[Herpes zoster and post-herpetic neuralgia]

Pain associated with herpes zoster arise from the virul neuritis of the suffered trigeminal or spinal dorsal ganglion. Prolonged neuritis makes an irreversible nerve injury and continuous pain impulse develops a central sensitization. A post-herpetic neuralgia is thought to be a neuropathic pain due to the irreversible nerve injury and sensitization. It is important to treat herpetic pain completely before the development of the post-herpetic neuralgia, because there are few effective therapies to cure post-herpetic neuralgia. A sympathetic nerve block increases the nerve blood flow supply, and may improve the nerve injury. It is also known that some sympathetic mechanisms relate to the development of the sensitization. A sensory nerve block reduces pain impulse to the dorsal horn, and may interfere the sensitization. A cortico-steroid administrated with a nerve block can reduce the neuritis, and may improve the nerve injury.