Hearing Level / Hearing Loss

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Hearing Level / Hearing Loss

Causes of Hearing Loss

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Learning About Causes of Hearing Loss
Diagnostic Process
Case History / Examination
Medical Laboratory Tests
Causes of Hearing Loss
Hearing Loss/Language
Frequently Asked Questions

LEARNING ABOUT CAUSES OF HEARING LOSS

One of the first questions you may have is: What caused my baby's hearing loss? This is a normal reaction. Sometimes the cause of hearing loss can be determined and sometimes it can not.

Your doctor will guide you through the process to determine the cause of your baby's hearing loss. The first step in the process is a review of your family history, your baby's birth history, and an examination. The second step includes medical and laboratory tests. These test results will help the doctor determine the cause of your baby's hearing loss.

There can be several reasons why there is a hearing loss.

Genetic factors and many diseases
Treatment for serious illnesses
Environmental factors including head trauma

Sometimes the hearing loss is caused by a combination of factors.

About 50% of infant hearing loss is due to genetic factors. A genetic factor can be inherited or non-inherited and refers to the “code” that determines the unique characteristics of your baby. Twenty-five percent of infant hearing losses are non-genetic (disease, treatment side effects, and environment trauma), and the remaining 25% are due to unknown causes. Learning about possible causes of hearing loss can help you provide specific information to professionals. The more information professionals have, the more likely they can help you find answers to your questions.

Pie Chart representing the causes of hearing loss.

DIAGNOSTIC PROCESS

Physicians who specialize in ear, nose and throat problems are commonly referred to as ENT physicians. They are also called otolaryngologists. Some ENT physicians specialize in working with babies and young children, and these ENT physicians are called pediatric ENT's or pediatric otolaryngologists. Some ENT physicians specialize in ears. Since “oto” means ear, these physicians are called otologists or neuro-otologists.

How will the doctor determine the cause of my baby's hearing loss?
When you go to the doctor because of an illness you are asked questions about your illness, you are examined, and participate in some tests. The process of determining the cause of your baby's hearing loss is similar. The doctor will ask you questions about your family history, your pregnancy, and your baby's health. The doctor will then examine your baby and your baby's ears. Diagnostic tests might be ordered to help determine the cause of your baby's hearing loss, and in addition to hearing tests to determine the type and degree of hearing loss, the doctor may order a urinalysis, blood work, x-rays, and eye, heart, and kidney tests. The doctor uses the results of the family history, examination, and test results to decide the cause of hearing loss. Sometimes the cause of hearing loss is straightforward, but in many cases, the cause of hearing loss may be very complicated or unknown.

How can I be sure that my baby has a hearing loss?
Hearing tests for babies are based on objective and reliable measures of how the ear works. If the ear does not work properly it affects the baby's ability to hear. The diagnostic hearing tests are very accurate and will determine whether or not your baby's ears are working properly.

Should I get a second opinion?
It is always a good idea to get a second opinion, because it is important for you as a parent to have confidence in the diagnosis. The down side is that second opinions take time. While you want to know for sure, you don't want to delay intervention. One alternative might be to schedule a second opinion at the same time that you begin the early intervention and amplification process. Make the assumption that the second opinion will provide additional support for the initial diagnosis and go ahead and take the necessary steps to get slotted in for early intervention services.

CASE HISTORY / EXAMINATION

The first step in the process of determining the cause of your baby's hearing loss is a review of your family history, your baby's birth history, and an examination.

What questions will the doctor ask me about the history of my baby's hearing loss?
Did your baby pass the birth hearing screening or was your baby referred at birth for additional testing? When did you first suspect that your baby had a hearing loss? Did anyone in the maternal or paternal extended family have a hearing loss beginning as a child? Was the cause of the family member's hearing loss known? Was the pregnancy normal or were there complications? Was the mother ill during pregnancy or did she take any medication? Was the length of pregnancy normal or was your baby premature? Was your baby healthy at birth? How much did your baby weigh at birth? Was your baby jaundiced at birth? Did your baby spend time in the neonatal intensive care unit after birth? Did your baby require ventilation, blood transfusion, or other treatment? Was your baby given antibiotics or other medication before birth discharge from the hospital? Did your baby have any serious illness early in life? Is your baby on target with developmental milestones or have you noticed any developmental delay? At what age did your baby smile, sit up, crawl, walk, or say the first word?

