Postherpetic neuralgia is a painful condition that affects the nerve fibers and skin. It is a complication of shingles, and shingles is a complication of chicken pox.
If the pain caused by shingles continues after the bout of shingles is over, it is known as post-herpetic neuralgia (PHN). It is estimated that about 1 in 5 patients with shingles will go on to have PHN.
Neuralgia is neuropathic pain that occurs along the course of a nerve. It tends to happen when an irritation or damage to a nerve alters its neurological structure or function.
The sensation may be of intense burning or stabbing, and it may feel as if it is shooting along the course of the affected nerve.
Neuropathic pain comes from inside the nervous system. It is not caused by an outside stimulus, such as an injury. People often refer to it as a pinched nerve, or trapped nerve. The nerve itself sends pain messages because it is either faulty or irritated.
Treatment will depend on the type of pain as well as the patient's physical, neurological, and mental health.
Painkillers: These may include tramadol (Ultram) or oxycodone (OxyContin). There is a small risk of dependency.
Anticonvulsants: The pain of PHN can be lessened with anticonvulsants, because they are effective at calming nerve impulses and stabilizing abnormal electrical activity in the nervous system caused by injured nerves. Gabapentin, or Neurontin, and pregabalin, also known as Lyrica, are commonly prescribed to treat this type of pain.
Steroids: A corticosteroid medication can be injected into the area around the spinal cord. Steroids should not be used until the shingles pustular skin rash has completely disappeared.
Lidocaine skin patches: Lidocaine is a common local anesthetic and antiarrhythmic drug. Applied to the skin, it can relieve itching, burning, and pain from inflammation. The patches can be cut to fit the affected area.
Antidepressants: These affect key brain chemicals, such as serotonin and norepinephrine, which influence how the body interprets pain. Examples of drugs that inhibit the reuptake of serotonin or norepinephrine are tricyclic antidepressants, such as amitriptyline, desipramine (Norpramin), nortriptyline (Pamelor), and duloxetine (Cymbalta).
Transcutaneous electrical nerve stimulation (TENS)
This treatment involves placing electrodes over the areas where pain occurs. These emit small electrical impulses. The patient turns the TENS device on and off as required.
Some people find that TENS relieves pain, while others do not. Its effectiveness has not been confirmed by research.
Spinal cord or peripheral nerve stimulation
These devices offer a safe, efficient, and effective way to relieve many types of neuropathic pain conditions. Similar to TENS, they are implanted under the skin along the course of peripheral nerves. Before implantation, doctors do a trial run using a thin wire electrode to determine patient response.
The spinal cord stimulator is inserted through the skin into the epidural space over the spinal cord. The peripheral nerve stimulator is placed under the skin above a peripheral nerve. As soon as the electrodes are in place, they are switched on to administer a weak electrical current to the nerve.
Experts believe that by stimulating the non-painful sensory pathway, the electrical impulses trick the brain into "turning off" or "turning down" the painful signals, resulting in pain relief.
Symptoms are usually limited to the area of skin where the shingles outbreak first occurred and may include:
- occasional sharp burning, shooting, jabbing pain
- constant burning, throbbing, or aching pain
- extreme sensitivity to touch
- extreme sensitivity to temperature change
In rare cases, if the nerve also controls muscle movement, there may be muscle weakness or paralysis.
Symptoms may make it hard to carry out some daily activities, such as bathing or dressing. PHN may also cause fatigue and sleeping difficulties.
PHN is a persistent nerve pain that can occur as a result of shingles. Shingles is caused by the herpes varicella-zoster virus, the virus known to cause chickenpox. After a person recovers from chickenpox, the virus remains inactive in the nervous system.
Later in life, the herpes varicella-zoster virus may become reactivated, causing shingles. Shingles is an infection of a nerve and the area of skin around it. Usually the nerves of the chest and abdomen on one side of the body are affected.
The nerve damage that is caused by shingles disrupts the proper functioning of the nerve. The faulty nerve becomes confused and sends random, chaotic pain signals to the brain. This can lead to a throbbing, burning pain along the nerve.
Experts believe that shingles causes scar tissue to form next to the nerves, creating pressure. This causes the nerves to send inaccurate signals, many of them pain signals, to the brain. It is unclear why some patients go on to develop PHN.
A number of natural and alternative therapies have been recommended for PHN.
- vitamin C, but more research is needed to confirm this
- homeopathic treatment, but scientific research has not confirmed this
- acupuncture, which scientists are currently reviewing for effectiveness
- herbal remedies
- wearing comfortable clothing made from cotton or silk
- using cool packs to soothe the pain
Treatments using traditional Chinese medicine will vary according to whether the PHN is a "wet" type, a "heat" type, or a "wind" type.
Researchers are still investigating how effective some of these therapies may be.
As PHN is a complication of shingles, it is generally easy to diagnose. If the symptoms persist after shingles, or if they appear after the symptoms of shingles have cleared up, then the patient might have PHN.
Early treatment is key for preventing PHN. Seeking medical help as soon as signs or symptoms of shingles appear can greatly reduce the chances of developing neuralgia.
Aggressive treatment of shingles within 2 days of the rash appearing helps reduce both the risk of developing subsequent neuralgia and the length and severity if it does.
The only effective way of preventing PHN from developing is to be protected from shingles and chicken pox through vaccination. The varicella vaccine protects against chickenpox, and varicella-zoster vaccine against shingles.
The Varivax vaccine is routinely given to children aged 12 to 18 months to prevent chickenpox. Experts recommend it also for adults and older children who have never had chickenpox. The vaccine does not provide total immunity, but it considerably reduces the risk of complications and severity if disease occurs.
The Zostavax vaccine can help protect adults over 60 who have had chickenpox. It does not provide 100 percent immunity, but it does considerably reduce the risk of complications and severity of shingles.
Experts recommend that people aged over 60 years should have this vaccine, regardless of whether or not they have had shingles before. The vaccine is preventive, and it is not used to treat people who are infected.
The following people should not have the shingles vaccine:
- Those who have had a life-threatening reaction to gelatin, the antibiotic neomycin, or any other shingles vaccine component
- People who have a weakened immune system
- Patients receiving steroids, and those who are undergoing radiotherapy, chemotherapy, or both
- Those with a history of bone marrow or lymphatic cancer
- Patients with active, untreated tuberculosis (TB)
A person with a mild cold may take the vaccine, but not those who are moderately or severely ill. These people should wait until they are recovered.