Learn more about what it is, what causes it and how it can be treated
Hearing loss is categorised according to the part of the auditory system that is damaged. There are three categories of hearing loss: conductive hearing loss, sensori-neural hearing loss and mixed hearing loss.
Sensori-neural hearing loss (SNHL) is the most common type of hearing loss. It is a result of damage to the hair cells in the cochlea of the inner ear, or to the auditory nerve (VIIIth) (retrocochlear) to the brain. Sensori-neural hearing loss, in most cases, cannot be medically or surgically corrected, it is a permanent loss.
What are the symptoms?
SNHL not only involves a decline in sounds heard, or the ability to hear faint sounds, but also affects the understanding of speech and the ability to hear clearly.
How is it diagnosed?
To determine if a patient is suffering from SNHL, an audiologist will conduct a hearing test using an audiometer. The process of testing a person’s hearing is called audiometry. Two rows of thresholds are obtained during a pure tone hearing test:
- bone conduction thresholds test the status of the cochlea/inner ear and is usually the top row
- air conduction thresholds show functional hearing (through the ear canal and middle ear)
The audiologist will cross-check her/his results by also performing speech audiometry. This often reveals important information with regards to a possible hearing loss and helps to confirm pure tone audiometry results.
When there is a gap between the two rows, it is called an air-bone gap. This means that there is a middle ear problem which is causing a problem with getting the sound to the cochlea. A sensori-neural hearing loss does not have an air-bone gap since only the inner ear structures are affected. A mixed hearing loss affects both the inner- and middle ear and will have an air-bone gap present.
What causes SNHL?
-The natural aging process and simple nerve degeneration. (presbyacusis)
-Head trauma or abrupt changes in pressure. (i.e. diving)
-Excessive or high impact noise exposure like loud music, machinery, an explosion or gun fire.
-Infections like measles, mumps, severe middle ear infections or meningitis.
-Medication prescribed for certain illnesses, such as cardiac conditions, anti-malarial medication, and certain antibiotics.
-Tumours sitting on or close to the auditory nerve may cause hearing loss
-Viral Labyrinthitis or loss of blood flow to the ear.
-Balance disorders such as Menieres (Ménière’s) disease, if it is accompanied by symptoms such as vertigo, nausea and tinnitus.
-Genetic causes, as a result of a physical irregularity or caused by some form of birth injury.
How is it treated?
Treatment is dependent on the cause of SNHL. In most cases there is little that can be done medically. Sufferers mostly opt for a hearing aid or cochlear implants. For a SNHL in one ear, a Baha® implant may also be a good solution. In instances where SNHL is caused by a disease or trauma, medical intervention may help to reverse SNHL.