Pittsburgh, June 11, 1999 -- Researchers in the department of neurological surgery at the University of Pittsburgh Medical Center are beginning two studies of people with partially and completely blocked blood vessels in the neck to determine the best methods to predict availability of brain blood flow.

Impaired blood flow to the brain may be a contributing factor to strokes. People with a completely blocked or a partially blocked neck artery may have brief attacks causing temporary blindness, numbness or weakness. These are individuals believed to be most at risk for a future stroke.

"Although the role of blood clots in causing strokes is well-known, the role of impaired blood flow is less clearly defined in part because of difficulties in measuring cerebral blood flow and other physiologic variables," said Howard Yonas, MD, chief of cerebrovascular surgery.

In the study, three methods for determining blood supply will be compared: transcranial doppler ultrasonography (TCD) which measures the speed of blood flow in large arteries, near infrared spectroscopy (NIRS) which measures the amount of oxygen consumption in the veins of the brain, and xenon with computed tomography (Xe/CT) which measures the amount of blood flow in the brain. The researchers hope to determine the least invasive test to identify patients who are having symptoms due to compromised blood flow. About 125 patients will be enrolled in the study over the next five years.

"In patients who do not have surgical intervention, the study also will be used to assess the value of cerebrovascular reserves measured by Xe/CT in predicting the risk of stroke," said Ronda Pindzola, Ph.D., research assistant professor in the department of neurological surgery and principal investigator in the study.

Patients with a completely blocked carotid artery who are symptomatic will also be eligible for a second study which will involve an additional test of blood flow called positron emission tomography (PET).

"This test is the Rolls-Royce of physiological studies and will allow us to determine several additional physiological variables," Dr. Pindzola said. "We want to determine if Xe/CT is as useful as PET for measuring blood flow reserves and predicting risk for stroke."

The first study is sponsored by the National Heart, Lung and Blood Institute of the National Institutes of Health. The second study is sponsored by The Pittsburgh Foundation.

Those interested in participating in these research studies should contact Dr. Pindzola at (412) 383-8677.