Hypoacusis: definition, symptoms, causes, diagnosis and treatment

When there is a partial or complete loss of hearing in one or both ears (unilateral or bilateral), we speak of ‘hearing loss’ or hypoacusis

Some people are born with a hearing impairment, which is known in medical jargon as congenital hearing loss, which can also be caused by problems related to pregnancy (e.g. an infection contracted by the mother-to-be and transmitted to the foetus) or childbirth, while others may develop it with advancing age (presbyacusis) or as a consequence of illness or physical trauma.

Heredity and chronic exposure to loud noises are the main causes that can lead to permanent hearing loss or weakening over time.

There are other factors, such as the presence of a plug of earwax or foreign bodies in the ear canal, can prevent normal perception of sounds, but these are, of course, transient.

The different types of hypoacusis

Depending on the anatomical site involved, the different types of hearing loss can be grouped into two categories:

  • transmission hearing loss, where the loss of hearing ability is caused by problems in the outer or middle ear (ear canal, eardrum) that hinder the transmission of sound to the inner ear;
  • sensorineural hearing loss, where the hearing loss is caused by the inability to transform sounds into nerve impulses (a process that occurs in the inner ear) or to transmit impulses from the ear to the brain, due to lesions or pathologies of the auditory nerve or nervous system.

When there are both problems with the sound transmission system and neurological problems, we speak of a mixed hearing loss.

Levels of hearing loss

Hearing loss can be mild, moderate, severe or profound.

Through certain hearing tests, the level of hearing loss in a person can be determined.

With these tests, hearing is measured in decibels (dB), down to the lowest level that the patient is able to hear.

Some ear disorders, such as tinnitus, do not necessarily cause hearing loss.

The different levels of hypoacusis are listed below:

  • Mild hearing loss (hearing deficit between 25 and 39 dB). Mild hearing loss can make it difficult to follow speech, especially in noisy contexts;
  • moderate hearing loss (hearing loss between 40 and 69 dB). In this case, the patient may have difficulty following speech without using a hearing aid;
  • severe hearing loss (hearing deficit between 70 and 89 dB). People who are severely deaf usually need to use some form of alternative communication, such as reading lips or learning sign language, even with the use of a hearing aid;
  • deafness or profound hearing loss (hearing impairment >90 dB).

Individuals who are unable to hear sound can often benefit from a cochlear implant.

Symptoms of hearing loss

Hearing loss can occur as early as birth or develop later in childhood or adulthood.

Hearing loss may therefore develop gradually over time, particularly due to factors associated with noise exposure and age.

If there is a hearing loss that starts quickly, there are different causes: a trivial earwax plug, infections or diseases in the middle or inner ear such as sudden hearing loss.

Thus, as can be deduced from the above, the symptoms of a hearing loss can be very varied, starting with:

  • sounds are muffled;
  • difficulty understanding words and following conversations, especially when there is background noise or one is in a crowd of people;
  • one often asks others to speak more slowly, clearly and loudly;
  • one feels the need to turn up the volume of the television or radio;
  • pressure in the ear (due to an alteration of the fluid behind the eardrum);
  • dizziness or lack of balance;
  • continuous ringing in the ears, also known as tinnitus.

Symptoms in children

From birth, babies are regularly screened within the first few weeks after birth as part of the Newborn Hearing Screening Programme (NHSP).

But it can also happen, unfortunately, that certain signs lead to the suggestion of further hearing evaluation, for instance if it is noticed that the child

  • by the age of four months, does not spontaneously turn towards a sound source;
  • is not frightened by loud noises
  • manifests a delay in learning to pronounce the first words or these are not clear when speaking.

The causes of hearing loss

The factors that lead to hearing loss can be various, starting with:

  • diseases of the outer ear (otitis, earwax, exostosis, etc.);
  • middle ear diseases (otitis, otosclerosis,…..);
  • inner ear diseases (sudden hearing loss, Meniere’s syndrome);
  • congenital diseases;
  • causes linked to the use of ototoxic drugs;
  • environmental factors from chronic damage due to noise exposure.

Apart from these causes, hearing loss can also be a natural consequence of ageing (in this case we speak of presbyacusis). Of course, hearing loss can also be linked to genetic factors, malformations and trauma involving the auditory system or the brain.

Acoustic trauma

We also speak of acoustic trauma when damage to the ear is caused by excessively loud noises.

This phenomenon can occur when part of the delicate inner structure of the ear is damaged due to prolonged exposure to loud noises.

In this case, the hair cells of the cochlea become inflamed and wear out.

The sound level of noise and the duration of exposure are important factors in determining noise trauma.

Some people are more exposed to this type of risk than others, and these are

  • those who work with equipment that produces excessive noise, such as pneumatic hammers or particular tools and machines used in construction, agriculture or factory work. When exposure to very loud noise is a normal part of the working environment, the risk of developing a hearing impairment or damage to hearing is greater. Sudden and intense explosions, such as those caused by fireworks or weapons, can also damage hearing immediately and permanently;
  • those who work in environments where there is always loud music, such as staff at a nightclub;
  • those who listen to loud music with earphones.

However, there are many other conditions that can cause hearing loss, such as infectious diseases such as meningitis, measles, rubella and mumps, multiple sclerosis, Ménière’s syndrome, benign and malignant tumours.

Hearing loss can also be caused by the use of certain ototoxic drugs (antibiotics, chemotherapeutics, etc.), i.e. drugs that can cause damage.

How to treat hypoacusis

When even partial hearing loss is experienced, it is a good idea to contact the attending physician or an ENT specialist to investigate the cause and severity of the hearing condition.

In addition to an assessment of the ear with an otoscope (an instrument that allows the ear canal and eardrum to be observed), further tests may be required to assess the origin of the problem and an audiometric test to ascertain the extent of the hearing deficit and possibly a speech audiometry to assess the ability to discriminate words.

The treatment of hearing loss depends on the underlying causes. In some cases, the problem is resolved trivially by eliminating the earwax plug or the accumulation of fluid (intra-tympanic insufflations), in others with targeted drug therapy, and in others still with surgery.

For some types of hearing loss, such as presbyacusis, hearing aids can be used.

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