Multifocal Motor Neuropathy

Written by Martha Anne Tudor
Medically Reviewed by Melinda Ratini, MS, DO on June 24, 2025
6 min read

Multifocal motor neuropathy (MMN)  is a rare disease that causes slowly worsening muscle weakness, mainly in your hands, arms, and legs. It affects your body's motor nerves, which control your muscles. MMN makes it hard for your motor nerves to send electrical signals that move your body. 

It's a chronic condition that's not curable. But treatment is usually very effective, helping slow down the disease and improve your muscle function. Over time, you may have a hard time doing daily tasks, such as typing on a keyboard or getting dressed. But with treatment, you may be able to work and stay active for many years after your diagnosis.

It's most often diagnosed between the ages of 40 and 50. Anyone aged 20-80 can get it, though it's been diagnosed in children in very rare cases. It's more common in men, and they're usually diagnosed at a younger age than women.

Experts don't know exactly what causes MMN, but they know you're not born with it. It's an autoimmune disease, meaning your immune system mistakenly attacks your nerve cells as if they were invaders. Researchers are working to find out why it happens.

You may first notice symptoms in your hands and lower arms. They may feel weak, cramp up, or twitch in ways you can't control. Those symptoms may start in specific parts of your arm or hand, such as your wrist or finger. They're often more severe on one side of your body. MMN may eventually affect your legs.

This condition isn't painful. You can feel with your hands and arms because your sensory nerves aren't affected. Your symptoms will likely get worse with age.

Doctors often mistake MMN for amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease. These conditions have similar symptoms. But unlike ALS, MMN is treatable.

You may need to see a neurologist, a medical doctor who specializes in problems with your brain and nervous system. They'll give you a physical exam and ask questions about your symptoms. They may ask:

  • Which muscles are giving you trouble?
  • Is it worse on one side of your body?
  • How long have you been feeling this way?
  • Do you have numbness or tingling?
  • Does anything make your symptoms better? What makes them worse?

They'll do nerve and blood tests to rule out other conditions. They may include:

Nerve conduction study (NCS). This test measures how fast electrical signals travel through your nerves. Usually, your doctor puts two sensors on the skin over one of your nerves: one to transmit a small electric shock and the other to record the activity. They repeat the test on other nerves if they think more than one is involved.

Needle electromyography (EMG). Your doctor will put electrodes on your arms. They have small needles that go into your muscle. They're attached by wires to a machine that measures electrical activity in your muscles. Your doctor will ask you to slowly flex and relax your arms so the machine can record the activity. They'll do this test at the same time as the NCS.

B lood test. This will look for GM1 antibodies, part of your body’s immune system. Some people with MMN have higher levels of them. If you have a lot of these antibodies, chances are you have MMN. You can still have it even if you don't have a lot of the antibodies.

Here are some questions you might want to ask your doctor:

  • How will MMN affect me?
  • Do I need treatment?
  • What kinds are available?
  • How will they make me feel?
  • Will I be able to work?
  • What happens if the treatment doesn't help?
  • Are there any clinical trials I can join?
  • Are there any activities I won't be able to do?

If your symptoms are very mild, you may not need any treatment. But if you do, your doctor may prescribe a medication called intravenous immunoglobulin (IVIG). It's given directly into one of your veins through an IV. You'll usually have this done in your doctor's office, but you can learn to do it at home.

If IVIG works, you should feel your muscle strength improve in three to six weeks. The effects wear off over time, so you need to keep having treatments. Most people with MMN have it once a month, but you may need it more or less often.

IVIG doesn't have many side effects, but it's expensive.

Doctors are testing ways to give it like a regular shot, but this method isn't yet available for everyone.

If IVIG doesn't work, your doctor may try a drug called cyclophosphamide (Cytoxan), which is also used to treat certain types of cancer. It controls symptoms by slowing down your immune system. Unlike immunoglobulin, cyclophosphamide can have severe side effects, so doctors try not to use it.

Therapeutic massages, heat therapy, physical therapy, ultrasound, electrical stimulation, and trigger point injections may also help. Talk to your doctor about whether any of these could help you.

Also, talk to your doctor about ongoing clinical trials to see if you're a candidate.

Healthy lifestyle habits and social support can boost your overall well-being and quality of life when living with MMN.

Protect your emotional and mental health by managing your stress and getting professional mental health help when needed. Try to follow a healthy diet, get enough quality sleep, manage your fatigue, and do gentle, low-impact exercises. Talk to your doctor about safe exercises before starting a new routine. Getting help with daily activities, if you need it, also boosts your sense of health and wellness. Join a support group to connect with others and get helpful advice.

Early diagnosis and care are key to staying active and able to do routine tasks. MMN rarely shortens your lifespan. Many people with this condition are able to continue most or at least some of their normal activities.

Your journey with MMN depends on factors such as when you were diagnosed, which muscles are affected, whether you stick with treatments, and whether you follow a healthy lifestyle. Possible issues include trouble eating, typing, writing, dressing, and doing other daily tasks. If your leg muscles are affected, you could have trouble walking. Some people with severe MMN have trouble in all these areas.

To learn more about multifocal motor neuropathy, visit the web sites of the Neuropathy Action Foundation, the Neuropathy Association, or the GBS-CIDP (Guillain-Barré syndrome-chronic inflammatory demyelinating polyneuropathy) Foundation International.

MMN is a rare, chronic disease that causes slowly worsening muscle weakness, mainly in your hands, arms, and legs. It's not curable, but it's treatable. It probably won't shorten your life. Experts don't know what causes it, but they know it's an autoimmune disease you're not born with. It affects more men than women, usually between the ages of 40 and 50. Early diagnosis and treatment, and following a healthy lifestyle, are keys to staying active and independent.

What's the difference between MMN and MND?

MMN and motor neuron disease (MND) can have similar symptoms. But the main difference is that MND affects groups of spinal nerves, while MNM affects single nerves.

What's the difference between ALS and MMN?

Both have similar symptoms, but ALS isn't treatable, while MMN is. 

What are the first symptoms of MMN?

Weakness in your hands and arms is a common first symptom.

What are the criteria for MMN diagnosis?

Your doctor will rule out other possible conditions. They'll look at your medical history and give you a physical exam. They'll also do blood and nerve tests, using the results to help make a MMN diagnosis. 

What's the blood test for MMN?

It's a test that looks at GM1 antibodies in your blood. The amount you have many indicate you have MMN, but it may not. 

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