Symptoms 26: Chronic Pain

Front 1

What are the types of pain?

Back 1

- Nociceptive (inflammatory)
- Neuropathic

Front 2

What is nociceptive pain? How is it mediated?

Back 2

Soft tissue damage
- Inflammation of skin, muscle, soft tissue
- Activates pain receptors (nociceptors)
- Inflammation due to release of chemicals (eg, prostaglandins) - activate and sensitize the free nerve endings attached to C fibers (unmyelinated)

Front 3

What are the types of fibers attached to nociceptors?

Back 3

- C fibers: not myelinated
- Aδ fibers

Front 4

What are the types of mild nociceptive pain?

Back 4

- Infection
- Rash

Front 5

What are the types of severe nociceptive pain?

Back 5

- Rheumatoid arthritis
- Gout
- Tumor in soft tissue

Front 6

How do you treat nociceptive pain?

Back 6

- NSAIDs: reduce inflammatory pain
- Opioids

Front 7

What is nociceptive pain? How is it mediated?

Back 7

Direct damage to nerves in PNS or CNS (eg, cut, compression, loss of blood supply and O2 to nerves)

Front 8

What is allodynia?

Back 8

Pain from stimulus that is not normally painful

Front 9

What is hyperalgesia?

Back 9

When a painful stimulus is extra painful

Front 10

What is the quality of neuropathic pain?

Back 10

- Burning, electrical quality
- May cause allodynia (pain to touch that is normally not painful)

Front 11

What are some examples of neuropathic pain?

Back 11

- Post-herpetic neuralgia after shingles infection
- Diabetic neuropathy
- Severe nerve entrapment

Front 12

What type of pain are NSAIDs and opioids good for? What type of pain is resistant to these drugs?

Back 12

- Good for nociceptive / inflammatory pain
- Neuropathic pain is resistant to NSAIDs or opioids; better to use Gabapentin

Front 13

Which of the following is not a typical characteristic of neuropathic pain?
a) Pain felt in response to light brush of the hand.
b) Typically treated effectively by morphine
c) Resistant to NSAIDS.
d) Due to trauma or disease of nerve fibers.
e) Pain has burning, shooting or “electrical” quality.

Back 13

Typically treated effectively by morphine

Front 14

What pathway transmits pain and temperature sensation to the cortex?

Back 14

Anterolateral System (ascending tracts of fibers): Aδ and C fiber nociceptors in skin, muscle, joints, and bones

Front 15

What can activate action potentials in free nerve endings that connect to the anterolateral system?

Back 15

- Noxious mechanical stimuli
- Thermal stimuli
- Chemical stimuli

Front 16

What types of fibers are in the anterolateral system? Characteristics?

Back 16

- Aδ fibers: mediate first pain - fast, sharp, pricking, short-lasting, protective
- C fibers: mediate second pain - delayed, burning quality, long-lasting, chronic

Also convey information about non-painful cooling and warming (temperature stimuli)

Front 17

Where do nociceptor fibers from the periphery go to tell the brain they've detected pain or temperature stimuli?

Back 17

- Central processes of nociceptors enter LATERAL dorsal horn via the Dorsal Lateral Tract of Lissauer
- Synapses on spinal cord neurons in superficial dorsal horn (on lamina I/II or V)

Front 18

Where do nociceptor fibers synapse?

Back 18

Spinal cord neurons in superficial dorsal horn (lamina I/II or V)

Front 19

What do nociceptors release at their synapse? Effect?

Back 19

Glutamate and Substance P → activates receptors on spinal neurons

Front 20

Where do the second order neurons that originate in the dorsal horn go? Function?

Back 20

- 2nd order neurons terminate in thalamus (dorsal column - medial lemniscus)
- Mediates discriminative aspects of pain and temperature sensation (location, intensity, duration of noxious stimulus)

Front 21

Where specifically do the second order pain neurons in the spinothalamic tract synapse?

Back 21

Two nuclei:
- Ventral Posterior Lateral (VPL) nucleus
- Central Lateral Nucleus

Front 22

Where do the third order neurons that originate in the Ventral Posterior Lateral (VPL) nucleus of the thalamus go? Function?

