2 - Pain and Management Part 2 Flashcards
Where do primary afferent fibers synapse?
The dorsal horn of the spinal cord
Where do 2nd order neurons synapse?
On the thalamus
True or false: Action potentials occur completely or not at all
True
True or false: The stronger the stimulus the stronger the action potential
False, a stimulus needs to be strong enough to depolarize the neuron however, if that stimulus increases in intensity the action potential is still going to occur at the same level.
True or false: a strong stimulation may produce a higher frequency of firing impulses
True
True or false: the stronger the stimulus the easier it is for the patient to tell you where the pain is
False, the stronger the stimulus the less likely the patient is able to tell you where the pain is.
True or false: pain is typically referred proximally
False: pain is typically referred more distally
What are the four conditions for pain?
Strength of the Stimulus
Position of the Painful Structure
Depth from the Surface
Nature of the Affected Tissue
What is referred pain?
it is an error in perception by the sensory cortex.
Wrongly identifies the source of the painful stimulus
Why does referred pain occur?
Because cutaneous, visceral, and skeletal muscle nociceptors converge on a common nerve root of the spinal cord. However, the brain interprets it as cutaneous pain.
Segmental referred pain is when…
Pain is referred to a structure within the same dermatome
Extrasegmental referred pain is when…
Pain is referred to more than one dermatome. Meaning there are multiple levels involved at the spinal cord level.
What is a dermatome?
It is an area of the skin in which sensory nerves derive from a single spinal nerve
What is a myotome?
The key muscle??
True or false: the dermatome and key muscles develop from different segments
False, they develop from the same segment
Define or describe root pain
It is the irritation of nerves and nerve roots. Sensation is deep sharp and well localized.
True or false: all root pain is referred pain but not all referred pain is root pain
True
What are the three types of pain?
Acute Pain
Subacute Pain
Chronic Pain
In what time period would people be considered to have acute pain?
3-6 Weeks
Why would someone be experiencing acute pain?
Due to injury or disease that can cause tissue damage.
Ex. infection, trauma, metabolic disorder progression, degenerative disease.
What does acute pain protect us from?
Further tissue damage
For how long could someone experience subacute pain?
From 6 weeks to 3-6 months
At what point does subacute pain move to chronic pain?
When it is more than 3-6 months
Define or describe chronic pain
When pain persists beyond the normal time expected for healing of injured tissues
It is associated with structural and functional changes in the CNS
Is chronic pain still trying to protect against damage?
No
Define or describe a chemical chemical source of pain
Chemical sources of pain are from substances that are released when a tissue is injured
It occupies the space around the tissue
Define the two different types of mechanical sources of pain
Normal stress on abnormal tissue (ex. movement with a patient who’s just out of a cast)
Abnormal stress on Normal Tissue (ex. bending your finder back and holding it)
True or false: when you place abnormal stress on a normal tissue a pathology must be present in order for the person to feel pain
False, you can place abnormal stress on a normal tissue and still feel pain without a pathology bring present
Mechanical vs. Chemical Pain:
Frequency
Mechanical - Intermittent
Chemical - Constant
Mechanical vs. Chemical Pain: Effect of changing position or movement
Mechanical - pain increases or decreases with certain positions or movements
Chemical - Pain is not altered by change it may actually worsen
Mechanical vs. Chemical Pain: Quality of pain
Mechanical - sudden sharp twinges
Chemical - pulsating or throbbing
Mechanical vs. Chemical Pain: Heat, redness or swelling
Mechanical - none
Chemical - quite common (signs of inflammation)
Mechanical vs. Chemical Pain: Effect of rest
Mechanical - better after prolonged rest
Chemical - stiff and sore after prolonged rest
Mechanical vs. Chemical Pain: Irritability
Mechanical - Low to moderate
Chemical - Moderate to high
Mechanical vs. Chemical Pain: Effect of anti-inflammatory meds
Mechanical - No effect
Chemical - better
Mechanical vs. Chemical Pain: Effects of exercise or manual therapy
Mechanical - effective
Chemical - often not effective
Define or describe sensitization
When a typically non-painful stimulus or a mildly painful stimulus elicits a stronger pain reaction
What are the characteristics of nociceptive pain?
It is a normal pain response. Usually aching or throbbing and is well-localized. Pain usually goes away once tissue is healed and it responds well to analgesics.
What are the characteristics of neuropathic pain?
Stems from having nerve damage (either abnormal firing or an increased signal to the brain). Is usually tingling, shock like, or burning. Usually chronic and responds poorly to analgesics.
What are the two types of neuropathic pain?
Hyperalgesia and Allodynia
What is hyperalgesia
It is increased pain from a stimulus that normally provokes milder pain
What is allodynia?
It is pain due to a stimulus that does not normally provoke pain
What are some issues that affect the brain, spinal cord or peripheral nerves that could lead to neuropathic pain?
Complex Regional Pain Syndrome
Diabetic Neuropathy
Phantom Limb Pain
Post-Stroke
What are the known mechanisms of neuropathic pain?
Ectopic Impulse Generation
Response to Activity in Adjacent Nerves
Changes in Sensitivity
What are four ways ectopic impulses can occur?
They can be stimulated independently
Caused by friction between nerves and rigid structures. Caused by sustained compression
Can also see neuromas with this type or neuropathic pain
What is a neuroma?
It is a high density bundle of regenerated nerve endings
What is another term of response to adjacent nerves in terms of neuropathic pain?
Ephatic coupling
What is Ephatic coupling?
It is a mechanism in which neurons or peripheral nerves that would otherwise operate in isolation communicate via extracellular electrical signals
What two things can trigger ephatic coupling?
