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Pain is subjective. Self-experience Experience depends on circumstances Pain can cause many different reactions: Activate autonomic system (heart rate, blood pressure, sweating, etc.) Muscle activity Mood (fear, anxiety, depression) Prevent sleep.

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pain is subjective
Pain is subjective
  • Self-experience
  • Experience depends on circumstances
  • Pain can cause many different reactions:
    • Activate autonomic system (heart rate, blood pressure, sweating, etc.)
    • Muscle activity
    • Mood (fear, anxiety, depression)
    • Prevent sleep
pain occurs with different degrees of severity
Pain occurs with different degrees of severity
  •   Mild pain:

Does not interfere noticeably with everyday life

  • Moderate pain:

May cause some annoyance and perceived as unpleasant

  • Severe chronic pain:

Affects a person’s entire life in major ways

there are many forms of pain

There are many forms of pain

Mild pain:

Does not interfere noticeably with everyday life

Moderate pain:

May cause some annoyance and may be perceived as unpleasant

Severe pain:

Affects a person’s entire life in major ways

different forms of pain
Different forms of pain
  • Acute pain
  • Chronic pain
  • Somatic pain
  • Neuropathic pain
  • Central neuropathic pain
pain has many different forms but the same name tinnitus has many different forms but the same name
Pain has many different forms, but the same name Tinnitus has many different forms but the same name
there are different types of pain
There are different types of pain
  • Somatic and visceral pain (Stimulation of nociceptors)
    • Pain ceases when stimulation ceases
  • Neuropathic pain
    • Pain is related to the nervous system
  • Central neuropathic pain
    • Plastic changes in the function of the CNS
    • May be persistent
it is important to have different names for for different disorders
It is important to have different names for for different disorders
  • We cannot think about matters that do not have names
  • The same words is used to describe very different forms of tinnitus and pain
  • Using the same names for fundamentally different disorders is a disadvantage in studying and treating such disorders
severe pain affects a person s entire life in major ways
Severe pain affects a person’s entire life in major ways
  • Prevent or disturb sleep
  • Interfere with or prevents intellectual work 
  • May cause suicide

May involve limbic structures causing affective reactions

Often accompanied by abnormal sensations from touch

how prevalent is severe pain

How prevalent is severe pain?

Some pain was reported by 86% of individuals above the age of 65

(Iowa study, 1994)

The prevalence of severe pain was 33% for people at age 77 and above (Swedish study, 1996)

how prevalent is severe pain1

How prevalent is severe pain?

Some pain was reported by 86% of individuals above the age of 65

(Iowa study, 1994)

The prevalence of severe pain was 33% for people at age 77 and above (Swedish study, 1996)

slide11

Pain

“The only tolerable pain is someone else’s pain”

René Leriche, French surgeon, 1879–1955

there are different types of pain1
There are different types of pain
  • Somatic and visceral pain (Stimulation of nociceptors)
    • Pain ceases when stimulation ceases
  • Neuropathic pain
    • Pain is related to the nervous system
  • Central neuropathic pain
    • Plastic changes in the function of the CNS
    • May be persistent
slide14
Central neuropathic pain:
    • Pain sensation caused by abnormal neural activity in the CNS
  • Hyperacusis:
    • Sounds are perceived louder than normal
  • Allodynia:
    • Sensation of pain from normally innocuous stimulation (such as light touch)
  • Hyperpathia:
    • Exaggerated and prolonged reactions to painful stimuli
somatic and visceral pain stimulation of nociceptors
Somatic and visceral pain (Stimulation of nociceptors)  
  • Burning (temperature)
  • Injury
  • Inflammation
  • Chemicals
  • Compression of spinal nerve roots (nervi nervorum)
slide17

Relationship between commonly used terms to characterize

muscle tension:

Tone, stiffness, contracture, and spasm

slide18

Tension type headaches

with trigger zones in

the temporalis muscle (),

in suboccipital,

sternocleidomastoid

and upper trapezius

muscles (), from where

pain attacks can be elicited

neuropathic pain
Neuropathic pain
  • Pain of the nervous system
  • Neuralgias
  • Anesthesia dolorosa
  • Root pain
  • Stroke pain
neuropathic pain1
Neuropathic pain
  • All pain of neural origin

The term is mostly used by neurologists for pain caused by disorders of peripheral nerves and cranial nerves

central neuropathic pain
Central neuropathic pain
  • Plastic changes in the function of the CNS(WDR neurons, thalamus)
acute pain may promote development of central neuropathic pain
Acute pain may promote development of central neuropathic pain
  • Central neuropathic pain is a neurologic disorder
acute pain sensation may not be a sign of pathology
Acute pain sensation may not be a sign of pathology

Pain sensation can be elicited by:

