Pain Mechanisms - Chronic

Question 1

What is primary hyperalgesia?

Answer 1

Hyperalgesia at site of injury

Question 2

What is secondary hyperalgesia?

Answer 2

Hyperalgesia at uninjured areas

Question 3

What causes a change from acute to chronic?

Answer 3

Sensitised processing

Question 4

What is sensitisation?

Answer 4

Decreased afferent firing threshold
Increased response to fixed stimulus
Increase spontaneous activity

Question 5

What is neuropathic pain?

Answer 5

Pain caused by a primary lesion or dysfunction in the NS

Question 6

What are the sensations of neuropathic pain?

Answer 6

Numbness
Tingling
Burning
Pins + needles

Question 6

What is allodynia?

Answer 6

Pain from a stimulus that does not normally evoke pain

Question 7

What is hyperalgesia?

Answer 7

Exaggerated response to a normally painful stimulus

Question 8

Describe inflammatory pain (chronic) model

Answer 8

Constant activation + sensitisation of C-type primary afferents
= release neuropeptides
= neurogenic inflammation in the periphery
= increased spinal excitability
= increased sensitivity

Question 9

Describe neuropathic pain model

Answer 9

C fibres lose synaptic contact in spinal cord
= large myelinated fibres sprout to site into SDH
Large fibres also develop abnormal ectopic discharges
= generator of neuropathic pain

Question 10

What are the generator sites of ectopic activity in chronic pain?

Answer 10

Increase Na+ currents
Decreases K+ currents

Question 11

Describe inflammatory pain (chronic)

Answer 11

Stimulus = inflammation
Sensory neuron = nociceptor + non-nociceptor
Site = PNS + CNS
Channels = TRP