The definition of pain by the International Association for the Study of Pain (IASP), as revised in 2020, states that it is "an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage," suggesting that pain or similar unpleasant sensory experiences may arise even if the cause of such sensations cannot be clearly identified. Pain, on the other hand, has been classified chronologically as acute, subacute or chronic pain such as those directly caused by cancer and non-cancer diseases and by the mechanisms involved. These are divided into nociceptive, neuropathic, and nociplastic pain, the last one of which is a recent addition to the classification. WHO created an independent category dedicated to chronic pain in its latest version of the International Classification of Diseases (ICD-11) defining it as pain that continues or reiterates over a period of three months or longer. As prolonged pain causes both physical and mental damage resulting in degradation of quality of life, it has been stressed that such pain must be approached from both the physical and mental perspectives. For this reason, multi-faceted evaluation is useful in treating chronic pain. In Japan, there are a number of guidelines for the treatment of chronic pain that have been published by different scientific societies as well as by a study group of the MHLW's Chronic Pain Policy Project. These serve as guides for providing evidence-based treatments to affected patients. Chronic pain remains a major challenge since they not only lower the quality of life of affected patients but also cause considerable damage to Japanese society as a whole.

Excellent outcomes were achieved with spinal cord stimulation (SCS) for 7 to 10 days on 2 patients who developed postherpetic neuralgia. Both patients were within 2 to 3 months of the onset of the condition, and nerve blocks provided only temporary pain relief and drug therapies had poor efficacy. The authors believe that limited-duration SCS for subacute postherpetic neuralgia is a useful treatment approach that may prevent the pain from progressing to chronic postherpetic neuralgia.
Aged ; Electric Stimulation Therapy ; methods ; Female ; Herpes Zoster ; complications ; Humans ; Neuralgia, Postherpetic ; etiology ; physiopathology ; therapy ; Outcome Assessment (Health Care) ; Pain, Intractable ; therapy ; Spinal Cord ; physiology