--a number of acute onset neuropathies are associated with previous infections--both viral and bacterial--most likely through autoimmune molecular mimicry. The theory is that the body is invaded by a pathogen, mounts an immune response, fights it off, even, but the now activated immune system, which works by shape--antibodies are produced to "fit" pathogens spatially, like a key in a lock--goes after anything with a similar shape. A number of pathogens, including those Mrs. D mentions, have cell wall shapes similar to many people's nerve epitope shapes, and it is theorized that the antibodies then go after those nerve components.
This is certainly the leading candidate for cause in my case, although we never found any direct evidence. There was, however, some evidence of Epstein-Barr Virus reactivation--and EBV is one of those pathogens that has been implicated in acute-onset neuropathies.
Classic Gullain Barre is an autoimmune demyelinating acute onset neuropathy--the immune response is against myelin sheathing, so it attacks large calibre nerves and leads to severe motor symptoms, and some sensory ones. There are variants, including some that have a more prominent sensory component and less of a motor one. And, there is an entity known as acute onset axonal neuropathy, which is a Gullain-Barre like syndrome that attacks the axons (the nerve fibers themselves) and thus may, depending on individual body chemistry and the prior infection/events, attacks small-fiber nerves preferentially (the small fibers are unmyelinated and subsume sensations of temperature and pain--this is what we think happened with me).
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