Pain after SCI Flashcards
The epidemiology of pain after SCI?
-approx. 60-70% of individuals with SCI experience some kind of chronic pain (maybe as high as 95%)
-approx. 20-40% of these individuals report their pain as severe
-pain after SCI may further decrease A.D.L (Activities of daily living), further increase stress and depression and may be a major cause of the increased incidence of suicide in this population
-approx. 30% of ppl with SCI who experience pain stated that they would trade loss of bladder, bowel or sexual function for pain relief
The existence of pain after SCI may not be correlated with the severity of the injury (ASIA classification) but…?
- the intensity of pain may be associated with the level of injury, such that lower injuries are associated with a greater chance of severe pain
-10-15% of individuals with tetraplegia experience severe pain
-25% with thoracic paraplegia
-47% with cauda equina
What are the descriptors for sensations of pain after SCI?
- Allodynia- pain evoked by a normally non painful stimulus to normal skin
- hyperalgesia- increased sensitivity to noxious stimulation
3.central pain- pain associated with a lesion of the CNS
- radicular pain- pain associated with damage to the peripheral nervous system (dorsal root), stimulus that wouldnt be harmful is at level of injury
5.parathesia- abnormal skin sensation (burning, tingling)
What is musculoskeletal pain?
-pain that arises from damage or overuse to structures such as bones, ligaments, muscles etc. OR damage to spinal structures (acute pain prior to spinal stabilization)
-occurs at or above the lesion level (in incomplete injuries) and may be described as dull, aching, worse with activity, eased by rest
What is Visceral pain?
-pain that arises from pathology of the abdominal organs possibly due to secondary health complications associated with SCI (bladder of bowel distension or disease). must consider level and severity of injury
-injury above abdomen can be a result of uti or constipation- may not be able to feel
-may be described as dull, poorly localized, cramping etc.
What is neuropathic pain?
-pain that occurs following damage to the central or peripheral nervous system (Radicular)
What is neuropathic at level pain?
-pain that is perceived within two segments above or below the lesion level, may be described as burning, stabbing, electric, shooting, presence of allodynia
What is neuropathic at level radicular pain?
-pain due to damage of the peripheral nervous system (dorsal root)
What is neuropathic at level central pain?
-pain due to damage (changes) of the central nervous system
What is neuropathic below level pain?
-pain that is perceived at least 3 segments below the level of the injury
-may be described as burning, tingling, aching, shooting, stabbing
-more likely to be diffuse compares to neuropathic at level pain (common)
-40% of individuals with SCI experience musculoskeletal pain
-36% experience at level neuropathic pain
-19% experience below level neuropathic pain
*Below level neuropathic pain may have a late onset,
i.e. This is the predominant type of pain 3-6 months post injury and some have reported its onset as late as 10 years post injury
Possible mechanisms behind neuropathic pain?
Dorsal roots carry:
-Large myelinated A8 fibres which synapse on inhibitory interneurons (inhibit via GABA)
-Small unmyelinated C fibres which synapse on excitatory interneurons (excite via glutamate)
-Descending tracts (corticospinal and reticulospinal) may also synapse at posterior grey matter and cause an inhibitory effect (via endorphin, serotonin, NE release GABA release
Root carry two different nerves
-One large myelinated nerve
-1-delta fibres and go into posterior , synapses on inhibited neuron named gaba
-Brain can send fibers , releases gaba
Possible mechanisms behind neuropathic pain at level radicular pain?
Damage to the dorsal root may cause preferential damage to the AS fibres, resulting in an imbalance favouring excitation of the substantia gelatinosa
People get radicular pain due to damage to peripheral nerve resulting or imbalance
Delta-a fibres more susceptible to damage because larger and isolated?
Possible mechanisms behind neuropathic central pain?
-Damage to the spinothalamic tract is necessary but not sufficient for the development of neuropathic central pain.
-This damage may cause hyperactivity of the spinothalamic tract neurons or the thalamus (i.e. spontaneous activity, reduced stimulation thresholds, prolonged after-discharges)
Mechanisms behind the hyperactivity of the spinothalamic system?
- accumulation of Na+ channels on the spinothalamic neurons at the sitre of injury
-membrane becomes unstable and spontaneous action potentials may result (Na+ channel blockers, lidocaine, may relieve pain in animals but not humans) too much glutamate–> causes more damage to nervous system - SCI results in a hyperactivity of the primary afferent neurons, and an exaggerated release of glutamate (received by NMDA receptors)
a) further damage to spinothalamic tract (excitotoxicity)
b) exaggerated pain- blocking NMDA receptors may help to relieve pain in humans - Loss of GABA releasing cells in the spinal cord, i.e. loss of inhibition of pain sensation (baclofen (GABA agonist) may relieve pain in humans with SCI) can lose guava cells
- Reduction in opioid (endorphin) activity in the brain and spinal cord due to increased level of CCK (cholecystokinin) which inhibits the effects of endorphins (morphine (opioid receptor agonist) may relieve pain in humans with SCI)
- Loss of serotonin and norepinephrine from damaged descending tracts (blocking the re-uptake of serotonin and NE may relieve pain in humans with SCI)
Management of neuropathic pain after SCI?
- The usual pain killing medications (anti-inflammatory, tylenol) used for musculoskeletal pain will have no effect on neuropathic pain
1.Physical and mental activity
Due to distraction from pain or endorphin production, and decreased depression.
2.Antidepressants:
-Many antidepressants work by interfering with serotonin reuptake, which may also relieve neuropathic pain (Prozac)
3.Narcotic medications
Morphine, codeine work by the same mechanism as endorphins
Inflammation can worsen pain
4.Transcutaneous electrical nerve stimulation (TENS)
-May relieve radicular pain by selectively activating the large Afibres which inhibit spinothalamic activation.
-tens -Can stimulate part of body and Activate fibers
5.Surgical destruction of part of the posterior gray portion of the spinal cord (DREZ surgery)
Drew
Surgically destroy
- relaxation techniques such as yoga, self-hypnosis, and meditation
7.marijuana (THC)
