Multifocal motor neuropathies with conduction block: Long-term follow-up of ten patients treated with Mg

Multifocal motor neuropathy (MMN) with conduction block responds to high-dose IV polyvalent immunoglobulins (IVIg) over the short term, but several studies have demonstrated a long-term increase in the degree of axonal degeneration and the number of conduction blocks, factors indicating a poor prognosis. The objective of this study was to evaluate the long-term effect of IVIg on clinical and neurophysiological parameters. Methods: We reviewed the records of ten patients who had initially responded well to IVIg and received regular long-term treatment. The parameters studied were muscular strength, motor function status (modified Rankin scale), as well as the number and progression of conduction blocks and the degree of axonal degeneration. Patients were followed up for a mean of 7.25 years (range, 3.5-12). They were all initially treated with 2 g IgIV/kg in 5 days every 4 weeks for 3 months. Maintenance therapy was administered every 4 weeks with dose adjustment to prevent muscular strength deterioration. Results: We noted a significant and persistent improvement in muscular strength and in the Rankin motor function score over the long term, with no escape phenomenon. The number of conduction blocks and the degree of axonal degeneration decreased markedly. Conclusion: IVIg treatment remains effective over the long term in MMN. These conclusions differ from those of other authors in earlier studies, but our patients were treated with significantly higher doses of IVIg. These results have important implications for long-term treatment of patients with MMN.