Back 22

3rd order nucleus projects through internal capsule and corona radiata, to SI cortex (areas 3b, 1, 2)

Front 23

What is the primary relay nucleus for discriminative pain info from body? Function?

Back 23

Ventral Posterior Lateral (VPL) nucleus of thalamus
- Localizes where noxious stimulus on body occurred, how intense, qualities
- Somatotopically organized

Front 24

What is the organization of the Ventral Posterior Lateral (VPL) nucleus in the thalamus?

Back 24

Somatotopically organized:
- Legs are lateral
- Arms are medial

Front 25

Where do the third order neurons that originate in the Central Lateral (CL) nucleus of the thalamus go? Function?

Back 25

- 3rd order neurons from CL project to many areas of cortex, limbic cortex (cingulate gyrus, hippocampus, amygdala)
- Involved in emotional suffering during chronic pain and memory of painful events

Front 26

What is the organization of the Central Lateral (CL) nucleus in the thalamus?

Back 26

Not somatotopically organized

Front 27

What are the functions of the thalamus in pain (spinothalamic tract)?

Back 27

- Process nociceptive pain: begin crude pain and temperature sensation, begin emotional suffering reactions
- Relay information to SI cortex: 3rd order neurons pass through posterior limb of internal capsule, corona radiata, to SI cortex

Front 28

Which of the following are NOT properties of the spinothalamic tract?
a) It discriminates sharp pain of a paper cut from burning pain of a hot iron.
b) Its axons may project to the Central Lateral Nucleus in the thalamus.
c) The spinothalamic tract in the right rostral medulla carries noxious information from the left side of the body.
d) It activates areas of the cortex concerned with the fear and anxiety associated with chronic pain.
e) Its axons may project to the Ventral Posterior Lateral Nucleus in the thalamus.

Back 28

It activates areas of the cortex concerned with the fear and anxiety associated with chronic pain

Front 29

What are the other pain pathways besides the spinothalamic tract?

Back 29

- Spinoreticular tract
- Spinomesencephalic tract

Front 30

What is the path of the spinoreticular tract? Function?

Back 30

- Many 2nd order axons terminate in reticular formation in medulla or pons
- Processing mediates changes in level of attention to painful stimuli
- Involved in emotional, arousal, attention, affective response to noxious stimulus

Front 31

What is the path of the spinomesencephalic tract? Function?

Back 31

- Some 2nd order axons terminate in the midbrain in the superior colliculus and periaqueductal gray (PAG)
- Other neurons in PAG send axons back down spinal cord → descending control neurons, pathways
- Stimulates descending control pathways that project down to spinal cord and INHIBIT PAIN signals coming up

Front 32

What pathway mediates the level of attention to painful stimuli?

Back 32

Spinoreticular tract (via reticular formation in medulla and pons)

Front 33

Which pathway inhibits pain signals coming up?

Back 33

Spinomesencephalic tract:
- Neurons in periaqueductal gray (PAG) sends axons down to spinal cord to inhibit pain signals coming up

Front 34

Besides pain and temperature sensation, what else do the anterolateral tracts carry information about?

Back 34

Some crude touch sensation (a few 2nd order fibers receive fine touch info too)

Front 35

What tract mediates this thought: "Something sharp is puncturing my right heel"?

Back 35

Spinothalamic Tract (discrimination)

Front 36

What tract mediates this thought: "Ouch! That hurts!"?

Back 36

Spinoreticular Tract (attention, arousal, affect)

Front 37

What tract mediates this thought: "Ahh, that feels better"?

Back 37

Spinomesencephalic Tract (endogenous pain relief)

Front 38

Where do thalamic neurons project to?

Back 38

- Somatosensory cortex
- Cingulate gyrus
- Insular cortex

Front 39

Where do thalamic neurons from the Ventral Posterior Lateral (VPL) nucleus project to? Function?

