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Multifocal Motor Neuropathy The Long-term Treatment of Multifocal Motor Neuropathy with Intravenous Immunoglobulin Leonard H van den Berg Professor of Neurology, Rudolf Magnus Institute of Neuroscience, Department of Neurology, University Medical Centre Utrecht, The Netherlands Abstract Multifocal motor neuropathy (MMN) is a rare, purely motor neuropathy. It is a progressive disorder, most patients eventually developing severe fatigue and weakness in the arm muscles that severely impair daily functioning and quality of life. Unlike other motor neuropathies such as motor neurone disease, MMN is treatable with regular infusions of intravenous immunoglobulin (IVIg). Four double-blind, randomised, placebo-controlled studies have shown that in the short term, IVIg significantly improves muscle strength and disability in more than 70 % of patients. The 11 observational studies reviewed in this article confirm that long-term maintenance treatment with IVIg maintains clinical improvement compared to pre-treatment baseline in most patients. Infusions are generally well tolerated, but regular monitoring and re-evaluation of the IVIg maintenance regimen is essential, as most patients need progressive increases in dosage or reduced intervals between infusions to maintain their response to treatment. In the absence of accepted predictive markers, maintenance IVIg should be individualised, based on each patient’s initial response, disability and the interval between the first infusion and decline in muscle strength. Keywords Multifocal motor neuropathy, intravenous immunoglobulin, maintenance, treatment Disclosure: Leonard H van den Berg has received a travel grant and honoraria from Baxter International Inc. Received: 5 March 2012 Accepted: 21 May 2012 Citation: European Neurological Review, 2012;7(2):128–33 Correspondence: Leonard H van den Berg, Department of Neurology G03.228, PO Box 85500, 3508 GA Utrecht, The Netherlands. E: Support: The publication of this article was funded by Baxter Innovations GmbH. The views and opinions expressed are those of the author and not necessarily those of Baxter Innovations GmbH. Multifocal motor neuropathy (MMN) is a rare, purely motor neuropathy with a prevalence of approximately 0.6 per 100,000 and a median age of onset of 40 years. 1 Men are more likely than women to be affected, in a ratio of 2.7:1 and are usually diagnosed at an earlier age. 1 Patients with MMN typically present with asymmetrical, predominantly distal limb weakness that follows individual nerves. There is no apparent sensory loss and weakness usually starts in the forearm or hand muscles, though the first symptoms may occur in the distal leg and upper arm. Respiratory and bulbar muscles are unaffected and patients have a normal life expectancy. However, since MMN is a progressive disorder, most patients eventually develop severe fatigue and weakness in the arm muscles, resulting in disability that can seriously impair daily functioning and quality of life. Unlike other motor neuropathies such as motor neurone disease (MND), MMN is treatable with intravenous immunoglobulin (IVIg). 2 Most patients require regular infusions in order to maintain clinical response and the aim of this review is to consider the effectiveness and safety of long-term or maintenance treatment of MMN with IVIg. Method The terms ‘multifocal motor neuropathy’, ‘treatment’, ‘long term’, ‘maintenance’ and ‘IVIg’ were used to conduct a PubMed search of articles published in English language journals between 1 January 1980 and 31 December 2011 (see Table 1). Papers were excluded if 128 they were single case reports, or were superseded by subsequent publications following up the same group of patients. Results The manual search of the results of the PubMed literature search identified a total of 14 studies concerning the long-term or maintenance treatment of MMN with IVIg. Three papers were excluded: • a case report in one patient; 3 • a publication concerning six patients included in a subsequent, larger study; 4,5 • and a study of dose titration in patients on maintenance IVIg. 6 The remaining 11 studies listed in Table 2 were included in the analysis. 1,5,7–15 All were retrospective, observational studies, except for one cross-sectional, descriptive study. Patient Demographics The 11 studies included a total of 297 patients who, except 10 of them, 15 were treated at centres in Europe. One study of long-term home IVIg treatment included 26 patients with MMN, but did not provide demographic information. 11 Of the 271 patients included in the remaining 10 studies, 1,5,7–10,12–15 183 (67.53 %) were male. Five studies 5,8,13,14 reported the age of onset of MMN: the lowest median age of onset was 36.5 (21–57) years 14 and the highest was 48 (32–59) years. 15 © TOUCH BRIEFINGS 2012