Physical Proximity and Chemicals
In terms of ephatic coupling what does physical proximity of motor neurons have to do with it?
When action potentials travel down a motor nerve if it is unmyleniated or if there is damage to the myelination it can trigger impulses in a sensory nerve. For example if there is damage to the insulation in the A-beta fiber then due to the proximity in the C fiber it can trigger an action potential in the C fiber and elicit a pain response
In terms of ephatic coupling what do chemicals have to do with it?
Different chemicals in the body can bind on the surface of the neuron and elicit an action potential which can cause a pain response
What are some sensitivity mechanisms that can elicit neuropathic pain?
Enhanced Mechanosensitivity
Pressure or Stretch
Peripheral Sensitization
Central Sensitization
What is enhanced mechanosensitivity?
it is when increased chemical concentrations are not necessarily enough to illicit activity but they do increase the sensitivity
How do pressure or stretch lead to neuropathic pain?
Pressure or stretch may elicit an action potential in a pain neuron. This is abnormal as these types of stimuli do not normally elicit pain.
What is peripheral sensitization?
It is increased afferent nociceptor input into the CNS
What increases pain signals in peripheral sensitization?
Spontaneous firing which does not require a signal
Could be due to a decrease in threshold to reach to elicit an action potential
Or could be due to increased firing frequency
True or false, peripheral sensitization causes the amount of pain that you feel to be out of proportion to the extent of your injury?
True
What are the three mechanisms of peripheral sensitization?
Reduced response threshold
Recruitment of silent nociceptors
Phenotype change
What is the reduced threshold response?
When there is trauma to a tissue the mechanism that is typically there to prevent a subsequent firing of an action potential is inhibited so the neuron does not fully depolarize and thus a second action potential is sent down the axon and signals continue to be sent more frequently
What does the recruitment of silent nociceptors mean?
When there is an injury the inflammatory mediators trigger their sensitivity to mechanical stimulus (meaning the A-delta and c fibers)
These mediators increase and become more positive over time
Their inability to turn off again leads to chronic pain
What is a phenotype change?
It is an altered neuron type when a nerve fiber can become a pain fiber (ie. non-nociceptive to nociceptive)
Transcription changes occur within the cell and stimulation of this neuron is now interpreted as pain instead of light touch or vibration
What is central sensitization?
It is an aspect of neuroplasticity (when the brain changes with experience)
Describes the changes at a cellular level
It is initiated by high activity levels in the peripheral nociceptors which leads to activity-dependent increases in excitability of nerves in the spinal cord
What are the two mechanisms of central sensitization?
Chemical property changes
Neuroanatomical reorginization
What are chemical property changes?
Two types of cells (WDR and NS) change their firing pattern in response to non-noxious stimuli
This reduces their firing threshold and increases the rate of firing
What is neuroanatomy reorganization?
It is the reorganization of the cortical sensory map in the brain
Nerve sprout to connect to pain pathways this changes their interpretation
So continual stimulation of A-delta and C fibers lead to changes in the A-beta fibers.
Why as clinicians should we be aware of sensitization?
Because the nervous system changes in response to pain (it becomes more sensitive and what may be considered excessive pain behaviours may actually reflect the sensitization of the nociceptive system)
Also need to know that the nervous system changes in response to experience or intervention
What are three types of somatomotor dysfunction?
Enhanced withdrawl reflex
Vicious cycle model
Pain adaptation model
What is somatomotor dysfunction?
It is when central nociceptive neurons synapse with non-nociceptive neurons
Upregulation (prolonged pain) leads to changes in motor behaviour
What is another name for the enhanced withdrawal refex?
A muscle stretch reflex
What is the premis of the enhanced withdrawal reflex?
It is reciprocal inhibition where the agonist muscle is inhibited and the antagonist muscle is activated
What is the vicious cycle method?
Some type of abnormality in structure, posture, movement or stress results in pain that leads to muscle hyperactivity
Then there is an increased sensitivity of muscle spindle afferents which leads to muscle stiffness
This means an increased metabolite production in the muscle which can result in spasm or fatigue and cause further pain and dysfunction which starts the cycle all over again.
Initiating factor - Pain - Reflex - Muscle Hyperactivity - Spasm, fatigue or reinjury - Pain and it continues
What is the pain adaptation model?
In general it is a decrease in the agonist muscle and an increase in activation of the antagonist
This leads to a general reduced max force output of the agonist
As a PT what are the 6 things we cannot note or assume
- We cannot only rely on changes in vital signs
- We cannot decide that a patient doesn’t “look in pain”
- We cannot know how a procedure or disease is “supposed to feel”
- We cannot list the types of pain assuming it will be one of them, we must let the patient tell us
- We cannot assume a sleeping patient does not have pain
- We cannot assume a patient will tell us they are in pain
What is the purpose of a pain assessment?
To diagnose, to help with the prognosis, to help track changes over time and to assist in clinical decision making
What are three types of pain assessments?
Self-reported assessments
Behavioural assessments
Physiological/quantitative sensory assessments
What are some examples of self reported pain assessments?
Visual Analog Scale
Questionnaires (various types)
What are some behavioural observations that would suggest pain?
Bracing
Guarding
Facial grimacing
In what types of poplulations would you expect to see exaggerated pain bahaviours?
Children - paediatrics
The elderly
Patients with cognitive impairments like dementia
What are some examples of physiological or quantitative pain assessments?
Applying pressure (measuring for hyperalgesia) Using monofilaments (measure for allodynia)
True or false: counselling our patients on what drugs to take and how much is within our scope of practice as PT’s?
False
