Small Fibre Neuropathy
The Small fibre neuropathy (SFN) and large fibre neuropathy belong to a group of diseases known as peripheral neuropathies. Polyneuropathy refers to cases where either the large fibres are affected, or both the large and small fibres are affected. SFN refers to isolated small fibre involvement.[1]
Aetiology
- Metabolic
- Diabetes mellitus
- Glucose intolerance
- Vitamin B12 deficiency
- Hypothyroidism
- Hiperlipidemia
- Hipervitaminosis B6
- Chronic kidney disease
- Dysimmunity/inflammatory diseases
- Sjögren’s syndrome
- Sarcoidosis
- Systemic lupus erythematosus
- Celiac disease
- Infectious
- HIV
- Hepatitis C
- Ebstein-Barr virus
- Lyme disease
- Leprosy
- Toxic agents and medications
- Alcohol (this can eventually cause large fibre neuropathy)
- Antibiotics (metronidazole, nitrofurantoin, linezolid, isoniazid)
- Anticancer agents (bortezomib, platin)
- Antiretroviral drugs
- Genetic diseases
- Fabry’s disease
- Familial amyloid polyneuropathy (transthyretin
Clinical Features
Small fibre sensory neuropathy can cause severe symptoms but there can be minimal objective findings on examination. Class symptoms include distal burnings, pain, numbness, paraesthesia, and autonomic symptoms. Autonomic symptoms can include sweating alterations, temperature dysregulation, dry mouth and eyes, and erectile dysfunction. Most affected patients have a combination of positive signs (e.g. hyperalgesia, and allodynia), and negative signs (e.g. diminished pin prick and temperature sense). Standard electrophysiologic testing is typically normal with disorders that affect mainly the small, unmyelinated nerve fibres. Sural nerve biopsy may be only minimally abnormal, or even normal.
- Characteristics of sensory nerve fibres
| Nerve fibre | Myelinated axons | Diameter (µm) | Conduction velocity (m/s) | Sensory information | Usefulness of electroneuromyography | Usefulness of QST |
|---|---|---|---|---|---|---|
| Aα | Yes | 13-20 | 80-120 | Proprioception, muscle spindle primary endings (Ia), golgi tendon organs (Ib) (and alpha motor neurons) | Yes (H reflex) | No |
| Aβ | Yes | 6-12 | 33-75 | Discriminative mechanoreception (touch, vibration), proprioception, pain modulation (block nociceptive information, allodynia in sensitisation) | Yes (sensory nerve conduction) | Yes |
| Aγ | Yes | 4-8 | 15-40 | Touch, pressure (and gamma motor neurons) | No | |
| Aδ | Thin | 1-5 | 3-30 | "rapid" pain, crude touch, pressure, temperature. AMH type I for rapid mechanical pain (high heat threshold >53C), AMH type II for rapid heat pain (lower heat threshold 43-47C). | No | Yes |
| C | No | 0.3-1.5 | 0.5-2.0 | "slow" pain, touch, pressure temperature (and postganglionic autonomic). Polymodal. | No | Yes |
See Also
References
- ↑ Maslinska et al. Small fibre neuropathy as a part of fibromyalgia or a separate diagnosis? Int. J. Clin. Rheumatol. (2018) 13(6), 353-359
Literature Review
Literature Review
- Reviews from the last 7 years: review articles, free review articles, systematic reviews, meta-analyses, NCBI Bookshelf
- Articles from all years: PubMed search, Google Scholar search.
- TRIP Database: clinical publications about evidence-based medicine.
- Other Wikis: Radiopaedia, Wikipedia Search, Wikipedia I Feel Lucky, Orthobullets,
