Saturday, February 25, 2012

Types and Causes of Age-related Hearing Problems


Main Causes

The most common form of hearing loss associated with ageing results from degeneration of a part of the inner ear which contains micropscopic blood vessels. Tiny hairs inside your ear help you hear. They pick up sound waves and change them into the nerve signals that the brain interprets as sound. Hearing loss occurs when the tiny hairs inside the ear are damaged or die. The hair cells do not regrow, so most hearing loss is permanent.

This type of hearing loss does not disproportionately affect the individual's ability to hear and understand speech. However, other changes within the inner ear associated with ageing, including the loss of the ear's tiny 'hair' cells, can have a more serious affect on the ability to understand speech.

Vital components of speech sounds, usually the higher pitched consonants, which give intelligibility to speech, are missing or distorted and, for this reason, many people first experience difficulty in understanding women and children - the lower pitched male voices often being easier for them to hear and comprehend. As hearing deteriorates the ability to understand speech becomes more severely affected.

There is no known single cause for age-related hearing loss. Most commonly, it is caused by changes in the inner ear that occur as you grow older. However, your genes and loud noises (such as from rock concerts or music headphones) may play a large role.

The following factors contribute to age-related hearing loss:
  • Family history (age-related hearing loss tends to run in families)
  • Repeated exposure to loud noises
  • Smoking (smokers are more likely to have such hearing loss than nonsmokers)

Certain medical conditions and medications also contribute to age-related hearing loss. About half of all people over age 75 have some amount of age-related hearing loss.

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Main Types of Hearing Problems

There are basically two types of hearing problems. One is caused by problems with the sound reaching the inner ear. Since the sound travels there via conduction, this is called conductive hearing loss.  It's the far less common mechanism of hearing loss.

Examples of causes include infection (otitis media), wax, “glue ear” where fluid collects in the middle ear, a perforated eardrum and otosclerosis – a condition caused by progressive hardening of the tiny bones in the middle ear that are crucial for hearing.

Much more common is sensorineural hearing loss. This is often called nerve deafness, but this is a misnomer, because the auditory nerve is almost never the cause. The problem is usually in the hair cells of the cochlea. One of the most devastating and mysterious forms of sensorineural hearing loss is sudden hearing loss or sudden deafness!

So what causes sensorineural hearing loss? Well, lots of things, many of which we can't do much about. Prebyacusis is the most common cause but others include injury, infection (such as mumps or meningitis), Meniere's disease, loud noise, neurological conditions such as multiple sclerosis or stroke, and benign tumours affecting the auditory nerve known as acoustic neuromas.

One big thing that we can control is noise. Noise is the enemy of hearing, and people are discovering that it doesn't take as much noise as previously thought to cause temporary or permanent hearing loss.

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Medications and Hearing Loss

More than 100 prescription and over-the-counter drugs have been identified as ototoxic, or damaging to the ear and hearing. Sometimes these drugs are necessary for treating a life-threatening illness and no other recourse is available. Other times, for various reasons, individuals take too much of a medication over a period of time. Among the drugs identified as causes of hearing loss/deafness are:
  • Certain drugs for pain relief have been associated with permanent hearing loss, especially when taken at high doses over a long period of time. Check with your doctor or pharmacist.
  • Strong antibiotics such as streptomycin and gentamycin are used to treat bacterial infections. These drugs can cause hearing loss (or deafness). These types of aminoglycoside drugs should be strictly monitored by a physician, and a baseline hearing test should be performed before and after any of these drugs are given.
  • Drugs used in chemotherapy, called cytotoxic drugs, destroy cells or prevent their growth to control cancer. Chemotherapy patients who experience tinnitus or difficulty hearing should let their physician know immediately.
  • "Water pills," or loop diuretics, are used to increase urine output for patients with certain heart problems. They can be ototoxic when administered in large doses (usually intravenously).
  • Aspirin and other salicylates, and anti-inflammatories such as ibuprofen can cause temporary hearing loss when taken in high doses and are known be a cause of tinnitus (ringing ears).

Infection-Caused Hearing Loss

Young children aged six and under often experience a condition of the middle ear called otitis media. Because the eustachian tube, the tube that connects the middle ear and throat, is more horizontal and shorter in younger children, it is more prone to infection from microorganisms that enter the ear. Symptoms of otitis media include pain in the ear, buzzing or ringing ears, a full or plugged feeling and related hearing loss, fever, and sometimes discharge from the ear. If left untreated, chronic otitis media can lead to permanent hearing loss and/or speech and language delays in children.

