2022 Pain

PAIN THEORY

For a quick review of pain pathways, watch the following:
1. Spinal Cord Tracts and Pathways: https://youtu.be/K-P_BKOUFXs
2. Pain Pathways: https://youtu.be/uOaiaYDoUnA

Pain is one of the most common health problems experienced by older
adults. Between 25% and 50% of all older people living at home, and up to
80% of older people living in nursing homes, report that they are in serious
pain.
Some kinds of pain, such as back pain, seem to decline in frequency as
people get older. Other types, such as large joint pain (pain in the knees,
hip, or feet) may increase. About 12% of older adults have widespread pain,
and pain is reported more often by women than by men.

Commonalities

• Common experience
• Age
• Gender
• Economic status
• “Unfavorable

experience”

Pain has been experienced by everyone regardless of age, gender or economic status.
Pain is usually described as unfavorable experience that has a lasting emotional and
disabling influence on the individual.

Definitions

• Personal experience
• Acute pain
• Chronic pain
• Greater impact on quality of life
• In 1979, the International

Association for the Study of
Pain (IASP) published its first
working definition of pain:

– “An unpleasant sensory and
emotional experience associated
with actual or potential tissue
damage, or described in terms of
such damage”

Bond (1984) describes pain as being a personal and unique experience which arises in
the brain due to injury to the body tissue, disease or due to biochemical changes in our
bodies.

There are two main types of pain, acute and chronic, though there is also fibromyalgia
pain, referred pain, and others.

✓ Acute pain is experienced for a short time and usually has a specific
cause and purpose such as injury to body tissue (Adams and Bromley,
1998)

✓ Chronic pain has no time limit therefore, can last for months and years,
and serves no obvious biological purpose. Chronic pain can have a
significant impact on the quality of person’s life as chronic pain can trigger
psychological as well as physical and emotional problems that leads to
feelings of helplessness and hopelessness as most chronic pain can not
be cured.

In 1979, the International Association for the Study of Pain (IASP) published its first
working definition of pain:

“An unpleasant sensory and emotional experience associated with actual or
potential tissue damage, or described in terms of such damage”.

Reaffirmed in 1994 with the clarification that, pain is always a psychological state that
cannot be reduced to objective signs. In other words, pain is always subjective.

Pain Classifications

• Disease state causing
the pain

• Mechanism of the
pain itself

• Age of the sufferer
• Temporal profile or

duration

Understanding how pain is categorized is critical to providing proper evaluation and
treatment. The classification of pain is not straightforward and there is no one system
universally accepted by clinicians or researcher. As discussed by Gatchel (2004) and
others (Turk and Melzack, 1992), there are many ways that pain can be classified
including:

by the disease state causing the pain or “diagnosis” (e.g., arthritis, cancer,
diabetic neuropathy)
by the mechanism of the pain itself (e.g., neuropathic, musculoskeletal)
by the age of the sufferer (pediatric, pain in the elderly)
by temporal profile or duration (e.g., acute, chronic, recurrent)

Acute Pain

• May indicate tissue
damage

• Protective function
• Associated with tissue

damage
• Of brief duration
• Relationship btw

amount of tissue
damage and pain
experience

Acute pain is usually indicative of tissue damage and most often serves a protective
function for the body signaling potential physical harm. Acute pain can be defined as
follows:

pain that is associated with tissue damage, inflammation, or a disease process.
pain that is of relatively brief duration (e.g., lasting less than 3 to 6 months)

This is the kind of pain that you experience when you cut your finger or stick yourself
with a needle. Other examples of acute pain:

Touching a hot stove or iron: This pain will cause a fast, immediate, intense pain
with an almost simultaneous withdrawal of the body part that is being burned.
You might then experience more of an aching pain that occurs a few seconds
after the initial pain and withdrawal.
Labor pains: The pain during childbirth is acute and the cause is certainly
identifiable
Smashing your finger with a hammer: There is immediate pain, withdrawal and
then “slower” aching pain.

In acute pain there is likely to be a one-to-
one relationship between the amount of
tissue damage and the pain experience. In
addition, the pain will tend to subside in
correlation with tissue healing. Acute pain is
often associated with some anxiety that will
motivate the individual towards adaptive and
self-protective behavior (e.g., resting the
injured body part during tissue healing,
seeking medical attention, etc.).

