World Hearing Day | Causes of Infant Hearing Loss

 

There are more than many reasons for hearing loss. Each of these reasons arises from a problem in the hearing pathway. This pathway includes the external ear, middle ear, inner ear, auditory nerve and the auditory centers in the brain. Normal hearing requires that all parts of the ear pathway are working correctly.

 

Causes of Hearing Loss That Occur During or Soon After Birth:

  • Hypoxia (where the baby does get not enough oxygen)
  • In utero infections or meningitis as a newborn
  • Genetic causes of hearing loss
  • Abnormal development of the brain or ear structures

 

Causes of Hearing Loss That Can Occur Later in a Child’s Life:

  • Infection (such as meningitis, chronic middle ear infections, or measles)
  • Injuries (such as head injury or injuries to the ear structures)
  • Certain drugs (such as the antibiotic gentamicin)
  • Neurological disorders
  • Genetic conditions
  • Tumors, particularly of the auditory nerve
  • Noise induced hearing loss
  • Advancing age
  • Many cases have an unknown cause

 

Causes of Conductive Hearing Loss:

  • Abnormalities in the structure of the ear canal or middle ear
  • Buildup of ear wax
  • Ear infections (especially repeated infections)
  • Foreign objects in the ear
  • Injury or trauma to the middle ear structures
  • Rupture of the eardrum
  • Tumors within the ear
  • Disruption of the bones of the middle ear

It is usually possible to treat this kind of hearing loss with medication or surgery.

 

Causes of Sensorineural Hearing Loss Include:

  • Exposure to certain toxic chemicals or medications while in the womb or after birth
  • Genetic and neurologic conditions
  • Infection before birth, including cytomegalovirus infection, or infection with German measles during the early stages of pregnancy
  • Infections after birth, such as bacterial meningitis and viral infections that affect the inner ear
  • Problems with the structure of the inner ear
  • Toxins that damage the inner ear hair cells
  • Noise induced hearing loss
  • Many cases have an unknown cause
There is no cure for sensorineural hearing loss. People with this type of hearing loss may benefit from hearing aids or a cochlear implant.Mixed hearing loss (a combination of conductive and sensorineural) can be caused by the same things that cause conductive and sensorineural hearing loss.

Why is it important to screen for hearing loss in all newborn infants?

Significant hearing loss is the most common disorder at birth. Approximately 1%-2% of newborns are affected.

Hearing loss in infants should be identified, and when possible treated, prior to 6 months of age. This recommendation is based on studies that have shown that children identified with hearing loss prior to 6 months of age have a better chance of developing skills equivalent to their peers by the time they enter kindergarten. Children not identified until later (for example, it is very common to first identify hearing impaired children at age 2 to 3 years) may ultimately suffer from irreversible and permanent impairments in speech, language, and cognitive abilities when compared to their peers.

Prior to the implementation of hearing screen programs, it was customary to only test those newborns who had known significant risk factors for hearing loss. This group included infants whose mothers suffered from illness during pregnancy, those who had a family history of hearing loss, or those who were exposed to drugs known to affect hearing. In addition, infants with the following conditions were included for hearing screening:

  • low birth weight and/or prematurity, or oxygen deprivation or breathing difficulties at birth;
  • high bilirubin levels (yellow color);
  • syndromes associated with hearing loss;
  • abnormal head or face structures;
  • infections such as cytomegalovirus, syphilis, herpes, or toxoplasmosis; or
    low Apgar scores (which assess several health factors at one and again at five minutes after birth).

However, despite the testing of all infants who fell into this “high-risk registry,” over half of all newborns with hearing loss were missed!

In order to identify this large group of hearing-impaired infants not identified with current testing protocols, it is now recommended that all newborns have a hearing test prior to discharge from the hospital. The goal of this program is to identify all hearing-impaired infants at an early age, thereby increasing these children’s chance at healthy and more productive lives.

Types of Cancer

Our bodies are made up of billions of cells. The cells are so small that they can only be seen under a microscope. These cells are grouped together to make up the tissues and organs of our bodies. These cells are basically the same, but they vary in some ways. This is because the body organs do very different things.

For example, nerves and muscles do very different things. So nerve and muscle cells have different structures.

Cancers can be grouped according to the type of cell they start in. There are 5 main categories

  • Carcinoma – cancer that begins in the skin or in tissues that line or cover internal organs. There are a number of subtypes, including adenocarcinoma, basal cell carcinoma, squamous cell carcinoma, and transitional cell carcinoma
  • Sarcoma – cancer that begins in the connective or supportive tissues such as bone, cartilage, fat, muscle, or blood vessels
  • Leukaemia – cancer that starts in blood forming tissue such as the bone marrow and causes large numbers of abnormal blood cells to be produced and go into the blood
  • Lymphoma and myeloma – cancers that begin in the cells of the immune system
  • Brain and spinal cord cancers – these are known as central nervous system cancers
  • Cancers can also be classified according to where they start in the body, such as breast cancer or lung cancer.