Cerebral Collateral Circulation in Carotid Artery Disease

Carotid artery disease is common and increases the risk of stroke. However, there is wide variability on the severity of clinical manifestations of carotid disease, ranging from asymptomatic to fatal stroke. The collateral circulation has been recognized as an important aspect of cerebral circulation affecting the risk of stroke as well as other features of stroke presentation, such as stroke patterns in patients with carotid artery disease. The cerebral circulation attempts to maintain constant cerebral perfusion despite changes in systemic conditions, due to its ability to autoregulate blood flow. In case that one of the major cerebral arteries is compromised by occlusive disease, the cerebral collateral circulation plays an important role in preserving cerebral perfusion through enhanced recruitment of blood flow. With the advent of techniques that allow rapid evaluation of cerebral perfusion, the collateral circulation of the brain and its effectiveness may also be evaluated, allowing for prompt assessment of patients with acute stroke due to involvement of the carotid artery, and risk stratification of patients with carotid stenosis in chronic stages. Understanding the cerebral collateral circulation provides a basis for the future development of new diagnostic tools, risk stratification, predictive models and new therapeutic modalities. In the present review we discuss basic aspects of the cerebral collateral circulation, diagnostic methods to assess collateral circulation, and implications in occlusive carotid artery disease

Diagnosis of Symptomatic Intracranial Atherosclerotic Disease

Intracranial atherosclerotic stroke differs from extracranial atherosclerotic stroke in many aspects, including risk factors and stroke patterns. It occurs in association with in situ thrombotic occlusion, artery-to-artery embolism, branch occlusion, and hemodynamic insufficiency. Intracranial atherosclerotic stenosis (ICAS) could have only been diagnosed by transcranial Doppler (TCD) and transcranial color-coded sonography (TCCS), which are burdened by a risk of bias, or catheter angiography (DSA), which, on the contrary, is very precise, but rarely it is done in clinical practice due to its invasiveness. Computed tomography angiography (CT-A) and magnetic resonance imaging angiography (MR-A) have increased the identification of ICAS in a wider stroke population

Imaging in Acute Stroke

Imaging in the acute setting of suspected stroke is an important topic to all emergency physicians, neurologists, neurosurgeons and neuroradiologist. When it comes to imaging, the American College of Radiology (ACR) continually updates its guidelines for imaging pathways through the ACR Appropriateness Criteria.1,2 This article is a general review of the imaging modalities currently used to assess and help guide the treatment of strokes

Cerebral Circulation

Diagnostics and diseases related to the cerebrovascular system are constantly evolving and updating. 3D augmented reality or quantification of cerebral perfusion are becoming important diagnostic tools in daily practice and the role of the cerebral venous system is being constantly revised considering new theories such as that of “the glymphatic system.” This book provides updates on models, diagnosis, and treatment of diseases of the cerebrovascular system

Assessment of collaterals in acute ischaemic stroke using CT imaging techniques

There is growing evidence that the degree of collateral circulation in acute ischaemic stroke, and in particular of leptomeningeal collaterals, is a useful imaging marker that is correlated with various baseline and outcome clinical parameters. However, methods for assessing collaterals on acute ischaemic stroke are poorly standardized at present. In the first part of this master thesis, an in-depth systematic review of methods for assessing collaterals published between 2009 and 2017 is presented. The review shows that although DSA is still used as gold standard, there has been a shift towards CT- and MR- based imaging modalities, which offer equal or higher sensitivity while being at the same time less invasive for the patient. In particular, CT seems to be a good candidate for replacing DSA as gold standard in the future and one scoring method proposed by Tan et al. has been widely adopted in recent studies. However, there has been zero or minimal progress towards a standardized method since previously published reviews. In the second part of this thesis, a retrospective study conducted at the QEUH (Glasgow) to assess the reliability of collaterals on single-phase CTA is presented. CTA does not provide time-resolved information and this may lead to mislabeling of collaterals. The phase of acquisition of the scan should be taken into account when evaluating collaterals. From 4 past clinical trials, we identified paItients with confirmed ICA or MCA occlusion. Three temporal-MIP images were reconstructed from CTP for each patient, each image corresponding to one of arterial, equilibrium and venous phase of contrast enhancement. Collateral scores were measured on both the temporal-MIP images and on single-phase CTA angiography and it was found that there was substantial agreement between the scores if the CTA was acquired in the equilibrium phase but only moderate agreement if the CTA was acquired in the arterial or venous phase. This confirms that the arterial phase, despite being the preferred phase for assessing arterial occlusion and recanalization, is not the best phase for assessing collaterals and that a combination of CTA-CTP or a CTA scan employing a time-resolved protocol should be employed when evaluating collateral status in stroke patients

Comparison of extra cranial with intra cranial carotid artery disease in ischemic stroke

