Large/small fibre - what the heck ?
 

hi guys

I am trying to work out which is small fibre PN, and what it large fibre. Particularly, I'd like to know which I have, as it has only been described to me as being sensori-motor axonal neuropathy.

Some years ago I used to have the sort of neuropathy that involved severe pain in both hands and one foot - that went away then a few years later I got this axonal neuropathy which I have had for many years and is gradually getting worse (numbness and loss of motor nerve function).

So, what do I have now ? Small or large fibre ? I'm not sure that this matters really, I am just curious.

thanks in advance

raglet

Could be both.
 

Generally, this distinction depends on symptomology.

The small fibers are the thin, lightly myelinated or unmyelinated fibers that subsume the sensations of pain and temperature, and also underlie most autonomic functioning. So one who has burning or lancating pain, numbness and or disrupted temperature sensation generally has some small-fiber component. Depending on the specificity of the symptoms, one may even be able to narrow down just which types of fibers are being attacked (although the attack can be global, too).

Larger, myelinated fibers include all motor nerve fibers, as well as those that underlie the sensations of vibration, mechanical touch, and bodily positional feedback. So disruption here presumes some problems with those fibers.

People who have global autoimmunities, or whose neuropathy includes the nerve roots near the spine and/or the ganglia, typically have both types of fibers involved.

Only large fibers can develop demyelination, though, as the smallest fibers do not have myelin sheathing. Small-fiber neuropathy therefore is by definition axonal--the damage is to the fiber itself. Large fibers can be damaged both by demyelination and by direct attack on the axon, and often both occur simultaneously, or one is secondary to the other (i.e., demyelination may expose the axon to assault, so one has "demyelinating neuropathy with secondary axonal degeneration").

thank you, that was a great description. I had been trying to google it, with little success.

Sounds like I have had both as I have motor and numbness problems. I still do get some pain in my hands sometimes, but as compared with when it was very severe (I used to describe it as a 22 on a scale of 1-10) it is very occiaional and very mild. I also have some evidence of radiculopathy in my nerve studies, which I think is nerve root involvement, and of course my neuropathy is secondary to my lupus (autoimmune).

thanks again, that was a great description

cheers

raglet