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Neuro Seminar Intro Lecture PPt.pptx

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Neuro Seminar Intro Lecture PPt.pptx

  1. 1. An Introduction to the Science of Pain – Myths and Realities Psychology Neuroscience Physiology
  2. 2. Epidemiology ■ Approximately 50 million Americans experience chronic pain ■ 18-34% of US population deals with chronic pain ■ Emphasizes critical need for pain management ■ Close to half of the American population will seek care for a pain problem at some point during their lives ■ 8% of Americans have “high impact” chronic pain
  3. 3. Epidemiology ■ Prevalence of low back pain ■ Any low back pain ■ 60-80% ■ Any back pain persisting at least 2 weeks ■ 7% ■ Back pain with features of sciatica lasting at least 2 weeks ■ 1.6% ■ Lumbar spine surgery ■ 1-2%
  4. 4. Epidemiology ■ Headache pain ■ 90% of Americans experience non-migraine headaches ■ Migraines ■ ~25 million Americans ■ Arthritis pain ■ 1 in 6 adults ■ Cancer pain ■ Majority of cancer pain patients experience some level of pain ■ Some statistics indicate that many of these patients do not receive adequate pain relief ■ Palliative care
  5. 5. Defining Pain ■ What exactly is pain? ■ How do you define pain? ■ Noxious – tissue damaging stimuli ■ Nociceptors – the receptors of the body that convey pain information ■ What are some of the ways you can describe pain? ■ Try to come up with terms to describe painful events…
  6. 6. What is pain? “Something that hurts.” UNC Student Female “Unpleasant sensation.” UNC Student, male “A signal that tells you that you should not be doing something. Tells you that something you are doing is bad.” UNC student, male “Pain means that you should stop.” UNC student, female “Something I don’t like. Try to avoid.” UNC student, male “Something bad, can be physical or emotional. Something you want to stay away from.” UNC student, female
  7. 7. Definitions of Pain ■ What do these definitions have in common? ■ Are these concepts of pain a product of evolution or are they produced by our experiences with pain? ■ Bonica’s studies with puppies ■ Completely isolated from pain experience ■ Fluffy environment ■ How did they react to painful stimuli?
  8. 8. Common Definitions of Pain ■ Most people define pain as a perception that occurs following tissue damage ■ This is a very dangerous misconception ■ Pain is designed as an early warning system ■ Pain occurs BEFORE tissue damage, as stimuli APPROACH tissue damaging range ■ So the organism can escape the potential injury!
  9. 9. What is pain? Pain: An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Note: Pain is always subjective. Each individual learns the application of the word through experiences related to injury in early life. Biologists recognize that those stimuli which cause pain are liable to cause tissue damage. It is unquestionably a sensation in a part or parts of the body, but it is also always unpleasant and therefore also an emotional experience. Experiences which resemble pain but are not unpleasant, e.g., pricking, should not be called pain. Unpleasant abnormal experiences (dyesthesias) may also be pain but are not necessarily so because, subjectively, they may not have the usual sensory qualities of pain. Many people report pain in the absence of tissue damage or any likely pathophysiological cause; usually this happens for psychological reasons. There is usually no way to distinguish their experience from that due to tissue damage if we take the subjective report. If they regard their experience as pain and if they report it in the same way as pain caused by tissue damage, it should be accepted as pain. This definition avoids tying pain to the stimulus. Activity induced in the nociceptor and nociceptive pathways by a noxious stimulus is not pain, which is always a psychological state, even though we may well appreciate that pain most often has a proximate physical cause. (International Association for the Study of Pain, 1979) Pain is what the patient says it is and exists when he says it does. (Meinhard and McCaffery, 1984)
  10. 10. The Meaning of Pain ■ “global” pain ■ all-encompassing multidimensional pain space ■ gestalt ■ Loeser (1980) ■ global pain should include ■ sensory qualities ■ suffering ■ pain behavior ■ many other potential components ■ motivation
  11. 11. The Meaning of Pain ■ Variety of meanings given to the word “pain” ■ Pure pain sensation ■ Somatosensory sensations ■ Emotional ■ Motivational ■ Cognitive ■ Suffering
  12. 12. Difficulties in Pain Measurement ■ Wall (1983) ■ pain is “always subjective” ■ Search for an objective pain measure, comparable between participants ■ No real objective assessments of a perceptual state ■ So, how can we assess pain?
  13. 13. What makes chronic pain so difficult? Social and psychological factors play a pivotal role in presentation and response to treatment Environment Social motivations Secondary gain
  14. 14. Parallel Processing Model of Pain Perception Emotional/Motivational Autonomic Discriminative Motor Reflex Spinal Input these many components of pain perception can interact with one another
