International Classification of Pain

An unpleasant sensory AND emotional experience associated w/ actual or potential tissue damage

• The neural process of encoding noxious stimuli
• Consequences of encoding may be autonomic (i.e. elevated BP) or behavioral (motor withdrawal)
• *Pain sensation is not necessarily implied

A stimulus that is damaging or threatens damage to normal tissues

Increased responsiveness of nociceptive neurons to their normal input and/or recruitment of a response to normally sub-threshold inputs

Central Sensitization: increased responsiveness of nociceptive neurons in the CNS to their normal or sub-threshold afferent input

Peripheral Sensitization: increased responsiveness and reduced threshold of nociceptive neurons in the periphery to the stimulation of their receptive fields

• Short duration w/ sudden onset
• Easily diagnosed/treated/resolved
• At/near site of lesion (if referred, in typical referral patterns)

• Starts 3-6 months after injury (lasts 6 months or longer)
• Difficult to diagnose/identify specific cause for pain
• Referred far from site of lesion/atypical referral patterns
• Emergence of illness behaviors not always a physiological sign of warning for the body
• May be related to physiological changes in the nervous system (reduced thresholds, neurotransmitter imbalance, psychological factors, not an identifiable injury)

• Substance abuse/overuse
• Multiple procedures/surgeries 
• External locus of control
• Vegetative signs
• Physical, emotional, sexual abuse
• Exaggerated clinical presentation (verbal or nonverbal pain behavior)

• Personality
• Social Context
• Culture
• Attitudes of Health Professionals
• Past Experience
• State of Mind
• Avoidance and Cognitive Processes

• Assumes an underlying injury
• Remove/alleviate/fix the injury and the pain will go away

• Pain perception due to more than just the injury (psychological state, physiological changes in long standing pain states)
• History of depression --> reduced pain thresholds
• Chronic pain state: receptor sensitivity is heightened
• Treating the inure alone won't address pain perception

• A Delta:
• Small, myelinated
• Speed = mod fast
• Location = capsules, ligaments, fat, blood vessels, connective tissue
• Stimuli = mechanical, thermal 
• Sensation = sharp, prickling sensation, small areas (increased stimulation --> habituation)

• C Polymodal
• Small, unmyelinated
• Speed = slow
• Location = capsules, ligaments, fat, blood vessels, connective tissue
• Stimuli = mechanical, thermal, chemical
• Sensation = dull aching sensation over larger areas (increased stimulation --> sensitization)

• Marginal Zone (I)
• Substantia Gelatinosa (II)
• Nucleus Proprius (III-VI)

"Soup at the dorsal horn" = combination of facility and inhibitory transmitters (mix determines transmission)

Intermediate Gray Matter (VII - VIII)

Anterior Horn Cells (IX)

• Protons (H+, acids)
• Neurotransmitters (serotonin, histamine, ACh)
• Polypeptides (bradykinin, kallidin)
• Prostaglandins
• Cellular metabolites (ATP, ADP, lactic acid, K+)
• Spicy plants (capsaicin)

• Substance P
• Vasoactive Intestinal Peptide (VIP)
• Cholecystokinin
• Somatostatin

One-to-one relationship between the magnitude of the injure and the pain experience (mind and body = distinct entities)

• Treatment aimed at changing behavior
• Pain = unreliable guide
• Education regarding maladaptive pain = paramount
• Graded exercise gradually acclimates the pt to function
• Focus on slow, progressive functional recovery
• Empower the patient
• Use of narcotic pain meds can undermine this process