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