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Postherpetic neuralgia (PHN) is a painful condition caused by the varicella zoster virus in a dermatomal distribution (the area governed by a particular sensory nerve) after an attack of herpes zoster (HZ) (commonly known as shingles), usually manifesting after the vesicles have crusted over and begun to heal.
There are a number of treatment options for PHN including antidepressants, anticonvulsants (such as gabapentin or pregabalin) and topical agents such as lidocaine patches or capsaicin lotion. Opioid analgesics may also be appropriate in many situations. There are some sporadically successful experimental treatments, such as rhizotomy (severing or damaging the affected nerve to relieve pain), and TENS (a type of electrical pulse therapy).
Additional recommended knowledge
Postherpetic neuralgia is thought to result after nerve fibers are damaged during a case of Herpes Zoster (also known as Shingles). Damaged fibers cannot send electrical signals from the skin to the brain as they normally do, and may be erratic or exaggerated, causing chronic, often excruciating pain that may persist or recur for months — or even years — in the area where shingles first occurred.
Each year, approximately 1,000,000 individuals in the United States develop shingles, or herpes zoster. Approximately 20 percent of these shingles patients, or 200,000 individuals, go on to suffer from PHN, or post-herpetic neuralgia.
Signs and symptoms
When to seek medical advice
It is strongly recommended by professionals that patients 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. In addition, amitriptyline may reduce the risk of developing PHN.
If patients do develop postherpetic neuralgia, they are also advised to see their doctor immediately. They may have to work with their doctor and sometimes other specialists such as neurologists to try a variety of treatments before they find something that helps.
Lab and imaging studies
Treatment for postherpetic neuralgia depends on the type and characteristics of pain experienced by the patient. Possible options include:
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 on its own within five years.
Caution: Although often recommended, Transcutaneous electrical nerve stimulation (TENS) may be contraindicated for Postherpetic Neuralgia, as there is concern that, if turned up too high and/or left on the Trigeminal nerve too long, it may stimulate Postherpetic neuralgia rather than relieving it. One indicator of overuse of TENS with Postherpetic neuralgia patients involves significant earwax production as a result of overstimulation of the Trigeminal nerve, followed by tinnitus and intense Postherpetic neuralgia pain that increases over time. Note: If a decision is made to use TENS on the Trigeminal nerve of Postherpetic neuralgia patients, the unit should never be turned high enough to move the muscles (a recommendation in all types of TENS use, according to the UK department of Health.)
In 1995, the Food and Drug Administration (FDA) approved the vaccine to prevent chickenpox. Its effect on PHN is still 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.
Recently, Merck has tested a new vaccine (Zostavax) against shingles. This vaccine is a more potent version of the chickenpox vaccine. Evidence indicates that the vaccine reduced the incidence of shingles by 51 percent. Additionally, the vaccine reduced the incidence of PHN by two-thirds compared to placebo. However, the vaccine's protective effects diminished over the three years that most patients were followed. In December 2005, an FDA advisory committee unanimously agreed that the vaccine is safe and effective for persons over 60 years old. This was followed on 2006-05-26 by the FDA formally approving the use of the vaccine for that same age group. Further studies may demonstrate if there is benefit in patients 50-59 years old and if a booster dose is recommended.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Postherpetic_neuralgia". A list of authors is available in Wikipedia.|