W6 PRINCIPLES

What type of experience is pain?

A subjective experience

How does pain arise?

Stimulation of nociceptors due to tissue damage or potentially damaged tissue

Is the experience of pain the same between everyone?

No, the actual pain experience is highly variable

Talk through the schematic representation of pain modularity circuitry? (Rough af if we need to know this)

• Nociceptive inputs enter spinal dorsal horn through primary afferents that synapse onto transmission neurons

• Projection fibres ascend through contralateral spinothalamic tract, target= thalamus

• Collateral projections target mesencephalic nuclei, DRt, RVM, and midbrain PAG

• Descending projections from DRt critical to DNIC pathway

• Rostral projections from thalamus target cortical sites and amygdala

• Lateral capsular part of CeA (nociceptive amygdala) receives nociceptive input from brainstem and spinal cord

• Inputs from thalamus and cortex enter lateral and basolateral amygdala

• CeA sends outputs to cortical sites and thalamus, where cognitive and conscious perceptions of pain are integrated

• Descending pain modulation mediated through projections to PAG, which also receives input from hypothalamus, RVM and other medullary nuclei that send descending projections to spinal dorsal horn through the DLF

• Noradrenergic locus coeruleus receives input from PAG, communicates with RVM and sends descending noradrenergic inhibitory projections to spinal cord

• Antinociceptive and pronociptive spinopetal projections from RVM positively and negatively modulate nociceptive inputs and provide an endogenous pain regulatory system

Does a nociceptive stimulus induce predictable levels of pain, and why?

No, it does not induce a predictable response of pain

→ Modulatory signals from CNS alter nociceptive signals, occurring at the dorsal horn or brain where descending modulation pathways modify transmission of the nociceptive signal

What has changed in the modulatory pathways for a person with chronic pain?

The modulatory pathways which are meant to inhibit pain are less active

What is Diffuse Noxious Inhibitory Controls (DNIC)?

A descending inhibitory control system that is triggered by a noxious stimulus that is applied to various parts of the body

→ An applied painful local stimulus becomes less intense after application of the stimulus

→ Suppresses responses of wide dynamic range neurons but not those transmission neurons that respond solely to only one modality (noxious or mechanoreceptive)

What is Diffuse Noxious Inhibitory Controls also referred to as?

Counter-irritation

→ Where one pain can inhibit another

What is the relevance of Diffuse Noxious Inhibitory Controls to chronic pain?

• Chronic pain syndromes believed to be due to loss of DNIC

• Suggests that there are deficits in descending endogenous pain modulation mechanisms

Is it possible to identify a primary pathology for many chronic pain conditions?

It is considered not possible to identify the primary pathology in many chronic pain conditions

Why do treatments for chronic pain run a risk of being unsuccessful?

There is no pain generator, therefore, targeting a particular tissue pathology/injury may not work

What is pain considered as?

A protector against tissue damage, more so than an actual representation of tissue damage

What happens to nociceptive pathways as pain persists?

The pathways become increasingly sensitised (amplified)

What are other possible factors that contribute to persistent pain?

Biopsychosocial or secondary pathologies

What is considered to be the best approach for managing chronic pain?

A biopsychosocial treatment that acknowledges and treats physical, psychological and social factors underpinning pain and disability

Passive treatment alone for chronic pain is NOT the answer? What else would you include in your management for a person with chronic pain?

• Exercise

• Functional rehab

Pain is related to external and internal stimuli. True or false?

True

How is pain related to external and internal stimuli?

These relationships are modulated by sensory inputs, as well as cognitive, emotional and social factors

→ Pain based on context

→ Perception of pain is the brains ‘best guess’ as to the most appropriate behavioural response for pain

What should the clinician determine about a patient with chronic pain?

The patients cues as to what credible evidence there is of danger

What is the goal of treatment for a patient with chronic pain?

Understanding and changing how the patient makes sense of their own pain

→ Make sure they know pain is not necessarily equal to harm

→ Teach them that its okay to move even with some pain

→ Set obtainable goals

This is Pain Education