Shingles and Postherpetic Neuralgia

Shingles and Postherpetic Neuralgia

C. Peter N. Watson, MD, FRCPC

Introduction

Shingles (say: SHING-uhlz) is a painful condition most commonly associated with a localized skin rash. It commonly affects certain areas on one side of the body, such as the forehead, or the chest, which includes the nipple area. The rash takes the form of blisters on reddened skin, similar to the rash of chickenpox but very localized. In fact, it is the same virus.

Virtually all children will get chickenpox (varicella) unless they are vaccinated with the chickenpox (varicella) vaccine. It is common for children to be vaccinated now, so chickenpox is much less frequently seen than in previous decades. The body’s immune system normally fights off the virus, and although it is usually not a serious condition, it is very infectious. The virus (varicella zoster virus) never goes away, remaining in groups of nerve cells near the spinal cord or brain. Because the older population (60 years of age or older) was not vaccinated against chickenpox they are more prone to develop shingles.

Shingles develops when a person gets older or suffers from a chronic illness because the immune system becomes less effective at containing the dormant virus. So, it can re-erupt as a localized, very painful skin eruption. This can occur at any age but increases with age and may result in persistent pain. Although overall only 10 percent of adults of all ages will have significant pain at one month after the rash, at age 60 years or older, the risk of significant pain is 50 percent or greater.

The good news is that most people, although they will suffer significant pain and a nasty rash, will get better. The bad news is that the older you are, the more likely you are to have persistent problems such as persistent nerve pain (postherpetic neuralgia).

This article will focus on three approaches to this problem. The first is the treatment of the acute rash and pain of shingles (herpes zoster). The second will discuss the difficult problem of treating persistent nerve pain (postherpetic neuralgia). The third and most important aspect of this is the prevention of the whole process by vaccination.

Why shingles is becoming more common

As shingles is related to age, there will be many more cases and probably many more cases of persistent pain and eye complications. Other reasons for an increase in shingles may be that older people are no longer exposed to children with chickenpox (which may boost immunity to the virus). There are also more patients who are immunosuppressed from HIV, cancer and chemotherapy, and from autoimmune diseases (diseases like lupus when the body’s immune system attacks its own cells).

Possible signs and symptoms

  • A reddened blistering rash most commonly in the forehead and chest area but possibly occurring anywhere in the body.
  • Severe pain in the area of the rash although occasionally the pain can occur without a rash; this does not commonly occur.
  • The pain is often described as a combination of steady burning and shock-like shooting or stabbing pain.
  • There may be itching, loss of sensation or tingling in the area of the rash or pain.
  • The skin becomes very sensitive so even contact with clothing or even a light wind on the face will be very painful. If it is on the chest, it may be difficult to wear clothes.
  • The significant, persistent problems with shingles are persistent nerve pain, which can be very difficult to treat, and loss of vision due to infection of the eye, which also may result in having to have the eye removed.
  • It is important you see your doctor right away (within 72 hours or 3 days) if this painful rash happens because early treatment with medication may be critical at preventing complications. You will also need advice about what medication to take and what to do about the rash, which may respond to local treatment with creams or ointments.

Cause

The rash that children get from chickenpox and shingles is caused by the same virus (varicella zoster virus). Chickenpox is extremely infectious and spreads rapidly to your child’s contacts with other children. Shingles results from the persistence of the virus, which really never leaves your body but is contained by the immune system until you are older. Shingles may occur even in infants and children, but they virtually always had chickenpox first. It is unknown how long the effect of the chickenpox vaccine will be. It may result in fewer incidences of shingles, but this is really unknown at the present time. The lack of exposure to chickenpox with older people may result in more shingles because they may have been obtaining boosts of immunity from exposure to grandchildren with chickenpox. So, there is much unknown at the moment.

Nonetheless, the older population, especially age 60 and older, will remain, for many years, vulnerable to the reactivation of the virus and shingles. Usually when herpes zoster occurs, it conveys lifelong immunity unless it occurs at a very young age. It can recur in about 5% of patients and in half of those it affects the same area of skin as the original eruption, but this is unusual.

The importance of early diagnosis

The most important means of diagnosing shingles is the appearance of the rash and its location on one side of the body along with the presence of pain. Severe jabbing or burning pain in the forehead or mid-chest on one side may be the first sign of shingles. It is important to see your doctor to rule out other conditions and to receive treatment early. There should be an emphasis on diagnosing shingles early. For example, if you get this condition on a Friday, it would be important to get into see your doctor on that day and not wait until Monday or go to a walk-in clinic or the emergency department. Early treatment with medications, such as antiviral agents, can then be instituted. This may be critical in the first 72 hours from the onset of the pain or the pain and rash.

Therapeutic approaches to preventing and treating herpes zoster and postherpetic neuralgia

Three major approaches to dealing with stages of virus

There are three major approaches to dealing with the stages of this virus:

  1. Treatment of herpes zoster: When herpes zoster first occurs, a topical approach or skin preparation may be prescribed with a bandage covering the rash area (e.g. calamine lotion for itching, antibiotic ointments if there is evidence of secondary infection) or simply covering the weeping vesicular rash with something like JELONET and gauze. The JELONET (a paraffin-containing covering) prevents sticking of the crusting, weeping rash to the gauze).

