Five thousand children are born profoundly deaf each year in the United States alone. Another 10 to 15 percent of newborns have a partial hearing loss. Early identification and intervention of hearing loss is essential for successful treatment and rehabilitation. Critical speech and language development starts within the first three to four months of life. Once a hearing loss is identified, it should be determined if this loss is progressive or stable. Your child may require periodic audiograms to be sure that the hearing loss is going to remain stable.
A sensorineural hearing loss is used to describe hearing impairments which result from a disruption of the conversion of mechanical viabrations in the inner ear to nerve signals, which go up to the brain. These impairments may be congenital (i.e. present at birth), hereditary, developmental, or a combination of these. In addition, these impairments may result from infections, injuries, ototoxic drug therapy, or lack of oxygen.
Congenital Hearing Loss
Congenital hearing loss can be caused by genetics or caused by problems that may occur during fetal development or during the immediate birth period. Several viral infections, including CMV and German measles, contracted by the mother during the first three months of pregnancy may interfere with inner ear development in the fetus. Occasionally the origin is other viruses, such as the viruses of measles and mumps. Fortunately, because of better immunization prevalence, these diseases are not as common as they once were. A difficult and complicated labor or premature birth may also result in an inner ear hearing impairment on occasion. There are many syndromes which can also result in a hearing impairment at birth. Jaundice occurring at or shortly after birth is capable of damaging the inner ear. This is most often caused by Rh incompatibility between the mother’s and the child’s blood.
Genetics can also be the cause of hearing impairment. The development and function of the ear is dependent upon thousands of genes interacting with each other and with the inter- and extra-uterine environment. A major cause of late-onset hearing loss for children is genetic in origin. Most cases of hereditary-based childhood deafness are sensorineural rather than conductive in nature. Hereditary sensorineural hearing loss may be present at birth, or may develop later in life. This may be caused by inner ear malformations or other associated syndromes which have an associated inner ear hearing loss.
Acquired Hearing Loss
The most common type of acquired sensorineural loss is meningitis. Frequently this may affect both ears, but can involve one ear. Other types of infections would include viral diseases, such as mumps, rubella and otitis media.
Treatment and Rehabilitation
With the continual advancements in technology, even children with profound hearing losses will likely be able to hear sound to some degree. However, there is no known medical or surgical treatment that will totally restore normal hearing in patients with sesorineural hearing impairments. We therefore rely on rehabilitation through the use of a hearing aid, a cochlear implant and special training.
If your child’s hearing impairment is in the range of 35-70 dB HL, he or she should do well with a properly fitted hearing aid. He or she will probably be able to attend school with normal hearing children. He or she will need preschool speech therapy and auditory training in order that communication abilities will be at the optimal level when regular school starts.
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 adjuncts to assist with their communication skills, such as cued speech or other manual techniques.
The Cochlear Implant
The cochlear implant is an electronic device that is implanted into the inner ear of a severe to profoundly hearing impaired child. This device is only utilized if the child can benefit more from an implant than from a hearing aid. This device is used to bypass the diseased or nonfunctional hair cells and converts sounds to electrical impulses which directly stimulate the cochlear nerve. The implant consists of an external portion, comprised of a microphone, sound processor, and external coil, and an internal portion that must be surgically implanted. The surgical procedure involves the placement of an internal coil beneath the skin behind the ear and a stimulating electrode which is inserted into the cochlea or inner ear.
To determine suitability for this device in the severe to profoundly hearing impaired child, a careful examination is required. The evaluation is performed to determine whether the child can receive adequate information from a powerful hearing aid, or whether the implantation procedure can be performed and give the expected improvement.