Thursday, December 12, 2013

Pain: The Science of Suffering

Book Review: Pain: The Science of Suffering by Patrick Wall ( Columbia University Press – Maps of the Mind – 2000)

I found this book to be fascinating, informative, and potentially practical, since pain and our anxieties about it, affect us all. The author is a medical doctor and a neuroscientist and one of the world’s foremost experts on pain. This book was written for laypeople and is not overly technical. He comes across as knowledgeable, sincere, and compassionate. He admits that there is yet much we don’t know about pain. There are many case histories given. The data show that pain is not simply physical. There is a rather inseparable mental component to all pain as well.

The author recounts anecdotes and interviews with trauma victims, including his own work with combat amputees. He recounts stories where people felt no pain until long after their injuries, some as serious as loss of a limb. Even Ronald Reagan noted no pain when he got shot, to his own astonishment. Among amputees, apparently, nearly all, felt, or feel a “phantom limb” that is not really there and most feel pain in that phantom limb, often for a lifetime. Such things are perplexing. Even animals will go on after trauma as anyone who has seen a deer get hit by a car and get up and run away will know. The author also examined emergency room patients along with a psychologist colleague. Significant percentages of victims (though quite less than half) did not feel pain or had limited pain even with deep tissue injuries, stabs, fractures, and sprains. Most felt pain within an hour but some pain was delayed for several hours. I remember once as a kid as I was in an emergency room for a tetanus shot after running a long rusty nail into my foot when a guy from a motorcycle crash came in with severe burns which shriveled his legs. He was coherent and speaking but obviously in a lot of pain as his moans revealed. The bottom line of this chapter, says Wall, is that: 

“… tissue damage and pain are not so intimately linked that the two can be considered equivalent.”

Wall summarizes sudden injury in the following way:

“… 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 injury. And all victims are eventually in pain.”

He notes that pain is typically accompanied by other stresses, anxieties, and fears. There is also the factor of ‘public display’ which involves socially acceptable ways to deal with pain in a social setting.

He briefly discusses torture and reactions to it. When one is helpless and uncertain of the future there is fear and often shame too. He notes that fear of the manner of dying is often much greater than fear of death itself. He also discusses masochism and even notes that that athletes, with their “no pain, no gain” mantra can also be masochistic in a sense. There are sexual masochists who associate pain with sexual pleasure. There are also religious ‘flagellants,’ masochists, and ascetics who associate pain with redemption and symbolic atonement for sins.

He discusses the philosophy of pain, mostly mind-body dualism and particularly its flaws, but concludes that pain is best studied in terms of an integrated mind-body-sensory system. Our language may express this dualism as in the statement “my foot is hurting me,” but really mind and body can hardly be separated. According to Descartes, sensation was simply the mental representation of a stimulus. Descartes came up with all sorts of mechanisms to describe the mind-body connection in terms of his dualistic idea but was stumped even in his own time by such things as phantom limbs – which he explained away as “false signals.” The author suggests that mind-body dualism was reinforced by the Church as an integrated body-mind would be thought heretical. More modern dualists (he mentions John Eccles and Karl Popper) tend to see the body as being directed by the conscious mind. Bertrand Russell suggested sensation as a passive input analyzed by an active brain – but the author notes that there is evidence that brain activity controls the input. Thus he concludes that sensation includes active participation of both mind and body. Also discussed are trance-like behaviors such as peak athletic or artistic performance. Here complex motor activity is performed in a relaxed “mindless” state. These are perhaps examples of optimum mind-body integration states.

Aristotle generally defined six types of tactile sensation: touch, warm, cold, pain, tickle, and itch. Each sensation was thought to be a combination of those ‘primaries’ but the author notes that the terms are not comparable as some describe the stimulus (touch, warm, cold) and some the sensation (pain, tickle, and itch). The International Association for the Study of Pain came up with a definition of pain:

“Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.” They also added that:

“Pain is always subjective… This definition avoids tying pain to the stimulus.”

