Causes of Hearing Loss
Ten percent of Canadians have a hearing loss. It may be present at birth or begin at any age. There are varying degrees. There are two main types.
- Conductive - loss occurs in the outer and middle ear.
- Sensorineural - or nerve deafness occurs in the inner ear or cochlea.
Conductive Loss
The main causes of conductive loss are:
- Acute Otitis Media
- Most common in children but can occur at any age. It is caused by infection in the middle ear. Symptoms include fever, irritability and pain. Antibiotics will clear the infection and quickly relieve the symptoms. It is important that the child be seen by a doctor, other wise serious infection will develop and permanent damage may occur.
- Secretory Otitis Media
- Often referred to as glue ear or fluid in the ear. This may occur if the narrow Eustachian tube gets blocked. Air in the middle ear is replaced by fluid, and sound will not be heard as well as usual. There may be no symptoms, or slight discomfort, but the fluid can become infected as in acute otitis media. The ear, nose, and throat (ENT) specialist may not treat it immediately, as it often clears up by it self. He may place little tubes through the ear drums to drain the fluid. This is done under a general anaesthetic.
- Otosclerosis
- A hereditary problem which usually begins to cause hearing loss in early to middle adult life. New bone grows around the stapes and affixes itself in the oval window, so that it cannot vibrate properly and the hearing impairment progresses gradually. In some cases the cochlea becomes involved, so that sensorineural loss is added to the conductive loss. This is more likely to happen if it is left untreated. Modern surgical treatment is usually effective in restoring good hearing provided the cochlea is not damaged. The stapes is removed and replaced by a plastic prop.
Other causes of conductive loss may be:
- Impacted Wax
- Foreign Objects – children love to push beads and buttons in their ears.
- Otitis Externa – a swelling of the lining of the ear canal due to infection and eczema.
- Malformation – of the external part of the ear or the canal.
- Ruptured Eardrum – may be caused by trauma to the ear, change in air pressure as often occurs in diving accidents.
Many conditions that cause conductive loss can be prevented. Most can be treated and many corrected either by medication or surgery. Hearing aids, if needed, give good results as sound will not be distorted because the inner ear is normal.
Sensorineural Hearing Loss
The main causes of sensorineural hearing loss are:
Present at Birth
- Congenital
- Congenital hearing loss which occurs at birth may be caused by genetic disorders or it may happen as a result of a difficult labor and delivery. A child may also be born with a hearing impairment if the mother had been exposed to viral infections or had been taking certain medications during pregnancy.
- Genetic
- Present at birth and caused by hereditary factors. Genes for hearing loss may be acquired from one or both parents.
- Infection in the mother during pregnancy
- There are several prenatal viral infections which can cause hearing loss in a new born child. They include rubella (german measles), rubeola (common measles), and influenza.
- Premature Birth
- Puts babies at a risk.
- Lack of oxygen during delivery.
Acquired After Birth
- Infections
- eg. mumps, meningitis.
- Noise
- Excessive or exposure to noise over a long period of time.
- Head Injury
- A severe blow to the head, sudden change in pressure, brain hemorrhage or stroke can all cause sensorineural hearing loss.
- Presbycusis
- The gradual deterioration associated with aging.
- Tumor
- An acoustic nerve tumor.
- Cochlear Otosclerosis Oxotoxicity
- A number of drugs can cause hearing loss and distur bance in balance. The loss may be temporary or permanent especially if taken in high dosages over a long period of time.
The following are some of the most commonly used drugs which can be implicated:
- Amino glycoside
- Antibiotics
- Streptomycin
- Neomycin
- Kanamycin
- Gentamicin
- Tobramycin
- Amikacin
- Netilmicin
- Other Antibiotics
- Vanocomycin
- Polymyxins
- Colistin
- Erythomycin
- Minocycline
- Loop Diuretics
- Ethacrynic Acid
- Furosemide
- Other Drugs
- Quinine
- Quinidine
- Salicylate - (aspirin)
- Cisplatin