Pain Neuroscience and Pain Modulation

What is pain?

An emergent conscious experience that serves to evoke a behavioural protective response; subjective; an unpleasant sensory and emotional experience associated with or resembling and actual or potential threat

What is nociception?

Activity in high-threshold primary fibers (A-d and C) and their projections; input that may elicit a variety of responses

Does nociception always mean pain?

No

What is the nature of stimulus for pain?

Physical and/or mental

What pathways are involved in pain?

Ascending and descending 

What factors influence pain?

Biological, psychological, and social

What is the sensory component of pain?

Perception of pain; intensity, quality, location

What is the affective component of pain?

Negative emotion; anxiety, fear, unpleasant sensation

What is the cognitive component of pain?

Interpretation of pain

What is the behavioural component of pain?

Coping strategy used to express, avoid, or control pain

What is the physiological component of pain?

Nociceptive and stress response

What i the fifth vital sign that should be assessed?

Pain

What are the components of pain assessment?

Character, Onset, Location, Duration, Exacerbation, Relief, Radiation

What is character of pain?

Describe pain sensation (sharp, ache, burning)

What is onset of pain?

When did the pain start? Sudden or gradual onset?

What is location of pain?

Where does it hurt? Mark on diagram

What is duration of pain?

How long have you had it? Is it constant or intermittent?

What is exacerbation of pain?

What factors make it worse?

What is relief of pain?

What factors make it better?

What is radiation of pain?

Pattern of shooting/spreading/location of pain away from its origin

What is intensity of pain?

Rate the present pain severity using a pain scale

What is quality of pain?

Description of pain in patient’s own words

What are coping resources?

Prayer, religious practices, withdrawal, meditation, social support

What is variations of pain?

Pain characteristics that change

What are patterns of pain?

Repetitive or not

What are ADL that can be affected by pain?

Sleep, appetite, concentration, school, work, driving, walking, self care

What are associated symptoms of pain?

Nausea/vomiting, dizziness, diarrhea

What are the main risk factors associated with musculoskeletal pain?

Smoking, diet, depression, sedentariness

How does smoking act as a risk factor for musculoskeletal pain?

Increases inflammatory mediators release

How does diet act as a risk factor for musculoskeletal pain?

Increase inflammation

How does depression act as a risk factor for musculoskeletal pain?

Increased suicide risk, increased substance and drug abuse

How does sedentariness act as a risk factor for musculoskeletal pain?

Increased obesity, increased fracture risk, decreased muscle power and strength

What factors influence pain perception?

Age, gender, culture, environment, meaning of pain, anxiety, fatigue, previous experience, family support

How can pain be categorized?

Duration, site of origin, cause, pathogenesis

What is the onset of acute pain?

Sudden, short duration that resolved when tissue heals 

What is the onset of chronic pain?

Insidious onset, persists despite tissue healing

What is the signal of acute pain?

Warning sign of actual or potential damage to tissue

What is the signal of chronic pain?

Not a warning of damage, false alarm

What is the severity of acute pain?

Correlated with amount of damage

What is the severity of chronic pain?

Not correlated with amount of damage

What is the CNS involvement of acute pain?

CNS intact, acute pain is a symptom

What is the CNS involvement of chronic pain?

May be dysfunctional, chronic pain is a disease

What are the psychological effects of acute pain?

Less, but unrelieved pain can cause anxiety and sleeplessness which improves when pain relieves 

What is the psychological effects of chronic pain?

Associated with depression, anger, fear, social withdrawal

Is acute or chronic pain associated with nervous system responses such as hypertension, tachycardia, restlessness, and anxiety?

Acute

Does acute or chronic pain require more drug therapy?

Chronic

How long does tissue healing typically take to occur?

Within 6 months

What is nociceptive/inflammatory pain?

Pain in response to injury or stimuli, typically acute

What is nociplastic pain?

Pain arising from altered nociceptive function, typically chronic

What is neuropathic pain?

Pain that develops when the nervous system is damaged, typically chronic

What is mixed pain?

Primary injury and secondary effects

What are examples of nociceptive/inflammatory pain?

Postoperative, sports injury, sickle cell, arthritis, mechanical low back pain

What are examples of nociplastic pain?

Fibromyalgia, IBS, nonspecific low back pain

What are examples of neuropathic pain?

Postherpetic neuralgia, trigeminal neuralgia, distal polyneuropathy, CRPS, radiculopathy

What are the clinical characteristics of nociceptive pain?

