Evaluation of simultaneous muscle and nerve biopsies for the diagnosis of neuromuscular diseases.

Skeletal muscle and peripheral nerve are occasionally simultaneously biopsied with the goal of increasing diagnostic yield in patients with an uncertain clinical diagnosis or in cases where the pathology is known to be focal or multifocal (eg, vasculitis or amyloidosis). The purpose of the present study is to evaluate the diagnostic utility of performing simultaneous muscle and nerve biopsies. A surgical pathology database was searched from 1993 to 2011 to identify patients who had concomitant skeletal muscle and peripheral nerve biopsies. Demographic and pathologic findings were recorded for all cases. Two hundred eighty-seven patients were included for study. There were 161 (56%) males and 126 (44%) females with a mean age at the time of biopsy of 51 years. The most commonly sampled sites were gastrocnemius muscle (n=186, 65%) and sural nerve (n=264, 92%). Most cases (n=166, 58%) were found to have a definitive diagnosis in either muscle or nerve. Of the cases with definitive diagnoses, 44 (27%) were based off the muscle only, 100 (60%) off the nerve only, and 22 (13%) had a definitive diagnosis in both the muscle and nerve. The most common diagnoses made on muscle biopsy alone were denervation atrophy (n=34) and inflammatory myopathy (n=7). The most common diagnosis made on nerve biopsy alone was a moderate or greater degree of axonal loss (n=82). Vasculitis was found in muscle in 2 cases, in the nerve in 14 cases, and both muscle and nerve in 4 cases. Amyloidosis was exclusive to muscle in no cases, was seen in nerve only in 1 case, and was found in both muscle and nerve in 4 cases. Performing simultaneous muscle and nerve biopsies can improve diagnostic yield (from 8% to 58% in the current study).