Postherpetic neuralgia: what do we know and where are we heading?

Postherpetic neuralgia (PHN) remains a difficult pain problem for patients and physicians alike. This review describes the epidemiology and pathophysiology of PHN and discusses proposed mechanisms of pain generation and the various treatments currently available. Evidence is scant for the value of surgical and procedural interventions in general, although there are numerous small studies supporting the use of specific interventions such as nerve blocks, neurosurgical procedures and neuroaugmentation. Medical interventions, particularly the use of antidepressants and anticonvulsants remain the best-documented therapies for treating pain associated with PHN. There is good evidence that amitriptyline and gabapentin reduce pain with PHN. Topical local anesthetics, such a lidocaine, may also be helpful. The decision to use a particular agent or intervention may depend on whether there is spontaneous pain, burning or lancinating pain or numbness. Interventions with low risk, such as TENS are appropriate. Although prevention of postherpetic neuralgia appears to be an appropriate strategy, there is little evidence to support the position that medical or interventional approaches (nerve blocks) will prevent PHN after a patient develops acute herpes zoster (HZ). Although antivirals are appropriate for acute HZ, and the use of neural blockade and sympathetic blockade may be helpful in reducing pain in selected patients with HZ, there is little evidence that these interventions will reduce the likelihood of developing PHN.