What is hearing impairment?
There is great importance in early detection of hearing impairment and in providing the best amplification from the youngest age.
For this we must take into account the unique characteristics of preschool children. We see parents as active and significant partners in the process.
The structure and function of the ear (see picture):
- The external ear – includes the auricle, the external auditory canal and the eardrum. The outer ear concentrates the sound waves and transfers them to the eardrum. The eardrum vibrates according to the sound wave, and transmits the sound to the middle ear.
- The middle ear. The middle ear is also called the tympanic cavity or tympanum.
The main function of the middle ear is to carry sound waves from the outer ear to the inner ear, which contains the cochlea and where sound input can be communicated to the brain. Sound waves are funneled into the outer ear and strike the tympanic membrane, causing it to vibrate.
These vibrations are carried through the three ossicles, and the stapes strike the oval window, which separates the middle ear from the inner ear. When the oval window is hit, it causes waves in the fluid inside the inner ear and sets into motion a chain of events leading to the interpretation of sound as we know it.
- The inner ear – also called a cochlea because of its shape. The inner ear is filled with fluid. The inner ear has two special jobs. It changes sound waves to electrical signals (nerve impulses). This allows the brain to hear and understand sounds. The inner ear is also important for balance.
The inner ear is also called the internal ear, auris interna, and the labyrinth of the ear.
Types of hearing impairment:
The hearing mechanism is a very delicate and complex mechanism. Any injury, even the smallest, in any of the stages can cause hearing impairment. Hearing impairments are usually divided according to their location:
- Conductive hearing loss (conductive) – is created as a result of sound attenuation on its way from the outer ear to the inner ear. A conductive defect can arise as a result of blockage or destruction of the anatomical structure in the outer ear, the eardrum or the middle ear. Such a blockage causes the vibration of the eardrum and/or the ossicles to weaken. The common causes of conductive hearing loss include wax accumulation in the outer ear, otitis media (acute or chronic as “fluids” in the ears), or a structural defect. Most progressive defects can be partially or fully treated medically (pharmacologically or surgically). It is not always possible to perform these treatments at an early age. If the progressive hearing impairment persists for a long time, it is recommended to use hearing aids.
- Sensory-neural/sensory-neural hearing loss (sensory neural) – occurs as a result of damage to the structure or function of the hair cells in the inner ear or damage to the passage of nerve stimulation from the inner ear to the brain. Sensory-neural impairment is usually not curable with medication or surgery. The sensory-neural impairment can be congenital or acquired. In these cases, it is recommended to give amplification with the help of hearing aids or a cochlear implant (depending on the severity of the impairment).
- Mixed hearing loss (mixed hearing loss) – includes a conductive component and a sensorineural component.
Assessment of auditory function:
The evaluation of auditory function is done through a hearing test. In the hearing test, the hearing threshold – the weakest intensity that the subject recognizes – is tested. Babies and young children usually perform the test in an “open field”, through the loudspeakers in the test room (sealed room). At a later stage, it is customary to isolate and test each ear separately with the help of regular headphones or headphones.
The findings of the behavioral test are recorded in a chart called an “audiogram”.