Intellectual Milestones in Our Understanding and Treatment of Pain
G. F. Gebhart
Through the ages, pain and suffering have been the primary reasons why patients sought medical care. But what pain is (an independent sense, an emotion, an experience, …) has been considered and argued by philosophers and investigators alike to the present day. The International Association for the Study of Pain (www.iasp-pain.org) defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.” Pain is always a subjective, personal, and unpleasant experience. This chapter reviews ideas and concepts about pain, including how our mental constructs shape our understanding, and then treatment of this complex experience we call pain. This chapter closes with a discussion of how the medical subspecialty is evolving within the broader context of medical specialization and thoughts for future development.2
Pain Understood as Part of a Larger Philosophy or Worldview
Since the beginning of time, humans have been born through a painful process, and the experience of suffering remains universal. The meaning of pain reflects the contemporary spirit of the age and, therefore, has changed over recorded history as worldviews changed. Among the earliest systems of pain management, dating back to the Stone Age, was Chinese acupuncture, theoretically based on the philosophy of imbalances of yin and yang affecting qi and blood flow. Thousands of years ago, Egyptians considered the experience of pain to be a god or disincarnate spirit afflicting the heart, which was conceptualized as the center of emotion. Galen, and later Aristotle, described pain as an emotional experience, or “a passion of the soul.”3
An important concept dating from antiquity that persisted until the 19th century was the theory of importance of the four humors. This worldview was espoused by Greek philosophers in approximately 400 BC and later applied to medicine by Hippocrates, who described humors as related to one of the four constitutions, shown in Table 1.1. Seasonal changes evoked pain, and certain disorders, such as migraine, were associated with specific humors (e.g., excessive cold humors thought to result in a mucus discharge requiring application of “hot effusions” to the head).
Consistent with this ideology was the custom of treating pain by applying “opposites” such as hot applications to the head to counterbalance and evacuate “cold” humors of headaches.5 Based on the humor theory and treatment by “opposites” was a technique called cupping. Warm suction cups were applied to the skin that on cooling resulted in raised reddened welts thought to “draw out” any unbalanced humors.6
Later, during the Middle Ages, coincident with the spread of Christianity, pain, not surprisingly, was explained in a spiritual, religious context. Medieval life has been described as short, cheap, and brutish, especially for the lower classes, with pain accepted as the universal lot of mankind. Little is known of how pain was actually treated during this period, but a suffering Christ, martyred saints, and the concept of physical pain in purgatory originated around the 12th century AD.6,7 Commonly revered was the iconography of tortured saints with ecstatic faces depicting pain as a spiritual discipline bringing the saints closer to God, relieved primarily by prayer and meditation. A clear example of pain as ennobling was St. Ignatius Loyola’s habit of wearing ropes and chains cutting into the skin and encouraging other humiliations of the flesh to enhance his spiritual development.3
An interesting example of pain as a function of the sociologic concepts of the day is the rise and fall of the diagnosis of hysteria, common in the 17th century and virtually nonexistent today. Thomas Sydenham (Fig. 1.1), in 1681, wrote, “Of all chronic diseases hysteria—unless I err—is the commonest.”8 The cardinal symptom of this condition was unexplained pain. In mid-19th century Europe and America, hysteria was virtually everywhere, found in every community. Invalids, mostly females, filled homes, spas, and convalescent facilities at the turn of the 19th century. This mysterious syndrome, afflicting
only middle and upper class females, was treated by complete social isolation, confinement to bed, and a total prohibition on any form of intellectual activity, even sewing or reading (CP Gilman as quoted in Rey9). As the social situation and educational opportunities for women improved, this disorder almost totally disappeared, a public health success on the order of magnitude of the eradication of yellow fever. In the 21st century, fibromyalgia, although a commonly diagnosed condition in Western countries, interestingly enough, is either underreported or not significantly present in Asian and developing country populations.
only middle and upper class females, was treated by complete social isolation, confinement to bed, and a total prohibition on any form of intellectual activity, even sewing or reading (CP Gilman as quoted in Rey9). As the social situation and educational opportunities for women improved, this disorder almost totally disappeared, a public health success on the order of magnitude of the eradication of yellow fever. In the 21st century, fibromyalgia, although a commonly diagnosed condition in Western countries, interestingly enough, is either underreported or not significantly present in Asian and developing country populations.