    In terms of medication, it is important to use an antiviral agent such as famciclovir or valacyclovir. Sometimes intravenous acyclovir may be used in very severe cases, for example with central nervous system complications (meningitis, encephalitis) or with spread of the skin rash. Acyclovir orally has been used in the past but valacyclovir is a better choice since acyclovir has to be changed to valacyclovir to be effective and better blood levels are achieved with valacyclovir.

    Other approaches that have some scientific merit include use of the antidepressant pain reliever amitriptyline early to prevent the development of postherpetic neuralgia. Another approach that can be combined with amitriptyline is to use the anticonvulsant pain reliever gabapentin. It is important to give the patient a stronger analgesic if the pain is severe and not responding to acetaminophen or ibuprofen.

    It is important to be seen by your doctor again if the rash is severe and the pain persists. Treating acute pain well may help to prevent the persistent pain of postherpetic neuralgia. Antiviral drugs are important for relief of acute pain and rash healing and have to be given within 72 hours of the onset of the rash or even the onset of the pain to work most effectively. A recent review has shown that antivirals alone are not very effective for preventing severe postherpetic neuralgia.

  2. Treatment of postherpetic neuralgia (PHN): PHN is pain that persists even when the rash has healed or approximately one month. While there is gradual improvement over the first few weeks and months in this pain some people have persistent severe pain beyond this time, which can be extremely difficult to treat.

    The treatment choices at this stage are to use a gabapentinoid (gabapentin, pregabalin) and/or a tricyclic antidepressant (amitriptyline, nortriptyline). If itching is a prominent problem with pain, doxepin is a tricyclic antidepressant that has the strongest antihistaminic effect regarding the itch. It may be that the serotonin norepinephrine reuptake inhibitors (SNRIs) may be useful (duloxetine and venlafaxine are two examples).

    Some patients with postherpetic neuralgia will only respond to the use of a strong painkiller such as a strong opioid (morphine, oxycodone, hydromorphone, transdermal fentanyl). You need to be aware of possible side effects of these drugs. Common side effects of gabapentin include weight gain, swelling of the hands of the feet, tiredness, and dizziness. Common side effects with tricyclic antidepressants include dry mouth, drowsiness, and constipation. The most common side effects with opioids include drowsiness, nausea when first started, and constipation. There are other side effects, but these are the more common. Stool softeners and laxatives can be used for constipation. It is important to start with low doses and go slow in terms of increasing.

    There is an increasing tendency to use combinations of drugs to treat postherpetic neuralgia since each drug works in a different way on pain relieving mechanisms in the body. A few patients will be almost completely unresponsive and suffer severe pain. This pain can be difficult to treat and prevention of PHN is important if possible by using the zoster prevention vaccine (Zostavax).

  3. Zoster prevention vaccine: The zoster prevention vaccine is a live vaccine and is 14 times as potent as the chickenpox vaccine used for children. Because it is a live vaccine, it cannot be used in the population of patients with significant immunosuppression including patients with certain diseases, patients on immunosuppressant drugs for cancer (chemotherapeutic agents), and patients with other immunosuppressant diseases such as HIV and AIDS.

    The vaccine is moderately effective at preventing herpes zoster in that it will reduce the occurrence of herpes zoster by 50% and it is more effective at preventing postherpetic neuralgia, reducing postherpetic neuralgia by two-thirds. Thus, even if one gets herpes zoster, one is less likely to develop postherpetic neuralgia. The most common side effects of the vaccine include injection site reactions. It is generally well tolerated in the immunocompetent patient. It is currently approved in Canada for those over 50 years of age.

Summary of why vaccination is important

  1. Herpes zoster and postherpetic neuralgia are common and will increase as the population ages.
  2. Herpes zoster can change the nervous system, permanently destroying sites where painkilling drugs act.
  3. Herpes zoster can result in persistent, severe postherpetic neuralgia, which can persist for years and cause a significant impairment on quality of life.
  4. Herpes zoster, when affecting the forehead (a common site), can cause loss of the eye and/or blindness from infection of the eye.
  5. Herpes zoster can result in strokes when affecting the forehead as the inflammation can travel along small nerves to the blood vessels and cause inflammation and clotting in a brain artery. Although this information is preliminary, there may be an increased incidence of stroke and perhaps heart attacks from herpes zoster in younger patients.
  6. Herpes zoster infection can produce inflammation of the brain (encephalitis) and its coverings (meningitis).
  7. Herpes zoster can cosmetically scar the face and body if the rash is severe.
  8. The treatment of herpes zoster with antiviral agents and other drugs is probably not very effective particularly because of the frequent delay in getting to treatment early as antivirals, which have been found to be most effective, should be used within 72 hours or 3 days.
  9. Postherpetic neuralgia can be very difficult and sometimes impossible to relieve and lasts for years.