What are the other Names for this Condition? (Also known as/Synonyms)

• MMN (Multifocal Motor Neuropathy)
• MMNCB (Multifocal Motor Neuropathy With Conduction Block)
• Multifocal Motor Neuropathy With Conduction Block (MMNCB)

What is Multifocal Motor Neuropathy? (Definition/Background Information)

• Multifocal Motor Neuropathy (MMN) is a rare neuropathy characterized by progressive, asymmetric muscle weakness and atrophy (wasting). Signs and symptoms include weakness in the hands and lower arms; cramping; involuntary contractions or twitching; and atrophy of affected muscles
• Multifocal Motor Neuropathy is thought to be due to an abnormal immune response, but the underlying cause is not clear. Most people treated with intravenous immune globulin (IVIG) have rapid improvement in weakness, but maintenance IVIG is usually required for sustained improvement
• The exact underlying cause of Multifocal Motor Neuropathy is poorly understood. It is considered an immune-mediated disorder (due to an abnormal immune systemresponse), both because IVIG therapy improves symptoms, and many patients have anti-GM1 antibodies. Research to further understand the cause of MMN is underway
• We are not aware of any evidence that Multifocal Motor Neuropathy is inherited or of any reports of familial cases (occurring in more than one person in a family). Furthermore, to our knowledge, no specific genes known to be associated with MMN have been identified

(Source: Multifocal Motor Neuropathy; Orphanet, National Institute of Health and Medical Research (INSERM), Paris.)

Who gets Multifocal Motor Neuropathy? (Age and Sex Distribution)

• Multifocal Motor Neuropathy is a rare disorder. The presentation of symptoms may occur in adulthood
• Both males and females may be affected
• Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Multifocal Motor Neuropathy? (Predisposing Factors)

• Currently, no risk factors have been clearly identified for Multifocal Motor Neuropathy

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Multifocal Motor Neuropathy? (Etiology)

• The cause of Multifocal Motor Neuropathy is not known at the present time
• Owing to the presence of anti-GM1 antibodies in affected individuals and response to intravenous immunoglobulin treatment, it has been suggested that Multifocal Motor Neuropathy may be caused by an abnormal immune system response

What are the Signs and Symptoms of Multifocal Motor Neuropathy?

The signs and symptoms of Multifocal Motor Neuropathy may include:

Very frequently present symptoms in 80-99% of the cases include progressive distal muscle weakness.

Frequently present symptoms in 30-79% of the cases:

• Abnormality of ganglioside metabolism 
• Fasciculations
• Functional motor deficit 
• Increased CSF protein 
• Limb muscle weakness
• Limited wrist extension 
• Motor conduction block 
• Muscle cramps 
• Reduced tendon reflexes 
• Weakness of long finger extensor muscles

(Source: Multifocal Motor Neuropathy; Genetic and Rare Disease Information Center (GARD) of National Center for Advancing Translational Science (NCATS), USA.)

How is Multifocal Motor Neuropathy Diagnosed?

Multifocal Motor Neuropathy is diagnosed on the basis of the following information:

• Complete physical examination
• Thorough medical history evaluation
• Assessment of signs and symptoms
• Laboratory tests
• Imaging studies
• Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Multifocal Motor Neuropathy?

The complications of Multifocal Motor Neuropathy may include:

• Resistance to IVIG treatment
• Progressive deterioration of symptoms
• Impact on quality of life

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Multifocal Motor Neuropathy Treated?

The treatment for Multifocal Motor Neuropathy may include:

• Intravenous immune globulin (IVIG) administration
• Immune-suppressing agents, such as cyclophosphamide, in individuals who have stopped responding (developed resistance) to IVIG therapy

How can Multifocal Motor Neuropathy be Prevented?

• At the present time, no preventive methods or guidelines are available for the prevention of Multifocal Motor Neuropathy 
• Active research is currently being performed to explore the possibilities for treatment and prevention of disorders such as Multifocal Motor Neuropathy
• Regular medical screening at periodic intervals with tests and physical examinations are recommended

What is the Prognosis of Multifocal Motor Neuropathy? (Outcomes/Resolutions)

• The prognosis of Multifocal Motor Neuropathy is dependent upon the severity of the signs and symptoms and associated complications, if any
• Individuals with mild conditions have better prognosis than those with severe symptoms and complications
• Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Multifocal Motor Neuropathy:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/