You definitely want to do some reading in the Useful Websites section of the Peripheral Neuropathy section here:

STICKY - Important Links to Useful websites

Generally, small fiber neuropathies preferentially or exclusively attack the small sensory nerves that are thinly myelinated or unmyelinated, and which subsume the sensations of pain, temperature, and a number of autonomic functions such as blood pressure and peristalsis of the digestive tract. The symptoms are therefore sensory or autonomic in nature, thought these can be quite varied in both kind and intensity.