By Craig M. Walker, M.D.
Medical Director,
Cardiocascular Institute of the South

Strokes, the principal cause of paralysis in this country, come in two distinct types -- bland strokes, resulting from an interruption in blood supply to a part of the brain, and apoplectic or bleeding strokes, in which an artery inside the brain springs a leak.

Though they differ in cause, the effects of the two types of stroke are similar -- dizziness; numbness, weakness or paralysis on one side of the body; speech impairment, and blurred vision.

The blocked blood flow in a bland stroke is generally caused by a blood clot, frequently in one of the carotid arteries -- the major arteries on each side of the neck which carry blood to the brain. The cause of the leakage or rupture of an aneurysm (swollen weak point) in a bleeding stroke is often high blood pressure. High blood pressure is also a factor in bland strokes as well, since it damages arteries and precipitates clot formation.

Clots are also thrown off by the heart as a result of turbulence from certain heartbeat irregularities, heart muscle weakness and valve abnormalities. A bland stroke occurs when one of these clots becomes lodged in the brain's arterial system, and is most severe when the clot blocks one of the brain's four major arteries, or when a narrowed artery clots off at the site of the constriction.

Much of the initial impairment from a stroke results from increased pressure within the skull, either from seeping blood, which has no way to drain out of the brain cavity, or from the brain's tendency to swell when injured. The initial improvement in the condition of stroke victims stems from the reduction of this pressure, through medical treatment or surgery. Contrary to what many people think, it does not signify that the brain is healing itself. Brain tissue does not regenerate.

Strokes frequently occur without warning. If there is an early signal of an impending bleeding stroke, it is usually a bad headache which does not go away. Bland strokes, on the other hand, are sometimes preceded by mild, stroke-like symptoms which last less than 24 hours, but tend to recur. These events, called "transient ischemic attacks" (TIAs), are caused by blood clots that do not completely block an artery, and quickly dissolve or are swept away. TIAs and severe, persistent headaches should be taken very seriously -- like the initial rumblings of a volcano.

You would be well advised to have a carotid ultrasound test to detect developing blockages in your neck arteries if you have a family history of strokes, persistent high blood pressure, any pre-stroke symptoms, or if your doctor hears what is called a bruit when he applies a stethoscope to your neck. A bruit is a whistling sound in the carotid arteries from blood coursing through a narrowed channel.

Next week we'll look at how stroke-producing conditions are detected and how such conditions -- and strokes themselves -- are treated.

&copy 1995 Cardiocascular Institute of the South

For further information, call Jane Arnette, Cardiocascular Institute of the South/Houma, 1-800-425-2565, or Jim Keyser at 1-800-848-2715. E-mail questions or comments to: jakeyser@cardio.com.

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