IASP Taxonomy Background

Changes in the 2011 List

The work of the Task Force on Taxonomy in the era of 1979 to 1994 has been continued by the Committee on Taxonomy that has worked to update both pain terms and the classification of pain syndromes. All of the terms have been carefully reviewed and their utility assessed in reference to new knowledge about both clinical and basic science aspects of pain. The Committee conducted its business primarily by e-mail, but face-to-face meetings were held at each of the annual Congresses of IASP. We now present the 2011 version of IASP Pain Terminology. Members of the Taxonomy Committee in this era included: David Boyd, Michael Butler, Daniel Carr, Milton Cohen, Marshall Devor, Robert Dworkin, Joel Greenspan, Troels Jensen, Steven King, Martin Koltzenburg, John Loeser, Harold Merskey, Akiko Okifuji, Judy Paice, Jordi Serra, Rolf-Detlef Treede, and Alain Woda. The Chair would like to acknowledge the continuous contributions that Harold Merskey has made to taxonomy since the founding of IASP. As stated in prior publications of the IASP taxonomy, we do not see this listing of terms as immutable. As we learn more about pain, we will need to update terminology.

John D. Loeser, M.D.
Chair, IASP Taxonomy Working Group

Changes in the 1994 List

There was substantial correspondence from 1986 to 1993 among members of the Task Force and other colleagues. The previous definitions all remain unchanged, except for very slight alterations in the wording of the definitions of Central Pain and Hyperpathia. Two new terms have been introduced here: Neuropathic Pain and Peripheral Neuropathic Pain.

The terms Sympathetically Maintained Pain and Sympathetically Independent Pain have also been employed; however, these terms are used in connection with syndromes 1–4 and 1–5, now called Complex Regional Pain Syndromes, Types I and II. These were formerly labeled Reflex Sympathetic Dystrophy and Causalgia, and the discussion of Sympathetically Maintained Pain and Sympathetically Independent Pain is found with those categories.

Changes have been made in the notes on Allodynia to clarify the fact that it may refer to a light stimulus on damaged skin, as well as on normal skin. Also, in the tabulation of the implications of some of the definitions, the words lowered threshold have been removed from the features of Allodynia because it does not occur regularly. Small changes have been made to better describe Hyperpathia in the definition and note. A sentence has been added to the note on Hyperalgesia to refer to current views on its physiology, although as with other definitions, that for Hyperalgesia remains tied to clinical criteria. Last, the note on neuropathy has been expanded.

Introduction to the 1986 List

A list of pain terms was first published in 1979 (Pain 1979;6:249–52). Many of the terms were already established in the literature. One, allodynia, quickly came into use in the columns of Pain and other journals. The terms have been translated into Portuguese (Rev Bras Anest 1980;30(5):349–51), into French (H. Dehen, Lexique de la douleur, La Presse Medicale 1983;12(23):1459–60), and into Turkish (as Agri Terimleri, translated by T. Aldemir, J Turkish Soc Algology 1989;1:45–6). A supplementary note was added to these pain terms in Pain (1982;14:205–6).

The original list was adopted by the first Subcommittee on Taxonomy of IASP. Subsequent revisions and additions were prepared by a subgroup of the Committee, particularly Drs. U. Lindblom, P.W. Nathan, W. Noordenbos, and H. Merskey. In 1984, in particular response to some observations by Dr. M. Devor, a further review was undertaken both by correspondence and during the 4th World Congress on Pain of IASP. Those taking part in that review included Dr. Devor, the other colleagues just mentioned, and Dr. J.M. Mumford, Sir Sydney Sunderland, and Dr. P.W. Wall. Following that review, it was agreed to take advantage of the publication of the draft collection of syndromes and their system for classification, to issue an updated list of terms with definitions and notes on usage.

The versions now presented are based upon some subsequent discussions by correspondence. The form of the definitions and notes at this point has been the responsibility of the editor (H.M.). It would be difficult now to single out individual contributions, but the editor remains heavily indebted to those five members of the original Subcommittee on Taxonomy who sustained this work in the form of an Ad Hoc group and whose names are listed at the beginning of this report. Their knowledge and patience was repeatedly provided freely and with good will.

The revised current list follows. The original comments provided as an introduction to the terms are given in the following two paragraphs, which indicate both the process by which the terms were first delivered and the justification for them.

"The usage of individual terms in medicine often varies widely. That need not be a cause of distress provided that each author makes clear precisely how he employs a word. Nevertheless, it is convenient and helpful to others if words can be used which have agreed technical meanings. Following correspondence and meetings during the period 1976–1978, the present committee agreed on the definitions which follow, and the notes have been prepared by the chairman in the light of members' comments. The definitions are intended to be specific and explanatory and to serve as an operational framework, not as a constraint on future development. They represent agreement between diverse specialties including anesthesiology, dentistry, neurology, neurosurgery, neurophysiology, psychiatry, and psychology. A starting point for some of these definitions was provided by the reports of a workshop on Orofacial Pain held at the U.S. National Institute of Dental Research in November 1974.

"The terms and definitions are not meant to provide a comprehensive glossary but rather a minimum standard vocabulary for members of different disciplines who work in the field of pain. We hope that they will prove acceptable to all those in the health professions who deal with pain. Not only are they a limited selection from available terms, but it is emphasized that except for pain itself, they are defined primarily in relation to the skin and the special senses are excluded. They may be used when appropriate for responses to somatic stimulation elsewhere or to the viscera. Except for Pain, the arrangement is in alphabetical order."

It is important to emphasize something that was implicit in the previous definitions but was not specifically stated: that the terms have been developed for use in clinical practice rather than for experimental work, physiology, or anatomical purposes.