Q: What should I/my family expect as a part of an evaluation in case of a stroke?

In the medical evaluation of a stroke patient, doctors seek to do several things: determine the nature of the stroke; assess the stroke's severity; discover the way in which the stroke occurred; and understand the patient's risk-factor profile. The aims of their efforts are: to limit the adverse effects to the stroke; to prevent complications; to plan for rehabilitation; and to craft a strategy for preventing future strokes.

The Nature of the Stroke
Stroke is the result of failure of circulation to the brain. It can be divided into two broad categories, ischemic and hemorrhagic. Most strokes, about 80% of them, are ischemic. Here, is the circulation fails because blood flow is blocked or reduced. Hemorrhagic strokes involve the bursting of a blood vessel, with blood leaking into (and damaging) the surrounding tissue. The clinical pictures presented by these two types stroke can be identical. It is necessary to obtain an image of the brain to determine which type of stroke one is dealing with. Computer assisted tomographic (CAT or CT) scans and magnetic resonance imaging (MRI) are the most useful types of imaging.

CT scans are readily available and rapidly accomplished. They are good at detecting hemorrhage, but they are not sensitive to the early changes of ischemic stroke. Since treatment options differ significantly between ischemic and hemorrhagic strokes, it is crucial to know which type is present. This would seem a critical shortcoming of CT scanning, but in practice it usually is not.

In most cases, the bedside diagnosis of a stroke syndrome is reliable. When a CT scan shows no evidence of hemorrhage, one may confidently infer that the stroke is ischemic in nature. In some cases, however, the bedside diagnosis may be in error. Patients may show findings that suggest stroke, but in reality represent something else. These cases are termed "stroke mimics." Alternatively, genuine strokes may initially appear to be a non-stroke problem. These cases are "stroke chameleons."

It is for mimics and chameleons that MRI is particularly useful. Unlike CT, MRI can show abnormality within the first few minutes of an ischemic stroke. With proper machine settings, MRI is also sensitive for early hemorrhage. A good argument can be made for MRI as the test-of choice for stroke, but in most cases that role is still played by CT because MRI is less readily available, takes longer, and requires a greater level of patient cooperation.

Assessing a Stroke's Severity
The clinical phenomena of stroke can be very diverse, and the magnitude of these phenomena can vary from negligible to extreme. There is no perfect rating scale for stroke severity. In recent years, however, a useful clinical scale has become widely accepted for ischemic stroke. This is the National Institutes of Health Stroke Scale. On this scale, a score of zero is normal. Scores of 1-4 imply a minor stroke in which the outcome is likely to be good in any event. Scores above 10 imply a major stroke in which the outcome is likely to be unfavorable, unless effective acute clotbusting treatment can be offered. Scores above 20 imply a very severe stroke, probably a life threatening one.

Similar scales are used to stratify hemorrhagic strokes. These scales allow doctors to make prognostic projections, and to decide what sort of acute treatment is warranted, what kind of complications may be anticipated, and what sort of rehabilitation may be needed.

The Ways in which Strokes Occur
As we have noted, strokes can be divided into two types, ischemic and hemorrhagic, but within each of these types there are multiple ways in which the end-result may happen. It is useful to recall an old term for stroke, "cerebro-vascular accident". The phase has largely been abandoned by the medical community, but it retains utility in the present context by way of analogy with another type of accident, the auto accident. How many ways are there of having an auto accident? To be sure, there are quite a few. Among these, some are common. They include faulty cars, bad roads, and intoxicated drivers.

Just so, there are many potential causes of stroke but some are more common than others. For ischemic strokes, common causes include arteries damaged by cholesterol deposits, arteries damaged by high blood pressure, and abnormalities of the heart. For hemorrhage strokes, the "usual suspects" include malformed blood vessels, weakened blood vessels that develop aneurysms (ballooned-out sections of the vessel wall), blood-thinning medications, and blood vessels damaged by high blood pressure.

The medical evaluation to determine the way in which a stroke has occurred includes images of the blood vessels, studies of the heart, and measurement of blood pressure, as well as its effect on the circulatory system. There are multiple options for accomplishing these assessments. In selected cases, additional investigations are needed to demonstrate that stroke was due to an uncommon mechanism. In these cases, the evaluation might even include highly invasive procedures such as brain biopsy.

Understanding a Patient's Risk-Factor Profile
Understanding the way in which a stroke has occurred in a given person is critical to designing an individualized strategy to prevent future strokes in that person, but is should not be assumed that the identified mechanism of one stroke is the only mechanism by which another stroke might occur.

All ischemic stroke patients should be screened for well known stroke risk factors. As implied above, high blood pressure and heart disease are prominent risk factors. Other common ones include an excess of cholesterol and fats in the blood, evidence of damaged arteries, diabetes, obesity, and lifestyle risks such as cigarette smoking and physical inactivity. For most of these risk factors, there is compelling evidence that interventions to mitigate the risk factor will result in a significant reduction of the incidence of subsequent strokes.

Various genetic factors are recognized as important predispositions to stroke. These can be identified by blood tests. One suspects that the list of important genetic risk factors will continue to expand as the workings of the human genome become more fully deciphered. Someday it will probably be possible to determine a person's predisposition to stroke, with a high degree of accuracy, by a simple panel of laboratory tests. I do not believe that day has yet arrived, but we are clearly making progress in that direction.