This article reviews the clinical, neurophysiologic, and neuropathologic findings in patients presenting with small fiber neuropathies. Emphasis is placed on recent updates to the literature, but also on understanding the differential diagnosis and initial evaluation of patients with small fiber neuropathy.
There have been several updates in the literature about diseases associated with small fiber neuropathy. First, treatment-induced neuropathy in diabetes mellitus is an iatrogenic small fiber neuropathy linked to overly rapid correction in blood glucose levels in the setting of chronic hyperglycemia. Second, several novel mutations to sodium channels have been identified in patients presenting with idiopathic small fiber neuropathy that may significantly alter our understanding and future treatment of small fiber neuropathy. Third, antibodies against voltage-gated potassium channels appear to be associated with a much higher incidence of pain than would be expected, although the mechanism has not been established. Fourth, the link between glucose dysregulation, metabolic syndrome, and neuropathy continues to grow. Finally, several other disorders, including postural orthostatic tachycardia syndrome, have been postulated to be associated with small fiber neuropathies.
Small fiber neuropathies are a heterogeneous group of disorders that may present with a variety of sensory or autonomic symptoms. Recent reports highlight a number of new causes of small fiber neuropathy that continue to reduce the number of remaining idiopathic cases.