The classical view has it that stimulus leads to pure sensation which leads to perception but the modern view notes that these events may or may not lead to the others. Tissue damage does not directly correlate to pain. Sensation and perception can hardly be separated.
Ronald Melzack classified types of pain based on descriptions. He came up with 10 types of sensory pain: temporal (such as throbbing), spatial (such as shooting), punctuate pressure (such as stabbing), incisive pressure (such as cutting), constrictive pressure (such as crushing), traction pressure (such as tugging), thermal (hot or cold), brightness (such as stinging, tingling), dullness (such as sore), and misc. (such as tender). In addition, he describes 5 types of affective pain: tension, autonomic, punishment, and misc. along with words that evaluate pain on a scale- ie. mild to excrutiating or annoying to unbearable. Indeed each classification has words along a scale from mild to severe. The chart is given and is known as the McGill pain questionnaire and it has been noted that patients exhibiting certain diseases and maladies will describe the pain similarly. Melzack noted the three ways people described their pain: sensory, affective, and evaluative.

The next chapter title is: The Body Detects, the Brain Reacts. This is the most technical chapter and notes what happens in the body when tissue damage occurs. Her are described structures and functions that relate to sensory experience, the immune system, and bodily healing strategies. The sensory nerve fibers signal the spinal cord by two methods: 1) production of nerve impulses and 2) chemical formation and transport from zones in and around (damaged) tissue – much slower than nerve impulses. Immediate response to tissue damage involves nerve impulses propagated along nerve fibers. Three changes may invoke the pain: pressure, temperature, or chemical (ie. hot pepper, insect sting, etc.). Secondary responses include the emitting of peptides which dilate blood vessels. Tissue damage creates damaged cells which leak their chemicals into other tissue. Such leakage and breakdown of the chemicals by enzymes into smaller chemicals is a major cause of pain. A very common tertiary response to tissue damage is inflammation, characterized by swelling, redness, heat, and pain. Leaking fluid, white blood cell invasion, and chemical breakdown products are causes of inflammation. The final stage is the reparation process which involves structures called C fibers and scarification tissue building blocks called fibroblasts. The spinal cord is the two-way communication pathway between nerves and brain. Interestingly, he describes the biological/neurological basis of rubbing/scratching/massage/cold water for immediate pain, say in the case of hitting one’s thumb with a hammer: “You are stimulating large, low-threshold A beta fibers, which in turn are stimulating the small white cells that diminish the firing of the big white cells.” Apparently the brain can send other signals that may mitigate the feeling of pain through distraction. Bombardment of C fibers aided by emission of peptides leads to a secondary pain that comes later, after the initial (usually sharp) pain. In surgery the initial pain is anesthetized but the second phase comes after surgery. Cut nerves may cause a tertiary phase where excitability of the spinal cord transmitting system is enhanced. Sensory messages (in both directions) involve multiple parts of the brain. Wall seems quite certain there is no single “pain center” in the brain as Descartes suggested. Wall’s summary is as follows:

“When tissue is damaged, a sequence of events produces inflammation with pain. The spinal cord is informed of tissue damage by way of sensory nerves. Cells in the spinal cord react immediately to the input, but the amount of their output depends on small cells  that can enhance or diminish the output message.”

Spinal cord cells become sensitive after receiving injury messages. Further messages from the brain either amplify or reduce the output messages.

Conscious awareness of pain is often a focused state. Wall notes the ideas of psychologist William James in describing some emotions as awareness of body reactions to an event. If a stimulus occurs we may have a startle response. We may orient and explore the stimulus. We may have hyper attention or a muscle response.

“Attention is an integral part of pain. Pain captures and monopolizes attention and includes an interruption of any activities not directly related to pain relief.”

People, most often children, with a very rare condition called - congenital analgesia – do not feel pain, yet they learn to avoid certain responses. The condition may fade as they get older but if it doesn’t they can suffer tissue damage that does not heal, becomes infected by bacteria, and kills them. They do not feel the first phase of pain. The damage is caused because the second phase of pain, which they also do not feel, has an inflammatory then restoration function which does not occur because they do not protect, and hold still the injured area which provides a protective function against infection. So pain has a protective role, not in the acute stage but in the secondary phase that bids us to avoid re-damaging currently delicate tissue.

