Hearing Loss in Children

 

Hearing loss in children can be frightening and confusing to parents.

Children with otitis media (ear infection) or otitis media with effusion (OME) (fluid in the ear), may have temporary hearing loss due to the fluid in the middle ear. Upon removal of the fluid, hearing usually returns to normal.

This is known as conductive hearing loss. This usually means that sound waves which hit the ear drum have a difficult time being transmitted from the ear drum into the inner ear (hearing nerve). Sensorineural hearing loss means the sound reaches the inner ear, but some defect in the hearing organ (cochlea), nerve, or brain is the cause of the hearing loss.

A less common form of hearing loss is known as mixed hearing loss. In this form of hearing loss, there are components of both conductive hearing loss and sensorineural (nerve) hearing loss.

 

Sensorineural hearing loss

 

It is estimated that one in every 1,000 newborns has significant hearing loss.

Fifty percent of these children with hearing loss have hereditary hearing loss.

Of these, one third have a syndrome associated with their hearing loss and usually have identifiable physical features which may alert the parents or physician to seek evaluation. The remaining two thirds of these children has a hearing loss for which a cause cannot be discovered.

The joint committee on infant hearing has identified ten risk factors for newborn hearing loss: 

 

1. Family history of hearing loss,

2. In utero infection,

3. Craniofacial anomalies,

4. Jaundice requiring exchange transfusion,

5. Birth weight less than 1500 grams,

6. Bacterial meningitis,

7. Apgar scores of 0 to 4 at one minute or 0 to 6 at five minutes,

8. Ototoxic medications,

9. Mechanical ventilation (greater than five days),

10. Physical appearance of known syndrome.

 

Of those children with hearing loss associated with a known syndrome, advancement in the fields of genetics and molecular biology have allowed us to identify many of these syndromes. Sixty to 70% of these children have autosomal recessive hearing impairment, making it the most common pattern of transmission. In these cases, the parents have normal hearing but carry the recessive gene, and there is a 25% chance of the children being affected. The three mode of transmission is autosomal dominant inheritance, which accounts for the other 20 - 30% of cases. In this instance, one parent usually has hearing impairment and carries the abnormal gene, and there is a 50% chance that their children will be affected. A small percentage of hereditary hearing impairment is due to x-linked abnormalities. Because girls have two x chromosomes and boys only have one, x-linked disorders are "carried" by girls and "show-up" in boys.

The terms hereditary and familial are sometimes confusing to many parents. When a disorder is hereditary, we mean to say that there is an identifiable genetic basis for the disorder. There is usually an inheritance pattern that is recognizable by examining family history and seeing a definite pattern. However, when a disorder appears to be more common in a certain family but shows no definitive pattern of inheritance, we call this familial. In hereditary disorders, a percentage of affected children can be predicted. In familial disorders, affected individuals appear randomly and cannot be predicted.

 

Common Types of Hereditary Hearing Impairment

 

1. • Autosomal Recessive 

   • Usher syndrome

   • Pendred syndrome

   • Jervell and Lang-Nielson syndrome

2. • Autosomal Dominant 

   • Treacher-Collins syndrome

   • Goldenhar syndrome

   • Waardenburg syndrome

   • branchio-oto-renal syndrome

   • neurofibromatosis type II

   • otosclerosis

   • Alport syndrome 

   • autosomal dominant delayed (late) progressive sensorineural hearing impairment.

3. • X-linked Disorders 

   • Alport syndrome

   • X-linked mixed hearing impairment with stapes fixation and perilymphatic gusher.

 

Hereditary causes of hearing loss are suspected in all cases of hearing impairment. Two factors, which increase levels of suspicion, are U-shaped audiograms and consanguinity of the parents (parents related before marriage). In general, the younger the child upon diagnosis and the less apparent the alternative causes, the more likely the diagnosis is of hereditary hearing impairment. A hereditary cause, however, must be considered even in adolescents and young adults because hereditary hearing impairment can occur with delayed onset. When hereditary hearing impairment is suspected, parents and siblings of the affected patient should also have audiologic testing.

 

Testing for hearing loss

 

There are no blood tests, which are available to diagnose specific type of hearing loss. Your physician will probably order a hearing assessment by audiogram or ABR (auditory brain stem response). In addition, although no specific blood test may identify hearing loss, some testing may be suggested by your physician and may include urinalysis (Alport syndrome), thyroid function studies (Pendred syndrome), EKG (JLN syndrome), ophthalmologic exam (Usher syndrome), computerized tomography (CT scan) or magnetic resonance imaging (MRI).

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