Week 4: Pain

Question 1

Pain is classified as 3 different types. What are they?

Answer 1

Nociceptive – archetypal mechanism, the experience of pain is evoked by damage to somatic or visceral tissues e.g.,
Neurogenic / Neuropathic arises from abnormal activity in nerves that transmit nociceptive pain
Psychogenic: from influences in the subjects mind, such as memory, association with
past events and malingering

Question 2

Pain generation. what are the 4 key components?

Answer 2

1. Transduction
2. Peripheral Transmission 3. Central Transmission
3. Modulation

Question 3

1. Transduction

Answer 3

• tissue damaged is detected by free nerve endings
• stimulated by creating a change in the body
• chemically (e.g. bradykinins, serotonin, inflammation response)
• mechanically (e.g. stretch caused by swelling from hemmorage or tumor)

Question 4

2. Peripheral transmission of pain

Answer 4

-pick up and relay the info from the free nerve endings
-C fibres= transmit, thermal and chemical stimuli
A-delta= mechanical sensations at low stimulus intensity but pain at higher levels
Note: there aren’t specialised nerve fibres for pain transmission. ts mediated by nerves that have other functions.
Pathway of the afferents:
a) info picked up mostly by dorsal roots-depending
-depending on volume of information it will run up or down a couple of levels which is why we feel pain in broader areas.

Question 5

3. Central transmission of pain?

Answer 5

Spinothalamic tract:

• control/ modulation in Rexes Laminae
• then goes up to the thalamus were it is processed by 3 components
  1. Limbic system- emotional dimensions of stimulus (brain will process pain in different ways for different people)
• allodynia= lowering of the pain threshold

2. Parietal lobe for location/ origin of stimulus
3. Reticular formation of brainstem (anterolateral funiculus= spinothalamic tracts)
   - reticular formation filters incoming stimuli to discriminate from relevant and irrelevant.

Question 6

4. Modulation of Pain

Answer 6

Its the feedback loop that modulates the level, intensity and severity of pain

• send info down into spinal cord to excerpt inhibitory effects on ascending traffic
• in chronic pain, pain is processed in smaller areas due to CNS changes

Question 7

What are some of the pain Interventions?

Answer 7

1. Transduction - at level of the skin- corticosteroids or NSAIDS
2. Peripheral transmission -nerve relaying
   - anaesthetic blocks (cut the nerve, knock out the receptors)
3. central transmission- spinal cord
   - SC stimulators (disturb afferent pain signals), spinal opoids
4. change the patients perception of pain

Question 8

Complex regional pain syndrome

There are 2 types

Answer 8

• previously called Reflex sympathetic dystrophy
• the whole system goes into overdrive
• central sensitisation (The brain has learnt how to process pain so efficiently that any sensation experienced is interpreted as pain)

Type 1:
-develops after a tissue trauma- not related to a single nerve
-allodynia with spontaneous burning, continuous pain not proportional to trauma made worse by movement, cold and touch
-will get skin vasomotor changes- temp, colour, focal oedema, moisturiser.
Phase1: (wees- 3 months)
-involved extremity is warm, oedematous and joints are tender
-increased sweating and hair growth
Phase 2 (3-6 months)
-thin, shiny, coll skin

Phase 3

• atrophy of the skin and subcutaneous tissue
• flexion contractures

Type 2 (causalgia):

• after injury to a specific peripheral nerve (usually a major nerve trunk)
• spontaneous pain develops within the nerve territory then spreads outside it.
• paroxysms of sharp, shooting or deep pain (similar to neuropathic Pain)

Question 9

Treatment of pain syndromes

Answer 9

• course of glucoocorticosteroids with early mobilisation and physical therapies
  2. NSAIDS
  3. Ca channel blockers
  4. Opioids- slippery path
  5. Stellate Ganglion blocks
  6. Psychological factors