The answers to these questions will help guide the doctor in making decisions about which medical or laboratory tests to order for your baby.

Is there a family history of early childhood hearing loss?
If there are other family members who were diagnosed with hearing loss at an early age, it might be related to a genetic cause.

Was the pregnancy uneventful?
If the mother had a disease during pregnancy, it could affect the baby's development. There are some diseases that are likely to result in this outcome. If the mother suffered physical trauma during pregnancy, it could result in a hearing loss for the baby.

Did the birthing process go as planned and expected?
If the baby is premature with a very low birth weight, the likelihood of a hearing loss increases. If there are complications during pregnancy, a hearing loss could result.

Was the baby healthy at birth or did the baby require time in the neonatal intensive care unit?
Babies who are sick at birth may require medication, ventilation, or a transfusion. These treatments can contribute to a hearing loss. Hearing loss is a characteristic of some syndromes and diseases that babies are born with. Some infections can cause hearing loss.

What kind of physical examination will the doctor do?
The ENT doctor will look at the overall health of your baby. The doctor will use a tool with a light on it to look into your baby's ears, nose, and mouth. The doctor will examine the baby's ears for otitis media, and will also look at your baby's eyes and listen to your baby's heart.

What is otitis media?
Otitis media is an ear infection caused when fluid collects in the baby's middle ear. Ear infections are usually a temporary condition, with symptoms often including fever, earache, and temporary hearing loss. Some infants do not have symptoms, however chronic otitis media can lead to permanent hearing loss. If your baby has fluid in the middle ear, the doctor will treat this condition. When this condition is cleared up, other diagnostic tests may be requested.

What information might the doctor provide?
The doctor may explain that finding out the cause of the hearing loss may or may not change the treatment. What you do about the hearing loss and how soon you do it will make a difference in your child's ability to learn language. Language development is the basic skill that children need in order to communicate, to learn how to read, and to have a successful experience throughout their school years. The doctor will emphasize that regardless of the cause of hearing loss - intervention should not be delayed.

MEDICAL / LABORATORY TESTS

The second step in the diagnostic process includes medical and laboratory tests. The test results will help the doctor determine the cause of your baby's hearing loss.

What tests might the doctor order?
The doctor needs to know the type and degree of your baby's hearing loss. The doctor will review any hearing test results that you have, and if the doctor needs more information about the hearing loss, additional hearing tests will be ordered. Other medical tests that the doctor might order include laboratory tests and x-rays. Laboratory tests include a urinalysis, blood tests, or a saliva swab. Special x-rays that can help the doctor determine the cause of hearing loss include computerized tomography (CT) scans or magnetic resonance imaging (MRI). The doctor might also want to see eye, heart, or kidney tests because some causes of hearing loss also affect other parts of the body. These eye, heart, and kidney tests might help determine the cause of your baby's hearing loss.

What is a urinalysis?
A urinalysis is the microscopic and chemical analysis of urine. A urinalysis can assist the doctor in the diagnosis of infections, diseases, dehydration, kidney problems, jaundice and many other conditions.

What blood tests might be ordered?
Analysis of the nutrients, oxygen, carbon dioxide, and metabolic by-products in the blood can provide information that can help the doctor make a diagnosis. Connexin 26, a special blood test used to diagnose genetic hearing loss, might also be ordered.