Acute Recurrent Pain

• Episode of pain
• Pain-free periods

between “flare-up”
• Less than 3 months
• Identified physical

process

In acute recurrent pain the individual suffers from pain episodes with pain-free periods
in between.
The pain episodes are usually brief (e.g., less that 3 months) and associated with an
identifiable physical process (such as migraine headaches, sickle cell anemia, back
sprain, etc.).

Chronic Pain

• Less indicative of tissue
damage

• Occurs past point of
tissue healing

• Lasts more than 3-6 mos
months

• Identifiable cause
• Non-specific
• Due to nerve damage or

nervous system reaction

In contrast to acute pain, chronic pain is usually less indicative of tissue damage and
generally does not serve a protective function for the body. A temporal definition of
chronic pain is as follows:

• pain that occurs past the point of tissue healing or,
• pain that lasts more than 3 to 6 months

As discussed previously, this definition emphasizing the temporal component is not
completely adequate for all types of chronic pain problems. Even so, the psychological
principles of chronic pain assessment and treatment remain the same.
There are at least three types of chronic pain problems:

• chronic pain that is due to a clearly identifiable cause or process,
• chronic pain that is “non-specific” and there is no clearly identifiable pain

generator that explains the pain, and
• chronic pain that is due to some type of nerve damage or abnormal nervous

system reaction.



Chronic Pain & Progressive Disease

• On-going disease
process causing pain

• Cancer
• COPD
• MS

In chronic pain associated with a progressive disease there is an ongoing disease
process that is causing the pain.
This might include such conditions as cancer, COPD, muscle spasm in multiple
sclerosis, etc.
These conditions are often actually categorized by disease state (e.g., cancer pain) and
this dictates special evaluation and treatment approaches.

Neuropathic Pain

• “Nerve pain” or
neuropathy

• Injury or irritation to
nerves-sensory or
motor nerves

• Pain persists
unrelated to injury or
condition

• Chronic pain category

Neuropathic pain has only been investigated relatively recently and seems to involve
some type of direct injury to the nerves. In most types of neuropathic pain, all signs of
the original injury are usually gone and the pain that one feels is unrelated to an
observable injury or condition.

With this type of pain, certain nerves (that have been injured or irritated) continue to
send pain messages to the brain even after the initial tissue damage has healed.

Neuropathic pain (also called nerve pain or neuropathy), is different from pain caused
by an underlying injury.

While it is not completely understood, it is thought that injury to the sensory or motor
nerves in the peripheral nervous system can potentially cause neuropathy.

Neuropathic pain is placed in the chronic pain category but it has a different feel then
chronic pain of a musculoskeletal nature.

Neuropathic Pain Descriptors

• Severe
• Sharp
• Lancinating
• Stabbing
• Ongoing numbness,

tingling, weakness
• CRPS (RSD)
• Post-herpetic neuralgia
• Radiculopathy

Neuropathic pain feels different than musculoskeletal pain, and is often described with
the following terms: severe, sharp, lancinating, lightning-like, stabbing, burning, cold,
and/or ongoing numbness, tingling or weakness.

It may be felt traveling along the nerve path from the spine down to the arms/hands or
legs/feet.

Different types of neuropathic pain conditions include reflex sympathetic dystrophy (or
Complex Regional Pain Syndrome), trigeminal neuralgia, postherpetic neuralgia,
radiculopathy, etc.

Melzack & Wall

• Melzack & Wall
introduced Gate
Control Theory

• Professor at McGill
University, Quebec

• Spurred research into
pain and
electrotherapy

• Theory continues to
evolve

Ronald Melzack is a legend in the field of pain science. Together with Patrick Wall, he
introduced the gate control theory, from which thousands of research studies have
sprung.

Thanks to Melzack, a professor at McGill University in Montreal, Quebec, Canada, our
understanding of the spinal cord physiology and peripheral mechanisms of pain has
exploded.

But as with every great scientist, Melzack has evolved over the past 40 years, and his
theory of pain has evolved with him. We will discuss his newest theory later.

Revised Theory

• Neuromatrix Theory
• Focus should be on

the brain for future
pain research

Melzack spoke before the Second International Congress of Pain) discussing his
description of the recently formulated neuromatrix theory of pain.
The brain should be the focus of the future of pain research.

