July 24, 2015

Inner Ear Disease Possible Cause for Sudden Infant Death Syndrome (SIDS)?

Image courtesy of Tuomas_Lehtinen
at FreeDigitalPhotos.net
A loyal blog reader alerted me to an interesting research suggesting that inner ear disease may be a causative factor of Sudden Infant Death Syndrome (SIDS). Apparently this association made the news in April 2015.

SIDS is when a baby without any obvious health issues inexplicably and suddenly dies while sleeping. This risk is mainly present within the first 12 months of life. Although all new parents are informed to institute "Safe to Sleep" environments which has cut down on the number of SIDS deaths... it still occurs in spite of these interventions.

But the main question is "why" does it even happen in the first place? Dr. Daniel Rubens, a pediatric anesthesiologist at Seattle Children's Hospital, hypothesized that SIDS may be due to an inner ear problem.
"If the part of the ear that controls balance is damaged, babies may be unable to reposition themselves when their breathing is compromised... A healthy human baby will gasp for air and instinctively move its head to breathe. [Research involving] mice with damaged ears stayed in the same position, breathing "bad air" and died." [link]
The inner ear injury is suspected to occur from injury during birth (prolonged contractions) or an inner ear viral infection (not the same as middle ear infections).

Assuming this hypothesis is correct... subtle abnormalities would than be expected on ear testing, such as the hearing screening all newborns in most states in the USA are required to undergo to monitor for congenital deafness.

And in one study, they indeed found that SIDS babies scored lower at 2000, 3000, and 4000 Hz in the right ear on TEOAE hearing testing compared with healthy infants. No significant abnormality was found in the left ear on these tests. Any well-equipped ENT office can perform this or similar type testing on infants.

Some may ask why there should be an association between SIDS and right side only hearing issues (as opposed to the left side or both sides)? It is hypothesized that transfused placental blood moving under pressure from labor contractions into a newborn's veins is likely to be preferentially directed to the veins in the right inner ear because of the nearly 90 degree angulation of the left innominate vein away from the line of pressurized blood passing through the superior vena cava thereby protecting the veins that go to the left inner ear.

Clearly, more research on larger numbers of newborns are needed to determine whether inner ear problems is just a marker, a cause, or coincidental finding as it relates to SIDS, but certainly food for additional thought and research!

'Provocative' theory links inner ear damage to SIDS deaths. Today.com 4/24/15

Newborn oto-acoustic emission hearing screening tests: preliminary evidence for a marker of susceptibility to SIDS. Early Hum Dev. 2008 Apr;84(4):225-9. Epub 2007 Jul 5.

Anatomo-pathologic study of the temporal bone in our 4 cases of sudden infant death. Ann Otolaryngol Chir Cervicofac. 1985;102(6):425-32.

Sudden infant death syndrome: an update and new perspectives of etiology. Handb Clin Neurol. 2013;112:867-74. doi: 10.1016/B978-0-444-52910-7.00008-8.

Inner ear insult ablates the arousal response to hypoxia and hypercarbia. Neuroscience. 2013 Dec 3;253:283-91. doi: 10.1016/j.neuroscience.2013.08.059. Epub 2013 Sep 8.
Fauquier blog
Fauquier ENT

Dr. Christopher Chang is a private practice otolaryngology, head & neck surgeon specializing in the treatment of problems related to the ear, nose, and throat. Located in Warrenton, VA about 45 minutes west of Washington DC, he also provides inhalant allergy testing/treatment, hearing tests, and dispenses hearing aids.

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