Theories of pain Dr. S. Parthasarathy - PowerPoint Presentation

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Theories of pain

Dr.

S. Parthasarathy

MD., DA., DNB, MD (

Acu

), Dip. Diab., Dip. Software statistics

Phd

( Physiology) CUGRA IDRA

www.painfreepartha.com

FRIDACE - Friday

Anesthesia

Continuing Education

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Introduction

Pain perception, indeed, is a subjective experience, influenced by complex interactions of biological, psychological, and social factors

Some one’s pain is not equal to other

Direct to the topic !!

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Theories of pain !

Intensity Theory

Cartesian Dualistic Theory

Specificity theory

Pattern theory

Epicritic protopathic Gate control theory Neuromatrix model Bio physico social model

“Progress is

not an accident, but a necessity…

It is a part of nature”. (spencer)

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Humor theory ! Sensing organ is the heart !!

Hippocrates and Galen believed that all the illnesses came from the four fluids of the body: the phlegm, the yellow ball, the black ball and the blood.

The flow and reflux of each of the fluids is a response to changes in the body or the environment.

Pain is caused by increased blood viscosity, which stops flowing from each narrow

passage in its path

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Intensity Theory

The theory goes back to the Athenian philosopher

Plato

(c. 428 to 347 B.C.) who in his work

Timaeus

, defined pain not as a unique experience, but as an 'emotion' that occurs when the stimulus is intense and lasting. Touch it ---- but do it with more intensity and for more time !

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There are a lot of deficiencies !

Why should the application of diclofenac relieve pain ?

How a part not involved in the disease or stimulation has pain !!

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Cartesian Dualistic Theory

The dualism theory of pain hypothesized that pain was a mutually exclusive phenomenon.

Pain could be a result of physical injury or psychological injury.

However, the two types of injury did not influence each other, and at no point were they to combine and create a synergistic effect on pain,

Related to soul

Related to pineal gland ! Melatonin now

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Charles Bell (1774–1842), is referred to as the specificity theory

it delineates different types of sensations to different pathways.

It also postulated that the brain was not the homogenous object that Descartes believed it was, but instead a complex structure with various components.

Slowly emerged receptors and pathways !!

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Specificity Theory

Fine

Why should there be pain after the injury healed ?

Why should there be allodynia ?

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Pattern theory - no separate receptors brain senses the pattern of stimulation to find out its touch or pain !

John Paul

Nafe

(1888-1970) presented this theory in 1929. The ideas contained with the pattern theory were directly opposite of the ideas suggested in the Specificity theory in regards to sensation.

Nafe

indicated that there are not separate receptors for each of the four sensory modalities. Instead, he suggested that each sensation relays a specific pattern or sequence of signals to the brain. The brain then takes this pattern and deciphers it

Receptors and pathways identified ? Relevance ?

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Central Summation Theory (Livingstone, 1943)

It proposed that the intense stimulation resulting from the nerve and tissue damage activates fibers that project to internuncial neuron pools within the spinal cord creating abnormal reverberating circuits with self-activating neurons.

Prolonged abnormal activity bombards cells in the spinal cord, and information is projected to the brain for pain perception.

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P

rotopathic and Epicritic theory – 1940s

pain perception often has both protopathic and epicritic aspects,

Epicritic is discrimination – exteroceptive

Protopathic is interoceptive

Only interoceptive is not localized -- example anger

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Sensory Interaction Theory (

Noordenbos

, 1959)

It describes two systems involving transmission of pain: fast and slow system.

The later presumed to conduct somatic and visceral afferents whereas the former was considered to inhibit transmission of the small fibers.

Multisynaptic afferent system

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The Fourth Theory of Pain (Hardy, Wolff, and Goodell, 1940s)

It stated that pain was composed of two components: the perception of pain and the reaction one has towards it.

The reaction was described as a complex

physiopsychological

process involving cognition, past experience, culture and various psychological factors which influence pain perception.

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The three main problems of the previous theories

The CNS response was not accounted

The visceral pain was not accounted

The persistent and chronic pain issues were not addressed

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Gate Control Theory - Melzack Wall – 1960s

According to gate-control theory, pain signals that are

generated at a particular site of injury,

such as the back or shoulder, do not go directly to the brain.

