2. Pain
Pain is a more
terrible loed of
mankind than even
death itself
Dr. Albert Schweitzer
3. Pain
International Association for the Study of pain
(IASP):
An unpleasant sensory & emotional experience
associated with actulal or potential tissue damage.
This definition emphasizes that....
A) Pain is always unpleasant:
Unlike other sensory input such as smell, which can be
( pleasant, neutral or unpleasant)
4. PAIN
B) Pain is both sensory & emotional experience:
* Individual dosen’t recognize perception of noxious
stimulus without emotional feeling as pain.
* Pain differs from other sensations in that “ it is always
referred to some part of the body with varying degrees of
precision”.
C) Pain is associated with actual or potential tissue
damage:
5. THEORIES OF PAIN
1) Specificity theory... Origin:
The theory was highlighted by Descartes in 1664 and modified by Von Frey
1895. * Descartes explain the pain system as being
like the ( bell - ringing mechanism ) in the church; i.e when someone pulls the rope
to ring the bell, the bell rings in the tower.
- He conceived that, pain is a specific entity similar to the sense of sight or
olfaction.
6. THEORIES OF PAIN
* Von Frey proposed that, specific cutaneous pain
receptors project to a specific pain center in the brain in a
hard - wired system.
- He conceived the pain occurs as follow:
Injury to body tissue ---> damage to nerve fiber-->
stimulation for specific pain receptor & fibers to send
direct message to the specific pain center in the brain-->
pain feeling.
7. THEORIES OF PAIN
Suggestions...
1- there is strong link between pain & injury and the
severity of the injury determines the amount of pain
experienced by the person.
2- peripheral receptors are specialized in their response to
stimuli.
8. THOERIES OF PAIN
Challenges...
1) this theory has defects on anatomical,psychological
& physiological grounds, e.g.: Injuries causing sever
tissue damage don’t always cause pain.
2) it doesn’t explain referred pain triggered off by
stimulation of normal skin.
3) it doesn’t consider the individual deference in how
pain is perceived by people.
9. THEORIES OF PAIN
2)Pattern theory...
This theory proposes that specific nerve fibers or
receptors don’t exist but rather free nerve ending respond
non-selectively to multiple stimuli & their responses took
the form of different patterns of impulses.
* Painful stimuli will be associated with increasing
impulse frequencies.
* Pain is not a separate entity but results from
overstimulation for other primary sensations ( sound,
touch....)
10. THEORIES OF PAIN
Challenges:
not true....
1) Pain has distinct nociceptive afferent pathway (A-
delta & C fibers).
2) Pain intenisty can be reduced while other sensory
modalities are maintained.
3) Intense electrical stimulation to non-nociceptive axons
doesn’t produce pain.
11. THEORIES OF PAIN
3) Gate control theory... ( Melzack & Wall in 1965)
Proposals:
* A modulating ( gating) mechanism exists in the
dorsal horn & involves central neural factors.
* It explains how innocuous stimulation inhibits pain via
a presynaptic inhibitory mechanism.
12. PATHWAY OF PAIN
According to the gate theory:
1) Noxious stimuli from the peripheral nociceptors are
carried to the spinal cord through two types of fibers:-
a- Large myelinated fibers with faster conduction
velocity ( A-beta fibers)
b- Small fibers with slower conduction velocity:
* small myelinated ( A- delta fibers )
* Unmyelinated ( C- fibers )
13. PATHWAY OF PAIN
2) Impulse gating:
* the gating is a neural mechanism that acts like a
modulating or regulating system that control the amount
of nerve impulse transmission from the periphery to the
transmission cells ( T cell)deep in the spinal cord.
3)The projection of pain to the brain:
After the noxious stimuli are modulated in the gate, they
are projected through various pathways to two diffrent
brain areas to be processed....
a- Motivational affective system:
it consists of the reticular formation, limbic system &
hypothalamus.
14. b- Sensory- discriminative system:
noxious stimuli--> spinothalamic & neospinothalamic
projection system --> ventrobasal thalamus -->
somatosensory cortex.
