery (MCA) flow and the visuospatial perception. A change in posterior cerebral artery (PCA) flow was associated with an increase in immediate memory index and anterior cerebral artery (ACA) flow change with the speech index.

CONCLUSION

 Convergence of data supporting the association between revascularization and cognitive improvement were added in a small, single-center cohort of ACS patients undergoing CEA. No significant differences in cognition were seen between preoperative findings and at 1 year after CEA. Visuospatial perception improvement was linked to flow change in MCA, immediate memory improvement to flow change in PCA, and speech index change to flow change in ACA. Methodical limitations of this small study preclude formulating larger generalizations. Hemodynamic factors in CEA should be assessed in a larger-scale study.

Subclinical Atherosclerosis and Brain Metabolism in Middle-Aged Individuals: The PESA Study

BACKGROUND

Atherosclerosis has been linked to cognitive decline in late life; however, the impact of cardiovascular risk factors (CVRFs) and subclinical atherosclerosis on brain metabolism at earlier stages remains unexplored.

OBJECTIVES

This study sought to determine the association between brain metabolism, subclinical atherosclerosis, and CVRFs in middle-aged asymptomatic individuals.

METHODS

This study included 547 asymptomatic middle-aged participants (50 ± 4 years, 82% men) from the PESA (Progression of Early Subclinical Atherosclerosis) study with evidence of subclinical atherosclerosis. Participants underwent ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography. Global brain FDG uptake and voxel-wise analyses were used to evaluate the associations of cerebral metabolism with CVRFs and atherosclerotic plaque burden in carotids and femorals assessed by 3-dimensional vascular ultrasound.

RESULTS

Global FDG uptake showed an inverse correlation with 30-year Framingham Risk Score (FRS) (β = -0.15, p < 0.001). This association was mainly driven by the presence of hypertension (d = 0.36, p < 0.001). Carotid plaque burden was inversely associated with global brain FDG uptake (β = -0.16, p < 0.001), even after adjusting for 30-year FRS. Voxel-wise approaches revealed that the brain areas most strongly affected by hypometabolism in association with 30-year FRS, hypertension, and carotid plaque burden were parietotemporal regions (angular, supramarginal, and inferior/middle temporal gyri) and the cingulate gyrus.

CONCLUSIONS

In asymptomatic middle-aged individuals, cardiovascular risk is associated with brain hypometabolism, with hypertension being the modifiable CVRF showing the strongest association. Subclinical carotid plaque burden is also linked to reduced brain metabolism independently of CVRFs. Cerebral areas showing hypometabolism include those known to be affected in dementia. These data reinforce the need to control CVRFs early in life in order to potentially reduce the brain's midlife vulnerability to future cognitive dysfunction.

Hemodynamic impairments within individual watershed areas in asymptomatic carotid artery stenosis by multimodal MRI

Improved understanding of complex hemodynamic impairments in asymptomatic internal carotid artery stenosis (ICAS) is crucial to better assess stroke risks. Multimodal MRI is ideal for measuring brain hemodynamics and has the potential to improve diagnostics and treatment selections. We applied MRI-based perfusion and oxygenation-sensitive imaging in ICAS with the hypothesis that the sensitivity to hemodynamic impairments will improve within individual watershed areas (iWSA). We studied cerebral blood flow (CBF), cerebrovascular reactivity (CVR), relative cerebral blood volume (rCBV), relative oxygen extraction fraction (rOEF), oxygen extraction capacity (OEC) and capillary transit-time heterogeneity (CTH) in 29 patients with asymptomatic, unilateral ICAS (age 70.3 ± 7.0 y) and 30 age-matched healthy controls. In ICAS, we found significant impairments of CBF, CVR, rCBV, OEC, and CTH (strongest lateralization ΔCVR = -24%), but not of rOEF. Although the spatial overlap of compromised hemodynamic parameters within each patient varied in a complex manner, most pronounced changes of CBF, CVR and rCBV were detected within iWSAs (strongest effect ΔCVR = +117%). At the same time, CTH impairments were iWSA independent, indicating widespread dysfunction of capillary-level oxygen diffusivity. In summary, complementary MRI-based perfusion and oxygenation parameters offer deeper perspectives on complex microvascular impairments in individual patients. Furthermore, knowledge about iWSAs improves the sensitivity to hemodynamic impairments.

