August 10, 2012
Dear Mayo Clinic:
Our 2-month-old son was just diagnosed with total deafness. Initially there was a 50 percent hearing loss in one ear, but after two months we were told he cannot hear at all. What could cause hearing loss in an infant? Is there any hope, such as promising clinical trials, that he may someday hear?
Finding out a child is deaf can be very difficult for families, and deciding what to do can be tough. Although there is no way to restore natural hearing, promising treatment options may help a child to hear.
A variety of causes can lead to hearing loss in infants. Babies born prematurely are at a higher risk for hearing loss than other infants. Some infections during pregnancy may lead to hearing problems in babies. For unknown reasons, the structure of the ear may not develop normally early in pregnancy. Also, many genes are necessary for normal hearing, and many abnormalities can result in hearing loss. Although testing can identify some causes of hearing loss, determining why an individual child has hearing loss is not always possible.
Right now, there are few clinical trials designed to treat or cure newborn hearing loss. One trial that is currently ongoing uses stem cells in an effort to remedy hearing loss. But the results of that study are only preliminary, and the treatment is not readily available at this time.
The most successful form of treatment for infant deafness is a cochlear implant, an electronic device that bypasses the parts of the ear that do not work. The implant includes an electronic component that is surgically placed under the skin behind the ear with a wire that extends into the inner ear, or cochlea. A combination transmitter and speech processer worn behind the ear looks similar to a hearing aid.
Normally, hearing occurs when sound waves reach the structures inside the ear. There, the sound wave vibrations are converted into nerve signals and carried through the auditory nerve to the brain. The brain then recognizes those signals as sound. A cochlear implant works by changing sounds into electrical pulses that go directly to the auditory nerve, skipping the inner ear. The auditory nerve sends those signals to the brain, and the brain interprets them as sound, so hearing can happen even when the ear is damaged.
The signals a person's brain receives through a cochlear implant are not exactly like the sound of normal hearing. Training and practice are necessary to associate the signals with specific sounds. Children who receive an implant at a very young age are particularly good at this, and results have been impressive.
Cochlear implants can be placed in children as young as 6 months. Most children who have severe hearing loss can develop spoken language skills when using cochlear implants. Many children who get implants at very young ages are able to enter school with their hearing peers. As children age, the implants have been shown to be dependable, and most children with the implants need few, if any, support services due to hearing loss.
Results seem to be best for children who receive cochlear implants when they are infants or toddlers. Children who have severe hearing loss in both ears, as your son does, receive the most benefit from two implants, one for each ear.
We encourage you to discuss the possibility of cochlear implants with your son's doctor. An audiologist — a medical professional who specializes in hearing loss — along with an otolaryngologist — a surgeon who specializes in ear, nose and throat disorders — can work with your son's health care team to determine whether he is a good candidate for cochlear implants.
— Colin Driscoll, M.D., Otorhinolaryngology, and Douglas Sladen, Ph.D., Audiology, Mayo Clinic, Rochester, Minn.