Lec 03: Neuropathic Pain

Question 1

True or False: Neuropathic pain is a disease.

Answer 1

FALSE. It is a syndrome. It is found in many neurologic conditions, affecting both the central and peripheral nervous system.

Question 2

The physiologic detection of injury or potentially tissue-damaging thermal, chemical energy impinging upon specialized nerve endings that mediate pain sensation.

a. Nociception
b. Pain
c. Suffering
d. Pain behavior

Answer 2

a. Nociception

Question 3

Advocated to be the 5th
vital sign.

a. Nociception
b. Pain
c. Suffering
d. Pain behavior

Answer 3

b. Pain

Question 4

Unpleasant sensory and emotional experiences
associated with actual or potential tissue damage; the actual sensation and emotion.

a. Nociception
b. Pain
c. Suffering
d. Pain behavior

Answer 4

b. Pain

Question 5

Feelings/emotions elicited because of pain.

a. Nociception
b. Pain
c. Suffering
d. Pain behavior

Answer 5

c. Suffering

Question 6

The reaction to the pain.

a. Nociception
b. Pain
c. Suffering
d. Pain behavior

Answer 6

d. Pain behavior

Question 7

Any type of output that is commonly understood to suggest the existence of a tissue-damaging stimulus.

a. Nociception
b. Pain
c. Suffering
d. Pain behavior

Answer 7

d. Pain behavior

Question 8

True or False: The quality and quantity of sleep is affected by pain.

Answer 8

True.

Question 9

ACUTE or CHRONIC pain?

Physiologic in nature.

Answer 9

ACUTE.

• Chronic more often a pathologic phenomenon

Question 10

ACUTE or CHRONIC pain?

Due to obvious tissue damage

Answer 10

ACUTE.

*Chronic pain is more often due to loss of protective function and degradation of health and function.

Question 11

ACUTE or CHRONIC pain?

Serves a protective function.

Answer 11

ACUTE.

Question 12

ACUTE or CHRONIC pain?

Pain resolves upon healing.

Answer 12

ACUTE.

*Chronic pain lasts beyond normal time for healing.

Question 13

All of the following are examples of nociceptive pain, EXCEPT:

a. Pain due to inflammation
b. Joint pain in osteoarthritis
c. Limb pain after a fracture
d. Nerve entrapment

Answer 13

d. Nerve entrapment
* Nociceptive pain is due to direct stimulation of nociceptors and more LOCALIZED.

REMEMBER that Neuropathic pain is initiated by a primary lesion or dysfunction within the nervous system itself.

Question 14

Which of the following is classified as MIXED pain?

a. Postherpetic neuralgia
b. Post-operative visceral pain
c. Thalamic Pain
d. Carpat tunnel syndrome

Answer 14

d. Carpal tunnel syndrome.
- Mixed pain means pain with both neuropathic and nociceptive components. Examples include, cancer pain: nociceptive, when mass effects of the tumor include direct stimulation and compression of nerve bundles and neuropathic due to direct nerve lesions and effects of chemotherapeutic agents.

Question 15

Which of the following is incorrectly paired?

a. Spinothalamic tract - Direct - pain and temperature
b. Spinoreticular - Indirect - autonomous response
c. Spinomesencephalic - Direct - affect
d. Spinoreticular - Indirect - arousal

Answer 15

c. Spinomesencephalic - Direct - affect

The spinomesencephalic tract is indirect.

Question 16

fast, thinly myelinated “aray” fibers.

Answer 16

A-delta fibers

Question 17

slow, unmyelinated “hapdi” fibers.

Answer 17

C fibers

Question 18

ACUTE or CHRONIC pain?

AMPA Receptor

Answer 18

ACUTE.

The AMPA receptor is a directly ionotropic non-NMDA receptor and is responsible for acute pain.

Question 19

Necessary for NMDA receptor to activate

Answer 19

Glycine moeity.

Question 20

Periaqueductal Gray Matter is rich in opiate-secreting neurons called:

Answer 20

enkephalins

Question 21

The fastest neuron.

Answer 21

Alpha motor neuron.

