Pain is one of medicine's greatest mysteries. When farmer John Mitson caught his hand in a baler, he cut off his trapped hand and carried it to a neighbor. "Sheer survival and logic" was how he described it. "And strangely, I didn't feel any pain." How can this be? We're taught that pain is a warning message to be heeded at all costs, yet it can switch off in the most agonizing circumstances or switch on for no apparent reason. Many scientists, philosophers, and laypeople imagine pain to operate like a rigid, simple signaling system, as if a particular injury generates a fixed amount of pain that simply gets transmitted to the brain; yet this mechanistic model is woefully lacking in the face of the surprising facts about what people and animals do and experience when their bodies are damaged.
Patrick Wall looks at these questions and sets his scientific account in a broad context, interweaving it with a wealth of fascinating and sometimes disturbing historical detail, such as famous characters who derived pleasure from pain, the unexpected reactions of injured people, the role of endorphins, and the power of placebo. He covers cures of pain, ranging from drugs and surgery, through relaxation techniques and exercise, to acupuncture, electrical nerve stimulation, and herbalism.
Pain involves our state of mind, our social mores and beliefs, and our personal experiences and expectations. Stepping beyond the famous neurologic gate-control theory for which he is known, Wall shows that pain is a matter of behavior and its manifestation differs among individuals, situations, and cultures. "The way we deal with pain is an expression of individuality."
About the Author
The late Patrick Wall was professor of physiology at St. Thomas's Hospital Medical School, London and a fellow of the Royal Society. His books include Defeating Pain, The Challenge of Pain, Natural Pain Relief, and Textbook of Pain.
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Private Pain and Public Display
It is crucial that we begin with precise and objective reports of what people and animals do when injured. The reports do not match the expectation of the victim or of the observer. In exploring the nature of pain, it will be necessary to separate reality from what we think ought to be observed. We will start with sudden events where a previously "normal" being is abruptly converted to a "sick" one. Of course, no such event occurs in a vacuum, as there is always a surrounding scene and the victim arrives at the accident with a personal and genetic history. Later, we will have to incorporate the vastly more common and less dramatic situation in which the onset of disease and pain is insidious.
A Swiss Army Officer
A forty-three-year-old reserve major, described by his wife as tough and taciturn, was skiing with his squad in the Upper Engadine region of Switzerland when a snow bridge collapsed below him. He remembers free falling into a crevasse with ice walls in front and behind, and scraping down one wall. With a tremendous crash and thump, he found himself wedged firmly in the ice crack. One arm was jammed above his head and he could not move his legs. He remembers hearing his gun and ski poles rattling down below, deeper into the crevasse. He was winded but was surprised to feel no pain whatsoever. He looked up and saw his men peering over the brink, and called out that he was all right but could not move.
A man was lowered down to him on a line and put a sling around him. The menabove hauled on the ropes, and he remembers his relief on feeling himself swaying free. They carried him down to an open area and radioed for a helicopter, which arrived after twenty-five minutes. His men were unusually quiet and subdued, in contrast to their normal boisterous behavior. He recalls feeling ashamed, as he had lectured on how to avoid such accidents. He wondered what this would do to his chances of promotion, and discussed this with the sergeant, who tried to cheer him up. During all this time, he recalls no trace of pain, either when he hit the ice slot or during his rescue.
He was strapped onto a stretcher and the helicopter took off. Just then, some forty-five minutes after his fall, a searing pain started in his left shoulder and spread to his neck and chest. He cried out. A crew member gave him a subcutaneous injection of fifteen milligrams of the narcotic morphine from the standard equipment in the emergency kit. By the time they arrived in hospital, he was dozy and the pain had lessened.
In the hospital, it was found that he had a dislocated left shoulder, a broken left collar bone, and serious bruises over his pelvis and upper legs. He was briefly anesthetized, and the shoulder bones were put in their proper place. He was put to bed and slept. Next morning, his shoulder ached all the time and he felt severe stabs of pain if he moved. He was sore all over, and was given painkillers. He felt exhausted and dozed for long periods. When the doctors came on their routine ward round, his pain escalated as they uncovered him and he cried out when they gently touched his shoulder. For the rest of the day, he curled up, moving as little as possible. He wanted no food. When visitors came, he put on his standard act: "Nothing to it," "Just a bit of a fall," and "I'll be out of here in a day or two." Within himself, he wished they would go away and leave him alone.