Localized to area of injury, clear mechanical nature to aggravating or easing factors, intermittent, sharp with movement, constant dull ache, no radiating symptoms, no night pain

What are clinical characteristics of peripheral neuropathic pain?

referred in dermatomal or cutaneous pattern, provocation with mechanical nests that load neural tissue, history of nerve injury

What are clinical characteristics of central sensitization/nociplastic pain?

disproportionate, non-mechanical, unpredictable, diffuse, strong association with maladaptive psycho-social factors

What are the 3 types of back pain?

non-mechanical, referred pain, musculoskeletal pathology

What are the stages of pain processing?

Stimulus → transmission along mixed fiber neurons → transmission along spine to brain → perception in brain → descending pathway

What are the peripheral pain modulators?

Histamine, prostglandins, cytokines, bradykinin, substance P

What are the descending neurotransmitters?

Serotonin, norepinephrine, endogenous opiates

What is the role of the premotor cortex?

organize and prepare movements

What is the role of the cingulate cortex?

concentration and focus

What is the role of the prefrontal cortex?

problem solving and memory

What is the role of the amygdala?

fear, conditioning, addiction

What is the role of the sensory cortex?

Sensory discrimination

What is the role of the hypothalamus/thalamus?

stress response, autonomic regulation and motivation

What is the role of the cerebellum?

movement and cognitions

What is the role of the hippocampus?

memory, spatial recognition and fear conditioning

what is the role of the spinal cord?

gate from periphery

How does pain chronification happen?

Persistence of peripheral and/or central painful stimuli → functional sensitization and expanded receptive fields → genetics, inadequate analgesia, or delay in treatment outweight inhibitory modulation → chronic pain

what is maladaptive in chronic pain?

neuropathic component

what central nervous system structures play a role in chronicification of pain?

decreased volume of thalamus, insular cortex, and cingulate cortex, loss of inhibitory interneurons, and sprouting/shrinking of neurons

What are predictors of pain chroniciity within the 1st 6-8 weeks?

Nerve root pain, specific spinal pathology, reported severity of pain at acute stage, belief about pain being work-related, psychological distress, compensation, time off work

What is the consequence of the death of inhibitory neurons?

Decreased ability to inhibit peripheral nociception

What is the consequence of C fibers pulling back and A-B fibers growing in?

Allodynia

What is the consequence of upregulation of second-order neurons?

Increased firing towards the brain, functional shifts in brain-pain matrix

What is the consequence of inappropriate synapsing at wrong level?

Spreading pain

What is the consequence of inappropriate firing at wrong fibers?

Sympathetic, immune, and motor contributions

What is the consequence of inappropriate firing on wrong side?

Bilateral mirror pains

what is the consequence of decreased endogenous mechanisms?

allodynia and hyperalgesia

What is the consequence of altered information from the periphery?

Structural shifts in the brain, homuncular smudging

What is the consequence of alterations in immune function (glial cells)?

Opening of spinal cord-blood barrier

What is the stress to pain cycle?

Chronic stress → nerve sensitization (pain signals sent for things not previously registered as pain), tension (muscle spasms and reduced blood flow cause pain), or chronic conditions (trigger points, IBS, acid reflux, heart conditions develop) → chronic stress

What is chronic pain associated with?

morphological changes in the CNS

What is the endocrine/metabolic response to pain?

Altered release of multiple hormones

Weight loss, fever, increased respiratory rate, shock, and increased blood sugar are examples of a stress response of what system to pain?

Endocrine/metabolic

What is the cardiovascular response to pain?

Increased heart rate, increased vascular resistance , increased blood pressure, increased myocardial oxygen demand, hypercoagulation

Unstable anginal, myocardial infarction, and DVT are examples of a stress response of what system to pain?

Cardiovascular

What is the respiratory response to pain?

Decreased air flow to involuntary and voluntary mechanisms that limit respiratory effort

Atelectasis and pneumonia are examples of a stress response of what system to pain?

respiratory

What is the gastrointestinal response to pain?

Decreased rate of gastric emptying and decreased intestinal motility

Delayed gastric emptying, constipation, anorexia, and ileus are examples of a stress response of what system to pain?

Gastrointestinal

What is the musculoskeletal response to pain?

Muscle spasm and impaired muscle mobility/function

Immobility, weakness, and fatigue are examples of a stress response of what system to pain?

Musculoskeletal

What is the immune response to pain?

Impaired immune function

Infection is an example of a stress response of what system to pain?

Immune 

What is the genitourinary response to pain?

abnormal release of hormones that affect urine output, fluid volume, and electrolyte balance

Decreased urine output, hypertension, and electrolyte disturbances are examples of a stress response of what system to pain?

genitourinary

What is pain modulation?

Any modification of sensory inputs at the levels of sensory processing