Historical Precedents:
Specificity Theory

• Descartes 1664
• Direct transmission systems
• 1:1 Relationship
• Periphery to the pain center in

brain
• Nociceptors generate pain

impulse
• Carried by A-delta and C-fibers
• Travel to lateral spinothalamic

tract then to thalamus

Before we discuss the latest theories of pain, let’s identify some pain theories and
historical precedents.

The most common theory purported is known as the Specificity Theory.
Rene Descartes proposed one of the original theories of pain in 1664. His theory
proposed that a specific pain system carried messages directly from pain receptors in
the skin to a pain center in the brain.

The original conceptualization of pain was the specificity theory of pain, in which direct
transmission systems course from the periphery to the pain center in the brain.

Nociceptive receptors generate a pain impulse that is carried by A-delta and C fibers to
the lateral spinothalamic tract and then to the thalamus.

In this model there is a one-to-one relationship between tissue injury and the amount of
pain a person experiences. For instance, if you stick your finger with the needle you
would experience minimal pain; whereas, if you cut your hand with a knife you would
experience much more pain.

Thus, the specificity theory proposes that the intensity of pain is directly related to the
amount of tissue injury.

Specificity Theory

• Surgical intervention was
derived from Descartes
theory

• Pain regarded as a fact of
life.

• Pain was simply regarded
as a fact of life.

• Believed that the pain
women endured during
labor was the spiritual
experience (Porter, 1997)

The treatment of pain by surgical transection of peripheral nerves and/or spinal cord
was derived from this theory.

Pain was simply regarded as a fact of life.

For example, it was thought that the pain women endured during labor was the spiritual
experience that would transform her into a self-sacrificing mother (Porter, 1997)

Specificity Theory

• Pain follows one
fixed pathway
(Jackson, 2002).

• Common
misconception
“mental pain” is
different from
‘physical pain’

Specificity theory was the notion that pain follows one fixed pathway (Jackson, 2002).

Also led to the commonly held misconception even today which recognizes ‘mental
pain’ as being different from ‘physical pain’.

Specificity theory does not explain many types of chronic pain.

Unfortunately, variations on the specificity theory are still taught (or at least emphasized)
in many medical schools and many physicians still ascribe to it in practice.

The theory assumes that if surgery or medication can eliminate the alleged “cause” of
the pain, then the pain will disappear. In chronic pain cases, this is very often not true.

1800’s

• “Age of
Revolutions”

• Discovery of pain
relief

• Opium, morphine,
codeine, cocaine

• Aspirin (sodium
salicylate)

The 1800’s became known as the “age of revolutions” observed scientific
developments, such as the discovery of pain relief.

During this time, they discovered that opium, morphine, codeine, and cocaine could be
used to treat pain.

Felix Hoffmann, a chemist working for Bayer, wished to develop an analgesic to help the
rheumatic pains of his father, devoid of the unpleasant effects of the naturally occurring
analgesic from willow bark: sodium salicylate. He developed aspirin, which to this day is
the most commonly used pain reliever.

20th Century

• Advancements in
medicine

• Custom-designed
drugs to block pain

• Aspirin, NSAIDS,
• Narcotics-

morphine &
codeine

Further developments in almost every area of Medicine, especially pain, with drugs
custom-designed to block specific pain mechanisms and fewer side-effects, emerging.

By the close of the century, several options for pain-relief existed (Arnst, Licking &
Barrett, 1999).

Aspirin was widely prescribed and the, now commonly used, aspirin-like non-steroidal
anti-inflammatory drugs (NSAIDS), such as ibuprofen and Naproxen, had been
introduced for mild to moderate pain.

Narcotics, such as morphine and codeine continue to be prescribed for severe pain.

Revised Thinking

• Dr. Henry Beecher
• Relationship btw

subjective psychological
states and objective drug
response
• Difference btw soldiers
wounded in combat vs.
patients admitted to ER
• No relationship btw
wound severity and
intensity of reported pain

One of the first doctors to question its validity was Dr Henry Beecher, who began his
investigation into relationships between subjective psychological states and objective
drug responses, during his work with severely wounded soldiers in World War II (Ullrich
& Burke, 1999).

He observed that only one out of five soldiers carried into a combat hospital complained
of enough pain to require morphine.

By comparison, when Dr Beecher returned to his practice in the United States following
the war, he noticed that trauma patients with similar wounds to the soldiers were much
more likely to require morphine to control their pain.

