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What is Chronic Pain?
Lori Montgomery MD CCFPClinical Lecturer, Departments of Family Medicine and Anesthesia
Medical Director, AHS Chronic Pain Centre
Disclosures
Grants/Research Support: NoneSpeakers Bureau/Honoraria: None Consulting Fees: None
290,000 (11.2%) experience chronic pain.
190,000 (7.5%) experience severe chronic pain.
Alberta Health data based on 1996 National Population Health Survey and 2001 Canadian Community Health Survey
Prevalence in Alberta
3–4%
RobinLow back pain for 12 years
Gradual onset
Two low-velocity MVCs, each made pain a bit worse
No red flags
Physical exam: reduced range of motion and strength; neuro exam normal; no radicular signs
RobinVisits you every few weeks,
looking for something to make the pain go away
This visit, Robin is very angry: “Just tell me why my back hurts!”
Pain "an unpleasant sensory and emotional
experience associated with actual or potential tissue damage, or described in terms of such
damage.”
International Association for the Study of Pain
A model of acute painPredictable
Associated with tissue damage
Circuitry well defined
Self limiting
Unimodal treatment
Responds predictably
Useful warning function
BUT
The relationship between injury and pain is NOT 1 to
1
Relationship between Tissue Damage and Pain
Acute injury may not be associated with pain
Henbit, Epsom Derby ,UK
Relationship between Tissue Damage and Pain
Pain may not be associated with acute injury
A model of chronic painUnpredictable
Relationship with tissue damage unclear
Circuitry complex
Continues
Multimodal treatment
Difficult to treat
No useful warning function
PAIN PERCEPTIONThe mind and the body“
Rene Descartes
“spino-thalamic
tract”
Tissue damageInflammationNerve compression
5-HT, Bradykinin, Cytokines,Histamine, Prostaglandins
The Chemistry of Pain
EAAs NMDA receptors SubP / NGF / NK1 / CGRP / NO
Neuronal Plasticity
Descending Excitation /InhibitionDynorphin A /
CCK 5HT / NE / GABA
AttentionExpectation
Affect
Peripheral Sensitization Central
“Explaining Pain”
Pain experienceBalance of input with
modulation
Genetics
Environment
Beliefs
Mood
Social response
See Lorimer Mosely video
Pain is an alarm
Credible evidence
But why does it persist?
Pain Pathways
Firing & WiringFiring & WiringFiring & WiringFiring & WiringFiring & WiringFiring & WiringFiring & WiringFiring & WiringFiring & Wiring
Dirt Road Super Highway
NMDAR
Fibromyalgia: from pathophysiology to therapy, Tobias Schmidt-Wilcke & Daniel J. Clauw, Nature Reviews Rheumatology 7, 518-527 (September 2011)
RobinVisits you every few weeks,
looking for something to make the pain go away
This visit, Robin is very angry: “Just tell me why my back hurts!”
Pain and disability
Model of DisabilityMain & Spanswick
Injury
Pain
Main & Spanswick, 2000
Injury
Pain
Physicaldeconditioning
WithdrawalFrom work
& Soc activities
Reduced physical activities
Main & Spanswick, 2000
1. Development of deconditioning and disuse
Model of DisabilityMain & Spanswick
Guarded movements
and muscle spasm
Injury
PainPateint‘s
(mis)-attributions
Fearavoidance
Main & Spanswick, 2000
1. Development of deconditioning and disuse2. Influence of fear and avoidance
Physicaldeconditioning
WithdrawalFrom work
& Soc activities
Reduced physical activities
Model of DisabilityMain & Spanswick
Guarded movements
and muscle spasm
Injury
PainFocus on
symptoms
Learnedhelplessness(Depression)
Physicaldeconditioning
WithdrawalFrom work
& Soc activities
Pateint‘s(mis)-attributions
Reduced physical activities
Fearavoidance
Main & Spanswick, 2000
1. Development of deconditioning and disuse2. Influence of fear and avoidance3. Influence of depression
Model of DisabilityMain & Spanswick
Guarded movements
and muscle spasm
Injury
PainFocus on
symptoms
Learnedhelplessness(Depression)
Physicaldeconditioning
WithdrawalFrom work
& Soc activities
Pateint‘s(mis)-attributions
Treatment(failed)
Reduced physical activities
Anger,Frustration
Fearavoidance
Main & Spanswick, 2000
1. Development of deconditioning and disuse2. Influence of fear and avoidance3. Influence of depression 4. Influence of anger and frustration
Model of DisabilityMain & Spanswick
Guarded movements
and muscle spasm
Injury
PainFocus on
symptoms
Learnedhelplessness(Depression)
Physicaldeconditioning
WithdrawalFrom work
& Soc activities
Pateint‘s(mis)-attributions
Treatment(failed)
Reduced physical activities
Anger,Frustration
Fearavoidance
Main & Spanswick, 2000
IATROGENICS
1. Development of deconditioning and disuse 2. Influence of fear and avoidance3. Influence of depression4. Influence of anger and frustration5. Influence of iatrogenics
Model of DisabilityMain & Spanswick
Guarded movements
and muscle spasm
Injury
PainFocus on
symptoms
Learnedhelplessness(Depression)
Physicaldeconditioning
WithdrawalFrom work
& Soc activities
Pateint‘s(mis)-attributions
Treatment(failed)
Reduced physical activities
Anger,Frustration
Fearavoidance
Main & Spanswick, 2000
Family
IATROGENICS
1. Development of deconditioning and disuse2. Influence of fear and avoidance3. Influence of depression4. Influence of anger and frustration5. Influence of iatrogenics6. Influence of the family
Model of DisabilityMain & Spanswick
Guarded movements
and muscle spasm
Injury
PainFocus on
symptoms
Learnedhelplessness(Depression)
Physicaldeconditioning
WithdrawalFrom work
& Soc activities
Patient‘s(mis)-attributions
SocioeconomicsLitigation/benefits
Treatment(failed)
Reduced physical activities
Anger,Frustration
Fearavoidance
Main & Spanswick, 2000
Family
IATROGENICS
1. Development of deconditioning and disuse2. Influence of fear and avoidance3. Influence of depression 4. Influence of anger and frustration5. Influence of iatrogenics6. Influence of the family 7. Influence of socioeconomic and occupationalfactors
Model of DisabilityMain & Spanswick
Guarded movements
and muscle spasm