What kind of special x-rays might be recommended and what would they show?
Computerized tomography (CT) scans and magnetic resonance imaging (MRI) tests are special types of x-rays that might be recommended. The CT scan uses a computer to generate multiple x-rays in small slices. This special x-ray shows soft tissue structures that cannot be shown using other x-ray techniques. The MRI is a special imaging technique that uses a large magnet to help visualize the soft tissues. MRI images are very good for soft tissues like the brain, spinal cord, and joints. CT and MRI are used to visualize the parts of the ear to see if they have developed properly. Refer to the “All About Hearing” section for more information about the parts of the ear and the way the ear works. The structure of the ear can help provide the doctor with clues about the cause of hearing loss.

Why would an eye examination be recommended?
Your baby might be referred for an eye examination, since many problems with the ear can also affect the eyes. An eye examination can help the doctor diagnose the cause of the hearing loss.

Why would a heart examination be recommended?
Many problems that cause a hearing loss can also cause a heart condition. The doctor will want to rule out a heart condition and make sure that your baby gets treatment if a heart condition is present.

Why would a kidney examination be recommended?
Some diseases and genetic conditions that cause hearing loss also involve the kidney. The doctor will use the information about the baby's kidneys to help diagnose the cause of hearing loss.

CAUSES OF HEARING LOSS

Genetic factors account for 50% of infant hearing loss. Together, disease, side effects of treatment and environment account for 25% of infant hearing loss. The cause of the remaining 25% of infant hearing loss is unknown.

Genetic - The part of the body that controls the unique characteristics of a person is a gene. Genes determine characteristics such as eye and hair color. A genetic hearing loss is caused by information or ‘code’ carried by the genes.

Disease - An illness, infection, or sickness is a disease. A disease affects the way the body functions, and there are several diseases that can cause hearing loss. Some diseases are transmitted from mother to baby during pregnancy or birth. Other diseases are contracted after birth.

Side Effects of Treatment - Some babies are very sick at birth. Medication or other types of treatment are needed in order for the baby to get well. Sometimes medication and other treatments are needed in order to save the baby's life, but it is important to know that some of these medications and treatments can cause hearing loss.

Environmental Factors - Environmental factors are events that occur in the baby's ‘living space’ either before or after birth. There are many events that can cause hearing loss.

More Information about Causes

Genetics

What are the different types of genetic hearing loss?
There are two types of genetic hearing loss. About sixty-six percent of genetic hearing losses are not related to syndromes. Thirty four percent are related to syndromes. A nonsyndromic hearing loss means that the hearing loss occurs without involvement of other systems in the body. A syndromic hearing loss means that the hearing loss occurs in combination with a recognized set of characteristics.

What are the characteristics of nonsyndromic hearing loss?
Nonsyndromic hearing loss is an inherited pattern of hearing loss that occurs at birth or in early childhood. The most common type of nonsyndromic genetic hearing loss is called Connexin 26 and is tested by a blood test. There are many other hearing loss genes that are not as easy to test for.

What is a syndrome?
A syndrome is a recognized set of characteristics that occur together. Syndromes are often named after the person that first described it.

What are the characteristics of syndromic hearing loss?
The characteristics of the hearing loss depend on the syndrome. Some syndromes are associated with conductive hearing loss. Other syndromes are associated with sensorineural or mixed hearing loss. The degree of hearing loss also depends on the type of syndrome. More importantly, syndromes are a set of characteristics that affect other parts of the body such as the eyes, face, head, heart, bones, and kidneys.

Are there other types of genetic hearing loss?
Sometimes there is no reason to suspect a hearing loss; the ear is just not shaped properly. The outside part of the ear can be absent or misshapenor the ear canal can be misshapen or closed. At times the inner ear consisting of the cochlea might be misshapen or malformed. The baby could be born with an enlarged vestibular aqueduct or a congenital fistula. In some babies, the hearing nerve could be small or absent. It is not always possible to determine whether these ear anomalies are genetic or not, however, in the future, there may be tests developed that can help provide this information.

