Over 40 percent of babies who died from Sudden Infant Death Syndrome (SIDS) had a distinctive brain abnormality affecting the hippocampus, which influences vital functions such as heartbeat and breathing.
The researchers believe this newly-discovered abnormality could destabilize the brain's control of breathing and heart patterns during sleep or during brief arousals from sleep, the National Institutes of Health reported.
In the U.S.SIDS is the leading cause of death in children between one month and one year of age, and is yet to be explained.
"The new finding adds to a growing body of evidence that brain abnormalities may underlie many cases of sudden infant death syndrome," said Marian Willinger, Ph.D, special assistant for SIDS at NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development, which funded the study. "The hope is that research efforts in this area eventually will provide the means to identify vulnerable infants so that we'll be able to reduce their risk for SIDS."
In SIDS cases researchers noticed some regions of a structure within the hippocampus, called the dentate gyrus, contained a doubled layer of nerve cells instead of the usual single layer.
To make their findings the researchers looked at sections of the hippocampus from 153 infants autopsied at the San Diego, medical examiner's office. The infants' deaths were classified as either unexplained (which includes SIDS), or explained by other causes. After examining the samples the researchers noticed abnormalities in the dentate gyrus in 41.2 percent of the unexplained group and in only 7.7 percent of the explained group. The team determined 86 of the undetermined cases were SIDS, and 43 percent of these samples were found to contain the abnormality.
The hippocampal abnormality is similar to what is seen in some cases of temporal lobe epilepsy, this is significant because in the past it has been suggested that SIDS is caused by unwitnessed seizures stop the heart or breathing patterns.
Until more research is conducted on the link between these brain abnormalities and SIDS the researchers recommend sticking to safe sleeping guidelines, such as placing infants on their back on a firm surface.
"The story of SIDS research is far from complete," said Dr. Hannah C. Kinney. "Until it is, the best ways to reduce the risk for SIDS is by following the recommendations for safe sleep and other infant care practices of the Safe to Sleep campaign."
The research was conducted in part by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).
