Diseases

The majority of patients who are diagnosed with PHN are done by follow-up of a shingles infection or by the patient's history of a recent shingles infection. The pain is located in the same nerve distribution (dermatome) area, usually on only one side of the person's body where the shingles lesions occurred.

Only approximately 9%-15% of patients who get shingles develop PHN. For those few patients who develop PHN, the length of time that PHN lasts is variable; the majority of PHN patients have discomfort lasting one to two months. About one-third of PHN patients have symptoms that last about three months, and about one-fifth last a year or longer.

If shingles can be prevented, then PHN can be prevented. Fortunately, the vaccine Zostavax is about 70% effective in preventing shingles. The CDC recommends that everyone older than 60 years of age get the vaccine; in 2011, the FDA approved the vaccine for people aged 50 and above. The CDC states, "Zostavax should not be given to pregnant women, persons with a primary or acquired immunodeficiency, or to persons with a history of anaphylactic reaction to gelatin, neomycin, or any other component of the vaccine. Herpes zoster vaccine can be administered simultaneously with other indicated vaccines."

The main symptom is pain. The pain can be severe (allodynia - pain due to a stimulus that does not usually provoke pain); patients describe the pain as burning, sharp, jabbing, deep, and aching. Often, the patient feels increased pain when any pressure, even clothing, touches the area. Some patients describe itchy skin and weakness or paralysis of the area.

PHN itself is a complication of shingles. A serious complication of PHN is addiction to pain medications. Some patients may have an inability to live a normal lifestyle (unable to exercise) because of constant pain, while others have sleep and activities limited or even prohibited by touching the affected area, including just having contact with their own clothing. Patients taking opioids may become very constipated. In a few cases of PHN, muscle weakness can be an additional complication.

Age is a high risk factor for PHN; the older a person when he or she develops shingles, the more likely it is that the person will develop PHN. People over 60 years of age have about a 60% chance while people 70 or older have about a 75% chance of developing PHN after getting shingles. Another risk factor is family; those people who have close relatives who developed PHN are at a higher risk than people with no family history of PHN.

Postherpetic neuralgia is thought to be caused by the damage or alteration of nerves that register pain, pressure, and other sensory nerves (for example, touch) that occur when the reactivated HZ viruses travel down nerves to the skin. This process first begins when the virus causes chickenpox in an individual; the viruses can infect various dorsal root ganglia (nerve cells) as the chickenpox subsides. These viruses then can be reactivated, usually decades later, and produce shingles lesions. The reactivation of HZ is thought to be due to a stress on the body from either another infection or a immunocompromised state (for example, some patients undergoing treatments for leukemia) that allows the HZ to escape the dorsal root cells. PHN does not occur in everyone who gets shingles; about 9%-14% have symptoms after one month post-shingles and about 5% have PHN three months post-shingles.

Postherpetic neuralgia (also termed PHN) is a condition of recurring or persistent pain in an area of the body that has undergone an outbreak of herpes zoster virus (HZ), also known as the varicella zoster virus, commonly termed shingles. It usually begins after shingles lesions (blisters) begin to crust over and heal but may occur in some patients who do not produce lesions. Some investigators suggest the pain has to be present for three months to be termed PHN.

For the majority of patients who develop PHN, the prognosis is good although they may have to take pain medications for about one to three months. For others, the prognosis is fair to poor if the pain is severe, lasts longer than three months, or markedly reduces their quality of life. PHN occasionally results in permanent nerve damage; however, the disease is not fatal.

Treatment is individualized for each patient; there is no treatment that is effective for all PHN patients, so clinicians often use two or more of the drug categories with examples listed below:

• Lidocaine skin patches ([Lidoderm] small, bandage-like patches applied to painful areas)
• Capsaicin skin patches ([Capsagel, Salonpas] applied in a doctor's office by trained staff)
• Opioids (tramadol [Ultram], oxycodone [OxyContin], morphine)
• Anticonvulsants (pregabalin [Lyrica], gabapentin [Neurontin]) have been shown to lessen the pain of PHN probably by stabilizing abnormal electrical activity in your nervous system.
• Antidepressants (venlafaxine [Effexor], duloxetine [Cymbalta]) are often prescribed in lower doses than for depression.

Because some drugs (opioids) can be addictive and because some patients may need long-term treatments (over one year), consultation with a pain-management specialist may be advised. Some individuals claim tamanu oil rubbed into the affected may reduce the symptoms of PHN. One small study and a few case reports indicate that acupuncture can be helpful in relieving the pain of PHN. Infrequently, other methods are used. TENS (transcutaneous electrical nerve stimulation) devices are designed to interrupt the body's pain sensations while nerve blocks (short-term chemical nerve sensation blockade) and nerve ablation (surgically cutting a nerve) are also used. Results vary but the methods often do not give lasting pain relief.