After a chickenpox infection, the varicella-zoster virus can remain dormant (asleep) in nerve cells. Years later, the virus may become active again. Researchers do not know exactly what triggers reactivation of the virus.
The reactivated virus travels along the nerves, causing pain and producing a rash or blisters on the skin. The shingles rash and pain usually occur in a band on one side of the back, chest or neck, or in a cluster on one side of the head or face.
Shingles typically goes away within a few weeks, with no lasting effects. Sometimes, however, the shingles virus damages nerves, causing pain and other sensations to linger after the shingles rash has healed. This is referred to as postherpetic neuralgia (PHN).
PHN symptoms vary from person to person, but may include significant pain, tingling, numbness or unusual skin sensitivity in the area where the shingles rash occurred. PHN symptoms often lessen over time time, but can last for months or even years.
PHN can affect every aspect of your life – your relationships, work and leisure activities. Fortunately, you can take steps to help you feel better and manage your symptoms. You may benefit from one or a combination of treatments, including physical therapy, medication, and cognitive behavioral therapy. Your health care provider can help you design a treatment plan that works for you.
WHO IS AFFECTED
Only people who have had chickenpox and, later, shingles can get PHN. Anyone can develop PHN following shingles, but certain factors may increase the risk:
- Age – The chance of getting PHN is related to the age at which a person has shingles. About 30% of people who experience shingles after age 60 also develop PHN, while only about 10-20% of all people with shingles do.
- Type of shingles symptoms – PHN is more likely to occur if the shingles rash and pain are severe, or if shingles affects the forehead and eyes.
- Other conditions — People with suppressed immune systems, such as those on chemotherapy or other immunosuppressive medications (e.g., cortisone) or those with HIV/AIDS may be more prone to PHN.
It is important to seek treatment for shingles early. Starting treatment within two to three days of the appearance of the shingles rash may reduce the length and severity of symptoms and lower the risk of PHN.
Source: National Pain Foundation
CAUSES OF POSTHERPETIC NEURALGIA
To understand PHN, it helps to know a bit about the nervous system. The nervous system is composed of the brain, the spinal cord, and nerves. Nerves are like electric cables that are distributed throughout the body. Nerves help carry messages to the brain about what the body is experiencing. Some nerves, for example, relay how painful, hot or cold something is, while other nerves sense pressure or just light touch.
PHN results when the shingles virus injures nerves that sense pain, temperature or touch. The damaged nerves do not function normally, but instead send faulty or amplified pain messages to the brain. This causes a person to feel chronic, often severe, pain or other abnormal sensations in the area affected by shingles.
Symptoms of Postherpetic Neuralgia
The signs and symptoms of PHN typically occur only in the area affected by shingles and include:
- Pain (may be sharp, stabbing, throbbing, burning or aching)
- Numbness, tingling or itching
- Headaches if the shingles affects the head or face
- Rarely, muscle weakness or paralysis, if PHN affects the nerves that control muscles
Some people also experience allodynia. Allodynia is an unusual sensitivity to touch, slight temperature changes (heat or cold) or other normally non-painful stimuli. For example, a person may be overly sensitive to a light breeze or the touch of clothing.
If you have continued pain or unusual sensitivity to touch or temperature changes following a case of shingles, see your health care provider promptly. There is no specific test or procedure for PHN, but your health care provider can gather important information by talking to you and doing a physical examination. Your health care provider may ask about your general health, medical history, occupation and symptoms. He or she may order tests to rule out other causes for your symptoms.
INJECTIONS AS A TREATMENT
Injections of corticosteroid medications into the area around the spinal cord sometimes provide pain relief. Injections carry risks and should be performed by a qualified physician (often, an anesthesiologist familiar with PHN). Discuss the risks and benefits of injections with your health care provider.
Source: National Pain Foundation