--is unlikely to come from pure small-fiber neuropathy, as twitches happen in muscles and small-fiber neuropathy by definition involves the unmyelinated sensory nerves that control the sensations of pain and temperature.

On the other hand, it is not unusual for those who have small-fiber syndromes to have some large fiber involvement of nerves that control muscle, though it may not be global enough to show up on nerve conduction studies, and that may result in twitching or fasiculations.

I would think, though, that such twitching is more likely due to electrolyte imbalance, which may not even be related to the rest of your condition. Such imbalance is very, very common--Mrs. D has talked about how many of us are probably deficient in magnesium--and supplementing with that, and possibly potassium, is definitely worth a trial.