More common to adults is external otitis, or infection of the outer ear. Sometimes called swimmer's ear, it can be caused by bacteria, fungus, eczema or seborrhea, allergies, swimming or scuba diving, and chronic irritation from ear pulling or scratching (with a Q-tip, for example). Its symptoms include ear pain, itching, ringing ears (it is often identified as a cause of tinnitus), and, when the infection becomes more serious, fever, swelling, discharge, and diminishment of hearing. Otitis media and external otitis should be treated by a physician. The physician will likely prescribe ear drops and an antibiotic and caution the patient to keep the ear as dry as possible.

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Hearing Loss Resulting from Trauma

Trauma-related hearing loss can result from several causes, from loud sounds to a blow to the head. Acoustic trauma often occurs in individuals exposed to loud sound over a long period of time, such as heavy equipment operators or airport workers. However, hearing loss also can result when a sudden loud noise such as an explosion, airbag discharge, or gunshot damages structures in the ear. This type of hearing loss, which usually affects perception of high frequency sound, can be a cause of tinnitus (ringing ears) and may become progressively worse over time.

Those who suffer a head injury are particularly prone to hearing loss. Damage can occur to structures in the ear, the neural pathways that carry sound to the brain, and the hearing centers of the brain. Such trauma can be a cause of tinnitus, sudden hearing loss, progressive hearing loss, and can even be one of the causes of deafness.

Tinnitus – Unpleasant Ringing Ears

Tinnitus is a high-pitched ringing or other sound in the ears that others cannot hear. Rather than being one of the causes of hearing loss, it most commonly occurs as the result of hearing loss. Presbycusis, medications, disease, and trauma have all been linked to ringing ears. The internal cause of tinnitus is thought to be damage to the cochlea, the snail-shaped bony structure of the inner ear responsible for hearing. The cochlea contains fine hairs that respond to sound stimulus and send signals to the brain. It is theorized that when these hairs or another portion of the cochlea becomes damaged, the brain compensates by creating its own noise—tinnitus.

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Balance Problems

A balance problem causes a person to feel unsteady on the feet and to be prone to episodes of dizziness or vertigo. A person's balance is largely regulated by the inner-ear structure called the vestibular system. This intricate system works in concert with other sensory organs to maintain the body's position. Factors such as infection, head trauma, circulatory disorders, medications, and aging can all affect the vestibular system and cause a balance disorder. Symptoms often include a sensation of falling, dizziness, vertigo ("room spinning"), blurred vision, and disorientation.

Balance problems can also occur as the result of an acoustic neuroma, a noncancerous tumor that grows on the nerve that goes from the inner ear to the brain. Because it develops on or near the vestibular system, it can affect equilibrium as well as cause hearing loss.

The neurological effects of a vitamin B12 deficiency can cause unsteadiness or loss of balance. This condition is most often seen in patients over 75 years old.

Dizziness / Vertigo

Dizziness (lightheadedness) and vertigo (a spinning sensation) are often related to inner ear disturbances. One of the most common causes of dizziness and vertigo is benign paroxysmal positional vertigo (BPPV). BPPV is the intense feeling of dizziness and vertigo that accompanies a sudden change of head position. Causes of BPPV are thought to include infection, aging, head injury, and the development of calcium carbonate in the inner ear structures, a condition technically known as otoconia. The chance of experiencing BPPV increases with age. It is estimated that 50 percent of dizziness in older people is a result of BPPV. In fact, most elderly people who have problems with dizziness and vertigo have an otologic (ear-related) disturbance. Repositioning therapy can be used to treat BPPV, and some patients benefit from vestibular rehabilitation therapy, a regimen of individualized exercises designed to reduce dizziness and alleviate balance problems.

Other causes of dizziness and vertigo include Meniere's Disease and neurological disorders. A condition that most often affects young adults but may also occur in younger and older individuals is viral labyrinthitis. Often developing after a cold or a bout of the flu, viral labyrinthitis causes sudden and severe dizziness and vertigo, often resulting in nausea and vomiting. The condition is thought to be caused by a viral infection of the labyrinth, a structure of the inner ear's vestibular system. Viral labyrinthitis can be treated with drugs, but it usually disappears without treatment.


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