Louisiana Pain Specialists - Pain Diagnosis and Intervention Experts

By Tarun Jolly, MD, Elizabeth Srejic

Postherpetic neuralgia (PHN) is a painful complication of shingles (herpes zoster). Shingles is a reactivation of dormant chickenpox virus (varicella zoster) residing in nervous tissue. Shingles appears as a painful rash of blisters confined to one dermatome (an area of skin supplied primarily by one spinal nerve). Normally, shingles clears up within a few weeks. However, persistent pain that lasts more than six weeks after the initial rash may indicate an individual has developed PHN.

Years after an individual has had the chickenpox infection, the dormant varicella virus may escape from nerve cell bodies and migrate down nerve axons where it causes viral infection of tissues around the nerve. The virus may spread to adjacent ganglia, infecting the local dermatome. The infection manifests as a painful rash that appears in a stripe or band around the torso, usually on one side of the body. In most cases, the rash clears within 2-4 weeks. However, in some people residual nerve pain may persist for years.

Reactivation of the chickenpox virus is possible in all infected persons, but becomes more common with increasing age and decline of varicella-specific cell-mediated immunity¹. Immunocompromised patients and people who are older than 50 years face an increased risk for a severe course of disease.

Symptoms of PHN may include:

• Pain – The pain of PHN is described as burning, sharp and jabbing, or deep and aching. Neuropathic pain develops due to lesions or disease affecting the central and peripheral nervous systems. Generally, neuropathic pain includes allodynia, or pain provoked by stimuli that are not usually painful, such as the touch of a feather on the skin, and hyperalgesia, a condition in which a normally painful stimulus may cause disproportionately severe irritation and pain.
• Sensitivity – Due to allodynia, people with PHN experience pain from normally harmless stimuli, such as light touch on the affected skin.
• Itching and numbness – Although uncommon, PHN can produce itchiness and numbness in the affected area.
  Weakness or paralysis – In very rare cases, PHN patients may develop muscle weakness or paralysis if the affected nerves control movement.

There is a vaccine (Zostavax) available to help prevent shingles and subsequent PHN. It is approved for persons aged 50 years and older. The live attenuated herpes zoster vaccine boosts an existing immune response, so that the already established varicella-zoster virus infection is kept latent². Vaccination has been shown to halve the risk of herpes zoster, and the risk of PHN by two thirds in people who are 60 years old. The vaccine so far is well tolerated in older, immunocompetent adults³. The efficacy of this attenuated high-dose live vaccine was evaluated in a double-blind randomised, placebo-controlled trial involving more than 38,000 immunocompetent adults aged 60 years or older⁴. Compared to placebo the vaccine reduced the frequency of herpes zoster by 51% and the incidence of PHN by 67%. Overall, the burden of illness was reduced by 61%. The course of diseases occurring among the vaccine recipients was clearly milder and the risk for complications was lower than among the placebo recipients. Although the vaccine efficacy against herpes zoster declined with advancing age of the vaccinees, subjects older than 70 years also benefited from vaccination because the burden of illness was considerably reduced.

It is important see a doctor at the first sign of shingles. The risk of developing subsequent PHN is halved if antiviral medications are taken within 72 hours of developing the shingles rash In addition, antiviral drug therapy can reduce the severity and duration of herpes zoster if begun within 72 hours of the appearance of the shingles rash.

Treatment for PHN depends on the type of pain experienced by the patient. Pain control options may include:

• Antivirals – Medications such as famciclovir, when taken at the onset of shingles outbreak, may shorten the clinical course of the illness and inhibit complications such as PHN. Once PHN has appeared, these medications are not effective.
• Analgesics – Pain-reducing agents such as non-steroidal anti-inflammatory drugs (NSAIDs), or ibuprofen-like drugs, are a good option for some PHN patients. Topical agents such as pain-relieving patches have also proved highly effective. These patches, which contain the numbing medication lidocaine, can be applied to painful areas of the skin to provide hours of relief. Numerous clinical studies demonstrate the efficacy of lidocaine patches in PHN. In one study, a population of patients including those with PHN who had been successfully treated with 5% lidocaine patches, were followed up by telephone interview after 3 and 5 years⁵. Questions were related to the efficacy, development of tolerance, tolerability, wear time and comfort of the patch. No patient discontinued because of inadequate analgesia or intolerable side effects, and there were no systemic side effects. Another study found treatment with 5% lidocaine patches was associated with improvements in pain, allodynia, quality of life and sleep measures⁶. In addition, lidocaine patches may be particularly effective in the treatment of PHN-related neuropathic allodynia⁷.
• Antidepressants – Low doses of tricyclic antidepressants such as nortriptyline and amitriptyline may help increase tolerance to severe pain in PHN patients. They are prescribed in lower doses than those used to treat depression. SSRIs and other types of antidepressants are less effective but may have fewer side effects in these individuals.
• Anticonvulsants – Anti-seizure medications such as gabapentin (Neurontin) and pregabalin (Lyrica) may stabilize abnormal activity in the nervous system caused by injured nerves. In addition to modulating pain, they help control muscle spasms. A randomized double-blind placebo-controlled 13-week trial designed to evaluate the long-term efficacy and safety of pregabalin for relief of PHN pain found the medication was effective in reducing pain and well-tolerated in 126 patients⁸. Further, a randomized, double-blind, placebo-controlled study conducted in 158 patients who had experienced pain for at least 3 months after shingles found gabapentin administered twice daily is effective and safe for the treatment of pain associated with PHN⁹.
• Capsaicin – Topical administration of creams containing extracts from the seeds of hot chili peppers may relieve pain in PHN patients. At first, the medication may cause a slight burning sensation on the skin, but this side effect wanes over time. One study showed a single 60-minute application of a capsaicin cream in PHN patients produced significant reduction in pain that was maintained over a 12-week period¹⁰; a similar study concluded the treatment appeared to be tolerable, generally safe, and effective¹¹.
• Botox – Injectable botulinum toxin A (BTX-A) is gaining popularity in the treatment of many pain syndromes, including PHN. A randomized, double-blind, placebo-controlled study in which 60 subjects with PHN were randomly and evenly distributed into BTX-A, lidocaine, and placebo groups found subcutaneous administration of BTX-A significantly decreased pain in PHN and reduced opioid use compared with lidocaine and placebo at day 7 and 3 months post-treatment¹². It also increased subjects’ sleep times.

Louisiana Pain Specialists understands the burden of living with pain and strives to help patients regain their quality of life. Our caring practitioners are dedicated to working closely with patients to create tailored individual pain management programs designed to restore good health and happiness. To investigate treatment options for your PHN, call to schedule an appointment with us today.

References

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