Epidemiology Shingles

Most current estimates of the epidemiology and burden of herpes zoster and PHN come from studies in Europe and the USA. The reported incidence of herpes zoster in these regions varies from 1.3 to 4.8/1000 patients/year, and this rate increases sharply with age, with a 2- to 4-fold increase in those aged >60 years.

The incidence rate of herpes zoster ranges from 1.2 to 3.4 per 1,000 person-years among healthy individuals, increasing to 3.9–11.8 per 1,000 person‐years among those older than 65 years.Similar incidence rates have been observed worldwide. Herpes zoster develops in an estimated 500,000 Americans each year.

United States

A study of patients in a large health maintenance organization (HMO) in the United States revealed 1075 cases from 1990-1992.¹ The following characteristics were noted:

• Incidence was 215 cases per 100,000 people per year.
• Older patients were more at risk (1424 cases per 100,000 people per year for age >75 y).
• Fewer than 5% of cases were in children and younger adolescents.
• Three of 4 patients with recurrent zoster were HIV positive.

Over 90 percent of adults in the United States have serologic evidence of varicella–zoster virus infection and are at risk for herpes zoster.² The annualized incidence of herpes zoster is about 1.5 to 3.0 cases per 1000 persons.^3,4 An incidence of 2.0 cases per 1000 persons would translate into more than 500,000 cases annually in the United States. Increasing age is a key risk factor for the development of herpes zoster; the incidence of shingles among persons older than 75 years of age exceeds 10 cases per 1000 person-years.³ The lifetime risk of herpes zoster is estimated to be 10 to 20 percent.⁴

Resource on Pain Treatment

http://www.painfoundation.org/learn/publications/files/TreatmentOptions2006.pdf

What is Shingles

Shingles is an infection of a nerve and the area of skin supplied by the nerve. It is caused by a virus called the varicella-zoster virus. It is the same virus that causes chickenpox. Anyone who has had chickenpox in the past may develop shingles. Shingles is sometimes called herpes zoster. (Note: this is very different to genital herpes which is caused by a different virus called herpes simplex.)

About 1 in 5 people have shingles at some time in their life. It can occur at any age, but it is most common in people over the age of 50. It is uncommon to have shingles more than once, but about 1 in 50 people have shingles two or more times in their life.

Most people have chickenpox at some stage (usually as a child). The virus does not completely go after you have chickenpox. Some virus particles remain inactive in the nerve roots next to your spinal cord. They do no harm there, and cause no symptoms. For reasons that are not clear, the virus may begin to multiply again (reactivate). This is often years later. The 're-activated' virus travels along the nerve to the skin to cause shingles.

In most cases, an episode of shingles occurs for no apparent reason. Sometimes a period of stress or illness seems to trigger it. A minor 'ageing' of the immune system may account for it being more common in older people. (The immune system keeps the virus inactive and prevents it from multiplying. A slight weakening of the immune system in older people may account for the virus 'reactivating' and multiplying to cause shingles.)

Shingles is also more common in people with a poor immune system. For example, shingles commonly occurs in younger people who have HIV/AIDS or whose immune system is suppressed with treatment such as steroids or chemotherapy.

Treatment of Shingles

Complementary Treatment for Shingles *addition*

THE ORTHODOX APPROACH

If the complaint is caught early enough and treatment starts within say 24 hours of the rash appearing, antiviral drugs will reduce the duration of the illness and lessen the risk of post-herpetic neuralgia. Strong pain-killers may also be prescribed. If shingles affects the forehead, the physician will examine your eyes to make sure that the cornea has not been harmed (sight can be damaged if treatment comes too late), and special eye drops will be prescribed to protect the eyesight. It is wise to wear loose fitting clothing so that the blisters are not rubbed and irritated. Cool baths may help relieve the pain.

ACUPUNCTURE

According to the theory of ancient Chinese medicine, shingles is caused by overheating along with viruses and toxins in the body. As one acupuncturist explains, “The principle of treatment is to tackle the overheating, to get through the blockages and to balance the body”.

He estimates that it normally takes about two weeks to clear up shingles. “Acupuncture alone is excellent for shingles and for the accompanying pain”, he says.

HYPNOTHERAPY

Post shingles pain can linger for a long time, often causing depression, and hypnotherapy can be most effective in dealing with this attendant aspect of the disease. When the patient is in a hypnotic state, visualization techniques can be used so that he or she sees the virus being expelled from the body and sees him/herself being well again.

HOMEOPATHY

One homeopath reports that “most cases of shingles show good improvement” using homeopathic remedies. He estimates that three to four consultations are usually adequate to produce results. The best known homeopathic remedies for shingles are Bellis per. and Hedera helix (ivy). Other commonly used remedies include Rhus tox. for the blistered, itchy skin, Apis mel if the skin burns or stings, and Mezereum for extreme pain and itching.

NATUROPATHY

There are dietary factors that are known to help or hinder the development of this painful disease. Specifically, there are two amino acids, lysine and arginine, which have an antagonistic effect on each other – arginine promotes herpes and lysine suppresses it. Therefore, foods rich in arginine and low in lysine are to be avoided. These include peanuts and other nuts, chocolate, various seeds (sunflower, poppy, and sesame), cereal grains (bread, breakfast cereals), raisins, gelatin and carob. Instead, choose foods which have a higher ratio of lysine to arginine, such as eggs, beans, fish, chicken, meat, potatoes, milk, and brewers’ yeast. One naturopath recommends that you drink red bush (Rooibosch) tea, which contains a bioflavonoid called quercetin that is useful in combating the herpes virus. In addition, aloe vera and liquorice can be taken internally and/or applied topically to help the rash.

Finally, for local, topical application, he recommends two treatments. Firstly, propolis, which has a “tremendous anti-viral effect”; and secondly lithium, an element found to inhibit herpes. It can be used in the form of an ointment containing lithium succinate with Vitamin E and zinc. “When applied to the blistered area four times daily, it can reduce the duration of the pain and discomfort considerably, easily by half”, he says.

SUPPORTIVE TREATMENTS

When combined with other remedies, the following therapies can be highly beneficial: the therapeutic properties of a Moor therapy drink or body treatment; the ancient Chinese exercise of Chi Kung, which balances the body’s energies and brings a sense of well-being; and the powerful effects of healing energy.

Anatomy - CNS

CENTRAL NERVOUS SYSTEM (CNS)

SOMATIC PART of CNS
- Carry conscious sensation from peripheral à CNS
- Innervates voluntary muscles
- Dermatomytome (from somites) : skeletal muscles + dermis
o Migrate to
§ ANTERIOR : Hypaxial muscles (limbs & trunk)
§ POSTERIOR : Epaxial muscles (intrinsic back muscles & dermis)
- Developing nerve cells in anterior neural tube (form CNS) à differentiating dermatomytome [ MOTOR neurons]
- Developing nerve cells in the neural crest (form PNS) à a) Medial process à posterior of NT
- à b) Lateral process à differentiating dermatomytomes [ SENSORY neurons]
Organized segmentally along the NT and form parts of all spinal nerves & some cranial nerves


- Sensory infos à POSTERIOR spinal cord Motor infos àAnterior spinal cord
- Peripheral à CNS Somatic Sensory Afferents/ General Somatic Afferents (GPAs)
· Modalities include pain, touch, temperature & proprioception
- CNS à Peripheral Somatic Motor Efferents/ General Somatic Efferents (GSEs)

Dermatomes (sensory)
- Specific somite develops à dermis at a precise location à associated somatic sensory fibres enter à POSTERIOR spinal cord at a specific level becomes à ONE specific spinal nerve
- Thus, EACH spinal nerve carries somatic sensory infos from a specific area of skin on the surface of the body
Area of skin supplied by a SINGLE spinal cord level/spinal nerve

- Dermatome is usually overlap
o Autonomous Region: Overlap of dermatomes is least likely
§ TESTING TOUCH in conscious patient à localize lesions to a specific spinal nerve
Mytomes (motor)
- Specific somite develops à skeletal muscle at a precise location à associated somatic motor fibres ­+ somatic sensory nerves from the SAME level = SPINAL NERVE
Portion of skeletal muscle innervated by a SINGLE spinal cord level/ spinal nerve

- More difficult to test than dermatomes as each skeletal muscle is usually innervated by > 1 spinal nerve
- However, TESTING MOVEMENT at successive joints à localize lesions to specific spinal nerve, e.g. a) shoulder joint (C5 & C6) b) elbow (C6 & C7) c) hand (C8 & T1)

IMPORTANT CLINICAL USE
Fundamental to carry out neurological examination

Risk Factors of Shingles

An Overview of Shingles Risk Factors
Shingles is a condition caused by the varicella-zoster virus, which is the same virus that causes chickenpox. After you recover from chickenpox (or have the chickenpox vaccine), the virus does not leave your body, but continues to live in some nerve cells. For reasons that aren't totally understood, the virus can become active instead of remaining inactive. When it is activated, it produces shingles.
Anyone with the varicella-zoster virus in his or her body can be at risk for getting shingles. Right now there is no way of knowing who will get shingles disease. But, there are things that make you more likely to get shingles. These "shingles risk factors" include:

• Advanced age
• Problems with the immune system
• Chickenpox during pregnancy.