Diseases

What are some of the diseases that could contribute to a hearing loss for the newborn?
Some of the more common diseases associated with hearing loss include cytomegalovirus, herpes simplex, rubella, syphilis, toxoplasmosis, and varicella.

What is cytomegalovirus (CMV)?
CMV is a very common virus. About three percent of babies are born with this virus. Many babies do not have any symptoms, but a small percentage of the babies born with CMV have symptoms. Of the babies that have symptoms, about fifty percent are born with hearing loss or develop hearing loss.

What is herpes simplex?
Herpes simplex is a virus that is passed from the mother to baby during birth. Many of the babies born with herpes develop a combination of neurological problems and hearing loss.

What is rubella?
Rubella is a type of measles. If a mother has rubella during the first trimester, it causes heart problems, eye problems and hearing loss. Rubella was a common cause of hearing loss before the vaccine was available. Rubella is now a relatively rare cause of hearing loss.

What is varicella?
Varicella is also called chicken pox. Varicella is transmitted to the baby during the first two trimesters of pregnancy. Characteristics of varicella include hearing, skin, eye, bone, and neurological problems.

What is syphilis?
Syphilis is a bacterial disease transmitted to the baby during pregnancy. Babies born with syphilis have teeth, bone, eye, and neurologic problems in addition to hearing loss.

What is toxoplasmosis?
Toxoplasmosis is a parasite infection. It is transmitted from mother to baby during pregnancy. The parasite affects the brain, eye, and ears. Babies born with toxoplasmosis frequently have no symptoms at birth. Hearing loss develops in about ten percent of infected babies.

What is meningitis?
Meningitis is a disease that is contracted after birth. It is an infection or inflammation of the meningis or lining of the brain. It can be caused by bacteria or by a virus and may result in sensorineural hearing loss. Availability of a vaccine has decreased some types of meningitis.

Side Effects of Treatment

What are some of the medications used to treat sick babies that can cause hearing loss?
Some antibiotics that can cause hearing loss include gentamycin, tobromycin, kanamycin and streptomycin. Medications like dopamine or furosemide used to treat lack of oxygen have also been linked to hearing loss. Other medications that can cause hearing loss are used as treatment for cancer, like cisplatinum. If your baby is very sick and is in the neonatal intensive care unit ask the doctor to keep you informed about the medications and potential side effects of treatment.

What are some other treatments that can cause hearing loss?
Jaundice is a yellowing of the skin related to elevated bilirubin levels. This condition is called hyperbilirubinemia. The treatment for hyperbilirubinemia includes light treatment and may include an exchange transfusion. About twenty percent of babies requiring exchange transfusion develop hearing loss.

Why are premature infants at risk for hearing loss?
Premature infants and infants with extremely low birthweight sometimes have difficulty breathing normally. This is called persistent pulmonary hypertension (PPHN). The treatment for PPHN may be intubation, ventilation, or oxygen treatment. Hearing loss has been associated with these treatments. Babies with PPHN that are very, very sick may require a treatment called extracorporeal membrane oxygenation (ECMO). Up to fifty percent of babies that survive treatment may develop hearing loss. The hearing loss often develops after hospital discharge, so it is important that these babies receive regular hearing evaluations until they are at least three years of age.

Environmental Factors

What is fetal alcohol syndrome?
Fetal exposure to alcohol during pregnancy can cause conductive or sensorineural hearing loss. Other features include slow growth development, misshapen facial features, and behavior disorders.

What are ototoxic medications and what effect might it have on a baby's hearing?
Medication taken by a mother during pregnancy can cause hearing loss. Trimethadione is used to treat seizures and can cause hearing loss if taken by the mother during pregnancy. Other medications known to cause sensorineural hearing loss include acetylsalicylic acid, aminoglycosides, neomycin, nortriptyline, quinine, streptomycin, thalidomide, vancomycin, and viomycin.

