Superficial peroneal nerve/peroneus brevis muscle biopsy in vasculitic neuropathy

Objective: To determine the sensitivity and specificity of superficial pero neal nerve (SPN)/peroneus brevis muscle (PBM) biopsy in a cohort of patient s with suspected peripheral nerve vasculitis. Background: In patients with suspected vasculitic neuropathy, combined nerve and muscle biopsies have be en advocated as a way to increase the diagnostic yield, but the sensitivity and specificity of this approach have not been evaluated. Pathologic predi ctors of biopsy-proven peripheral nerve vasculitis have also not been analy zed in a systematic fashion. Methods: The clinical, laboratory, and patholo gic data for all patients undergoing SPN/PBM biopsy for possible vasculitis from 1986 through 1996 were analyzed. Biopsies were classified as positive , negative, or suspicious for vasculitis. Patients were then divided into v asculitis and nonvasculitis cohorts by final clinical diagnosis. Results: O f 70 SPN/PBM biopsies, 22 (30%) showed definite vasculitis; nerve was diagn ostic in 90% (n = 20) and muscle in 50% (n = 11). Nerve biopsy had a higher yield than muscle in patients with nonsystemic vasculitic neuropathy (p = 0.0047) but not in those with systemic vasculitis. The estimated sensitivit y of a positive SPN/PBM biopsy for vasculitis was 60%. Considering biopsies either positive or suspicious for vasculitis increased the sensitivity to 86% with a corresponding specificity of 85%. Pathologic features associated with necrotizing vasculitis were muscle fiber necrosis/regeneration (relat ive risk 18.1; 95% CI 3.4 to 96.1), predominant axonal nerve pathology (>8. 8; >1.0 to 77.4), Wallerian-like degeneration (5.6; 1.4 to 21.9), and asymm etric nerve fiber loss (4.6; 1.4 to 15.9). Conclusions: These findings esta blish the yield, sensitivity, and specificity of SPN/PBM biopsy for diagnos ing vasculitic neuropathy and validate the use of suggestive pathologic fea tures for diagnosing cases lacking definite necrotizing vascular changes.