Advanced Age
About 25 percent of all adults, mostly otherwise healthy, will get shingles during their lifetime, usually after age 40. The incidence increases with age. For example, shingles is 10 times more likely to occur in adults over 60 than in children under 10.

Immune System Problems
Your immune system is the part of your body that fights off infections. Age can affect your immune system. So can an HIV infection (or AIDS), cancer, cancer drugs, radiation treatments, or an organ transplant. Even stress or a cold can weaken your immune system for a short time and put you at risk for shingles.

Chickenpox During Pregnancy
Youngsters whose mothers had chickenpox late in pregnancy -- 5 to 21 days before giving birth -- or who had chickenpox in infancy have an increased risk of pediatric shingles. Sometimes these children are born with chickenpox or develop a typical case within a few days.
What Are the Causes of Shingles?
There is only one cause of shingles (also known as herpes zoster) -- a reinfection with the varicella-zoster virus. The varicella-zoster virus that causes shingles is the same virus that causes chickenpox. The infection with this virus just tends to occur during different decades of a person's life.

The Varicella-Zoster Virus - - The "Cause of Shingles"
Varicella-zoster is part of the herpesvirus family. This group of viruses includes the herpes simplex virus (HSV) that causes cold sores, fever blisters, genital herpes (a sexually transmitted disease), and the Epstein-Barr virus involved in infectious mononucleosis.

As early as 1909, a German scientist suspected that the viruses causing chickenpox and shingles were one and the same. In the 1920s and 1930s, the case was strengthened. As part of an experiment, children were inoculated with fluid from the lesions of people with shingles. Within two weeks, about half the children came down with chickenpox. Finally, in 1958, detailed analyses of the viruses taken from people with either chickenpox or shingles confirmed that the viruses were identical.

So how does the same virus that causes chickenpox also cause shingles? To understand this, it may be helpful to understand the "reactivation" of the varicella-zoster virus.

Reactivation of the Shingles Virus Causes Shingles
After an attack of chickenpox, the varicella-zoster virus moves up into the nerves, where it settles down in an inactive form (known as a latent form). It "lies down" inside specific nerve cells (neurons) that relay information to the brain about what your body is sensing -- such as whether your skin feels hot or cold, whether you've been touched, or whether you're feeling feel pain. These nerve cells lie in clusters (ganglia) adjacent to the spinal cord and brain, and are one type of sensory neuron.

As we get older, it is possible for the varicella-zoster virus to "come alive." When this happens, the shingle virus "reactivates" and then moves down the nerves to cause symptoms of shingles. Research scientists are still trying to understand why this happens and why it happens in some people and not in others.

Although shingles is most common in people over age 50, if you have had chickenpox or the chickenpox vaccine, you are at risk for developing shingles. This disease is also more common in people with weakened immune systems from HIV infection, chemotherapy or radiation treatment, transplant operations, and stress.

Mnemonic Fun

http://www.medicalmnemonics.com/pdf/2002_09_full_unabr_a4.pdf

Came across this huge list of mnemonics while deliberately trying to avoid the Anatomy textbook.

Utterly irrelevant for what's to come next week, but pretty interesting stuff (I guess?).

Prognosis + Complications of Herpes Zoster

PROGNOSIS

• most healthy people who receive treatment soon after the outbreak of blisters, the lesions heal, the pain subsides within 3 to 5 weeks
  
• The blisters often leave no scars.
  
• a serious threat in immunocompromised individuals
  

COMPLICATIONS

Herpes Zoster Opthalmicus

• Occurs when one of the nerves that go into the eye (known as the ophthalmic nerve) is involved with the shingles infection.
  
• Most common problem is known as anterior uveitis, which is inflammation that normally includes the iris
  
• may cause
  
  • Redness of the eye
    
  • Pain
    
  • Blurred vision.
    
• Up to 70% people with this complication will develop some sort of temporary or permanent eye problem.
  
• May also lead to temporary or permanent blindness.
  

Ramsay Hunt Syndrome

• Occurs when herpes zoster causes facial paralysis and rash on the ear (herpes zoster oticus) or in the mouth.
  
• Symptoms
  
  • Severe ear pain
    
  • Hearing loss
    
    • Varies from partial to total
      
    • May be permanent
      
  • Ringing in the ear
    
  • Loss of taste
    
  • Nausea
    
  • Vomiting
    
  • Dizziness
    
    • May last for a few days or even for weeks
      
    • Usually resolves
      
• May also cause a mild inflammation in the brain
  

Bell's palsy

• Partial paralysis of the face.
  
• May suggest a reactivation of herpes zoster, even if no rash appears.
  

Postherpetic Neuralgia

• Most common severe complication (10%-70%)
  
• Risk factor:
  
  • Age
    
  • Gender
    
  • Severe/ complicated shingles
    
• Pain that persists for longer than a month, sometimes years after the onset of herpes (commonly resolves within 3 months)
  
• Mechanism :
  
  
  • Occurs from damage to the nerve fibers, caused by the varicella zoster virus
    
  • The herpes zoster virus appears to produce persistent inflammation in the spinal cord that causes long-term damage, including nerve scarring.
    
  • Nerves that are injured in the initial attack may regrow abnormally and provoke an exaggerated response in the brain that signals intense sensitivity or pain.
    
• Skin is so sensitive that clothing or even a passing breeze cannot be tolerated on the affected area.
  
• The pain is described as agonizing, excruciating, and burning.
  
• last longer
  
• Difficult to treat
  
• Can result in an inability to perform daily tasks of living. This can lead to loss of independence and, ultimately, depression and isolation.
  

Sacral Zoster

• When the shingles virus affects the nerves that control bladder function
  
• Symptoms can include
  
  • Being unable to urinate
    
  • Feeling the urge to urinate but not being able to
    
  • Having a dribbling urinary stream.
    

Secondary Infection In The Blisters

• If the blistered area is not kept clean and free from irritation
  
• May become infected with Streptococcus A or Staphylococcus bacteria
  
• If the infection is severe, scarring can occur.
  

Disseminated Herpes Zoster

• Spreads to other organs
  
• Can be life-threatening, particularly if it affects the lungs
  
• Immunocompromised person are at greatest danger, with risk of 5 - 25%.
  
• Very rare in people with healthy immune systems.
  

Encephalitis / Meningitis

• A rare complication
  
• Generally mild
  
• Resolves in short period
  
• Can be severe and even life-threatening in immunocompromised person
  

Imminent acute retinal necrosis syndrome

• A devastating infection in the retina
  
• Visual changes develop within weeks or months after the herpes zoster outbreak has resolved
  
• Usually follows a herpes outbreak in the face
  
• Can also occur after an outbreak in any part of the body
  
• Symptoms
  
  • Conjunctivitis
    
  • Inflammation of the cornea
    
  • Pain
    

Treatment of Postherpetic Neuralgia

Treatment of Postherpetic Neuralgia

Analgesics
Capsaicin, an extract from hot chili peppers, is currently the only drug labeled by the U.S. Food and Drug Administration for the treatment of postherpetic neuralgia.19 Trials have shown this drug to be more efficacious than placebo but not necessarily more so than other conventional treatments.20

Substance P, a neuropeptide released from pain fibers in response to trauma, is also released when capsaicin is applied to the skin, producing a burning sensation. Analgesia occurs when substance P is depleted from the nerve fibers. To achieve this response, capsaicin cream must be applied to the affected area three to five times daily. Patients must be counseled about the need to apply capsaicin regularly for continued benefit. They also need to be counseled that their pain will likely increase during the first few days to a week after capsaicin therapy is initiated. Patients should wash their hands thoroughly after applying capsaicin cream in order to prevent inadvertent contact with other areas.

Patches containing lidocaine have also been used to treat postherpetic neuralgia. One study found that compared with no treatment, lidocaine patches reduced pain intensity, with minimal systemic absorption. Although lidocaine was efficacious in relieving pain, the effect was temporary, lasting only four to 12 hours with each application.21

Over-the-counter analgesics such as acetaminophen (e.g., Tylenol) and nonsteroidal anti-inflammatory drugs have not been shown to be highly effective in the treatment of postherpetic neuralgia. However, these agents are often useful for potentiating the pain-relieving effects of narcotics in patients with severe pain. Because of the addictive properties of narcotics, their chronic use is discouraged except in the rare patient who does not adequately respond to other modalities.
Tricyclic antidepressants or anticonvulsant medications given in low dosages can be effective adjuncts in controlling the pain of postherpetic neuralgia.

