How Do I Know If I Have Postherpetic Neuralgia?

Postherpetic neuralgia is a complication of a painful rash called shingles, which is caused by the varicella-zoster virus (the same virus that causes chickenpox). 

In up to 15% of people who have shingles, the pain associated with the condition does not go away when the rash disappears. This chronic pain is postherpetic neuralgia.

Postherpetic neuralgia is caused by nerve damage due to shingles. Shingles is caused by the varicella-zoster virus. After a person has chickenpox, the varicella-zoster virus remains dormant in the body but can become reactivated later in life, causing shingles. When the pain of shingles persists, it is postherpetic neuralgia.

Risk factors for developing postherpetic neuralgia include: 

• Older age (over 50)
• Greater acute pain
• More severe rash 
• Immunosuppression
• Cancer
• Human immunodeficiency virus (HIV)
• Chemotherapy

Most of the time, postherpetic neuralgia is easy to diagnose because it results from pain that persists after a documented case of shingles. The diagnosis is made based on the clinical presentation alone.  

Factors that can support a diagnosis of postherpetic neuralgia include: 

• Advanced age (postherpetic neuralgia is common in people aged 50 years and older)
• Severe prodromal pain with acute herpes zoster 
• Severe rash that preceded the pain
• Distribution of pain in certain areas of skin supplied by specific nerves (trigeminal or brachial plexus dermatomes)
• The presence of pain on light touch

Up to 50% of patients with postherpetic neuralgia do not respond to treatment.

Treatments for postherpetic neuralgia pain include: 

• Tricyclic antidepressants 
  • Amitriptyline (preferred) 
  • Nortriptyline
  • Desipramine
  • Maprotiline
• Anticonvulsants 
  • Gabapentin and pregabalin are first-line treatment choices
  • Carbamazepine, oxcarbazepine, lamotrigine, and valproic acid may also be used
• Topical lidocaine patches 
• Narcotic pain medications
  • Not a first-line treatment, and should be used cautiously
• Aspirin in cream 
  • Low benefit, but may help some patients
• Capsaicin cream 
  • Low benefit, but may help some patients
• Intrathecal glucocorticoid injections
• Botulinum toxin 
• Other treatments
  • Cryotherapy to freeze peripheral nerves (results are mixed)
  • Spinal cord stimulation and peripheral nerve stimulation (considered experimental)

The main way to help prevent shingles, which can lead to postherpetic neuralgia, is vaccination. There are two vaccines available for adults 50 years and older to reduce the chance of developing shingles.

• Zostavax (zoster vaccine live) is available in a single dose. Zostavax reduces the risk of developing shingles by 51% and postherpetic neuralgia by 67%. Protection from the Zostavax vaccine lasts about 5 years.
• Shingrix (recombinant zoster vaccine) requires two doses administered two to six months apart. The two-dose Shingrix vaccine is preferred because it is more than 90% effective at preventing shingles and postherpetic neuralgia. Protection from the Shingrix shingles vaccine stays above 85% for at least four years after vaccination. 

Antiviral agents or use of amitriptyline taken within 72 hours of the onset of shingles can reduce the intensity and duration of acute illness, and may also help prevent postherpetic neuralgia.