He concluded that there was no direct relationship between the severity of the wound
(sensory input) and the intensity of reported pain. Instead he proposed that it was the
meaning associated with the injuries that explained the differences in pain levels.

Beecher’s Findings

• Meaning attached
to the injuries

• Soldier-thankful to
be alive

• Patient-loss of
income, activities

Dr. Beecher concluded that this evidence demonstrated there was not a direct
relationship between the wound and the amount of pain experienced.
He believed the meaning attached to the injuries in the two groups explained the
different levels of pain.
To the soldier, the wound meant thankfulness to escape alive from the battlefield and to
be going home.
Alternatively, the injury to a civilian often meant major surgery, loss of income, loss of
activities, and many other negative consequences.

Phantom Limb Pain

• Discounted
specificity theory

• Sensations occur
in amputated
wound

• Sensations of
intactness or pain

Another finding that discounted the specificity theory was that of phantom limb pain.

Many times patients who undergo the amputation of a limb continue to report
sensations that seem to come from the limb that has been amputated.

This might include feeling that the limb is still there, or it may be a sensation of pain. Of
course, the sensations cannot be actually coming from the limb since it has been
removed from the person’s body.

The specificity theory cannot account for these findings since there is no ongoing tissue
injury in the amputated limb.

Gate Control Theory

• Developed by
Melzack and Wall
(1965)

• Changed
perception of pain

• Explains the
experience of pain
and psychological
factors

A new theory of pain was developed in the early 1960’s that could explain these results.
It is called the gate control theory of pain and it was developed originally by Melzack
and Wall (1965).

The gate control theory changed the way in which pain perception was viewed. The
original theory is very complex and a detailed discussion is beyond the scope of this
presentation.

The gate control theory attempts to explain the experience of pain (including
psychological factors) on a physiological level.

Based upon subsequent challenges and findings, the original gate control theory has
undergone some reformulation and revision but the basic tenets hold true. It has been
able to explain a variety of pain phenomena and has had enormous impact and
stimulated further research (Turk and Flor, 1999).

The gate control theory, wherein large fiber afferents modulate the pain transmission of
the small nociceptive fibers through a gateway, was proposed by Wall and Melzack in
1965.[2]

The substantia gelatinosa in the dorsal horn of the spinal cord was the proposed
location of the gate that modulated the synaptic transmission of nerve impulses from
peripheral fibers to central cells.

This theory foretold the advent of transcutaneous electrical nerve stimulation and spinal
cord stimulation to modulate the transmission of pain in the spinal cord. Other methods
of modulation include psychology and hypnosis.



Gate Theory

• Peripheral nervous
system

• Central nervous
system (spinal cord &
brain)

• Pain peripheral
nerves to spinal cord-
proceed to brain

• Dorsal horn-nerve
gates

In the gate control theory, pain is divided into two components which are processed by
the body separately. These are:

the peripheral nervous system which is outside of the brain and spinal cord, and
the central nervous system which includes the spinal cord and the brain.

Pain messages flow along the peripheral nerves to the spinal cord and proceed to the
brain.

In the spinal cord there are “nerve gates” (in the dorsal horn substantia gelatinosa) that
can inhibit (close) or facilitate (open) nerve impulses going from the body to the brain.

These nerve gates are influenced by a number of factors including the diameter of the
active peripheral fibers converging in the dorsal horns as well as “instructions” coming
down from the brain.

Nerve Activity

• Activity in afferent
large-diameter and
small-diameter fibers
influence spinal gates

• A-beta (lg) inhibit
transmission

• A-delta and C (small)
facilitate transmission
(open gate-more pain

The relative excitatory activity in the afferent large-diameter (myelinated) and small-
diameter (unmyelinated nociceptor) fibers is thought to influence the spinal gates.

The activity in the A-beta (large diameter) is thought to primarily inhibit transmission
(close the gates) whereas the A-delta and C (small diameter) activity are thought to
primarily facilitate transmission (open the gate).

When the gates are more open, a person experiences more pain since the messages
flow freely.

When the gates close, the pain is decreased or may not be experienced at all.

These are important concepts because they explain why various treatments are
effective.

