Use of human intravenous immunoglobulin in lower motor neuron syndromes

Objective-To determine whether patients with the clinical phenotype of mult ifocal motor neuropathy but without the electrophysiological criteria for c onduction block would respond to intravenous immunoglobulin (IVIg). Methods-Ten patients were selected with a slowly progressive, asymmetric, l ower motor neuron disorder, and were treated prospectively with IVIg at a d ose of 2g/kg over 5 days. All subjects had neurophysiological testing to lo ok for evidence of conduction block before treatment. Muscle strength was a ssessed by MRC grades and hand held myometry, measuring pinch and grip stre ngth. A 20% increase in both pinch and grip myometry was considered a posit ive response. Results-In no patient was conduction block detected. Four of the 10 patient s showed a positive response to IVIg, with the best response occurring in t wo patients who presented with weakness but without severe muscle wasting. Three of the four responders have continued to receive IVIg for a mean peri od of 17 months (range 15-24 months), with continued effect. The response t o IVIg was not related to the presence of anti-GM1 antiganglioside antibodi es, but responders had a selective pattern of muscle weakness and normal (> 90% predicted) vital capacity. Conclusion-The findings suggest that a course of IVIg should be considered in patients with the clinical phenotype of multifocal motor neuropathy but without neurophysiological evidence of conduction block.