Child during the Auditory Steady State Response (ASSR) test

Paediatric hearing impairment

The impairment of auditory perception, called hearing impairment, is a problem which is particularly important to address during childhood, because intellectual and social development depends to a significant extent on good hearing function.

One out of 100 newborns is affected by hearing impairment, with one out of 750 cases being affected by severe hearing impairment. Similarly, 40% of children under the age of 5 present with episodes of serous otitis lasting longer than 3 months, which are a frequent cause of delayed speech development and failure at school. This has encouraged us to set up the Paediatric Hearing Impairment Unit aimed at early diagnosis and treatment.

Alarm signs. How to find out whether your child does not hear well

Ages 0 to 1

  • The child is excessively calm
  • It does not turn its head when exposed to loud or familiar sounds
  • It does not utter any articulate sounds

Ages 1 to 2

  • It has not started to speak
  • It does not understand simple instructions
  • It does not recognise its name

Ages 3 to 4

  • It often replies with "what?" when asked questions
  • It is incapable of forming sentences of 3 or more words
  • It is unable to explain what is happening

In general

  • Frequent colds and otitis. Snoring at night. Breathing with the mouth open
  • An introvert, distracted or aggressive child
  • Delayed progress at school
  • Doubts of the mother or teacher with regard to the child's hearing

Evoked potentials of auditory steady state response

There has been increasing awareness among paediatricians and otorhinolaryngologists of the need for early diagnosis of deafness. For that reason, the Otorhinolaryngological Surgery of Dr J. Coromina at Teknon Medical Centre in Barcelona has set up the Paediatric Audiology Unit coordinated by Dr Carlos Costa, Paediatric Audiologist. This Unit has been developing its neonatal screening program for several years.

Whenever a child does not pass an auditive screening or where there is reason to suspect a hearing impairment, it is critically important to offer a full range of diagnostic tools in order to determine the degree and type of hearing loss in the most precise and objective manner. In addition, delays in undertaking audiological tests must be avoided given that speech therapy must be initiated in children with hearing loss and hearing aids must be fitted by the age of 6 months.

The most common audiological tests, namely Brainstem Auditory Evoked Potentials, are not precise enough in certain cases because they only provide information about the frequencies from 2,000 a 4,000 Hz. The remaining frequencies are not covered by the test, although they are the most important ones.

This is why the Paediatric Audiology Unit has been using the Auditory Steady State Response (ASSR) technique since 2004. This technique permits reliable audiometric testing across the entire frequency spectrum of human hearing rather than solely focusing on high-pitched tones. This technique is particularly useful in children aged 3 to 4 or 5 months.

The obvious benefits of the Auditory Steady State Response (ASSR) technique can be explained by means of the following example:

  • The Auditory Steady State Response (ASSR) of a child with a neurosensory hearing impairment provides us with an audiometric curve for the entire frequency spectrum. This allows us to fit hearing aids more efficiently.
  • By contrast, the Brainstem Auditory Evoked Potentials technique only provides us with partial information, showing us the status across a limited frequency range.

We perform complete audiological tests in children with suspected hearing impairments. These are based on following techniques:

  • Otoacoustic emissions
  • Brainstem Auditory Evoked Potentials (BAEPs)
  • Auditory Steady State Response (ASSR)
  • Paediatric audiometry (paediatric audiometry and Suzuky Test)

Example of an ASSR of a child with a severe neurosensory hearing impairment: We see the audiometric curve for the entire frequency spectrum from 250 Hz to 4,000 Hz. The information provided by this screening allows us to fit hearing aids more efficiently in order to achieve the best possible performance.

The BAEPs of the same child, on the other hand, only provide us with information on the hearing threshold from 2,000 to 4,000 Hz, while no specific information is provided on the remaining frequency ranges. In contrast to the ASSR test, the information provided by BAEPs is incomplete.