Surgical Approaches to Stroke Risk Reduction

PURPOSE OF REVIEW

Surgical vascular intervention is an important tool in reducing the risk of stroke. This article examines the evidence for using the available options.

RECENT FINDINGS

Carotid endarterectomy is an effective treatment option for reducing the risk of stroke in appropriately selected patients. Patients should be stratified for future stroke risk based on both the degree of stenosis and the presence of symptoms referable to the culprit lesion. Carotid stenting is also useful in reducing stroke risk, again in carefully selected patients. Because of the publication of significant data regarding both carotid endarterectomy and carotid artery stenting in the last several years, selection can be far more personalized and refined for individual patients based on demographics, sex, patient preference, and medical comorbidities. Routine extracranial-intracranial bypass surgery remains unproven as a therapeutic option for large vessel occlusion in reducing the incidence of ischemic stroke although some carefully screened patient populations remaining at high risk may benefit; procedural risks and pathology related to alterations in blood flow dynamics are challenges to overcome. Indirect revascularization remains an appropriate solution for carefully selected patients with cerebral large vessel steno-occlusive disease, and multiple variations of surgical technique are patient specific. Indirect revascularization may benefit from clinical trials with larger patient populations for validation in specific pathologies and offers the advantages of lower surgical complication rates and reduced risk of pathologic responses to altered cerebral flow dynamics.

SUMMARY

Surgical solutions to reduce stroke risk provide important alternatives in appropriately selected patients and should be considered in addition to medical management and lifestyle modification for optimizing patient outcomes.

Trends and controversies in carotid artery stenosis treatment

Despite the completion of several multi-center trials, the management of carotid stenosis remains in flux. Key questions include the role of intensive medical management in the treatment of asymptomatic carotid stenosis. In addition, identification of patients with symptomatic stenosis who will most benefit from carotid revascularization remains a priority. The role of newer imaging techniques such as carotid plaque analysis with magnetic resonance imaging is also challenging current treatment paradigms. These topics are explored in this topical update.

Quantification of brain oxygen extraction and metabolism with [15O]-gas PET: A technical review in the era of PET/MRI

Oxygen extraction fraction (OEF) and the cerebral metabolic rate of oxygen (CMRO₂) are key cerebral physiological parameters to identify at-risk cerebrovascular patients and understand brain health and function. PET imaging with [¹⁵O]-oxygen tracers, either through continuous or bolus inhalation, provides non-invasive assessment of OEF and CMRO₂. Numerous tracer delivery, PET acquisition, and kinetic modeling approaches have been adopted to map brain oxygenation. The purpose of this technical review is to critically evaluate different methods for [¹⁵O]-gas PET and its impact on the accuracy and reproducibility of OEF and CMRO₂ measurements. We perform a meta-analysis of brain oxygenation PET studies in healthy volunteers and compare between continuous and bolus inhalation techniques. We also describe OEF metrics that have been used to detect hemodynamic impairment in cerebrovascular disease. For these patients, advanced techniques to accelerate the PET scans and potential synthesis with MRI to avoid arterial blood sampling would facilitate broader use of [¹⁵O]-oxygen PET for brain physiological assessment.

Cognitive Impairment Correlates Linearly with Mean Flow Velocity by Transcranial Doppler below a Definable Threshold

INTRODUCTION

Low cerebral blood flow can affect cognition in patients with high-grade asymptomatic internal carotid artery stenosis. Current clinical algorithms use stroke risk to determine which patients should undergo revascularization without considering cognitive decline. Although correlations between low-flow and cognitive impairment have been reported, it is not known whether a threshold exists below which such a correlation expresses itself. Such information would be critical in treatment decisions about whether to intervene in patients with high-grade carotid artery stenosis who are at risk for cognitive decline.

OBJECTIVE

To determine how reduced blood flow correlates with lower cognitive scores.

