Neuropathic Pain Flashcards

0
Q

What is neuropathic pain?

A
  • pain initiated by lesion or dysfunction of the somatosensory system, resulting in abnormal activity of the somatosensory pathway
  • can result from drugs, disease or trauma
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1
Q

What is nociceptive pain?

A

acute pain associated with injury and inflammation

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2
Q

What are some triggers of neuropathic pain?

A
  • alcoholism
  • amputation
  • diabetes
  • drugs (ex. chemo)
  • herpes zoster (shingles)
  • HIV or AIDS
  • MS
  • spinal injury
  • stroke
  • tumor
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3
Q

What are the name of the nerve fibers that carry pain and temperature sensations?

A

A gamma - small, myelinated

C - small, demyelinated

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4
Q

What is the name of the nerve fiber that carries touch sensations?

A

A beta fibers - large, myelinated

  • these are the fibers that contribute to allodynia
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5
Q

What is allodynia?

A

Pain resulting from a non-painful stimulus

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6
Q

Where is myelin produced in the PNS?

CNS?

A

Schwann Cells

Oligodendrocytes

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7
Q

Describe the pain pathway from the source

A
  • pain source in A gamma and C nerve fibers
  • peripheral nerves to afferent dorsal horn
  • into brain’s sensory cortex
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8
Q

Excitatory neurotransmitters bind to post-synaptic membranes and cause _______________.
What are the excitatory neurotransmitters?

A

depolarization

Glutamate (A gamma)
Substance P (C)
Aspartate

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9
Q

Inhibitory neurotransmitters bind to post-synaptic membranes and cause _______________.
What are the inhibitory neurotransmitters?

A

hyperpolarization

GABA
Glycine

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10
Q

What can cause hyperexcitability?

A
  • increase of excitatory NTs
  • decrease of inhibitory NTs
  • increase of cell permeability (Na+ and Ca2+ will increase intracellularly)
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11
Q

What does the term “windup” mean when referring to NPP?

A
  • when adjacent neurons produce AP due to ectopic firing

- increases the pain signal

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12
Q

What happens to the pain signal when the inner cell becomes more positive?

A

The pain signal will become stronger

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13
Q

What are the symptoms of NPP?

A
  • burning
  • tingling
  • pins and needles
  • shooting
  • stabbing
  • numbness
  • jabbing
  • throbbing
  • aching
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14
Q

What is hyperalgesia?

A

higher pain response than usual to a normally painful stimulus

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15
Q

What is paraesthesia?

A

abnormal numbing or prickling of skin

16
Q

What is the pain triad of NPP?

A
  1. NPP
  2. Psychological symptoms
  3. Sleep Disturbances

can include:

  • insomnia
  • fatigue
  • lack of concentration
  • depression
  • anxiety
  • stress
17
Q

How to TCAs (tricyclic antidepressants) help with NPP?

A
  • they block the tricyclic reuptake of NE and 5-HT
  • blocks Na+ and Ca2+ channels
  • blocks NMDA receptors
  • that will help with mood
  • serotonin is good for sleep
  • so TCAs will help with mood, pain and sleep
18
Q

How is NPP diagnosed?

A
  • DN4 questionnaire (4 or more/10 = NPP)
  • visual analogous scale
  • clinical presentation of 2-3 sx
19
Q

What are the 4 point of focus to treat NPP?

A
  1. inhibition of first order sensory afferents (site of pain)
  2. synaptic inhibition between 1st order sensory afferent and DRG
  3. synaptic inhibition between DRG and dorsal horn interneurons
  4. synaptic inhibition between dorsal horn interneurons and ascending tract
20
Q

APs can be regulated by decreasing excitation or increasing inhibition.
How do we do this?

A

Decreasing excitation:

  • Na+ blockers
  • inhibit Ca2+ channels
  • block excitatory NTs (Glutamate, Aspartate, Substance P)

Increase inhibition:

  • GABA agonists
  • NE and 5-HT reuptake inhibitors
21
Q

How do antiepileptics help with NPP?

A
  • reduce influx of Na+ and Ca2+
  • enhance inhibitory effects of GABA
  • reduce concentration of glutamate and/or blocks NMDA receptors
22
Q

How do SSRIs help with NPP?

A
  • it inhibits serotonin reuptake without affecting NE
23
Q

Can NPP be cured?

A
  • only 20% of patients have complete pain cessation with treatment
  • the other 80% can only have their pain lowered to a more tolerable level.
24
Q

What is the definition of pain?

A
  • an unpleasant sensory and emotional experience associated with actual or potential tissue damage
25
Q

What substances shut off the pain pathway?

A
  • NE
  • E
  • GABA
  • serotonin
  • endogenous opiods (endorphins, encephalins, cannabinoids)