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Placebo Analgesia

SUMMARY The expectation of pain relief can exert a powerful analgesic effect, even when the pain is severe. Depending on the nature of experiences and instructions provided, a placebo analgesic effect can be elicited acutely in a very large percentage of individuals in both experimental and clinical contexts. Placebo analgesia has been linked with activity in the prefrontal cortex, endogenous opioid release in both the descending…

Pain, Opiates, and Addiction

SUMMARY Over the years there has been a paradigm shift away from the belief that the use of opiates for the relief of chronic pain would inevitably lead to addiction toward an understanding of the complexity of pain relief and opioid addiction. Addiction is now regarded as a chronic relapsing disease characterized by compulsive drug taking, yet the progression from opiate abuse to opiate addiction is…

Hypnotic Analgesia

SUMMARY Modern medical hypnosis is increasingly being recognized as a valid method of pain control based on accumulating evidence demonstrating robust effects on the physiological manifestations of pain-related processes. Besides the operational description of the conditions under which hypnosis is typically produced, hypnosis-related phenomena can be described in relation to changes in brain activity, cognitive processes, and subjective experience. A variety of techniques and strategies can…

Assessment of Pain Beliefs, Coping, and Function

SUMMARY Individual differences in the experience and impact of pain necessitate the inclusion of cognitive, affective, and functional measures in the assessment of pain, particularly persistent pain. A rich and diverse literature documents the role that pain beliefs and attitudes and pain-coping strategies have on outcomes, including pain severity and the impact of pain on function. This chapter reviews the measures that are commonly used in…

Measurement and Assessment of Pediatric Pain

SUMMARY Appropriate management of pain in children depends on valid and reliable assessment and measurement that is implemented regularly and responded to appropriately. Significant improvements in pediatric pain measurement have been made in the past 25 years, and many acceptable measures of “short, sharp” pain are now available for all children and excellent measures of pain for children who can self-report. At this time there are…

Pain in Older Persons

SUMMARY This chapter provides an overview of research into pain and aging, including pain assessment and age-related patterns of pain intensity and prevalence. Older people are less likely than younger people to report pain associated with acute pathology, whereas age differences in postoperative and cancer pain remain unclear. Although the prevalence of chronic non-cancer pain may peak at midlife and decrease or plateau thereafter, it remains…

Pain Measurement in Adult Patients

SUMMARY Pain is a personal, subjective experience that consists of sensory–discriminative, motivational–affective, and cognitive–evaluative dimensions. Accurate, valid, and reliable measurement of pain is essential if we are to (1) better understand the factors that determine pain intensity, quality, and duration; (2) improve diagnosis and treatment of pain; and (3) ensure accurate evaluation of the relative effectiveness of different therapies. Approaches to the measurement of pain include…

Studies of Pain in Human Subjects

SUMMARY Studies of pain mechanisms in normal, pain-free individuals provide a degree of experimental control not found in studies of clinical pain and open a window to the experience of pain that is not available in controlled studies with laboratory animals. The ultimate goal of these studies is to improve the treatment of people in pain. Pain studies in normal individuals approach this goal by improving…

Psychiatric Pain–Associated Co-morbidities

SUMMARY Co-morbidity is defined as “any distinct clinical entity that has existed or may occur during a patient’s clinical course that has the index disease under study” ( ). Co-morbidity is important because co-morbid disease can complicate, interfere with, or make treatment of the index disease more difficult, thereby worsening the prognosis. The hallmark characteristic of a chronic pain patient is co-morbidity . Co-morbid conditions in…

Cognitive and Learning Aspects

SUMMARY Pain is an experience that affects the entire person; it involves a learning history and occurs within a social context. As a consequence, pain is much more than a sensation or a symptom of a disease. Pain involves not only physiological processes but also emotional responses, cognitive evaluations, and behavioral responses and instigates learning processes. Chapter 17 deals with the emotional components of the experience…

