Nerve pain: What you don't know may hurt you

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LIFESTYLE FEATURE - Health and Family

Nerve pain: What you don’t know may hurt you

AN APPLE A DAY By Tyrone M. Reyes, M.D.

The Philippine STAR 03/30/2004

For most people, pain is useful. It alerts them to danger, gets them out

of harm’s way, and encourages them to cuddle injuries until they heal.

But thousands endure a different sort of pain – pain that serves no

purpose and persists even in the absence of external hazards. This is

neuropathic pain, caused by the damage or deterioration of nerves. A

related term is neuralgia, which refers to pain that extends along one

or more nerves.

Neuropathic pain can range from an occasional tingling in the hands or

feet to a persistent burning or stabbing sensation. Some people

experience such heightened sensitivity that even the brush of bed sheets

or a soft breeze can cause excruciating pain. Unable to sleep or

maintain a routine, people with this kind of pain may grow depressed

from their relentless suffering. Because its causes are complex – and

successful treatment challenging – the condition can frustrate doctors

and patients alike. Gradually, however, researchers and doctors are

getting a handle on what causes neuropathic pain. Treatment has

improved. Today, most people can get some measure of relief. Many Causes

Disease, poor nutrition, injuries, or faulty blood flow can damage

nerves. If the motor nerves that control muscles are affected, the

result can be weakness. If the autonomic nerves – which control rectal

bodily functions – are damaged, the circulating and digestive systems

can go awry. Sexual function may be hampered. Damage to the sensory

nerves can lead to numbness or – paradoxically – pain. The long

peripheral nerves of the arms and legs are especially vulnerable. About

20 percent of people over age 60 have some peripheral nerve damage.

Many people with diabetes eventually suffer from nerve damage. Estimates

of how many are affected range greatly, from 10 to 90 percent, depending

on how neuropathy is defined. Stocking and glove neuropathy is

especially common in diabetes. It may lead to a chronic burning pain

that begins in the feet and hands and spreads to the upper limbs and

trunk. Because alcohol can damage nerves, alcoholics are also prone to

this kind of neuropathy.

Other conditions that can damage peripheral nerves include

hypothyroidism, an inactive thyroid gland, and several of the autoimmune

diseases, such as rheumatoid arthritis or lupus. Nerve damage can also

result from exposure to certain chemicals, including heavy metals like

arsenic, lead, and thallium; pesticides; and some of the medicines used

to treat AIDS, TB and cancer.

Shingles

Sometimes, only a single nerve is damaged, although that doesn’t mean

there is any less pain. For example, carpal tunnel syndrome results from

prolonged pressure on the nerve that travels through the wrist. A

fracture or tumor can harm a nerve by pressing on it. The

varicella-zoster virus that causes chickenpox and herpes zoster, which

is often referred to as shingles, can also be a source of nerve pain.

Shingles is the reactivation of a " silent " varicella-zoster infection

following a case of childhood chickenpox. About half of the shingles

sufferers age 60 and over will experience lingering pain, most often in

the chest and face. The severity and duration of postherpetic neuralgia,

as doctors call it, increases with age. Vitamin B Deficiency

Poor nutrition, especially deficiencies in the B vitamins, can lead to

neuropathy. People with pernicious anemia, which occurs when vitamin B12

cannot be absorbed, usually experience relatively mild tingling or " pins

and needles " sensations. Alcoholism and eating disorders like anorexia

may set the stage for nutritional deficiencies with a variety of

negative health consequences, including neuropathy. If the damage is

widespread, it is called polyneuropathy.

But in many cases, the cause of neuropathic pain remains elusive. Of the

people who go to the doctor complaining of pain in their hands and feet,

about one-third turn out to have diabetes. Doctors can find a cause,

such as alcoholism, for another third. But for the rest, even an

exhaustive medical and neurological work-up reveals no clear reason for

the condition.

Relief

The first step in relieving neuropathic pain is to address any

underlying problem. If vitamin B deficiencies are to blame, taking

supplements will usually help, although sometimes, injections are

necessary. Too much of some B vitamins can be dangerous, so a doctor

should oversee such treatments. For people with diabetes, the key is

keeping a tight rein on blood sugar levels. It may also help to

exercise, limit alcohol, and quit smoking.

