Postherpetic neuralgia in immunocompetent elderly people.

The most menacing complication of herpes zoster in immunocompetent elderly people is chronic pain or postherpetic neuralgia (PHN). The cardinal epidemiological feature of PHN is its striking relationship to aging. Among zoster patients over 60 years old, estimates of the occurrence of PHN, defined as pain 1 month after rash onset, vary from 27 to 68%. The pathogenesis of PHN is incompletely understood but seems to involve varicella-zoster virus (VZV)-induced damage of peripheral afferent neurons and resultant changes in central afferent neurons and efferent pain-modulating neurons. PHN improves over time in many elderly patients, but an unfortunate subset experience of debilitating pain lasts for years. They experience constant and/or intermittent spontaneous pain and stimulus-evoked pain such as allodynia or hyperpathia. The outcomes of this pain include fatigue, sleep disturbance, anorexia, depression, social withdrawal, impaired activities of daily living and profound lowering of quality of life. The management of PHN is hampered by two problems: (1) a uniformly effective treatment for PHN is not available (although tricyclic antidepressants, local or regional anaesthetics, capsaicin, opiates, anticonvulsants and physical therapies are sometimes useful); and (2) early antiviral therapy of zoster may be ineffective in preventing PHN, partly related to the fact that days of VZV replication and neuronal destruction have occurred by the time the patient reaches the doctor. A potential solution to the problem of PHN is the vaccination of elderly persons with the varicella vaccine to prevent or attenuate zoster or PHN.