PAIN

ESAT 3640Therapeutic Modalities

What is Pain?

International Association for the Study of Pain defines pain as “an unpleasant sensory and

emotional experience associated with actual or potential tissue damage, or described in terms such as damage”

http://www.iasp-pain.org/defsopen.html

Pain

Composed of a variety of human discomforts

Not a single entity Perception of pain can be

subjectively modified by past experiences and expectations

We try to change perception of pain

What is the Purpose of Pain?

Warning system Something is wrong, provoking

withdrawal response Can persist beyond its usefulness

Types of Pain

Acute Chronic Referred Radiating

Tissue Sensitivity

Order of sensitivity: 1 – Periosteum and joint capsule

most sensitive 2 – Subchondral bone, tendons, and

ligaments 3 – Muscle and cortical bone 4 – Synovium and articular cartilage

Sensory Receptors Activation of sense organs with

therapeutic agents will decrease perception of pain

4 groups Mechanoreceptors Nociceptors Proprioceptors Thermoreceptors

Meissner’s Corpuscles

Located near the surface at the dermal-epidermal junction

Sensitive to light pressure Mechanoreceptor Produces impulse when stimulus is

increasing or decreasing No impulse with sustained stimulus

Pacinian Corpuscles

Deeper in the subcutaneous tissue Respond to deep pressure Mechanoreceptor Produces impulse when stimulus is

increasing or decreasing No impulse with sustained stimulus

Merkel’s Corpuscles

Located at the dermal–epidermal junction

Touch receptors Sensitive to vertical pressure, not

stretching Mechanoreceptor

Ruffini Corpuscles

In skin sensitive to touch, tension, and heat

In joint capsule and ligaments sensitive to change in position

Mechanoreceptors Proprioceptors Thermoreceptors

Krause’s End Bulbs

Located in skin React to decrease in temperature

and touch Thermoreceptors Mechanoreceptors

Nociceptors

Free nerve endings Sensitive to extreme mechanical,

thermal, or chemical energy Respond to noxious stimuli PAIN Pretty much throughout the body

Muscle Spindles

Bundle of specialized muscle fibers located in muscle

Respond to tension and length when muscle is stretched or contracted

Causes reflexive contraction of muscle Tendon tap

Proprioceptors

Golgi Tendon Organs

Musculotendinous junction Respond to length and tension

changes in muscle Cause relaxation of muscle Proprioceptors

Accommodation

Adaptation by the sensory receptors to various stimuli over an extended period of time

Phasic vs. Tonic receptors Use of physical agents for

extended period of time, may result in accommodation

Neural Transmission

Afferent Nerve fibers that transmit impulses

from the sensory receptors to the CNS Efferent

Nerve fibers that transmit impulses from the CNS to the periphery

Motor neurons

Simple Reflex Arc

Afferent System 1st order neurons

Transmit impulses from sensory receptors to the dorsal horn of the spinal cord

4 types of fibers Alpha () Beta () Delta () C

Afferent System Continued

2nd order neurons Carry sensory information from dorsal

horn to the brain Wide dynamic range or nociceptive

specific 3rd order neurons

Carry information to various brain centers for integration, interpretation, and action response

Synaptic Transmission Neurotransmitter – Passes information

between neurons Neuroactive peptides can facilitate or

inhibit synaptic activity Enkephalin Serotonin Norepinephrine -endorphine Dynorphin

Nociception Nociceptive neurons transmits pain

signals Cell body located in the dorsal root

ganglion Delta fibers = 25%, C fibers = 50% Once stimulated – substance P is

released Size and conduction velocities

different

Fast Pain

Delta neurons Brief, well-localized, & well-

matched to stimulus Originates from receptors in the

skin

Slow pain

C neurons Aching, throbbing, or burning Poorly localized Less specificity to stimulus Originate from both superficial and

deep tissues

Afferent Pathways

Gate Control Theory Pain modulation due to sensory

stimulation and resultant increase in the impulses in the afferent fibers

Stimulation of the substantia gelatinosa (SG)

Stimulation of the SG by fibers inhibit synaptic transmission in the large and small fibers

Ascending Gate Control Theory

and C fiber impulses inhibit SG, facilitating pain perception

Use of physical agents stimulate large-diameter fibers creating analgesic response

Endogenous Opioid Analogue to the Ascending Gate Control Theory

fiber impulses trigger a release of enkephalin from neurons in the dorsal horn

Inhibit synaptic transmission in the and C fibers

Central Biasing Descending pain control Impulses from the

thalamus and brain down the efferent fibers to the dorsal horn

Impulses from the higher centers close the gate and block transmission of pain message at the dorsal horn

Previous experience, emotional influences, sensory perception are factors which can influence transmission of pain

Endogenous Opioid Model of the Descending Pain Control Theory

Stimulation of the periaqueductal grey region and raphe nucleus by ascending inputs activates descending mechanisms

Stimulation of raphe nucleus sends impulses down the efferent fibers in the dorsal lateral tract

Synapse with enkephalin interneurons Release of enkephalin

-Endorphin and Dynorphin Stimulation of small-diameter afferents

stimulates the release of BEP & Dynorphin Prolonged stimulation of the small-

diameter fibers is thought to trigger the release of BEP from the anterior pituitary gland

BEP does not cross blood-brain barrier BEP probably release from area within

brain

Pain Assessment

Pain is difficult to evaluate and quantify Subjective nature Difficult to put into words

Pain Profiles

Type of pain Quantify intensity of pain Effect of pain experience on the

athlete’s level of function Assess psychosocial impact of pain

Pain Assessment Scales Visual analogue scales Pain charts McGill Pain Questionnaire Activity Pattern Indicators Pain Profile Numeric Pain Scale

…Rate your pain on a scale from 1 to 10, with 10 being the worst pain you have every experienced or could imagine

Visual Analogue Scales

Pain Charts

McGill Pain Questionnaire