Causes of hearing loss

Hearing loss can be conductive, sensorineural or mixed. Conductive and sensori-neural hearing loss can occur together or separately in one or both ears.

Conductive hearing loss

Conductive hearing loss results from interference with the passage of sound through the external and middle ear to the inner ear.

Some common causes of conductive hearing loss include:

• Blockage in the external canal, e.g. by wax or a foreign body
• Perforation of the tympanic membrane
• Fluid in the middle ear e.g. as a result of infection, or due to blockage of the Eustachian tube (Otitis Media with effusion (OME)
• Damage to the ossicles e.g. due to trauma, otosclerosis

Many of the causes of conductive hearing loss can be corrected by treatment.

Sensorineural hearing loss

Sensorineural hearing loss results from disorders of the cochlea (the cochlea is in the inner ear) or the auditory nerve and its central connections.

Causes of sensorineural hearing loss can be divided into two groups:

Congenital deafness

Congenital deafness may present at birth and it is the aim of newborn hearing screening to identify these babies at an early age. Some congenital conditions may not become evident until the child is older.

During the pre and perinatal periods babies are subjected to various factors, which can affect their hearing, for example, infections such as mumps, meningitis, cytomegalovirus and rubella.

Acquired deafness

Similarly in adults other causes include:

• Exposure to sustained or sudden loud noise
• Ménières disease
• Toxic reactions to medication
• Trauma such as a severe head injury
• Tumours

Age related hearing loss (Presbycusis)

It first affects the highest pitches or frequencies. This means that many of the consonants such as the letters “F”, “S” “T” and the sound “SH” are not heard properly. This affects conversation and understanding of what is said on the telephone.

Sensorineural hearing loss is usually permanent. People with severe to profound hearing loss may derive benefit from cochlear implantation.

Amended February 2009