Approximately 3 in 1,000 babies are born with permanent hearing loss, making hearing loss the most common birth defect in America (Ross et al., 2008; White, 1997). Children with hearing loss who begin intervention earlier, including hearing aids and speech therapy, have significantly better developmental outcomes than other children with hearing loss who begin intervention later. More than 90% of children with permanent hearing loss are born to two hearing parents, and an even larger majority are born to one hearing parent and one parent with hearing loss (Mitchell & Karchmer, 2004; Harrison & Rousch, 1996).
Until the 1990s, children born with permanent hearing loss typically would not have been identified and diagnosed until 2 ½ to 3 years of age. Since the initiation of newborn hearing screening and early hearing detection and intervention programs, the average age of hearing loss identification has decreased to 2 to 3 months of age.
Hearing loss may be divided further due to the cause of the hearing loss:
- Congenital hearing loss- hearing loss present at birth.
- Genetic – a defect in the genes which results in an abnormal development of the ear.
- Non-genetic –hearing loss which is due to some problem which occurred during the fetal development or during birth.
Acquired hearing loss –hearing loss which occurs sometime after birth and is not transmitted to future children.
Several viral infections, including cytomegalovirus (CMV) and German measles contracted by the mother during the first three months of pregnancy may interfere with the development of the inner ear in the fetus. Occasionally, other viral diseases are the cause. The viruses of measles and mumps may cause a sensorineural, or permanent, hearing loss after birth, but this happens infrequently. Immunizations are now available for both of these diseases.
PROBLEMS AT BIRTH
On occasion, a very difficult and complicated labor or premature birth may also result in a permanent hearing impairment. This may be due to lack of oxygen to the delicate ear structures. There are many syndromes which can also result in a hearing impairment at birth. A child can have also a hearing loss at birth without any hereditary relationship.
Jaundice, or yellowing of the skin, occurring at or shortly after birth is capable of damaging the inner ear. This is most often due to Rh incompatibility between the mother’s and the child’s blood. Fortunately, this is not a common occurrence. Newborns with jaundice who receive blood transfusions for the condition are at an increased risk of permanent hearing loss and should be evaluated at by an audiologist before six months of age.
The development and function of the ear is dependent upon hundreds or even thousands of genes interacting with each other. A major cause of late-onset hearing loss is genetic. There are several patterns of inheritance. In autosomal dominant disorders, one parent has the trait, which he passes to 50 percent of his children. In autosomal recessive inheritance, the parents of the children are clinically normal, but carry the recessive gene and pass it on to 25 percent of their children. X-linked inheritance traits are transmitted from a mother who carries the gene to 50 percent of her sons.
Most cases of hereditary childhood hearing loss are sensorineural, or permanent, rather than conductive (sometimes temporary) in nature. Hereditary sensorineural hearing loss may be present at birth or may develop later in life. This may be due to inner ear malformations or to other associated syndromes which have an associated inner ear hearing loss. One may see a genetic sensorineural hearing loss with or without associated abnormalities.
Children are more susceptible to middle ear infections than adults. Middle ear infections and fluid behind the eardrum can cause hearing loss in children if left untreated. The buildup of thick fluid does not allow the eardrum to pass sound to the hearing nerve as easily and can makes sounds seem muffled. Once the infection is treated and the fluid drains, hearing often returns to normal. Untreated infections that result in temporary hearing loss can cause speech delays over time, especially when children are infants and toddlers. Some temporary hearing impairments can become permanent if they are not treated and damage is caused to the eardrum and small bones in the ear. This kind of conductive hearing loss can require long-term use of hearing aids. Only an ear, nose, and throat physician can determine if surgical options could restore hearing.
The most common type of acquired sensorineural loss is due to meningitis. This typically affects both ears, but occasionally only one ear is affected. Other types of infections would include viral diseases, such as mumps, rubella, cytomegalovirus (CMV) and middle ear infections.
There is no known medical or surgical treatment that will restore hearing back to normal in children with sensorineural hearing loss. Therefore, we rely on rehabilitation through the use of a hearing aid or cochlear implant and specialized listening therapy, or aural rehabilitation.