*Alpha motor neuron > A-beta touch fibers > A-delta fiber > C-fibers

Question 22

Abnormal but not painful.

a. Dysesthesia
b. Paresthesia
c. Allodynia
d. Hyperpathia

Answer 22

b. Paresthesia
- Paresthesias are a type of positive sensory, spontaneous symptom of neuropathic pain.
ex: sensation of crawling ants, tingling
* Dysesthesia - abnormal and painful. Ex. shooting, electric-like, burning.

Question 23

Painful response to a nonpainful stimulus.

a. Dysesthesia
b. Paresthesia
c. Allodynia
d. Hyperpathia

Answer 23

c. Allodynia

Allodynia is a stimulus evoked symptom of Neuropathic pain (still under postive sensory symptoms)
e.g. pain when wind and bed covers brush on skin

*ALLODYNIA IS PATHOGNOMONIC for Neuropathic pain

Question 24

Delayed, explosive pain/sustained pain to painful stimulus even if it is removed.

a. Dysesthesia
b. Paresthesia
c. Allodynia
d. Hyperpathia

Answer 24

d. Hyperpathia.

Other types of stimulus-evoked symptoms of neuropathic pain:

allodynia - painful response to a nonpainful stimulus

hyperalgesia - heightened response to a PAINFUL stimulus.

Question 25

The progressive increase in the response of the system to repeated stimuli.

Answer 25

Activation-dependent plasticity.

Question 26

What are the mechanisms of pain chronification?

Answer 26

1) ECTOPIC DISCHARGES - Increased pain experience that eventually worsens to experiencing pain even without stimulus, due to a nerve cell injury that increases excitability of the cell. 2) PERIPHERAL SENSITIZATION - . An initial noxious stimulus results in nerve damage and the release of substance P and prostaglandins. The release of these mediators forms an inflammatory soup, which sensitizes the adjoining afferent fibers. This leads to pain sensation beyond the area initially affected. 3) WIND UP - Due to the repetitive charges transmitted to the dorsal horn neurons by the C-fibers, adjacent dorsal horn neurons are stimulated, thus the pain sensation is greater, giving rise to hyperalgesia. 4) STIMULUS-DEPENDENT CENTRAL SENSITIZATION - appearance of early genes and gene expression and chronification of pain, resulting from activation of both AMPA and NMDA receptors. Forms "pain memory". 5) DISINHIBITION - In neuropathic pain, the descending inhibitory control is lost, thus the nociceptors are more active, and there is greater transmission to the Dorsal Horn Nucleus, which results into greater pain sensation.

Question 27

Identify the sites of action of the following drugs: TCAs - Anti-convulsants - NSAIDS - Opioids -

Answer 27

1) TCAs - PNs, Spinal cord, CNS MOA: inhibition of reuptake of serotonin and norepinephrine -> Increased levels of serotonin and norepinephrine in the CNS -> Greater inhibition on the dorsal horn neuron; also inhibit of Na+ channels, NMDA receptors 2) Anti-convulsants - PNs, Spinal Cord MOA: inhibition of action potential (PNs) and inhibit reuptake of norepinephrine (Spinal cord) 3) NSAIDS - terminal nociceptors MOA: inhibit prostaglandins 4) Opioids - PNs, Spinal Cord, CNS MOA: inhibit action potential, inhibit reuptake of norepinephrine and epinephrine, etc.

Question 28

The drug of choice for painful DM neuropathy a. Clonazepam b. Carbamazepine c. Gabapentin d. Lamotrigine

Answer 28

c. Gabapentin | - Decreases Calcium channel activity at presynaptic neuron and block release of pain neurotransmitters.

Question 29

The drug of choice for trigeminal neuralgia. a. Clonazepam b. Carbamazepine c. Gabapentin d. Lamotrigine

Answer 29

a. Clonazepam | - Increases GABA activity. (It is an anticonvulsant)

Question 30

Has the least amount of side effects since it bypasses the liver and have little drug-drug interactions: a. Clonazepam b. Carbamazepine c. Gabapentin d. Lamotrigine

Answer 30

c. Gabapentin * Gabapentin and Pregabalin. * TCAs have the most side effects. So don't give to elderly patients since it may cause arryhtmia and have uncomfortable side effects.

Question 31

Depletes substance P from sensory nerves in skin. a. Capsaicin b. Lidocaine c. Tramadol d. Pregabalin

Answer 31

a. Capsaicin