Wikis > Neurology > Pain > Hyperalgesia/allodynia


Pain that is induced by stimuli that do not normally cause pain. Tactile sensations are transformed into painful sensations.

Hyperalgesia – lower pain threshold or exaggerated response to noxious stimulus that is not normally that painful
Hyperpathia – painful syndrome that is characterised by an abnormally painful reaction to a stimulus as well as an increased threshold
Allodynia – pain following a non-noxious stimulus that does not normally produce pain

Mechanisms :
1) Peripheral nerve endings are sensitised  low receptor threshold:
• this is the mechanism that causes the ABC syndrome – burning pain and hyperalgesia to mechanical stimuli; heat increases symptoms and cooling relieves; skin is red and hot
2) Ephapses:
• abnormal electrical cross talk between axons
3) Changes in central plasticity:
• sensitisation of second order sensory neurons  overreact
4) Central disinhibition:
disruption of inhibitory mechanisms may cause pain

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