Emotion, Motivation, and Pain

SUMMARY There is no more potent a motive in life than to preserve the integrity of the self. Our existence as autonomous agents rests on the ability to detect a multiplicity of dangers and threats and respond to them both expediently and effectively. The most important signaling mechanism for imminent harm is the pain system, and it is unsurprising that the quintessential aversive nature of pain…

Epidemiology of Pain

SUMMARY Epidemiological studies, particularly within the past few decades, have greatly increased our understanding of the burden of chronic pain and the etiological factors implicated in its onset. In an adult population, the most common regional pain syndromes are those of low back, hip, and shoulder pain (between 25 and 35% of individuals will report such pain), whereas 10–15% will complain of widespread body pain. For…

Gender Differences in Pain and Its Relief

SUMMARY The topic of sex and gender differences in pain and analgesia has garnered progressively more interest from the pain research community over the last 15 years. The field has moved from asking whether there are meaningful sex or gender differences in pain to asking what conditions and mechanisms contribute to such differences. These questions have been explored in terms of both clinical and basic science…

Itch

SUMMARY A specific neuronal pathway for histamine-induced itch in the peripheral and central nervous systems has been described. However, not all forms of itch are mediated by this pathway. Apparently, non-specific pathways also exist that are operational under physiological conditions. Exact delineation of the neuronal pathways for itch and pain has therefore become problematic. This review focuses on the neurophysiological mechanisms that underlie itch sensations under…

Autonomic, Endocrine, and Immune Interactions in Acute and Chronic Pain

SUMMARY Pain is a warning signal not only for local tissue or nerve injury but also as an indicator of systemic illness. Signaling by the autonomic, endocrine, and immune systems, coordinated by central neural circuits, produces changes perceived as pain, and dysregulation of these bidirectional signaling pathways may contribute to chronic inflammatory pain, neuropathic pain, generalized pain syndromes, and illness symptoms. This chapter summarizes the bidirectional…

Ascending Projection Systems

SUMMARY The ascending pathways that convey pain-related activity to the forebrain in humans include the lateral spinothalamic tract and indirect spinobulbar projections by way of brain stem homeostatic sites. Several areas in the thalamus relay pain-related activity to the cortex, including the posterior part of the ventral medial nucleus and the ventral caudal part of the medial dorsal nucleus, as well as the ventral posterior inferior…

Animal Models of Pain

SUMMARY Animal models of pain, usually rodents, support basic research on physiological and pathophysiological mechanisms, as well as applied research in drug discovery. Quantification of pain and analgesia relies on responses evoked by physical or chemical stimuli and modification of motor behavior in normal animals or following a variety of forms of injury. Electric stimuli are easy to regulate but bypass the nociceptor endings, recruit non-nociceptor…

Genetics of Pain

SUMMARY Pain is associated with considerable variability between individuals. Humans exhibit robust differences in their thresholds and tolerances to controlled noxious stimuli, in their analgesic response to drugs, and in their susceptibility to (and severity of) clinical pain syndromes. In fact, the central focus of pain research can be accurately cast as a question of individual differences: why does chronic pain eventually develop in only a…

Development of Pain Pathways and Mechanisms

SUMMARY Study of the development of pain pathways and mechanisms is fundamental to our understanding and treatment of the many infants and children around the world who suffer acute or chronic pain. Increasing evidence that exposure to tissue injury and excessive noxious input in early life can change the sensitivity of pain pathways in adulthood underlines the importance and impact of these studies. This chapter summarizes…

Central Nervous System Mechanisms of Pain Modulation

SUMMARY In this chapter we present an overview of pain-modulating systems with a focus on the properties of a network with major relays in the midbrain periaqueductal gray (PAG) and rostral ventromedial medulla (RVM). This network exerts bidirectional control over dorsal horn nociceptive transmission by means of separate anti- and pro-nociceptive output from the RVM. The PAG–RVM system is the central substrate for the actions of…