POST-HERPETIC NEURALGIA

Facts:

1. Caused by herpes-zoster (shingles) infection.
   Herpes-zoster infections affect 1.25/1000 people.
   Elderly approximately 20X more likely to be affected.
   Patients with malignancies, especially lymphoproliferative disorders are at increased risk.
   
2. Prevalence rates of post-herpetic neuralgia range from 9 to 34%.
   a. 65% of patients above age 60 have pain for more than a month.
   b. 75% of patients above age 70 have pain for more than a month.
   c. 50% of patients above age 60 have pain for more than a year!

Symptoms:

1. Burning and/or lancinating pain in the distribution of a previous herpes-zoster rash.
   Healing or healed rash usually apparent.
   Patients may have abnormal sensation in this distribution.
   
2. Most common areas affected in the elderly are the thoracic area and the ophthalmic division of the trigeminal nerve.

Diagnosis:

1. History
   Physical exam
   
2. No special testing needed

Treatment:

1. Antidepressants - Tricyclics (Elavil) are the most studied group for PHN.
   Antiepileptics - Gabapentin (Neurontin) is good for the lancinating pains, has a good side effect profile for the elderly. Also unlike other anti-convulsants, it has no hepatotoxicity, does not cause blood dyscrasias and has few drug interactions. Lidoderm patches may be of some symptomatic value. (after lesions
   heal) Sympathetic nerve blocks - may be valuable even in long term patients.
   Radiofrequency rhizotomies in refractory cases.
   
2. Intrathecal steroids - a relatively new but promising treatment.