Wall mentions the work of Claude Bernard and Hans Kosterlitz who surmised that plant poisons led us to discover similar mechanisms in the body such as the chemical acetylcholine that causes muscles to contract. Later, naturally occurring opiate-like compounds (endorphins and enkephalins) were discovered and these brain-made narcotics explain the pain relieving function of concentrated narcotics. Apparently modern PET scans of the brain responding to pain show that classical definitions of the mechanism of pain and pain relief are lacking. Experiments show that humans all have more or less the same pain threshold. The difference is what happens after that threshold is crossed. Psychological tolerance to pain varies. Pain tolerance may be influenced by culture as in the behavioral ideal of the hero who tolerates pain and difficulty. Tribal initiations can include pain induction. One may be inspired by others or simply resolve to be Spartan and Stoic and accept pain as a duty. The author does note that much of culturally-induced pain tolerance is temporary and situational as later in life heroes may wimper at mild discomforts! Another form is that of Christians who attempt to emulate their hero Jesus by undergoing his sufferings in various ways from ritualistic emulation to simply being more stoic. The author states that he does not believe in the existence of pure sensation divorced from perception and I would definitely agree. He notes also that there is no evidence that genetics play a role in pain experience. Indeed, pain varies in the same person depending on circumstances. Studies that show differences in pain tolerance of different ethnicity are in doubt by the author. He thinks that the differences are simply cultural differences in public display of pain. People are simply bound by custom in this regard.

Wall explores hypnotism and acupuncture as anesthesia. He concludes that they have very real anesthetic effects but that the key to these affects is mainly the placebo effect in conjunction with the anesthetist-patient trust/expectation relationship. Verbal cues can be a key to hypnosis as well.

Recent fMRI images of the brains of people subjected to the same pain stimuli show quite varied responses in the brain. This was surprising. The amount of pain reported by the subjects also varied. This suggests that we each have different personalized strategies to deal with pain.

He discusses pain after surgery and notes that post-operative treatment has improved in that doses of pain relievers are now often tailored to the needs of the individual rather than giving set doses at set times. There are psychological difficulties too as immobilized patients feel helpless and can suffer shame.

Pain with obvious causes is examined. A scratch, a twisted ankle, a toothache, a heart attack, osteoarthritis, childbirth (an example of pain without illness), cancer, and amputation are discussed. Cancer may or may not be painful, especially in its early stages. Childbirth is rated high on the pain scale rather universally. In many situations/conditions the causes of pain migrate as they are related to sequential changes in the body. In the case of amputation the brain invents a phantom limb after receiving false signals that it is still present. Wall notes that the pain one feels is influenced by the pain one expects to feel with a given injury. The expectations of others, including doctors (especially when a patient still feels pain long after treatment), also influence one’s pain tolerance, emotional reactions, and public display.

Pain without known causes is also discussed. Headache, back pain, repetitive-stress injury, fibromyalgia, myofascial pain, and orphan pains are analyzed. Though there are many known causes of headache and back pain there are also unknown and undiscovered causes of these and the others. This has created much difficulty and frustration with diagnosis, insurance appropriation, and lack of pain relief. Some have attributed some back pain and repetitive-stress injury to self-inflicted psychological causes. While psychology may be part or much of the cause it is still real pain and should not be brushed off and left untreated, says Wall. He thinks orphan pains (symbolic pains invented by the psychology of the patient) are actually rarer than the literature depicts. Those pains may have an undiscovered cause or a cognitive component but are not strictly fictions of the mind as some have suggested, he thinks.

In discussing medicines Wall notes the difficulties in testing them, often against placebos. The history, use, and mechanism of aspirin and its antecedents as an anti-inflammatory medicine are recounted:

“… a crude herbal mixture was used for two thousand years, a purified extract for a century, and the precisely synthesized chemical for another seventy years before the rational for the use of aspirin was discovered …”

“Aspirin has a subtle effect on only one part of the inflammatory pathway, but it reduces pain and swelling and fever.”

