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UAMS Device May Help Prevent Fetal Brain Damage
Embargoed for
Release: Sept. 5, 2002, 5:30 p.m. CDT
LITTLE ROCK -- For years, doctors who work in maternal and fetal medicine have had no way to detect brain activity in fetuses. Now, for the first time, researchers using a unique scanning device developed at the University of Arkansas for Medical Sciences (UAMS) can detect fetal brain activity in response to flashes of light transmitted through the mother's abdomen. With refinement, their technique may help physicians detect and prevent fetal brain damage resulting from maternal hypertension, diabetes, and other conditions.
The study at UAMS is one of the first tests of a new device designed to study maternal and fetal physiology, including fetal brain activity, using magnetoencephalography (MEG) of the womb. It also is the first MEG study to use light, rather than pulses of sound, to stimulate the fetus.
"This device allows us to examine the fetus in a new and noninvasive way," Curtis L. Lowery, a physician at UAMS and head of the project, explains. "We believe this device will be useful in the prediction and management of premature labor, fetal cardiac disease, and hypoxic ischemic disease of the fetus." Research scientist Hari
Eswaran of UAMS adds, "We are excited about |
Curtis Lowery, M.D., and Hari Eswaran, Ph.D., posed Sept. 4, 2002, with SARA, their device for scanning brain activity in fetuses. (Click on image for print-quality resolution.)
The top row of graphs show a fetus's brain responses to a series of light pulses at 28 weeks, 30 weeks, and 36 weeks. The bottom row of images are different representations of the same brain activity. (Click on image for print-quality resolution.)
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these initial results. With further study, we can improve the success rate of this technique."
The UAMS device uses fetal magnetoencephalography (MEG) to detect minute magnetic field fluctuations in the fetus. During the examination, the pregnant woman sits against a concave shield that covers her abdomen. More than 100 sensors obtain three-dimensional data from the fetus and the uterus - without employing needles or any other invasive instruments. It is the first instrument for simultaneous recording of multiple physiologic signals from a woman's uterus. MEG technology has been in use for 30 years for adult brain scans, but UAMS is the first medical center to adapt the technology for fetuses.
The work was supported by the National Institute of Neurological Disorders and Stroke (NINDS). Eswaran and Lowery and other colleagues describe the project in the September 7, 2002, issue of the British medical journal, The Lancet. "Though this work is preliminary, it is a promising indication of how MEG may help researchers understand the fetal brain," according to Giovanna Spinella, a pediatric neurologist at NINDS.
SARA stands for SQUID Array for Reproductive Assessment. SQUID is an acronym for Superconducting Quantum Interference Device, a method developed to detect tiny fluctuations in magnetic fields using a superconductor cooled by liquid helium.
Previous studies have shown that maternal hypertension, diabetes, pregnancy with two or more babies at once, and many other conditions can lead to a lack of oxygen that can damage the fetal brain. Prenatal infections, smoking, and other problems also can interfere with normal brain development. Structural problems in the fetal brain often can be detected using magnetic resonance imaging (MRI). However, until recently it has been impossible to directly assess brain activity in a fetus. Researchers have now begun to experiment with MEG and another type of brain scan, called functional MRI, in order to overcome this problem. Both techniques work by measuring tiny magnetic field changes that result from brain activity.
"To develop therapies, you need to be confident in intrauterine diagnosis," Lowery says. Currently available tests, such as fetal heart-rate monitors, have a high false positive rate, meaning that they often indicate a problem when there really isn't one. Using SARA could help to determine if a fetus is really at risk, enabling doctors to better decide when treatments will be beneficial, Lowery says. Doctors might be able to prevent brain damage by delivering the fetus before term, by cooling the baby's head after delivery, or someday even by using neuroprotective drugs, he adds.
In the study, Lowery and his colleagues tested SARA with 10 fetuses that had a gestational age of 28 - 36 weeks and no known risk factors for brain damage. Fetuses whose eyes were more than 3 centimeters from the maternal skin or whose heads were facing down or away from the mother's abdomen were excluded from the study. The expectant mothers sat upright on the SARA machine and leaned forward into a concave array of 151 sensors that surrounded the abdomen. The researchers then used a fiber-optic cable to deliver light pulses to the outside of the mother's abdomen while they recorded MEG data. The light used was about 11 times less intense than sunlight on a bright day.
When they screened out signals from the maternal and fetal heart beats, the researchers found that four of the 10 fetuses had measurable brain responses to the light pulses. The time between the light pulses and each fetus's response decreased with increasing gestational age. It is unclear why six of the fetuses did not respond to the stimulus, Lowery says. They may have been asleep during the test, or the position of their heads may have prevented them from seeing the light. He believes researchers may get better results if they test the same fetus repeatedly.
Much more testing is needed to define what types of responses indicate normal and abnormal brain activity in fetuses at different gestational ages, Lowery says. Unborn babies with specific kinds of brain damage may have no response to certain types of stimuli, or a delayed response. The researchers now plan to test larger numbers of fetuses to determine what types of brain responses may indicate a problem. They also plan to test babies born with abnormalities to try to determine how their responses differ from those of other babies. A special "cradle" adapter allows the researchers to scan newborn babies using SARA.
While this study showed that visual stimulation can activate the fetal brain, other types of stimulation may also be used with SARA. These might include auditory stimulation (such as pulses of sound or exposure to a mother's voice), vibration, or magnetic stimulation. Using several different kinds of stimuli may yield more conclusive results than a single test, because different types of stimuli activate different parts of the brain, Lowery says. The researchers also are investigating whether SARA can detect baseline brain activity in the fetus when no special stimulus is present.
In addition to improving clinical care, SARA may be useful as a research tool to investigate brain development in the womb. Data from such tests might ultimately lead to new insights about the causes of cerebral palsy and other developmental disorders, and to ways of preventing those disorders. SARA could be used with a visual stimulus as early as the 24th week of pregnancy, when the eyes have matured and the cortex is fully connected to the lower brain regions, according to Lowery.
The UAMS researchers are now planning to develop and test better light stimulators, such as lasers, and to perform serial brain scans, in which they examine a fetus's responses over a period of time. Since SARA also can detect the fetal heartbeat, uterine activity, and other physiological factors that may influence a healthy pregnancy outcome, it ultimately could be used in a variety of clinical tests, the researchers say.
The NINDS is a component of the National Institutes of Health in Bethesda, Maryland, and is the nation's primary supporter of biomedical research on the brain and nervous system.
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For more information:
Leslie W. Taylor, 501-686-8998
Wireless phone: 501-951-7260
taylorlesliew@uams.edu
Elizabeth Shores
Phone: 501-686-8394
e-mail: shoreselizabethf@uams.edu
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09/04/02 |
