Painful Small Fiber Neuropathies

Abstract

This article reviews the clinical features, pathophysiology, and treatment of small fiber sensory neuropathy. Neuropathic pain is prevalent among patients with peripheral neuropathies of diverse etiologies. For example, in one recent study using the sensitive Neuropathic Pain Symptom Inventory as a screening tool, neuropathic pain was reported in 94% of patients with different peripheral nervous system diseases. Neuropathic pain is frequently underrecognized or inadequately treated. Furthermore, the paucity of clinical signs with small fiber neuropathy may delay recognition of an organic process. Pain, or uncomfortable symptoms, typically results from damage to small unmyelinated nerve fibers (C fibers) or thinly myelinated nerve fibers (A delta fibers). Recent research has helped discover the location of the "pain generators" within the injured peripheral nerves. Small fiber neuropathies are relatively common in clinical practice, but until recently most of the available neurodiagnostic tests focused on large caliber nerve fibers. In the past two decades, the widespread use of quantitative sensory testing and punch skin biopsies to evaluate small caliber nerve fibers has substantially changed the neurologist's ability to diagnose and manage small fiber sensory neuropathy. Neuropathic pain from small fiber neuropathy is prevalent and is caused by a wide variety of disorders, many of which are treatable, especially if recognized early in the process.