Postherpetic neuralgia (PHN) is a painful condition caused by the varicella zoster virus, in a dermatomal distribution after an attack of herpes zoster or shingles. The dermatomal distribution is the area that is governed by a particular sensory nerve.
In laymen terms, postherpetic neuralgia is a painful condition that persists after a shingles episode is over. The sharp and shooting pain of PHN is in the same area as that of pain and rash of shingles and results from the damage to nerve fibers during the shingles infection.
PHN is generally not considered life threatening, though the condition can lead to insomnia, weight loss, depression and even disability in some cases. Patients may also become hypersensitive to even a very light touch or pressure on the skin, such as when touched by hand, a piece of cloth or even a brush of air.
According to studies, one of every five patients with shingles or herpes zoster is inflicted with an episode of PHN. Adults above the age of 50 and especially those who are in the immunocompromised state are at a greater risk of developing PHN.
Research reveals that amongst those over the age of 55, one in every four will develop PHN. In those above 70, 3 out of every four persons are likely to be inflicted. Overall, roughly 20 percent of those diagnosed with shingles usually develop an episode of PHN.
Causes of Postherpetic Neuralgia
Postherpetic Neuralgia presents itself as the manifestation of the virus varicella, the same virus that causes chicken pox. It may lie dormant in the body after an episode of chickenpox and present itself a number of years later.
PHN primarily results when nerve fibers are damaged during a case of shingles. Since damaged fibers are unable to send messages from the skin to the brain, the messages become confused and exaggerated. This in turn causes chronic and severe pain that lasts for months or even years in the area where shingles first developed.
Management of Postherpetic Neuralgia
Clinical trials divide the medications prescribed for postherpetic neuralgia into four broad categories:
1) Tricyclic antidepressants (TCAs): This is normally the first drug prescribed for relief to a patient of postherpetic neuralgia. The most common ones prescribed include:
2) Anticonvulsants: Used in conjunction with TCAs, certain anticonvulsants also provide relief for postherpetic patients since both seizures and pain involve abnormally increased firing of nerve cells. Some of the commonly used ones are:
· Other anti-neuropathic agents
3) Opioids: Opioids are morphine like drugs, typically defined as strong pain medications prescribed for all types of pain. Examples of opioids include:
4) Topical local anesthetics: Local anesthetics are also given to be applied directly on the area affected by postherpetic neuralgia. These are available as creams, gels, sprays or as a patch. These include:
· Lidocaine patch (Lidoderm)
· Capsaicin cream
· EMLA cream