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Post Herpetic Neuralgia: The Pain After Shingles

Last Reviewed on: October 14, 2004

"I feel like someone is putting a hot poker in my skin."

"I feel like hundreds of knives are digging and pulsing into my skin."

"I would cut off my thigh if it would make the pain stop."

"I feel like electric shocks are going all the way down my leg."

"It's very embarrassing, but I haven't been able to wear underwear for months."

These are some of the comments from my patients with post herpetic neuralgia.

What is Shingles?
Shingles is an acute infection caused by the varicella zoster virus, a herpes virus. It is sometimes referred to as zoster, and the pain after the infection is called post herpetic neuralgia (PHN). Shingles is caused by the reactivation of the virus that causes chicken pox. The chicken pox virus never completely leaves the body after the initial infection. Instead, it hides in nerve roots (small structures that make up the network that sends out thin nerves to all parts of the body). We don't know exactly what triggers the virus to reactivate, but often after a stressful event, such as illness, trauma, or extreme fatigue, the virus will become active and cause a new viral infection.

During its first infection with the chicken pox virus, the entire body is affected with fever and small pox-like lesions. When the varicella zoster virus reactivates, only a single nerve root, and the skin that is connected to that root, will be involved. Often, the first symptom is severe pain in a narrow band of the body such as the chest, groin, face, one eye, or the outer side of one leg. This may be accompanied by nausea, vomiting, and general sickness. After a few days, a linear, raised rash will develop—the classic shingles rash.

Making the Diagnosis
Because the pain from shingles starts before the rash appears, the diagnosis can be very difficult to make. I had a patient who developed severe pain in the left side of his chest and he was taken to the hospital to rule out a heart attack. The zoster rash erupted two days later. Another patient experienced excruciating burning in her vagina for two days, which worsened when walking, before developing a rash on her abdomen and back.

The main identifying feature of shingles is the distribution of the rash. Typically, the rash does not cross the midline of the body. It will therefore affect half of the face, or start in the middle of the back and travel across the side of the body to cover one half of the chest. A terribly painful and unfortunately common manifestation of shingles is ophthalmic zoster, in which the painful lesions affect the eye and can impair vision. When shingles affects the ear, it is called Ramsay-Hunt syndrome and can cause facial paralysis, hearing loss, and vertigo. The rash of shingles is often linear and consists of fluid-filled vesicles or pustules. It can be clustered together or patchy, and one difficulty with shingles diagnosis is that it is easy to confuse with other dermatitises, or inflammations of the skin. When the diagnosis is not quite clear, swabs of a fresh lesion can be sent to the lab for a DFA (direct fluorescent antibody testing), viral culture, or a Tzanck test.

How Did I Get It? Can I Give It to Someone Else?
Chicken pox is a common childhood illness. It is highly contagious, and is spread by airborne transmission of infectious respiratory droplets. Patients are contagious for two days before they develop the rash, and even after recovery, the virus never leaves the body and can reactivate at any time. Only people who have been exposed to chicken pox in the past can get shingles. Contact with a person who has shingles can cause chicken pox in those who were never exposed to it. This poses particular risk for pregnant women, because infants born to mothers who get chicken pox early in their pregnancy have a risk of developing birth defects, and mothers who become infected with chicken pox late in the pregnancy have a risk of delivering infants who are severely ill. Fortunately, someone with shingles cannot cause the virus to reactivate in a person who has already had chicken pox. In other words, someone with shingles cannot cause shingles in someone else.

Shingles can occur at any age, and 10 to 20 percent of people will develop shingles during their lifetimes. Up to 50 percent of people aged 80 or older can expect to have at least one episode of herpes zoster.

What Causes Shingles Pain?
Pain is the greatest problem with shingles. Post herpetic neuralgia is the term used to describe the pain after the rash has faded. PHN may develop days, weeks, or even months after the herpes zoster rash heals. People with PHN suffer from three types of pain:

• constant aching or burning
• lancinating pain (cutting or stabbing feeling)
• allodynia (heightened sensitivity to very minimal stimuli such as a light breeze)

This pain can be accompanied by loss of sensation in the affected area. Most patients report an increase in pain after exposure to cold, but not to heat. Some report numbness or tingling.

The exact cause of the pain associated with shingles is not yet understood. It is probably related to a number of factors, involving direct nerve injury from inflammation and perhaps hemorrhages that occurred during varicella zoster virus reactivation. Nerve fibers may be "turned up" to give a constant message of pain, and the inhibitory fibers can't turn off the signal. There also appears to be abnormal central nervous system processing of the pain signal.

