Treatments that suppress or modify the immune system for multifocal motor neuropathy

Review question

We reviewed the evidence for the benefits and harms of treatments that suppress or modify the immune system in multifocal motor neuropathy (MMN).

Background

MMN is a rare condition causing progressive weakness of the limbs, especially the hands and arms. This disorder is believed to be driven by an immune-based process. The usual treatment is infusion of immunoglobulin (antibodies purified from the blood) into a vein (IVIg). This is expensive, needs to be repeated every few weeks and is not always completely effective. Immunosuppressive drugs (drugs that suppress immune responses) such as cyclophosphamide, azathioprine, ciclosporin, interferon beta-1a, mycophenolate mofetil and rituximab have been tried as initial or add-on treatments.  

Study characteristics

We found only one randomised controlled trial (RCT), of a drug called mycophenolate mofetil. The trial involved 28 people with MMN.

Key results and quality of the evidence

The trial provided moderate quality evidence that mycophenolate mofetil, when used with IVIg, did not reduce the requirement for IVIg or improve muscle strength of trial participants with MMN. No serious side-effects were observed. The risk of bias was low in this study. New RCTs of other immunosuppressive drugs are needed to identify beneficial treatments for MMN.

The evidence is current to September 2014.

Authors' conclusions: 

According to moderate quality evidence, mycophenolate mofetil did not produce significant benefit in terms of reducing need for IVIg or improving muscle strength in MMN. Trials of other immunosuppressants should be undertaken.

Read the full abstract...
Background: 

Multifocal motor neuropathy (MMN) is characterised by progressive, predominantly distal, asymmetrical limb weakness and usually multiple partial motor nerve conduction blocks. Intravenous immunoglobulin (IVIg) is beneficial but the role of immunosuppressive agents is uncertain. This is an update of a review first published in 2002 and previously updated in 2003, 2005, 2008 and 2011.

Objectives: 

To assess the effects of immunosuppressive agents for the treatment of multifocal motor neuropathy.

Search strategy: 

On 22 September 2014 we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, EMBASE and LILACS for trials of MMN. We also searched two trials registers for ongoing studies.

Selection criteria: 

We planned to include randomised controlled trials (RCTs) and quasi-RCTs. We considered prospective and retrospective case series and case reports in the Discussion.

Data collection and analysis: 

Two review authors searched the titles and abstracts of the articles identified and extracted the data independently.

Main results: 

Only one RCT of an immunosuppressive or immunomodulatory agent has been performed in MMN. This study randomised 28 participants and showed that mycophenolate mofetil, when used with IVIg, did not significantly improve strength, function or reduce the need for IVIg. No serious adverse events were observed. The study was deemed at low risk of bias. We summarised the results of retrospective and prospective case series in the discussion.

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