METHODS

Patients with ≥80% unilateral internal carotid artery stenosis with no history of stroke were recruited from inpatient and outpatient practices at a single, large, comprehensive stroke center. Patients underwent bilateral insonation of middle cerebral arteries with standard 2-Hz probes over the temporal windows with transcranial Doppler. Cognitive assessments were performed by an experienced neuropsychologist using a cognitive battery comprising 14 standardized tests with normative samples grouped by age. Z-scores were generated for each test and averaged to obtain a composite Z-score for each patient. Multivariable linear regression examined associations between mean flow velocity (MFV) and composite Z-score, adjusting for age, education, and depression. The Davies test was used to determine if there was a breakpoint for a non-zero difference in slope of a segmented relationship over the range of composite Z-score values.

RESULTS

Forty-two patients with unilateral high-grade internal carotid artery stenosis without stroke were enrolled (26 males, age = 74 ± 9 years, education = 16 ± 3 years). Average composite Z-score was -0.31 SD below the age-specific normative mean (range -2.8 to +1.2 SD). In linear regression adjusted for age, education, and depression, MFV correlated with cognitive Z-score (β = 0.308, p = 0.043). A single breakpoint in the range of composite Z-scores was identified at 45 cm/s. For MFV <45 cm/s, Z-score decreased 0.05 SD per cm/s MFV (95% CI: 0.01-0.10). For MFV >45 cm/s, Z-score change was nonsignificant (95% CI: -0.07 to 0.05).

CONCLUSIONS

In high-grade, asymptomatic carotid artery stenosis, cognitive impairment correlated linearly with lower flow in the hemisphere fed by the occluded internal carotid artery, but only below a threshold of MFV = 45 cm/s. Identifying a hemodynamic threshold for cognitive decline using a simple, noninvasive method may influence revascularization decision-making in otherwise "asymptomatic" carotid disease.

Poststroke Montreal Cognitive Assessment and Recurrent Stroke in Patients With Symptomatic Intracranial Atherosclerosis

BACKGROUND AND PURPOSE

Cognitive impairment occurs in 20%-40% of stroke patients and is a predictor of long-term morbidity and mortality. In this study, we aim to determine the association between poststroke cognitive impairment and stroke recurrence risk, in patients with anterior versus posterior circulation intracranial stenosis.

METHODS

This is a post-hoc analysis of the Stenting and Aggressive Medical Therapy for Preventing Recurrent Stroke in Intracranial Stenosis (SAMMPRIS) trial. The primary predictor was poststroke cognitive function measured by Montreal Cognitive Assessment (MOCA) at 3-6 months and the primary outcome was recurrent ischemic stroke. We used univariate and multivariable cox-regression models to determine the associations between MOCA at 3-6 months and recurrent stroke.

RESULTS

Of the 451 patients enrolled in SAMMPRIS, 393 patients met the inclusion criteria. The mean age of the sample (in years) was 59.5 ± 11.3, 62.6% (246 of 393) were men. Fifty patients (12.7%) had recurrent ischemic stroke during a mean follow up of 2.7 years. The 3-6 month MOCA score was performed on 351 patients. In prespecified multivariable models, there was an association between 3 and 6 month MOCA and recurrent stroke (hazard ratio [HR] per point increase .93 95% confidence interval [CI] .88-.99, P = .040). This effect was present in anterior circulation stenosis (adjusted HR per point increase .92 95% CI .85-0.99, P = .022) but not in posterior circulation artery stenosis (adjusted HR per point increase 1.00 95% .86-1.16, P = .983).

CONCLUSIONS

Overall, we found weak associations and trends between MoCA at 3-6 months and stroke recurrence but more notable and stronger associations in certain subgroups. Since our study is underpowered, larger studies are needed to validate our findings and determine the mechanism(s) behind this association.

