A microhistory of pain

Fast-forward to the Middle Ages, a time when it was hell to have a toothache, even though laudanum laced with opium was readily dispensed. One of the opiophiles of the era was the enlightened sixteenth-century practitioner Paracelsus. He was the original patient-centered physician. "Every physician must be rich in knowledge," he wrote in Man and His Body, "and not only of that which is written in books; his patients should be his book, they will never mislead him...and by them he will never be deceived. But he who is content with mere letters is like a dead man; and he is like a dead physician." We may be overdue for a Paracelsus revival.

The man most responsible for our modern misconception of "mental pain" versus "physical pain," however, was the seventeenth-century philosopher and scientist Rene Descartes. Although he is often blamed for the mind-body split that came to characterize Western thinking, in other ways, Descartes's investigation into pain was farsighted. In the treatise De l'homme, his hypothesis about pain pathways and the "delicate threads" that conduct pain signals, for instance, turned out to be a crude but correct notion of nerve fibers and neurotransmitters. But it was his theory of the transmission of pain signals that led to what is known as the "specificity theory" of pain-the notion of pain as one fixed pathway or center. This idea dominated the study of pain until the last thirty or forty years.

Descartes's theory was accompanied by a famous illustration of a rather hunchbacked naked man, eyes a-bulge, who appears to be stepping into a campfire. His foot is in the flame. "If for example fire comes near the foot," he wrote in 1640, "minute particles of this fire, which you know move at great velocity, have the power to set in motion the spot of skin on the foot which they touch, and by this means pulling on the delicate thread which is attached to the spot of the skin, they open up at the same instant the pore against which the delicate thread ends, just as by pulling on one end of a rope one makes to strike at the same instant a bell which hangs at the end."

Descartes has helpfully labeled the diagram. The sensation of pain (A) is perceived in the foot and then travels up to the "common sense center" (F) in the pineal gland, which interprets the signal as pain. This same stimulus-response model still defines our popular understanding of pain: The coffee table hits your toe, a sensation in the nerves then tugs at the bell-rope of the brain, which interprets this event as pain. No coffee table, no pain. But even in his time, Descartes had to defend this theory against critics. When it was pointed out to him that some amputees still feel pain in their missing limbs-phantom limb pain-he nimbly responded that the brain was just being tricked by false signals. But he still characterized the mind as a passive central switchboard instead of as a coauthor of pain.

In Descartes's mechanistic view, pain is something that happens to the body, a sensation then promoted to the status of a concept in the brain. A worker-CEO arrangement, you could say, except that the goods flow only one way. Although the brain is the boss, it is a passive decoder, and pain only runs along one track, with its own special apparatus, impervious to emotions or environmental factors.

The race for pain's Northwest Passage-the path it takes in the body-was under way, and for the next three hundred years science pursued this mysterious trail. Pain began to lose its multiple meanings, as a visionary experience in religion, or as an expressive element of tragedy. Instead, pain became the property of science and medicine, even though they didn't quite know what to make of it. The focus shifted from exploring the questions of identity, consciousness, and grace that pain raises to describing its mechanisms in the body and brain. The pharmaceutical age began at the end of the nineteenth century. Cutting pain out of the body, cutting nerves, and killing pain became the new goals.

A time line of some of the landmarks of pain science and treatment over the past two centuries might look like this:

1803 Morphine is synthesized from opium

1846 The discovery of anesthesia

1853 The invention of the hypodermic needle

1853 Acetylsalicylic acid, predecessor to aspirin is developed

1914 The Harrison Act in the United States sets restrictions on narcotic drugs

1943 Pain Mechanisms published by William Livingston

1946 Henry Beecher's work on the power of the placebo

1965 The gate-control theory of pain published by Melzack and Wall in the journal Science

1966 The first hospice, St. Christopher's, opens in the United Kingdom

1973 International Association for the Study of Pain holds its first congress

1975 The McGill Pain Questionnaire (first measurement of pain intensity)

1976 Discovery of endorphins

1986 The World Health Organization publishes The Analgesic Ladder: Guidelines to Cancer Pain Relief

2000 The U.S. Congress declares the next ten years the "Decade of Pain Control and Research"