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Brain Abnormality Linked to Sudden Infant Death Syndrome

2014/12/1      view:

An abnormality in the hippocampus has been discovered in babies who have died from sudden infant death syndrome (SIDS). The researchers suggest this could help with understanding why this condition occurs, and ultimately may lead to an intervention to lower risk.

The research team, led by Hannah C. Kinney, MD, professor of pathology, Harvard Medical School, Boston, Massachusetts, report their discovery in an article published online November 25 in Acta Neuropathologica.

SIDS, which is also known as cot or crib death, is characterized by the sudden and unexpected death of an infant, normally at night during sleep, with no other explanation found for the death. In the United States, SIDS is the third leading cause of death in infants, and it is the leading cause of death in postneonatal infants (those aged between 1 month and 1 year).

Coauthor of the current paper, Richard Goldstein, MD, a pediatrician at Boston Children's Hospital, explained toMedscape Medical News that multiple factors are thought to play a role in SIDS.

"It is thought that a convergence of external threats occur at a critical developmental stage in the child, but it is also believed that there could be an intrinsic developmental abnormality in these babies, and this is what we think we have discovered," Dr Goldstein said.

He added: "We see this as a very important discovery. It is a culmination of decades of work by Dr Kinney in trying to understand the vulnerability of infants who die suddenly with no apparent explanation."

He noted that Dr Kinney's previous work has suggested that the brainstem is involved in SIDS, and this has led to a focus on the hippocampus, the regulatory center in the brain for breathing, heart rate, and temperature. There is also evidence that serotonin may be involved in SIDS, with these babies found to have low levels of both this neurotransmitter and various serotonin receptors in their brains.

Focal Granule Cell Bilamination

In the current study, Dr Kinney and colleagues examined the hippocampus from postmortem samples taken from 153 infants autopsied at the San Diego, California, medical examiner's office. The infants had died suddenly and unexpectedly between 1991 and 2012. The deaths were classified as either unexplained (which included SIDS and other cases in which the cause of death was unknown) or explained (with death due to known causes).

In the SIDS cases, the researchers found that the dentate gyrus area of the hippocampus contained a double layer of nerve cells at certain intervals along its length, instead of the usual single layer. This abnormality is known as focal granule cell bilamination.

The researchers found the abnormality in the dentate gyrus in 41.2% (47/114) of the unexplained group compared with 7.7% (3/39) of the explained (control) group (P < .001). It was associated with a cluster of other dentate developmental abnormalities that reflect defective neuronal proliferation, migration, and/or survival, the researchers report.

"The pattern of abnormal changes in the dentate gyrus suggests to us there was a problem in its development at some point in late fetal life or in the months right after birth," Dr Kinney said in a statement from the National Institutes of Health. "We didn't see any signs of injury to the brain by low oxygen levels in the tissue we examined, such as scarring and loss of nerve cells."