Neurovascular Examination E-Book

Andrei V. Alexandrov

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 364

Veröffentlichungsjahr: 2013

Beschreibung

The use of neurovascular ultrasound is of increasing importance in neurological practice, both for radiologists and increasingly by neurologists themselves. Written by the world’s most renowned expert, this book explains

• 
  
• ultrasound examination of a stroke patient
  
• scanning protocols
  
• interpretation of the results

Case examples (with a standard template presentation correlating presentation to waveform output) reinforce the book's practical nature.

Illustrated with photos of the tests, explanations, and with actual waveforms, images, and result interpretation, and enhanced with 'pearls' and 'avoiding pitfalls' features, it is a practical reference for those learning ultrasound as well as those using ultrasound in their practices.

Leseprobe

Table of Contents

Title page

Copyright page

Foreword

Preface

Acknowledgment

Abbreviations

1: Understanding the Mechanisms and Dynamics of Cerebrovascular Events

Appendix 1.1 The National Institutes of Health Stroke Scale (NIHSS) score

2: Time Is Brain and Brain Is Flow!

3: The Power of Observation

4: Applied Principles of Ultrasound Physics

Introduction

Basic concepts

Bioeffects

5: Applied Principles of Hemodynamics

6: Real-Time Ultrasound Measures

Carotid and vertebral duplex

Intracranial ultrasound

7: Emergent Examination

Approaching the patient and neurological considerations

Extracranial vessel examination

Intracranial vessel examination

Emergent neurovascular assessment

8: Diagnostic Waveforms and Algorithms

Waveforms in vessels with normal patency

Waveforms indicating abnormalities in the vasculature

9: Differential Diagnosis

Introduction

Carotid artery stenosis

Carotid artery occlusion

Vertebral artery hypoplasia, stenosis, dissection, and occlusion

Systemic and cardiac abnormalities that could affect differential diagnosis

Downstream effects of carotid lesions

Intracranial stenoses versus collaterals

Intracranial occlusion localization

Vasospasm

Hyperemia

Steal

10: Integration of Information and Case-Based Problem Solving

Conclusion

Index

This edition first published 2013; © 2013 by Andrei V. Alexandrov

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Cover design by Grounded Design

Foreword

The practice of stroke medicine is more than a profession that I share with Andrei, as we both indulge in this passionate hobby that extends far beyond a typical job. Andrei authored this innovative book based on his diverse background in the medical physics and technical aspects of ultrasonography, neurovascular expertise, and perpetual education of trainees to develop new treatments for acute ischemic stroke. Fueled by similar interests in engineering, neuroimaging, and mentorship of young investigators, I have pursued a collateral pathway to study the hemodynamics of cerebrovascular disorders. These multidisciplinary roots have driven us to the frontiers of our field, where questions abound regarding the use of imaging to improve treatment and the subsequent outcomes of our patients at risk of devastating stroke syndromes. We continually ask questions about the whys of stroke, seeking explanations for the complex pathophysiology of ischemia in the brain. We think about blood flow without fear of mathematics or the challenge of uncharted territory in the crevasse between various fields. In fact, we both think about flow in the snow while enjoying a similar enthusi­­asm for skiing every winter! On such occasions, we exchange text messages about specific hemodynamic advances intermixed with scenes of powder on the slopes. Off the slopes, we both capitalize on the wealth of imaging data provided by a diverse range of technology, from ultrasonography to multimodal CT/MRI and conventional angiography. Detailed analyses of such vast imaging datasets in the light of clinical manifestations have been the focus of intense research efforts by our collaborative groups to understand collateral circulation and reperfusion. Our shared research interests have centered on the pathophysiology and clinical relevance of serial imaging for hemodynamics in the brain rather than the development of an isolated diagnostic technique or elusive treatment for stroke. In my work on collateral perfusion in acute stroke or chronic disorders of intracranial atherosclerosis and moyamoya, difficult questions arise about hemodynamics where the answers cannot be found in the literature or textbooks. At those times, I call upon Andrei to provide expertise and clarify the boundaries of known from unknown. Many other colleagues in the field have similarly suggested calling Andrei when questions arise about blood flow in stroke. This book is indeed an explanation of hemodynamic assessment with ultrasonography as best described only by Andrei.

