Small Fiber Neuropathy
What is Small Fiber Neuropathy?
Peripheral neuropathy refers to conditions that irritate or damage the nerves that connect the body to the central nervous system (spinal cord and brain). These nerves contain both small and large fibers. Large fibers carry the pain signals to the central nervous system, as well as control muscle movement while small fibers detect pain and play a key role in almost all involuntary bodily functions.
Small fiber neuropathy (SFN) is the more common of the two and causes pain, burning sensations and temperature sensitivity.
What Causes Small Fiber Neuropathy?
For most, SFN is idiopathic and no cause can be found. However, a high percentage of individuals with polyneuropathy (both small and large) also have diabetes. Other causes of SFN can include Sjogren syndrome, metabolic syndrome, and lupus.
What are the Symptoms of Small Fiber Neuropathy?
Typically, patients first start noticing burning and stinging dysesthesia in the feet that is worse at night and aggravated by prolonged standing or walking. Other symptoms include pain, paresthesia, and allodynia (pain in response to non-painful stimuli) in other parts of the body.
How is Small Fiber Neuropathy Diagnosed?
Patients usually have normal strength, reflexes, and vibration thresholds. In addition, unlike large fiber neuropathy, SFN will not show up on an EMG/NCS. However, these tests might be used by providers to rule out other causes of symptoms.
Typically, a skin biopsy is done to confirm loss of cutaneous nerve innervation. However, a normal skin biopsy does not exclude a diagnosis of SFN. Other tests include:
- Quantitative Sensory Testing (QST) – evaluates small nerve function by measuring thresholds for cold and warm sensations
- Quantitative Sweat Measurement (Q-Sweat) – assesses sweat gland nerve fiber density to detect automatic dysfunction
- Autonomic Cardiovascular Tests (ACTV) – examines heart rate and blood pressure responses to evaluate autonomic nervous system involvement
- Electrochemical Skin Conductance (ESC) – measures the ability of sweat glands to produce sweat, often used to assess distal small fiber damage
- Laboratory and genetic tests – to look for causes such as vitamin deficiencies, autoimmune conditions
How is Small Neuropathy Treated?
Treatment for SFN typically includes neuropathic pain medications, including antiseizure medications (like gabapentin and duloxetine). Additional treatment for SFN includes antidepressants and topical anesthetics.
It can be difficult to know when is the right time to file a disability insurance claim for small fiber neuropathy. Disability claims based on small fiber neuropathy can also be difficult to prove-up, particularly because symptoms can be subjective in nature and can vary.
If you have been diagnosed with small fiber neuropathy (or suspect that you might have it) and are worried that it may be impacting your ability to safely practice, it is best to speak with an experienced disability insurance attorney before making any changes to your work schedule or duties.
These posts are for informative purposes only and should not be used as a substitute for consultation with and diagnosis by a medical professional. If you are experiencing any of the symptoms described above and have yet to consult with a doctor, do not use this resource to self-diagnose. Please contact your doctor immediately and schedule an appointment to be evaluated for your symptoms.
Sources:
America College of Rheumatology
Harvard Health
American Academy of Neurology
Johns Hopkins
Cleveland Clinic
