INVESTIGATION OF OXIDATIVE STRESS IN PATIENTS WITH MULTIFOCAL MOTOR NEUROPATHY

Background and purpose - Multifocal motor neuropathy (MMN) is a rare, immune-mediated illness attacking exclusively motor nerves. It is known that oxidative stress is present in peripheral neuropathies, but it has not been investigated MMN. Methods - We measured in our prospective study the L-arginine, symmetric and asymmetric dimethylarginine (SDMA, ADMA) serum concentrations of 10 patients and 10 controls before and after intravenous immunoglobulin treatment (IVIG), as markers of the L-arginine/NO pathway involved in chronic inflammation and oxidative stress. The functions of motor nerves were tested in all patients and the serum antiganglioside antibody levels were detected, as well. Results - MMN patients showed significantly higher ADMA (p = 0.0048; 0.98 and 0.63, respectively) and SDMA levels (p = 0.001; 0.88 and 0.51, respectively) than healthy controls, while L-arginine was not different. Controlling for the covariant age, ADMA (B = -0.474; p = 0.041) or SDMA (B = -0.896; p < 0.0005) serum levels proved to be the significant predictors of the presence of MMN. IVIG therapy decreased significantly ADMA concentrations (p = 0.025; 0.98 and 0.84, respectively) and showed a trend to reduce SDMA levels (p = 0.1; 0.88 and 0.74, respectively). The dimethylamine levels did not correlate with the number of affected nerves, disease duration, or the presence of ganglioside antibodies. The conduction block-related peripheral motor dysfunction improved right after the IVIG treatment. Conclusion - Dimethylamine levels are elevated in the serum and are responsive to IVIG therapy in MMN. These findings support the presence of oxidative stress in MMN.