Intraepidermal nerve fiber density

Intraepidermal nerve fiber density; nerve fiber density; small-fiber neuropathy; 

Method for determining intraepidermal nerve fiber density (IENFD) of a valid method for the diagnosis of isolated small-fiber neuropathies. It is determined in specialized laboratories in a skin biopsy.

Several studies have demonstrated a reduction in intraepidermal nerve fiber density and epidermal nerve fiber bundles in patients with neuropathy. In addition to the quantitative decrease in nerve fibers in the skin, morphological changes such as axonal swelling, branching at the ends of nerve fibers, and the formation of fibers running parallel to the basement membrane can also be observed. These changes usually precede the reduction in nerve fiber density.

Skin biopsy plays an important role in the diagnosis of small-fiber neuropathy. This term refers to isolated damage to the small, thinly myelinated A-fibers and the unmyelinated C-fibers.  

Measuring the IENFD in a skin biopsy is a suitable diagnostic method with good reliability, high sensitivity (45–89%, depending on the study), and high specificity (88–97%).

Biopsy collection and immunohistochemistry

The biopsy was taken under local anesthesia by means of punch biopsy (3 mm diameter). The biopsy is usually performed on the skin of the thigh 20 cm below the iliac spine and on the skin of the lower leg 10 cm above the lateral malleolus.

After collection, the biopsies are placed in 2% paraformaldehyde lysine periodate solution and transported refrigerated to the laboratory. There they remain at 4 °C for 24 hours. Serial preparation in 50μm sections. And immunohistochemical preparation with anti-protein-gene-product 9.5 antibody (AbD Serotec, Martinsried, Germany, 1:1000). The intraepidermal nerve fibre density is determined according to the guidelines of the European Federation of Neurological Societies. The standard values determined by Devigili et al. for the thigh (>12.8 intraepidermal nerve fibres/mm skin surface area) and the lower leg (>7.6/mm) are used as limit values.

1. McCarthy BG et al (1995) Cutaneous innervations in sensory neuropathies: evaluation by skin biopsy. Neurology. 1995;45:1848–55.
2. Lauria G, Morbin M, Lombardi R, Borgna M, Mazzoleni G, Sghirlanzoni A, et al Axonal swellings predict the degeneration of epidermal nerve fibers in painful neuropathies. Neurology 61:631-6.
3. Gibbons CH et al (2006) The utility of skin biopsy for prediction of progression in suspected small fiber neuropathy. Neurology 66:256-258.
4. Lauria G et al (2005) EFNS guidelines on the use of skin biopsy in the diagnosis of peripheral neuropathy. Eur J Neurol 12:747-758.
5. Devigili G et al (2008) The diagnostic criteria for small fibre neuropathy: from symptoms to neuropathology. Brain 131:1912-1925.