What is lead poisoning?
Lead poisoning is caused by environmental exposures such as paint that is lead based. This type of paint used to be commonly used and may still exist in some older homes. Babies who eat lead paint chips can get lead poisoning. Lead poisoning causes brain damage and hearing loss.

What is trauma?
Trauma is damage or injury that accidentally occurs. Infant hearing loss can be caused from head trauma, or other types of ear injuries.

What kind of head trauma might result in a hearing loss?
Babies born with an enlarged vestibular aqueduct are highly susceptible to head trauma. For these babies, minor head trauma can induce or increase a permanent hearing loss. Head trauma can cause the bones in the middle ear to be broken apart. Severe head trauma can result in a fracture of the temporal bone causing hearing loss.

HEARING LOSS / LANGUAGE

The age at which your baby's hearing loss occurs makes a big difference. Babies that are born with a hearing loss have no experience hearing language. Their brain has not had the chance to practice interpreting what they hear and intervention is usually more intensive. Babies who were born with normal hearing, but acquired a hearing loss before two years of age have limited experience with hearing language. These babies still require intensive intervention in order to catch up or in order to develop age appropriate communication skills.

What is congenital hearing loss?
Congenital hearing loss can occur during conception, pregnancy, or at birth. The causes of congenital hearing loss include genetic factors and disease. It can also occur as a result of prematurity. Sometimes there is no apparent cause, the ear just doesn't develop properly during the early stages of pregnancy.

What is acquired hearing loss?
If we know the baby's hearing was normal at birth, and then the hearing loss occurred, we call this an acquired hearing loss. Acquired hearing loss includes side effects of treatment, environmental factors, and trauma. Acquired hearing loss could occur at birth from birth trauma or by contracting a disease during the birthing process. Sometimes treatment in the NICU may lead to a hearing loss. There are many illnesses that a baby might have in the first few months of life that could result in a loss of hearing.

What does prelingual hearing loss mean?
Prelingual means that the hearing loss occurs before the baby learns to talk. Babies who were born with normal hearing, but acquired a hearing loss before two years of age have limited experience with hearing language. Prelingual hearing loss has a bigger impact on speech and language development and communication skills than post-lingual hearing loss. The more speech and language a baby is exposed to before the hearing loss occurs, the easier it will be for the baby to learn to communicate.

What does postlingual hearing loss mean?
Postlingual hearing loss means that the baby developed hearing loss after speech and language development began. If the hearing loss occurs or is acquired after the age of two years, or after the child has learned some communication skills - then intervention builds on what the child has already learned. A baby with post-lingual hearing loss has had some experience listening to the rhythm of speech.

Does it matter if the hearing loss is prelingual or postlingual?
The age at which your baby's hearing loss occurs makes a big difference. Babies that are born with a hearing loss or have a congenital hearing loss have no experience hearing language. Babies that are born with normal hearing or have an acquired hearing loss have some limited experience with speech and language. Regardless of when the hearing loss occurred plans must always be based on the individual needs of the child and family.

Hearing Loss Timeline
A "congenital" hearing loss refers to a hearing loss present at birth. Other causes of hearing loss may be related to events that result in admission to the neonatal intensive care unit. Often, it is difficult to know for sure if the hearing loss is congenital or acquired, so the term "prelingual" hearing loss is used. Prelingual hearing loss refers to any hearing loss that occurs before language is developed.

This graphic demonstrates hearing loss can occur at any point in a child's life.

* Hearing Loss can occur at any point on this timeline.

FREQUENTLY ASKED QUESTIONS

What kind of physical examination will the doctor do?
The ENT doctor will look at the overall health of your baby. The doctor will use a tool with a light on it to look into your baby's ears, nose, and mouth. The doctor will examine the baby's ears for otitis media. The doctor will also look at your baby's eyes and listen to your baby's heart.