Back 39

- Somatosensory Cortex SI areas 3b, 1, and 2
- Subsequently goes to SII cortex

- Helps localize painful stimulus

Front 40

Where do thalamic neurons from the Central Lateral (CL) nucleus project to? Function?

Back 40

Projects to cingulate gyrus (part of limbic system)
- Processes emotional component of pain: fear, anxiety, depression, anger, and attention

Front 41

What is the function of thalamic neurons that project to the insular cortex?

Back 41

- Processes info on internal, autonomic state of body (heart races, breathing rapid, mouth dry, muscles tense, can't sleep)
- Also integrates discriminative, affective, emotional, cognitive components of pain

Front 42

What happens to your perception of pain if the insular cortex is lesioned?

Back 42

"Asymbolia for pain" - patients perceive stimulus as noxious but don't care, emotional response is inappropriate

Front 43

A lesion to what area would cause patients to perceive a stimulus as noxious, but don't care (inappropriate emotional response)?

Back 43

Insular Cortex

Front 44

How can you inhibit pain centrally?

Back 44

Neurons with cell bodies in Periaqueductal Gray (PAG)
1. Send axons to Raphe nuclei (medulla), others send axons to locus ceruleus (pons)
2. These neurons send axons to spinal cord - synapse on inhibitory interneurons or spinothalamic tract neurons (inhibit)
3. Suppresses transmission of ascending noxious info to thalamus and cortex

Front 45

Where do neurons from the periaqueductal gray (PAG) synapse to inhibit pain?

Back 45

- Raphe nucleus (medulla)
- Locus ceruleus (pons)

Front 46

Where do neurons in the raphe nucleus (medulla) and locus ceruleus (pons) go to inhibit pain? Effect?

Back 46

These neurons send axons to spinal cord
- Synapse on inhibitory interneurons or spinothalamic tract neurons (inhibit)
- Suppresses transmission of ascending noxious info to thalamus and cortex

Front 47

What do Aδ fibers mediate?

Back 47

Sharp localized pain to dorsal horn of spinal cord - terminates in lamina I

Front 48

What do C fibers mediate?

Back 48

Dull, diffuse, aching, or burning pain - terminates in lamina II

Front 49

What NTs do Aδ fibers use? Where do they synapse?

Back 49

Use glutamate as NT, act on lamina I

Front 50

What NTs do C fibers use? Where do they synapse?

Back 50

Use glutamate and substance P as NTs, act on lamina II

Front 51

Which of the following is the most common cause of low back pain (LBP)?
a) Metastatic bone disease
b) Inflammatory back pain
c) Lumbosacral sprain or strain
d) Posterior facet strain
e) Ankylosing spondylitis

Back 51

Lumbosacral sprain or strain

(Inflammatory back pain and ankylosing spondylitis are referring to the same thing)

Front 52

Which of the following is a “red flag” or danger sign in the diagnosis of low back pain (LBP)?
a) Impotence
b) Imbalance
c) Pain aggravated by standing
d) Limited spinal motion
e) Sleep disturbance

Back 52

Impotence - caused by neurologic injury

Front 53

What are the red flags for "back pain"?

Back 53

- Bowel or bladder dysfunction
- Impotence
- Fever/chills; weight loss
- Lymphadenopathy
- New onset in children/adolescents or age >50
- Saddle anesthesia
- Motor deficits at multiple levels

Front 54

What is pain?

Back 54

Unpleasant sensory and emotional experience associated with actual or potential tissue damage

Front 55

How can painful stimuli be experienced differently?

Back 55

- Different genetic background: different receptor densities, nociceptor thresholds, density of innervation, pain pathway projections, descending control, CNS modulation
- Different past experiences, cultures, mental status, anxiety, fear

Front 56

As a trained physician, after thorough physical and neurological examination if you cannot identify the source of a patient’s pain, you can conclude that the pain is psychosomatic and recommend cognitive or psychological therapy.
a) TRUE
b) FALSE

Back 56

False

Front 57

What are the challenges in diagnosing pain?