INTRODUCTION: Stroke is defined as developing symptoms or and signs of global or focal, loss of cerebral function with symptoms lasting for more than 24 hours or leading to death with no apparent cause other than vascular origin. Globally, the rate of occurrence of stroke is estimated as 400 - 800 per lakh of population. Around 57 lakh deaths occur due to stroke in a year. Approximately, 1.6 crore new acute strokes are reported yearly. Worldwide, stroke mortality is high in Eastern Europe and Asia. In India, the rate of occurrence of stroke is estimated as 90 - 222 per lakh of population. Approximately, 14 – 16 lakhs new acute strokes are reported yearly. 12% of them occur in the age group of less than 40 years. In fact, it is estimated that the incidence of stroke will reach one million annually by the year 2050. Stroke is a leading cause of long term disability in our society. As the longevity of the population increase, the incidence is on the rise. Adoption of western diet may further increase the prevalence and incidence of cardiovascular disease and stroke. Of the hundreds and thousands of stroke survivors each year, approximately 30% need support for day- to-day activities 20% need assistance with ambulation and 16% require institutional care. Hence the need for identifying stroke risk factors to the reduce morbidity and mortality due to stroke. AIM OF THE STUDY: To assess the following in patients with anterior circulation ischemic stroke: 1. Risk factors involved in carotid artery stroke. 2. Clinical profile, pattern of vascular involvement in carotid artery stroke. 3. Extra cranial internal carotid artery disease by carotid doppler. 4. Intracranial carotid artery disease by transcranial doppler in patients who showed extracranial internal carotid artery disease. 5. Comparing the concordance and discordance of carotid artery disease in extracranial and intracranial part of internal carotid artery. MATERIALS AND METHODS: This cross sectional study was conducted during Jan 2011 to Oct 2012 at Madras Institute of Neurology, Rajiv Gandhi Government General Hospital, and Chennai. Patients with clinical features suggestive of stroke were enrolled in this study; all were subjected to CT Brain, MRI Brain and Carotid Doppler. Inclusion Criteria: 1. All the patients with clinical feature suggestive of stroke, 2. Imaging showing ischemic infarct in the anterior circulation, 3. Carotid Doppler showing atherosclerotic carotid artery disease, 4. Patients with anterior circulation TIA. Exclusion Criteria: 1. All hemorrhagic strokes, 2. Posterior circulation stroke, 3. Patients without carotid artery disease on carotid doppler, 4. Patients with cardiac disease. RESULTS: Among the total 485 patients, 150 patients (30.9%) with posterior circulation stroke or venous infarcts, intra cerebral hemorrhage were excluded from the study. Remaining 335 patients were subjected to cardiac evaluation, of them 23 patients (6.8%) who showed cardiac abnormalities were excluded from the study. Out of the 312 patients only 70 patients who showed carotid artery disease in carotid doppler were enrolled in this study and subjected to transcranial doppler to study the intra cranial part of internal carotid artery involvement. CONCLUSION: 1. The common risk factors for carotid artery disease in our study are dyslipidemia, systemic hypertension, diabetes mellitus, smoking and alcohol consumption, in the order of occurrence. 2. Incidence of transient ischemic attack was high in patients with intracranial carotid artery disease indicating the need for intensive management of these patients to prevent morbidity and mortality 3. The most common radiological presentation is the territorial infarct involving the middle cerebral artery territory followed by watershed infarcts. 4. Most of the patients with extracranial internal carotid artery disease also had co-existing intracranial internal carotid artery disease which in turn may further lead to stroke. This emphasizes the need to search for intracranial disease in patients with extra cranial carotid artery disease. 5. Transcranial doppler can be used as a noninvasive initial screening tool for detecting intracranial internal carotid artery stenosis before considering any invasive investigation

A novel MRA-based framework for the detection of changes in cerebrovascular blood pressure.

Background: High blood pressure (HBP) affects 75 million adults and is the primary or contributing cause of mortality in 410,000 adults each year in the United States. Chronic HBP leads to cerebrovascular changes and is a significant contributor for strokes, dementia, and cognitive impairment. Non-invasive measurement of changes in cerebral vasculature and blood pressure (BP) may enable physicians to optimally treat HBP patients. This manuscript describes a method to non-invasively quantify changes in cerebral vasculature and BP using Magnetic Resonance Angiography (MRA) imaging. Methods: MRA images and BP measurements were obtained from patients (n=15, M=8, F=7, Age= 49.2 ± 7.3 years) over a span of 700 days. A novel segmentation algorithm was developed to identify brain vasculature from surrounding tissue. The data was processed to calculate the vascular probability distribution function (PDF); a measure of the vascular diameters in the brain. The initial (day 0) PDF and final (day 700) PDF were used to correlate the changes in cerebral vasculature and BP. Correlation was determined by a mixed effects linear model analysis. Results: The segmentation algorithm had a 99.9% specificity and 99.7% sensitivity in identifying and delineating cerebral vasculature. The PDFs had a statistically significant correlation to BP changes below the circle of Willis (p-value = 0.0007), but not significant (p-value = 0.53) above the circle of Willis, due to smaller blood vessels. Conclusion: Changes in cerebral vasculature and pressure can be non-invasively obtained through MRA image analysis, which may be a useful tool for clinicians to optimize medical management of HBP