Postherpetic Neuralgia

Why shingles pain can persist

Shingles is caused by reactivation of the varicella-zoster virus, which stays dormant in nerve roots after chickenpox. When it reactivates, it travels along a nerve to the skin, causing a painful rash in a band (dermatome). The inflammation damages the nerve fibers and their connections in the spinal cord. Damaged nerves can fire spontaneously and amplify normal sensations, causing pain long after the skin heals.

Symptoms

• constant burning, aching or throbbing pain in the area of the old rash
• sharp, shooting, electric or stabbing pains
• allodynia: pain from light touch, such as clothing, bedsheets or a breeze
• itching (postherpetic itch), sometimes severe
• numbness or altered sensation
• scarring or color changes in the skin

The pain often disrupts sleep (insomnia), mood, appetite and activity, and can lead to depression and social withdrawal. It is one form of neuropathic pain.

Risk factors

• age: the most important; risk rises steeply after 60
• severe pain during the shingles episode
• a widespread or severe rash
• shingles affecting the face, especially the eye (herpes zoster ophthalmicus)
• pain before the rash appears (prodromal pain)
• weakened immune system
• diabetes

Diagnosis

PHN is diagnosed from the history of shingles and the persistence of pain in the same area for at least 3 months (some definitions use 90 days after rash onset). Tests are rarely needed. A doctor will examine the skin and sensation and assess sleep, mood and daily function.

Treatment

Treatment aims to reduce pain to a manageable level; complete relief is not always possible. Combinations often work best.

Topical treatments

• lidocaine 5% patches: applied over the painful area for up to 12 hours a day; few side effects; a good first choice, especially for older adults
• capsaicin 8% patch: applied in a clinic for 30 to 60 minutes; can relieve pain for up to 3 months
• lower-strength capsaicin creams: over the counter, but require repeated application and cause initial burning

Oral medicines

• gabapentin or pregabalin: reduce nerve signaling; can cause dizziness and drowsiness; doses are increased gradually
• tricyclic antidepressants (nortriptyline, amitriptyline) in low doses; caution in older adults and heart disease
• duloxetine: an SNRI used for neuropathic pain
• opioids and tramadol are generally avoided or used only short-term, because of risks and limited long-term benefit

Other options

• nerve blocks or epidural injections in selected cases
• TENS (transcutaneous electrical nerve stimulation)
• cognitive behavioral therapy and pain management programs
• treatment of sleep problems and depression

Practical tips

• wear soft, loose clothing; cotton is often best
• cover the area with a light dressing or plastic film to reduce contact
• cool packs (not ice directly on skin) may help some people

Prevention

• Shingles vaccine: the recombinant zoster vaccine (Shingrix), given as 2 doses, is recommended for adults 50 and older and for adults 19 and older with weakened immunity. It is more than 90 percent effective at preventing shingles in most age groups and sharply reduces PHN.
• Early antivirals: starting acyclovir, valacyclovir or famciclovir within 72 hours of the rash shortens shingles, although their effect on preventing PHN is modest.
• Early pain control during shingles may reduce the chance of chronic pain.

Outlook

PHN often improves gradually. Many people improve significantly within a year, though a minority have pain lasting years. Treatment can reduce pain and improve sleep and quality of life even when it does not eliminate pain.

Frequently asked questions

What is postherpetic neuralgia?

Postherpetic neuralgia is persistent nerve pain in the area where a shingles rash occurred, lasting 3 months or more after the rash heals. It happens because the shingles virus damages the nerve, which keeps sending pain signals.

How long does postherpetic neuralgia last?

It varies. Many people improve within several months to a year, but some have pain for years. Older people and those with severe shingles are more likely to have long-lasting pain.

What is the best treatment for postherpetic neuralgia?

Lidocaine patches are often tried first because they have few side effects. Gabapentin, pregabalin, low-dose tricyclic antidepressants, duloxetine and capsaicin patches are also effective. Combinations often give the best relief.

Can the shingles vaccine prevent postherpetic neuralgia?

Yes. The recombinant shingles vaccine greatly reduces the risk of shingles and therefore of postherpetic neuralgia. It is recommended for adults 50 and older and for adults 19 and older with weakened immune systems.