This history has two clear epochs. In the first emergency period of forty-five minutes, where survival, escape, and rescue had clear priority, there was injury but no pain. He was mentally clear and supervising his own rescue. Furthermore, he was assessing the situation clearly but blaming himself and fearing for the future. In the second period, when pain began, recovery from the injury had priority. Pain was present and increased with movement or touch. Beyond the presence of pain, his usual character had changed: normally a very active man, he was overwhelmed by lethargy and fatigue; usually a good eater, he had no appetite; habitually gregarious, he disliked company, although verbally he put on a very good act in imitating his old self. Within himself, he displayed the complete syndrome of the best tactics for recovery in people or animals: don't move, and don't let anyone else move you, just sleep. Outside himself, he displayed the opposite, for the benefit of other people and for his own image: "I'm all right," "Soon be out," "Don't worry," "It only hurts when I laugh."
The Anzio Beachhead
During the winter of 1943-44, Allied troops came to a halt in their advance up Italy on the Gustav line, which included the slaughter point of Monte Cassino. In an attempt to outflank this line, American and British troops landed 50 miles north on the beaches of Anzio in January 1944. They landed successfully on the coastal strip but were trapped when the Germans regrouped in the hills. It took until May 1944 before there was a breakout and Rome was captured. During this time, the Allied troops' lines hardly moved and they suffered heavy casualties, mainly from persistent artillery fire.
Harry K. Beecher was the medical officer admitting casualties to one of the few hospitals on the beachhead. He was later to become a leader in the new clinical research on pain as professor of anesthesia at Harvard. His concern for humanity reflected that of his ancestor, Harriet Beecher Stowe, author of Uncle Tom's Cabin. Every wounded man who could speak was asked the same question: "Are you in pain? Do you want something for it?" All of these men were seriously wounded, as they had already been sent back after first aid in advanced medical posts. Some of these men were in an exalted state, recognizing their near brush with death. Beecher collected the answers and was astonished that 70 percent of the men answered no to both questions. When the war was over, Beecher asked the same questions of an age-matched group of civilian men who had been operated on at the Massachusetts General Hospital in Boston; 70 percent answered yes to both questions.
Beecher reasonably concluded that something about the situation in which the tissue damage was inflicted influenced the amount of pain suffered. Beecher had a theory about what was the crucial difference in the two situations. To be wounded on the Anzio beachhead had a positive biological advantage over not being wounded. This paradoxical statement needs explanation. To be wounded and to reach the hospital at Anzio implied a good chance of evacuation and survival. To remain in the line unwounded implied a serious risk of being killed. Of the 767 men in the American Rangers battalion who attacked in the attempted breakout on January 30, only six returned. Beecher proposed that the men he questioned in Anzio were pain free because they were in an exalted state in the expectation of survival with honor. Therefore, he suggested that there are rare circumstances in which wounding is advantageous, and those wounds are pain free. I doubt this reasoning, but there is no doubt that he observed numbers of seriously wounded men who were not in pain.
The Yom Kippur War
In October 1973, Syria and Egypt attacked Israel and there was a brief, violent war. Dr. Carlen from Canada, Dr. Bill Noordenbos from Holland, and I decided to study a complete sample of Israeli soldiers who had suffered a traumatic amputation during that war. We examined seventy-three amputees from days to months after their injury. Their mean age was twenty-six and ranged from nineteen to forty-five years. This study of the subsequent history of amputees in or out of pain was possible because all Israeli amputees attended a single rehabilitation hospital at Tel Hashomer outside Tel Aviv. On questioning about their first sensation at the time of injury, the great majority clearly described their sensations with neutral words such as "bangs," "blows," and "thumps." Not one described a flash of pain that then died down. These men uniformly expressed their surprise at not feeling pain, often beginning with "Doctor, you won't believe it but ..." A minority had felt pain from the first moment.
