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> Postherpetic NeuralgiaPostherpetic Neuraglia - PHNTo understand Postherpetic Neuralgia (PHN), we need to look at the subsequent viral disease called herpes zoster, or shingles. Shingles is a viral disease characterized by a painful rash of blisters that usually arises on one side of the body in a strip or ‘belt’ shape (zoster actually means ‘belt’ in Greek). Shingles is the result of the varicella zoster virus (VZV) which initially causes chicken pox. Although you cannot ‘get’ chicken pox more than once, the virus associated with it never leaves the body. As such, subsequent physical manifestations of the virus (shingles) are common, especially with older people. The varicella zoster virus resides in the nerve cells, even in it’s dormant state, much the same way the herpes simplex virus (HSV) does. Periodic outbreaks of shingles are the result of the virus manifesting on the skin for the purpose of spreading (shedding). Because the virus lives in the nerve cells, there is a chance that the manifestation of an outbreak can actually damage the nerve cells hosting the virus. When this happens, the nerve-brain communication becomes confused and can result in great pain, and can last months or even years. This condition is called Postherpetic Neuralgia. Herpes Zoster, or shingles, affects people above the age 50 much more frequently than younger adults or teens. Proportionally, PHN is also much more predominant in elderly people. It is estimated that over 1 million people contract herpes zoster each year, and of them almost 20% will experience postherpetic neuralgia. Of those 20% (or approx. 200,000), more than 90% are over the age of 50. Postherpetic Neuralgia Causes As mentioned the damage of nerve cells is what causes postherpetic neuralgia. The herpes zoster virus itself needs to travel through the nerve fibres to get to the skin’s surface. Once it reaches the skin, it manifests as a long strip of blisters and rashes called shingles, usually on one side of the body. Although painful and irritating, shingles usually disappears within a month. However, when topical blistering and subsequent skin damage takes place, the underlying nerve cells and nerve fibres can also be damaged. This is why postherpetic neuralgia and its symptoms persist months or years after the initial herpes outbreak. Damaged nerve cells can be repaired by the body under some circumstances. Below is a chronological list of the causes of postherpetic neuralgia: • Contraction of the varicella zoster virus (VZV) causing chiken pox, usually during childhood • Re-emergence of the dormant virus, manifesting on the skin as herpes zoster (shingles) • Damage to the nerve cells from the zoster virus using nerve fibres to reach the skin’s surface, resulting in pain, numbness or in extreme cases, paralysis (postherpetic neuralgia) PHN Symptoms Although related to herpes zoster, the symptoms of postherpetic neuralgia are very different. Where herpes zoster bears symptoms of pain and itchiness while a visible symptoms exist (rash, blisters), the symptoms of PHN occur after the visible symptoms have subsided. In many cases, people who suffer from a shingles outbreak will still experience some itchiness after the visible symptoms are gon – however, if pain and itchiness is still experienced weeks after the shingles have disappeared, you are probably suffering from PHN due to nerve damage. Here are some common symptoms of PHN: • Pain or burning sensation at the area of the skin where a shingles outbreak had previously occurred • Moderate to severe pain in the area over 3 months after the shingles outbreak has disappeared • Numbness at the area of a previous shingles outbreak • Hypersensitivity at the area of a previous shingles outbreak • Scarring of the skin where there was a previous shingles outbreak • In rare cases, muscle fatigue or restriction of muscle control at the affected area due to nerve/muscle damage Although PHN is defined as having moderate to severe pain for over 3 months after the visible symptoms of shingles have disappeared, if you are in extreme pain only weeks after, it is probably best to see your physician who can monitor the situation and test for any severe nerve damage. In many cases, simply wearing a loose shirt or pants is almost unbearable. Living your life day to day may be hampered by bouts of extreme in which case a physician will want to make a proper diagnosis earlier. Below are some treatment options that may be recommended by your doctor. Treating PHN There are many treatment options for PHN. In particular, many focus on the pain associated with PHN. It is important to mention that even some of the more extreme pain relieving treatments do not always