Investigation of oxidative stress in patients with multifocal motor neuropathy

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.

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.

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.

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.