Janury 22, 2007

Brain Defects and SIDS
By Thomas G. Dolan
For The Record
Vol. 19 No. 1 P. 30

Researchers from Children’s Hospital Boston have uncovered clues that the cruel killer may be a disease and not a tragic mistake.

Sudden infant death syndrome (SIDS), often referred to as a mystery disease, has been a source of anguish for parents whose newborns have perished due to unknown causes that often get lumped together as the source of SIDS. They have endured the tragedy of putting an apparently healthy baby to bed only to have him or her never wake.

Until recently, for this reason, there have been contradictory recommendations as to how to place an infant down to sleep. Parents can be haunted by their failure to put their infant in the right position. Also, there has been the connotation, however vague, that if the child went to bed healthy and then died, a parent must have committed murder.

Stephen Sheldon, DO, professor of pediatrics at Northwestern’s Feinberg School of Medicine and director of the Sleep Medicine Center at Chicago’s Children’s Memorial Hospital, explains that infant deaths due to unknown causes have been reported for 2,000 years.

As for how to position babies for bed, Marian Willinger, PhD, special assistant for SIDS, National Institute of Child Health and Human Development for the National Institutes of Health, says that until 1992, medical recommendations were that the baby should lie on his or her side or back. However, a side-sleeping infant could easily roll over onto the stomach and smother. As a result, in 1992, the American Academy of Pediatricians started a Back to Sleep campaign to promote placing infants on their backs at bedtime. According to government statistics, the incidence of SIDS has dropped 50% since 1992, suggesting that the campaign has been successful.

Now comes news of a potential breakthrough study that may one day eliminate the worry over how to send infants to bed. Researchers led by noted neuropathologist Hannah Kinney, MD, and neuroscientist David Paterson, PhD, at Children’s Hospital Boston and colleagues at Harvard Medical School analyzed new autopsy data to provide the strongest evidence yet that SIDS has a concrete biological cause. The study, published in the November 1 issue of The Journal of the American Medical Association, documents abnormalities in the brain stem, a part of the brain that regulates breathing, blood pressure, body heat, and arousal, in babies who died from SIDS.

The researchers examined brain autopsy specimens from 31 SIDS infants and 10 infants who died from other causes. Examining the lowest part of the brainstem, known as the medulla oblongata, they found abnormalities in nerve cells that make and use serotonin, one of more than 100 chemicals in the brain that transmit messages from one nerve cell to another. Specifically, the researchers discovered that brainstems from SIDS infants contained more neurons that manufacture and use serotonin than did the brainstems of control infants.

Based on their findings, Kinney, Paterson, and colleagues hope to develop a diagnostic test to identify infants at risk for SIDS. They also envision a drug or other type of treatment to protect infants who have abnormalities in their brainstem serotonin system.

According to Children’s Hospital Boston, the brainstem serotonin system is thought to help coordinate breathing, blood pressure, sensitivity to carbon dioxide, and temperature during waking and sleep. When babies sleep face down or have their faces covered by bedding, they are thought to rebreathe exhaled carbon dioxide, therefore breathing in less oxygen. Normally, the rise in carbon dioxide activates nerve cells in the brainstem, which in turn stimulate respiratory and arousal centers in the brain, so the baby doesn’t asphyxiate.

“A normal baby will wake up, turn over, and start breathing faster when carbon dioxide levels rise,” Kinney said in a news release.

But in babies who die from SIDS, defects in the serotonin system may impair these reflexes, the researchers noted.

“We provide strong evidence that SIDS is a biological problem, and that the brainstem serotonin system is a good place to focus continued research efforts,” Paterson said in a statement.

Despite the fact that the Back to Sleep campaign recommendations had been widely distributed by the time the study began, 65% of the SIDS cases in the study were sleeping prone or on their side at the time of death.

Nevertheless, the study prompted plenty of feedback from the medical community, including Sheldon and Willinger. On one hand, they view the results as a scientific advance.

“The Children’s Hospital Boston study is the result of many years of research,” says Willinger. “It is the most comprehensive view to date. It shows how the whole network of cells in the brain communicate with each other through serotonin and do so in an abnormal way with SIDS babies. The study shows how this area of the brain regulates breath, heart beat, temperature, and other factors while the baby is sleeping. It’s very clear-cut.”

However, despite the scientific breakthrough, there’s no guarantee that it will lead to a reduction in SIDS deaths.

“Right now, it’s all speculation,” Willinger says. “It has to be pursued at the research level. You start with the physiology, learn how the system works, then develop screening tests to identify babies who are at risk and then find specific ways of intervention.”

Sheldon says that “any discovery regarding SIDS is exciting, and this is a very valid discovery.” He adds, however, that it needs to be replicated in many other institutions for full scientific validity. “And once the biological cause can be diagnosed in a reasonable manner, then it’s necessary to develop screening tests to find which babies should be investigated further for confirmation,” says Sheldon. “Then the direction is to look for a cure, to be able to do something about it, or to counsel appropriately.”

Willinger estimates that such a screening test is roughly 10 years away.

Meanwhile, what works (at least to a significant degree) and which has been proven in several countries, is that putting babies “back” to sleep has led to a dramatic decrease in SIDS. Sheldon says that although adverse reactions, such as carbon dioxide intake, are plausible, they are still speculation.

Placing infants on their backs isn’t the complete answer, Willinger acknowledges. She reports that 2,000 babies still die of SIDS each year, 30% of whom are not put to bed on their backs. Of the 2,000, approximately three fourths are premature or otherwise abnormal babies, according to Willinger.

Should a screening procedure be developed and treatments created to protect infants during this time when they’re most vulnerable, it’s unlikely it would involve a drug.
‘’Drugs and baby’s brains don’t seem like a good mix,” Willinger says. She agrees that cigarette smoke and alcohol are “insults” to the fetus, although their role in serotonin deficiency is unknown. However, those vices are destructive for any number of reasons, and a known biological linkage is not necessary for mothers-to-be to use common sense during pregnancy.

To help ensure newborns are at optimal health, it’s also essential that mothers be aware of their diet.

‘’It’s very important we learn about optimal nutrition,” Willinger says. “We know that babies with a healthy mother have a better chance than those who don’t.” But, again, enough is already known about good nutrition, so it can be implemented without waiting for scientific discoveries as to what foods are linked positively or adversely to serotonin.

What might be called simple folk medicine, or common sense, is still the best and most practical prevention available for a time if the search for a cure leads to a pharmaceutical. Back to Sleep is probably still the best medicine, especially since the phrase helps parents remember the correct position.

But there are other practical measures Willinger and Sheldon point to which seem to help. One is the use of pacifiers in certain populations which, according to various studies, have reduced the incidence of SIDS, though no one is quite sure why.

Willinger also emphasizes that steps should be taken to ensure that infants don’t get tangled in quilts, blankets, comforters, and pillows. “You don’t want the room too hot,” she says. “The baby should be comfortable and cool to the touch.” She adds that if more warmth is needed, a blanket sleeper is the answer because the baby can’t get tangled in it.

Willinger also says that if the baby is brought to bed for nursing or coddling, it’s recommended that the infant be put in its own sleeping environment afterward.

There are no pat answers to preventing SIDS. But at the moment, common sense appears to be a step ahead of science, at least in terms of a solution. The pregnant mother shouldn’t smoke or drink and should eat healthy foods. Infants should sleep on their backs in a comfortable setting, alone and without unnecessary bedding or clothing. Having done this, parents can rest comfortably knowing they’ve followed all the recommendations available at this time.

— Thomas G. Dolan is a medical/business writer based in the Pacific Northwest.