From the IASP definition of pain & the gate control
theory, it is clear that pain is a multidimensional
experience with physical & psychological components.
15. Components of Pain
Melzack &Casey suggests three components comprising
the nature of pain:
1) Sensory - Discriminative.
2) Affective - Emotional.
3) Cognitive - Evaluative.
16. Sensory...
Discrimination of pain in perspective of:
* Time ( days, weeks, months )
* Space ( jaw, head )
* Intensity ( not bad , so bad )
Affective...
Affective responses of feeling:
* Negative responses
* Positive responses
Cognitive...
Significance of pain to the patient.
17. Mechanism of Pain
The classic description of mechanism of pain typically
includes four processes...
1)TRANSDUCTION:
* Definition:
It is the conversion of energy from a noxious stimulus
into electrical signals ( nerve impulse ) by nociceptors.
18. Mechanism of Pain
* Mechanism:
noxious stimulus--> tissue injury--> cells breakdown &
release of their byproducts & inflammatory mediators-->
activation & sensitization of nociceptors.
what is NOCICEPTORS ?
Definition:
Receptors that respond to noxious stimulus or to stimulus
which would become noxious if prolonged.
19. Mechanism of Pain
Location:
Present in most body tissues but notably absent in the
brain.
Type:
Respond to mechanical,thermal or chemical stimuli.
Nature :
They are primary afferent nerve fibers & their
nociception travels along:
20. Mechanism of Pain
1) C-fibers ( unmyelinated-slowly conducting)--> carry
sensation ( dull, aching pain ).
2) A-delta fibers ( myelinated- rapidly conducting)-->
carry sensation ( sharp, localized pain ).
Activation:
They are not spontaneously active , their activation
requires a stimulus over the threshold.
21. Mechanism of Pain
Their activation results in Nociception, which is the
activity that arises in the nerve fiber as a result of
activation of nociceptors.
**Transduction is as follow ( activation ):
Noxious stimulus --> tissue injury --> cells breakdown -->
and release of their byproducts & inflammatory
mediators ( e.g. PG, bradykinin, histamine, &
serotonin)--> these substance will result in:
22. * Activation of nociceptors ( generation of nerve
impulse)
* Sensitization of nociceptors:
- increase excitability
- increase discharge frequency
ADAPTATION:
They are adapted slightly or not at all to the presence
of tissue byproducts & inflammatory mediators ) .
- This explain why pain persists after initial trauma.
23. Mechanism of Pain
2)TRANSMISSION...
* Definition:
Transfer of the neural signals from the site of
transduction ( periphery ) to the spinal cord and brain.
24. Mechanism:
Nociception along the afferent nerve fibers
Dorsal horn cell
Gate
Permission for impulse transmission inhibition for transmission
Impulse transmission at synape from the primary afferent neuron
to second order neuron under the influence of exitatory amino acids
& neuropeptides.
25. Mechanism of Pain
From the dorsal horn cells the impulse are then
transmitted as follow:
* BY spinothalamic tract TO thalamus
* BY spinoreticular tract TO reticular formation
* BY spinomesencephalic tract TO mesencephalon
* BY spinohypothalamic tract TO hypthalamus
29. Mechanism of Pain
3)MODULATION:
It is the descending inhibitory & facilitory input from
the brain that influences or modulates nociceptive
transmission at the level of the spinal cord.
4)PERCEPTION ( awareness of pain ):
* Definition:
It is integration & recognition of signals arriving in the
higher structures as pain. This involve both cortical &
limbic system structures.
30. mechanism of pain
Perception of different types of pain:
Recognition of type & intensity of pain occurs primarily
in the cerebral cortex & differ according to origin.
1) Somatic pain:
The cerebral cortex projects the somatic pain back to the
stimulated area. e.g.: if you burn your finger feel pain in
your finger & not in the cortex.