Tricyclic Antidepressants
Tricyclic antidepressants can be effective adjuncts in reducing the neuropathic pain of postherpetic neuralgia. These agents most likely lessen pain by inhibiting the reuptake of serotonin and norepinephrine neurotransmitters.22

Tricyclic antidepressants commonly used in the treatment of postherpetic neuralgia include amitriptyline (Elavil), nortriptyline (Pamelor), imipramine (Tofranil) and desipramine (Norpramin). These drugs are best tolerated when they are started in a low dosage and given at bedtime. The dosage is increased every two to four weeks to achieve an effective dose.

The tricyclic antidepressants share common side effects, such as sedation, dry mouth, postural hypotension, blurred vision and urinary retention. Nortriptyline and amitriptyline appear to have equal efficacy; however, nortriptyline tends to produce fewer anticholinergic effects and is therefore better tolerated. Treatment with tricyclic antidepressants can occasionally lead to cardiac conduction abnormalities or liver toxicity. The potential for these problems should be considered in elderly patients and patients with cardiac or liver disease.

Because tricyclic antidepressants do not act quickly, a clinical trial of at least three months is required to judge a patient's response. The onset of pain relief using tricyclic antidepressants may be enhanced by beginning treatment early in the course of herpes zoster infection in conjunction with antiviral medications.20

Anticonvulsants
Phenytoin (Dilantin), carbamazepine (Tegretol) and gabapentin (Neurontin) are often used to control neuropathic pain. A recent double-blind, placebo-controlled study showed gabapentin to be effective in treating the pain of postherpetic neuralgia, as well as the often associated sleep disturbance.23

The anticonvulsants appear to be equally effective, and drug selection often involves trial and error. Lack of response to one of these medications does not necessarily portend a poor response to another. The dosages required for analgesia are often lower than those used in the treatment of epilepsy.

Anticonvulsants are associated with a variety of side effects, including sedation, memory disturbances, electrolyte abnormalities, liver toxicity and thrombocytopenia. Side effects may be reduced or eliminated by initiating treatment in a low dosage, which can then be slowly titrated upward.

There are no specific contraindications to using anticonvulsants in combination with antidepressants or analgesics. However, the risk of side effects increases when multiple medications are used.

Effective treatment of postherpetic neuralgia often requires multiple treatment approaches. In addition to medications, modalities to consider include transcutaneous electric nerve stimulation (TENS), biofeedback and nerve blocks.

Corticosteroids
Orally administered corticosteroids are commonly used in the treatment of herpes zoster, even though clinical trials have shown variable results. Prednisone used in conjunction with acyclovir has been shown to reduce the pain associated with herpes zoster.15 The likely mechanism involves decreasing the degree of neuritis caused by active infection and, possibly, decreasing residual damage to affected nerves.

Some studies designed to evaluate the effectiveness of prednisone therapy in preventing postherpetic neuralgia have shown decreased pain at three and 12 months.16,17 Other studies have demonstrated no benefit.15,18

If the use of orally administered prednisone is not contraindicated, adjunctive treatment with this agent is justified on the basis of its effects in reducing pain, despite questionable evidence for its benefits in decreasing the incidence of postherpetic neuralgia. Given the theoretic risk of immunosuppression with corticosteroids, some investigators believe that these agents should be used only in patients more than 50 years of age because they are at greater risk of developing postherpetic neuralgia.15 The recommended dosage for prednisone is given in Table 1.

Analgesics
The pain associated with herpes zoster ranges from mild to excruciating. Patients with mild to moderate pain may respond to over-the-counter analgesics. Patients with more severe pain may require the addition of a narcotic medication. When analgesics are used, with or without a narcotic, a regular dosing schedule results in better pain control and less anxiety than "as-needed" dosing.

Lotions containing calamine (e.g., Caladryl) may be used on open lesions to reduce pain and pruritus. Once the lesions have crusted over, capsaicin cream (Zostrix) may be applied. Topically administered lidocaine (Xylocaine) and nerve blocks have also been reported to be effective in reducing pain.

Signs and Symptoms of Shingles

Early symptoms:
* Sensitivity to light
* Flu-like symptoms without fever

You may then feels symptoms such as:
* Pain, burning, tingling, numbness or extreme sensitivity in a certain part of your body
* A red rash that begins a few days after the pain - the rash will first form blisters, then scab over, and finally clear up over a few weeks.
* Fluid-filled blisters that break open and crust over
* Itching;tingling
* Fever and chills
* Headache
* Upset stomach or abdominal pain
The rash caused by shingles is more painful than itchy.







Typically, the shingles rash occurs on only one side of your body. This is an important sign to help diagnose shingles. It may appear, for example, as a band of blisters that wraps from the middle of your back around one side of your chest to your breastbone, following the path of the nerve where the virus had been inactive. Sometimes, the shingles rash occurs around one eye or on one side of the neck or face.






Pain is usually the first symptom of shingles. For some, it can be intense, with just the slightest touch causing severe pain. Sometimes the pain can be mistaken for other problems or diseases, such as kidney stones, gallstones or appendicitis, depending on its location. Some people experience the pain without the rash, which makes diagnosing shingles more difficult.

Although the shingles rash may resemble chickenpox, the virus typically causes more pain and less itching the second time around.





Shingles develops in stages:

Prodromal stage (before the rash appears)
* Pain, burning, tickling, tingling, and/or numbness occurs in the area around the affected nerves several days or weeks before a rash appears. The discomfort usually occurs on the chest or back, but it may occur on the abdomen, head, face, neck, or one arm or leg.
* Flu-like symptoms (usually without a fever), such as chills, stomachache, or diarrhea, may develop just before or along with the start of the rash.
* Swelling and tenderness of the lymph nodes may occur.

Active stage (rash and blisters appear)
* A band, strip, or small area of rash appears. It can appear anywhere on the body but will be on only one side of the body, the left or right. Blisters will form. Fluid inside the blister is clear at first but may become cloudy after 3 to 4 days. A few people won't get a rash, or the rash will be mild.
* A rash may occur on the forehead, cheek, nose, and around one eye (herpes zoster ophthalmicus), which may threaten your sight unless you get prompt treatment.
* Pain, described as "piercing needles in the skin," may accompany the skin rash.
* Blisters may break open, ooze, and crust over in about 5 days. The rash heals in about 2 to 4 weeks, although some scars may remain.






Postherpetic neuralgia (chronic pain stage)
* Postherpetic neuralgia is the most common complication of shingles. It lasts for at least 30 days and may continue for months to years. Symptoms are:-
o Aching, burning, stabbing pain in the area of the earlier shingles rash.
o Persistent pain that may linger for years.
o Extreme sensitivity to touch.
* The pain associated with postherpetic neuralgia most commonly affects the forehead or chest, and it may make it difficult for the person to eat, sleep, and perform daily activities. It may also lead to depression.

Shingles may be confused with other conditions that cause similar symptoms of rash or pain, such as herpes simplex infection or appendicitis.

http://www.mayoclinic.com/health/shingles/DS00098/DSECTION=symptoms

What is Pain and Types of Pain

The English word 'pain' probably comes from Old French (peine), Latin (poena - meaning punishment pain), or Ancient Greek (poine - a word more related to penalty), or a combination of all three.

In medicine pain relates to a sensation that hurts. If you feel pain it hurts, you feel discomfort, distress and perhaps agony, depending on the severity of it. Pain can be steady and constant, in which case it may be an ache. It might be a throbbing pain - a pulsating pain. The pain could have a pinching sensation, or a stabbing one.

Only the person who is experiencing the pain can describe it properly. Pain is a very individual experience.
Types of pain
Acute pain - this can be intense and short-lived, in which case we call it acute pain. Acute pain may be an indication of an injury. When the injury heals the pain usually goes away.

Chronic pain - this sensation lasts much longer than acute pain. Chronic pain can be mild or intense (severe).

How do we classify pain?

Pain can be nociceptive, non-nociveptive, somatic, visceral, neuropathic, or sympathetic. Look at the table below.

Pain
Nociceptive Nociceptive
1)Somatic 2)Visceral 1)Neuropathic 2)Sympathetic


Nociceptive Pain - specific pain receptors are stimulated. These receptors sense temperature (hot/cold), vibration, stretch, and chemicals released from damaged cells.

