Multifocal motor neuropathy improved by IVIg - Randomized, double-blind, placebo-controlled study

Objective: To determine the effect of TV immunoglobulin (Mg) on neurologic function and electrophysiologic studies in multifocal motor neuropathy with conduction block (MMN). Background: MMN is characterized by progressive, asymmetric, lower motor neuron weakness and is probably immune-mediated. Mg treatment has been shown to have beneficial effects in several open-label studies and in one small controlled trial. However, larger randomized controlled studies are lacking. Methods: The authors recruited 16 patients with MMN. All subjects were given each of two treatments (Mg [0.4 g/kg/d for 5 consecutive days] or placebo [dextrose or saline]) that were assigned according to a randomized, crossover design under double-blind conditions. Patients were evaluated before and about 28 days after trial treatment for subjective functional improvement, neurologic disability score, grip strength, distal and proximal compound muscle action potential amplitude, and conduction block. Results: Subjective functional improvement with Mg treatment was rated as dramatic or very good in nine patients, moderate in one, mild in one, and absent in five patients. This improvement was absent after placebo. The neurologic disability score improved by 6.7 +/- 3.3 points with Mg treatment, whereas it decreased by 2.1 +/- 3.0 with placebo (p = 0.038). Grip strength on the weaker side was increased by 6.4 +/- 1.9 kg with Mg treatment; it decreased by 1.0 +/- 0.8 kg with placebo (p = 0.0021). Conduction block worsened by 12.98 +/- 6.52 % with placebo, but improved by 12.68 +/- 5.62 % with Mg treatment (p = 0.037). Conduction block was reversed in five patients with Mg but not placebo. Conclusion: Mg improved conduction block as well as subjective and objective clinical measures of function in patients with MMN.