Chronic Pain Flashcards
What is acute pain?
Sudden onset of pain in response to injury, infection
Resolves as the underlying cause resolves
What is the difference between recurrent acute pain and chronic pain?
Recurrent acute pain is lots of minor attacks of the body causing pain
Chronic pain is pain that persists after the stimulus/cause has resolved
What is meant by chronic neuropathic pain?
A neurological condition
That results from damage to, or dysfunction of the sensory nervous system
The pain persists in absence of tissue damage
Neuropathic vs nociceptive?
Nociceptive: pain caused by trauma to tissues, activation of nociceptors
Neuropathic: pain caused by damage to the sensory nervous system
What is neurogenic pain?
Pain caused by damage/dysfunction of the peripheral nervous system
What are some causes of chronic neuropathic pain?
Trauma Post-operative Viral Diabetes Unknown cause
What type of pain is chronic neuropathic pain? I.e. what does it feel like?
Burning: hot and cold sensations
Electric shocks, shooting pain
Deep, achy
Poorly localised, may be in a dermatomal pattern
Numbness, paraesthesia
Hypersensitive skin
Worse at night, or when not distracted
What type of pattern/distribution is chronic neuropathic pain seen in?
Dermatomal patterns often
For the patient it feels poorly localised
What is a dermatome?
The region of skin supplied by a particular spinal nerve root
Briefly explain what is meant by ‘illness behaviour’?
The fact that people respond differently to pain and illness
Some people feel pain more than others
A lot of it depends on upbringing, environment, culture
What type of people are at risk of suffering from chronic neuropathic pain?
Work pressures
People going through litigation, benefit, claim processes
Poor social circumstances
Lack of family support
Why does pain persist to become chronic neuropathic pain in some people?
Poorly understood
We think, that there is increased afferent activity or synaptic transmission at the affected level of the spinal cord
What are C fibres?
Small, afferent, unmyelinated nerve fibre
Involved in the transmission of pain from the peripheries to the CNS
Are C fibres high or low velocity conductors?
Slow, since they are unmyelinated and have a small diameter
What is the difference between afferent and efferent?
Afferent: transmission from peripheries TO the CNS
Efferent: transmission FROM the CNS to the peripheries
Remember latin:
Ad = to, towards
E, ex = of, from
Describe the journey of a pain impulse from the nociceptor to the brain?
Nociceptor is activated
Pain impulse travels from nociceptor along C (or other similar) fibre
Enters the spinal cord
Synapses with a second order neuron in the dorsal horn, substantia gelatinosa
Impulse travels up spinothalamic tract to the brain, via the thalamus
Which part of the spinal cord is involved in the transmission of pain impulses?
The substantia gelatinosa
Found in the dorsal horn of the spinal cord
What neurotransmitter is involved in the transmission of a pain impulse from the C fibre to the second order neuron in the substantia gelatinosa?
Substance P
Is the neurotransmitter for the synapse of pain fibres in the substantia gelatinosa
What is neuralgia?
Intense intermittent pain along the course of a nerve
E.g. trigeminal neuralgia
What is neuropathy?
Damage, dysfunction of a peripheral nerve, resulting in weakness or numbness
What is hyperalgesia?
Abnormally heightened sensitivity to pain
What is causalgia?
Severe pain in a limb caused by injury to a peripheral nerve
What is hyperpathia?
Activation of nociceptors evokes exaggerated levels of pain
What is allodynia?
When normal, non-painful stimuli evoke pain
What is lumbago?
Pain of the muscles and joints of the lower back
Investigation of a patient with chronic pain?
History:
- other medical conditions
- history of trauma, anything that could have triggered
- SOCRATES
Examination:
- of pain
- neurological exam
X-rays, MRI of spine
Serology
What does SOCRATES stand for?
Site
Onset: when, sudden/gradual
Character: ache, stabbing
Radiation
Associations: any other problems associated with the pain
Time course: diurnal?
Exacerbating / relieving factors
Severity: scale of 1-10
Management of patient with chronic pain?
Counselling, CBT to improve state of mind
Pain management program: agreed objectives
Explanation that there is no damage occurring, and encourage exercise
Drug treatment
Other treatments
What drugs are used to treat chronic neuropathic pain?
Weak and moderate strength
Anti-depressants: tricyclic + SSRIs
Anti-convulsants
N-methyl D-aspartate receptor antagonists
How do anti-convulsants help treat chronic neuropathic pain?
They dampen down excitation of neurons
Reducing the transmission of pain impulses
What is N-methyl D-aspartate?
A chemical involved in pain transmission
Involved in presynaptic excitation where C fibres synapse with second order fibres (in the substantia gelatinosa)
Inhibiting it can reduce pain
How do N-methyl D-aspartate receptor antagonists help treat chronic neuropathic pain?
N-methyl D-aspartate is involved in presynaptic excitation of the synapse where C fibres and second order fibres meet in the s. gelatinosa
Inhibiting its action will inhibit transmission of pain from the C fibres to the brain
What is tranacutaneous electrical nerve stimulation?
Method of pain relief
Uses a mild electrical current which can reduce pain signals to the brain and release endorphins that also help reduce pain
Name some topical preparations used to treat chronic neuropathic pain?
Capsaicin: chilli, intense burning followed by pain relief
Lignocaine: transient pain relief effect
What are some protective mechanisms we can do to prevent chronic pain?
Regional blocks, such as epidural while amputating a leg
This reduces phantom limb pain
Peri-operative gabapentin or pregabalin
Holistic approach to surgery
Name an anti-convulsants drug used for pain?
Gabapentin
