Nerve biopsy--some comments on procedures and indications.

Nerve biopsy is most often a final step in the evaluation of patients with peripheral neuropathy. The procedure should always be expected to result in varying degree of sensory loss within the innervation area of the biopsied nerve and chronic pain in the area may also occur. Therefore appropriate informed consent must be obtained and a weighing of such side effects and benefits for the patient, particularly therapeutical consequences, should be seriously considered before the procedure is performed. The surgical procedure and the processing in the laboratory of the nerve material must hold a high standard at all levels. Nerve biopsy should not be performed before adequate clinical, electrophysiological and laboratory investigations have been performed. The choice of nerve is important, but in most instances the sural nerve is biopsied, although the superficial peroneal nerve is also an option and allows an easy access to muscle biopsy in the same procedure. Laboratories performing nerve biopsies should have the facilities and expertise to prepare and evaluate fixed and frozen sections (paraffin, cryostat and epoxy-sections) and teased fibers, and also to perform light and electron microscopy and immunohistochemistry. Although not routinely used, the option of morphometry should be available as well. We recommend that properly trained technicians start the processing procedures in the operating room and, if feasible, even in hospitals outside that of the hospital with nerve laboratory. We also prefer routine use of teased fiber analysis as this visualizes in an excellent way pathological processes like axonal degeneration, demyelination and remyelination as well as other features. Evaluation of small fiber neuropathy is rarely an indication for nerve biopsy and should be investigated with skin biopsy and visualization and quantification of intraepidermal nerve fibers. Investigation of inflammatory neuropathy, particularly to demonstrate nerve vasculitis, is the main indication of nerve biopsy.