  15. 15. Situational, Behavioral, and Emotional Factors and Pain Perception NOXIOUS STIMULUS Situational Factors Behavioral Factors Emotional Factors *expectation *control *relevance *coping style *overt distress *social response *fear *anger *frustration *competition PAIN SENSATION *sex *age *cognitive level *previous pains *family learning *culture A model of the situational, behavioral, and emotional factors that can modify pain perception. taken from McGrath 1990
  16. 16. Anatomy of Pain ■ Primary systems for pain perception ■ Receptors - nociceptors ■ C fibers ■ A delta ■ Polymodal nociceptors ■ Pathway ■ Spinothalamic tract ■ Brain areas responsible for pain perception ■ Primary somatosensory cortex ■ Anterior cingulate cortex ■ Prefrontal cortex ■ Tempero-parietal cortex ■ Periaqueductal grey
  17. 17. Spinothalamic Tract
  18. 18. The general response to patients with chronic pain…
  19. 19. Analgesia ■ Not just relief of subjective pain ■ Can be debilitating ■ A host of other physiological factors are influenced by presence of pain ■ Sympathetic nervous system ■ Hypothalamic-pituitary axis ■ Importance of adequate pain relief
  20. 20. Consequences of Inadequate Analgesia ■ Impairment of immune function ■ Increased ability of blood to clot ■ Exacerbate injury ■ Prevent wound healing ■ Increase susceptibility to infection ■ Prolong hospitalization
  21. 21. Consequences of Inadequate Analgesia ■ Fight or flight ■ Release of stress hormones ■ Epinephrine ■ Norepinephrine ■ Glucagon ■ Cortisol ■ Aldosterone ■ Thyroid stimulating hormone ■ Growth hormone ■ Promote breakdown of body tissues and water retention ■ Increase blood glucose ■ Increase body’s metabolic rate ■ Increase heart rate, blood pressure, cardiac output, and inotropic state of heart ■ Impair normal gastrointestinal functioning
  22. 22. Importance of Subjective Ratings of Pain ■ Pain is defined by the person experiencing it ■ Most common means of assessing pain is by subjective report of the person/participant ■ Most common means of assessing pain rely on subjective ratings ■ These ratings are the primary tool for determining if pain management is effective
  23. 23. Pain Measurement ■ If the answers to the question “What is pain?” are so varied, how can one measure pain? ■ A person can easily report whether or not a stimulus is painful ■ But how can they report the degree of pain they are experiencing?
  24. 24. Pain Measurement ■ How can one define and assess the validity of a pain measure? ■ Is pain a unidimensional or a multidimensional construct? ■ Can one find a truly objective measure of a subjective sensation?
  25. 25. The Meaning of Pain ■ Melzack (1973) The Puzzle of Pain ■ Number of pain qualities ■ Ranges from a single quality ■ purely emotional ■ purely sensory) ■ To as many as 5 qualities ■ affective ■ motivational ■ cognitive aspects ■ behavior
  26. 26. Components of Pain ■ Melzack and Casey (1968) ■ Suggested 3 dimensions ■ Sensory-discriminative ■ Motivational-affective ■ Cognitive-evaluative
  27. 27. Multiple Dimensions of the Pain Experience ■ Multidimensional scaling studies demonstrate anywhere from 2-5 factors ■ Two of the factors are ■ Pain Intensity ■ Pain Unpleasantness ■ Experience of pain may be a gestalt ■ more than the sum of its parts ■ To adequately assess pain, one needs to assess as many of these parts as possible
  28. 28. Multidimensional Models of Pain ■ Multiple Components of the Pain Experience ■ Sensory/Physiological ■ Cognitive ■ Behavioral ■ Affective/Emotional ■ Motivational
  29. 29. Complexities of Pain ■ Pain as a perceptual construct ■ Extremely difficult to define ■ Extremely difficult to assess ■ Very common as a clinical symptom ■ However, very difficult to describe to someone else ■ Think of a pain experience that you have had ■ Try to describe it to your neighbor ■ Unless she has had a similar experience, this can be very difficult
  30. 30. Sensation, Perception, Comprehension ■ Every experience you have with something in your environment has at least three components, if it reaches conscious awareness ■ Sensation – the recognition by your nervous system of an outside event ■ Perception – your awareness of that event ■ Comprehension – your understanding of the meaning of the event
  31. 31. The Unique Nature of Pain ■ Can you have a perception of pain without noxious inputs (sensation)? ■ Can you have sensation of pain without perception? ■ Can you have perception of pain without comprehension?
  32. 32. Examples ■ Have you ever given a child a shot? ■ Do they yell when you clean the site with alcohol? ■ The child expects (comprehension) pain with a shot ■ Therefore, can feel pain when you touch her! ■ Have you ever been hiking and come home with a cut or a bruise that you don’t remember getting? ■ Where there noxious inputs? ■ Why weren’t you aware of them?
  33. 33. The Nature of the Body’s Reaction to Pain ■ Our perceptual systems are designed to understand the events that happen to us ■ To assign them meaning ■ This means that sensation, perception, and comprehension may not occur in sequential order!
