Spine - Pain

What is pain?

• Does not mean nociception

• Nociception refers to the signal arriving to the brain and being interpreted, pain is the interpretation of that signal

  • Ex. phantom limb pain and gate theory

Pathways

• Pain travels through spinal cord through primary afferent nerve fibers

• Enters through dorsal horn and cross to contralateral side where they ascend through spinothalamic tract

• Enters thalamus, which relays it to the cerebral cortex (sensory cortex) to be perceived (interpret intensity, location, compare to past experiences)

Types of pain

• Nociceptive

• Peripheral neuropathic

• Central sensitization

Nociceptive pain

• Noxious stimuli from tissue damage

  • Chemical (inflammatory)

  • Thermal

  • Mechanical

• Response to inflammation (trauma, degeneration, systemic disease), or ischemia (loading)

  • Altering brain about a potential injury

• Clinical cluster of s&s to differentiate from other types

  • Localized

  • Anatomic in nature

  • Sharp pain provoked by movement

  • Dull ache/throb at rest

• Fiber types

  • A alpha (proprioception)

  • A beta (mechanoreception)

  • A delta (nociception)

  • C fibers (nociception)

• Mechanism/pathway

  • Transduction

    • Noxious receptors detect stimuli

    • Depolarization to action potential

  • Transmission

    • Signal goes from peripheral n. to dorsal horn, then crosses

    • Ascends up spinal tract to brain

  • Modulation

    • While signals pass through spinal cord, they are either dampened or amplified through descending modulation

  • Perception

    • Signals are processed and interpreted in brain (thalamus, cortex, limbic system)

Peripheral neuropathic pain

• Neuropathic pain which comes from damage or disease affecting the peripheral ns

• Results in abnormal cell activity and heightened excitability, most notably from increased firing from voltage gated ion channels

• Responses to both innocuous and noxious stimuli are amplified

• Caused by infection, diabetes, autoimmune disorders, neurotoxic chemicals, and mechanical trauma

• Can present as either spontaneous or stimulus evoked pain

  • 2 types of stimulus evoked pain:

    • Allodynia - pain response coming from stimulus that doesn’t normally induce pain

    • Hyperalgesia - exaggerated pain response from stimulus that would cause mild pain

Central sensitization

• CNS amplification despite minimal/absent peripheral input

• NOT mutually exclusive… overlap of pain types

• Mechanisms

  • Ion channel upregulation

  • Reduced inhibitory control

  • Maladaptive neural plasticity

  • Temporal summation

• Peripheral nociceptive input + persistence over time = mixed pain state

• Hyperexcitable neurons —> hypersensitivity

  • Allodynia

  • Hyperalgesia

  • Expanded receptive field

  • Prolonged pain after stimulus removal

• LBP pts w associated CS

  • Increased severe pain

  • Increased pain related…

    • Depression

    • Disability

    • Anxiety

  • Decreased physical/mental health

• Central sensitivity syndrome = subset of centralized pain disorders

  • Mood/cognition/sleep disorder

  • Fatigue

  • Neuropathic pain (burning, numbness, tingling, paresthesia)

  • Central sensitization inventory (CSI) = screening questionnaire to help identify

Implications for PT

• BPS model suggests everyone is different

• Pain = unique, requires personal plan

• PTs

  • Identify cause

  • Address underlying issues

  • Use multi-faceted approach

  • Educate and empower pts