OBJECTIVE: To test the hypothesis that patients with rheumatoid arthritis (RA) have clinical or subclinical evidence of peripheral neuropathy or myopathy. METHODS: We studied 40 seropositive women with RA, mean age 46.6 years (SD 6.4), and 56 healthy controls, mean age 43.0 years (SD 9.1). Patients had a mean disease duration of 13.0 years (SD 7.8). We performed electromyographic examination of 4 muscles [extensor digitorum communis (EDC), biceps brachii (BB), vastus lateralis (VL), and tibialis anterior (TA)] on the right side in both groups. Quantitative data included percentage of polyphasic potentials, motor unit potential amplitude, area, duration, turns, and number of polyphasic potentials. RESULTS: There were statistically significantly higher proportions of polyphasic potentials in 3 muscles in patients compared with controls. Mean number of phases in EDC was 4.6 (SD 0.4) in the patients and 4.1 (0.5) in controls (p = 0.0001). The values for the VL were 4.1 (SD 0.4) in patients compared with 3.6 (0.4) in controls (p = 0.0001), and in the TA 4.5 (SD 0.5) versus 4.0 (0.4) (p = 0.0001). We also found significantly increased duration of motor unit potentials in the VL and TA of patients. The amplitudes of motor unit action potentials were not significantly different in the 2 groups. CONCLUSION: The study reveals an increased prevalence of neurogenic but not myogenic changes in patients with RA compared with controls.
OBJECTIVE: To test the hypothesis that patients with rheumatoid arthritis (RA) have clinical or subclinical evidence of peripheral neuropathy or myopathy. METHODS: We studied 40 seropositive women with RA, mean age 46.6 years (SD 6.4), and 56 healthy controls, mean age 43.0 years (SD 9.1). Patients had a mean disease duration of 13.0 years (SD 7.8). We performed electromyographic examination of 4 muscles [extensor digitorum communis (EDC), biceps brachii (BB), vastus lateralis (VL), and tibialis anterior (TA)] on the right side in both groups. Quantitative data included percentage of polyphasic potentials, motor unit potential amplitude, area, duration, turns, and number of polyphasic potentials. RESULTS: There were statistically significantly higher proportions of polyphasic potentials in 3 muscles in patients compared with controls. Mean number of phases in EDC was 4.6 (SD 0.4) in the patients and 4.1 (0.5) in controls (p = 0.0001). The values for the VL were 4.1 (SD 0.4) in patients compared with 3.6 (0.4) in controls (p = 0.0001), and in the TA 4.5 (SD 0.5) versus 4.0 (0.4) (p = 0.0001). We also found significantly increased duration of motor unit potentials in the VL and TA of patients. The amplitudes of motor unit action potentials were not significantly different in the 2 groups. CONCLUSION: The study reveals an increased prevalence of neurogenic but not myogenic changes in patients with RA compared with controls.