  • Stimulation of nociceptors
  • Overstimulation of other receptors
acute pain has two phases a fast sharp and a slow burning sensation
Acute pain has two phases: A fast (sharp) and a slow (burning) sensation
  • The slow and delayed pain is mediated by unmyelinated fibers (C-fibers).
  • The fast phase is mediated by myelinated fibers (A).
fast and slow pain are different
Fast and slow pain are different
  • Fast pain (stinging):
    • Well defined with regards to location
    • Its strength is defined
  • Slow pain (aching):
    • Diffuse, poorly localized anatomically
    • Difficult the estimate its strength
temperature
Temperature

There are four different temperature receptors:

Cool and warmth (sensory receptors)

Cold and heat (nociceptors)

temperature1
Temperature
  • Cool and warmth receptors mediate sensation of temperature
  • Cold and heat receptors are nociceptors that mediate sensation of pain.
  • Cool and warmth receptors are innervated by small myelinated (A fibers, diameter 1-5 m, conduction velocity 5-30 m/sec).
  • Cold and heat receptor are innervated by unmyelinated fibers (C-fibers, diameter 0.2-2 m; conduction velocity 0.5-1 m/sec).
slide37

Wide dynamic

range neuron

the anterior lateral system mediates pain sensations

THE ANTERIOR LATERAL SYSTEM MEDIATES PAIN SENSATIONS

The spinothalamic tract is the best known of the anteriorlateral tracts

slide42

Ascending projections of

the anterior portion

of the STT from neurons

in lamina IV-V of the

spinal horn.

VPI: Ventral posterior

inferior (nuclei of thalamus);

VPL: Ventral posterior

lateral (nuclei of thalamus);

SI: Primary

somatosensory cortex;

SII: secondary

somatosensory cortex

slide43

Projections of the

lateral portion of

the STT from cells

in lamina I of the

dorsal horn

slide44

Projection of

unmyelinated C fibers.

Notice: Projection

to SII is bilateral

but only the SI

receives input

from C fibers

slide47

Pathways involved

in mediating the

sensation of

nociceptor pain

slide48

Input to the

periaquaductal gray

(PAG) and

pathways that modulate

transmission of pain

signals by the PAG

through the rostral

ventromedial medulla

(RVM) pathway.

slide49

Dorsolateral

pontomesencephalic

tegmentum pathway (DLTP).

slide51

Innervation by the

vagus nerve of organs

in the lower abdomen

involving the nucleus

of the solitary tract (NST)

slide52

DLF: Dorsolateral funiculus

VLF: Ventrolateral funiculus

RVM: Rostroventral medulla

visceral pain is different from somatic pain
Visceral pain is different from somatic pain
  • Inconsistent sensations
  • Sometimes referred pain to body surface
  • Often inescapable
slide55

Two-way connections

between PAG, DLPT

and RVM

and their connections

to the dorsal horn

slide58

Hypothesis about expansion of receptive field and creation of

trigger points by unmasking of dormant synapses

slide59

Mean EMG amplitudes recorded from a muscle

at a trigger point and at an adjacent

non-tender muscle

slide60
Itch
  • The basis of itching is poorly understood but it has similarities with pain.
central neuropathic pain may involve the sympathetic nervous system
CENTRAL NEUROPATHIC PAIN MAY INVOLVE THE SYMPATHETIC NERVOUS SYSTEM
  • REFLEX SYMPATHETIC DYSTROPHY, RSD
role of sympathetic nervous system in neuropathic pain
Role of sympathetic nervous system in neuropathic pain
  • Sympathetic system is activated by stimulation of pain fibers
  • Sympathetic fibers secrete nor-epinephrine near mechanoreceptors
  • Sensitivity of mechanoreceptors increases
  • Activation of sympathetic system increases
  • Result: A viscous circle that causes RSD
slide64

Trauma cause activation of pain fibers (C-fibers), which sensitize WDR neurons

Sensitized WDR neurons cause pressure to activate pain circuits (allodynia)

Mechanoreceptors are activated by epinephrine that is secreted from sympathetic nerves in absence of mechanical stimulation

slide65

Contemporary hypotheses of neural mechanisms involved

in generating CRPS I and II following trauma

CRPS: Complex regional pain syndrome

neuropathic pain2
Neuropathic pain
  • Pain of the nervous system
  • Neuralgias
  • Anesthesia dolorosa
  • Root pain
  • Stroke pain
central neuropathic pain1
Central neuropathic pain
  • Plastic changes in the function of the CNS(WDR neurons, thalamus)
central neuropathic pain2
Central neuropathic pain
  • All pain of neural origin

The term is mostly used for pain caused by disorders of peripheral nerves and cranial nerves

central neuropathic pain may be caused by
Central neuropathic pain may be caused by:
  • Chronic inflammation
  • Sensitization of skin receptors
  • Changes in the connectivity of the CNS (through neural plasticity)
acute pain may promote development of central neuropathic pain1
Acute pain may promote development of central neuropathic pain
  • Central neuropathic pain is a neurologic disorder
slide71

