Brain Injury in Newborns
An Investigation of Brain Injury in Newborns
What is the problem and what is known about it so far?
The brain is described as having both "gray" and "white matter." Gray matter is a layer of cells called neurons which covers the entire outer surface of the brain. These neurons send out branches which connect with other parts of the brain allowing neurons to communicate with each other. Bundles of these branches form the white matter. It is known that newborns with damaged and shrunken white matter (also known as periventricular leukomalacia) have an increased chance of developing cerebral palsy (a condition which can lead to loss of muscle control in the legs and arms as well as mental retardation). It is not known what causes most cases of white matter damage in newborns.
Why did the researchers do this particular study?
The researchers wanted to learn if certain infections were likely to be found in newborns with white matter damage. The researchers also wanted to learn if white matter damage was caused by poor blood flow to the baby during birth.
Who was studied?
Babies born after less than 34 weeks in their mothers' womb are more likely to have white matter damage than are "full-term" babies (those born after 37 to 42 weeks). For this reason only babies born after 23 to 34 weeks in their mothers' womb were included in this study. All of the babies were born in the same hospital between 1994 and 2001. There were 150 newborns with white matter damage born within these seven years. These 150 cases were compared with 150 newborns without white matter damage.
How was the study done?
For the newborns included in this study an ultrasound of the head was done (using sound waves to make a picture) to determine if the white matter was severely damaged. To find out if a newborn had poor blood flow during birth the pH of the umbilical cord blood was tested (a low pH means the baby's blood is acidic from poor blood flow). To find out if a newborn was likely to be infected, the newborn's blood, spinal fluid and fluid from deep in the throat were sampled and tested to see if bacteria were growing in them.
What did the researchers find?
The researchers found that newborns with severe white matter damage did not have lower blood flow during birth (measured by umbilical cord blood pH) than newborns with normal white matter. The researchers also found that newborns with white matter damage were more likely to have bacteria growing in the fluid from deep in their throat than newborns without white matter damage. Bacterial growth in blood and spinal fluid was the same in both groups.
What were the limitations of the study?
Overall, this was an inconclusive study because the researchers could not tell if the bacteria in the throat fluid caused the white matter damage or their presence was just a coincidence. Other studies have already shown that low blood flow during birth is not responsible for most cases of white matter damage.
What are the implications of the study?
More research is needed to improve the understanding about the causes of, and prevention strategies for, white matter damage (periventricular leukomalacia) in newborns.
Summarized by Wells Chandler, College of Medicine, University of Vermont.
Summarized from "Neonatal Cerebral White Matter Injury in Preterm Infants is Associated with Culture Positive Infections and Only Rarely with Metabolic Acidosi". Graham, Ernest M. et al. American Journal of Obstetrics and Gynecology, October 2004, Volume 191, Number 4, Pages 1305-1310.
