What is Post-Herpetic Neuralgia?
Postherpetic neuralgia (also referred to as PHN) is a condition of recurring or persistent pain in an area of the body that has undergone an outbreak of of shingles, which is caused by the chickenpox (herpes zoster) virus. 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. Postherpetic neuralgia affects nerve fibers and skin, causing burning pain that lasts long after the rash and blisters of shingles disappear.
What are the Causes?
If you have had chickenpox, the virus remains in your body for the rest of your life. As you age or if your immune system is suppressed, such as from medications or chemotherapy, the virus can reactivate, often decades later, causing shingles. Postherpetic neuralgia is caused by the damage or alteration of nerves that register pain, pressure, and other sensory nerves (for example, touch) that occur during an outbreak of shingles when the reactivated viruses travel down nerves to the skin. Damaged fibers can’t send messages from your skin to your brain as they normally do. Instead, the messages become confused and exaggerated; this causes chronic, often excruciating pain that can last months — or even years.
In addition, when you have shingles, you might be at greater risk of developing postherpetic neuralgia as a result of:
- Age. You’re older than 50.
- Severity of shingles. You had a severe rash and severe pain.
- You have a chronic disease, such as diabetes.
- You had shingles on your face or torso.
What are the Symptoms?
The main symptom is pain, which can be severe. Specific signs and symptoms may include:
- Pain that lasts 3 months or longer after the shingles rash has healed. The associated pain has been described as burning, sharp and jabbing, or deep and aching.
- Sensitivity to gentle touch. People with the condition often can’t bear even the touch of clothing on the affected skin (allodynia).
- Itching and numbness. Less commonly, postherpetic neuralgia can produce an itchy feeling or numbness.
The signs and symptoms of postherpetic neuralgia are generally limited to the area of your skin where the shingles outbreak first occurred — most commonly in a band around your trunk, usually on one side of your body. However postherpetic neuralgia is also common in people whose shingles occurred on the face.
The risk of postherpetic neuralgia increases with age, primarily affecting people older than 60.
What are the Treatments?
Although there is no cure, treatment to ease symptoms can be individualized for each patient; there is no single treatment that is effective for all PHN patients, and therefore in many cases it takes a combination of treatments to reduce the pain.
For most people, postherpetic neuralgia improves over time. Your doctor will examine your skin, possibly touching it in places to determine the borders of the affected area. In most cases, no tests are necessary.
Specific treatments include:
Lidocaine skin patches, such as Lidoderm, are small, bandage-like patches that contain the topical, pain-relieving medication lidocaine and are applied to painful areas)
Capsaicin skin patches, such as Capsagel and Salonpas, are applied in a doctor’s office by trained staff)
Anticonvulsants, such as pregabalin (Lyrica) and gabapentin (Neurontin) have been shown to lessen the pain of PHN probably by stabilizing abnormal electrical activity in your nervous system.
Antidepressants, such as venlafaxine (Effexor), duloxetine (Cymbalta) are often prescribed in lower doses than for depression.
Common side effects of these medications include drowsiness, dry mouth, lightheadedness and weight gain.
Some people may need prescription-strength pain medications containing tramadol (Ultram, Conzip), oxycodone (Percocet, Roxicet, Xartemis XR) or morphine. Opioids can cause mild dizziness, drowsiness, confusion and constipation. They can also be addictive. Although this risk is generally low, discuss it with your doctor.
Tramadol has been linked to psychological reactions, such as emotional disturbances and suicidal thoughts. Opioid medications should not be combined with alcohol or other drugs and may impair your ability to drive.
Although steroids are sometimes injected into the spine (intrathecal) for postherpetic neuralgia, evidence of effectiveness is inconsistent. A low risk of serious side effects, including meningitis, has been associated with their use.