CRPS

Question 1

Define CRPS

Answer 1

• pain with associated motor, sensory, autonomic, trophiic abnormalities with symptoms beyond the area of primary damange; patients have psychological damage
• Type 1 - without nerve injury
• Type 2 - with nerve injury

Question 2

Describe CRPS prevalence

Answer 2

• rare
• 1% develop it after nerve or bone injury
• UL > LL
• most have hx of trauma
• period of immobilisation
• 25-30% achieve full recovery

Question 3

Wharts the CRPS diagnostic criteria

Answer 3

1. Persistent pain disproportionate to type injury
2. At least 1 symptom in 3 of (sensory, vasomotor, sudomotor, motor)
3. At least 1 sign in 2 of (sensory, vasomotor etc)
4. Exclusion of other possibilities

Question 4

What are the risk factors for CRPS?

Answer 4

Female (5:1)
Immobilisation
Fracture type of injury
Pain >5 within 1st week of fracture
hx of migraine or asthma (bc this indicates neurogenic inflammation)
Genetic factors - mutation to TNF alpha gene
Psychological

Question 5

What are clinical features of central sensitization?

Answer 5

Hyperalgesia
Allodynia
'Wind up'
Spread of pain
Poor stimulus-response 
Psychosocial element

Question 6

What are the brain changes seen in central sens?

Answer 6

• increased excitability of somatosensory cortex
• changers in primary somatosensory cortex
• changes to blood O2 signals in the cortex
• sens of the brainstem

Question 7

What components does pathophys of CRPS include?

Answer 7

Immune system (inflammation causes peripheral sensitization)
Vasomotor
CNS (psychosocial, cortical plasticity, sensitization)

Question 8

Describe the immune system response

Answer 8

1. Trauma causes senstization of primary afferents by cytokines
2. Substance P and CGRP is released
3. Vasodialation and protein extravasation
4. elevated CGRP thought to be reason for CRPS; TNF alpha and IL-6 causes hyperalgesia

Question 9

Describe the vasomotor system response

Answer 9

• limb is warmer in the early stages and colder in the later stages
• with CRPS there’s inhibition of vasoconstriction - thats why you get swelling and warmer limb (d/t fxnal changes in the SC, brainstem
• increased responsiveness of alpha adrenergic receptors in the skin
• nociceptors develop sensitivity to catecholamines (E+NE) > hyperactive BVs - colder limb in chronic stage

Question 10

What are the 2 primary mechanisms that sympathetic nervous system contributes to CRPS?

Answer 10

1. nociceptors sensitized by catecholamines; injury = more expression of alpha adreno-receptors
2. sprouting of sympathetic axons into DSG

Question 11

Define central sensitization

Answer 11

amplification of neural signalling within the CNS that causes hypersensitivity

Question 12

Describe cortical changes

Answer 12

• distortions of limb representations
• neglect towards affected limb
• limb can feel foreign

Question 13

What fracture characteristics may predict likelihood to develop CRPS?

Answer 13

1. fracture/dislocation
2. intraarticular fracture
3. RA
4. MSK co-morbidities

Question 14

what are 4 characteristics of central sensitization

Answer 14

1. increased pain activity
2. sprouting in the dorsal horn
3. brain changes
4. allodynia/hyperalgesia

Question 15

What is cortical reorganization? smudging?

Answer 15

• reorganization of motor/sensory maps on the brain
• smudging is the poor differentiation between different adjacent parts of the body - leads to poor specificity in movements; poor 2 pt discrimination

Question 16

What clinical features might cortical smudging explain?

Answer 16

• body perception disturbance
• poor tactile discrimination
• referred sensations and mislocalisations