Researchers from Brazil and Canada will report that a combination of two forms of ultrasound -- transcranial Doppler ultrasound and duplex carotid ultrasound -- can accurately measure the degree of blockage in the carotid arteries that serve the brain.
Assessing the extent of blockage is an important step in deciding whether an operation is needed to remove the blockage in those who are at risk of stroke, the leading cause of disability in the United States.
But cerebral angiography, the current method which uses dyes in the blood to assess blockage before deciding whether to operate, can itself provoke a stroke. This new method would reduce the need for cerebral angiography and the risk that goes with it.
Dr. Roberto Hirsch of Sao Paulo University Medical School in Brazil will report the findings on August 14 at International Neurosonology 97, an international medical conference in Winston-Salem, N.C. to review the latest use of ultrasound on the brain. The conference is being sponsored by the World Federation of Neurology and the Bowman Gray School of Medicine of Wake Forest University.
Stroke, sometimes called "brain attack," kills about 150,000 people in the United States each year and is the third leading cause of death in the United States after heart disease and cancer. When not fatal, stroke can leave brain functions impaired. About 500,000 people suffer strokes each year.
A major cause of stroke is arteriosclerosis, or hardening, of the carotid arteries that supply blood to the brain. As we age, a plaque of fat, calcium deposits and blood clotting material can form on the inner lining of the arteries, impeding the flow of blood to the brain. Stroke occurs when a piece of this plaque breaks off and lodges in a smaller blood vessel, shutting off the flow of blood to that part of the brain. Stroke also can happen when the carotid itself is completely blocked.
A person whose artery is 70 percent blocked or more has four times the risk of stroke as a person with lesser blockage. Severe blockages can be surgically removed.
Currently, doctors use cerebral angiography as the final step in assessing the blockage to determine whether surgery is needed. This method involves inserting a catheter in the leg and following the arteries up into the head. There, a dye is released into the blood that can be seen on x-rays.
But the catheter itself can rupture the plaque and send pieces into the brain, or trigger an arterial response that may form blood clots, leaving patients at risk of stroke not only during the procedure but for several hours afterward. And, said Hirsch, "the risk is exponential depending on their age and their history of stroke."
Hirsch and other studied 72 patients. On each they performed cerebral angiography, transcranial Doppler and duplex carotid ultrasound and found no statistical difference in the results. This shows, Hirsch said, that "if you are basing the indication for (surgery) solely on the measurement of (blockage), you can do it safely and non-invasively. The combination of the two (ultrasound) methods gives you enough information."
However, Hirsch noted, this new method will not find blockages lower in the carotid artery where it emerges from the main artery leading from the heart.
For further information, call Mark Wright (email: mwright@bgsm.edu) or Bob Conn (email: rconn@bgsm.edu) at 910-716-4587. Once International Neurosonology '97 has begun on August 13, call the conference press room at 910-724-6923.