Book Review

Brain Ischemia: Basic concepts and clinical relevance

N Engl J Med 1995; 333:71July 6, 1995

Article

Brain Ischemia: Basic concepts and clinical relevance
Edited by Louis R. Caplan. 380 pp., illustrated. New York, Springer-Verlag, 1995. $165. ISBN: 0-387-19850-4

“Everybody talks about the weather, but nobody does anything about it,” said Charles Warner, and this has been true of stroke -- until recently. As Dr. Caplan points out, however, in his preface to this interesting book, times have changed. With a newly acquired understanding of the processes involved and with new techniques for noninvasive monitoring, the role of the physician has shifted from merely providing supportive care to intervening in ways that can prevent irreversible damage. Cerebral ischemia reflects the interaction of pathologic and physiologic processes at many sites, and its consequences are equally complex. Effective intervention requires an understanding of these processes, and the aim of this book is to present an overview of this multifaceted problem. I think it succeeds remarkably well.

Brain Ischemia is a collection of 31 reviews by experts, each presenting an up-to-date description of the basic science underlying one aspect of stroke, with an emphasis on clinical relevance. The reviews are quite comprehensive but (in most cases) succinct, well referenced, well illustrated, and easy for nonexperts to understand. Unlike those in many collections of this type, these are bona fide reviews rather than seminars on the authors' research. The book is unusual in bringing together so many different -- but relevant -- features, including, for example, the important role of the endothelium in signaling systems, the hemodynamics of flow around plaques, the many controls of cerebrovascular tone, and the various cardiac dysfunctions caused by brain ischemia. Another unusual feature is the participation of the editor, who has written short introductions and summaries for the seven sections of the book. I think this is a great idea, but I do not think its potential has been fully realized.

There are, to my mind, several shortcomings. The space given to the many aspects of ischemia is not always well apportioned. Only one sixth of the book deals with the effects of ischemia on brain parenchyma, whereas some 30 pages are devoted to the physics of flow in arteries, and the cascade of reactions responsible for clotting and clot lysis is described by three contributors.

There are some surprising omissions. First, I found no mention of the effects of energy deprivation (the ``toxic'' changes in neurons that are discussed represent only a few of the myriad effects of too little energy). Second, there is virtually no mention of the role of temperature and its potential to enhance or diminish irreversible damage -- a factor over which the physician does have some control. Third, though the period before irreversible changes make treatment ineffective is briefly discussed, I believe it warrants more attention, because this period dictates the requirements for heroic efforts to initiate treatment early (probably by paramedics) and makes the negative effects of clinical interventions initiated after four hours largely irrelevant. Fourth, there is no discussion of the important differences between ``global'' and ``focal'' ischemia (misnomers, respectively, for a short period of complete cessation of flow, as in cardiac arrest, and for an extended period of inadequate flow through collateral vessels -- for example, after an embolism). The differences between the two insults have important clinical implications with respect to both the chemical changes that the neurons undergo and the nature of the hemodynamic limitations (e.g., the impaired autoregulation that makes it particularly difficult to reinstitute uniform blood flow after a complete arrest). Finally, though there are interesting discussions of the factors controlling the cerebral vasculature, they fail to address the question of what is responsible for the enlargement of the collateral circulation that occurs during chronic, progressive occlusion of a main artery and that may help to preserve brain tissue.

Notwithstanding these reservations, which reflect my particular interests, I found this book fascinating. I believe Dr. Caplan has performed a valuable service for both the clinician and the investigator by providing a broad and authoritative overview of the processes responsible for the many facets of ischemic brain disease.

Adelbert Ames, III, M.D.
Massachusetts General Hospital, Boston, MA 02114