Neuropathic Pain, Pain Matrix Dysfunction, and Pain Syndromes

Question 1

What are the four types of chronic pain?

Answer 1

1. Nociceptive (mechanical, cancer, burns)
2. Neuropathic (nerve entrapment, central pain, neuropathy)
3. Pain matrix dysfunction (fibromyalgia, chronic whiplash, headache)
4. Pain syndromes (CRPS, chronic LBP syndrome)

Question 2

pain arising as a direct consequence of a lesion or disease affecting the somatosensory system, which can be anywhere in the somatosensory system (mechanical LBP, cancer, arthritis, burns)

Answer 2

Neuropathic pain

Question 3

Individuals with genetic codes that produce less of the enzyme that regulates the levels of _______ and ______ are twice as likely to develop neuropathic pain as those who produce more of the enzyme

Answer 3

catecholamine; encephalin

Question 4

painless abnormal sensation in the absence of nociceptor stimulation (tingling sensations)

Answer 4

Paresthesia

Question 5

unpleasant abnormal sensation, either evoked or spontaneous (painful)

Answer 5

Dysethesia

Question 6

pain evoked by a stimulus that normally would not cause pain (usually light touch)

Answer 6

Allodynia

Question 7

excessive sensitivity to stimuli that are normally mildly painful in uninjured tissue

Answer 7

Secondary hyperalgesia

Question 8

What are the symptoms of neuropathic pain?

Answer 8

1. Paresthesia
2. Dysesthesia
3. Allodynia
4. Secondary hyperalgesia

Question 9

What are the 5 mechanisms that produce neuropathic pain?

Answer 9

1. Ectopic foci
2. Ephaptic transmission
3. Central sensitization
4. Structural reorganization
5. Altered top-down modulation

Question 10

When myelin is damaged, signals from the exposed axon stimulate excessive production of mechanosensitive and chemosensitive ion channels; Channels are inserted into the demyelinated membrane, producing abnormal sensitivity to mechanical and chemical stimuli; Demyelinated regions take on the new, pathologic role of generating action potentials in addition to the normal role of conducting action potentials

Answer 10

Ectopic foci

Question 11

Cross-talk between axons in regions of demyelination

Answer 11

Ephaptic Transmission

Question 12

Test where you tap along a nerve, the point where a nerve is injured becomes more sensitive; region where schwann cells are damaged, so insulation between axons is lost and one axon may stimulate its neighbor

Answer 12

Tinel’s sign

Question 13

Occurs in the CNS; greater peripheral nerve sensitization occurs, so also has greater sensitization in CNS, resulting in increased perception of pain; as intense pain is prolonged, the CNS changes and everything becomes painful, no matter what the peripheral input is; pain does not reverse back to normal input

Answer 13

Central sensitization

Question 14

Loss of nociceptive neuron from the body; sprouting occurs where touch sensation neuron makes connections with neurons that carry nociceptive information to the brain; hard to get back to normal

Answer 14

Structural reorganization

Question 15

Antinociceptive pathways are decreased/inhibited/lost, so pain stimulus is increased because pronociceptive signals are not inhibited

Answer 15

Pain matrix dysfunction

Question 16

Neuropathic pain arise from abnormal activity in the

Answer 16

1. Periphery (e.g., nerve compression in carpal tunnel syndrome)
2. CNS in response to deafferentation
3. Dorsal horn

Question 17

__________ generation of neuropathic pain can occur as a result of:

• Injury or disease of the peripheral nerves often results in sensory abnormalities.
• Complete nerve resection results in a lack of sensation from that nerve’s receptive field.
• Partial damage can result in allodynia and sensations similar to an electric shock.

Answer 17

Peripheral

Question 18

What are the peripheral abnormalities causing neuropathic pain?

