Understanding Pain

1. Understanding Pain Grant Huston Physiotherapist GF Strong Rehab Centre

2. Acknowledgments • David Butler “The Sensitive Nervous System” (2000) • Lorimer Moseley and David Butler “Explain Pain” (2003) • Marshall Devor (contributor to) “The Textbook of Pain” (1999 – 4th ed.)

3. Why Talk About Pain? • Prevalent in SCI: 94% incidence, up to 45% describe as severe pain. • Important to SCI: Many would like their pain decreased before walking or bowel and bladder recovery.

4. Why Talk About Pain? • Persistent pain is a major cause of disturbed daily activities, sleep and depression • “At any one time on the face of the earth around 25% of people have pain which has persisted for more than three months”

5. What Is Pain? • “An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described by the patient in terms of such damage” (World Health Organization definition)

6. What Is Pain? • “Pain is a multi-system output that motivates and assists the individual to get out of a system that the brain perceives threatens body tissue” - LM

7. …in other words • If (1) danger or perceived danger to body tissue exists • And (2) action is required • then the brain produces pain.

8. Pain is Normal • Pain protects you. • Pain alerts you to danger often before you are injured or injured badly. • Pain makes you… MoveThink and Behave differently making it vital for healing.

9. Pain Is Normal • It is usually sensible to hurt.

10. The Brain Decides… • Ultimately the brain has the final say. If it thinks you are in danger, you will feel pain. • It may not always be correct, but the brain has the final say. “NO BRAIN, NO PAIN!”

11. Pain Factoids • The amount of pain you experience is not related to the amount of tissue damage you have sustained. (this goes both ways: war stories vs. paper cuts) • If there is no pain: it means that changes in the tissues are not perceived as a threat by the brain. (aging, shark bites, sporting)

12. The Effect of Context on Pain • Many cues and experiences relate to the pain experience. The brain decides whether something hurts or not 100% of the time: No Exceptions. • We are emotional creatures that can calculate, surmise and predict the future. (Memories and reasoning help avoid danger before it happens).

13. The Virtual Body in our Brain

14. How it all works:The Danger Alarm System • Think of your body as a house. • The command centre for the alarm system (brain, spinal cord) for your house is kept in a well cushioned vault. • Wired with nerves which are triggered by alarm sensors which have the ability to increase or decrease the bias depending on the brains perceived needs for survival.

15. Receptors (sensors) • Specific: mechanical, chemical, and temperature. • Sensitive: short lived, made by the nerve specifically in terms of type and rate of replacement. • Location: nerve endings, axon hillock, cell body, and any de-myelinated areas. (not evenly distributed).

16. A Receptor…

17. So… are there pain sensors? No….but… • There are some neurons that send prioritized danger signals. • …signals are sent but it still doesn’t mean pain. It means danger. • Sensors sensing danger are one way to activate the alarm…there are other ways (eg. thoughts).

18. About Nerves… They are: • Electrically Excitable • Require a certain amount of excitement before a message is sent

19. More About Nerves…. • Large and fast or small and slow, they still only say “danger.” • Depending on what they connect with they will inhibit or excite. • The danger signal travels to the spinal cord where it releases a chemical sensitizing messenger into the synapse.

20. Neuron: “hello Spinal Cord, pleased to meet you” • Excitatory chemicals are released into the synapse (gap) to a neighboring neuron. • Specific chemicals unlock specific receptors. (kind of like a key in a lock). • The nerve to the brain needs to reach a certain level of stimulation before a signal is sent.

21. The Spinal Cord Junction (“Synapse”)

22. What does the Brain do with this information? • Yes yes…we know!!…it interprets the array of danger messages and then decides whether this danger equals pain. • Pain borrows parts of the brain (movement, sensation, emotion and memory) to express itself. • Neurotag is a particular pattern of activity in the brain which creates the perception of pain.

23. Recap: Nociception(= danger reception) • Alarm Bells. • Get out of harms way (several systems get activated. • Very Fast and Useful. REMEMBER…The activity of the alarm system (nociception) is neither sufficient nor necessary to cause pain.

24. Okay, I wasn’t Fast enough! • The body rests and tissues heal… predictably. • Inflammation: Swelling Heat Redness. • Scar is formed and remodeled to make a best match.

25. Acid or Inflammation? • Move and cure thyself (ACID). Lack of movement (like sitting for hours at a computer) leads to build-up of cell waste products including acid…sets off the acid danger sensors…so move it! • What’s in the soup? (INFLAMMATION). The “inflammatory soup” after an injury activates alarm bells and this increased sensitivity is designed to protect the injured tissue. The brain gets immediately interested in inflammation.

