QS Study

Deafness

It is a clinical condition characterized by partial or complete loss of ability to hear, is known as deafness. This occurs when a person cannot understand speech through hearing, even when sound is amplified.

Some diseases or circumstances that can cause deafness include: chickenpox, cytomegalovirus, mumps, meningitis, syphilis, Lyme disease, diabetes, hypothyroidism, arthritis etc.

It is two types – a) Conduction deafness; b) Nerve deafness.

(a) Conduction deafness – Deafness resulting from impaired sound transmission in the external or middle ear is known as conduction deafness. This means that the vibrations are not passing through from the outer ear to the inner ear, specifically the cochlea.

Causes of conduction deafness:

  • Plugging or blockage of external auditory canals with wax or foreign bodies.
  • Narrowing of the external meatus.
  • Destruction of the auditory ossicles.
  • Thickening of the tympanic membrane.
  • Exudate in the middle ear.
  • Disease such as meningitis, rheumatism, malaria, syphilis etc.

In conduction, deafness bone conduction is better than ossicular conduction.

(b) Nerve deafness – Deafness due to damage to the hair cells or neural pathways is known as nerve deafness. This kind of hearing loss is normally due to damaged hair cells in the cochlea. As humans grow older, hair cells lose some of their function, and hearing deteriorates.

Causes of nerve deafness:

  • Damage of the eight cranial nerve,
  • Damage to the outer hair cells by prolonged exposure to noise.
  • Drugs (Aminoglycoside antibiotics such as streptomycin and gentamicin).
  • Tumor of the vestibular nerve.
  • Cerebellopontine angle.
  • Vascular damage in the medulla.
  • Disease such as meningitis, rheumatism, malaria, syphilis etc.

In nerve deafness, ossicular conduction is better than bone conduction.

Test for deafness

  • Weber test,
  • Rinne test,
  • Schwabach.

[Presbycusis: The gradual hearing loss associated with aging, affects more than one-third of those over 75 and is probably due to gradual cumulative loss of hair cells and neurons.]