Somatic Pain - a type of nociceptive pain. Pain felt on the skin, muscle, joints, bones and ligaments is called somatic pain. The term musculo-skeletal pain means somatic pain. The pain receptors are sensitive to temperature (hot/cold), vibration, and stretch (in the muscles). They are also sensitive to inflammation, as would happen if you cut yourself, sprain something that causes tissue damage. Pain as a result of lack of oxygen, as in ischemic muscle cramps, are a type of nociceptive pain. Somatic pain is generally sharp and well localized - if you touch it or move the affected area the pain will worsen.

Visceral Pain - a type of nociceptive pain. It is felt in the internal organs and main body cavities. The cavities are divided into the thorax (lungs and heart), abdomen (bowels, spleen, liver and kidneys), and the pelvis (ovaries, bladder, and the womb). The pain receptors - nociceptors - sense inflammation, stretch and ischemia (oxygen starvation).

Visceral pain is more difficult to localize than somatic pain. The sensation is more likely to be a vague deep ache. Colicky and cramping sensations are generally types of visceral pain. Visceral pain commonly refers to some type of back pain - pelvic pain generally refers to the lower back, abdominal pain to the mid-back, and thoracic pain to the upper back (see below for the meaning of referred pain).

Nerve Pain or Neuropathic Pain

Nerve pain is also known as neuropathic pain. It is a type of non-nociceptive pain. It comes from within the nervous system itself. People often refer to it as pinched nerve, or trapped nerve. The pain can originate from the nerves between the tissues and the spinal cord (peripheral nervous system) and the nerves between the spinal cord and the brain (central nervous system, or CNS).

Neuropathic pain can be caused by nerve degeneration, as might be the case in a stroke, multiple-sclerosis, or oxygen starvation. It could be due to a trapped nerve, meaning there is pressure on the nerve. A torn or slipped disc will cause nerve inflammation, which will trigger neuropathic pain. Nerve infection, such as shingles, can also cause neuropathic pain.

Pain that comes from the nervous system is called non-nociceptive because there are no specific pain receptors. Nociceptive in this text means responding to pain. When a nerve is injured it becomes unstable and its signaling system becomes muddled and haphazard. The brain interprets these abnormal signals as pain. This randomness can also cause other sensations, such as numbness, pins and needles, tingling, and hypersensitivity to temperature, vibration and touch. The pain can sometimes be unpredictable because of this.

Sympathetic Pain

The sympathetic nervous system controls our blood flow to our skin and muscles, perspiration (sweating) by the skin, and how quickly the peripheral nervous system works.

Sympathetic pain occurs generally after a fracture or a soft tissue injury of the limbs. This pain is non-nociceptive - there are no specific pain receptors. As with neuropathic pain, the nerve is injured, becomes unstable and fires off random, chaotic, abnormal signals to the brain, which interprets them as pain.

Generally with this kind of pain the skin and the area around the injury become extremely sensitive. The pain often becomes so intense that the sufferer daren't use the affected arm or leg. Lack of limb use after a time can cause other problems, such as muscle wasting, osteoporosis, and stiffness in the joints.
What is referred pain?
Also known as reflective pain. When pain is felt either next to, or at a distance from the origin of an injury it is called referred pain. For example, when a person has a heart attack, even though the affected area is the heart, the pain is sometimes felt around the shoulders, back and neck, rather than in the chest. We have known about referred pain for centuries, but we still do not know its origins and what causes it.
How do you measure pain?
It is virtually impossible to measure a person's pain objectively. Most experts say that the best way to find out how much pain a person is enduring is by a subjective pain report. A comprehensive assessment of pain should include:
The identification of all the pains. This must include the most important ones.
The site, quality, and radiation of pain
What factors aggravate and relieve the pain

When the pain occurs throughout the day

What impact the pain has on the person's function

What impact the pain has on the person's mood

The sufferers' understanding of their pain
There are many different methods for measuring pain and its severity. Health care professionals say it is important to stick to whatever system or tool you chose for a specific patient all the way through. If a patient is unable to report his pain, such as an infant, or a person with dementia, there are a number of observational pain measures a doctor can use.

Here is a list of some pain measures used today:

Numerical Rating Scales

The patient is given a form which asks him to tick from 0 to 10 what his level of pain is. 0 is no pain, 5 is moderate pain, and 10 is the worst pain imaginable.

Please rate the pain you have right now
0 2 3 4 5 6 7 8 9 10
No pain Moderate pain Worst pain imaginable


The Numerical Rating Scales are useful if you want to measure any changes in pain, as well as gauging the patient's response to pain treatment. If the patient has dyslexia, autism, or is very elderly and has dementia this may not be the best tool (see the ones below).

Verbal Descriptor Scale

This type of scale exists in many different forms. The patient is asked questions and responds verbally choosing from such terms as mild, moderate, severe, no pain, mild pain, discomforting, distressing, horrible, and excruciating.

Elderly patients with cognitive impairment, very young children, and people who respond better to verbal stimuli tend to have better completion rates with this type of scale, compared to the written numerical scale. Children respond even better to the faces scale (description below).

Faces Scale

The patient sees a series of faces. The first one is calm and happy, the second less so, etc., and the final one has an expression of extreme pain. This scale is used mainly for children, but can also be used with elderly patients with cognitive impairment. Patients with autism may respond better to this type of approach - people with autism tend to respond to visual stimuli well.

Brief Pain Inventory

This is a much more comprehensive written questionnaire. Not only does it gauge current level of pain, but also records the peaks and troughs of pain during previous days, how pain has affected mood, activity, sleep patterns, and how the pain may have affected the patient's interpersonal relationship. The questionnaire also has diagrams which the patient shades - the shaded parts being where the pain is located and where it is most severe.

McGill Pain Questionnaire

This questionnaire measures the intensity (severity) of the pain, the quality of the pain, mood, and understanding of the pain. It is also known as the McGill Pain Index. It is a scale of rating pain developed at McGill University by Melzack and Torgerson (1971).

Look at the 20 groups below.
Circle one word in each group that best describes your pain.
Circle only three words from Groups 1 to 10 that best describe your pain response.
Choose just two words in Groups 11 to 15 that best describe your pain.
Just pick the one in Group 16.
Finally, choose just one word from Groups 17-20.
You should now have seven words. Those seven words should be taken to your doctor. They will help describe both the quality and intensity of your pain.

Group 1 - Flickering, Pulsing, Quivering, Throbbing, Beating, Pounding
Group 2 - Jumping, Flashing, Shooting
Group 3 - Pricking, Boring, Drilling, Stabbing
Group 4 - Sharp, Gritting, Lacerating
Group 5 - Pinching, Pressing, Gnawing, Cramping, Crushing
Group 6 - Tugging, Pulling, Wrenching
Group 7 - Hot, Burning, Scalding, Searing
Group 8 - Tingling, Itching, Smarting, Stinging
Group 9 - Dull, Sore, Hurting, Aching, Heavy
Group 10 - Tender, Taunt, Rasping, Splitting
Group 11 - Tiring, Exhausting
Group 12 - Sickening, Suffocating
Group 13 - Fearful, Frightful, Terrifying
Group 14 - Punishing, Grueling, Cruel, Vicious, Killing
Group 15 - Wretched, Binding
Group 16 - Annoying, Troublesome, Miserable, Intense, Unbearable
Group 17 - Spreading, Radiating, Penetrating, Piercing
Group 18 - Tight, Numb, Squeezing, Drawing, Tearing
Group 19 - Cool, Cold, Freezing
Group 20 - Nagging, Nauseating, Agonizing, Dreadful, Torturing

Measuring pain when the patient is cognitively impaired

In this case doctors say that the patient's subjective pain report is the most effective and accurate way of evaluating pain. If the severely cognitively impaired patient is observed carefully it is possible to pick out clues as to the presence of pain, e.g. restlessness, crying, moaning, groaning, grimacing, resistance to care, reduced social interactions, increased wandering, not eating, and sleeping problem

How We Perceive Pain

Three people can stub the same toe at the same time and all three may have different responses to the pain. Do we have different pain tolerances? No, but how we perceive pain can be very different. The way we interpret pain can be influenced by things like age, gender, expectations, emotions, and even memories of past experiences. If you expect something to hurt you are predisposing yourself to a higher degree of pain. Have you ever seen a small child trip and fall? There are times when they won’t shed a tear until someone asks “are you ok?” and then they will begin to realize that what happened could have caused pain. This type of pain, called ancillary pain, is what happens when you “work yourself up”.

