Small Fiber Neuropathy

What Is Small Fiber Neuropathy?

Small fiber neuropathy (SFN) affects the small nerve fibers that detect pain, temperature, and autonomic functions. Unlike large fiber neuropathy, it typically doesn't cause weakness or affect reflexes, and standard nerve tests may be normal. It can cause significant pain and is increasingly recognized as a cause of unexplained chronic pain.¹

Types of Small Fibers

A-delta Fibers

• Sharp, fast pain sensation
• Temperature detection (cold)

C Fibers

• Slow, burning pain
• Temperature (heat)
• Autonomic functions

Symptoms²

Sensory Symptoms

• Burning pain (often feet/hands)
• Electric shock sensations
• Pins and needles
• Sensitivity to touch
• Cold/heat intolerance
• Pain worse at night

Autonomic Symptoms

• Dry eyes/mouth
• Sweating abnormalities
• Orthostatic intolerance
• GI issues
• Urinary symptoms
• Heart rate variability

Causes³

• Diabetes/prediabetes (common)
• Autoimmune conditions
• Sjogren's syndrome
• Celiac disease
• Sarcoidosis
• Vitamin B12 deficiency
• Amyloidosis
• Medications
• Idiopathic (no cause found)

Diagnosis

Standard Tests Often Normal

• EMG/nerve conduction studies
• These test large fibers only

Tests for SFN

• Skin punch biopsy (gold standard)
• Measures nerve fiber density
• Quantitative sensory testing
• Sudomotor testing
• Blood tests for causes

Treatment

Treat Underlying Cause

• Blood sugar control
• Vitamin supplementation
• Immunotherapy if autoimmune

Pain Management

• Anticonvulsants (gabapentin, pregabalin)
• Antidepressants (duloxetine, amitriptyline)
• Topical treatments
• IVIG in select cases

Autonomic Symptoms

• Specific treatments for each symptom
• POTS management
• GI treatments

Living with SFN

• Protect sensitive skin
• Comfortable footwear
• Temperature management
• Pace activities
• Support groups helpful

References

1. Devigili G, Tugnoli V, Penza P, et al. The diagnostic criteria for small fibre neuropathy: from symptoms to neuropathology. Brain. 2008;131(Pt 7):1912-1925.
2. Themistocleous AC, Ramirez JD, Serra J, Bennett DL. The clinical approach to small fibre neuropathy and painful channelopathy. Pract Neurol. 2014;14(6):368-379.
3. Terkelsen AJ, Karlsson P, Lauria G, et al. The diagnostic challenge of small fibre neuropathy: clinical presentations, evaluations, and causes. Lancet Neurol. 2017;16(11):934-944.