Neurovascular Examination: The Rapid Evaluation of Stroke Patients Using Ultrasound Waveform Interpretation

206 Pages·2013·13.134 MB·English

by  Andrei V Alexandrov(eds.)

Neurovascular Examination

Neurovascular
Examination
The Rapid Evaluation of Stroke
Patients Using Ultrasound
Waveform Interpretation
Andrei V. Alexandrov ,
MD
Professor and Director
Comprehensive Stroke Center
University of Alabama at Birmingham
University of Alabama Hospital
Birmingham, AL
USA
FOREWORD BY D AVID S. LIEBESKIND
This edition fi rst published 2013; © 2013 by Andrei V. Alexandrov
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1 2013
Contents
Foreword, vii
Preface, ix
Acknowledgment, xi
Abbreviations, xiii
1 Understanding the Mechanisms and Dynamics of Cerebrovascular Events, 1
2 Time Is Brain and Brain Is Flow!, 27
3 The Power of Observation, 39
4 Applied Principles of Ultrasound Physics, 55
5 Applied Principles of Hemodynamics, 71
6 Real-Time Ultrasound Measures, 91
7 Emergent Examination, 113
8 Diagnostic Waveforms and Algorithms, 129
9 Differential Diagnosis, 151
10 Integration of Information and Case-Based Problem Solving, 177
Index, 197
v