Answer 18

1. Development of ephaptic transmission that occurs in demyelinated regions
2. Ectopic foci in an injured nerve that occurs at the nerve stump, in areas of myelin damage, or in dorsal root ganglion somas

Question 19

Central response to _______:
Occurs when a nerve loses its input so the receiving neuron becomes more sensitive to any stimulus; Avulsion of dorsal roots from the spinal cord produces ___(same word)___ and causes an individual to feel burning pain in the area of sensory loss; Neurons in the CNS may become abnormally active when peripheral sensory information is completely absent

Answer 19

Deafferentation

Question 20

refers to individuals who have had a limb amputated but experience sensations that seem to originate from the missing limb

Answer 20

Phantom limb sensation

Question 21

Phantom sensation that is painful; reports of this are more rare

Answer 21

Phantom pain
- must be differentiated from residual limb pain; treatment for residual limb pain is different than for phantom limb pain

Question 22

caused by a lesion of the CNS and is usually localized to the area of the body deafferented by the lesion; refers to burning, shooting, aching, freezing, or tingling pain

Answer 22

neuropathic central pain

Question 23

the thalamus may be the site of pain generation because after a SCI, the neurons in the VPL thalamic nucleus are spontaneously active without input from the spinal cord

Answer 23

SCI central pain

Question 24

Where does pain occur due to MS central pain?

Answer 24

Depends on the location of the lesion

Question 25

Top-down regulation of pain is disturbed when this occurs; Antinociception is reduced and/or pronociception is intensified; the result is increased pain; Fibromyalgia, episodic tension-type headache, migraine, and chronic whiplash-associated disorder are all the rest of this

Answer 25

pain matrix dysfunction

Question 26

What are the criteria for episodic tension-type headache?

Answer 26

1. Mild-to-moderate pain, usually bilateral
2. Lasting 30 minutes to 7 days
3. Not aggravated by physical activity
4. Not associated with nausea or vomiting
   - Photophobia or phonophobia, but not both, may accompany the headache.
   - Mechanism appears to be supersensitivity to nitric oxide

Question 27

What are two pain syndromes that involve other systems in addition to the pain system?

Answer 27

1. Complex regional pain syndrome - involves the somatosensory, autonomic, and motor systems
2. Chronic low back pain syndrome - involves muscle guarding, disuse, and abnormal movements

Question 28

Response to injured body part due to pt not using affected part; increased levels of inflammatory neurochemicals in the periphery, partial denervation of epidermis and upper dermis, impairment of sympathetic regulation of blood flow and sweating, sensitization, and cortical reorganization; early intervention has best outcome; intensive PT often required; some cases are intractable

Answer 28

Complex regional pain syndrome

Question 29

decreased endurance of abdominal and back muscles

Answer 29

Chronic low back pain

Question 30

What is the surgical treatment of chronic pain?

Answer 30

dorsal rhizotomy

-often fails in practice; only short term

Question 31

Why does dorsal rhizotomy fail?

Answer 31

may be the result of CNS changes in response to the original maintained pain or to pain-mediating fibers traveling in the dorsal columns

Question 32

Where does acetaminophen work?

Answer 32

peripheral nervous system

Question 33

Where do selective norepinephrine reuptake inhibitors work?

Answer 33

1. Dorsal horn of spinal cord

2. Cerebral cortex

Question 34

Where do cannabinoids?

Answer 34

Raffe neuclei (Rostral ventromedial medulla)

Question 35

Where do SSRIs work?

Answer 35

cerebral cortex

Question 36

where do NSAIDs work?

Answer 36

1. PNS

2. Periaqueductal gray

Question 37

Where do opioids work?

Answer 37

1. Dorsal horn
2. Raffe nuclei (Rostral ventromedial medulla)
3. Periaqueductal gray
4. Cerebral cortex

Question 38

What three Ds must therapists address for chronic pain?

Answer 38

1. Distress
2. Disuse
3. Disability

Question 39

What psychologic interventions may decrease activation of pain systems and improve coping skills?

Answer 39

1. relaxation (breathing, m. relaxation)
2. biofeedback
3. imagery
4. cognitive behavioral therapy

Question 40

any genuine psychological or physiologic effect which is attributable to receiving a substance or undergoing a procedure, but is not due to the inherent powers of that substance or procedure

Answer 40

Placebo-associated improvement

Question 41

Where do tricyclic antidepressants work?

Answer 41

1. dorsal horn of SC

2. Cerebral cortex

Question 42

Abnormal central processing of pain signals in both pain amplification and impaired defending inhibition; incr. levels of substance P and glutamate in SC; decreased pain inhibition from brainstem to dorsal horn

Answer 42

fibromyalgia