How Long Will It Last?
Skin lesions associated with shingles slowly crust, scab, and usually heal within two weeks. New lesions continue to develop between four and six weeks after the initial outbreak. Post herpetic neuralgia is defined as pain lasting for three months or more after onset of herpes zoster infection. PHN is uncommon in young people and occurs with increasing frequency as people age, especially in those older than 60. Unfortunately, the pain from PHN can be lifelong, but in most cases, the duration of pain is measured in months, not years. Clinical features of the initial zoster infection, including increased fatigue and severe pain may be associated with an increased risk of prolonged PHN.

Treatment
The key to the treatment of shingles is to make the diagnosis early. This is difficult because the severe pain may precede the rash by a few days.

Oral antiviral drugs
Acyclovir, Famciclovir, and Valacyclovir are oral antiviral drugs that, in order to be effective, must be started within 48 to 72 hours of the onset of the viral vesicles. Treatment can reduce the period of viral shedding, accelerate the rate of healing, and perhaps shorten the duration of pain from the acute attack. Famciclovir and Valacyclovir have easier dosing schedules. They are taken three times a day for ten days. Acyclovir is dosed five times a day for seven days. None of these preparations, however, prevent the development of PHN, although there is some evidence that using them early may shorten the duration of pain.

Systemic corticosteroids
The use of systemic corticosteroids (Prednisone) is controversial. They may offer minimal initial benefits in reducing acute zoster pain, and they may improve quality of life in the month following the outbreak, but they have not been clearly shown to reduce the rate of development of post herpetic neuralgia. They may also cause some nausea, edema (swelling), and increase in blood-sugar levels.

Topical steroids
Some of my patients have found the use of topical corticosteroids to be helpful. Fluocinolone acetonide 0.025 percent ointment (not the cream or lotion) can provide some soothing relief, as can EMLA cream or Lidocaine HCL two percent gel.

Capsicin
Although Capsicin cream 0.025 percent (the same ingredient found in hot peppers) has been recommended, I have not found it helpful in my practice. It is applied three to four times daily to the affected area, but can cause a severe burning reaction. This may last for days before a possible numbing affect. If you use this cream, you must be careful to wash your hands after application.

Narcotic pain medications
Often, narcotic pain medications (e.g., morphine or Demerol) are needed for management of the initial pain and later for post herpetic neuralgia. Dosing may need to be increased as tolerance develops.

Tricyclic antidepressants
Low-dose tricyclic antidepressants may also be useful. Amitriptyline, nortriptyline, and desipramine can be started as soon as a diagnosis is made and maintained for three months. Low doses are used for the management of pain. Studies have shown that this treatment may reduce the number of patients who develop post herpetic pain. Unfortunately, the side effect profiles of these drugs do not make them safe for many elderly patients.

When the Pain Persists
When the pain persists for more than three months, it is then called post herpetic neuralgia, a type of neuropathic pain. The following therapeutic options may be tried prior to that time:

Gabapentin
Originally introduced as an anti-seizure drug, Gabapentin has been shown to be very effective in neuropathic pain, particularly PHN. Since it can be sedating, I often start at a low dose of 100 milligrams every eight hours, rather than the recommended dose of 300 milligrams every eight hours. Dosing is gradually increased up to a level of 3,600 milligrams per day, although some patients find relief at much lower total doses. In my practice, Gabapentin has made a dramatic difference in patients' quality of life. Unfortunately, it is quite expensive, and some insurance company prescription plans may not cover Gabapentin for this use.

Lidocaine patch
Another new therapy, the Lidocaine patch, is composed of an adhesive material with five percent Lidocaine and is applied to the most painful rash area. The patch can be applied for up to 12 hours in a 24-hour period. This can be a very effective measure especially for bad pain days, as it works very quickly, when it works. However, removal of the patch may exacerbate the pain.

When nothing seems to work
For extremely resistant cases of PHN, a referral to a pain specialist may be needed. New techniques of IV Lidocaine infusion to specific areas of the spine, or nerve blocks, or even surgery to sever the effected nerve, have been used.

Summary
Post herpetic neuralgia can be excruciating, disabling, and difficult to treat. The best hope for shortening the duration of pain after shingles is early diagnosis and treatment with antiviral medications. It is important to visit the doctor when the pain starts, rather than deciding to live with the pain for a few days. When the pain persists after the lesions have crusted and resolved, newer medications can be very helpful in reducing the pain. We cannot yet predict, however, who will have pain for weeks, months, for years, or for a lifetime, though we can do our best to help manage the pain.