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Slide 1: Pain: Definitions and Clinical Issues Roger B. Fillingim, Ph.D. University of Florida, College of Dentistry
Slide 2: Definition of Pain • An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage. … Activity induced in … nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state … (IASP, 1994)
Slide 4: The Impact of Pain
Slide 5: The Prevalence of Pain • In a recent survey, 29.6% of respondents reported experiencing pain the previous day and 43.2 % reported pain during the previous week (Catala, et al., 2002) • An estimated 50 million people suffer from chronic pain in the United States (Joranson & Lietman, 1994) • 23 million surgical procedures are performed annually in the U.S., most accompanied by significant post-operative pain (Peebles & Schneidman, 1991)
Slide 6: Pain and Health Care Use • Pain is the number one motivator for utilization of health care – Pain accounts for over 35 million new office visits to physicians and over 70 million total physician visits annually (Turk & Melzack, 2002) – Pain medications are the second most frequently prescribed class of drugs, and analgesics are the most frequently used non-prescription medicines (Isaacson, 2002) – Pain is the most frequent reason for seeking treatment in the emergency room (Cordell, et al., 2002)
Slide 7: The Costs of Pain • The total costs of chronic pain have been estimated at $125 billion per year (Turk et al., 1999) • The costs of treating pain exceed the combined costs of treating cardiovascular disease, cancer, and AIDS (Cousins, 1995) • The human costs, in terms of suffering and diminished quality of life, cannot be overestimated
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Slide 9: Gate Control Theory of Pain Melzack & Wall (1965) • This theory suggested that there is a “gate” in the spinal cord (and the brain stem) that modulates the transmission of pain signals to the brain. • Pain-related input can be inhibited by nonpainful signals from the same region. • Also, descending signals from the brain, based on thoughts and feelings can open or close the gate.
Slide 11: Commons Types of Clinical Pain • • • • • • • Inflammatory pain Musculoskeletal pain Neuropathic pain Vascular pain Visceral pain Cancer pain Central pain
Slide 12: Features of Clinical Pain • Spontaneous pain • Allodynia – pain due to a stimulus which does not normally provoke pain • Hyperalgesia – an increased response to a stimulus which is normally painful
Slide 13: Cervero & Laird, 1996
Slide 14: Acute vs. Chronic Pain • Acute Pain – Short duration – Known stimulus – Low to moderate psychological load – Serves protective function • Chronic Pain – Long duration – Stimulus vague or unknown – Moderate to high psychological load – Not protective, often maladaptive
Slide 15: Common Chronic Pain Disorders Prevalence Migraine Tension-Type Headache Temporomandibular Disorders Irritable Bowel Syndrome Rheumatoid Arthritis Osteoarthritis Interstitial Cystitis Fibromyalgia Low Back Pain 15-20% 4-5% 4-12% 15-20% 1% > 80% (age 65) 0.5% 2-3% ~ 70% lifetime F:M Ratio 2-3:1 2:1 1.5:1 2:1 2.5:1 1.5:1 – 4:1 9:1 6:1 1:1
Slide 16: Other Clinical Pain Syndromes • Complex Regional Pain Syndrome – Type I: (formerly Reflex Sympathetic Dystrophy): a syndrome that develops after an initiating noxious event, is not limited to the distribution of a single peripheral nerve, and is apparently disproportionate to the inciting event – Type II: (formerly causalgia): Burning pain, allodynia, and hyperpathia usually in the hand or foot after partial injury of a nerve or one of its major branches • Phantom Pain – the experience of pain in a limb that has been amputated – occurs in 50-80% of amputees
Slide 17: BIOPSYCHOSOCIAL MODEL OF PAIN BIOMEDICAL - Pathology - Injury - Nociception SOCIOCULTURAL - Age, Sex, Race - Income, Education - Social Milieu PSYCHOLOGICAL - Anxiety, Depression - Cognitive Factors - Behavioral Factors
Slide 18: The Clinical Relevance of Pain Neuroscience • Diagnostic systems based on underlying mechanisms are more clinically useful than diagnoses based solely on symptoms • Pain neuroscience is the key to elucidating these mechanisms • Basic neuroscience research reveals targets for analgesic drug development • A better understanding of the neural mechanisms underlying normal and abnormal pain responses will permit prevention of chronic pain