Small fiber neuropathies

Rebecca E Traub MD (

Dr. Traub of The University of North Carolina received honorariums from Akcea Therapeutics, Alnylam Pharmaceuticals, and CSL Behring as an advisory board member.

)
Louis H Weimer MD, editor. (

Dr. Weimer of Columbia University has received consulting fees from Roche.

)
Originally released June 7, 2010; last updated November 18, 2019; expires November 18, 2022

Overview

Small fiber neuropathy is a polyneuropathy affecting the small unmyelinated and thinly myelinated sensory and autonomic nerve fibers. Symptoms typically include numbness, paresthesias, and neuropathic pain, and sometimes it can include symptoms of autonomic dysfunction. Physical exam may demonstrate loss of small fiber modalities on sensory testing, but may be normal, often leading physicians to presume a psychiatric source to patient symptoms. First line diagnostic tests for sensory symptoms, including EMG/NCS testing and MRI, are normal. Skin biopsy for epidermal nerve fiber density is currently considered the best test for confirming a small fiber neuropathy diagnosis. Laboratory testing is recommended to evaluate for underlying causes for small fiber neuropathy, although often no cause is identified and the neuropathy is deemed idiopathic. Medications and nonpharmacologic therapies can be used to treat neuropathic pain and autonomic symptoms.

Key points

 

• Small fiber sensory neuropathy often presents with length-dependent numbness or pain due to abnormal somatic unmyelinated or small myelinated nerve function.

 

• Autonomic symptoms and subclinical autonomic dysfunction are common with small fiber neuropathy.

 

• Although there is no gold standard diagnostic test, skin biopsy demonstrating reduced epidermal nerve fiber density, in the appropriate clinical setting, is most often used to confirm small fiber neuropathy diagnosis.

 

• Laboratory testing to evaluate for conditions causative of small fiber neuropathy should include those assessing for diabetes, Sjögren syndrome, celiac disease, vitamin deficiencies and toxicities, amyloidosis, and in some cases, genetic disorders.

 

• Frequently, no cause for small fiber neuropathy is identified, and it is idiopathic.

 

• Symptomatic management of small fiber neuropathy includes medications and nonpharmacologic treatments for pain and autonomic symptoms.

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