Back 57

- Perceived differently by different people
- Strongly influenced by psychological and social factors
- May exist with mental illness and addiction
- Particularly in the case of lower back pain: "an illness in search of a disease" - difficult to identify if muscular, ligamentous/tendinous, facet joint, or discogenic in origin

Front 58

Which neurotransmitters are involved in pain transmission in the dorsal horn of the spinal cord?
a) GABA and Glutamate
b) GABA and Substance P
c) Glutamate and Substance P
d) Glutamate and Acetylcholine
e) I don’t know

Back 58

Glutamate and Substance P

Front 59

How can you image low back pain? Utility?

Back 59

- Plain X-rays - frequently ordered but have a very low yield of findings, often doesn't change management, poor relationship between radiographic abnormalities and signs/symptoms of lower back pain

Front 60

When is a plain x-ray for low back pain indicated?

Back 60

- Rules out infectious or malignant process
- Assessing patient with objective neuro abnormalities
- Identify compression fracture

Front 61

An MRI reliably identifies the source of pain in patients with degenerative disc disease.
a) TRUE
b) FALSE

Back 61

False

Front 62

When would you do an MRI for low back pain?

Back 62

If you think the MRI will influence management; patient should be willing to undergo surgery before test is performed

Front 63

What are the advantages of MRI?

Back 63

- Diagnosing disc disease, spinal stenosis, infection, neoplasm
- Evaluation in case of intractable pain or neuro deficits

Front 64

What are the disadvantages of MRI?

Back 64

- Presence of abnormal findings does NOT correlate well with clinical symptoms
- Eg, you may see a herniated disc in up to 25% of asymptomatic people

Front 65

How do you treat acute lower back pain?

Back 65

- 80-90% will recover after 6 weeks, no matter what treatment is prescribed
- Only 1% eventually require surgery
- Patient education is crucial
** Cornerstone of treatment = physical exercise

Front 66

Which of the following would be best in the short and long-term treatment of back pain?
a) Regular physical activity
b) Back supports
c) Work site modification
d) Back education school

Back 66

Regular physical activity

Front 67

How common are patients going to progress to chronic lower back pain (>3 months)?

Back 67

10%

Front 68

What are the goals of opioids for chronic non-malignant pain?

Back 68

- Improve pain control ("pain free" isn't realistic)
- Improve function
- Provide relief of associated symptoms (ie, anxiety or sleep problems)

Front 69

What do you need to do to assess a patient you may give opioids for chronic non-malignant pain?

Back 69

1. Pain assessment
2. Screen for substance use disorder (eg, "AUDIT", "DAST-10")
3. Screen for psychological co-morbidity (eg, "PHQ-9")

Front 70

What are some non-opioid adjuvant medications that can be used for low back pain?

Back 70

- Tricyclic anti-depressants (eg, amitriptyline)
- SSRI (eg, citalopram)
- SNRI (eg, duloxetine)

Front 71

Why do anti-depressants work for pain management?

Back 71

Release of serotonin, NE to inhibit the ascending pain pathway

Front 72

What opioids are used for low back pain?

Back 72

- Morphine (controlled-release) = Contin
- Morphine (extended-release) = Avinza
- Oxycodone (controled-release) = Oxycontin

Front 73

Little tolerance develops to which opiate action?
a) Constipation
b) Diarrhea
c) Respiratory depression
d) Analgesia
e) Nausea and vomiting

Back 73

Constipation

Front 74

What effects of opioids do patients rapidly become tolerant to?

Back 74

Nausea and vomiting

Front 75

What effects of opioids do patients more gradually become tolerant to?

Back 75

- Analgesia (must increase dose)
- Euphoria
- Respiratory depression
- Endocrine effects

Front 76

What effects of opioids do patients rarely become tolerant to?

Back 76

- Constipation
- Miosis

Front 77

How do you evaluate for substance dependence to opioids?