Sensory Nerves

• Sensory nerves carry
information

• Specialized
• A-delta (“fast” pain)
• C-fibers (“slow” or

“continuous” pain)

Sensory nerves bring information to the spinal cord from various parts of the body.
These nerves are specialized to detect: pain, heat, cold, vibration, and touch.

At least two types of small diameter nerve fibers are thought to carry the majority of pain
messages to the spinal cord:

• A-delta nerve fibers carry electrical messages to the spinal cord at
approximately 4 to 44 meters per second (“first” or “fast” pain).

• C-fibers carry electrical messages at approximately .5 to 1 meter per
second to the spinal cord (“slow” or “continuous pain”).

An example of how these
different nerve fibers work is
when you hit your “funny
bone” in your elbow (the
ulnar nerve).
The first sensation is a sharp,
tingling pain followed by a
second sensation of
achiness. At first sensation
there is activation of the A-
delta nerve fibers followed by
the activation of the slower
C-fibers.
The activation of different
nerve fibers can produce
different qualities of pain
sensation.



Modifications

• Pressure and touch-A-
beta fibers (fast)

• Override pain message
of A-delta and C-fibers so
pain message is
decreased

• Less pain
• Accounts for therapeutic

effect of massage, heat,
cold, TENS, Acupuncture

You may have noticed that when you strike your elbow or hit your head, rubbing the
area seems to provide some relief.

This is because you are activating other sensory nerve fibers.

These nerve fibers carry pressure and touch messages to the spinal cord:
These fibers are called “A-beta fibers” and they send their message at
approximately 93 to 103 meters per second.
These speeding messages can reach the spinal cord and brain to override some
of the pain messages carried by the A-delta and C-fibers.

When this overriding occurs, the pain messages are decreased and you experience
less pain.

The action of these differing nerve fibers can explain why many treatments for pain are
effective.

Treatments such as massage, heat, cold, TNS (transcutaneous nerve stimulation), or
acupuncture can change a pain message due to some of these differences in nerve
fibers.

Spinal Cord

• Pain message peripheral
nerves to spinal cord

• Send the message, change
the message, or stop the
message

• Influenced by:
– intensity of message
– competition from incoming
nerves
– signals from brain affecting
priority of message

The pain message travels along the peripheral nervous system until it reaches the
spinal cord. At this point, an extremely complex system can:

Send the message directly to the brain
Change the message being sent to the brain
Stop the message from reaching the brain

As discussed previously, the gate control theory proposes that there are gates on the
bundle of nerve fibers in the spinal cord between the peripheral nerves and the brain.

These spinal nerve gates can either open to allow pain impulses to move freely from the
peripheral nerves to the brain, or they can close to stop the pain signals from reaching
the brain.

Many factors determine how the spinal nerve gates will manage the pain signal
including:

The intensity of the pain message
The competition from other incoming nerve messages (such as touch, vibration,
heat, etc)
Signals from the brain telling the spinal cord to increase or decrease the priority
of certain pain messages.



Brain
Fast Pathways

• Areas of brain stem can
inhibit signal

• Produce endorphins
• Stress, excitement,

vigorous exercise
• Fast pain messages

travel to thalamus and
cortex
• Cortex prompts action to
decrease pain or injury

Once the pain signal reaches the brain, a number of different things can happen.

Certain parts of the brain stem can inhibit or muffle incoming pain signals by the
production of endorphins, which are naturally occurring morphine-like substances.

Stress, excitement, and vigorous exercise are among the things that may stimulate the
production of endorphins.

This is why athletes may not notice the pain of a fairly serious injury until the “big”
game is over.
This is also why regular aerobic exercise can be an excellent method to help
control chronic pain.

In addition, pain messages may be directed along different pathways in the brain. For
instance, a fast pain message is relayed by the spinal cord to specific locations in the
brain: the thalamus and cortex.

A fast pain message reaches the cortex quickly and prompts the individual to take
action to reduce the pain or threat of injury.



Slow Pathway

• Afferent pathways
• Chronic pain-slow pathway
• Pathway to a different portion

of brain, hypothalamus and limbic
system
– Hypothalamus releases stress hormones
– Limbic system where emotions are processed

(why chronic pain associated with stress,
depression, and anxiety)
• Brain also assigns meaning

These are afferent pathways.

Chronic pain moves along a “slow pain” pathway. Slow pain is often perceived as dull,
aching, burning, and cramping.