Amplification in children with hearing loss is imperative so that the children can develop speech and language as close to their normal-hearing peers as possible. Infants identified with hearing loss should be fit with amplification before six months of age. Older children should be fit as soon after the hearing loss is identified and once they have been evaluated by an ear, nose, and throat physician (ENT). At times it may be necessary to obtain special x-rays of the inner ear, a balance test or other laboratory and blood tests. The audiologist will determine what amplification is best for the child and may work closely with a speech-language pathologist and ENT for long-term treatment. If the cause of the hearing loss is unknown, it is difficult to know if the hearing loss will worsen over time or stay the same.
HEARING AID EVALUATION
Evaluation of a young child’s hearing may require several visits with the audiologist. It is important to determine an accurate measurement of both the type and the degree of hearing loss in order to select the proper hearing aid. An aid that is too powerful for a young child may cause further damage or be uncomfortable and cause the child to reject it. On the other hand, if the aid is not strong enough, a child may receive little or no benefit from it and therefore object to wearing it, causing further speech and language delays.
PROFOUND SENSORINEURAL HEARING IMPAIRMENT
Children with severe to profound sensorineural hearing loss who are not able to achieve speech and language benefit with a hearing aid may be candidates for a cochlear implant. The cochlear implant is an electronic device that is implanted into the inner ear. It bypasses the damaged hair cells in the cochlea and converts the sounds we hear to electrical impulses which directly stimulate the hearing nerve.
The implant consists of an external portion, called the sound processor. It contains a microphone and a magnetic coil that is used to transmit the electrical sounds to the implant under the skin. The surgical procedure involves the placement of the implant in the skull bone that houses the inner ear; the electrical portion of the implant is threaded carefully into the cochlea so that the electrodes will make contact with the hearing nerve.
The goal of a cochlear implant is to restore hearing so that the child may hear soft, medium and loud sounds and develop oral speech and language. Several factors contribute to determining if a child is a suitable candidate to receive a cochlear implant. Evaluations must be completed by experienced audiologists and ENTs specializing in cochlear implant surgery. The evaluations determine whether or not the child can receive adequate information from a powerful hearing aid, and whether or not the surgery can be performed and give the expected improvement. In some cases, a speech-language pathologist may be part of the evaluation process also. Some considerations of a good pediatric candidate include age, physical structure of the skull, structure of the cochlea and hearing nerve, caregiver support and motivation, and access to proper speech therapy and audiological services.
Children who are not candidates or do not proceed to a cochlear implant may benefit from manual forms of communication such as American Sign Language, Signed English or cued speech in addition to spoken language. For those children who are not able to achieve understanding for speech, special schools are available to train them in the manual form of communication. The type of school a child attends depends upon the child’s hearing level and communication skills.
Proper rehabilitation for children with hearing loss depends on the type and degree of the child’s hearing loss and also the family’s goals for speech and language development. A well-rounded program of rehabilitation for children with hearing loss may include speech reading, auditory training, speech therapy and instruction in the use of a hearing aid. One may also consider other professionals to assist with the child’s communication skills, such as cued speech or other manual techniques. All aspects of the program do not necessarily apply to each child with an impairment, but each individual may be helped through some of these methods.
For additional facts and information, visit:
The American Speech-Language-Hearing Association
Harrison, M., & Roush, J. (1996). Age of suspicion, identification, and intervention for infants and young children with hearing loss: A national study. Ear and Hearing, 17(1), 55–62.
Mitchell, R. E., & Karchmer, M. A. (2004). Chasing the mythical ten percent: Parental hearing status of deaf and hard of hearing students in the United States. Sign Language Studies, 4(2), 138–163.
Ross, D., Holstrum, W. J., Gaffney, M., Green, D., Oyler, R., & Gravel, J. (2008). Hearing screening and diagnostic evaluation of children with unilateral and mild bilateral hearing loss. Trends in Amplification, 12(1), 27.
White, K. R. (1997, October). The scientific basis for newborn hearing screening: Issues and evidence. Invited keynote address to the Early Hearing Detection and Intervention (EHDI) Workshop sponsored by the Centers for Disease Control and Prevention, Atlanta, GA. Retrieved on August 25, 2012, from http://www.infanthearing.org/summary/materials/cdc.pdf