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