Some kids seem to have near-constant ear infections. Even after the pain is gone, a parent's got to wonder: Are there lasting effects from all that muffling of sound in the formative years?
Research in rats just published in the journal Neuron suggests there might be effects in the brain that, while not permanent, can last for years. Apparently, hearing loss in one ear during critical periods of brain development can rewire the auditory cortex, changing the way it processes sound.
Neurobiologist Dan Polley, who recently moved to Harvard and the Massachusetts Eye and Ear Infirmary in Boston, conducted the research with a colleague, Maria Popescu, while at Vanderbilt University.
Polley says that while we don't need two ears to hear sound, figuring out where that twitter of birds or the shout from a friend is coming from requires the sort of depth perception that input from two ears provides. Plus, there are other benefits from a nuanced fusion of the two signals in the brain.
"Our ability to hear speech in a noisy background; to hear the wonderful compliments that your date is paying when you've taken her out to dinner; or when you have multiple people talking to you at once, and you try to home in on one speech source -- all these phenomena depend critically upon integrating signals from each ear," he says.
Polley wondered if the kind of periodic, months-long hearing loss experienced by some children with chronic infections and resulting blockage of the middle ear might actually affect the wiring of the brain. So he and his colleague tried a little test in rats of different ages: In each animal, they blocked the sound in one ear for a couple of months, and then unblocked that ear.
The result: In young rats, the ear that had remained open and clear made a sort of real estate grab in the auditory cortex, developing a much richer network of neural connections. The blocked ear lost influence. And even after both ears were once again sending clear signals to the brain, the imbalance in the brain persisted.
It's the sort of thing, Polley says, that could make triangulating the source of a sound harder, he says, and create subtle, but important deficits in hearing.
"When you don't correctly identify the position of a sound a in space, you may not know it," he says. When you're not able to hear in a noisy background, you may just not go out to dinner as often. You may end up isolating yourself from the environments that really require good hearing."
A child with that sort of problem might withdraw in a noisy classroom, Polley says, or--depending on when the imbalance occurs--might miss milestones in language or learning.Other studies have shown that's just the sort of thing that's been reported among some children with chronic middle ear infections.
Here's some comfort for parents: Though it can take a while, the brain is pretty good at developing workarounds, Polley says. Restore hearing, and the brain will eventually catch up.
Atresia Repair / Medpor now combined into ONE surgical procedure
Late January, 2008, Dr. Reinisch, Dr. Lewin, and Dr. Roberson (assisted by Drs. Colen) combined to perform the world's first procedure where atresia repair and medpor auricular reconstruction were combined into a single surgical procedure. The early results from this combined procedure, which took approximately seven hours to complete, appear to be as good if not better than performing it in the traditional two, or occasionally three procedures.
This combined procedure was performed on a 3 year old boy with bilateral microtia and atresia, adopted from China by a family living in Sacramento, California. Since that first case, all 18 subsequent cases have been successfully completed.
The advantages of the combined procedure are:
Fewer separate surgical procedures under general anasthesia
For families not living in the area, fewer trips to California (each
requiring an eight to ten day stay)
No three to four month waiting period between surgeries
The use of a single skin graft (taken from the skull) for both
procedures, eliminating the need for
multiple skin grafts from the thigh or abdomen
Watch a movie on Combined Atresia Repair - Microtia Reconstruction Surgery
Drs. Reinisch and Roberson plan on offering this combined atresia repair and
medpor auricular reconstruction
procedure once per month at the Waverley Surgery Center in Palo Alto
California.
The human is a complex body organ that begins development
early in a mother’s pregnancy. Those who have
been pregnant know the ear works by the last third of
pregnancy and that babies respond to sounds in their
environment by startling, by kicking or by stopping
movement.
For the ear to form correctly, structures grow from the skull base
and must join with growth from the outside of the head which
progresses in toward the inner ear. The two processes meet at the
eardrum and middle ear bones. A part of the process involves formation
of the outer ear (called the pinna) as several small folds of
skin merge to give our ears their normal appearance. Download Complete Newsletter
Drs. Colen) combined to perform the world's first procedure where atresia repair and medpor auricular reconstruction were combined into a single surgical procedure. The early results from this combined procedure, which took approximately seven hours to complete, appear to be as good if not better than performing it in the traditional two, or occasionally three procedures.