The brain will send out signal nerve cells that will release painkillers that occur naturally in the body. These natural painkillers, like endorphins for example, will lessen the pain response. This is what happens when you take your mind off of what would be a painful experience and focus on other things, such as what happens when you meditate. Another example of this is the use of focus points when going through natural labor in Lamaze classes. The woman is conditioned to focus her energy and breathing onto a single object, and effectively blocks out pain. Men typically have a higher tolerance for pain because they are usually brought up to “not cry”. Pain can sometimes be seen as a sign of weakness instead of a normal bodily response, and therefore men will condition themselves to take more pain than is normal.

Things that can reduce the number of endorphins in the body are stress, anxiety, and depression. This reduction in endorphins means that the body will be responding to the pain message more severely than if you were not stressed, anxious, or depressed. The adage telling you to think good things and keep a positive mood may have some medicinal bearing when it comes to chronic pain.

More OSHA stuff.

Specfic info just for the auditory rules for factory workers.

http://www.dosh.gov.my/Informasi/PeraturanAKJ/Peraturan14.pdf

The Perkeso website meant for compensation.

http://www.perkeso.gov.my/

Laws that govern compensation.

http://www.agc.gov.my/agc/Akta/Vol.%206/Act%20273.pdf

Thanks to Xin Wei of Group I and Adib.

Role Play 2

a) how we know that many years of exposure to loud noise causes hearing impairment?
Sound-induced hearing loss is irreversible and the main form of treatment is prevention. Commonly, damage to sensory cells of the inner ear builds up over time. The hearing loss goes unnoticed at first and increases until it reaches a certain degree where it becomes obvious to the affected person. In rare cases, exposure to very loud sounds can lead to immediate damage.

exposure to loud sounds at a young age can make the ear more vulnerable to ageing. Over the years, there are small unnoticeable effects on the inner ear that only become evident many years later when the affected person develops hearing loss. Exposure to certain chemicals, smoking or lack of oxygen supply to the body also increase sound-induced hearing loss.
Exposure to loud sounds can produce some initial damage to the inner ear, for instance by causing inflammation. This triggers processes that cause cells to destroy themselves and results in further damage through the loss of sensory and nervous cells.

How do loud sounds affect the inner ear?
Extremely loud sounds such as those produced by bomb blasts can cause small cracks in various parts of the ear which can be seen with a simple microscope. However, in most cases, the damage to the inner ear occurs at cellular level and is thus less visible.

Sensory cells in the inner ear (hair cells of the cochlea) convert sounds into signals that can be interpreted by the brain and losing these cells causes permanent hearing loss. Different hair cells are receptive to different sound frequencies. The wider the loss, the larger the number of sound frequencies that are affected. For each frequency, the greater the number of lost cells, the larger the hearing impairment. Because of the shape and the characteristics of the human outer and middle ear, excessive exposure to loud sounds makes individuals less sensitive to high-pitched sounds at frequencies of 4 to 6 kHz.

Losing one type of sensory cells completely (outer hair cells) results in a hearing impairment of 50 to 70 dB and also makes affected individuals less capable of focusing on a particular frequency and therefore less able to understand speech in noisy environments.

Recent advances made using more powerful microscopes show that losing or damaging hair cells is not the only factor that harms hearing. Loud sounds can also harm other types of cells, such as nerve cells, in the organ of the inner ear that converts sound into electrical impulses (cochlea). However, the chain of events that leads to cell damage and to the resulting hearing loss is not well understood at present.

Short exposures to steady loud sounds can damage the cochlea but this damage is usually reversible and the effect on hearing loss is temporary. Repeated exposures to very loud sounds can cause irreversible damage; in that case the hearing loss is permanent.

The likelihood that exposure to a particular sound will result in temporary or permanent hearing loss depends not only on loudness and exposure time but also on how quickly sound levels increase. The body has a reflex to contract certain muscles in order to protect the ear from excessively loud sounds. Sudden, very loud sounds such as explosions occur too quickly for the body to activate this reflex and are therefore a lot more harmful to hearing than steady sounds, in particular at high frequencies.

The inner ear of some people is more vulnerable to damage than that of others. Several factors – some of which are genetic – play a role, such as smoking, high blood pressure, fat levels, age, gender, as well as other anatomical characteristics.

Average noise levels in certain working environments can reach up to about 90-125 dB. People also expose themselves to loud sounds in their leisure activities. Outside the workplace, a high risk of hearing impairment arises for instance from attending rock concerts and discos, from practicing noisy sports such as shooting, and from exposure to military noise. Children could be exposed to noisy toys such as trumpets (92 to 125 dB SPL), whistles (107 to 129 dB SPL) and toy weapons (113 to over 135 dB SPL).

Listening to music played at high volumes can be as dangerous to hearing as industrial noise. This applies not only to rock concerts or nightclubs but also to personal music players (and mobile phones with music playing function) which can generate sounds across a broad frequency range at high volumes without distortion.

In our daily lives we are also exposed to environmental noise from traffic, construction, aircraft or various noises in the neighbourhood. These noises do not reach levels that can damage hearing but can be very irritating and cause other harmful effects.

Excessive exposure to loud sounds is a major cause of hearing disorders worldwide and is the main avoidable cause of permanent hearing loss.

Among workers, noise-induced hearing loss is the most common irreversible occupational disease. Worldwide, 16% of the disabling hearing loss in adults is caused by exposure to noise at work, although this proportion varies in different parts of the world from 7% to 21%.

Sound-induced hearing loss affects an estimated 10 to 15 million people in the USA. In the UK, about 350 000 people aged 35 to 64 years have serious hearing difficulties, including tinnitus, caused by exposure to noise at work. In France, a survey carried out in 2003 indicates that 7 % of employed workers were exposed to excessive sound levels above 85 dB(A) for at least 20 hours a week . Most exposed workers belonged to industry agriculture or the building sector.
People working with vibrating tools, such as jackhammers, can develop hearing loss. The effect is worse if exposure to vibration and to loud sounds occurs at the same time. It is unclear whether body vibration causes any damage.

Go to this website http://www.abelard.org/hear/hear.php#how-loud
to find out the effects of specific decibels on our hearing


b) What happens to the ear when it is damaged by noise?
Exposure to harmful sounds causes damage to the hair cells as well as the auditory, or hearing, nerve. Impulse sound can result in immediate hearing loss that may be permanent. This kind of hearing loss may be accompanied by tinnitus—a ringing, buzzing, or roaring in the ears or head—which may subside over time. Hearing loss and tinnitus may be experienced in one or both ears, and tinnitus may continue constantly or occasionally throughout a lifetime.

Exposure to impulse and continuous noise may cause only a temporary hearing loss. If a person regains hearing, the temporary hearing loss is called a temporary threshold shift. The temporary threshold shift largely disappears 16 to 48 hours after exposure to loud noise. You can prevent NIHL from both impulse and continuous noise by regularly using hearing protectors such as earplugs or earmuffs.

Scientists believe that, depending on the type of noise, the pure force of vibrations from the noise can cause hearing loss. Recent studies also show that exposure to harmful noise levels triggers the formation of molecules inside the ear that damage hair cells and result in NIHL. These destructive molecules play an important role in hearing loss in children and adults who listen to loud noise for too long.

Sound-induced hearing damage is not limited to deafness or an inability to hear certain sounds, but also includes difficulties understanding speech in noisy environments, ringing in the ears (tinnitus) and hypersensitivity to loud sounds.

The initial damage caused by loud sounds is often small and causes slight hearing problems that disappear some time after the sound exposure, so these often go unnoticed.

With repeated exposure to loud sounds, hearing disturbances increase. By the time they are noticed, the damage has become permanent and almost always incurable.

Excessive exposure to loud sounds can not only damage the organ of the inner ear that converts sound into electrical impulses (cochlea) but also the part that contributes to balance and spatial orientation (vestibule). Balance involves the eye and the ear but also the neck muscles that keep the head stable. Hearing damage can therefore be assessed indirectly by creating a sound and measuring how the neck muscles react to it.

Temporary or permanent high-pitched ringing in the ear (tinnitus) induced by loud sounds can sometimes be the only indication of hearing damage in the early stage, which may then be accompanied by hearing loss with continued exposure. After exposure to very loud or sudden loud sounds, tinnitus appears rapidly and is often temporary. In opposition, when it results from continuous long-term sound exposure, tinnitus often only appears after several years but remains permanent.

One of the most common forms of hearing impairment is hearing loss, which is the inability of the affected individual to hear sounds below certain thresholds. This can be measured with standard hearing tests. Certain people with normal hearing thresholds can nonetheless have problems understanding speech due to difficulties in processing sounds.

Hearing problems linked to the outer or middle ear can usually be treated, while problems in the inner ear or the auditory nerve going from the ear to the brain are usually permanent.