It was shown that aspirin works by blocking a pathway through which damaged cells make prostaglandins during the inflammatory process.

The use of opiates is covered. In the middle of this century it was thought by doctors that opiate use was dangerous due to addiction but others figured out how to use lower doses for the analgesic effect. Dame Cicely Saunders, a founder of the modern hospice movement, championed their use among cancer patients and the terminally ill in pain. Now it is also common to have weaker narcotics combined with aspirin given in hospitals and pain prescriptions. Even cannabis is now being used legally and successfully as relief for many aliments. Similar to the situation with opiates, the brain produces chemicals similar to the cannabinoids of cannabis. Antidepressants work by increasing the level of certain neurotransmitters such as serotonin. These may improve mood but also may decrease incoming pain signals from the spinal cord. Research with pain relieving drugs is aimed at increasing the analgesic effect and reducing side effects.

Also discussed are surgical operations to reduce pain. He recounts some of his own experiences in this regard as well, with varying levels of success. Some surgery may even make the pain worse.

Other therapeutic methods are covered including yoga, massage, relaxation, exercise, acupuncture, manipulation, osteopathy, and stimulation. Each seems to have merits and limitations in regards to pain.

I found the chapter on the placebo response to be quite interesting. He notes that the placebo/nocebo effect is based on expectation. Its association with quackery is rather unfortunate and many doctors seek to trivialize it or to suggest that it only works for imagined pains. But the evidence is to the contrary. He notes that new drugs need to be proven to be better than a placebo and that this is much more difficult than it appears. Studies designed to test the placebo effect have yielded fascinating results. The placebo effect can also be implicated in other therapies and even in the success or failure of surgery. Apparently, the body can react to our strongly held expectations. Certainly we are conditioned by our experiences which influence our expectations. Placebos can mimic the physiological effects of drugs, even of potent narcotics. Fake surgery has given long-term results in some cases due to the power of expectation. Interestingly, experiments have shown that placebo/nocebo responses also occur in animals. They too have expectations based on previous experiences. This led to the effect being explained as a form of Pavlovian classical conditioning. Certainly, such conditioning is an aspect of the effect, but Wall strongly thinks there is more to it:

“The placebo response is the fulfillment of an expectation. Expectations are learned by individuals, and if enough individuals share the same expectations it is called a culture.”

The doctors in their white coats tend to support an expectation of healing. “Society itself is changed by its belief in medicine and surgery.”  “The placebo response is played out on the stage of expectation, which is created by the patients and their experience and culture, by the reputation of the therapy and by the attitude of the therapists.”

One experiment in 1978 used a narcotic suppressant to show that the pain relief due to the placebo response was indeed produced by the body’s endogenous narcotic system through the release of endorphins. This study conclusively showed that expectation can cause very real and powerful bodily reactions.

Wall is convinced that there is a cognitive component to the placebo response, that it is not simply a conditioned response. Belief and expectation are certainly cognitive in nature. The effect is not simply mechanical as some have suggested, it is learned and shaped by previous experience and individual and cultural expectation. The author also points out that in any therapy there is a placebo component.

Wall states that understanding the basis of one’s own pain can have a therapeutic effect. In describing the necessity of attention in experiencing pain he notes that all species seem to have a set of rules for selective attention to the vast input of the sensory world. He suggests that like large, sudden, and novel movements are noticed by our survival oriented  awareness so too is tissue damaged dealt with (noticed) by bodily actions. Our attention mechanism scans and selects. It may order attention which may explain some painless injury where overcoming tissue damage in order to get out of danger overrides pain. Injured warriors and athletes can sometimes perform quite well. Pain demands attention. Distraction has been a successful therapy to pain at least temporarily. This is the basis of many folk remedies (like certain balms) and often how we deal with injuries of toddlers. Cognitive therapy is a form of distraction therapy too as pain can be daydreamed away to some extent with training. When pain appears the body is on alert and reorganizes/reorients. The body stiffens. The painful area is explored with mind and often with hands. The protective role of the inflammation process may become maladaptive when prolonged which may lead to chronic pain. The body has a strategy of holding the body part or area of injury still by stiffening muscles to facilitate the healing process. This may be overemphasized and result in further pain. Such pain can be eased by biofeedback training where one may learn to relax the stiffness. The over-stiffness is accompanied by a belief that the pain caused by moving an injury will lead to further injury. This is often not the case, says Wall. I experienced this recently after taking a fall on the ice and hurting my wrist. Having plans for a blues guitar jam the next day I thought I might have to cancel but I moved it around and it turned out OK – however side plank in yoga class on that side was not an option.