What is otitis media?
Otitis media is an ear infection. Fluid collects in the baby's middle ear. Ear infections are usually a temporary condition. Symptoms often include fever, earache, and temporary hearing loss. Some infants do not have symptoms. Chronic otitis media can lead to permanent hearing loss. If your baby has fluid in the middle ear, the doctor will treat this condition. When this condition is cleared up, other diagnostic tests may be requested.

What tests might the doctor order?
The doctor needs to know the type and degree of your baby's hearing loss. The doctor will review any hearing test results that you have. If the doctor needs more information about the hearing loss, additional hearing tests will be ordered. Other medical tests that the doctor might order include laboratory tests and x-rays. Laboratory tests include a urinalysis, blood tests, or a saliva swab. Special x-rays that can help the doctor determine the cause of hearing loss include computerized tomography (CT) scans or magnetic resonance imaging (MRI). The doctor might want to see eye, heart, or kidney tests. Some causes of hearing loss affect other parts of the body. Eye, heart, and kidney tests might help determine the cause of your baby's hearing loss.

What is genetic hearing loss?
The part of the body that controls the unique characteristics of a person is a gene. Genes determine eye and hair color. A genetic hearing loss is caused by information carried by the genes. There are two types of genetic hearing loss. About sixty-six percent of genetic hearing losses are not related to syndromes. Thirty four percent are related to syndromes. A nonsyndromic hearing loss means that the hearing loss occurs without involvement of other systems in the body. A syndromic hearing loss means that the hearing loss occurs in combination with a recognized set of characteristics.

What side effects of treatment can cause hearing loss?
Some babies are very sick at birth. Medication or other types of treatment are needed in order for the baby to get well. Sometimes medication and other treatments are needed in order to save the baby's life. Some of the medications and treatments can cause hearing loss. Some antibiotics that can cause hearing loss include gentamycin, tobromycin, kanamycin and streptomycin. Medications like dopamine or furosemide used to treat lack of oxygen have also been linked to hearing loss. Other medications that can cause hearing loss are used as treatment for cancer, like cisplatinum. The treatment for hyperbilirubinemia includes light treatment and may include an exchange transfusion. About twenty percent of babies requiring exchange transfusion develop hearing loss. If your baby is very sick and is in the neonatal intensive care unit ask the doctor to keep you informed about the medications and potential side effects of treatment.

Why are premature infants at risk for hearing loss?
Premature infants and infants with extremely low birthweight sometimes have difficulty breathing normally. This is called persistent pulmonary hypertension (PPHN). The treatment for PPHN may be intubation, ventilation, or oxygen treatment. Hearing loss has been associated with these treatments. Babies with PPHN that are very, very sick may require a treatment called extracorporeal membrane oxygenation (ECMO). Up to fifty percent of babies that survive treatment may develop hearing loss. The hearing loss often develops after hospital discharge. It is important that these babies receive regular hearing evaluations until they are at least three years of age.

What are environmental factors?
Environmental factors that can contribute to newborn hearing loss include fetal alcohol syndrome, ototoxic medication taken by the mother during pregnancy, lead poisoning, and head trauma.

Does the age at which my baby's hearing loss occurs make any difference?
It makes a big difference. Babies that are born with a hearing loss have no experience hearing language. This is called a congenital hearing loss. Their brain has not had the chance to practice interpreting what they hear and intervention is usually more intensive. Babies who were born with normal hearing, but acquired a hearing loss before two years of age - have limited experience with hearing language. These babies still require intensive intervention in order to catch up or in order to develop age appropriate communication skills. If we know the baby's hearing was normal at birth - and then the hearing loss occurred, we call this an acquired hearing loss. If the hearing loss occurs or is acquired after the age of two years - or after the child has learned some communication skills - then intervention builds on what the child has already learned. Regardless of when the hearing loss occurred plans must always be based on the individual needs of the child and family.

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Information on this web site was obtained from the Infant Hearing Guide developed in a cooperative project between the University of Arkansas for Medical Science, Arkansas Children's Hospital and the University of Arkansas RRTC and we would like to acknowledge their work.

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