In the last decades, imaging technology has been introduced that allow the physician to make physiologic distinctions among normal, ischemic, and infarcted brain tissue. This approach to stroke will likely guide the next generation of treatments and has already had a pronounced impact on the direction of research in the field. Salvageable brain tissue in the acute phase of stroke can be delineated by these methods. To identify such ischemic but not yet infarcted tissue is a major goal of modern acute stroke medicine.
The introduction of effective treatments for acute stroke has led to greater dependence on sophisticated imaging techniques, but the authors believe it remains essential for the neurologist to understand the details of the cerebral vascular anatomy and the corresponding stroke syndromes for several reasons. Imaging techniques, though increasingly accurate, are not perfect. In cases in which the imaging does not reveal a stroke, the clinician remains dependent on careful history and neurologic examination. Furthermore, in many parts of the world, imaging techniques are unavailable at the pace necessary to initiate acute treatment. Finally, understanding the detailed anatomy helps the neurologist understand how the nervous system functions, lessons which are applicable to many other categories of illness other than stroke.
Despite these valuable imaging and therapeutic advances in stroke neurology, three points should be made. First, all physicians have a role to play in the prevention of stroke by encouraging the reduction of risk factors, such as hypertension, smoking, and hyperlipidemia and the identification of signs of potential impending stroke, such as transient ischemic attacks, atrial fibrillation, and carotid artery stenosis. Second, careful clinical evaluation integrated with the newer testing methods still provides the most powerful approach to this category of disease. Finally, there has been a departure from the methodical clinicopathologic studies in individual patients that have been the foundation of our understanding of cerebrovascular disease. Increasingly, randomized trials involving several hundred and even thousands of patients and conducted simultaneously in dozens of institutions have come to dominate investigative activity in this field. These multicenter trials have yielded highly valuable information about the treatment of a variety of cerebrovascular disorders, both symptomatic and asymptomatic. However, this approach suffers from a number of inherent limitations, the most important of which is that the homogenized data derived from an aggregate of patients is difficult to apply to a specific case at hand or the data is not available to resolve each patient’s particular problem. Most large studies show only modest or marginal differences between treated and control groups and correspondingly give guidance in large populations. These multicenter studies will be critically appraised at appropriate points in the ensuing discussion.
Differentiation of Stroke From Other Neurologic Illnesses
The diagnosis of a vascular lesion therefore rests essentially on recognition of the stroke syndrome; without evidence of this, the diagnosis must always be in doubt. The three criteria by which the stroke is identified should be reemphasized: (1) the temporal profile of the clinical syndrome, (2) evidence of focal brain disease, and (3) the clinical setting, by which we mean potential causes of embolic or other types of stroke, such as atrial fibrillation. Definition of the temporal profile requires a clear history of the premonitory phenomena, the mode of onset, and the evolution of the neurologic disturbance in relation to the patient’s medical status. Here, an inadequate history is the most frequent cause of diagnostic error. If these data are lacking, the stroke profile may still be determined by extending the period of observation for a few days or weeks in order to determine if the temporal pattern is more in keeping with a progressive disorder such as brain tumor, thus invoking the clinical rule that the physician’s best diagnostic tool is a second and third examination.