Small Fibre Sensory Neuropathy SFSN

Diseases,

Synonyms:

Small fibre sensory neuropathy SFSN a.k.a. small fibre neuropathy SFN

Clinical features:

  • Small fibre involvement:
    • Neuropathic pain; allodynia, hyperalgesia
  • Reduced sensation to pin prick and temperature.
  • Absence of large fibre involvement: light touch, vibratory, proprioceptive sensory loss or absent deep tendon reflexes
  • Normal motor exam

Findings on Investigations:

+Electrodiagnosis NCS (sensory +motor +F waves) +/-EMG:

  • Normal

+Quantitative sensory testing QST:

  • Abnormal
  • This is used to determine the patients threshold for sensory stimuli (pain, cold, warm and vibration sensation) and comparing them to normative data.

+Skin biopsy:

  • Immunohistochemistry: polyclonal anti-protein-gene-product 9.5 antibodies (this stains nerve fibres in the skin) to assess Intra-Epidermal nerve fibre density IENF: reduced.

Na channel mutations in small fiber neuropathy

Investigations to consider:

  • Fasting blood glucose, HBA1c, TFTs, Lipid profile, ESR, CRP, ANA screen, ENA panel (anti- dsDNA, anti-Sm, anti-RNP, SSA, SSB, anti-Jo-1, antitopoisomerase ‘formerly anti Scl-70’, antinucleolar, anticentromere), ANCA (c-ANCA, p-ANCA), Complement C3, C4 and CH50
  • Infection tests: influenza, HIV
  • Paraneoplastic tests: anti-Hu Antibodies
  • Test for amyloidosis e.g. sural nerve biopsy.
  • Consider:
    • Autonomic neuropathy testing
    • Genetic testing for hereditary amyloid neuropathies

 Related articles:

References:

  • Shy ME, Frohman EM, So YT, Arezzo JC, Cornblath DR, Giuliani MJ, Kincaid JC, Ochoa JL, Parry GJ, Weimer LH; Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Quantitative sensory testing: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology. Neurology. 2003 Mar 25;60(6):898-904.