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  1. 1. Pain: Definitions and Clinical Issues Roger B. Fillingim, Ph.D. University of Florida, College of Dentistry
  2. 2. Definition of Pain <ul><li>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) </li></ul>
  3. 4. The Impact of Pain
  4. 5. The Prevalence of Pain <ul><li>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) </li></ul><ul><li>An estimated 50 million people suffer from chronic pain in the United States (Joranson & Lietman, 1994) </li></ul><ul><li>23 million surgical procedures are performed annually in the U.S., most accompanied by significant post-operative pain (Peebles & Schneidman, 1991) </li></ul>
  5. 6. Pain and Health Care Use <ul><li>Pain is the number one motivator for utilization of health care </li></ul><ul><ul><li>Pain accounts for over 35 million new office visits to physicians and over 70 million total physician visits annually (Turk & Melzack, 2002) </li></ul></ul><ul><ul><li>Pain medications are the second most frequently prescribed class of drugs, and analgesics are the most frequently used non-prescription medicines (Isaacson, 2002) </li></ul></ul><ul><ul><li>Pain is the most frequent reason for seeking treatment in the emergency room (Cordell, et al., 2002) </li></ul></ul>
  6. 7. The Costs of Pain <ul><li>The total costs of chronic pain have been estimated at $125 billion per year (Turk et al., 1999) </li></ul><ul><li>The costs of treating pain exceed the combined costs of treating cardiovascular disease, cancer, and AIDS (Cousins, 1995) </li></ul><ul><li>The human costs, in terms of suffering and diminished quality of life, cannot be overestimated </li></ul>
  7. 8. 1 2 3
  8. 9. Gate Control Theory of Pain Melzack & Wall (1965) <ul><li>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. </li></ul><ul><li>Pain-related input can be inhibited by nonpainful signals from the same region. </li></ul><ul><li>Also, descending signals from the brain, based on thoughts and feelings can open or close the gate. </li></ul>
  9. 11. Commons Types of Clinical Pain <ul><li>Inflammatory pain </li></ul><ul><li>Musculoskeletal pain </li></ul><ul><li>Neuropathic pain </li></ul><ul><li>Vascular pain </li></ul><ul><li>Visceral pain </li></ul><ul><li>Cancer pain </li></ul><ul><li>Central pain </li></ul>
  10. 12. Features of Clinical Pain <ul><li>Spontaneous pain </li></ul><ul><li>Allodynia – pain due to a stimulus which does not normally provoke pain </li></ul><ul><li>Hyperalgesia – an increased response to a stimulus which is normally painful </li></ul>
  11. 13. Cervero & Laird, 1996
  12. 14. Acute vs. Chronic Pain <ul><li>Acute Pain </li></ul><ul><ul><li>Short duration </li></ul></ul><ul><ul><li>Known stimulus </li></ul></ul><ul><ul><li>Low to moderate psychological load </li></ul></ul><ul><ul><li>Serves protective function </li></ul></ul><ul><li>Chronic Pain </li></ul><ul><ul><li>Long duration </li></ul></ul><ul><ul><li>Stimulus vague or unknown </li></ul></ul><ul><ul><li>Moderate to high psychological load </li></ul></ul><ul><ul><li>Not protective, often maladaptive </li></ul></ul>
  13. 15. Common Chronic Pain Disorders 6:1 2-3% Fibromyalgia 1:1 ~ 70% lifetime Low Back Pain 9:1 0.5% Interstitial Cystitis 2.5:1 1% Rheumatoid Arthritis 1.5:1 – 4:1 > 80% (age 65) Osteoarthritis 2:1 15-20% Irritable Bowel Syndrome 1.5:1 4-12% Temporomandibular Disorders 2:1 4-5% Tension-Type Headache 2-3:1 15-20% Migraine F:M Ratio Prevalence
  14. 16. Other Clinical Pain Syndromes <ul><li>Complex Regional Pain Syndrome </li></ul><ul><ul><li>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 </li></ul></ul><ul><ul><li>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 </li></ul></ul><ul><li>Phantom Pain </li></ul><ul><ul><li>the experience of pain in a limb that has been amputated </li></ul></ul><ul><ul><li>occurs in 50-80% of amputees </li></ul></ul>
  15. 17. BIOPSYCHOSOCIAL MODEL OF PAIN BIOMEDICAL PSYCHOLOGICAL SOCIOCULTURAL - Pathology - Injury - Nociception - Age, Sex, Race - Income, Education - Social Milieu - Anxiety, Depression - Cognitive Factors - Behavioral Factors
  16. 18. The Clinical Relevance of Pain Neuroscience <ul><li>Diagnostic systems based on underlying mechanisms are more clinically useful than diagnoses based solely on symptoms </li></ul><ul><li>Pain neuroscience is the key to elucidating these mechanisms </li></ul><ul><li>Basic neuroscience research reveals targets for analgesic drug development </li></ul><ul><li>A better understanding of the neural mechanisms underlying normal and abnormal pain responses will permit prevention of chronic pain </li></ul>