26. All Tissues Heal • Some are better than others. • The speed of healing depends on the blood supply and the demands that are placed on the tissue. • Skin and muscle heal quickly; ligament and disc do not.

27. Nerves can cause pain too • Remember they are tough and slippery! • The neurons in a nerve can be a real source of danger messages and a contributor to pain.

28. Nerves… • Nerves can generate danger signals when damaged (common spot is nerve root) • Nerves can cause inflammation (backfiring)

29. Recap: Inflammatory Pain • Temporary. • Pain seen after a new injury. • Has a well established survival mechanism. • Redness, Heat, Swelling.

30. An Important Picture!

31. Recap • Most pain involves some tissue issue. Inflammation. Slow healing. Disused/unused/unfit tissues. Anticipation of tissue harm. • The initial injury has healed. why does my pain persist? A KEY QUESTION!!!!!

32. The key is how the alarm signals are processed • Back to the spinal cord. • when danger impulses keep coming, the system will adapt to meet the demand.

33. Here, the volume of the response is being turned down. It may take several “volleys” from the tissues to send a danger signal. Brain is meddling. There are other inputs too!

34. Another example… • Here, the volume of the response is being turned up. • It doesn’t take as much peripheral stimulation to send a danger signal to the brain. • Brain is meddling.

35. So the Spinal Cord can act as a magnifier of tissue reality • Enhanced Sensitivity of the alarm system is nearly always a main feature in persistent pain (think about all the symptoms too). • The brain is being told that there is more danger at the tissues than there actually is.

36. Adaptations in the Brain • Again the changes are aimed at trying to protect you: More sensors More pain ignition nodes More chemicals. • Easier to ignite. • Eg: a memory cue may serve to protect you in terms of a shudder or even a pain neurotag.

37. Brain Adaptation cont.. • Over the long term see: Smudging (remember the virtual body)… • Motor areas = makes it difficult to use to part in question • Sensory areas = makes surrounding areas sensitive too

38. Other nerve inputs • Remember the Neurotag. • Thoughts are nerve impulses too. Sometimes they serve to increase sensitivity in the brain. • “Thought Viruses.” eg “I’m not doing anything until all the pain is gone.” “I’m in pain, so there must be something harmful happening to my body.”

39. The Interacting Components of Sensitivity

40. Focus on Output…How do we respond to pain? Systems at work… • Sympathetic and parasympathetic. Chronic pain and stress are associated with increased Adrenaline (sympathetic). Adrenaline is useful in small doses, but for long periods of time, it too can magnify the pain response. The parasympathetic system is active during rest and replenishment…chronic pain is very associated with sleeplessness.

41. Response systems cont… 2. Endocrine system and cortisol. Our hormone system releases cortisol in response to pain…it slows down body processes which are not needed for immediate protection, and enhances those which are.

42. Responses to Pain cont… 3. The Immune System. Also looks after you. Immune Molecules - Cytokines are involved. When pain gets bad it’s kind of like the permanent flu.

43. Responses to Pain cont… • It’s not all bad with the immune system though: • Exercising appropriately, having a sense of humor, having strong beliefs, having family and medical support, to be in control of your life and medical treatment, to influence your own quality of life: These things keep the immune system on your side.

44. Responses to Pain cont… • Movement/Muscles When you are in pain, the brain primes the muscles to be ready… But when muscles stay active and tense for a long time, they tend to contract and shorten STIFFNESS, ACHINESS, ACID BUILDUP

45. Persistent Pain:To Sum it up • As pain becomes more persistent, response systems become more involved • Thoughts become a contributor to pain • The brain produces a neurotag by adaptation • Tissues contribute less and less to the pain experience

46. But you haven’t been talking about spinal cord injury! • Pain in SCI usually (often) appears to act oddly. • It is important to realize that the body will use the systems it has working to convey messages about pain. eg. Autonomic dysreflexia.

47. SPECIAL TYPES OF PAIN SEEN IN SCI: 1. Dysesthetic/Central Pain • Syrinx Pain

48. Types of SCI Pain... 1. Central/Dysesthetic Pain. • often the most troublesome symptom in SCI. • can feel pain where you are not supposed to feel anything or where your feeling is different. • Pain is throughout the generalized area below your level of injury and is often constant. • often begins weeks or months after your injury, and can cause. • pins and needles, or numbness. • aching or burning (most common).

49. Types of SCI Pain... 2. Syrinx Pain. • develops months to years after injury. • can occur above or below the site of your injury. • Can result in a gradual loss of organ function, feeling, movement. Be aware of changes in sensation, strength, and pain patterns.

50. Managing Your Pain… • Many people will want to help. • You will be better informed and in control if you understand the science behind your pain.