Wall proposes an alternative theory to how we deal with pain. He says that:

“The brain analyzes the input in terms of what action would be appropriate.”

The parts of the brain associated with motor planning are implicated in reaction to pain. The brain scans for motor action that would be appropriate to the input, he says. The same motor planning system is involved in mimicry and learning by copying. He even suggests that all sensory events may be analyzed by scanning and selecting the appropriate motor responses. He then gives what he sees as the appropriate motor responses to an arriving injury signal:

“… first to remove the stimulus; second, to adopt a posture to limit further injury and optimize recovery; and third, to seek safety, relief, and cure.”

Through learning, growing up, and cultural influences we learn to hone our expectations. We learn that particular actions are followed by relief and so we apply them when needed. Thus, we each develop a particular strategy in responding to pain that is colored by our previous experiences.

“Pain is then seen as a need state, like hunger and thirst, which are terminated by a consummatory act.”

Pain is almost always accompanied by fear and anxiety. Fear of debilitation can be a factor and lead to further anxiety. These anxieties can focus the attention on the pain. Chronic pain sufferers may fall into depression. Feeding these emotional states back into attention on the pain can make pain harder to bear, suggests the author. It is psychosomatic (like the placebo effect) and can be quite powerful. Treating these emotional states may not make the pain go away but can make the pain easier to deal with. Strategies for coping with pain are needed. The first step in coping is to successfully deal with the accompanying fear, anxiety, and depression. Pain is a syndrome in this respect and each aspect of the syndrome should be treated.

There is an interesting section on dealing with the pain of others. Caregivers can help others deal with pain but they can also be negatively affected by the person in pain and their emotional orientations. Misery tends to be privatized in many modern cultures so that can be a barrier to therapy. Sometimes alternative therapies can be more effective than medical ones. This may be due to the therapist giving more time and attention to the patient and the buildup of expectations of success. It seems that coping is the key. Just as the brain has a strategy for finding the appropriate reaction to injury and that strategy may be the origin of pain, the mind can develop a strategy for coping that can be fine-tuned. In contemplating this, it seems to me that everyday life is a coping strategy! I have noticed too that animals will mask pain. This may be for survival reasons as injury is a vulnerability that can be exploited.

He goes through the medical profession’s strategies for dealing with pain. He notes that pain relief is not emphasized enough as are cause and cure. He thinks it is not studied enough in medical schools – after all pain is the primary reason someone visits a doctor. Some hospitals now have acute pain teams. There are pain clinics. There is hospice care and palliative care. Focus on rehabilitation can be useful. Patients groups are an option. He suggests that the early days of pharmaceutical companies led to many important medical discoveries but now they are overly focused on profits. Newer biotech firms may take up the discovery spirit. He wants more researched focused on pain and pain relief. Society (and insurance companies) may belittle people’s pain, especially if the causes are not clear. There are also people who believe that people such as that are faking pain for various reasons or it is entirely imaginary. This relates to the depiction of people on welfare and disability as being frauds or fakes – most of whom are not.

“Pain is one facet of the sensory world in which we live. It is inherently ridiculous to consider pain as an isolated entity, although many do exactly that. “… Pain is not just a sensation but, like hunger and thirst, is an awareness of an action plan to be rid of it.”

I am glad I read this one. I agree that knowledge of such a subject as pain might be therapeutic as learning to cope can be a key to dealing with it successfully. May all those dealing with pain deal with it well and learn to be pain-free.

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