Hearing loss can be congenital, occurring prior to birth, or acquired, as the result of an illness during childhood.
- Maternal rubella or cytomegalovirus infection during pregnancy
- Genetic deafness can be autosomal recessive or autosomal dominant
- Associated syndromes, for example Down’s syndrome
- Hypoxia during or after birth
- Meningitis and encephalitis
- Otitis media or glue ear
The UK newborn hearing screening programme (NHSP) tests hearing in all neonates. This involves special equipment that delivers sound to each eardrum individually and checks for a response. This can identify congenital hearing problems early.
Children with hearing difficulties may present with parental concerns about hearing or with behavioural changes associated with not being able to hear:
- Ignoring calls or sounds
- Frustration or bad behaviour
- Poor speech and language development
- Poor school performance
Younger children (under 3 years) are tested by looking for a basic response to sound (i.e. turning towards a sound). Older children can be tested properly with headphones and specific tones and volumes. The results of audiometry testing are recorded on an audiogram, which can help identify and differentiate conductive and sensorineural hearing loss.
Audiograms are charts that document the volume at which patients can hear different tones. The frequency in hertz (Hz) is plotted on the x-axis, from low to high pitched. The volume in decibels (dB) is plotted on the y-axis, from loud at the bottom to quiet at the top. It is worth noting that the lower down the chart, the higher the decibels and the louder the volume.
Hearing is tested to establish the minimum volume required for the patient to hear each frequency, and this level is plotted on the chart. The louder the sound required for the patient to hear, the worse their hearing is and the lower on the chart they will plot. For example, a 1000 Hz sound will be played at various volumes until the patient can just about hear the sound. If this sound is heard at 15 dB, a mark is made on the chart where 1000 Hz meets 15 dB. If this sound can only be heard at 80 dB, a mark is made where 1000 Hz meets 80 dB.
Hearing is tested in both ears separately. Both air and bone conduction are tested separately. The following symbols are used to mark each of these separate measurements:
- X – Left sided air conduction
- ] – Left sided bone conduction
- O – Right sided air conduction
- [ – Right sided bone conduction
When a patient has normal hearing, all readings will be between 0 and 20 dB, at the top of the chart.
In patients with sensorineural hearing loss, both air and bone conduction readings will be more than 20 dB, plotted below the 20 dB line on the chart. This may affect only one side, one side more than the other or both sides equally.
In patients with conductive hearing loss, bone conduction readings will be normal (between 0 and 20 dB), however air conduction readings will be greater than 20 dB, plotted below the 20 dB line on the chart. In conductive hearing loss, sound can travel through bones but is not conducted through air due to pathology along the route into the ear.
In patients with mixed hearing loss, both air and bone conduction readings will be more than 20 dB, however there will be a difference of more than 15 dB between the two (bone conduction > air conduction).
Establishing the diagnosis is the first step. After the diagnosis is established, input from the multidisciplinary team is required for support with hearing, speech, language and learning:
- Speech and language therapy
- Educational psychology
- ENT specialist
- Hearing aids for children who retain some hearing
- Sign language
Last updated January 2020