Post herpetic neuralgia is an extremely painful complication of herpes zoster or shingles. The excruciating pain and burning sensations are due to nerve damage caused by the severe inflammation caused by the varicella zoster virus which causes chicken pox and herpes zoster. As the name indicates, the pain starts after an attack of herpes zoster, when the lesions start crusting over and begin to heal. The neuralgia is typically distributed over the area of the skin innervated by the affected branch of the nerve, called a dermatome.
How Common is Post Herpetic Neuralgia?
According to the CDC, in the US alone each year around 1 million individuals develop shingles. Out of these, about one fifth or 200,000 develop post herpetic neuralgia. Studies show that the chances of shingles patients developing post herpetic neuralgia (PHN) is less than 10% in the age group below 60 years while about 40% of patients above 60 years age are at risk of developing post herpetic neuralgia.
By the Way, Is It Post Herpetic Neuralgia or Postherpetic Neuralgia?
This is something that has never been discussed before! It should be post herpetic neuralgia, as it is post (after) herpes nerve pain, and not 'postherpetic' as is usually used.
What are the Symptoms of Post Herpetic Neuralgia?
The pain of post herpetic neuralgia varies from a burning discomfort to extremely severe pain. Patients have described the pain as stabbing, throbbing, gnawing, jabbing, lancinating, deep aching, and, at times, the worst pain ever. The affected skin may be very sensitive to touch and temperature changes. This abnormal reactivity to light touch or other sensory stimuli is termed allodynia.
Depending upon the level of nerve damage, patients feel itchy or numbness in the area. When the ophthalmic branch of the trigeminal nerve on the forehead is affected (see the image), the resulting headache can be excruciating, compelling patients to even contemplate suicide!
Why is Post Herpetic Neuralgia Extremely Painful?
Post herpetic neuralgia occurs when nerve fibers are damaged during herpes zoster. Damaged, ragged nerve endings which are raw due to the inflammation caused by herpes zoster get trapped within the fibrous tissue when the skin starts healing with scars. Whenever the skin moves over these ragged nerve endings, extreme shooting pain results.
The damaged sensory nerves and neurons send pain signals to the brain in an exaggerated manner in PHN. It has also been found that normal inhibitory signals from the brain is also suppressed in PHN, resulting in further attenuation of the pain signals from the skin.
How Do I Prevent Postherpetic Neuralgia?
Primary Prevention: FDA in 1995 approved the varicella vaccine which reduce the incidence and severity of chickenpox in the vaccinated individuals. In such patients the occurrence of herpes zoster and post herpetic neuralgia is rare. The new shingles vaccine approved by CDC in 2006 reduces the development of post herpetic neuralgia by two-thirds .
Secondary Prevention of post herpetic neuralgia starts after an attack of shingles. Some clinical studies, though not conclusively, have reported that the earliest institution of treatment (as soon as the shingles rashes appear) with antivirals, antidepressants and/or oral prednisolone (controversial) can reduce the incidence of post herpetic neuralgia.
How to Manage Post Herpetic Neuralgia?
The treatment of post herpetic neuralgia usually involves dermatologists and neurologists. The management of post herpetic neuralgia involves the pain control while waiting for the condition to resolve.
Topical Treatment: Application of Capsaicin ointment, and higher strength local anaethetics are of limited value, but can help in milder cases. A lidocaine patch has been found useful in reducing the severity of the pain, but should not be used on the face.
Recently the FDA has approved a Capsaicin patch to be applied by a dermatologist in the treatment of post herpetic neuralgia. This provides pain relief upto a period of 3 months.
The common systemic medications prescribed for post herpetic neuralgia are OTC pain killers, tricyclic antidepressants and anticonvulsants. Some patients may require narcotics like morphine or intra thecal injection of methylprednisolone to relieve their misery. The problem with PHN medications is that most drugs cannot stop the pain-they can only make it tolerable.
Non medical interventions like transcutaneous electrical nerve stimulation (TENS) has also been tried successfully in some cases. Cognitive behavioral therapy, including biofeedback, relaxation training and hypnosis has also been used as adjuncts in the treatment of post herpetic neuralgia.
Updated on Nov 28, 2010
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Disclaimer
The information given in this article is for educational purpose only so that patients are aware of the options available. No diagnosis should be made or treatment undertaken without first consulting your doctor. If you do so, the author or suite101 will not be responsible for any consequences. The images provided are for illustration purpose only.
References
- PHN Pamphlet by Varicella Zoster Foundation
- Robert W Johnson,Robert H Dworkin. Treatment of Herpes Zoster And Post Herpetic Neuralgia. BMJ 2003;326:748-750
Hanish Babu - Dr.Hanish Babu, MD is a dermatologist and a feature writer on Suite101.com with more than 200 articles related to skin diseases on the ...
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