INFECTIOUS DISEASE Viral Illnesses • Chickenpox • Mumps • Postherpetic neuralgia • Croup • Measles • Rubella • Mononucleosis • Smallpox • Parvovirus infection • West Nile virus • Roseola • Rabies • SARS • Viral hemorrhagic fevers • Polio • Hand-foot-and-mouth disease

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Postherpetic neuralgia (post-her-PET-ic noo-RAL-jah) is a painful condition affecting your nerve fibers and skin. It's a complication of shingles, a second outbreak of the varicella-zoster virus, which initially causes chickenpox.

During an initial infection of chickenpox, some of the virus can remain in your system, lying dormant inside nerve cells. Years later, factors such as age, illness, stress or medications can reactivate the virus, causing shingles, or it can also reactivate for no apparent reason.

Once reactivated, the virus travels along nerve fibers, causing pain. When the virus reaches your skin, it produces a rash and blisters. A case of shingles (herpes zoster) usually heals within a month. But some people continue to feel pain long after the rash and blisters heal. This pain is known as postherpetic neuralgia.

Not everyone who's had a reactivation of the virus develops postherpetic neuralgia. But postherpetic neuralgia is a common complication of shingles in older adults. The greater your age when the virus reactivates, the greater the chance you'll develop postherpetic neuralgia.

In most people, the pain of postherpetic neuralgia lessens over time. In the meantime — especially if symptoms are addressed early — treatments for postherpetic neuralgia can ease nerve-related pain.

The symptoms of postherpetic neuralgia are generally limited to the area of your skin where the shingles outbreak first occurred. They may include:

• Sharp and jabbing, burning, or deep and aching pain
• Extreme sensitivity to touch and temperature change
• Itching and numbness
• Headaches

In rare cases, you might also experience muscle weakness or paralysis — if the nerves involved also control muscle movement.

Postherpetic neuralgia results when nerve fibers are damaged during an outbreak of shingles. Damaged fibers aren't able to send messages from your skin to your brain as they normally do. Instead, the messages become confused and exaggerated, causing chronic, often excruciating pain that may persist for months — or even years — in the area where shingles first occurred.

This complication of shingles occurs much more frequently in older adults. Less than 10 percent of people younger than 60 develop postherpetic neuralgia after a bout of shingles, while about 40 percent of people older than 60 do.

See a doctor at the first sign of shingles. Treating shingles early — within three days of developing the rash — and aggressively with oral antiviral drugs may reduce the length and severity of postherpetic neuralgia.

If you do develop postherpetic neuralgia, see your doctor right away. Finding an effective treatment to relieve the pain can sometimes be frustrating. You may have to work with your doctor and sometimes other specialists to try a variety of treatments before you find something that helps.

Treatment for postherpetic neuralgia depends on the type of pain you experience. Possible options include:

• Lidocaine skin patches. These are small, bandage-like patches that contain the topical, pain-relieving medication lidocaine. These patches can be cut to fit only the affected area. You apply the patches, available by prescription, directly to painful skin to deliver temporary relief. Don't use patches containing lidocaine on your face.

• Antidepressants. Your doctor may prescribe antidepressants for postherpetic neuralgia even if you're not depressed because these drugs affect key brain chemicals, including serotonin and norepinephrine, which play a role in both depression and how your body interprets pain. Doctors typically prescribe antidepressants for postherpetic neuralgia in smaller doses than they do for depression.

  Drugs that inhibit the reuptake of norepinephrine and serotonin — including tricyclic antidepressants, such as amitriptyline, desipramine (Norpramin) and nortriptyline (Pamelor) — or a newer antidepressant approved for the treatment of postherpetic neuralgia, duloxetine (Cymbalta), may not eliminate the pain; however, they can make it more tolerable. Your doctor may also prescribe other antidepressants for postherpetic neuralgia, such as fluoxetine (Prozac, Sarafem).

• Certain anticonvulsants. Medications for treatment of seizures also can lessen the pain associated with postherpetic neuralgia. These medications stabilize abnormal electrical activity in your nervous system caused by injured nerves. Doctors may prescribe gabapentin (Neurontin), pregabalin (Lyrica) or another anticonvulsant to help control burning and pain.
• Injected steroids. Corticosteroid medications injected into the area around the spinal cord may help relieve the persistent pain of postherpetic neuralgia. This treatment is usually reserved until after the pustular skin rash associated with shingles has gone away.
• Painkillers. Some people may need prescription-strength pain medications, such as tramadol (Ultram) or oxycodone (OxyContin), to control their pain. However, these drugs are narcotics and can be addictive.
• Transcutaneous electrical nerve stimulation (TENS). This treatment involves the placement of electrodes over the painful area. The electrodes deliver tiny, painless electrical impulses to nearby nerve pathways. You turn the TENS unit on and off as needed to control pain. Exactly how the impulses relieve pain is uncertain. One theory is that the impulses stimulate production of endorphins, your body's natural painkillers. This treatment doesn't work for everyone.
• Spinal cord or peripheral nerve stimulation. These devices are similar to TENS, but are implanted underneath the skin. Like TENS units, you can turn these units on and off as needed to control pain. Before the device is surgically implanted, doctors do a trial first using a thin wire electrode. The trial is done to ensure that the stimulator will provide effective pain relief. The electrode is inserted through your skin into the epidural space over the spinal cord for a spinal cord stimulator or under your skin above a peripheral nerve in the case of a peripheral nerve stimulator. Some areas, such as your chest, abdomen and some areas of your face, can't benefit using this method.

In some cases, treatment of postherpetic neuralgia brings complete pain relief. But most people still experience some pain, and a few don't receive any relief. Although some people must live with postherpetic neuralgia the rest of their lives, most people can expect the condition to gradually disappear during the first three months. For about 10 percent to 20 percent of people with postherpetic neuralgia, the pain may persist for a year or more.

Although a vaccine to prevent chickenpox is available, its effect on postherpetic neuralgia is unknown.

The vaccine — made from a weakened form of the varicella-zoster virus — may keep chickenpox from occurring in nonimmune children and adults, or at least lessen the risk of the chickenpox virus lying dormant in the body and reactivating later as shingles. If shingles could be prevented, postherpetic neuralgia could be completely avoided. If you've already had chickenpox, the vaccine can't prevent shingles because the varicella-zoster virus is already in your body.

However, researchers in 2005 reported the results of a 10-year trial of a more potent version of the chickenpox vaccine. In what was called the Shingles Prevention Study, researchers reported that the vaccine reduced the incidence of shingles by about half compared with a placebo. And, in people who developed shingles, the vaccine significantly reduced the severity of the disease and lessened the risk of complications, such as postherpetic neuralgia. The vaccine is awaiting approval from the U.S. Food and Drug Administration.

After talking with your doctor, you may find the following over-the-counter medications ease the pain of postherpetic neuralgia:

• Capsaicin. This cream, made from the seeds of hot chili peppers, may relieve pain from postherpetic neuralgia. Capsaicin (Capzasin-P, Zostrix) can cause a burning sensation and irritate your skin, but these side effects usually disappear over time. Capsaicin cream can be very irritating if rubbed on nonaffected parts of your body, such as in your eyes. Follow the application instructions carefully.
• Topical analgesics and anesthetics. Aspirin mixed into an absorbing cream or nonprescription-strength lidocaine cream may reduce skin hypersensitivity. Don't apply cream containing lidocaine to your face. Your doctor may also recommend using a cream containing other medications.