Post Herpetic Neuralgia (Shingles)
What is Shingles?
The medical term for shingles is “acute herpes zoster.” Shingles is a skin rash that develops on half of the body, in a belt-like pattern. The rash is usually on either the right or left side of the chest, starting in the middle of the back and wrapping around to the breast — but it can occur on any part of the body, such as the forehead and abdomen.
Most of the time, shingles is very painful. Sometimes the pain from shingles starts several days before the rash appears. When the pain starts before the skin rash, it can be very hard for doctors to make the correct diagnosis. Many patients have been told they have heart attacks, appendicitis, and migraine headaches before getting the correct diagnosis of shingles.
Fortunately, in most cases the pain of shingles gradually disappears over several weeks or months. Most people with shingles will have no pain or just a little pain one year after the rash.
What is Postherpetic Neuralgia?
If the pain from shingles does not go away, it is called Postherpetic Neuralgia (PHN). Only a small number of people with shingles develop PHN.
What Causes Shingles and Postherpetic Neuralgia?
Many people get “chicken pox” when they are children or even when they get older. The varicella zoster virus, a herpes type of virus, causes chicken pox. After the chicken pox heals, the varicella zoster virus moves from the skin along the nerves and into an area called “the dorsal root ganglia,” a part of the nerve, which lies next to the spinal cord. The virus stays there for many years in an inactive state.
The virus is usually inactive for decades. It can “wake up,” become active again and multiply when a person’s immune system becomes weakened. For most people who get shingles, the weakening of the immune system is not the result of a serious problem. It is true that shingles may be brought on by cancer, AIDS, or drugs that lower the immune system, but this happens in a very small group of patients. The most common reason for lowered immunity in shingles patients is being elderly and experiencing a stressful event, such as an illness in the family or emotional distress.
The reactivated virus begins to multiply within the dorsal root ganglia, which causes damage and swelling to this area of the nerve. This damage to the nerve causes the first pains of shingles. The virus then moves along the nerve to the skin, damaging the nerve and causing swelling as it goes. When the virus finally reaches the skin, it causes the shingles rash.
Can You Prevent Postherpetic Neuralgia?
Scientists have not found a treatment that prevents all patients with shingles from developing PHN. However, there are several treatments that some think might reduce the chances of developing PHN. These treatments are:
Antiviral Medication (such as acyclovir, valacyclovir or famciclovir): These medications kill the herpes virus during the shingles phase. Studies have shown that they shorten the time and pain of shingles. Because of this, antiviral medications probably reduce the chances of developing PHN after shingles, but this has never been totally proved.
Nerve Blocks: Nerve blocks are injections of numbing medications, called local anesthetics, into different nerves. Some doctors believe that doing several nerve blocks during the shingles phase will stop patients from developing PHN. Unfortunately, no studies have proven this. Nerve blocks may be a good treatment for the pain of shingles but should not be given to patients as a treatment to prevent PHN.
Tricyclic Antidepressants: One scientific study reported that giving the antidepressant amitriptyline (Elavil) during the shingles phase reduced the chance of developing PHN. Scientists need to do another study like this, with the same results, before everyone with shingles is given this type of medication.
Herbs and Other Medicinals: Many patients visit their doctors and ask about cures or treatments they have heard about in medical magazines, on the Internet, or from friends or relatives. Doctors might discourage their patients from using some of these treatments if there could be any harmful effects. Patients should not expect that any of these treatments will prevent them from getting PHN — the sad fact remains that no treatment given during the shingles has been shown in scientific studies to prevent PHN.
Who Gets Shingles and Postherpetic Neuralgia?
Age is an important factor in determining who gets shingles and PHN. The older you are, the greater chance you have of developing shingles. And, the older you are when you get shingles, the greater chance you have of developing PHN.
Recently, a good scientific study showed that older people with a neuropathy (nerves of the body that are not working correctly, usually due to old age or diabetes) are more likely to develop PHN after shingles. It is interesting that most people in this study who had a neuropathy before they got shingles did not know they had a neuropathy — they did not have any symptoms. Therefore, having a neuropathy, even if it is not causing symptoms, may increase the chances of getting PHN.
Other studies have suggested that the more severe and painful the shingles rash is, the greater the chance of long-lasting PHN pain. Also, some studies have concluded that people who do not cope well with stress and pain may have worse PHN than others who cope better.
Pain from Shingles and Postherpetic Neuralgia
Patients often describe the pain from shingles as a horrible, unbearable pain in the area of the rash. Each patient may experience different types and degrees of pain. The words used to describe the pain include sharp, electric-like jabs, burning, throbbing, aching, and skin sensitivity.
Most patients who develop the chronic pain of PHN say that the pain is less severe than the shingles pain, but it may still be intense. Like shingles pain, the pain of PHN can be described as sharp, electric-like jabs, burning, throbbing, aching, and skin sensitivity, and the pain is different from patient to patient. Patients might also have intense itching in the painful area. The pain of PHN may spread beyond the original shingles rash, and often includes several inches above the rash area. Some patients have severe skin sensitivity (called “allodynia”) that can be very disabling, especially if the sensitive area is on the chest, trunk, or limbs, making the touch of clothing unbearable.
Other Symptoms and Problems Associated with Shingles and Postherpetic Neuralgia
People suffering from shingles or PHN may develop depression, anxiety, and sleeping difficulties because of the severe pain. The patient should tell his or her doctor about these problems so they may be treated.
Also, some patients describe a “sagging of the muscles” in the area of the shingles. When doctors examine the region, a loss of muscle tone is seen. This might be caused by damage of some nerves that control the muscle tone in the area of the shingles.