Back 77

3 out of 7 over 12 months (TWITCH-AR)
- Tolerance
- Withdrawal
- Intention
- Time
- inability to Cut down
- use despite Harm
- Activities Reduced

Front 78

How many of these findings does someone need to have over what time period to be given a diagnosis of substance dependence:
- Tolerance
- Withdrawal
- Intention
- Time
- inability to Cut down
- use despite Harm
- Activities Reduced

Back 78

3 out of 7 in 12 months

Front 79

What are the symptoms 6-12 hours after morphine withdrawal in a patient with physical dependence?

Back 79

- Drug-seeking behavior
- Restlessness
- Lacrimatino
- Rhinorrhea
- Sweating
- Yawning

Front 80

What are the symptoms 12-24 hours after morphine withdrawal in a patient with physical dependence?

Back 80

- Restless sleep for several hours
- Irritability
- Tremor
- Dilated pupils
- Anorexia
- Goosebumps

Front 81

What are the symptoms 24-72 hours after morphine withdrawal in a patient with physical dependence?

Back 81

- Increased intensity of the symptoms seen from 6-24 hours
- Weakness
- Depression
- Nausea and vomiting
- Intestinal cramps and diarrhea
- Alternating chills and flushes
- Aches and pains
- Increased HR and BP
- Involuntary movements of arms and legs
- Dehydration and possible electrolyte imbalance

Front 82

What are the symptoms >72 hours after morphine withdrawal in a patient with physical dependence?

Back 82

- Symptoms from <72 hours of autonomic hyperactivity
- Alternates with brief periods of restless sleep with gradual decrease in intensity until addict recovers (7-10 days)
- Still exhibit strong cravings for drug
- Some mild signs and symptoms are detectable for up to 6 months
- Delayed growth and development in infants born to addicted mothers may be detected for up to 1 year

Front 83

How long will patients with a physical dependence on opioids have symptoms?

Back 83

- 7-10 days of physical symptoms
- Cravings for up to 6 months

Front 84

How long does it take for heroin, morphine, and methadone effects to wear off?

Back 84

- Heroin: 4 hours
- Morphine: 4-5 hours
- Methadone: 8-12 hours

Front 85

How long does it take for heroin, morphine, and methadone withdrawal symptoms to appear?

Back 85

- Heroin: 8-12 hours
- Morphine: 8-12 hours
- Methadone: 36-72 hours

Front 86

How long does it take for heroin, morphine, and methadone peak withdrawal symptoms to occur?

Back 86

- Heroin: 36-72 hours
- Morphine: 36-72 hours
- Methadone: 96-144 hours

Front 87

How do you diagnose substance abuse?

Back 87

1 out of 4 in 12 months, HOLES:
- Hazards: use despite harm / risky situations
- Occupational impairment
- LEgal problems
- Social/interpersonal consequences

Front 88

What is "physical dependence"?

Back 88

A state of adaptation

Front 89

What is "tolerance and withdrawal"?

Back 89

Don't apply as criteria for addiction, because anyone taking opioids chronically will develop tolerance and experience withdrawal if meds are abruptly discontinued

Front 90

What are the characteristics of addiction?

Back 90

Primary, chronic, neurobiologic disease:
- Impaired control over drug use
- Craving
- Compulsive use
- Continued use despite harm

Front 91

Opioid withdrawal produces all of the following except?
a) Piloerection
b) Involuntary movements of the limbs
c) Convulsions
d) Dilated pupils
e) It produces all of the above.

Back 91

Convulsions

Front 92

What drug withdrawal can cause convulsions, which can cause death?

Back 92

Alcohol

Front 93

What increases the risk of overdose?

Back 93

- Decreased tolerance (ie, after a detox program, hospital stay, or jail and they return to the same amount as before)
- Mixing opioids with benzos and alcohol
- Other health issues: asthma, liver/heart disease, AIDS, malnourishment
- Previous overdose
- Mode of administration

Front 94

What is the mechanism of Naloxone?

Back 94

Opioid antagonist

Front 95

What is the effect of Naloxone (Narcan)?

Back 95

- Non-addictive prescription medication
- Only works if a person has opioids in their system (so if it is not a drug overdose, nothing happens)
- Used in IM, IV, SC form and can be used intranasally with atomizer
- Can induce acute withdrawal in opioid-dependent person