Pathophysiology of Neuropathic Pain

What are the 3 pain buckets?

• Nociceptive

• Nueropathic

• Nociplastic

Describe nociceptive pain

• Tissue is the issue

• Pain localized to area of injury

• Clear & proportionate aggravations & eases

• Intermittent & sharp w/ movement or mechanical provocation

• Dull ache or throb at rest

• NO night pain

• NO burning, shooting, or electric shock

• NO pain w/ other dysesthesias

Describe neuropathic pain

• Nerve is the issue

• Pain in dermatomal pattern

• History of nerve injury, pathology, or mechanical compromise

• Pain w/ NDT (compression, movement, loading)

Describe nociplastic pain

• CNS sensitivity is the issue

• Disproportionate, non-mechanical, & unpredictable pain

• Pain disproportionate to injury or pathology

• Pain/tenderness all over

• Strong association w/ maladaptive psychological factors

What are the 3 types of inflammation?

• Immunoinflammation

• Neurogenic inflammation

• Neuroinflammation

What is immunoinflammation?

• Body’s protective response to harmful stimuli

• Biological response of somatosensory, immune, ANS, & vascular systems

What triggers immunoimflammation?

Direct activation of nociceptors

What are the mechanisms of immunoinflammation?

• Inflammatory mediators

• Prostaglandins, proinflammatory cytokines & chemokines

What is the role of immunoinflammation?

• Healing response & induces threat/danger

• Pain, calor, erythema, edema

• Removes debris & initiates tissue repair

What is neurogenic inflammation?

• Inflammation initiated by release of inflammatory mediators from afferent neurons

• Dorsal root reflex (DRR)

What triggers neurogenic inflammation?

Central release of GABA → anterograde nerve AP due to pain or inflammation related conditions

What are the mechanisms of neurogenic inflammation?

Release of neuropeptides → plasma extravasation & edema

What is the role of neurogenic inflammation?

Plays role in conditions: migraines, CRPS, entrapment neuropathies, asthma, psoriasis

What is neuroinflammation?

Inflammation within the PNS & CNS

What triggers neuroinflammation?

• Injury

• Infection

• Autoimmune disorders

• ND disease

• Toxins

• Aging

What are the mechanisms of neuroinflammation?

Activation of glial cells & infiltration of immune cells

What is the role of neuroinflammation?

• Can be protective or harmful

• Results in sensitization w or w/out neuroplastic changes

What is the primary pain mechanism of an entrapment neuropathy?

Neurogenic

What is the most prevalent type of peripheral neuropathy?

Entrapment neuropathy

What is an entrapment neuropathy?

Result of compression or irritation of peripheral nerve as it transitions through anatomical spaces

What is the onset of an entrapment neuropathy?

Usually slow & chronic

Do all patients with entrapment neuropathies display dermatomal patterns?

NO, 2/3 do NOT

What is extraterritorial spread?

• Sensitization

• Neuroinflammatory reaction via glial cell activation in SC or brain

What are the key components of neuropathic pain?

• Ion channel expression

• Blood flow changes

• Retrograde nerve firing

• DRG

• AP windup

• Immune neuroplasticity

• Multifocal Neuropathy (double crush)