hearing loss



Partial or total inability to hear. In conduction deafness, the passage of sound vibrations through the ear is interrupted. The obstacle may be earwax, a ruptured eardrum, or stapes fixation, which prevents the stapes bone from transmitting sound vibrations to the inner ear. In sensorineural deafness, a defect in the sensory cells of the inner ear (e.g., injury by excessive noise) or in the vestibulocochlear or eighth cranial nerves prevents the transmission of sound impulses to the auditory centre in the brain. Some deaf people are helped by hearing aids or cochlear implants; others can learn to communicate with sign language and/or lip reading.

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Conductive hearing loss happens when there is a problem conducting sound waves through the outer ear, tympanic membrane (eardrum) or middle ear (ossicles). This type of hearing loss may occur in conjunction with sensorineural hearing loss or alone.

Causes of conductive hearing loss

External ear



  • Foreign body in the external auditory canal
  • Exostoses
  • Tumour of the of canal
  • Congenital atresia

Middle ear



Inner ear


Differentiating conductive and sensorineuronal hearing loss

When a Weber test is carried out, sound localizes to the ear affected by the conductive loss. A Rinne test, in which air conduction is normally greater than bone conduction, is usually negative (abnormal), and shows higher greater bone conduction than air conduction.

Table 1. A table comparing sensorineural hearing loss to conductive

Criteria Sensorineural hearing loss Conductive hearing loss
Anatomical Site Inner ear, cranial nerve VIII, or central processing centers Middle ear (ossicular chain), tympanic membrane, or external ear
Weber Test Sound localizes to normal ear Sound localizes to affected ear (ear with conductive loss)
Rinne Test Positive Rinne; Air conduction > Bone conduction (both air and bone conduction are decreased equally, but the difference between them is unchanged). Negative Rinne; Bone Conduction > Air Conduction (Bone/Air Gap)

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