Hearing loss

AGE Risk factors depend on the cause	GENDER Risk factors depend on the cause
LIFESTYLE Risk factors depend on the cause	GENETICS Risk factors depend on the cause

Hearing loss is partial or total loss of hearing in one or both ears.

What are the types of hearing loss?

Partial or total hearing impairment can severely restrict social interaction, leading to isolation and depression. Hearing loss may result from disease or injury, and most people experience deterioration of hearing with age (see Presbyacusis). Hearing defects may also be present from birth; about 2 in every 1,000 babies are born with some degree of hearing impairment (see Congenital deafness).

What are the types of hearing loss?

There are two types of hearing loss: conductive and sensorineural. Conductive hearing loss is caused by a failure of the outer or middle ear to transmit sound to the inner ear, and is often temporary. Sensorineural hearing loss, is usually permanent, and may be caused by disorders of the cochlea (the part of the inner ear that detects sound), the vestibulocochlear nerve (which connects the inner ear to the brain), or parts of the brain involved with hearing.

Conductive hearing loss

The most common cause of conductive hearing loss in children is chronic secretory otitis media, in which the middle ear fills with fluid following an infection. In adults, the condition is often due to blockage of the ear canal (see Wax blockage). It can also result from a ruptured eardrum, or sudden changes in air pressure (see Barotrauma). Rarely, the condition is due to otosclerosis, in which one of the tiny bones in the middle ear is immobilized and cannot transmit sound.

Sensorineural hearing loss

This type of hearing loss is commonly due to deterioration of the cochlea with age and mostly affects people over 70. The condition may also result from damage to the cochlea by excessive noise (see Noise-induced hearing loss) or by the inner-ear disorder Ménière's disease. Rarely, hearing loss is caused by a tumour that affects part of the brain or the vestibulocochlear nerve (see Acoustic neuroma). Certain drugs, including antibiotics such as gentamicin and chemotherapeutic agents such as cisplatin, can be toxic to the inner ear, resulting in hearing loss.

What might be done?

Your doctor will examine your ear with a viewing instrument called an otoscope (see Otoscopy). Hearing tests may then be performed to establish the type and degree of hearing loss. If a tumour of the vestibulo-cochlear nerve is suspected, your doctor may arrange for an examination of the nerve using MRI.

If you have conductive hearing loss, treatment of the underlying cause may restore your hearing to near normal. Sensorineural hearing loss is often permanent, although a hearing aid may be helpful. In cases of profound sensorineural deafness, a cochlear implant, in which electrodes are surgically implanted in the cochlea, may allow hearing of sounds such as speech.

Posted 09.09.2010

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