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Severe hearing loss
The softest sounds a child hears are at levels of 70 dB to 90 dB. A child with a severe hearing loss will not hear voices, unless speech is very loud. Without amplification, the individual will not recognize any speech through listening alone. With amplification, a child with severe hearing loss should have good ability to hear speech, but may still have some difficulty distinguishing all sounds.
Profound hearing loss
The softest sounds a child hears are at levels of 90 dB or more. Historically, a child with a profound hearing loss would be called deaf, but a more appropriate term is “a child with a profound hearing loss”. Very loud sounds will not be detected. A child will rely on vision rather than hearing for primary communication.
Many children with profound hearing loss with hearing aids can detect moderately loud sounds and spoken conversation under ideal listening conditions. Many children still need visual communication to assist them in understanding spoken conversation.
Unilateral hearing loss
Because one ear still has normal hearing, a child with unilateral hearing loss will hear well in “quiet and close” situations. However, children with a hearing loss in one ear will have hearing in situations when noise and distance create listening challenges, especially if the good ear is close to the noise. Individuals with unilateral hearing loss usually have difficulty knowing where sounds are coming from (localizing). If a child with unilateral hearing loss has usable hearing then the child will receive benefit from the use of a hearing aid, a standard hearing aid may not be helpful when the hearing loss is more severe. However, recent studies suggest that 25-35% of children with unilateral hearing loss are at risk for failing a grade in school. Therefore, a child with unilateral hearing loss will often benefit from an amplification device, an FM system, in the classroom.
Etiology of Hearing Loss
Causes of permanent hearing loss in children
Most professionals working with hearing loss are in general agreement that the cause of hearing loss in about 40% is Non-genetic, and about 60% Genetic.
Non-genetic hearing loss
Non-genetic hearing loss is most often caused by illness or trauma before birth or during the birth process.
Older infants and young children can also hearing loss due to illness or trauma.
• Congenital infections
Some viral infections are known to be associated with hearing loss. These infections carry the highest risk of causing hearing loss if the mother has the illness during pregnancy or passes the infection to her baby during the birth process. The primary infections are toxoplasmosis, syphilis, rubella (german measles), cytomegalovirus (also known by the initials CMV) and herpes. The amount of hearing loss that can result varies widely and some babies show no hearing loss at all, even if they have one of these infections. These infections can affect other systems in the body as well and medical professionals will need extensive birth history and test information to identify these infections as a cause for hearing loss. Congenital CMV infection is the leading cause of acquired hearing loss in infants.
• Complications associated with prematurity
Low birth weight has also been identified as a risk factor for hearing loss. Newborn specialists identify 1500 grams (approx. 3.3 lbs.) as a cut-off point, with children weighing less than 1500 grams having an increased likelihood of hearing loss. For infants that are born premature, illnesses associated with prematurity can cause hearing loss.
Hyperbilirubinemia (jaundice) that is severe enough to require a blood transfusion can also result in hearing loss. This is related to the potential damage that high levels of bilirubin can cause to the nerves of hearing.
Sometimes medications that are known to be ototoxic (damaging to hearing) are prescribed to babies, usually to treat serious infections or birth complications. The most common ototoxic medications used at this time include a family of antibiotics called aminoglycosides with names such as gentamycin, tobramycin, kanamycin, and streptomycin. They present more of a risk to hearing when they are used multiple times or in combination with other medications, such as diuretics.
All babies are evaluated at birth on a 10-point scale, called an APGAR score, given at 1 minute and 5 minutes after birth. The higher the score, the healthier the baby is. When babies have scores of 0-4 at one minute or 0-6 at five minutes, their risk for having hearing loss increases.
Also, prolonged mechanical ventilation for a duration of five days or longer due to persistent pulmonary hypertension increases the risk for hearing loss. These conditions of breathing problems and other distress at birth do not mean that a baby will always have a hearing loss, but do indicate the need to monitor hearing closely.