SM 250: Acute vs Chronic Pain

Question 1

What is pain?

Answer 1

Pain is an unpleasant sensory or emotional experience associated with actual or potential tissue damage

Question 2

What two factors classify pain?

Answer 2

Duration: acute vs chronic

Mechanism: nociceptive vs neuropathic

Question 3

What types of pain stimuli can be detected by primary afferent neurons, and what fibers connect them to a dorsal root ganglion?

Answer 3

Non-noxious mechanical stimulus = Abeta fiber

Noxious mechanical stimulus = Adelta fiber

Noxious heat and chemical stimuli = C fiber

Question 4

What structures are broadly involved in the Ascending pain pathway?

Answer 4

Spinothalmic Tract to Thalamus to Somatosensory Cortex and other areas of the brain

Question 5

What role does the Thalamus play in the Ascending pain pathway?

Answer 5

The Thalamus is a relay station for pain signals

Question 6

What is the function of the descending inhibitory pathway?

Answer 6

Downregulates pain signals being detected in the Ascending pain pathway from the periphery

Question 7

How does the Descending Inhibitory Pathway modulate pain?

Answer 7

Inhibitory signals from the brain and spinal cord are relayed to the Dorsal Horn of the Spinal cord to limit incoming pain signals

Question 8

How does the Descending Inhibitory Pathway mediate pain tolerance and how does it relate to chronic pain?

Answer 8

In the short term, the Descending Pathway can allow a person to withstand severe pain for a short period of time

In chronic pain, these inhibitory signals are often lost, leading to constant pain perception

Question 9

What is plasticity?

Answer 9

Plasticity refers to the nervous system’s ability to reorganize itself and adjust it’s function/activity in response to changes in the environment

Question 10

Is plasticity adaptive or maladaptive in chronic pain and why?

Answer 10

Plasticity is maladaptive in chronic pain because it leads to hypersenitization of the nervous system and perpetuates chronic pain

Question 11

Does sensitization occur centrally or peripherally in the nervous system?

Answer 11

Both

Question 12

What can cause peripheral sensitizaton?

Answer 12

Changes in signalling due to:

Distal nerve endings
Axons
Cell bodies/DRG

Question 13

How does Peripheral sensitization lead to chronic pain?

Answer 13

Reduced threshold of nociceptors as a result of peripheral sensitization leads to chronic pain

Question 14

Does peripheral sensitization occur acutely or chronically?

Answer 14

Either or

Question 15

What can peripheral sensitization result in?

Answer 15

Allodynia or Hyperalgesia

Question 16

What is Allodynia?

Answer 16

A form of peripheral sensitization where pain occurs in response to a non-painful stimuli

Question 17

What is Hyperalgesia?

Answer 17

A form of peripheral stimulus where a mildly painful stimuli is perceived as much more painful

Question 18

If a physical exam reveals pain to light touch, what form of sensitization has occured?

Answer 18

Allodynia, since light touch is normally not painful

Question 19

If a physical exam reveals severe pain to pin-prick testing, what form of sensitization has occured?

Answer 19

Hyperalgesia, since pin-prick is normally only slightly painful

Question 20

What causes sensitization at a mechanistic level?

Answer 20

Substances released by damaged tissues which augment the response of nociceptive fibers, such as Prostaglandins, leading to Hyperalgesia

Question 21

What is central sensitization?

Answer 21

A persistent state of high reactivity that lowers the threshold for what causes pain and maintains pain even after the initial injury has healed

Question 22

Does pain caused by central sensitization persist after the initial wound is healed?

Answer 22

Yes - leads to chronic pain

Question 23

What causes central sensitization at a physical level?

Answer 23

Rewiring of nerve connections centrally + loss of descending inhibition of sensory input

Question 24

Why does a loss of descending inhibitory function lead to central sensiziation?

Answer 24

Subthreshold stimuli become sufficient to generate AP’s in the Dorsal Horn neurons without inhibition, leading to sensitivity

Question 25

Does central sensitization lead to Allodynia or Hyperalgeisa?

Answer 25

Both

Question 26

How does central sensitization present?

Answer 26

Heightened sensitivities across all senses Cognitive defects Increased anxiety Sick Role Behaviors

Question 27

What factors predipose central sensitization?

Answer 27

A lot of things: ``` Biological Psychological Environmental Depression/Anxiety Stressors ```

Question 28

What is the evolutionary role of pain?

Answer 28

Pain is a warning of potential or actual tissue damage and acts to protect the body

Question 29

What is the ideal pain threshold?

Answer 29

One that allows the body to prevent or minimize tissue damage without interfering with daily activities

Question 30

How can an injury and it's associated acute pain heal?

Answer 30

Normal healing will lead to pain relief Healing with plasticity leads to Hyperalgesia and/or Allodynia, causing chronic pain

Question 31

What is acute pain?

Answer 31

Pain from an injury or trauma that acts as a signal demanding healing

Question 32

How long does acute pain last?

Answer 32

For an expected duration of time, until the tissue has recovered from the injury

Question 33

How long does chronic pain last?

Answer 33

Longer than the time of healing for the initial injury

Question 34

How does chronic pain manifest behavioral changes in patients?

Answer 34

Guarding of the injured area, fear of movement/re-injury, generalization of pain, adoption of the sick role

Question 35

What drives chronic pain?

Answer 35

Structural changes in the nervous system = plasticity

Question 36

What symptoms does chronic pain involve?

Answer 36

Unremitting and spontaneous shooting or burning sensations as well as abnormal sensitivity to normally noxious stimuli on exam

Question 37

Why is chronic pain maladaptive?

Answer 37

Pain signals no longer serve to protect a person but become the focus of impairment and limitation for a person

Question 38

What are the two types of psychological factors in pain?

Answer 38

Affective and Cognitive factors

Question 39

What are the Affective factors in pain?

Answer 39

Depression, Anxiety, Anger

Question 40

What are the Cognitive factors in pain?

Answer 40

Catastrophizing, fear, helplessness, and decreased self-efficacy

Question 41

How does sleep play into pain?

Answer 41

Vicious cycle: Pain leads to anxiety and impairs sleep, which decreases our ability to cope with pain

Question 42

How should acute pain be managed?

Answer 42

Rest, pharmacologic and non-pharmacologic interventions, and surgery = biomedical approach

Question 43

How should chronic pain be managed?

Answer 43

Address both physical and emotional components of a chronic disease state with an emphasis on coping and improving symptoms (may not resolve pain entirely) = biopsychosocial approach

Question 44

What is the biomedical treatment model view of pain?

Answer 44

Pain as a sensory event with an underlying disease or tissue damage involved

Question 45

What would be involved in interdisciplinary treatment of pain?

Answer 45

Psychologist, physical therapists, physicians

Question 46

What are the goals of an interdisciplinary pain program?

Answer 46

Increase physical activity, decrease pain intensity, improve psychosocial functioning

Question 47

What is pain psychology?

Answer 47

A branch of psychology that focuses on the mind-body connection, coping skills training, and mindfulness

Question 48

How does physical therapy contribute to pain management?

Answer 48

Improve range of motion, aerobic conditioning, home exercise plan, etc

Question 49

How does occupational therapy contribute to pain management?

Answer 49

Positioning/posture improvement, body mechanics, work tolerance