Initially, slow pain messages travel along the same pathways as the fast pain signals
through the spinal cord. Once they reach the brain, the slow pain messages take a
pathway to a different area of the brain, the hypothalamus and the limbic system.

The hypothalamus is responsible for the release of certain stress hormones in the body
while the limbic system is the area where emotions are processed.

In part, this is one reason why chronic pain is often associated with stress,
depression, and anxiety.
The slow pain signals are actually passing through brain areas that control these
experiences and emotions.

The brain also controls pain messages by attaching meaning to the situation in which
the pain is experienced. This occurs in the cortex, where higher level thinking takes
place.

Soldiers who were wounded in combat displayed much less pain then similarly
wounded civilians who had been involved in a trauma such as a car accident.
The meaning that the brain attached to the situation seemed to be the important
difference.
The brain also gives meaning to the pain signal which also occurs in the cortex.

Depending on how the messages are received and other situational factors, the brain
may pay close attention to the pain signal, or choose to ignore it altogether.

Efferent Pathways

• Descend from brain to
spinal cord

• Opens/closes gate
• Anxiety, stress, may

amplify afferent pain
• Descending, efferent

message can close the
gate
• Occurs in sports,
hypnosis, battle,
distractions

The pain signal is also influenced by efferent neural impulses that descend from the
brain.

In other words, the brain can send signals down the spinal cord to open and close the
nerve gates.

At times of anxiety or stress, the descending messages from the brain may actually
amplify the pain signal at the nerve gate as it moves up the spinal cord.

On the other hand, the descending message from the brain can “close” the nerve gate
in the spinal cord and the message will be stopped at the closed nerve gate (no pain
experienced by the brain).

This can occur in situations such as being in battle, playing competitive sports, being
under hypnosis, being distracted,

Gate Modifiers

• Sensory-physical
being & activities

• Cognitive-related to
thoughts, memories,
interpretations,
predictions

• Emotional-emotions
or feelings

There are a number of other factors that can open or close the pain gates as messages
move up and down the spinal cord. These can be classified into sensory, cognitive, or
emotional areas.

Sensory factors include things that are related to your actual physical being and
activities.

Cognitive factors are those things that are related to your thoughts. This might include
your memories, your interpretation of a current situation, or your predictions about the
future.

Emotional factors are those things related to your emotions or feelings. Emotions are
being happy, sad, mad, or glad.

Factors that Open Pain Gates

• Sensory-injury, inactivity,
drug use, body mechanics,
pacing of activities

• Cognitive-focusing on
pain, outside interests,
worry, thinking bad things

• Emotional-depression,
anger, anxiety, frustration,
hopelessness,
helplessness

Factors that open the pain gates and cause more suffering are:

Sensory factors are such things as
• injury
• inactivity
• long-term narcotic use
• poor body mechanics
• poor pacing of your activities.

Cognitive factors are
• focusing on the pain
• having no outside interests
• worrying about the pain
• remembering bad things associated with the pain
• thinking that your future is a catastrophe.

Emotional factors include
• depression
• anger
• anxiety
• stress
• frustration
• hopelessness,
• helplessness.

Closing the Pain Gate

• Sensory-increasing
activity, pain Rx,
relaxation, meditation,
aerobic exercise

• Cognitive-outside
interests, thoughts,
distraction

• Emotional-positive
attitude, reassurance,
taking control, stress
management

Factors that close the pain gates and cause less suffering are:
Sensory factors can include
• increasing your activity
• short-term use of pain medication
• relaxation training and meditation
• aerobic exercise.

Cognitive factors include
• outside interests
• thoughts that help you cope with the pain
• distracting yourself from the pain.

Emotional factors that can close the pain gates include
• having a positive attitude
• decreasing depression
• being reassured that the pain is not harmful
• taking control of your pain and your life
• stress management.

Acute to Chronic

• On-going pain signals
• Thoughts & emotions
• Pain affected by other

factors than tissue
input

Not all pain that persists will turn into chronic pain.

Pain is experienced very differently for different people. Likewise, the effectiveness of a
particular treatment will often differ from person to person. For example, a particular
medication or injection for a herniated disc may provide effective pain relief for some
people but not for others.

Not all patients with similar conditions develop chronic pain, and it is not understood
why some people will develop chronic pain and others will not.

Also, a condition that appears relatively minor can lead to severe pain, and a serious
condition can be barely painful at all.