Patients who have painful feet with no known cause should think about

what they might be doing to harm peripheral nerves. The most common

culprit is alcohol. Even people who are not alcoholics may suffer from

nerve pain caused or exacerbated by drinking. Poor foot care can lead to

neuropathy and pain. Injuries to feet with damaged nerves, such as

people with diabetes and leprosy, can develop into ulcers, which in the

worst case can lead to amputation. Medications Aspirin, acetaminophen

(Tylenol), or other common pain relievers rarely relieve neuropathic

pain. Topical analgesics, pain relief medicines applied to the skin, may

help with peripheral neuropathies. For example, creams containing

capsaicin, the active ingredient in chili peppers, often help with pain

from postherpetic neuralgia. The cream may burn when first applied,

however, and it may take several weeks of continual use for it to have

full effect. Capsaicin creams can also relieve stocking and glove

neuropathy, although it can be hopelessly messy if you have to spread it

over a wide area. Studies have found that lidocaine skin patches also

reduce postherpetic pain. Topical prostaglandin is promising although

the data are only preliminary.

Tricyclic antidepressants, such as amitriptyline, often help alleviate

the burning and stabbing pain of shingles and diabetic neuropathies.

They usually work sooner and at lower doses for pain than for

depression. But the tricyclics have many side effects, including

drowsiness, dizziness and – especially for people in their 70s and 80s –

constipation. Newer antidepressants, like fluoxetine (Prozac), have

fewer side effects and may relieve some neuropathic pain, but their

track record is not as well established.

Anticonvulsant medications can also be a useful treatment, especially

for individuals who can’t tolerate antidepressants. In the 1950s,

carbamazepine (Tegretol) was introduced as a highly effective treatment

for trigeminal neuralgia, pain coming from one of the main nerves in the

face. It is among the most excruciating of chronic pain conditions. The

drug turned out to be an excellent anticonvulsant as well, and is now a

mainstay in the treatment of epilepsy. Carbamazepine and other

anticonvulsants that calm overexcited nerves continue to help some

people with chronic nerve pain.

A relatively newer anticonvulsant, gabapentin (Neurontin), has fewer

side effects and interacts less often with other drugs than

carbamazepine. Research has found it effective against postherpetic and

diabetic nerve pain. Mexiteline, used to treat heart arrhythmias, may

also help some pain patients for whom antidepressants and

anticonvulsants have failed. Like several other promising new drugs, it

can cause side effects, and it’s not clear how often doctors will wind

up prescribing it. Narcotics are highly effective against pain. But

partly because they carry the risk of addiction, doctors are reluctant

to prescribe them save as a last resort for people with terrible pain

that can’t be relieved by other means, such as some cancer patients.

Other Kinds Of Help

Unfortunately, people with nerve damage often go through a great deal of

trial and error before finding something that works. Physical therapy

may be tried. Acupuncture has helped some people. Biofeedback and

meditation can relax the muscles and give comfort. Some people benefit

from transcutaneous electrical nerve stimulation (TENS), in which

electrodes on the surface of the skin stimulate the nerves.

Chronic neuropathic pain is physically and emotionally draining. Support

groups or psychotherapy may help sufferers. The nonprofit Neuropathy

Association (www.neuropathy.org) is a good resource.

Many investigators are experimenting with nerve growth factor, a class

of proteins that affect nerve growth and regeneration. So far, the trial

results have been mixed.

The Bottom Line

For now, the best approach really is prevention. For example, you can

reduce your risk for painful neuropathies by eating a balanced diet rich

in B vitamins, watching your alcohol consumption, steering clear of

dangerous chemicals, exercising, and controlling your blood sugar if you

have diabetes.

Pain conditions are underdiagnosed and undertreated, especially in the

elderly. If you’re in constant pain, don’t be stoic. Visit your doctor.

Like most pain, neuropathic pain is best treated promptly and

aggressively. The longer it persists, the harder it is to conquer. The

earlier it is treated, the greater is your chance of successfully

relieving nerve pain.