The long-term effect of intravenous immunoglobulin treatment in multifocal motor neuropathy

We studied the long-term effect of intravenous immuno-globulin (IVIg) treatment in seven patients with multifocal motor neuropathy. In six patients, treatment with a fill IVIg course (0.4 g/kg for 5 consecutive days) improved muscle strength but for not longer than 12 weeks. These patients received IVIg maintenance treatment consisting of one infusion every week for 2-4 years. One patient in whom the effect of the initial full IVIg treatment lasted for more than 1 year received incidental IVIg treatment when muscle strength deteriorated. In all patients IVIg treatment had a beneficial effect on most muscle groups during the follow-up period. However in three of the seven patients muscle strength deteriorated during IVIg maintenance treatment in four of the 28 muscle groups that had initially shown an improvement of muscle strength after the start of IVIg treatment and in two muscle groups with normal strength at the start of IVIg treatment. The electrophysiological follow-up studies indicated that there was an improvement of conduction block, but also that there were new sites of conduction block and ongoing axonal degeneration during IVIg maintenance treatment.