As pain moves from the acute phase to the chronic stage, influences of factors other
than tissue damage and injury come into play. Influences other than tissue input
become more important as the pain becomes more chronic.

These include such things as ongoing “pain” signals in the nervous system even
though there is no tissue damage, as well as thoughts and emotions, as
discussed previously. This can be a difficult concept for chronic pain patients to
accept.
A common retort is, “but my pain is real”. All pain is real and physically
experienced.

The gate control theory establishes that pain can be affected by a variety of factors
other than tissue input. After a discussion of the gate control theory patients may be
more open to accepting the idea of psychological pain management treatment.

Pain can generally be divided into acute and chronic phases based upon the length of
time in pain and how fast the tissues are expected to heal.

It is very important to understand that as pain moves from the acute to the chronic
stages, the influences of other factors in the pain system (aside from tissue damage)
come more into play. Gatchel (1991, 1996, 2004) has characterized this progression
from acute to chronic pain as a three-stage model.

This three-stage model can be applied to a number of chronic pain problems, especially
musculoskeletal injuries.

As the pain goes on longer and longer, other factors than just input from the tissue
become important and take priority.

This can be a difficult concept for patients to understand, and common report is, "But I
have real pain." The pain is real and is physically experienced but it is supported and
increased by other factors not just the tissue damage.

Chronic pain and depression are common health problems that we encounter (Currie
and Wang, 2004). There is limited research on chronic pain in the general population,
however. Major depression is thought to be four times greater in people with chronic
back pain than in the general population (Sullivan, Reesor, Mikail & Fisher, 1992).
Research on depression in chronic low back pain patients found rates ranging from 32-
82% of patients showing some type of depressive problem, with an average of 62
percent (Sinel, Deardorff & Goldstein, 1996).

Summary

• Theoretical
framework for pain

• Multi-dimensional
• Genetic, neural-

hormonal mechanism
of stress AND
historical sensory
transmission of pain

We now have a theoretical framework for addressing the issue of pain which involves
the body-self perception, which is modulated by stress system and cognitive brain
functions as well as the historical sensory inputs.

Future research in understanding pain will facilitate continued growth in rehabilitation
and therapeutic techniques.

ASSESSING PAIN

Elements of a Pain Assessment:
Pain History

– Site – Relieving Factors
– Distribution – Impact on ADL
– Quality – Associated Symptoms
– Duration – Onset
– Temporal Factors – Previous Symptoms
– Intensity – Previous Treatment
– Aggravating Factors – Current Treatment

Pain History
The elements of a pain history provide information that can alert to the presence of a serious underlying
condition.

While it is important to note that in the presence of a serious cause for the pain (e.g. fracture), it is not
necessary to obtain a specific patho-anatomic diagnosis to manage acute musculoskeletal pain
effectively.

Completing a good assessment will help with determining an effective treatment intervention. This slide
is a list of areas that should be addressed when conducting an assessment of pain.

Pain History
Site
Distribution
Quality
Duration
Temporal Factors
Intensity
Aggravating Factors
Relieving Factors
Impact on ADL
Associated Symptoms
Onset
Previous Symptoms
Previous Treatment
Current Treatment

Pain History

• Site

– Anatomical
identification

– Referred pain

• Distribution

– Use a drawing such as
the one on the right

Site
The anatomical site where the person feels the pain may or may not be the site of
origin as in the case of referred pain.

The clinician should ask which part hurts the most and whether the pain started
there or elsewhere.

Distribution
The regions in which
pain is felt should be
described.

Even a person who
initially complains of
‘pain all over’ can
usually describe distinct
region(s) of pain
(possibly large and
overlapping).

Having the patient draw
their pain focus and
radiation on a pain
diagram (clarifies its
distribution and can act as a baseline from which to assess response to treatment
and changes in pain patterns).

Pain History

• Quality

– Somatic: deep
– Radicular; sharp or shooting
– Neuropathic: burning
– Visceral: dull

• Duration

– Acute: less than 3 months
– Chronic: longer than 3 months

Quality
The quality of pain may be described in different ways.

Somatic pain is usually deep, dull and aching.
Radicular pain is mostly sharp and ‘electric’ or ‘shooting’.
Neuropathic pain is often ‘burning’.
Visceral pain is dull at first but sharp when lining tissues such as the peritoneum
become involved.