Unlike the traditional medicine textbook where dogma is recapitulated from generation to the next, this book emphasizes process over boundless tomes of medical facts. This unique book provides the perspective and an experienced approach for burgeon­­ing stroke professionals to utilize ultrasound at the bedside. Readers may then similarly engage in this fascinating and rewarding process where imaging technology can be integrated with neurological expertise to improve stroke treatment outcomes. After reading the book more than two times, I can attest that it will easily become an essential companion guide to this rapidly evolving field. The book covers a broad range of topics from the applied principles of ultrasound physics and related hemodynamics to clinical applications, composed in an inviting style of writing that can be easily digested. The content should be of interest to anyone exploring hemodynamics of the brain, as an introductory book or even as a refresher text for experienced researchers. The personal nature of each chapter and close integration with germane clinical issues reflects a progressive approach to stroke. Andrei notes that management of the stroke patient and treatment decisions do not end with delivery of the tPA bolus, as this is just an initial step. Decision-making may be tailored to specific aspects of a given case rather than blind adherence to standard protocols. Throughout the book, functional significance or hemodynamic effects of vascular lesions are emphasized, in sharp contrast to the overly simplistic anatomical definitions for luminal stenosis utilized to date. Neurovascular examination with ultrasonography is touted for the ability to discern key physiological details beyond limited anatomical characterization of other neuroimaging modalities. This education in plumbing for neuroscientists offers hemodynamic perspective on the role of collaterals, microcirculation and even venous phenomena. These entities and the physics of flow are described in conceptual format, allowing the reader to grasp essential concepts rather than memorizing equations. This straightforward explanation of the underlying physics sets the stage for the ultimate how-to book on cerebrovascular ultrasound while considering the limitations of current technology. A palpable interest in educating future strokologists about influential mechanisms and pathophysiology is evident throughout the book. For instance, a thoughtful discussion of intracranial stenosis and downstream blood flow is offered in place of the usual fixation solely on measures of vessel narrowing. Hemodynamics gleaned from real-time neurovascular examination and serial monitoring in parallel with clinical evaluation are emphasized, casting stroke as a dynamic process incompletely captured by static imaging studies such as the routine noncontrast CT examination inevitably described as “unremarkable”.

If you believe blood flow plays an important role in determining stroke risk and subsequent outcomes, then this book on ultrasound and hemodynamics in clinical practice is undoubtedly useful. Andrei's stepwise overview on the topic in logical sequence from the requisite physics concepts to common hemodynamic scenarios will be of value in routine stroke care. The only missing aspect is an audio clip of Andrei's whistling and other vocalizations of ultrasonography findings. The hemodynamic aspects of ischemic stroke underscored in this book form the basis for next steps in stroke therapy, extending even beyond my own obvious bias on collateral perfusion!

David S. Liebeskind, MD

Professor of Neurology

Neurology Director, Stroke Imaging

Co-Director, UCLA Cerebral Blood Flow Laboratory

Program Director, Stroke and Vascular Neurology Residency

Associate Neurology Director, UCLA Stroke Center

Los Angeles, CA, USA

Preface

The modern term stroke has a predecessor, a Greek word “apoplexy,” or “striking away,” as if a person was struck by the hand of God. Although some strokes are truly unexpected and unpredictable, the risk factors for most are now largely known, often detectable and some modifiable, and they tell us: stroke is coming, it could be imminent, and one has to take care and change what can be changed to prevent it.

Stroke may still happen. This misfortune has been a stepchild of medicine as it caused no pain, was thought to affect mostly the elderly, leaving a person miserably disabled, and there was nothing that a clinician could do to reverse it. Reperfusion therapy changed that, though some nihilism and resistance still linger. For those knowing how much needs to be done, there is a constant challenge to advance our ability to detect stroke, bring victims to treatment, tailor rescue to the specific mechanism of injury, and, most importantly, find ways to preserve the brain tissue and afford time for natural or induced mechanisms to heal, restore, and to protect the person's ability to get through a stroke.

What came next is our understanding that stroke is not a striking lightening rod, leaving irreversible damage. It is rather a process that takes time. Some complete the damage in minutes, some in hours, some linger for days at the edge of potential reversibility. For how long, why, and how to afford time to bring them back will be the challenge for generations of strokologists to come.

There is never an end to an exploration in science, and the time to challenge established dogmas is always now. New questions and discoveries lead to new thinking. Thinking outside the box generates unorthodox ideas. These ideas lead to innovation, disruption, and ultimately improvement in medicine. Stroke is one area that deserves this now. With so many social, organizational issues, and truly multifactorial mechanisms, stroke poses a great challenge not only to my colleagues in Vascular Neurology, Neuro-Endovascular Specialties, Neuro-Critical Care and Emergency Medicine but to many other disciplines of science as well as health-care providers, administrators, and politicians.