Since chronic pain is, by definition, pain that has persisted beyond the time of healing, a classification based purely on causal agent is not achievable. In some chronic pain syndromes, such as rheumatoid arthritis and osteoarthritis, healing is never completed. For these reasons, a chronic pain classification system needs to be pragmatic and heterogeneous in its classification strategy. The IASP task force has chosen classification by region with secondary classification by etiology. Entries follow a standardized format providing definition, site, main clinical features, associated symptoms and signs, laboratory findings, usual course, relief strategies, complications, social and physical disabilities, pathology, diagnostic criteria, and differential diagnosis.
Some decisions regarding specific syndromes are potentially controversial.
The task force omitted atypical facial pain because the senior editor thought it a vague and overused term. I believe devising clearer criteria might have been a better strategy, because this category is in frequent clinical use and does appear to identify a discrete group of patients. Myofascial syndromes subdivide into general and regional forms. This strategy seems reasonable, given the difference between fibromyalgia and more localized, trauma-related syndromes. The task force also omitted chronic pain syndrome as a vague, often perjorative term that dismisses the reality of the patient's pain.