6 hours ago
allodynia refers to pain that is evoked by a stimulus that normally does not ❎ produce pain (like a gentle brush of the arm feeling like a knife 🔪 wound).
when i try to explain how this occurs to my patients i usually start talking water slides. stay with me a minute will ya?
under normal circumstances, we have nerves in the body that respond to different types of stimuli: temperature 🔥💧, pressure🗜, chemical🛢, dangerous stuff☠ etc. these nerves send messages to the spinal cord, where they are relayed to their appropriate corresponding pathway and then up ⬆ to the brain (pressure nerve is relayed to the pressure pathway, danger nerve to the danger pathway and so on). more to it than this but let's keep it simple. picture a waterslide with separate tracks that stay separate, like in the first slide.
with allodynia, something changes in the spinal cord. it becomes 'sensitized' via mechanisms not completely understood: and now messages that travel via pressure and temperature nerves can end up in the danger pathway. now think of a water slide that has different tracks (representing different nerves) that all drop off into a common pool 🌊 (the danger pathway). see slide 2!
now: normal sensations that aren't typically threatening 👍 are interpreted as dangerous/noxious👎 because of this 'cross-talk.' end result: pain from a normally non-painful stimulus! allodynia!