31. Mechanism of Pain
2)Visceral pain:
The visceral pain doesn’t project back to the stimulated
area but rather, the pain is felt in the skin overlying the
stimulated organ or in a surface area far from the
stimulated organ ( Referred Pain Phenomenon)
The referred phenomenon occurs because the same
segment of the spinal cord innervates the areas to which
the pain is referred as well as the visceral organ involved.
32. Mechanism of Pain
3) Phantom pain:
Pain often experienced by the patients who have had a limb
amputation. *
The reason of this phenomenon is that :
The remaining proximal portions of sensory nerves that
previously received impulses from the limb are stimulated by the
trauma of the amputation & stimuli of these nerves are
interpreted by the brain as pain coming from the nonexistent
limb.
33. Mechanism of Pain
Factors affecting pain perception:
1) Pain threshold...
The point at which the painful stimulus is perceived as
painful, it is variable from one person to another.
2) Pain tolerance...
The amount of pain which the one can endure.also vary
from one to another.
3) Psychological & cultural factors.
34. • Pain Perception:
Transmission of an impulse to
CNS.
• Pain Reaction:
Patient’s reaction (manifestation)
to pain perception.
Pain
Pain Perception and Reaction
35. Pain
Pain Perception and Reaction
Pain
Threshold
PAINNOPAIN
Impulse of equal intensity (all or
none)
Pain threshold is the least intensity of a stimulus that can be
47. Types of Pain
A) According to the PAIN DURATION &
THE CAUSE:
a- Acute ( short time less than one month )
b- Chronic ( 3-6 months or more )
c-Subacute (daily pain for several weeks )
d- Recurrent acute ( several limited pain episodes over
many months)
48. Types of Pain
B) According to the PATHOPHYSIOLOGY:
a- Nociceptive pain:
Normal pain due to normal stimuli in response to
noxious stimuli.
Type: - Physiologic : when acute
- Pathologic : when chronic
b- Neuropathic pain:
Pain in nerve themselves ( neuralgia) caused by
damage to peripheral or central nervous system.
49. Type of Pain
c- Psychological pain:
Pain originates in the mind
No noxious stimulus or abnormality in the nervous
system.felt in many areas as there is no relation between
the pain source & site of pain.
d- Idiopathic pain:
Pain without any identifiable organic lesion.
50. Type of Pain
ACCORDING TO THE ORIGION OF
PAIN:
1) Visceral pain:body viscera or organ
2) Somatic pain: skin, mucous membrane &
subcutaneous tissue)
51. Methods of Pain Control
1)Removal of the cause
2) Blocking the way of painful stimuli : LA action
3) Elimination of pain by cortical depression: GA act
4) Pain control by drugs: Analgesics
5) Non pharmacological:Acupuncture, transcutaneous
electrical nerve stimulation & hypnosis.
52. Methods of Pain Con
1. Removal of the Cause:
Inferior alveolar nerv
53. Methods of Pain Con
2. Blocking the pathway of painful impulses:
Inferior alveolar nerve
54. Methods of Pain Con
2. Blocking the pathway of painful
impulses:
Anesthesia versus analgesia:
Anesthesia
An – No, without
Esthesia – Sensation.
“Absence of all sensation”
55. Methods of Pain Con
2. Blocking the pathway of painful impulses:
Analgesia
An – No, withou
Algesia: pai
“Absence of pain in response to
stimulation that would normally b
painful
58. Methods of Pain Con
4. Pharmacological:
Pain
Free
Pain Threshold
Analgesic
59. Methods of Pain Con
Points to remember:
Stimulus is still present.
Stimulus: beyond threshold = below
threshold.
Pain threshold can be raised to a
limited degree only depending on
the drug used.
60. Methods of Pain Con
5. Non-Pharmacological:
• Acupuncture.
• Hypnosis.
• TENS (Transcutaneous Electric
Nerve Stimulator).
61. Methods of Pain Con
Points to Remember
Pain is an alarm for a potential or actual tissue
damage.
Every effort should be made to diagnose
the source of the pain, and to treat
the pathologic condition rather than the
discomfort alone