With Beecher's reasoning in mind, we began to inquire about the precise circumstances of their wounding. The scene at Anzio was evidently one of unremitting horror and terror, continuing night and day, with the common soldier adjusting to some passive tactic that he hoped would end in survival. For those of us fortunate enough not to have been in battle, we perhaps imagine that painless injuries could occur only in the heat of combat when the "blood was up" and the victim was engaged in some intense action. But, far from this picture of continuous intensity, the Yom Kippur War was often intermittent, scattered with abrupt short violence. Some of the men had suffered in road accidents as they raced at night with lights out on unfamiliar roads. Some had been asleep in a quiet area when they were hit by an unexpected long-range shell. Others had been hit suddenly by the accidental firing of weapons from their own side. It was evident that painless injury could occur in men who were in no unusual state of mind. The episode appeared to begin precisely upon impact and did not depend on some prior expectation.
Our team, which included fluent Hebrew speakers, very tentatively and diplomatically explored the question whether any of these men greeted their injury as welcome. There was never a hint that anyone adopted the Darwinian approach that being wounded increased their chance of survival. No soldier reported even a fleeting sense of relief that he had escaped alive from the killing fields. Elsewhere, I spoke to a man from another army who had shot off one of his own toes in order to get out of action. He said it hurt badly and immediately. Yet the overwhelming reaction of these seventy-three soldiers to their wound was anger. Surprisingly, it was often directed at themselves: "If only I had not gone into that house" or "If only I had not climbed out of the trench."
I found the most bizarre story of this kind to come from a man who had lost three fingers from one hand. He had been standing head and shoulders out of a tank turret when he saw an Egyptian wire-guided antitank missile streaking towards him. He dodged down, leaving his hands on the rim of the turret so that he lost his fingers when the missile exploded. He said, "What a fool I was. If I had time to get my head out of the way, I certainly had time to move my hands." Next to themselves, they blamed officers and, only low on the list, the enemy, who had, after all, really been responsible.
We can leave the topic of emergency painless injury as a fact that we must accept and explain without reverting to ad hoc attempts to classify it as a very special case, as Beecher did, or by using meaningless terms such as shockthe victims had clear minds and were behaving rationally. We have all witnessed one such episode on television. President Ronald Reagan was shot with a 9-mm bullet that entered his chest as he walked from a Washington hotel. He was slammed roughly into his car by the Secret Service men. He and the others in the car did not know he was wounded. He began to feel unwell, and there was a discussion about the possible damage to him when he slumped against the car door. On the anniversary of the shooting, Reagan appeared on a CBS documentary and said, with his wondrous command of English: "I had never been shot before except in the movies. Then you always act as though it hurts. Now I know that does not always happen."
So much for the men's reports of their immediate sensations. What was their sensory state after some weeks when we saw them? Within twenty-four hours of their amputation, 65 percent experienced a "phantom limb," a name given by the American Civil War physician Wier-Mitchell to the clear sensation that the missing limb is still present. The remaining 35 percent all felt a phantom limb within a few weeks. Pain in the phantom was experienced by 67 percent, who described it using the words "jabs," "strong current," "pins and needles," "burning," "knifelike," "pressure," "cramps," "crushing," and "vicelike." In addition, many had pain in their stumps, with or without phantom pain as well. On careful examination of the stumps, it was found that every man had at least one area of intensely painful hypersensitivity. At the time these men were examined, in 1973 and 1974, 80 percent had stumps that appeared perfectly healed with no signs of infection. It is particularly sad to report that when this same group of men was examined fifteen years later, even though all signs of infection had gone and all stumps appeared perfectly healed, the pain reports were identical to those we had reported soon after the war.
Now we have three new problems to absorb and explain. What can be the explanation of the common report of no pain at the time of the injury but pain within a day? Second, some of the pains appeared to the victims to be located in a lost limb. And third, some of the pains persisted even when there seemed to be complete healing of the remaining damaged tissue.