Hearing impairment refers to the complete or partial loss of the ability to hear from one of both ears and can be graded as mild, moderate, severe or profound. When the hearing threshold in the better ear is at or below 25 dB, this will pose very little or no hearing problems. At the other extreme, threshold values in the better ear at or above 81 dB result in the listener being unable to hear and understand even a shouted voice.

Hearing impairment that is caused by a problem in the outer or middle ear can usually be treated. When the impairment is due to problems in the inner ear or the auditory nerve going from the ear to the brain, the hearing loss is usually permanent. Common causes of this type of hearing problem are ageing, excessive exposure to loud sounds and some drugs.

Hearing is usually tested by presenting sounds of different frequencies to the listener and measuring the lowest volume of the sound that the listener can detect. The threshold of hearing is set at 0 dB HL and levels between 0 and 20 are considered to be normal.

Any sign of a shift in this threshold, even within the normal range, could be a sign of impairment so it is important to assess any such change, particularly for children.

Hearing impairment may also arise in people with normal threshold levels of hearing but who cannot process the sound signals properly and therefore find it very difficult to understand speech. Other people have trouble focusing on particular sound frequencies; they cannot tune in to sounds of interest and are distracted by background noise.

The ability to understand speech depends on how loudly a person speaks and on hearing loss, and can be described by mathematical models. A normal-hearing person can understand the words in a sentence if about 30% of the information is present. Listeners can fail to understand speech if the volume of the sound is below the threshold value they can hear, or if there is a background noise that masks the sound signal.

In everyday situations, listeners are exposed to combinations of many different sounds. People with hearing loss at high frequencies have difficulties understanding speech in noisy environments such as a party where there are many different conversations taking place or in large rooms with a lot of echoes such as a church hall. For instance, if a normal-hearing person can communicate at a party at a distance of about one meter, a high-frequency hearing loss of about 40 dB makes it impossible to do so; the listener has to come closer to the speaker and reduce the distance to half a meter.

People with a more significant hearing loss at high frequencies will find it impossible to understand speech in noisy environments unless they get extremely close to the speaker, which may be socially unacceptable. Hearing aids can only partly compensate such loss. Therefore, high-frequency hearing loss, whether aided or not, will cause poorer speech understanding in a noisy environment.


c) How noise-induced hearing loss differs from conductive hearing loss?
Refer to Huey Ting's. Lazy to retype... =.='
Basically noise-induced hearing loss comes under sensorineural.

Conductive Hearing Loss
Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones, or ossicles, of the middle ear. Conductive hearing loss usually involves a reduction in sound level, or the ability to hear faint sounds. This type of hearing loss can often be medically or surgically corrected.

Sensorineural hearing loss occurs when there is damage to the inner ear (cochlea) or to the nerve pathways from the inner ear (retrocochlear) to the brain. Sensorineural hearing loss cannot be medically or surgically corrected. It is a permanent loss.

Sensorineural hearing loss not only involves a reduction in sound level, or ability to hear faint sounds, but also affects speech understanding, or ability to hear clearly.

Sensorineural hearing loss can be caused by diseases, birth injury, drugs that are toxic to the auditory system, and genetic syndromes. Sensorineural hearing loss may also occur as a result of noise exposure, viruses, head trauma, aging, and tumors.

What is noise-induced hearing loss?

The sound pathwayEvery day, we experience sound in our environment, such as the sounds from television and radio, household appliances, and traffic. Normally, we hear these sounds at safe levels that do not affect our hearing. However, when we are exposed to harmful noise—sounds that are too loud or loud sounds that last a long time—sensitive structures in our inner ear can be damaged, causing noise-induced hearing loss (NIHL). These sensitive structures, called hair cells, are small sensory cells that convert sound energy into electrical signals that travel to the brain. Once damaged, our hair cells cannot grow back

What sounds cause NIHL?
NIHL can be caused by a one-time exposure to an intense “impulse” sound, such as an explosion, or by continuous exposure to loud sounds over an extended period of time, such as noise generated in a woodworking shop.

OSHA

Here is a comprehensive 67 slides on osha.. haha u can dload it HERE from this link.. Just click on the link on the HTML format file once you clicked it, to dload the powerpoint file (:

Hope you ppl have done your practicals!

See ya tmr (:

Anatomy of the Ear

Sorry i cant seem to get the pictures in here is the link so you guys can read.. some of the terms used are a lil different so i put them in brackets in the article i posted:

http://www.webschoolsolutions.com/patts/systems/ear.htm

Here is another site......... Anatomy of the ear made FUN^_^:

http://www.wisc-online.com/objects/index_tj.asp?objID=AP1502

Anatomy of the Ear

Introduction
The ears are paired sensory organs comprising the auditory system, involved in the detection of sound, and the vestibular system, involved with maintaining body balance/ equilibrium. The ear divides anatomically and functionally into three regions: the external ear, the middle ear, and the inner ear. All three regions are involved in hearing. Only the inner ear functions in the vestibular system.
Anatomy of the Ear
The external ear (or pinna, the part you can see) serves to protect the tympanic membrane (eardrum), as well to collect and direct sound waves through the ear canal(external acoustic meatus) to the eardrum. About 1¼ inches long, the canal contains modified sweat glands that secrete cerumen, or earwax. Too much cerumen can block sound transmission.


The middle ear, separated from the external ear by the eardrum, is an air-filled cavity (tympanic cavity) carved out of the temporal bone. It connects to the throat/nasopharynx via the Eustachian tube(pharyngotympanic tube). This ear-throat connection makes the ear susceptible to infection (otitis media). The eustachian tube functions to equalize air pressure on both sides of the eardrum. Normally the walls of the tube are collapsed. Swallowing and chewing actions open the tube to allow air in or out, as needed for equalization. Equalizing air pressure ensures that the eardrum vibrates maximally when struck by sound waves.
Adjoining the eardrum are three linked, movable bones called "ossicles," which convert the sound waves striking the eardrum into mechanical vibrations. The smallest bones in the human body, the ossicles are named for their shape. The hammer (malleus) joins the inside of the eardrum. The anvil (incus), the middle bone, connects to the hammer and to the stirrup (stapes). The base of the stirrup, the footplate, fills the oval window which leads to the inner ear.
The inner ear consists of a maze of fluid-filled tubes, running through the temporal bone of the skull. The bony tubes, the bony labyrinth, are filled with a fluid called perilymph. Within this bony labyrinth is a second series of delicate cellular tubes, called the membranous labyrinth, filled with the fluid called endolymph. This membranous labyrinth contains the actual hearing cells, the hair cells of the organ of Corti(spiral organ). There are three major sections of the bony labyrinth:

The front portion is the snail-shaped cochlea, which functions in hearing.
The rear part, the semicircular canals, helps maintain balance.
Interconnecting the cochlea and the semicircular canals is the vestibule, containing the sense organs responsible for balance, the utricle and saccule.
The inner ear has two membrane-covered outlets into the air-filled middle ear - the oval window and the round window. The oval window sits immediately behind the stapes, the third middle ear bone, and begins vibrating when "struck" by the stapes. This sets the fluid of the inner ear sloshing back and forth. The round window serves as a pressure valve, bulging outward as fluid pressure rises in the inner ear. Nerve impulses generated in the inner ear travel along the vestibulocochlear nerve (cranial nerve VIII), which leads to the brain. This is actually two nerves, somewhat joined together, the cochlear nerve for hearing and the vestibular nerve for equilibrium.


How We Hear - The Auditory System

All sounds (music, voice, a mouse-click, etc.) send out vibrations, or sound waves. Sound waves do not travel in a vacuum, but rather require a medium for sound transmission, e.g. air or fluid. What actually travels are alternating successions of increased pressure in the medium, followed by decreased pressure. These vibrations occur at various frequencies, not all of which the human ear can hear. Only those frequencies ranging from 20 to 20,000 Hz (Hz = hertz = cycles/sec) can be perceived.

In hearing, air-borne sound waves funnel down through the ear canal and strike the eardrum, causing it to vibrate. The vibrations are passed to the small bones of the middle ear (ossicles), which form a system of interlinked mechanical levers: First, vibrations pass to the malleus (hammer), which pushes the incus (anvil), which pushes the stapes (stirrup). The base of the stapes rocks in and out against the oval window - this is the entrance for the vibrations. The stapes agitates the perilymph of the bony labyrinth. At this point, the vibrations become fluid-borne. The perilymph, in turn, transmits the vibrations to the endolymph of the membranous labyrinth and, thence, to the hair cells of the organ of Corti. It is the movement of these hair cells which convert the vibrations into nerve impulses. The round window dissipates the pressure generated by the fluid vibrations, thus serves as the release valve: It can push out or expand as needed. The nerve impulses travel over the cochlear nerve to the auditory cortex of the brain, which interprets the impulses as sound.