Diagnosing Postherpetic Neuralgia
PHN is simple for a doctor to diagnose, without any laboratory testing. Any patient who develops a chronic pain at the site of the shingles rash has PHN. The area of pain of PHN may be smaller than the shingles rash or may spread several inches larger than the shingles rash.
Treatment for Shingles
Antiviral Medication (such as acyclovir, valacyclovir, and famciclovir): For most patients with shingles, oral antiviral medication should be prescribed for 7 days. The earlier this medication is taken, the better the chance of stopping the virus from causing more damage to the nerves. Early treatment with antiviral medication can lessen the intensity and duration of shingles pain (but, as mentioned above, there is no definite proof that these medications will stop the patient from getting PHN). Once the rash has healed, the patient should stop taking antiviral medication.
Steroids (such as prednisone): Some studies have shown that early treatment with a short course (usually 1-2 weeks) of steroids can decrease the intensity and duration of pain associated with acute shingles.
Nerve Blocks: Pain specialists can inject numbing medications (called “local anesthetics”) directly into certain nerves to help with shingles pain. There is evidence in the literature regarding the early use nerve blocks in order to reduce the chances of developing PHN. If nerve blocks are successful but not long lasting, there are procedures that can be performed such as radiofrequency neurolysis that can be extremely successful in certain conditions.
Opioid Medication (narcotics): Opioid medications, such as morphine, oxycodone, codeine, hydromorphone, and methadone, can provide good pain relief without side effects for many patients. In most cases, there should be no concern about developing “addiction” when these drugs are used to treat the severe pain of shingles. Patients can be safely taken off of the narcotic medication if it is no longer needed.
Tricyclic Antidepressants (such as amitriptyline [Elavil] and nortriptyline [Pamelor]): One study has shown that giving tricyclic antidepressants during the early shingles phase can help reduce the pain and help reduce the chance of developing chronic PHN pain. When used in this way, tricyclic antidepressants are not given to treat any kind of depression — they are prescribed for pain relief and perhaps to reduce the chance of getting PHN.
Recommended Treatments For Post-herpetic Neuralgia
There is good and bad news about treating PHN. The bad news is that there are no treatments that reverse the nerve damage caused by shingles, and there are no treatments that can improve the healing of the nerves. The good news is that there are many different treatments available for the pain of PHN. Some treatments work better for some patients than for others, and some cause bad side effects in some patients but no side effects in others. So each patient with PHN should be tried on a variety of medications until the drug or combination of drugs is found that gives good pain relief with no or little side effects.
It is very important that doctors start all oral medications (that is, medications taken by mouth in pill, tablet or syrup form) at a low dose and then gradually increase the dose until pain is relieved or side effects occur. This gradual increase in dosage, called “titration,” is important because every patient with PHN is different and each may respond to a different dose of each medication.
Topical Lidocaine Patch: This is a new medication that can be used to treat the pain of PHN. As many as 3 patches (each about the size of an adult hand), can be placed directly over the painful area of the skin. The patches are applied for 12 hours on the skin and then removed from the skin for 12 hours. Lidocaine patches are a unique treatment because they can reduce the pain and skin sensitivity of PHN without causing any blood level of lidocaine. The medication acts locally in the skin’s damaged nerves. Within 1-2 weeks, most patients begin to notice relief.
Anticonvulsants (such as gabapentin [Neurontin] and carbamazepine [Tegretol]): Drugs used to treat epilepsy and seizures have been used for many years to help relieve the pain of PHN. In recent years, the anti seizure drug gabapentin (Neurontin) has become available, and it is widely prescribed for PHN by pain specialists today (often as the first medication tried). It has been shown in a large study to be effective and safe for many patients with PHN, with few side effects. Also, gabapentin does not interact with any other medication, making it a good choice for many patients who are taking several different medications at once.
Carbamazepine (Tegretol) is an older anti epilepsy drug that has been used for PHN pain. This medication helps some patients, but many others complain of side effects, such as mental changes and dizziness. Patients taking this drug need regular blood tests.
Many other anticonvulsant medications are available, and doctors may try using others to treat PHN.
Tricyclic Antidepressants (such as amitriptyline [Elavil], nortriptyline [Pamelor], desipramine, doxepin): Up until the past year or so, tricyclic antidepressants (TCAs) were probably the most widely used medicines to treat the pain of PHN. Many studies have shown that some patients with PHN have good pain relief from these drugs. However, many patients also complain of side effects, such as severe dry mouth, constipation, sedation, trouble thinking, and dizziness.
Newer antidepressant drugs, such as fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft), might be helpful for some patients with PHN. These medications usually have fewer side effects than the tricyclic antidepressants, but studies have found that they are generally less effective for pain.
Opioids (such as oxycodone, morphine, methadone): For some patients, opioid medications greatly relieve the pain of PHN without serious side effects. When using these drugs as the main pain medication, it is important that the doses be given “around-the-clock” to keep a certain amount of the drug in the bloodstream.
The use of opioid medications for chronic pain continues to be controversial. Pain specialists now agree, however, that some patients greatly benefit from taking opioids. When used properly, the drugs can be taken long-term for pain management with few side effects. It is very rare that patients become addicted to opioid pain medication. Fear of addiction should not prevent a doctor from prescribing opioids for pain in appropriate cases. Patients can be safely taken off of opioid medications without withdrawal symptoms.
Nondrug Therapies: Like other kinds of patients with chronic pain, patients with PHN may benefit from many non-drug treatments. These include rehabilitation therapies and psychological therapies (such as relaxation therapy and biofeedback). Also, patients may get pain relief from therapies that stimulate the nerves, such as TENS (Transcutaneous Electrical Nerve Stimulation). TENS units are small devices that send very small amounts of electrical current to the skin through electrodes that are stuck to the skin. In some refractory severe cases of PHN, spinal cord stimulation can be an effective form of pain control.