  34. 34. A Child’s Story ■ When I was young, my brother and I used to enjoy stomping in mud puddles. One weekend, after a brisk rain, we trudged outside and took on mud hole after mud hole, trying to splash one another as impressively as possible. After a particularly good splash, my brother looked down at my feet, his mouth open, and pointed. I looked down to see a streak of red in the puddle. I pulled my foot up to see a large piece of glass lodged in my Snoopie galoshes – and my foot. I started to scream. My father came out, and began trying to remove the galoshes, to get a look at the injury.. I writhed and yelled, protesting my agony. My father finally sat me up with a start, and exclaimed, “I will bet you didn’t start crying until you saw it.” I stopped crying, and realized he was right. So I sat still as he removed the 4 inch piece of glass.
  35. 35. Why is this important to health professionals? ■ Understanding that a patient may have pain even when we don’t see anything wrong ■ Also understanding that what a patient knows may impact the amount of pain she feels ■ Finally, recognizing that we can never really know how much a patient is hurting ■ We have to ask, and ask often!
  36. 36. Pain Measurement Scales ■ Numerical Rating Scales ■ Visual Analogue Scales ■ Verbal Rating Scales ■ Magnitude Matching ■ Behavioral Measures ■ Physiological Measures
  37. 37. Multidimensional Models of Pain ■ Multiple Components of the Pain Experience ■ Sensory/Physiological ■ Cognitive ■ Behavioral ■ Affective/Emotional ■ Motivational
  38. 38. Complexities of Pain ■ Pain as a perceptual construct ■ Extremely difficult to define ■ Extremely difficult to assess ■ Very common as a clinical symptom ■ Specific issues related to pain in the clinical environment ■ What aspects of pain are important to assess? ■ Why?
  39. 39. Prevalence of Undertreated Pain ■ Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatment ■ 50% of patients reported unrelieved pain ■ 15% reported extremely severe pain ■ Cancer Pain ■ Study of 54 cancer treatment centers ■ 67% of outpatients reported pain in the previous week ■ 42% were not given adequate analgesia ■ Inadequate treatment of pain at end of life
  40. 40. Barriers to Optimal Pain Control ■ Lack of knowledge ■ Very few medical schools have courses on pain ■ Oncologists ■ 75% rated pain management training as fair to poor ■ Many schools have only 1-2 lectures, despite prevalence of pain as syndrome as well as symptom ■ This is improving, but slowly ■ Inadequate pain assessment ■ MAJOR predictor of inadequate pain control ■ Difficulties of measuring pain ■ Pain as subjective ■ Sometimes, can only measure pain relatively, within a given patient ■ Measuring CHANGE in pain ratings
  41. 41. Faking Pain ■ Worker’s Compensation ■ Issues of Secondary Gain ■ Issues that may lead an individual to report pain, to achieve a secondary benefit ■ Can be very difficult to determine if an individual is malingering pain
  42. 42. Malingering ■ A constant challenge to all aspects of health professional interactions with pain patients ■ Describe the “classic” patient who is “faking pain” ■ How can you tell ■ The classic stereotype of a malingering patient can often look strikingly similar to a chronic pain patient receiving inadequate treatment ■ Depression ■ Hysterical ■ “Doctor shopping”
  43. 43. Detection of Bias in the Pain Responder ■ Minnesota Multiphasic Personality Inventory II (Greene, R. L. (1991) ■ Gracely (1983) suggests the use of several of the MMPI scales to detect biases in responding in pain assessment ■ F-scale: “Faking” scale ■ L-scale: “Lying” scale ■ K-scale: “Defensiveness” scale
  44. 44. Problems with the Use of these Tools to Measure Bias ■ Many problems with the accuracy of these scales ■ Biases in responding to the MMPI-II may not indicate biases in response to pain measurement ■ “The only time my children tell the truth is when they are in pain.” Bill Cosby ■ Need specific tools for measuring these features in pain report ■ Again, return to problem of how to determine accuracy
  45. 45. Where does this leave us? ■ If we accept that we have a duty to assess and attempt to treat pain, where does this leave our responsibility? ■ What about patients who are malingering or faking pain? ■ How do we determine if patients are genuinely in pain?
  46. 46. Responsibility ■ The answer, as difficult as this may seem, is that we simply have to take the patient at her word ■ We must believe that a patient is in pain who reports pain, until proven otherwise ■ When reasonable doubts are present regarding validity of pain report, physicians may take into account other causes ■ But remember - the only valid pain report comes from the patient herself

Notas do Editor

  • these many components of pain perception interact with one another

    parallel processing, rather than serial processing

    the size of a motor reflex can significantly affect an emotional response to painful stimuli, and a powerful autonomic response can influence one’s ability to discriminate exactly what is causing the painful stimulation, and location of that painful stimulation