Animals with Abrupt Injuries
The major horse race in Britain at the end of the season is the Epsom Derby. To everyone's surprise, it was won in 1980 by a horse called Henbit, who was far from being the favorite. Half a mile from the end of the race, Henbit was running in the middle of the pack when it stumbled into a hole. The jockey felt and heard a crack. The horse accelerated away from the pack and, with the spectacular perfect gait of a thoroughbred at full gallop, won the race. In the paddock, the jockey leapt off and went to feel the right foreleg. As he suspected, and as was later confirmed by X-ray, the cannon bone, a fine long bone, had been fractured when the horse stumbled. The next day's newspapers had a headline that read "Gallant Henbit's career may end." The horse said nothing but began to limp. With good veterinary care, the fractured cannon bone appeared to knit perfectly, but something changed in the horse. They never got it up to speed again and it retired to stud. Smart horse?
Henbit is not the only horse to have impressed people with its "courage." In 1632, Sweden's King Gustav Adolf II was killed at the battle of Lützen in Poland. His horse had a large open gunshot injury in its left shoulder. In spite of this, the horse carried his dead master off the battlefield and walked to the Baltic coast where it died. Awed by this display of "valor," the Swedes transported king and horse back to Stockholm. The horse, now stuffed, stands today in the stables below the royal palace.
Deer hunters report the effect of rifle shooting at one member of a herd of deer. At the sound of the shot, the entire herd takes off at full speed, aiming for cover. One of the herd has been hit but, with anything short of an immediately lethal injury, it is impossible to identify the wounded animal from the others by its speed, gait, or skill. Long after, the wounded animal may be seen again, curled up, separated from the herd and drowsy.
Dog owners have often seen their gentle domesticated friends suddenly display their hoodlum characters given the chance of a dogfight. Fur flies, canine teeth puncture skin, and chunks of flesh are ripped free. Does the wounded dog stop and surrender? You wish it would. When finally separated from the brawl and taken home, the wounded dog again changes its character. It lies curled up, quiet, sleepy, wants no food, and licks its wounds. Be very cautious in examining the wounds because the dog is likely to yelp and bite you.
The subject of hunting is now under intense scrutiny for many good reasons. A recent study of stags chased and killed by hounds showed that their blood chemistry was grossly abnormal when compared with animals abruptly and humanely slaughtered. The changes were characteristic of intense stress, fatigue, and excessive exercise. Similar but less marked changes are seen in marathon runners who have voluntarily put themselves through a grueling race. The ethical question of cruelty rests on whether anyone is justified in putting an animal through this involuntary stress and not on the unanswerable question of what the animal felt at the moment of death. The fact that a dying soldier on a battlefield may not feel pain in his last moments does not remove the stress from which he suffers, nor does it solve the ethical question of whether his shooting was permissible.
I stress here the similarities between stressed and wounded humans and animals. That does not mean identity between species. There are profound differences. For example, when an old deer is culled by shooting and drops dead, the other members of the herd briefly startle but then continue grazing and ignore the corpse. Deer are evidently not human, but that does not give open permission to kill deer.
Animals and humans in the early stages after abrupt injury may appear to ignore the injury. They proceed with an activity that has a higher priority than care for the wound. Unfortunately, this common observation has been interpreted by some hunters and others in charge of animals to mean that animals do not feel pain. Examination of the victim a few hours later quickly dispels that generalization because, by then, they show all the same signs as humans who are trying to recover from injury.
Furthermore, there are long-term consequences wherever they have been examined. Animals learn and become cautious and skilled in avoidance. Henbit would never gallop at full speed despite the apparently perfect healing of its fracture. When the wily, fat old pike, who drives generations of anglers to distraction because he will not take the bait, finally gives up to senility, it is found that his mouth has the scar of an old hook from which he escaped and learned.