Noise Induced Hearing Loss

http://www.aafp.org/afp/20000501/2749.html

Hearing Aid

What is a hearing aid?

A hearing aid is a small electronic device that you wear in or behind your ear. It makes some sounds louder so that a person with hearing loss can listen, communicate, and participate more fully in daily activities. A hearing aid can help people hear more in both quiet and noisy situations. However, only about one out of five people who would benefit from a hearing aid actually uses one.

A hearing aid has three basic parts: a microphone, amplifier, and speaker. The hearing aid receives sound through a microphone, which converts the sound waves to electrical signals and sends them to an amplifier. The amplifier increases the power of the signals and then sends them to the ear through a speaker.

How can hearing aids help?

Hearing aids are primarily useful in improving the hearing and speech comprehension of people who have hearing loss that results from damage to the small sensory cells in the inner ear, called hair cells. This type of hearing loss is called sensorineural hearing loss. The damage can occur as a result of disease, aging, or injury from noise or certain medicines.

A hearing aid magnifies sound vibrations entering the ear. Surviving hair cells detect the larger vibrations and convert them into neural signals that are passed along to the brain. The greater the damage to a person’s hair cells, the more severe the hearing loss, and the greater the hearing aid amplification needed to make up the difference. However, there are practical limits to the amount of amplification a hearing aid can provide. In addition, if the inner ear is too damaged, even large vibrations will not be converted into neural signals. In this situation, a hearing aid would be ineffective.

How can I find out if I need a hearing aid?

If you think you might have hearing loss and could benefit from a hearing aid, visit your physician, who may refer you to an otolaryngologist or audiologist. An otolaryngologist is a physician who specializes in ear, nose, and throat disorders and will investigate the cause of the hearing loss. An audiologist is a hearing health professional who identifies and measures hearing loss and will perform a hearing test to assess the type and degree of loss.

Are there different styles of hearing aids?

There are three basic styles of hearing aids. The styles differ by size, their placement on or inside the ear, and the degree to which they amplify sound.

• Behind-the-ear (BTE) hearing aids consist of a hard plastic case worn behind the ear and connected to a plastic earmold that fits inside the outer ear. The electronic parts are held in the case behind the ear. Sound travels from the hearing aid through the earmold and into the ear. BTE aids are used by people of all ages for mild to profound hearing loss.
  
  A new kind of BTE aid is an open-fit hearing aid. Small, open-fit aids fit behind the ear completely, with only a narrow tube inserted into the ear canal, enabling the canal to remain open. For this reason, open-fit hearing aids may be a good choice for people who experience a buildup of earwax, since this type of aid is less likely to be damaged by such substances. In addition, some people may prefer the open-fit hearing aid because their perception of their voice does not sound “plugged up.”
• In-the-ear (ITE) hearing aids fit completely inside the outer ear and are used for mild to severe hearing loss. The case holding the electronic components is made of hard plastic. Some ITE aids may have certain added features installed, such as a telecoil. A telecoil is a small magnetic coil that allows users to receive sound through the circuitry of the hearing aid, rather than through its microphone. This makes it easier to hear conversations over the telephone. A telecoil also helps people hear in public facilities that have installed special sound systems, called induction loop systems. Induction loop systems can be found in many churches, schools, airports, and auditoriums. ITE aids usually are not worn by young children because the casings need to be replaced often as the ear grows.

Canal aids fit into the ear canal and are available in two styles. The in-the-canal (ITC) hearing aid is made to fit the size and shape of a person’s ear canal. A completely-in-canal (CIC) hearing aid is nearly hidden in the ear canal. Both types are used for mild to moderately severe hearing loss.

Because they are small, canal aids may be difficult for a person to adjust and remove. In addition, canal aids have less space available for batteries and additional devices, such as a telecoil. They usually are not recommended for young children or for people with severe to profound hearing loss because their reduced size limits their power and volume.

Do all hearing aids work the same way?

Hearing aids work differently depending on the electronics used. The two main types of electronics are analog and digital.

Analog aids convert sound waves into electrical signals, which are amplified. Analog/adjustable hearing aids are custom built to meet the needs of each user. The aid is programmed by the manufacturer according to the specifications recommended by your audiologist. Analog/programmable hearing aids have more than one program or setting. An audiologist can program the aid using a computer, and the user can change the program for different listening environments—from a small, quiet room to a crowded restaurant to large, open areas, such as a theater or stadium. Analog/programmable circuitry can be used in all types of hearing aids. Analog aids usually are less expensive than digital aids.

Digital aids convert sound waves into numerical codes, similar to the binary code of a computer, before amplifying them. Because the code also includes information about a sound’s pitch or loudness, the aid can be specially programmed to amplify some frequencies more than others. Digital circuitry gives an audiologist more flexibility in adjusting the aid to a user’s needs and to certain listening environments. These aids also can be programmed to focus on sounds coming from a specific direction. Digital circuitry can be used in all types of hearing aids.

Which hearing aid will work best for me?

The hearing aid that will work best for you depends on the kind and severity of your hearing loss. If you have a hearing loss in both of your ears, two hearing aids are generally recommended because two aids provide a more natural signal to the brain. Hearing in both ears also will help you understand speech and locate where the sound is coming from.

You and your audiologist should select a hearing aid that best suits your needs and lifestyle. Price is also a key consideration because hearing aids range from hundreds to several thousand dollars. Similar to other equipment purchases, style and features affect cost. However, don’t use price alone to determine the best hearing aid for you. Just because one hearing aid is more expensive than another does not necessarily mean that it will better suit your needs.

A hearing aid will not restore your normal hearing. With practice, however, a hearing aid will increase your awareness of sounds and their sources. You will want to wear your hearing aid regularly, so select one that is convenient and easy for you to use. Other features to consider include parts or services covered by the warranty, estimated schedule and costs for maintenance and repair, options and upgrade opportunities, and the hearing aid company’s reputation for quality and customer service.

What questions should I ask before buying a hearing aid?

Before you buy a hearing aid, ask your audiologist these important questions:

• What features would be most useful to me?
• What is the total cost of the hearing aid? Do the benefits of newer technologies outweigh the higher costs?
• Is there a trial period to test the hearing aids? (Most manufacturers allow a 30- to 60-day trial period during which aids can be returned for a refund.) What fees are nonrefundable if the aids are returned after the trial period?
• How long is the warranty? Can it be extended? Does the warranty cover future maintenance and repairs?
• Can the audiologist make adjustments and provide servicing and minor repairs? Will loaner aids be provided when repairs are needed?
• What instruction does the audiologist provide?

How can I adjust to my hearing aid?

Hearing aids take time and patience to use successfully. Wearing your aids regularly will help you adjust to them.

Become familiar with your hearing aid’s features. With your audiologist present, practice putting in and taking out the aid, cleaning it, identifying right and left aids, and replacing the batteries. Ask how to test it in listening environments where you have problems with hearing. Learn to adjust the aid’s volume and to program it for sounds that are too loud or too soft. Work with your audiologist until you are comfortable and satisfied.

You may experience some of the following problems as you adjust to wearing your new aid.

• My hearing aid feels uncomfortable. Some individuals may find a hearing aid to be slightly uncomfortable at first. Ask your audiologist how long you should wear your hearing aid while you are adjusting to it.
• My voice sounds too loud. The “plugged-up” sensation that causes a hearing aid user’s voice to
  sound louder inside the head is called the occlusion effect, and it is very common for new hearing
  aid users. Check with your audiologist to see if a correction is possible. Most individuals get used to
  this effect over time.
• I get feedback from my hearing aid. A whistling sound can be caused by a hearing aid that does not fit or work well or is clogged by earwax or fluid. See your audiologist for adjustments.
• I hear background noise. A hearing aid does not completely separate the sounds you want to hear from the ones you do not want to hear. Sometimes, however, the hearing aid may need to be adjusted. Talk with your audiologist.
• I hear a buzzing sound when I use my cell phone. Some people who wear hearing aids or have implanted hearing devices experience problems with the radio frequency interference caused by digital cell phones. Both hearing aids and cell phones are improving, however, so these problems are occurring less often. When you are being fitted for a new hearing aid, take your cell phone with you to see if it will work well with the aid.

How can I care for my hearing aid?

Proper maintenance and care will extend the life of your hearing aid. Make it a habit to:

• Keep hearing aids away from heat and moisture.
• Clean hearing aids as instructed. Earwax and ear drainage can damage a hearing aid.
• Avoid using hairspray or other hair care products while wearing hearing aids.
• Turn off hearing aids when they are not in use.
• Replace dead batteries immediately.
• Keep replacement batteries and small aids away from children and pets.

Are new types of aids available?

