Clinical and neuropathological parameters affecting the diagnostic yield of nerve biopsy.

The value of nerve biopsy in the investigation of peripheral neuropathies is an important and controversial issue, partially obscured by the large variations in the diagnostic yield routinely reported for this procedure. The aim of this study was to evaluate the clinical and neuropathological parameters affecting the yield of nerve biopsy. We compared the experience of two independent neuropathology laboratories with different patient recruitment and neuropathological methods over 11 years (01/1987-12/1997). Clinicopathological correlations were studied retrospectively in 355 patients. Using the same criteria of evaluation, contributive biopsies accounted for 35.5% in one laboratory, and 47.3% in the other. Clinical parameters affecting the yield of nerve biopsy were: (a) the presumptive diagnosis at time of referral for biopsy; (b) the distribution of symptoms; and (c) the interval between disease onset and biopsy. Greater yield was associated with clinically suspected vasculitis, inflammatory demyelinating neuropathy or hereditary sensorimotor neuropathies. Contributive findings were more often reported with multifocal or asymmetrical presentations, and onset-to-biopsy interval of less than 6 months. The contribution of nerve biopsy varied according to neuropathological techniques: (a) serial sections on frozen. paraffin-embedded and resin-embedded material improved sensitivity for interstitial pathology: (b) combined muscle biopsy increased sensitivity in the detection of vasculitis; and (c) teasing of nerve fibers added critical information to other classical techniques in only 4/102 cases.