Small Fibre Neuropathy (SFN)

Small Fibre Neuropathy (SFN) – When the Smallest Nerve Fibres Cause Symptoms

Small Fibre Neuropathy (SFN) is a disorder affecting the smallest nerve fibres of the peripheral nervous system. These include the thin unmyelinated C fibres and thinly myelinated Aδ fibres, which are responsible for transmitting pain, temperature, and certain touch sensations. In addition, these fibres play a crucial role in regulating the autonomic nervous system, which controls functions such as sweating, heart rate, blood pressure, digestion, and bladder function.

Because these small nerve fibres are often not detected by standard nerve conduction studies, the condition may remain undiagnosed for a long time.

Common Symptoms

Symptoms can vary considerably between individuals and often develop gradually.

Possible symptoms include:

Burning pain in the feet or hands
Tingling or pins-and-needles sensations
Numbness
Increased sensitivity to touch (allodynia)
Impaired temperature perception
Electric shock-like pain
Worsening pain at night
Abnormal sweating
Dizziness upon standing
Rapid heart rate or circulatory symptoms
Gastrointestinal disturbances
Bladder dysfunction
Severe fatigue

In some patients, pain is the dominant symptom, while others primarily experience autonomic dysfunction such as circulatory instability or abnormalities of sweating.

Potential Causes

Small Fibre Neuropathy can have many different causes. Common underlying conditions include:

Diabetes mellitus and prediabetes
Autoimmune diseases (e.g. Sjögren’s syndrome, systemic lupus erythematosus)
Vitamin deficiencies, particularly vitamin B12 deficiency
Metabolic disorders
Infections
Medication-related nerve damage
Genetic conditions
Toxic exposures
Long COVID and other post-infectious syndromes

Despite extensive investigations, the underlying cause remains unknown in a proportion of patients.

Why Is Diagnosis Often Challenging?

Many patients experience symptoms for years despite normal MRI scans, nerve conduction studies, and routine laboratory investigations. This is because conventional neurological tests primarily assess large nerve fibres and may fail to detect damage to small nerve fibres.

As a result, specialised diagnostic methods are often required to establish the diagnosis.

Small Fibre Neuropathy Diagnostics at Neuro Praxis Düsseldorf

Neuro Praxis Düsseldorf offers advanced diagnostic techniques for the assessment of small nerve fibre disorders and autonomic nervous system dysfunction. Depending on the individual clinical situation, investigations may include:

Quantitative sensory testing (CASE IV)
QSweat® testing for sudomotor function
Sudoscan®
Skin biopsy for measurement of intraepidermal nerve fibre density (IENFD)
Comprehensive autonomic nervous system evaluation
Extended laboratory investigations to identify underlying causes
Additional electrophysiological testing where appropriate

The selection of diagnostic procedures is tailored to each patient based on a detailed neurological history, symptoms, and previous medical findings.

Treatment

Treatment is primarily directed at the underlying cause whenever one can be identified. In addition, various options are available to help manage symptoms, including:

Treatment of the underlying disease
Correction of metabolic abnormalities and vitamin deficiencies
Specialised medications for neuropathic pain
Management of autonomic dysfunction
Individualised neurological follow-up and monitoring

When Should an Evaluation Be Considered?

A specialised assessment may be appropriate if you experience:

Burning or neuropathic pain
Tingling, numbness, or unexplained sensory symptoms
Dizziness, palpitations, or circulatory problems
Symptoms suggestive of autonomic neuropathy
Neurological symptoms associated with Long COVID or post-vaccination syndromes
Persistent symptoms despite normal standard neurological investigations

Early diagnosis can help identify potentially treatable causes and may significantly improve quality of life and long-term outcomes.