TABLE 1.1 Relationships in Antiquity between the Four Humors, Elements, Constitutions, and Seasons4 | ||||||||||||||||
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 FIGURE 1.1 Thomas Sydenham. (Courtesy of the National Library of Medicine.) |
Another very clear link between mental state and the perception and control of pain is apparent in the work of the German physician Franz Anton Mesmer. In 1766, he published his doctoral dissertation entitled “On the Influence of the Planets on the Human Body,” describing animal (or life spirit) magnetism as a force to cure many ills.10 He used iron magnets to treat various diseases, amplifying the magnetic fields with room-sized Leyden jars. His demonstrations of his technique, combining hypnotism with spectacle, included the wearing of brightly colored robes in dimly lit ritualistic séances, with soft music playing from a glass harmonium. He invoked magnetic power with poles either held or waved over the patient and his techniques were an early rival to ether anesthesia as a way to relieve pain during surgical procedures.11 Mesmerism was such a common form of pain therapy during his day that Robert Liston reportedly exclaimed after the successful administration of ether anesthesia in an early above-knee operation, “This Yankee Dodge beats mesmerism hollow.”12 Mesmerism was based on the larger generally accepted theory of vitalism which posited that every part of a living thing was endowed with sensibility. The energy or force which animated a living organism was capable of being stimulated or consumed. In disease, pain was necessary to produce a “crisis” which rid the patient of original pain by stimulating the diminishing energy.6
A further development of the link between mind and body and the understanding of pain was the landmark development of Freudian theory in understanding subconscious influences on pain perception and behavior. The link between the unconscious mind and physical sensation in hysterical conversion disorders was posited as an explanation for psychogenic pain and continues to be influential today. This conceptual paradigm was expanded in the 1970s by the psychiatrist George L. Engel who demonstrated the link between chronic pain and psychiatric illness.13 Later, psychiatrists, psychologists, and social scientists, including Thomas Szasz,14 Allan Walters,15 and Harold Merskey,16 explored social situations, psychological character traits, and the effects of past life experiences in understanding chronic pain in patients. Depression, stress, and personality, in addition to physiologic mechanisms, have proven to be critical grounds for investigation and therapy. From these early studies, investigating the mind-body interface of pain grew the cognitive-behavioral school of pain therapy in the 1980s that is widely employed today, emphasizing the development of coping mechanisms to deal with chronic pain as a basic component of interdisciplinary pain programs. The concept of pain, not only as a physiologic response to stimuli but as a more complicated construct, incorporating social, behavioral, and psychological responses as well, is an intellectual milestone that has inspired a wealth of investigations and patient treatment options. New areas of investigation now include pain in relationship to social setting, gender, national, ethnic, and racial background as well as differences in coping ability and psychiatric comorbidities. Considerations of vocational and legal environment as well as family and interpersonal dynamics are also relevant to the understanding and care of individual patients.
This global philosophy of pain as only part of an entire life experience can best be summed up in the words of Alexander Pope in his Essay on Man in 1733:
Say what the use, were finer optics giv’n,
T’ inspect a mite, not comprehend the heav’n?
Or touch, if tremblingly alive all o’er,
To smart and agonize at ev’ry pore?
Or, quick effluvia darting thro’ the brain,
Die of a rose in aromatic pain?17
Mechanistic Views of Pain
In counterpoint to the holistic philosophical consideration of pain was mechanism, the philosophical mind set suggesting that the human body functions as a simple machine with pain being the result of its malfunction.18 This viewpoint is clearly seen in Descartes’ Passions of the Soul in 1649 where he compares a human being to a watch:
[T]he difference between the body of a living man and that of a dead man is just like the difference between, on the one hand, a watch or other automaton (that is, a selfmoving machine) when it is wound up and contains in itself the corporeal principle of the movements for which it is designed …; and, on the other hand, the same watch or machine when it is broken and the principle of its movement ceases to be active.19
How did the mechanistic view of the body develop and even supersede traditional theologic and philosophical explanations for pain? Early anatomical studies were conducted beginning with Galen of Pergamum (130-201 AD) and Avicenna (Fig. 1.2), the Persian Muslim polymath
(980-1037 AD), forming an intellectual basis for pain as an actual physical sensation rather than as a mental, spiritual dilemma. Later, in the 14th through 17th centuries, the Renaissance cultural movement questioned the basis of all knowledge, including ideas about the human body and the experience of pain. Empiricism and the development of scientific inquiry with direct observation into the mysteries of life became the basis for advances in both medical understanding and treatment, including the now commonly accepted neurologic basis of pain. Extended wars on the continent between France and Spain resulted in bullet and musket ball injuries that tore the skin, forcing surgical removal and amputation. Wounds were bound and foreign bodies extracted, originally posited to prevent leakage of the “vital force” or to inhibit the entrance of animal spirits into the injured body. Gradually, direct observation of the circulation of the blood by William Harvey20 in 1628 and the direct anatomical studies of Descartes (Fig. 1.3)19 in 1662, elucidating sensory physiology became the theoretical basis for further exploration in the 18th and 19th centuries.