Foreword
The practice of stroke medicine is more than a profes- lated diagnostic technique or elusive treatment for
sion that I share with Andrei, as we both indulge in stroke. In my work on collateral perfusion in acute
this passionate hobby that extends far beyond a typical stroke or chronic disorders of intracranial atheroscle-
job. Andrei authored this innovative book based on rosis and moyamoya, diffi cult questions arise about
his diverse background in the medical physics and hemodynamics where the answers cannot be found in
technical aspects of ultrasonography, neurovascular the literature or textbooks. At those times, I call upon
expertise, and perpetual education of trainees to Andrei to provide expertise and clarify the boundaries
develop new treatments for acute ischemic stroke. of known from unknown. Many other colleagues in
Fueled by similar interests in engineering, neuroimag- the fi eld have similarly suggested calling Andrei when
ing, and mentorship of young investigators, I have questions arise about blood fl ow in stroke. This book
pursued a collateral pathway to study the hemody- is indeed an explanation of hemodynamic assessment
namics of cerebrovascular disorders. These multidisci- with ultrasonography as best described only by Andrei.
plinary roots have driven us to the frontiers of our Unlike the traditional medicine textbook where
fi eld, where questions abound regarding the use of dogma is recapitulated from generation to the next,
imaging to improve treatment and the subsequent this book emphasizes process over boundless tomes
outcomes of our patients at risk of devastating stroke of medical facts. This unique book provides the per-
syndromes. We continually ask questions about the spective and an experienced approach for burgeon -
whys of stroke, seeking explanations for the complex ing stroke professionals to utilize ultrasound at the
pathophysiology of ischemia in the brain. We think bedside. Readers may then similarly engage in this
about blood fl ow without fear of mathematics or fascinating and rewarding process where imaging
the challenge of uncharted territory in the crevasse technology can be integrated with neurological exper-
between various fi elds. In fact, we both think about tise to improve stroke treatment outcomes. After
fl ow in the snow while enjoying a similar enthusi- reading the book more than two times, I can attest
asm for skiing every winter! On such occasions, we that it will easily become an essential companion
exchange text messages about specifi c hemodynamic guide to this rapidly evolving fi eld. The book covers a
advances intermixed with scenes of powder on the broad range of topics from the applied principles of
slopes. Off the slopes, we both capitalize on the wealth ultrasound physics and related hemodynamics to clin-
of imaging data provided by a diverse range of tech- ical applications, composed in an inviting style of
nology, from ultrasonography to multimodal CT/MRI writing that can be easily digested. The content should
and conventional angiography. Detailed analyses of be of interest to anyone exploring hemodynamics of
such vast imaging datasets in the light of clinical mani- the brain, as an introductory book or even as a
festations have been the focus of intense research refresher text for experienced researchers. The per-
efforts by our collaborative groups to understand col- sonal nature of each chapter and close integration
lateral circulation and reperfusion. Our shared research with germane clinical issues refl ects a progressive
interests have centered on the pathophysiology and approach to stroke. Andrei notes that management of
clinical relevance of serial imaging for hemodynamics the stroke patient and treatment decisions do not end
in the brain rather than the development of an iso- with delivery of the tPA bolus, as this is just an initial
vii
Foreword
step. Decision-making may be tailored to specifi c ing in parallel with clinical evaluation are emphasized,
aspects of a given case rather than blind adherence to casting stroke as a dynamic process incompletely cap-
standard protocols. Throughout the book, functional tured by static imaging studies such as the routine
signifi cance or hemodynamic effects of vascular lesions noncontrast CT examination inevitably described as
are emphasized, in sharp contrast to the overly “unremarkable”.
simplistic anatomical defi nitions for luminal stenosis If you believe blood fl ow plays an important role in
utilized to date. Neurovascular examination with determining stroke risk and subsequent outcomes,
ultrasonography is touted for the ability to discern then this book on ultrasound and hemodynamics in
key physiological details beyond limited anatomical clinical practice is undoubtedly useful. Andrei ’ s step-
characterization of other neuroimaging modalities. wise overview on the topic in logical sequence from
This education in plumbing for neuroscientists offers the requisite physics concepts to common hemody-
hemodynamic perspective on the role of collaterals, namic scenarios will be of value in routine stroke care.
microcirculation and even venous phenomena. These The only missing aspect is an audio clip of Andrei ’ s
entities and the physics of fl ow are described in con- whistling and other vocalizations of ultrasonography
ceptual format, allowing the reader to grasp essential fi ndings. The hemodynamic aspects of ischemic stroke
concepts rather than memorizing equations. This underscored in this book form the basis for next steps
straightforward explanation of the underlying physics in stroke therapy, extending even beyond my own
sets the stage for the ultimate how-to book on cere- obvious bias on collateral perfusion!
brovascular ultrasound while considering the limita-
tions of current technology. A palpable interest in David S. Liebeskind, MD
educating future strokologists about infl uential mech- Professor of Neurology
anisms and pathophysiology is evident throughout the Neurology Director, Stroke Imaging
book. For instance, a thoughtful discussion of intrac- Co-Director, UCLA Cerebral Blood Flow Laboratory
ranial stenosis and downstream blood fl ow is offered Program Director, Stroke and
in place of the usual fi xation solely on measures of Vascular Neurology Residency
vessel narrowing. Hemodynamics gleaned from real- Associate Neurology Director, UCLA Stroke Center
time neurovascular examination and serial monitor- Los Angeles, CA, USA
viii
Preface
The modern term stroke has a predecessor, a Greek organizational issues, and truly multifactorial mecha-
word “apoplexy,” or “striking away,” as if a person was nisms, stroke poses a great challenge not only to my
struck by the hand of God. Although some strokes are colleagues in Vascular Neurology, Neuro-Endovascu-
truly unexpected and unpredictable, the risk factors lar Specialties, Neuro-Critical Care and Emergency
for most are now largely known, often detectable and Medicine but to many other disciplines of science as
some modifi able, and they tell us: stroke is coming, it well as health-care providers, administrators, and
could be imminent, and one has to take care and politicians.
change what can be changed to prevent it. Historically, stroke was seen as a neurologists’
Stroke may still happen. This misfortune has been domain to “diagnose and adios” when a traditional
a stepchild of medicine as it caused no pain, was neurological examination was used to pinpoint the
thought to affect mostly the elderly, leaving a person location of a lesion while therapeutic options until
miserably disabled, and there was nothing that a recent times were nil, leaving physicians pessimistic.
clinician could do to reverse it. Reperfusion therapy Novel developments in stroke treatment modify our
changed that, though some nihilism and resistance classic approach to diagnostic evaluation of acute
still linger. For those knowing how much needs to be stroke victims. Often, there is no time to conduct a
done, there is a constant challenge to advance our full neurological examination in the emergency room.
ability to detect stroke, bring victims to treatment, Structured and focused scales are predictive of conse-
tailor rescue to the specifi c mechanism of injury, and, quences of cerebrovascular catastrophes but provide
most importantly, fi nd ways to preserve the brain little clues as to the mechanism of a specifi c event.
tissue and afford time for natural or induced mecha- Physicians taking care of stroke patients need to
nisms to heal, restore, and to protect the person ’ s understand hemodynamic phenomena and applied
ability to get through a stroke. physics of imaging. This book is a refl ection of many
What came next is our understanding that stroke years of emergent evaluations of stroke patients
is not a striking lightening rod, leaving irreversible whereby my to-the-point neurological examination
damage. It is rather a process that takes time. Some and treatment decision-making were complemented
complete the damage in minutes, some in hours, some by bedside assessment of cerebral vasculature and
linger for days at the edge of potential reversibility. For hemodynamics in real time with ultrasound. The
how long, why, and how to afford time to bring them sequence of chapters refl ect the areas that physicians,
back will be the challenge for generations of strokolo- sonographers, and trainees need to study in order to
gists to come. build knowledge and skills for practicing, interpreting,
There is never an end to an exploration in science, and integrating cerebrovascular ultrasound for stroke
and the time to challenge established dogmas is always patient assessment and treatment.
now. New questions and discoveries lead to new I have to explain how I got there myself. In the past,
thinking. Thinking outside the box generates unortho- most neurologists were reluctant to take on stroke
dox ideas. These ideas lead to innovation, disruption, since it bordered so much on the internal medicine
and ultimately improvement in medicine. Stroke is and more recently on critical care and surgery – all
one area that deserves this now. With so many social, areas that many neurologists shied away from for a
ix
Preface
variety of reasons. I myself was no exception. I was Kuzmitch Lunev, whom I worshiped during my resi-
graduating from a neurology residency with no inter- dency training (yet I was reluctant to consider stroke
est in caring for a disease for which nothing radical as my future subspecialty). It was an order, I had to
could be done at that time (a disclosure here, it was obey it. Reluctantly, I did.
prior to the NINDS rt-PA Stroke Study). Like cancer, My subsequent journey introduced me to amazing
like incurable diseases before actual discoveries that teachers and thinkers including John W. Norris,
changed the dogmas and stigmas around these condi- Sandra E. Black, Patrick M. Pullicino, and ultimately
tions, I was under the impression that what I can do to James C. Grotta, all of whom contributed to my
as a physician will be better practiced elsewhere. I mentoring and leading me to learning real-time
have to give credit to the director of our academic pathophysiology of stroke through the prism of ultra-
institute back in the Soviet-era Moscow, late Professor sound, which I share with you in this book.
Nicolai Victorovich Vereshchagin, who told me that I
had to do a stroke fellowship under Professor Dmitri Andrei V. Alexandrov
x