Publications
APS Bulletin • Volume 7, Number 1, January/February 1997
Resource Review
John D. Loeser, MD, Department Editor
Classification of Chronic Pain: Descriptions of Chronic Pain Syndromes and Definitions of Pain Terms
Reviewed by Mark D. Sullivan, MD PhD
IASP Task Force on Taxonomy, Harold Merskey & Nikolai Bogduk (Eds.), IASP Press, Seattle, 1994, $20, 222 pages, ISBN 0-931-092-05-1
IASP Press has produced a second edition of its classification of chronic pain syndromes. The first edition was published as a supplement to Pain in 1986. The purpose of the classification is to provide "universally accepted definitions of terms and a classification of pain syndromes," as first requested by Dr. John Bonica in 1979. The classification specifically tries to go "beyond what is available in the general international systems of classification such as the International Classification of Diseases" (ICD-10). By providing a description of chronic pain syndromes, the IASP Committee on Taxonomy hopes to establish a "standardization of observations," which through research, can lead to continuous updating and improvement.
The ICD-10 classifies disease by causal agent, systems of the body affected, pattern and type of symptom, and whether or not the disease is related to a medical procedure. 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. I agree wholeheartedly with this decision. The point of the classification, after all, is to show that not all chronic pain is the same and healthcare providers should not regard it as a single entity. The current Diagnostic and Statistical Manual of Mental Disorders (DSM-IV, 1994) of the American Psychiatric Association contains the diagnosis "pain disorder," which is the rough equivalent of "chronic pain syndrome." It is purely a diagnosis of exclusion, without clear implications for therapy, and it serves to further stigmatize patients with chronic pain. The IASP Task Force on Taxonomy deserves applause for moving away from these global labels.
The second edition expands the headache and spinal pain sections and adds a number of new, specific conditions associated with pain, such as Guillain-Barré syndrome and proctalgia fugax. I commend the authors for their efforts to revise the back pain sections of the taxonomy, which are quite confusing even in the ICD-10. This edition provides useful distinctions between referred pain and radicular pain and recommends dropping the term sciatica. Some of the syndromes provided are more likely to be associated with acute than chronic pain, but in general the back pain section adequately represents the state of the art in this difficult area.
This book is a useful, maybe even essential, reference for clinicians treating patients with chronic pain and researchers studying chronic pain. It provides the best categories we have for communicating about these vexing problems to our colleagues and the public.
Mark Sullivan is associate professor of psychiatry and behavioral sciences at the University of Washington in Seattle.