Hearing Loss

Hearing loss, an impairment in the hearing sense, is classified by where in the ear the loss occurs. There are three types of hearing loss.

A conductive hearing loss occurs when there is interference with sound waves that travel through the outer and middle ear. This could be due, for example, to a perforated eardrum, wax in the ear or problems with the middle ear bones—the malleus, incus and stapes.

A sensorineural hearing loss occurs when there is interference in the innermost area of the ear or the auditory nerve that conducts hearing information to the auditory area of the brain. Damage to the inner ear structures, for example, due to exposure to loud noises or a tumor of the auditory nerve could cause hearing losses. This may occur in cochlea, the part of the inner ear that turns the sound vibrations into electrical signals, which are then transmitted by the auditory nerve to the brain where they are turned into recognizable sounds. In hearing loss due to excessive noise exposure, the force of the noise impulses on the inner ear mechanisms leads to cellular metabolic overload, cell damage and then cell death. One might think of noise induced hearing loss as excessive wear and tear on these sensitive structures.

• Mixed hearing loss where the teen has both conductive and sensorineural components to the hearing impairment.
  
• Hearing loss is further divided into four levels of severity. This is defined by the level of sound a teen may hear in decibels (dB) without a hearing aid.
  
• Mild hearing loss: a teen can hear sounds of 20 to 40 dB or louder. He or she may have trouble hearing distant or faint speech
  
• Moderate hearing loss: a teen can hear sounds louder than 45 to 60 dB. These adolescents will have difficulty hearing speech in group situations.
  
• Severe hearing loss: these teens can hear sounds 65 to 85 dB or higher. He or she can hear only loud voices one foot or less away or loud environmental sounds.
  
• Profound hearing loss: teens with this loss are usually termed deaf; they may hear loud sounds of 90 dB or more.

Who is likely to develop hearing loss?

Approximately one to two newborns per one thousand newborns have a moderate, severe or profound hearing loss, and one to two newborns per one thousand may have mild hearing loss. By age nineteen years the prevalence of hearing loss has doubled.

Conductive hearing loss may be congenital or acquired during childhood or adolescence. A newborn may have an absent ear canal or deformed ear and this could produce sound conduction problems. More commonly, middle ear infections, problems with the middle ear function or tumors in the middle ear can cause conductive hearing loss in older children and adolescents.

Sensorineural hearing loss may also be congenital or acquired. Children born with certain infections such as rubella or cytomegalovirus may have hearing loss due to nerve conduction issues. After birth, meningitis and other severe infections may cause hearing loss. About fifty percent of sensorineural hearing losses are based on genetic causes. Often these children have other physical or functional abnormalities beside hearing loss. Some toxins, chemicals and antibiotics may also cause sensorineural hearing loss. Other causes of sensorineural hearing loss include head injuries, radiation and exposure to loud noise.

Noise induced hearing loss is the second most common cause of sensorineural hearing loss. Listening to loud music at a rock concert or even through headphones may cause hearing loss.

What are the symptoms of hearing loss?

Most teens with hearing loss have some degree of usable hearing. About six percent of children and adolescents with hearing loss have profound loss. Hearing loss that occurs early in life will probably affect the development of speech and language, academic achievement, social skills, behavior and emotional development. The degree of problems will have an impact on the adolescent who has hearing loss.

Teens exposed to loud noise such as music may complain of ringing in the ears. Some feel as if there is a cotton plug in their ears that impede their ability to hear.

Unrecognized hearing loss will impact on academic achievement. Adolescents with hearing loss may have greater difficulty in the classroom setting and with communications. Cognitive delays may occur accompanied in some cases by behavior and disciplinary issues. Untreated or unrecognized hearing loss may impact the adolescent in sports and in music as well as self-esteem and emotional adjustment.

How is hearing loss evaluated?

An audiogram is administered to adolescents who are suspected of having hearing loss. This test provides a fundamental description of the teen’s hearing. The threshold of hearing in dB is determined for each ear using pure tones at octave intervals from 250-8,000Hz. Air conducted sounds are presented to the adolescent through earphones. Bone conducted sounds can be presented through an oscillator placed on the head. Bone conducted sounds bypass the outer and middle ears and help to define if hearing loss is attributable to conductive or sensorineural problems or a combination of both.

Further testing may include speech recognition threshold. This is the lowest intensity level where a score of about fifty percent correct is obtained on a test of certain words such as baseball, hotdog or pancake.

Tympanometry is a technique to test the ability of the middle ear to transmit sound energy or impede sound energy as a function of ear pressure in the external ear canal. This is important in certain conditions such as serous otitis media where there is fluid behind the eardrum.

If the results of hearing testing are not normal, then the teen may be referred to an otolaryngologist, neurologist or other specialists to further determine the cause of the loss. A CT scan or MRI may be necessary to study the anatomy of the middle ear.

How is hearing loss treated?

After hearing loss is identified, a full evaluation should be completed. A conductive hearing loss may be treated through correction of the underlying abnormality. For example, fluid in the middle ear may be corrected by placement of tympanostomy tubes. Teens who have sensorineural hearing loss may be fitted with a hearing aid. Hearing aids make sounds louder although not clearer. Some sounds may be distorted by the amplification.

Cochlear implants may also be utilized for teens with sensorineural hearing loss. A cochlear implant consists of a microphone, microcomputer and cochlear electrode. The microphone, which is worn behind the ear, sends the sound to a microcomputer that is connected to the microphone by a wire and worn attached to a belt. The microcomputer turns the sound into an electrical code and this is sent by radio wave to an electrode implanted in the cochlea. The cochlear implant does not give normal hearing to the adolescent, but he or she may be able to interpret the signals.

Teens with hearing loss may also benefit by changes in seating placement in classrooms. Also, the Americans with Disabilities Act may help teens with hearing loss in obtaining accommodation in the classroom or the workplace.

How is hearing loss prevented?

Appropriate prenatal care may prevent the newborn from acquiring certain infections that could lead to hearing loss. Complete immunizations during childhood also will help to avert types of meningitis that could have hearing loss as a consequence.

The adolescent can prevent hearing loss by utilizing safeguards when he or she is exposed to loud noises and music. The following are common sources of noise:

• Gunshot: 140 to 170 dB
• Jet takeoff: 140 dB
• Rock concert: 110 to 120 dB
• Stereo headphones: 100 dB
• Lawnmower: 90 dB

Prolonged and unprotected exposures to these levels of noise could cause hearing damage. Temporary or even permanent hearing impediment is reported when rock musicians have been exposed to very loud and persistent music. It is important to prevent hearing loss in loud noise situations by using adequate hearing protection or avoiding prolonged exposure.

Related topics:

Academics, chronic illness, disabilities, genetic disease, immunizations, learning disorders, meningitis, self-esteem, speech disorders