Our Emerging Understanding of Small Fiber Neuropathies

Over the last decade, it’s become very clear that many people who experience widespread pain or maybe first experience pain in their distal extremities, burning pain, difficulties with sweating, difficulties with bowel function, difficulties with urination, may be experiencing small fiber neuropathy. In fact, in three studies almost 50 percent of individuals who had been diagnosed with fibromyalgia as the reason for their chronic widespread pain actually had biopsy-proven changes consistent with small fiber neuropathy. With respect to what causes small fiber neuropathy, glucose intolerance or frank diabetes, even metabolic syndrome is the most common associated set of circumstances. Many autoimmune disorders--Sjögren’s syndrome, rheumatoid arthritis, lupus--are associated with small fiber neuropathy as well. B12 deficiency, hepatitis C, HIV can be associated. Celiac disease or even gluten intolerance can be associated with small fiber neuropathy. A recent publication by a neuromuscular specialist at Columbia University has just documented how often this happens in celiac disease or gluten intolerance... Another important group, however, are families that have small fiber neuropathy as a hereditary neuropathy. But about half the people who experience small fiber neuropathy don’t have a known cause.

Typically we would approach small fiber neuropathy with the kind of treatments that we would use for neuropathic pain. So that might mean various antidepressants that have been used as analgesics, as well as various anticonvulsants. Examples of antidepressants would be duloxetine, tricyclics like amitriptyline, nortriptyline, similar medications. For anticonvulsants, gabapentin, pregabalin, carbamazepine have been utilized. Intravenous lidocaine infusions are another approach under investigation, as well as the use of intravenous gamma globulin since there seem to be in some instances an immune-mediated disorder associated with a small fiber neuropathy. In less common use would be plasma exchange (also known as plasmapheresis) where a person’s plasma is taken out and exchanged, cleaned and given back with clear plasma to remove any circulating antibodies or other factors that might be perpetuating the disorder.