Hi hope for the cure

When en bloc says 'motor nerve involvement' and 'long fibers' I think she's referring to long fiber Peripheral Neuropathy (PN) - correct me if I'm wrong here en bloc.
SFN is one subset of PN and refers to damage in smaller nerves (as opposed to larger nerves) - there are over 100 different types of neuropathy and just as many causes. They are mainly divided into 3 different types depending on how they affect the body: Sensory, Motor & Autonomic. Here's a link to a better explanation:

http://www.ninds.nih.gov/disorders/p...neuropathy.htm

It is possible to have more than one type at the same time.
SFN is mentioned in the 'skin biopsy' paragraph under Diagnosis.

. . . and ShaggyChic
As regards supplements - you're right to be cautious and consider them carefully before trying - side affects can be different for individuals - but don't rule them out completely. With PN being so complex I took the approach of first trying to get as accurate diagnosis as possible, then searched for probable cause (eliminating as many unlikely ones as possible). This helps to narrow down options for possible treatment.

Ensuring you get as many essential vitamins and nutrients as possible through your diet is the next step. Research what food sources contain good levels of each nutrient and if you have adequate of those in your diet then your levels should be okay (unless you have a malabsorption condition). Cut out or reduce those foods which could be causing harm - ie sugar, alcohol etc. If you still feel you may still be lacking in certain vitamins (eg. B12, Magnesium, Vit D. etc) get tested and then consider supplementation.

If you are already on prescription medications you need to make sure that any supplements aren't likely to interact. If you decide you want to take a particular supplement only start one at a time to monitor effects. Keep a journal - some supplements will have an immediate effect others may need 3 mths or longer to show any improvement. Remember that more is not necessarily better, eg the highest dose of a probiotic may cause constipation whereas a lower dose may help intestinal issues without causing problems. Sometimes it's a case of try it and see.

To help figure out what is best to buy there is a website that does independent testing: Supplement Rankings - Labdoor

Check for any academic research that may have been done on a specific supplement. Be cautious of website sales hype and any manufacturer funded studies as there may be bias. Also if you have questions about a specific type of supplement you can come here and ask or use the search function.

Hope this is of help and hasn't added to confusion.