National Institutes of Health StrokeNet Training Core

Background and Purpose- The National Institutes of Health (NIH) StrokeNet provides a nationwide infrastructure to advance stroke research. Capitalizing on this unique opportunity, the NIH StrokeNet Training Core (NSTC) was established with the overarching goal of enhancing the professional development of a diverse spectrum of professionals who are embedded in the stroke clinical trials network of the NIH StrokeNet. Methods- This special report provides a descriptive account of the rationale, organization, and activities of the NSTC since its inception in 2013. Current processes and their evolution over time for facilitating training of NIH StrokeNet trainees have been highlighted. Data collected for monitoring training are summarized. Outcomes data (publications and grants) collected by NSTC was supplemented by publicly available resources. Results- The NSTC comprises of cross-network faculty, trainees, and education coordinators. It helps in the development and monitoring of training programs and organizes educational and career development activities. Trainees are provided directed guidance towards their mandated research projects, including opportunities to present at the International Stroke Conference. The committee has focused on developing sustainable models of peer-to-peer interaction and cross-institutional mentorships. A total of 124 professionals (43.7% female, 10.5% underrepresented minorities) have completed training between 2013 and 2018, of whom 55% were clinical vascular neurologists. Of the total, 85% transitioned to a formal academic position and 95% were involved in stroke research post-training. Altogether, 1659 indexed publications have been authored or co-authored by NIH StrokeNet Trainees, of which 58% were published during or after their training years. Based on data from 109 trainees, 33% had submitted 72 grant proposals as principal or co-principal investigators of which 22.2% proposals have been funded. Conclusions- NSTC has provided a foundation to foster nationwide training in stroke research. Our data demonstrate strong contribution of trainees towards academic scholarship. Continued innovation in educational methodologies is required to adapt to unique training opportunities such as the NIH StrokeNet.

Frequent Cognitive Impairment in Patients With Disorders Along the Heart-Brain Axis

Background and Purpose—

Patients with cardiovascular disease are at increased risk for cognitive decline. We studied the occurrence and profile of cognitive impairment in 3 patient groups as exemplar conditions of hemodynamic disturbances at different levels of the heart-brain axis, including patients with heart failure (HF), carotid occlusive disease (COD), and patients with cognitive complaints and vascular brain injury on magnetic resonance imaging (possible vascular cognitive impairment [VCI]).

Methods—

In 555 participants (160 HF, 107 COD, 160 possible VCI, 128 reference participants; 68±9 years; 36% F; Mini-Mental State Examination 28±2), we assessed cognitive functioning with a comprehensive test battery. Test scores were transformed into z -scores. Compound z -scores were constructed for: memory, language, attention/psychomotor speed, executive functioning, and global cognitive functioning. We rated cognitive domains as impaired when z -score≤−1.5. Based on the number of impaired domains, patients were classified as cognitively normal, minor, or major cognitive impairment. We used general linear models and χ 2 tests to compare cognitive functioning between patient groups and the reference group.

Results—

Age, sex, and education adjusted global cognitive functioning z-score was lower in patients with COD (β [SE]=−0.46 [0.10], P <0.001) and possible VCI (β [SE]=−0.80 [0.09], P <0.001) compared with reference participants. On all domains, z -scores were lower in patients with COD and possible VCI compared with reference participants. Patients with HF had lower z-scores on attention/speed and language compared with reference participants. Cognitive impairment was observed in 18% of HF, 36% of COD, and 45% possible VCI. There was no difference in profile of impaired cognitive domains between patient groups. Memory and attention-psychomotor speed were most commonly affected, followed by executive functioning and language.

Conclusions—

A substantial part of patients with HF and COD had cognitive impairment, which warrants vigilance for the occurrence of cognitive impairment. These results underline the importance of an integrative approach in medicine in patients presenting with disorders in the heart-brain axis.

Is Hemispheric Hypoperfusion a Treatable Cause of Cognitive Impairment?

PURPOSE OF REVIEW

To review the current literature that supports the notion that cerebral hemodynamic compromise from internal carotid artery stenosis may be a cause of vascular cognitive impairment that is amenable to treatment by revascularization.

RECENT FINDINGS

Converging evidence suggests that successful carotid endarterectomy and carotid artery stenting are associated with reversal of cognitive decline in many patients with severe but asymptomatic carotid artery stenosis. Most of these findings have been derived from cohort studies and comparisons with either normal or surgical controls. Failure to find treatment benefit in a number of studies appears to have been the result of patient heterogeneity or confounding from concomitant conditions independently associated with cognitive decline, such as heart failure and other cardiovascular risk factors, or failure to establish pre-procedure hemodynamic failure. Patients with severe carotid artery stenosis causing cerebral hemodynamic impairment may have a reversible cause of cognitive decline. None of the prior studies, however, were done in the context of a randomized clinical trial with large numbers of participants. The ongoing CREST-2 trial comparing revascularization with medical therapy versus medical therapy alone, and its associated CREST-H study determining whether cognitive decline is reversible among those with hemodynamic compromise may address this question.