eradicate all of the pain associated with PHN; in many cases, it simply lessens the pain to different degrees. Some of the more extreme treatment methods may help lessen the pain more effectively, but in most cases the preferred pain relief depends on the individual. Here are some common pain relieving treatment options. Natural Treatment: • Plant Extracts: It has been shown that some anthraquinones found in plant extracts can work as an antiviral agent. Natural products, sold over the counter, consist of various plant extracts which can inhibit shingles eruptions and therefore reduce the chance of getting PHN. These natural products can be found as topical creams, tablets and even oils which are rubbed on the skin (not necessarily the affected area) and enter the blood stream. Topical/Injected: • Lidocaine: comes in topical patches (like medicated band-aids) and is used for temporary pain relief. The patches can be quite large and cut to fit. Lidocaine is only available through prescription. Although lidocaine is not as effective as other treatments, it is sometimes preferred over ingesting prescriptions drugs or using topical steroids. • Corticosteroids: In some cases, doctors may recommend corticosteroid injections at the site of the pain. Corticosteroids can help reduce the pain, but constant injections are needed. Steroids do have adverse side effects; make sure you ask your doctor about them before agreeing to use this treatment method. Ingested Treatments: • Painkillers: there are painkillers that are sometimes prescribed for the pain of PHN. Examples include Percocet, Oxycontin and Ultram. These painkillers can be extremely addictive, and therefore should only be taken for shot periods. • Antidepressants: Used for various afflictions and symptoms, antidepressants have been used as a painkiller for many years. The active ingredients affect norepinephrine and serotonin levels in the brain. Antidepressants do not necessarily eradicate pain but they do make the pain more tolerable. Examples include Pamelor, Cymbalta and Norpramin. • Anticonvulsants: These are used to dull the electrical activity in the nervous system. When nerves are damage, the electrical activity can increase or decrease – antivonvulsants are used in the case of increased electrical activity (which causes muscle spasms). Separate anticonvulsants are prescribed depending on the type of pain experienced – burning or stabbing pain for example. • Antiviral Agents: Famciclovir, sold as Famvir, has been shown to reduce the frequency of shingles outbreaks, reduce the duration of shingles outbreaks and reduce the occurrence of complications (like PHN for example). It is believed that the active ingredient inhibits replication from the DNA level. Surgery/Machinery • TENS – TENS stands for transcutaneous electrical nerve stimulation and is used to reduce the pain of nerve damage for shingles, burns, accidents etc. With tiny electrodes attached to the affected area, turning the TENS unit on when experiencing pain gives the area a very small electrical impulse, affecting nerves and induces the production of endorphins which relieve pain. • Spinal Cord Stimulation: SCS works with the same principals of TENS. The difference being that the electrodes are surgically implanted. The unit can still be manipulated (on/off) so that it is only used when there is pain present. This treatment does not work for everyone and in many cases ‘trial runs’ will be used to test its efficacy on a particular patient. Preventing Postherpetic Neuralgia Although there are no preventative measures proven to work specifically for PHN, there are certain vaccines that may lessen the frequency of shingles outbreaks and PHN symptoms. The vaccine Varivax, used as a chicken pox vaccine, has been shown to significantly reduce the occurrence of shingles (by about 50% in some studies). The newer vaccine Zostavax (for shingles) has also been shown to reduce the frequency of shingles outbreaks. Reducing the frequency of shingles outbreaks will lessen the chances of getting PHN, as PHN is the result of shingles manifestations and its damage to the nerve cells. The vaccine has been approved for people over 60, the age which PHN predominantly affects. Preventative measures can also be taken during a shingles outbreak. People who have had shingles outbreaks can usually detect early symptoms. If an antiviral medication such as acyclovir is used on the rash early enough, studies have shown (inconclusively thus far) that this may reduce the chances of the shingles outbreak leading to PHN. Mayo Clinic: http://www.mayoclinic.com/health/postherpetic-neuralgia/DS00277 After
Shingles: AAFP (American Academy of Family Physicians: |
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