Chronic or Persistent Pain Flashcards
What are A fibres?
- Myelinated somatic nerve fibres
- Largest in diameter, fastest conduction
- Divided into alpha, beta, gamma & delta
What do delta fibres transmit?
Messages concerning pain, temperature & touch
What fibres are sharp and dull pain transmitted by?
- Sharp: A-delta fibres
- Dull: Slow transmitting, unmyelinated C fibres
How is pain from above and below the neck transmitted?
- Neck & below: Afferent neurons of spinal nerves
- Head: Sensory fibres of cranial nerves 5, 7, 9 & 10
How does the scientific community think persistent pain occurs?
- Via neuroplasticity
- In the lamina, there are 5 wide dynamic range (WDR) 2nd order nociceptors
What are the characteristics of WDR?
- High threshold
- Highly adaptable
- Main cause of chronic pain
What are the 3 stages of adaptation of WDR?
- Potentiation
- Intra-terminal genetic expression
- Genetic expression (make more receptors in the brain)
What is the effect of passive interventions on WDR?
Passive interventions such as massage/touch may keeps exciting WDR, i.e. passive interventions may prolong/worsen chronic pain
What happens in the potentiation stage?
- If WDR get used a lot, they adapt
- Many adaptations
- More chemicals made
- Message transmitted earlier
- Increase in resting level of excitement of cell’s action potential to fire
What happens in the intra-terminal genetic expression stage?
- Holds open receptors
- Double sodium than normal gets into nerve cells (tells brain there is double the amount of pain)
- No extra messages come from injured tissue
What happens in the genetic expression stage?
- Receptors mutate, so will take up other chemicals that are available
- E.g. adrenaline (why some chronic pain patients complain of increased pain with anger)
What is the order of response to pain in the brain?
- Anterior cingulate cortex: attention
- Prefrontal cortex: Forward planning, emotion
- S1: Localisation, intensity
- S2
- Insular
- Thalamus
What is the process of pain transmission?
- Peripheral signal: Generator/receptor chemical
- Signal amplifier: Spinal cord neuroplasticity
- Signal receiver: Brain
- Signal modulator: Brain
- Inhibitory dysfunction: Brain
- Descending input: Brain to spinal cord
- Efferent output from spinal cord to muscles
What is the difference before descending inhibition & facilitation?
- Descending inhibition: “It’s not that dangerous”
- Descending facilitation: “It’s more dangerous than that”
What is kinesiaphobia?
Fear of movement (pain)
What is the Tampa measure?
Fear avoidance measure
What is an example that can be used to explain how pain is not always caused by tissue damage?
Phantom limb pain
How should pain be considered?
- As a human experience, rather than a marker of injury
- Perceived differently by everyone
What does chronic pain syndrome appear to reflect?
- A failure to adapt, i.e. the individual cannot cope with the unimproved symptoms
- The presence of factors that interfere with adaptation may promote chronic pain (e.g. depression, inactivity, relationship problems)
What are orange flags?
Mental health factors
- Mental health disorders
- Personality disorders
What are yellow flags?
- Unhelpful beliefs about injury
- Poor coping strategies
- Pasive role in recovery
What are blue flags?
Social factors
- Low social support
- Unpleasant work
- Low job satisfaction
- Excessive work demands
- Non-English speaking
- Sense of injustice
- Problems outside work
What are black flags?
Other factors
- Threats to financial security
- Litigation
- Compensation thresholds
When will the brain produce pain?
When the brain concludes that:
- Danger to the body tissue exists
- Action is required
What influences people’s perception of pain?
- Sensory input from the body
- Previous experience
- Cultural factors
- Social/work environment
- Expectations about consequences of danger/pain
- Beliefs, knowledge & logic
What other body systems are affected by pain?
- SNS
- Motor
- Endocrine
- Immune
How is the SNS affected by chronic pain?
- Adrenaline activates WDR & sensitised C fibres
- Difficulty sleeping & healing
- Blood sugar difficulties
- Agitation
How is motor function affected by chronic pain?
- Motor control problems
- Sustained tissue load
- Secondary injury/nociceptive input
How is the endocrine system affected by chronic pain?
- Sustained cortisol levels
- Tissue breakdown
- Immune difficulties
- No sex drive
- Poor digestion
- Constipation
How is the immune system affected by chronic pain?
- Glia attacked
- Neurones sensitised
- Spreading pain in a non-dermatomal & non-Penfold’s homunculus distribution
What is the most important intervention for chronic pain?
Education
Where does pain modulation occur?
Spinal cord (control of transmission of nociceptive info) & in the cerebral cortex
When do WDR neurons become more sensitised?
After repeated activation of nociceptors
What happens when WDR neurons become more sensitised?
Stimulation of affected body part (which is normally not painful) is now capable of evoking pain) - Reversible process
What is chronic pain?
- Sensitisation of WDR neurons remains present
- Primary afferent begins to form new connections between neurons
- Inhibitory interneurons die
- Pain signals are augmented
- Irreversible process
What is pain perception influenced by?
Prior experience & the context in which the noxious stimulus occurs
