Painful small-fiber neuropathies

This chapter describes that small-fiber neuropathies are a subtype of sensory neuropathies exclusively or predominately affecting small diameter nerve fibers. These include small diameter myelinated fibers (Aδ) and unmyelinated (C) fibers. Both sensory and autonomic fibers may be involved. It reviews that generally a mild degree of large-fiber dysfunction is accepted when diagnosing small-fiber neuropathy. In pure small-fiber neuropathy, there should be no muscle atrophy or weakness. In most patients, the neuropathy starts distally with a “dying back” pattern, but there seem to be some cases with a more patchy and asymmetric pattern. The chapter explores that small-fiber neuropathy is supposed to account for more than 90% of cases with burning feet. If an underlying cause of small-fiber neuropathy can be found, it is most often diabetes mellitus. Sarcoidosis may manifest with a painful small-fiber neuropathy, similarly systemic lupus erythematodes. Small fibers constitute the majority of fibers in a peripheral nerve.