Duration
By convention, pain present for less than three months is described as ‘acute’ pain.

Chronic pain refers to pain present for greater than three months duration.
Pain duration will affect pain management.

Pain History

• Temporal Factors

– Constant or intermittent
– Time of day, activity, duration

• Intensity

– Impact of the experience, not degree of pain
– Good correlation between various types of

assessments

Temporal Factors
Pain may be constant or intermittent.

If pain is constant the history should elicit whether its intensity varies.
If pain is intermittent, the history should elicit its pattern in relation to time of day,
activity and duration.

Intensity
The intensity of pain reflects the impact of the experience, not necessarily the degree of
nociception.
Even though pain is essentially subjective (Merskey and Bogduk 1994) it is important to
assess the intensity of the pain.
Simple tools can be used to assess pain at the initial and follow-up visits to evaluate
progress.

There is good correlation between the various types of scales (Jensen at al. 1986).
The Numerical Rating Scale is suitable for many clinical situations because it is
simple to apply.

PAIN ASSESSMENT TOOLS

Pain History

• Aggravating and Relieving Factors

– Precipitating or worsening pain
– Reduce or abolish pain

• Impact on ADL and Sleep

– Effect of pain on ADL
– Sleep deprivation

• Associated Symptoms

Aggravating and Relieving Factors
Aggravating factors include those that precipitate or worsen pain.
Relieving factors are those that alleviate, reduce or abolish pain.
People who say that nothing eases the pain can be asked about the posture in which
they are least uncomfortable.

Impact on Activities of Daily Living and Sleep
The effects of pain on activities of daily living (ADL) determine associated disabilities
and handicaps (WHO 1986).
Identifying such effects gives the clinician an idea of the impact of pain on the patient’s
lifestyle.
The effect of pain on sleep should be specifically sought; sleep deprivation is a powerful
amplifier of the pain experience.

Associated Symptoms
These include any symptom apparently associated with the painful condition, in contrast
to symptoms associated with other conditions the person may also have.

Pain History

• Onset (Precipitating Event)

– First appearance
– Previous Similar Symptoms

• Previous Action to Relieve Pain

– Treatment successes and failures

• Current Action to Relieve Pain

– All forms of treatment

Onset (Precipitating Event)
The first appearance of the pain and the circumstances in which it started should be
assessed.
The clinician should distinguish between an event that may have aggravated rather than
precipitated the pain.

Previous Similar Symptoms
Previous experience of similar symptoms suggests a recurrent condition.

Previous Action to Relieve Pain
All measures used for the condition before (and their effectiveness) should be noted.
Unwanted effects associated with past treatment should also be recorded.
Information on how each intervention was applied can be helpful, as treatment ‘failures’
may be due to misapplication rather than to true failure of effect.

Current Action to Relieve Pain
All forms of treatment in current use should be noted.
The clinician should ask about the use of physical interventions, including self-applied
measures, all passive treatments, and all substances whether prescribed or otherwise
that the person is taking or applying, with an appraisal of the helpfulness of each.

Pain History

• Social and Occupational History

– Information from a personal, social and
environmental context

• Psychosocial History

– General affect, reaction to pain, fears, coping
strategies

Social and Occupational History
The social and occupational history provides information on the personal, social and
environmental context.
It may include information on

• close relationships
• domicile
• occupation (with details of work tasks)
• present and previous employment
• sources of income
• education
• occupational
• other qualifications and leisure interests.

Psychosocial History
Elicitation of psychosocial history is aimed at understanding the pain (Engel 1977) and
identifying any significant psychosocial issues that may place the person at risk of
developing chronic disability.
The aspects to be explored include:

• general affect
• understanding of and reaction to the painful condition
• associated fears relevant cognitions and beliefs (personal and socio-

cultural)
• coping strategies used in relation to the painful condition.

Pain History

• Past and Current Medical History

– That which has bearing on current situation

• Systems Review

– Review of all body systems that might
contribute to understanding pain.

Past and Current Medical History
The patient’s medical history should be explored and note taken of any condition that
may have a bearing on the pain condition.
All forms of treatment in current use for other conditions should be ascertained and
particular note taken of any that may have a bearing on the pain condition or its
treatment.

Systems Review
Information can be obtained on past or present symptoms from each system of the body
to assess for conditions that may influence the pain condition.