Intravenous immunoglobulin therapy in multifocal motor neuropathy - A double-blind, placebo-controlled study

We conducted a double-blind, placebo-controlled, study of 19 patients fulfi lling eligibility criteria for multifocal motor neuropathy with persistent conduction block. They were enrolled and divided into two groups: those who had never been treated previously with intravenous immunoglobulins (IVIg) (Group 1: 10 patients) and those who presented recurrent symptoms after pre viously successful treatment with IVIg (Group 2: nine patients). They were randomized prospectively to receive either IVIg or placebo at a dose of 500 mg/kg/day for 5 consecutive days, once a month for 3 months. At month 4, p atients found to be responders remained on the same treatment for the 3 fol lowing months, while nonresponders were switched to the alternative study d rug for the 3 following months. Clinical assessment was conducted with the MRC score in 28 muscles and a self-evaluation scale (five daily motor activ ities scored from 0 to 5). In Group 1, nine patients completed the study, o f whom initially four received IVIg and five placebo; four patients respond ed to IVIg (two at months 4 and 7, and a further two at month 7 after switc hing treatment at month 4), two patients responded to placebo at months 4 a nd 7, and three patients did not respond to either treatment. In Group 2,ni ne patients completed the study. Five patients first received IVIg and all responded at months 4 and 7. Four patients first received placebo and none responded at month 4; all were then switched to IVIg and three responded at month 7. When the 18 patients were considered together, seven out of the n ine patients who received IVIg first were responders at month 4, compared w ith two of the nine patients who received placebo first, a difference that was statistically significant (P = 0.03). On the other hand, there was no s ignificant difference in MRC score but a significant difference in the self -evaluation score, at month 4, between IVIg patients and placebo patients. Electrophysiological studies did not show significant differences at month 4 in motor parameters between IVIg patients and placebo patients. IgM anti- GM1 titres did not change significantly in patients treated with IVIg compa red with those who received placebo, between baseline, month 4 and month 7. However, of five patients who had significantly high anti-GM1 titres (>320 0) at baseline, four responded to IVIg. This trial confirms that IVIg is a promising therapeutic option for multifocal motor neuropathy.