(980-1037 AD), forming an intellectual basis for pain as an actual physical sensation rather than as a mental, spiritual dilemma. Later, in the 14th through 17th centuries, the Renaissance cultural movement questioned the basis of all knowledge, including ideas about the human body and the experience of pain. Empiricism and the development of scientific inquiry with direct observation into the mysteries of life became the basis for advances in both medical understanding and treatment, including the now commonly accepted neurologic basis of pain. Extended wars on the continent between France and Spain resulted in bullet and musket ball injuries that tore the skin, forcing surgical removal and amputation. Wounds were bound and foreign bodies extracted, originally posited to prevent leakage of the “vital force” or to inhibit the entrance of animal spirits into the injured body. Gradually, direct observation of the circulation of the blood by William Harvey20 in 1628 and the direct anatomical studies of Descartes (Fig. 1.3)19 in 1662, elucidating sensory physiology became the theoretical basis for further exploration in the 18th and 19th centuries.
 FIGURE 1.2 Avicenna. (Courtesy of the National Library of Medicine.) |
19TH CENTURY—PAIN AS A SPECIFIC SENSE
In 1811, Charles Bell (Fig. 1.4), an anatomist in Edinburgh, Scotland, published a monograph in which he described new and important evidence for the specificity of function of peripheral nerves. Bell proposed differences in function between the dorsal and ventral roots of the spinal cord, writing that “… the nerves of sense and nerves of motion … are distinct …”21 Bell’s discovery that ventral root stimulation controlled muscle contraction was followed by François Magendie’s (Fig. 1.5) report in 1822 that sectioning posterior (dorsal) nerve roots resulted in paralysis and insensibility of the corresponding
limbs, confirming that the dorsal roots are afferent.22 The result of these discoveries regarding the functions of the spinal roots is now known as the Bell-Magendie law (confirmed in 1831 by Johannes Müller).
limbs, confirming that the dorsal roots are afferent.22 The result of these discoveries regarding the functions of the spinal roots is now known as the Bell-Magendie law (confirmed in 1831 by Johannes Müller).
 FIGURE 1.3 René Descartes. (Courtesy of the National Library of Medicine.) |
 FIGURE 1.4 Sir Charles Bell. (Courtesy of the National Library of Medicine.) |
 FIGURE 1.5 François Magendie. (Courtesy of the National Library of Medicine.) |
Johannes Müller (Fig. 1.6)23 was a precocious and influential German investigator who advanced in 1826 at the age of 25 years the Law of Specific Nerve Energies, which laid out the basic concept of modern sensory physiology (cf. Handwerker and Brune24). Müller’s “law” emphasized that the quality of sensation depends not on the stimulus but on the sense organ and sensory pathway stimulated. Müller’s law was not advanced in the context of pain as he was studying at that time vision. He considered the sensation of sound to be the “specific energy” of the acoustic nerve, and the sensation of light the particular “energy” of the visual nerve. In 1858, Moritz Schiff25 established, based on studies of the effects of spinal cord lesions, that separate spinal pathways conveyed tactile, temperature, and pain sensations. On the basis of his studies, Schiff proposed that pain was an independent sensation (a specific sense). Schiff’s findings were subsequently confirmed and extended by Charles-Édouard Brown-Séquard and Sir William Richard Gowers, establishing the importance of spinal pathways for conducting information about painful stimuli applied in the periphery.
Alfred Goldscheider (Fig. 1.7) and Max von Frey (Fig. 1.8) were contemporaries, adversaries, and also important to the history of pain research.24 Their divergent interpretations and conclusions from their research fostered and supported debate about the “pain” sensitivity of pressure points in skin well into the 20th century. In 1881, Goldscheider, a German army physician, demonstrated in his dissertation (and independently of the Swedish physiologist Magnus Blix), spatially discontinuous warm and cold spots in the skin, thus confirming
Müller’s Law of Specific Nerve Energies. Goldscheider reported that stimulation of a cold point always produced the sensation of cold whether activated by a cold metal rod or by electrical stimulation. Goldscheider also reported that stimulation of temperature points did not produce a sensation of pain and advanced therefore the existence of tactile and pain points in skin.24,26
Müller’s Law of Specific Nerve Energies. Goldscheider reported that stimulation of a cold point always produced the sensation of cold whether activated by a cold metal rod or by electrical stimulation. Goldscheider also reported that stimulation of temperature points did not produce a sensation of pain and advanced therefore the existence of tactile and pain points in skin.24,26
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