Pathophysiology of Pain

Question 1

what is pain?

Answer 1

an unpleasant sensory and emotional experience which we primarily associate with tissue damage or describe in terms of damage.

Question 2

is pain a stimulus?

Answer 2

no

Question 3

describe the pain pathway from the periphery to modulation

Answer 3

> periphery there is detection and transmission to the spinal cord via first order neurons
spinal cord there is processing and transmission to the brain (thalamus) via second order neurons
brain there is perception, learning and response
modulation is the descending tracts

Question 4

what is nociception?

Answer 4

the detection of tissue damage by specialised transducers connected to A-delta and C fibres

Question 5

what are nociceptors?

Answer 5

free nerve ending of A delta and C fibres

Question 6

what do nociceptors respond to?

Answer 6

thermal, chemical, mechanical noxious stimuli

Question 7

where is the first order neurons cell body?

Answer 7

in the dorsal root ganglion

Question 8

describe A alpha and A beta fibres

Answer 8

> myelinated
large diameter
proprioception and light touch

Question 9

describe A-delta fibres

Answer 9

> lightly myelinated
medium diameter
nociception
fast/sharp pain

Question 10

describe C fibres

Answer 10

> unmyelinated
small diameter
slow conducting
innocuous temperature, itch, dull pain

Question 11

describe the neurons that will receive the input in the spinal dorsal horn

Answer 11

> nociceptive specific
low threshold mechanoceptive
wide dynamic range

Question 12

what does the lateral spinothalamic tract convey?

Answer 12

fast and slow pain (pain and temperature sensations)

Question 13

what does the anterior spinothalamic tract convey?

Answer 13

sensation of simple touch

Question 14

what rexed lamina does the spinothalamic tract arise from?

Answer 14

2 and 5

Question 15

what is the second relay station?

Answer 15

the thalamus

Question 16

what are the connections to the thalamus?

Answer 16

> cortex
limbic system
brainstem

Question 17

where does pain perception occur?

Answer 17

in the somatosensory cortex

Question 18

what is hyperalgesia?

Answer 18

increased perception of pain or even the perception of non-noxious stimuli as noxious.

Question 19

when does hyperalgesia occur?

Answer 19

whenever there is a tissue injury and inflammation, it occurs in the surrounding uninjured tissue

Question 20

what is allodynia?

Answer 20

is type of hyperalgesia where there is a decreased threshold for pain

Question 21

describe the changes in nociceptor in allodynia

Answer 21

there is decreased threshold for response

Question 22

describe the changes in nociceptor in hyperalgesia

Answer 22

exaggerated response to normal and supranormal stimuli

Question 23

describe gate control theory

Answer 23

non painful input closes the gate to the painful input, stopping it from travelling to the central nervous system. stimulation of a non-noxious input is able supress pain

Question 24

describe the changes in nociceptors in spontaneous pain

Answer 24

there is spontaneous activity in nerve fibres

Question 25

what is central sensitisation?

Answer 25

the response of second order neurons in the CNS to normal input both noxious and non-noxious

Question 26

name three main components in central sensitisation

Answer 26

> wind up > classical > long term potentiation

Question 27

describe wind up central sensitisation

Answer 27

> involves only activated synapses > homosynaptic activity dependent progressive increase in response of the neurons > manifests over the course of the stimuli and terminated with the stimuli

Question 28

in classical central sensitisation what is opened up in the dorsal horn?

Answer 28

new synapses, silent nociceptors

Question 29

in classical central sensitisation what is heterosynaptic activity dependent on?

Answer 29

plasticity

Question 30

describe onset of classical central sensitisation

Answer 30

it is immediate with the appropriate stimuli

Question 31

can the classical sensitisation outlast the initial stimuli duration?

Answer 31

yes and it can be maintained at low levels of ongoing stimuli

Question 32

describe long term potentiation

Answer 32

> involves mainly activated synapses | > occurs primarily for very intense stimuli

Question 33

what conditions involves supracentral sensitisation?

Answer 33

> fibromyalgia > chronic widespread pain > painful physical symptoms of depression/anxiety

Question 34

describe acute pain

Answer 34

``` > less than a month > usually obvious tissue damage > increased nervous system activity > resolves on healing > serves protective function > usually nociceptive ```

Question 35

describe chronic pain

Answer 35

``` > 3-6months or more > beyond expected period of healing > no protective function > degrades health and function > nociceptive/neuropathic/mixed ```

Question 36

what is nociceptive pain?

Answer 36

a sensory experience that occurs when specific peripheral sensory neurons respond to noxious stimuli

Question 37

in nociceptive pain is there often specific localisation?

Answer 37

yes, often describes and throbbing, aching, stiffness

Question 38

what is neuropathic pain?

Answer 38

pain initiated or caused by a primary lesion or dysfunction in the somatosensory nervous system

Question 39

describe the painful region in neuropathic pain

Answer 39

it is not necessarily in the same region as the site of injury but occurs in the neurological territory of the affected structure

Question 40

which responds to conventional analgesics better, nociceptive pain or neuropathic pain?

Answer 40

nociceptive pain

Question 41

what works on transduction of pain?

Answer 41

> NSAIDs > Ice > Rest > LA blockers

Question 42

what works on transmission of pain?

Answer 42

> nerve blocks > drugs (opioids, anticonvulsants) > surgery (DREZ, cordotomy)

Question 43

what works on the perception of pain?

Answer 43

``` > education > congnitive behavioural therapy > distraction > relaxation > graded motor imagery > mirror box therapy ```

Question 44

what works on descending modulation?

Answer 44

> placebos > drugs (opioids, antidepressants) > surgery (spinal cord stimulation)