[Pain therapy in herpes zoster and post-zoster neuralgia.]

Herpes zoster neuralgia and post-zoster neuralgia (PZN) are common disabling pain syndromes. While pain from acute herpes zoster is self-limited in most cases, as pain may disappear without treatment, post-zoster neuralgia is difficult to manage. Pathological findings in acute herpes zoster include infiltration of ganglia, demyelinization and loss of axons; yet the pathogenesis of pain remains largely unknown. In postzoster (often incorrectly called post-herpetic) neuralgia, peripheral and central origins are mentioned for the development of pain: selective loss of myelin-sheathed nerve fibres, sensitization of peripheral nociceptors, cross-talk between afferents and sympathetic efferents, deafferentation with somatotopic remodeling, virus-induced spontaneous activity, and nociceptive nervi nervorum. Pain shows no sex-specific differences, but there is a clear predominance in elderly patients over 60 years of age. In these patients aggressive therapy should be instituted. Numerous pharmacological, anesthetic and surgical approaches have been proposed for the treatment of pain in herpes zoster. Most approaches have been studied in uncontrolled settings. Treatment is most effective when installed early in the course of the disease. For acute zoster pain, treatment with acyclovir, glucocorticosteroids and sympathetic blocks reveal the best results. PZN of less than 3 months' duration should be treated with sympathetic blocks. Long-standing PZN resolves in two-thirds of the cases when treated with tricyclic antidepressants. TENS may be tried concomitantly. Topical ASA and capsaicin show promising effects and should be the object of further investigation. The same is true for specific zoster hyperimmunoglobulins and non-specific immunoglobulins; however, there are no definite results. In the future, controlled, double-blind studies on the effect of therapeutic measures in preventing postzosteric neuralgia need to be conducted. So far, the positive effect of sympathetic blocks in preventing the late pain complications of herpes zoster can only be suggested and recommended based on subjective experience.