The inner ear may hold a clue in the quest to find the cause of SIDS

Infant ear

Daniel Rubens, MD, is not your average researcher. He’ll tell you for starters, that he’s not technically a researcher, but rather an anesthesiologist. His team is small:  Travis Allen, a nurse anesthetist at Seattle Children’s, volunteers his free time to work alongside Rubens, who is also supported by staff and leaders at Seattle Children’s Research Institute and the University of Washington.

Since 2007, Rubens has spent no more than $100,000 on his research on SIDS, or Sudden Infant Death Syndrome. A big chunk of those funds, $60,000, came from a fundraiser held in Florida by a mother who lost her child to SIDS. She read about Rubens’ research, contacted him out of the blue and wanted to support his efforts.

Rubens’ experience dealing with infants in crisis inspired him to seek an answer to the unsolved mystery of SIDS, and his latest study published in Neuroscience—offers up more clues on the premise that the syndrome may be related to dysfunction within the inner ear. “I was always drawn to the mystery of SIDS,” Rubens said. “I’ve read the literature over the years, and it struck me that there’s so much we don’t know,” he said, when asked what initially piqued his interest.

“Families are devastated by this phenomenon,” Rubens added. “Parents are never the same again, frequently second guess what happened and imagine what they could have done to prevent it.” Not smoking and laying the baby on its back are things that definitely can help, yet babies still die from SIDS when both of these recommendations are followed.

Recent changes to the terms used by coroners on death certificates have created additional headaches, according to Rubens. Deaths previously identified as SIDS may now be named death from suffocation, asphyxia, or other terms such as Sudden Unexplained Death. These terms make it nearly impossible to investigate SIDS and the terminology can throw a greater sense of blame on already devastated parents.

Shining a light on a dark topic

SIDS deaths are less common today than they were 40 years ago, when Children’s hosted the first international conference that shined a light on this dark topic. The conference and the leadership of Bruce Beckwith, MD — who began studying crib deaths in 1964 — helped illuminate SIDS and launched a greater understanding of how to reduce its occurrence.

It was Beckwith, former head of pediatric pathology at Children’s, who coined the term SIDS. Four decades later, much has been learned about the syndrome, yet the quest for its cause continues. At Children’s, where so much of the initial investigation of SIDS occurred, Rubens is following in Beckwith’s footsteps.

In a study published in 2008, Rubens found an association between SIDS and an abnormality in the ear. It was a potential breakthrough, but also an example of how medical research is a journey where opening one door leads to another, and where unrelated paths often cross in unexpected ways.

Intuition inspires a search to find answers

Rubens listened to his intuition when he decided to seek clues to SIDS in the inner ear. “I had the idea that we’ve missed something in medicine about the way the body controls breathing and that the missing piece might be in the specialized nerve tissue found in the inner ear,” he said.

When Rubens sought hearing-related data to pursue his theory, he turned to Susan Norton, PhD, who leads Clinical and Research Audiology at Children’s. Between 1993 and 2000, Norton led a national study to compare the effectiveness of various newborn hearing tests.

While leading that study, Norton worked closely with Betty Vohr, MD, of Women and Infants Hospital in Rhode Island, one of the first states in the U.S. to test the hearing of newborns. Norton’s relationship with Vohr paved the way for Rubens to gain access to 13 years of hearing test results.

The state’s testing program was able to provide a large enough sample of SIDS cases — 31 — to be statistically significant. Although the hearing loss was not severe, the 31 SIDS babies demonstrated a consistently lower score in the right ear across three sound frequencies when compared to babies who did not die from SIDS.

Subsequently, in a study published in Neuroscience in 2011, Rubens found that inner ear dysfunction in a previously-healthy individual can cause a breathing problem. “This may not in itself cause SIDS, but it led us to look further into the possibility that an inner ear problem might also be directly related to why SIDS babies die,” said Rubens.

His most recent study, published in Neuroscience in October 2013, found that individuals with inner ear dysfunction (even if limited to only one ear) are unable to arouse and move away from a suffocating environment. The scenario of arousal being impaired, even when faced with suffocation, has been proposed by many researchers to be the issue at the heart of why SIDS babies die.

The two recent studies were both conducted on mice, described by Rubens as portraying important similarities to SIDS cases. “You can’t tell the mice with inner ear dysfunction apart from their siblings,” Rubens said. “They do not have any apparent brain-related problems, they display normal eating patterns and they look completely normal in their waking behavior.”

Rubens continues to look at the potential link between the animal studies he’s conducted and what’s taking place with SIDS babies. “If the mechanism of death is related to inner ear dysfunction, we can start looking at potential solutions and that is the next step,” he said.

One theory Rubens has been mulling over is that babies who die from SIDS suffer some undetected trauma at birth that damages the specialized cells within the ear. This inner ear trauma would explain the change in newborn hearing and does not exclude that the trauma might impair other regions of the brain.

Research to continue using UK data

The next step for Rubens is to take his research even farther, distance-wise. He needs more specific hearing data for newborns in greater numbers and the place to find that is in England, through the British newborn hearing screening program. The aim is to investigate up to 120 SIDS cases, comparing them with 360 newborn infants that survived the first year of life. The unique researcher will also team up with London police, who have launched Project Indigo, a program that investigates conditions such as SIDS (known, in the broader sense, as Sudden Unexpected Death in Infancy in the U.K.).

What’s missing right now, though, is funding. Rubens said that he needs $150,000 to get the newborn hearing study off the ground in England. “There are families that are interested in supporting the work and I hope we can get a bare bones study off the ground within the year,” he said.

Co-authors on the “Inner ear insult ablates the arousal response to hypoxia and hypercarbia” study in Neuroscience include Travis Allen (Seattle Children’s Hospital), and A.J. Garcia III, J. Tang and Jan-Marino “Nino” Ramirez (Seattle Children’s Research Institute) .

Donate to Dr. Ruben’s research through Seattle Children’s.

If you’d like to interview Dr. Rubens, please contact Seattle Children’s PR team at 206-987-4500 or at [email protected].