Pathological pain Flashcards
what is the definition of abnormal/maladaptive/pathological pain
unpleasant sensory/emotional experience resembling that associated with actual potential tissue damage
persists beyond healing when no stimuli present
can arise spontaneously
why does pathological pain require different treatment to nociceptive and inflammatory pain
it has additional neuroimmune components
what is chronic pain
pain persisting beyond normal healing time of 3ish months
what are the potential causes of pathological pain
chronic injury/disease
changes in nociception
damage to peripheral or cns (neuropathic)
no known organic cause
what are the nomral changes to peripheral transduction after injury
perihperal nerve injury -> acute inflammation -> peripheral sensitisation -> hyperalgesia/allodynia
what are the changes to peripheral transduction after chronic injury
preipheral nerve injury -> chronic inflammation/aberrant regeneration -> peripheral sensitisation -> hyperalgesia/allodynia/dysaesthesia
what might cause peripheral sensitisiation that persists beyond injurY
change in distribution/exp of primary sensory neuron specific vgc Na+ channels
describe the change in vgc Na+ channels
become conc around nerve site of injury = changes in mem excit
lower nociceptor threshold (eg lowering temp thresholds)
or ectopic discharges from primary noc neurons
which 2 factors contribute to hyerpalgesia/allodynia/dysaesthesis associated with chronic pain
changes to Na+ chans and activation of silent receptors
what is central sensitisation
inc excit of noci pathways in dorsal horns
what are the mechanisms of central sensitisation
- repetitive impulses from C fibres => increased sens of non-specific , wide dynamic range neurons via NMDAR =? wind up/hyperexcitability
- new input from non-noci (alpha) fibres to 2nd order neurons = sprouting into lamina II, or expression of neuropeptides
what changes to modulation can lead to path pain
loss of descending inhibitory signals
loss of local inhibitory interneurons