Hospital Emergency Rooms
My friend Ron Melzack, a Canadian psychologist, and I decided to examine and compare patients who were admitted to the emergency room (the casualty department) of the largest general hospital in Montreal. In a gentler setting, we could probe with questions that had not been possible in more urgent and dramatic scenes. We examined the first 138 patients to enter, who were alert, rational, and coherent, 37 percent of whom said they did not feel pain at the time of the injury. Of those patients with injuries limited to their skin, such as abrasions, cuts, and burns, 53 percent had a pain-free period. However, of those patients with deep tissue injuries, such as fractures, sprains, and stabs, only 28 percent had a pain-free period. The majority of these people reported the onset of pain within an hour, although some did not feel pain for many hours. The predominant emotions of the patients were embarrassment at appearing careless or worry about loss of wages. None expressed any pleasure or indicated any prospect of gain as a result of the injury.
A fifty-two-year-old senior machine shop foreman lay on a gurney in the emergency room after a collapse of heavy machinery had amputed the front of his right foot. He stated that there was no pain. This was not his first experience of painless sudden injury because an unexploded aircraft canon shell had lodged in the upper part of his leg during the Second World War, and we observed the old scar. He was coherent, sad, and thoughtful, and said, "What a fool they will think I am to let this happen" and "There goes my holiday." He lay still on the trolley with an intravenous drip running while waiting to go to the operating room. After a while he complained of a painful cramp in his left leg although the injured leg remained pain free. The pain went away with massage. Evidently, his analgesia was present only in the region of the original injury. This phenomenon had already been reported by Beecher, who observed that pain-free casualties complained of pain when intravenous needles were inserted.
We can now summarize key points of sudden injury. For a start, sudden injury may or may not be painful. The victims can be coherent and rational throughout. There may be no pain from the moment of injury. The pain-free state is localized precisely to the site of the injury. And all victims are eventually in pain.
Let us now turn to the majority (63 percent) who were in pain from the moment of injury. How much pain? They were asked to rate their pain on a scale of 0 to 10, with 10 as the worst pain imaginable. The answers were widely scattered. Anyone, expert or not, observing someone who is injured almost inevitably assigns an "appropriate" amount of pain that they expect. On what do they base this assignment of the appropriate: personal experience, professional experience, empathy, sympathy, knowledge of the victim? The staff of the emergency room thought that 40 percent were making "a terrible fuss," nearly 40 percent were "denying" pain, and 20 percent gave the "appropriate" answer. It is obvious there is something fundamentally wrong here. People generally are convinced that a certain degree of injury inevitably produces and justifies an appropriate amount of pain. Clearly this is not the case, but we have great difficulty in accepting the fact. (It is strange that even professionals may ignore their experience and persist in expecting patients to display only an appropriate amount of pain.)
A major theme of this book will be the exploration of the factors that, in addition to overt damage, produce pain and modulate its intensity. One crucial aspect is that patients are not only assessing their private misery but also making a public display. Their private misery is not necessarily about the pain. For example a twenty-two-year-old Israeli Army woman lieutenant with one leg blown off above the knee by a shell explosion was in deep distress with tears flooding over her face. When asked about her pain, she replied, "The pain is nothing, but who is going to marry me now?"
What did the patients say about their pain? Melzack has made an extensive study of the words people use, as will be discussed in chapter 2. He divides the words into "sensory," such as sharp, burning, and stinging, which describe the sensation itself, and into "affective," such as tiring, sickening, and annoying, which describe what the feeling is doing to the person. It is interesting that on their first encounter in the emergency room with doctors and nurses, patients used, almost entirely, the sensory words. Much later they would add the affective words. In this emergency situation, the first priority of communication was to inform those who brought aid exactly those details they would need to diagnose the injury. They delayed, to less urgent times, the information about what the injury was doing to their mood.
Governments have refined techniques over the centuries for deliberately inflicting pain. The victim is in a unique situation quite unlike that of any injury or disease because he is helpless and there will be no help. If the torture is part of an interrogation, the only way to end the pain is to tell the interrogator what he wants to hear or, more likely, to invent false yet plausible information. A few victims may have the skill to dissociate themselves from the present and to enter a fantasized world. The vast majority react in the predicted way and search only for ways to end the torture. Where the torturer is a sadist or has the intention to terrorize the population at large, the victim loses even the option that confession will stop the torture.
Christopher Buney wrote of his own interrogation in a German prison:
Suddenly the major turned and strode across the room and struck me in the face with a swing of his open hand. I knew now what was to come. The first impact still took me by surprise. There is a sense of shame following an unanswerable blow which has nothing of fear in it but which is more demoralizing than any pain.
