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Muscle Weakness with PN (Large Vs Small Fiber)
Some months ago, I began seeing a neurologist due to years of muscle weakness in my legs/feet and arms/hands, that I originally thought was unrelieved thyroid symptoms (I am treated for hypothyroidism caused by Hashimoto's thyroiditis - 8 years). I also thought it might be associated Chronic Fatigue Syndromes or Fibromyalgia, which thyroid patients often complain of. It wasn't until I also developed tingling, burning, stabbing and aching in the nerves that I suspected peripheral neuropathy.

The neuro-doc found that I had vitamin E deficiency (flagged very low) and my regular MD found that I had low-normal (insufficient) B12 level and vitamin D deficiency (flagged low).

After I got past the cyberchondria phase, some of the intense phobia being sparked by info posted by people suggesting that only diseases like ALS or other motor neuron diseases cause muscle weakness, that I began finding reputable information stating that peripheral neuropathies very commonly cause muscle weakness and even muscle atrophy. To this day, I have not seen any muscle atrophy with my PN but I do still have the muscle weakness which progressed to a moderate level over about a 10 year period.

Strangely, huge numbers of sources, some reputable, state that "small fiber neuropathy" includes muscle weakness as a symptoms, while lots of other sources state that only "large fiber neuropathies" cause muscle weakness.

I came to the conclusion, after ongoing research for these past 6 months or so (since going to a neuro-doc) that the reason muscle weakness is found so often in people with small fiber neuropathy, is likely because there is a degree of large fiber involvement in most cases of it. One source in-particular that brought me to this conclusion was an article I found by three MD/Neurologists which states the following:

"Most peripheral neuropathies involve large as well as small-fiber dysfunction. A small subset of neuropathies present with restricted or predominant small-fiber involvement."
(By: Al-Shekhlee, Amer MD; Chelimsky, Thomas C. MD; Preston, David C. MD)

Article title/link: "Small-Fiber Neuropathy" ("The Neurologist" Website) - http://journals.lww.com/theneurologist/Abstract/2002/07000/Review__Small_Fiber_Neuropathy.4.aspx

If you have any doubt about the vast number of articles that attribute muscle weakness directly to small fiber neuropathy, just use "small fiber neuropathy symptoms" or "small fiber neuropathy muscle weakness" as search terms and you will see bookoos of them. Apparently however, all of these sources are incorrect according to some of the medical ones.

Also, one thing that is confirmed repeatedly, even by the most reputable medical sources, is the fact that small fiber neuropathy (SFN) also affects autonomic functions in the body (i.e. involuntary ones such as blood pressure, breathing and heart rate), in the majority of cases, even if only mildly. They in fact use testing of autonomic functions to help diagnose SFN.

I've seen posts here and there, in which people diagnosed with large fiber neuropathy (LFN) are told that it is much more serious than (SFN) and that they may be on their way to losing all of their major bodily functions (again a little nudge toward cyberchondria).

In light of what I have posted above and from what I take from the source searches I have done extensively, my take on it would be this:

Most people with PN have mixed fiber cases, with one or the other causing the more prominent symptoms. People who do go on the progress to fatal types of PN, are likely those with severe forms of difficult-to-control diabetes. I also do not believe that pain or muscle weakness levels in the extremities, necessarily indicates what type systemic affect this might have on all bodily organs. Lots of people with PN complain of severe pain or weakness they have dealt with for decades.

I just wanted to express my two cents worth as I do on occasion at these forums. The information you find online can at times be frustrating because there are ongoing disagreements on aspects of PN and even medical professionals on some of the sites I've found, are frustrated at the lack of progress in understanding and treating types of PN. Of course treating underlying causes of PN is essential and can even reverse or at-least halt some cases but otherwise, treatments are symptomatic only and no truly recognized nerve regeneration treatments have yet to be found. Hopefully advances will soon be made in this area.

Thanks,
JL  



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