Instead, there is a neurological gate inside the spinal cord that the pain signals encounter.

This gate determines whether or not the signals will be passed to the brain

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SG is the gate !!

PAIN

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Gate control touches the cognitive part of pain

when the signal traveling to the spinal cord reaches a certain level of intensity, the “gate” opens.

Once the gate is open, the signal can travel to the brain where it is processed, and the individual proceeds to feel pain.

The Gate Control Theory was one of the first to acknowledge that psychological factors contributed to pain as well

Depression opens the gate

Unhealthy life style opens the gate ! Negative state of mind opens the gate ! Cortical control

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Headache or backache !!

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When we get itching, we scratch – itch goes through pain pathways !!

Scratching

The gate control theory, however, is not able to explain several chronic pain problems, such as phantom limb pain, which require a greater understanding of brain mechanisms

.

Itching

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Interaction between A beta and A delta

Acute pain

Touch sensation is sensed more

Chronic pain

Touch sensation is sensed less !

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Descending pain modulation

Descending pain modulation encompasses 

pathways that descend from the forebrain and brainstem to the spinal cord and trigeminal sensory complex to modify incoming somatosensory information

 so that the perception of and reactions to somatosensory stimuli are altered, resulting in either less or more pain.

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Neuromatrix Model – 1990s – Ronald

Melzack

!

the central nervous system that is responsible for eliciting painful sensations rather than the periphery.

The

neuromatrix model denotes that there are components within the central nervous system responsible for creating pain. The components are the “body-self neuromatrix, the cyclic processing, and synthesis of signals, the sentinel neural hub, and the activation of the neuromatrix.”

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What is the neuromatrix – how does it work ?

Neuromatrix

consists of multiple areas within the central nervous system - brain thalamus, limbic system, prefrontal areas Spinal Cord etc.

These areas work together to produce a pain signature !

Neurosignature

makes one to feel pain

Only peripheral signals alone

cannot

elicit

pain signature !

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Thermal stimulation increased blood flow in many areas of the brain !!

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Neuromatrix Model

allows for memory formation of these particular experiences. If the same circumstances occur again in the future, it is this memory that allows for the same sensation to be felt

established the idea that pain gets influenced by cognitive and emotional factors as well as physical factors,

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See the inputs !

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Neuromatrix theory !! ??

It explains why some non pharmacological methods help

It throws light on

labour

pain relief methods and their effects

But why each individual’s experience with pain is unique ?it still fails to account for social constructs of pain.

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Homeostatic theory

Rather than seeing pain as part of the exteroceptive sense of touch, Bud Craig suggests that pain is a homeostatic signal , based on neuroanatomical and neurophysiological demonstrations.

Pain perception is then both a distinct sensation and a motivation at the same time.

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Biopsychosocial Model – its just viewpoints !

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Physico psycho social !!

There must be something to address social factors especially in chronic pain syndromes

John

B

onica

( Father of pain) – found it difficult to treat pain of injuries and war trauma!

pain is the result of complex interactions between biological, psychological and sociological factors

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Patient with HIV

Neuropathy and pain

bio

Depression and mental agony

Psycho

He or she will be treated as a social outcast What are the social influences of pain !

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Malignancy

Cancer cervix with infiltration

Tissue damage and pain

BIO

Severe depression

Psycho Does the pain be influenced by his residence in an apartment in Mumbai Or a small house in vadugapatti !

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What are special about biopsycho social approach

This model has been proven to have superior outcomes in terms of increased patient satisfaction and a better degree of restoration of functionality.

more cost-effective method

Uniqueness explained

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Why do we need such models ?

Assessment

Interprofessional approach

Management – cure or treat – disease or illness ?

Maximizing functionality

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PHN and capsaicin ointment

Gate control theory

New 8 % capsaicin

High concentrations of capsaicin or repeated applications can produce a persistent local effect on cutaneous nociceptors, which is best described as

defunctionalization

and constituted by reduced spontaneous activity and a loss of responsiveness to a wide range of sensory stimuli.

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Summary

Intensity Theory

Cartesian Dualistic Theory

Specificity theory

Pattern theory

Epicritic protopathic Gate control theory Neuromatrix model Biophysicosocial model

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www.painfreepartha.com

So many theories

So many explanations ,mean what ?

We have not understood enough

Thank you all