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, a symmetric, lower motor neuron weakness and is probably immune-mediated. Mg treatment has been shown to have beneficial effects in several open-label s tudies and in one small controlled trial. However, larger randomized contro lled studies are lacking. Methods: The authors recruited 16 patients with M MN. All subjects were given each of two treatments (Mg [0.4 g/kg/d for 5 co nsecutive days] or placebo [dextrose or saline]) that were assigned accordi ng to a randomized, crossover design under double-blind conditions. Patient s were evaluated before and about 28 days after trial treatment for subject ive functional improvement, neurologic disability score, grip strength, dis tal and proximal compound muscle action potential amplitude, and conduction block. Results: Subjective functional improvement with Mg treatment was ra ted 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. T he neurologic disability score improved by 6.7 +/- 3.3 points with Mg treat ment, whereas it decreased by 2.1 +/- 3.0 with placebo (p = 0.038). Grip st rength 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 bloc k 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 pat ients with Mg but not placebo. Conclusion: Mg improved conduction block as well as subjective and objective clinical measures of function in patients with MMN.