The McGill Pain Index



McGill Pain Index

Reflex Sympathetic Dystrophy (causalgia) has a score of 42 out of 50 on the McGill Pain

Index.  RSD in the most painful chronic disease that is known.

The McGill Pain Questionnaire was developed in 1971 by Ronald Melzack and Warren Torgerson from McGill University in Canada. Their paper On the Language of Pain [Anesthesiology, 1971, v 34] proposed what was then a novel idea:  It is not only the intensity of pain that matters. Each disease produces a different quality of pain: we have the burning of causalgia; the stabbing or cramping of visceral pain; and so on. The quality of pain provides a key to diagnosis and may even suggest a course of therapy. 

Over several years, patients in a variety of settings were asked to fill out the McGill Pain Questionnaire.  Pain scores were obtained from:

  1. Women during labour   Melzack et al 1981 CMAJ 125(4)

  2. Patients in a general hospital pain clinic   Melzack 1975 Pain 1(3)

  3. Patients in a hospital emergency department   Melzack and Wall 1982 Pain 14(1)

  4. A group of patients with a confirmed diagnosis of causalgia   Tahmoush 1981 Pain 10(2)

Results of the study: For any specific disease, the descriptive words chosen by patients were remarkably similar. So were the pain scores. Substantial portions of the words had the same relative positions on a common intensity scale for people from widely divergent social and ethnic backgrounds.

Melzack and Torgerson used this data to create the McGill Pain Index. It is a yardstick to quantify pain. The Index compares three categories of pain: Labour pain, clinical pain syndromes, and pain after trauma or accident.  It takes the visual form of a bargraph (illustrated below).

The McGill Pain Scale remains a useful instrument for doctors because it is reliable and consistent. The original paper from 1971 is considered a classic. Anesthesiology reprinted this in 2005 under the title Classic Papers Revisited The McGill Pain Questionnaire: From Description to Measurement.