Chapter Two - Pain and Management Flashcards
There are 3rd order neurons to several areas of the brain. What are their roles?
- Planning
- Sensory discrimination
- Memory
- Emotion
Describe the Gate Control Theory.
Possible brain modulation, not just a passive system• Includes descending pathways
What are endorphins?
Endogenous opioids released within the brain and spinal cord
What is the Neuromatric Theory?
Varied dimensions that overlap to create a unique experience
What are the four components of pain?
Strength of Stimulus - the stronger the stimulus, the less the patient is able to tell where the pain is
Position of the Painful Structure - pain is referred distally
Depth from the Surface - more superficial lesioned tissue, the more precise is its
localizing ability
Nature of the Affected Tissue - nerve root versus peripheral nerve
What is referred pain? Why do we have it?
WHAT: an error in perception by the sensory cortex in the brain as to the source of the painful stimulus (i.e., felt elsewhere than its true site)
WHY: cutaneous, visceral, and skeletal muscle nociceptors converge on a common nerve root of the spinal cord, but brain interprets as cutaneous (higher proportion)
What is the difference between segmental and extrasegmental referred pain?
SEGMENTAL: pain referred to a structure within the same dermatome
EXTRASEGMENTAL: pain referred to >1 dermatome (multiple levelsàsevere)
In one sentence, what is a dermatome?
An area of skin in which sensory nerves derive from a single spinal nerve root
Where does the dermatome project? Where can pain refer alon a dermatome? In what direction, usually?
Projects more distally than the key muscle (myotome)
Dermatome and key muscles develop from the same segment
Any structure within a particular segment can refer pain to the same dermatome of that segment
It may refer along the whole length of the dermatome or only part of it
Pain is generally referred in a distal direction, thus the structure at fault will be located proximal to where the patient feels the pain
What is root pain? Is all root pain referred? Is all referred pain root pain?
Irritation of nerves and nerve roots
Deep, sharp and well localized
All root (radicular) pain is referred, but not all referred pain is root pain
What is acute pain? Give examples. What is its role?
Results from injury or disease that causes, or can cause, tissue damage
E.g., infection, trauma, metabolic disorder progression, degenerative disease
Protects against further tissue damage
Results from injury or disease that causes, or can cause, tissue damage
E.g., infection, trauma, metabolic disorder progression, degenerative disease
Protects against further tissue damage.
What kind of pain is this?
Acute pain
What is subacute pain? What is its purpose?
Similar to acute pain occurring later in the process
Continues to protect against damage
Similar to acute pain occurring later in the process
Continues to protect against damage.
What kind of pain is this?
Subacute pain.
What is chronic pain? What is it associated with? Does it have a role?
Persists beyond the normal time expected for healing of injured tissue
Associated with structural and functional changes in the central nervous system
No longer a symptom or protective
Persists beyond the normal time expected for healing of injured tissue
Associated with structural and functional changes in the central nervous system
No longer a symptom or protective.
What kind if pain is this?
Chronic
Give two kinds of stimulus or source of pain, and one example for each.
Chemical Sources
• Substances that are released with tissue injury (space occupying)
Mechanical Sources
- Normal Stress on Abnormal Tissue
- Ex: movement with a patient just out of a cast
- Abnormal Stress on Normal Tissue
- Not necessary for pathology to be present for pain to be produced
•Ex: bend finger back and hold it
Fill out this graph:
Mechanical pain / Chemical pain
Frequency of pain
Effect of Altered Position or Movement
Quality of the Pain
Heat, Redness and/or Swelling
Effect of Rest
Irritability
Effect of Anti- Inflammatory Meds
Effect of Exercise or Manual Therapy
Mechanical pain / Chemical pain
Frequency of pain : intermittent / constant
Effect of altered position or movement: Pain increases or decreases with certain positions or movements / pain not altered by position or movement (worsens)
Quality of the pain : sudden, sharp twinges / pulsating, throbbing
Heat, redness and or swelling: None/ Common (signs of inflammation)
Effect of rest: Better after prolonged rest/ stiff and sore after prolonged rest
Irritability : Low to moderate / Moderate to high
Effect of anti-inflammatory meds: no effect (need for relief of the mechanism) Better
Effect of exercise or manual therapy: Effective / often not effective (thermal modalities)
How can upregulation and sensitization happend?
