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Sural nerve biopsy has been a well established diagnostic procedure for the investigation of peripheral neuropathies for over 30 years and the techniques and indications were described by Dyck and Loufgren at the Mayo Clinic1 and Thomas.2 Although indications and guidelines for sural nerve biopsy have been described3 and retrospective studies of its value have been published, the first prospective study of the procedure to determine its usefulness in influencing diagnosis and treatment and the complications is reported in the paper by Gabrielet al 4 in this issue (pp442–446).
Full laboratory investigations and neurophysiological studies should be undertaken before biopsy is considered and it is of primary importance that the surgeon is experienced in the procedure and that the tissue can be evaluated by a laboratory experienced in the techniques of light and electron microscopy, teased fibres studies, and the use of immunohistochemical methods of staining. Certain conditions have characteristic histopathological appearances including most cases of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), CMT1, amyloid neuropathy, vasculitis, sarcoidosis, giant axonal neuropathy, hexacarbon neuropathy, IgM kappa paraproteinaemic neuropathy, metachromatic leukodystrophy, and Krabbe's and Fabry's diseases but in many conditions the appearance of axonal degeneration or mixed axonal degeneration and demyelination is non-specific and nerve biopsy assists the diagnosis only by exclusion.
Sural nerve biopsy has complications of pain, infection, sensory loss, and delayed wound healing and should only be undertaken in cases of peripheral neuropathy where there are good prospects of its significantly assisting in the diagnosis, as was the case in the study of Gabriel et al,4 which examined the value of biopsy in 50 consecutive patients. In their series biopsy was performed only when it might have disclosed a treatable cause and therefore many hereditary neuropathies with characteristic pathology would have been excluded. In seven cases the prebiopsy diagnosis was altered by the biopsy and in 60% of cases an independent neurologist judged that it had been helpful, particularly in mononeuritis multiplex and demyelinating neuropathies.
It is clear that sural nerve biopsy has an important place in the diagnosis of peripheral nerve disease and, in the case of vasculitic neuropathy confined to peripheral nerves, it is the only certain way of making the diagnosis of the treatable condition. The value of biopsy needs to be weighed against the complications of persistent pain at the biopsy site (33%), infection (15%), and patient dissatisfaction with the procedure (27%).