Since the 19th century work of Ramón y Cajal and French neurologist Charcot, neurologists have focused on localization with the long-standing belief that only by understanding if a disease process affects the brain, spinal cord, nerve, and/or muscle, can the clinician begin to determine the cause of the specific pathology. In the peripheral nervous system, we now understand that some diseases can affect all types of nerves, but others can be confined to just the myelin or just the axon. Likewise, a disease can affect just large fiber neurons or small fiber neurons. Even within diseases that affect purely small fibers, we now understand that this can present as purely sensory disruption such as pain, purely autonomic dysfunction, or in some patients a combination of both sensory and autonomic. Being able to parse patients into different subsets of neuropathies allows for a better understanding of the pathophysiology and potential treatments. One disease that would benefit from a more specific determination of clinical phenotypes to allow for a more precise diagnosis and potential improvement in patient condition is small fiber neuropathy (SFN).