- Nociceptive system is usually very quiet
- When injury activates the system, a relatively innocuous stimuli can trigger pain perception
- Events that were not painful before become painful
What is nociceptice pain? What are its characteristics?
Nociceptive pain: normal pain response
• Usually aching or throbbing and well-localized, time limited (resolved once the tissue heals), responds well to analgesics
What is neuropathic pain? What are its characteristics?
- Neuropathic pain: nerve damage (e.g., abnormal firing, increased signal to brain). It is a direct consequence of a lesion or disease affecting the somatosensory system
- Tingling, shock-like or burning pain, usually chronic and responds poorly to conventional analgesics
What is hyperalgia?
Hyperalgesia: increased pain from a stimulus that normally provokes pain
What is allodynia?
Allodynia: pain due to stimulus that does not normally provoke pain
Describe the ectopic impulses theory
Stimulation independent
Neuroma – high density of regenerated nerve endings
Friction between nerves and rigid structures (e.g., musculoskeletal)
Sustained compression
Describe the “response to adjacent nerves” theory. What is the main mechanism called? What are the two ways that this mechanism can happend?
Ephatic-coupling
- A mechanism in which neurons, that would otherwise operate in isolation, communicate via extracellular electrical signals
- Within the same peripheral nerve
Two ways:
Physical Proximity
• Action potentials traveling down a motor nerve can trigger impulses in a sensory nerve, where unmyelinated
Chemical
• Noradrenaline responsive fibres triggered by sympathetic activation
In peripheral sensitization, what is the role of the chemical mediators after a trauma?
Trauma
Inflammatory Response
Chemical Influence on Afferent Neuron Impulse
Describe the reduced reponse threshold pathway of peripheral sensitization.
Chemicals released in response to tissue trauma will bind to ion channels in the membrane to alter permeability and excitability
Indirect influence through 2nd messenger system
(altered pH of the tissue)
Inhibition of after-hyperpolarization
Describe the recruit silent nociceptors pathway of peripheral sensitization.
- A large portion of Ad and C fibers are insensitive in normal, non-injured, non-inflamed tissues
- No firing in ~ 1/3 of nociceptive specific neurons
Injury releases inflammatory mediators to trigger their sensitivity to mechanical stimuli (mediators increase +ve, more and more +ve over time)
Inability to turn off againàchronic pain (simulated tissue damage)
Describe the phenotype change pathway of peripheral sensitization.
- Altered neuron type (nerve -> pain fibre)
- Non-nociceptive to nociceptive
The actual type of afferent nerve can change cellular makeup to become a more painful source
It occurs at the cellular levels
Transcription changes occur within the cell
Stimulation now interpreted as pain
• Once was perceived as light touch/vibration
Describe the chemical property changes pathway of central sensitization.
Chemicals release from nociceptive afferents induce changes in properties of spinal cord neurons
Wide Dynamic Range (WDR) and NS neurons change firing patterns with non-noxious stimuli
NS fire like WDR when central sensitization occurs
Reduced threshold firing, increased rate of firing
WDR: wide dynamic range- tends to be more sensitive because they respond to multiple signals - tends to fire faster
NS: neuro specific neurons
Describe the neuroanatomy reorganiszation pathway of central sensitization.
Reorganization of the cortical sensory map
Sprout nerves to connect to pain pathways
Changes their interpretation
Continual stimulation of Ad and C fibres leads to Aβ fibre changes
Describe the vicious cycle model.
A simple model
An abnormality in structure, posture, movement or stress results in pain that reflexively leads to muscle hyperactivity
Increased sensitivity of muscle spindle afferents
Increased muscle stiffness
Increased muscle metabolite production
• Spasm or fatigueàfurther pain, dysfunction
What is the pain adaptation model?
• More complex – pain does not arise from the muscle itself
Give two examples of self-report pain • Visual Analog Scaleassessments.
- Visual Analog Scale
- Questionnaires
- E.g., McGill Pain Questionnaire (MPQ)
- Select a word to describe pain
- Each word has a separate score
- Includes all dimensions of the pain experience
How do you conduct physiological/quantitative pain assessments (two ways)? Which procedure is more appropriate for which type of neuropathic pain?
Pressure (measure for hyperalgesia)
• Apply pressure against the skin and increase pressure until the individual reports that it is painful
Monofilaments (measure for allodynia)
- Wires with increasing thickness that are pressed against the skin until wire bends
- Greater wire thickness requires greater pressure to bend wire