Wide dynamic

range neurons

central neuropathic pain may develop from peripheral nerve injuries
Central neuropathic pain may develop from peripheral nerve injuries
  • The pain is referred to the peripheral location
  • Treatment of that location will not help
  • The patient and the surgeon are both frustrated
central neuropathic pain may involve changes in function
Central neuropathic pain may involve changes in function
  • Normally innocuous stimulation becomes painful (allodynia)
  • Stimuli that normally cause mild pain cause an exaggerated reaction (hyperpathia)
central neuropathic pain is often accompanied by altered perception of touch and pain stimuli
Central neuropathic pain is often accompanied by altered perception of touch and pain stimuli
  • Touch may cause pain (allodynia)
  • Increased sensitivity to pain (hyperalgesia)
  • Painful stimulation may cause exaggerated reaction to pain and prolonged pain (hyperpathia)
central neuropathic pain may involve changes in function1
Central neuropathic pain may involve changes in function
  • Normally innocuous stimulation becomes painful (allodynia)
  • Stimuli that normally cause mild pain cause an exaggerated reaction (hyperpathia)
slide76

Allodynia: Pain from normally innocuous stimulation (of the skin)Hyperalgesia: Extreme sensitiveness to painful stimuli.Hyperpathia: Exaggerated subjective response to painful stimuli, with a continuing sensation of pain after the stimulation has ceased.

slide77

Temporal integration

Neuropathic pain

Normal

Pain

Tingling

From: Møller and Pinkerton, 1997

slide78

Temporal integration during development of

carpal tunnel syndrome

A

B

From: Møller and Pinkerton, 1997

slide80

Hypothesis for referred pain and

sensitization of different nociceptors

sensitization
Sensitization
  • Peripherally:
    • Receptors
  • Centrally
    • Increased synaptic efficacy
    • Expression of new neurotransmitters
    • Neuromodulators
    • Morphological re-organization
other phenomena associated with chronic pain
“Wind-up”

Response to second stimulus is stronger than the response to the first one

Change in temporal integration

Other phenomena associated with chronic pain

From: Møller: Sensory Systems, 2002

slide83

"Wind-up" is NMDA mediated.

Response with and without an NMDA antagonist.

severe neuropathic pain affects a person s entire life in major ways
Severe neuropathic pain affects a person’s entire life in major ways
  • Prevent or disturb sleep
  • Interfere with or prevent
  • Intellectual work 

Involve limbic structures causing affective reactions

how do we explain these symptoms and signs physiologically and anatomically

How do we explain these symptoms and signs physiologically and anatomically?

Where is the neural activity that give a sensation of pain generated?

slide86
The anatomical location of the abnormality that cause pain may be different from that to which the pain is referred
  • Referred pain
  • Central neuropathic pain
slide87
The abnormal neural activity that causes symptoms are not generated at the location where the symptoms are felt

Example:

  • Posttraumatic central neuropathic pain
  • Phantom pain
central pain pathways for pain
Central pain pathways for pain
  • PROJECT TO PRIMARY CORTICES WITH SPATIAL INFORMATION (“WHERE”)
  • PROJECT OBJECTIVE INFORMATION (“WHAT”) TO MANY DIFFERENT PARTS OF THE CNS.
  • NON-CLASSICAL PATHWAYS ALSO CONTRIBUTES TO AROUSAL
slide89

SUMMARY OF PATHWAYS INVOLVED IN MEDIATING THE SENSATION OF PAIN

CENTRAL PAIN PATHWAYS PROJECT TO PRIMARY CORTICES WITH SPATIAL INFORMATION (“WHERE”)

OBJECTIVE INFORMATION (“WHAT”) TO MANY DIFFERENT PARTS OF THE CNS (FOR EXAMPLE THE AMYGDALA)

NON-CLASSICAL INFORMATION ALSO CONTRIBUTES TO AROUSAL

From: Møller: Sensory Systems, 2003

reversal of neural plasticity
Reversal of neural plasticity
  • “TENS” (transderm electric nerve stimulation) has been used for many years in treatment of chronic pain
  • Recently, sound stimulation in various forms have been introduced in treatment of severe tinnitus
severe neuropathic pain affects a person s entire life in major ways1
Severe neuropathic pain affects a person’s entire life in major ways
  • Prevent or disturb sleep
  • Interfere with or prevent
  • Intellectual work 

Involve limbic structures causing affective reactions

how can pain information reach the amygdala
How can pain information reach the amygdala?
  • Through the thalamus
  • Through routes that are enhanced by expression of neural plasticity (re-routing of information)
slide93

Connections from a sensory system to the amygdala

“the high route”

From: Møller: Sensory Systems, 2003

slide94

Connections from a sensory system to the amygdala

“the low route”

From: Møller: Sensory Systems, 2003

slide96

Connections from the amygdala

From: Møller: Sensory Systems, 2003

inescapable pain involves other parts of the cns than escapable pain

INESCAPABLE PAIN INVOLVES OTHER PARTS OF THE CNS THAN ESCAPABLE PAIN

Activate different columns in the PAG coordinating either active of passive coping