Although they work differently than the hearing aids described above, implantable hearing aids are designed to help increase the transmission of sound vibrations entering the inner ear. A middle ear implant (MEI) is a small device attached to one of the bones of the middle ear. Rather than amplifying the sound traveling to the eardrum, an MEI moves these bones directly. Both techniques have the net result of strengthening sound vibrations entering the inner ear so that they can be detected by individuals with sensorineural hearing loss.

A bone-anchored hearing aid (BAHA) is a small device that attaches to the bone behind the ear. The device transmits sound vibrations directly to the inner ear through the skull, bypassing the middle ear. BAHAs are generally used by individuals with middle ear problems or deafness in one ear. Because surgery is required to implant either of these devices, many hearing specialists feel that the benefits may not outweigh the risks.

Can I obtain financial assistance for a hearing aid?

Hearing aids are generally not covered by health insurance companies, although some do. For eligible children and young adults ages 21 and under, Medicaid will pay for the diagnosis and treatment of hearing loss, including hearing aids, under the Early and Periodic Screening, Diagnostic, and Treatment (EPSDT) service. Also, children may be covered by their state’s early intervention program or State Children’s Health Insurance Program (SCHIP).

Medicare does not cover hearing aids for adults; however, diagnostic evaluations are covered if they are ordered by a physician for the purpose of assisting the physician in developing a treatment plan. Since Medicare has declared the BAHA a prosthetic device and not a hearing aid, Medicare will cover the BAHA if other coverage policies are met.

Some nonprofit organizations provide financial assistance for hearing aids, while others may help provide used or refurbished aids. Contact the National Institute on Deafness and Other Communication Disorders’ (NIDCD’s) Information Clearinghouse with questions about organizations that offer financial assistance for hearing aids.

Noise-Induced Hearing Loss

What is noise-induced hearing loss?

The sound pathwayEvery day, we experience sound in our environment, such as the sounds from television and radio, household appliances, and traffic. Normally, we hear these sounds at safe levels that do not affect our hearing. However, when we are exposed to harmful noise—sounds that are too loud or loud sounds that last a long time—sensitive structures in our inner ear can be damaged, causing noise-induced hearing loss (NIHL). These sensitive structures, called hair cells, are small sensory cells that convert sound energy into electrical signals that travel to the brain. Once damaged, our hair cells cannot grow back

What sounds cause NIHL?
NIHL can be caused by a one-time exposure to an intense “impulse” sound, such as an explosion, or by continuous exposure to loud sounds over an extended period of time, such as noise generated in a woodworking shop.

Sound is measured in units called decibels. On the decibel scale, an increase of 10 means that a sound is 10 times more intense, or powerful. To your ears, it sounds twice as loud. The humming of a refrigerator is 45 decibels, normal conversation is approximately 60 decibels, and the noise from heavy city traffic can reach 85 decibels. Sources of noise that can cause NIHL include motorcycles, firecrackers, and small firearms, all emitting sounds from 120 to 150 decibels. Long or repeated exposure to sounds at or above 85 decibels can cause hearing loss. The louder the sound, the shorter the time period before NIHL can occur. Sounds of less than 75 decibels, even after long exposure, are unlikely to cause hearing loss.

Although being aware of decibel levels is an important factor in protecting one’s hearing, distance from the source of the sound and duration of exposure to the sound are equally important. A good rule of thumb is to avoid noises that are “too loud” and “too close” or that last “too long.”

What are the effects of NIHL?
Exposure to harmful sounds causes damage to the hair cells as well as the auditory, or hearing, nerve (see figure). Impulse sound can result in immediate hearing loss that may be permanent. This kind of hearing loss may be accompanied by tinnitus—a ringing, buzzing, or roaring in the ears or head—which may subside over time. Hearing loss and tinnitus may be experienced in one or both ears, and tinnitus may continue constantly or occasionally throughout a lifetime.

Continuous exposure to loud noise also can damage the structure of hair cells, resulting in hearing loss and tinnitus, although the process occurs more gradually than for impulse noise.

Exposure to impulse and continuous noise may cause only a temporary hearing loss. If a person regains hearing, the temporary hearing loss is called a temporary threshold shift. The temporary threshold shift largely disappears 16 to 48 hours after exposure to loud noise. You can prevent NIHL from both impulse and continuous noise by regularly using hearing protectors such as earplugs or earmuffs.

Scientists believe that, depending on the type of noise, the pure force of vibrations from the noise can cause hearing loss. Recent studies also show that exposure to harmful noise levels triggers the formation of molecules inside the ear that damage hair cells and result in NIHL. These destructive molecules play an important role in hearing loss in children and adults who listen to loud noise for too long

What are the symptoms of NIHL?
When a person is exposed to loud noise over a long period of time, symptoms of NIHL will increase gradually. Over time, the sounds a person hears may become distorted or muffled, and it may be difficult for the person to understand speech. Someone with NIHL may not even be aware of the loss, but it can be detected with a hearing test.


Who is affected by NIHL?
People of all ages, including children, teens, young adults, and older people, can develop NIHL. Approximately 15 percent of Americans between the ages of 20 and 69—or 26 million Americans—have high frequency hearing loss that may have been caused by exposure to loud sounds or noise at work or in leisure activities. Recreational activities that can put someone at risk for NIHL include target shooting and hunting, snowmobile riding, woodworking and other hobbies, playing in a band, and attending rock concerts. Harmful noises at home may come from lawnmowers, leaf blowers, and shop tools.


Can NIHL be prevented?
NIHL is 100 percent preventable. All individuals should understand the hazards of noise and how to practice good hearing health in everyday life. To protect your hearing:

•Know which noises can cause damage (those at or above 85 decibels).

•Wear earplugs or other hearing protective devices when involved in a loud activity (special earplugs and earmuffs are available at hardware and sporting goods stores).

•Be alert to hazardous noise in the environment.

•Protect the ears of children who are too young to protect their own.

•Make family, friends, and colleagues aware of the hazards of noise.

•If you suspect hearing loss, have a medical examination by an otolaryngologist (a physician who specializes in diseases of the ears, nose, throat, head, and neck) and a hearing test by an audiologist (a health professional trained to measure and help individuals deal with hearing loss).


How we hear

Hair cells in the inner earHearing depends on a series of events that change sound waves in the air into electrical signals. Our auditory nerve then carries these signals to the brain through a complex series of steps.

•Sound waves enter the outer ear and travel through a narrow passageway called the ear canal, which leads to the eardrum.

•The eardrum vibrates from the incoming sound waves and sends these vibrations to three tiny bones in the middle ear. These bones are called the malleus, incus, and stapes.

•The bones in the middle ear amplify, or increase, the sound vibrations and send them to the inner ear—also called the cochlea—which is shaped like a snail and is filled with fluid. An elastic membrane runs from the beginning to the end of the cochlea, splitting it into an upper and lower part. This membrane is called the “basilar” membrane because it serves as the base, or ground floor, on which key hearing structures sit.

•The sound vibrations cause the fluid inside the cochlea to ripple, and a traveling wave forms along the basilar membrane. Hair cells—sensory cells sitting on top of the membrane—“ride the wave.”

•As the hair cells move up and down, their bristly structures bump up against an overlying membrane and tilt to one side. This tilting action causes pore-like channels, which are on the surface of the bristles, to open up. When that happens, certain chemicals rush in, creating an electrical signal.

•The auditory nerve carries this electrical signal to the brain, which translates it into a “sound” that we recognize and understand.

•Hair cells near the base of the cochlea detect higher-pitched sounds, such as a cell phone ringing. Those nearer the apex, or centermost point, detect lower-pitched sounds, such as a large dog barking.

What research about NIHL is being conducted?
The National Institute on Deafness and Other Communication Disorders (NIDCD) researches the causes, diagnosis, treatment, and prevention of hearing loss. Most hearing loss is caused by damaged hair cells, which do not grow back in humans and other mammals. NIDCD-supported researchers have helped to identify some of the many genes important for ear development and hearing; they have also been studying the possibility of using gene therapy to regrow hair cells in mammals.

NIDCD researchers also are investigating a potential way to prevent NIHL after noise exposure. Noise exposure triggers the formation of destructive molecules, called free radicals, which cause hair cell death. Researchers initially had thought that antioxidants—chemicals that protect against cell damage from free radicals—might prevent NIHL only if the antioxidants were given before noise exposure. In a recent study, however, the antioxidants in salicylate (aspirin) and Trolox (vitamin E) were given to guinea pigs as long as three days after noise exposure and still significantly reduced hearing loss. These results suggest that there is a window of opportunity in which it is possible to rescue hearing from noise trauma. NIDCD-funded researchers are now testing the ability of nutrients, such as vitamins and minerals, to prevent NIHL in military personnel and college students.