To experience helplessness in the face of impending death wipes out confidence. The horror of this state becomes primary beyond the misery of the pain. A South African doctor conscripted into the army describes being presented with Namibian prisoners under torture and being ordered to treat them so that interrogation could continue. He gave morphine to ease their pain. I believe this compounds the atrocity. I do not believe that it was ethically permissible for the doctor to relieve pain where the consequence was that violent beating would continue to the point of threatening the prisoner's life.
Individuality can be demolished without pain. In the early 1970s, the British Army in Northern Ireland introduced a new high-tech method of interrogation without pain. Arrested men were made to lean at 45 degrees, supported by their handcuffed hands on a wall. A bag was placed over their heads so they could see nothing. Intense noise from loudspeakers prevented hearing. If they collapsed, they were propped up again. At irregular intervals, they were taken out and interrogated but were otherwise left in their unmoving posture of sensory isolation for days. When these men were examined, long after their release, many remained broken zombies, apathetic, tremulous, and unable to function. Primo Levi wrote of his experience in Auschwitz: "Anyone who has been tortured, remains tortured." The British government set up a judicial committee, the Gardner Commission, to investigate torture, and the practice was forbidden. For many of us, the fear of our manner of dying is much greater than our fear of death itself.
It would be narrow-minded to avoid admitting that there is a small fraction of any community that invites the very pain that the great majority attempt to avoid or cure. One such group are the athletes and aerobic buffs whose motto is "No pain, no gain." We can understand if not applaud their conviction that pain is a measure of achievement and is therefore welcome. A quite different group are those in the quasi-legal underground sadomasochist subculture who seek pleasure in pain.
An interview with an attractive woman in her forties who edits a magazine for sadists and masochists was revealing about the facts. First, she had no doubt that the pain she enjoyed had nothing to do with the pains of illness and injury, which she loathed. Next, the whipping that she invited had to stop short of serious injury, so the sadist who inflicted them had to be under her control and trusted. The pain was associated with a hugely increased sexual awareness. She felt her reactions to be like those of a horse "alerted and bounding after the thwack of a crop on its buttocks." She knew nothing in her background to explain her actions in any symbolic or associated terms.
I report this here without any of the sympathetic feeling that usually allows one to understand what is heard. Clearly this practice has many variations and extremes. Some can achieve sexual satisfaction only with pain. Some have defined requirements. The greatest pleasure over many years for a successful white banker was to be beaten up by a particular black woman. For some, the pain is self-inflicted during masturbation. Alfred C. Kinsey, author of The Sexual Behavior of the Human Male (1948), while masturbating would "insert an object into his urethra, tie a rope around his scrotum and tug hard on the rope as he maneuvered the object deeper." Some evidently search for increasing extremes and may kill themselves with asphyxia or wounding.
The word pain includes a reference to punishment, as in "on pain of death." Some achieve the tranquillity of absolution by punishing themselves for their sins or the sins of the world. The flagellants in Spanish religious processions appear exalted. A thousand years of Christian art portray candidate saints seeking wounds with radiant eagerness. The masochists are a small minority, but the rest of the community is fascinated by the paradox of their existence.
In this chapter we have seen that the public display of pain and the expression of private suffering are full of surprises. The amount of pain and the amount of injury are not tightly coupled. The time course of pain depends on the needs for escape followed by the needs best suited for treatment and recovery. The location of the pain may differ from the location of the damage. The public display of pain has the purpose of informing others of the patient's needs whereas the private suffering assesses the meaning and consequences of the patient's own miserable state. All pain includes an affective quality that depends on the circumstances of the injury and on the character of the victim.
Table of Contents
1. Private Pain and Public Display
2. The Philosophy of Pain
3. The Body Detects the Brain Reacts
4. The Whole Body
5. A "Normal'' Pain Response
6. Pains with Obvious Causes
7. Pain Without a Cause
8. How Treatments Work
9. The Placebo Response
10. Your Pain
11. Other People's Pain