Neuromuscular disorders affect the nerves that control certain muscles in your body. These muscles are called your voluntary muscles — they’re the muscles you can choose to move such as the ones in your arms, legs, or face.

Disorders that affect voluntary muscles can be genetically inherited (passed down from your parents) or may develop over time as a complication of certain health conditions such as an autoimmune disorder.

This article takes a look at the different types of neuromuscular disorders, what their symptoms include, and what treatments may help.

Your body is home to more than 650 voluntary or skeletal muscles. These muscles allow you to do things such as walk, talk, blink, and eat. Neuromuscular disorders disrupt your ability to control these muscles.

How do neuromuscular disorders disrupt your ability to control muscles?

The neurons (nerve cells) that help your brain control your voluntary muscles become damaged or even die off, leading to weakness or atrophy. Neuromuscular disorders may affect the peripheral nerves, the skeletal muscles, or the neuromuscular junction (where the nerves and muscles meet).

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Common neuromuscular disorders include:

  • Amyotrophic lateral sclerosis (ALS): This condition leads to the loss of nerve cells in the brain and spinal cord. Weakness in the muscles causes trouble with movement and speech. ALS may also eventually lead to issues with swallowing and breathing.
  • Charcot-Marie-Tooth disease (CMT disease): This group of disorders is inherited. Early symptoms include weakness in the lower limbs/feet and hands. CMT progresses slowly and may not affect a person’s life span.
  • Chronic inflammatory demyelinating polyneuropathy (CIDP): This condition leads to weakness in the extremities (arms/legs). It’s caused by autoimmune issues that damage the insulation surrounding the peripheral nerves (myelin sheath).
  • Guillain-Barré syndrome (GBS): This condition also affects the myelin sheath. Symptoms and progress vary by person, but it typically begins with weakness in the legs and spreads rapidly to the rest of the body. Similar to CIDP, the cause is likely the immune system attacking the peripheral nervous system.
  • Lambert-Eaton syndrome: This autoimmune condition leads to weakness and fatigue in the arm and leg muscles. It’s caused by antibodies that damage the voltage-gated calcium channels in the neuromuscular junction.
  • Multiple sclerosis (MS): This condition is also caused by the immune system attacking the myelin sheath around the peripheral nerves. It affects the brain, spinal cord, and optic nerves. People with MS have attacks that lead to either a progression of symptoms or periods of time where there are no new symptoms (stabilization).
  • Myasthenia gravis: This autoimmune condition is caused by damage to muscle receptors. It leads to muscle weakness throughout the body. Symptoms include weakness in the arms/legs, issues with the eyes and vision, and trouble with speaking and eating.
  • Peripheral neuropathy: This group of disorders affects nerves beyond the brain and spinal cord. It leads to weakness, pain, and numbness in the extremities (arms, legs, hands, feet, face, mouth, etc.).
  • Spinal muscular atrophy (SMA): This group of genetically inherited disorders causes symptoms such as hypotonia (decreased muscle tone) in the arms/legs, feeding issues, and breathing issues. Many forms start in infancy/childhood, but some begin in adulthood as well.

The symptoms you experience with a neuromuscular disorder vary by the disorder you have. The same goes with the severity of those symptoms. One person may have very mild symptoms while another person may have life threatening symptoms.

Likewise, the onset of symptoms can range from infancy to adulthood. The progress of symptoms may be slow, rapid, or even change over time.

Symptoms may include:

  • weakness in the muscles
  • wastage of the muscles
  • cramps in the muscles
  • stiffness (spasticity) in the muscles
  • pain in the muscles
  • difficulty breathing
  • difficulty swallowing
  • issues with balance and movement
  • trouble with vision

The cause of neuromuscular disorders depends on the specific disorder.

For some, such as ALS, the cause isn’t known. Others, such as CIDP and MS, are caused by autoimmune issues and, therefore, by whatever triggers the immune response.

Other disorders, such as SMA and CMT, may be inherited or caused by spontaneous gene mutations during reproduction.

Additional risk factors may include:

  • age
  • family history
  • smoking

To diagnose a neuromuscular disorder, a doctor or healthcare professional will first likely test your reflexes and look for signs such as loss of muscle tone (atrophy). From there, the following tests may help with diagnosis:

Neuromuscular disorders can’t be cured. Instead, treatment is prescribed to ease symptoms and slow the disease from getting worse.

Medications may include:

  • drugs to relieve muscle pain, weakness, cramps, and stiffness
  • drugs to address nerve impulses and strength in the muscles
  • immunosuppressants if a disorder is caused by autoimmune issues
  • high dose immunoglobulin therapy to build antibodies

Other treatments include:

  • physical therapy to restore muscle tone and work on motor skills
  • occupational therapy to learn new ways to go about daily tasks and save energy
  • surgery — with neuropathy — to relieve pressure on the nerves or — with myasthenia gravis — to remove the thymus

Each neuromuscular disorder and each person is unique. Some conditions may lead to only mild symptoms that don’t progress. Others may progress rapidly and become debilitating or even life threatening.

The good news is that treatment may slow the progression of some disorders. Therapies can also help with motor function and performing everyday tasks.

Researchers are also looking into new treatments to improve outcomes, such as using the drugs rasagiline, tirasemtiv, and mexiletine for ALS or using bone marrow transplants to treat mitochondrial neurogastrointestinal encephalomyopathy.

Can neuromuscular disorders affect children?

Yes. Children can develop neuromuscular disorders, the most common of which is Duchenne muscular dystrophy. Other common disorders in children include SMA, myotonic dystrophy (a form of muscular dystrophy), and CMT disease. These conditions are usually genetic, so children are born with them.

Can neuromuscular disorders affect breathing?

Neuromuscular disorders may affect breathing for some people. You may first notice shortness of breath at night or when lying down flat. The three main breathing issues associated with neuromuscular disorders are nocturnal (nighttime) hypoventilation, obstructive sleep apnea, and central sleep apnea.

Can a COVID-19 vaccine cause a neuromuscular disease?

Researchers can’t currently establish a firm link between neuromuscular disorders and the COVID-19 vaccine. In one study, eight people developed neuromuscular disorders — including GBS — in the weeks following their vaccination. More research is needed to determine if there’s a relationship or if it’s coincidental.

Are people with neuromuscular disorders at a higher risk of COVID-19 (or for developing a more severe case of COVID-19)?

Researchers share that some people with neuromuscular disorders may face certain challenges with COVID-19. For example, people who are taking immunosuppressants may be at higher risk of illness. And, once sick, the illness may make breathing tougher for people who are already dealing with breathing issues.

That said, the researchers point out that increased risk of COVID-19 and severe complications will depend greatly on:

  • the type of disorder a person has
  • the treatments they’re using
  • other factors such as age and other health conditions

Make an appointment with a doctor if you experience symptoms associated with neuromuscular disorders such as weakness or tingling in your arms or legs.

The sooner you receive a diagnosis, the sooner you can get treatment. While there’s no cure for these disorders, treatment and different therapies can help slow the progression of disease and improve your quality of life.