Multiple sclerosis (MS) and myasthenia gravis (MG) are autoimmune diseases that occur when the immune system attacks the nervous system. These two diseases cause recurrent episodes of dysfunction due to inflammation, often without permanent damage.

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MS occurs when there is damage to the myelin sheath that protects cells of the central nervous system (CNS), causing a disruption in nerve signaling to and from the brain. This can result in widespread symptoms due to the involvement of different parts of the nervous system.

MG occurs when the immune system’s antibodies attack the communication system between the nerves and muscles, leading to muscle weakness and fatigue.

This article will examine the difference between MS and MG, including differences in their symptoms, causes, treatment, diagnosis, and outlook.

Below is a general overview of MS in comparison with MG.

Multiple sclerosis

MS is a result of the body attacking the myelin sheath that surrounds and protects the CNS, which includes the brain and spinal cord. This damage causes lesions that interrupt communication signals in the brain and spinal cord, resulting in a range of physical and cognitive symptoms.

MS is more common among females than males, and doctors most often diagnose it in people in their 20s and 30s.

Learn more about different types of multiple sclerosis here.

Myasthenia gravis

MG affects the voluntary muscles, which include muscles that are involved in the following functions:

  • swallowing
  • eye movement
  • limb movement

MS occurs when antibodies attack receptor sites at neuromuscular junctions, which are the junctions between nerves and muscles. Damage to these sites causes muscle weakness.

This disease can occur at any age but typically develops in females under 40 years of age and males over 60 years of age.

Summary of the key difference

The primary difference between MS and MG is that the two diseases affect different parts of the nervous system. While MS affects the CNS, MG affects the voluntary muscles.

The symptoms, treatments, causes, and diagnosis of these conditions include:

Multiple sclerosisMyasthenia gravis
Symptoms* vision issues, such as:
** blurred or double vision
** partial vision loss
* neuromuscular symptoms, such as:
** muscle tremors or spasms
** muscle numbness or weakness
** coordination problems
* dizziness
* fatigue
* memory problems
* loss of bladder or bowel control
* sexual dysfunction

* vision issues, such as:
** blurred or double vision
** eyelid drooping
* neuromuscular symptoms, such as:
** weakness of the limbs, hands, or neck
** difficulty speaking or swallowing
* shortness of breath

Treatments* medications, such as:
** interferons
** glatiramer acetates
** natalizumab
** mitoxantrone
** steroids
* complementary therapies, such as:
** physiotherapy
** occupational therapy
** speech therapy
* medications, such as:
** anticholinesterase medications
** immunosuppressants
** steroids
* thymectomy
* plasmapheresis
* immunoglobulin treatment

Causes* genetic factors
* environmental factors
* infectious factors
* genetic factors
* environmental factors
Diagnosis* neurological exam
* blood tests
* magnetic resonance imaging (MRI)
* lumbar puncture
* evoked potential test
* neurological exam
* blood tests
* MRI or CT scans
* edrophonium test
* electrodiagnostics

Below is a summary of the symptoms of MS in comparison with those of MG.

Multiple sclerosis

The symptoms of MS vary widely from person to person and can also change over time. They may disappear and reappear and vary in severity upon relapse. Common symptoms include:

Myasthenia gravis

The main indicator of MG is a weakness of the voluntary muscles, which worsens with activity and improves after rest. The voluntary muscles include those of the face, such as those that affect the following functions:

  • chewing
  • swallowing
  • talking
  • eye movement

Symptoms of MG include:

MS and MG involve different disease mechanisms and symptoms and require different treatments.

Multiple sclerosis

There is currently no cure for MS. Treatment focuses on symptom management and slowing disease progression. The primary methods of treatment include:

Myasthenia gravis

The treatment for MG may involve a combination of medication, surgery, and treatment procedures designed to support the immune system. There is currently no known cure for MG, so treatment focuses on strengthening the affected muscles to improve muscle function.

Treatment may include the following:

  • Medications: Examples include:
    • anticholinesterase medications
    • immunosuppressants
    • steroids
  • Thymectomy: Surgical removal of the thymus gland, which is involved in the function of the immune system. Research has found it to improve symptoms in 70% of people who do not have cancer of the thymus.
  • Plasmapheresis: Involves removing abnormal antibodies from the blood and replacing them with normal antibodies from donated blood.
  • Immunoglobulin treatment: Involves boosting levels of the blood product “immunoglobulin,” which reduces the immune system’s tendency to attack the nerves.

Both MS and MG may involve a combination of genetic and environmental causes. However, the exact causes differ between the two conditions.

Multiple sclerosis

The exact cause of MS remains unknown. However, the following factors are likely to play a role in its development:

  • Genetic factors: People are more likely to develop MS if someone in their family has the disease, suggesting a possible genetic link.
  • Environmental factors: Some environmental factors that could increase the risk of MS include:
  • Infectious factors: Medical experts have also noted a possible link between certain childhood viruses and the development of MS in later life.

Myasthenia gravis

Some people with MG have an enlarged thymus gland, indicating that this gland may play a role in the development of the disease.

According to the National Organization for Rare Disorders, most people with MG have no family history of the disease, though around 5% of people with it have a relative who has MG or some other autoimmune disorder. This suggests that there is some genetic predisposition to MG, which requires an environmental trigger in order to develop.

The diagnostic procedures for MS and MG are as follows:

Multiple sclerosis

To diagnose MS, a doctor will conduct a comprehensive medical history and ask about a person’s current symptoms.

A doctor will then perform a complete neurological exam to check neurologic function. They may focus on things such as:

  • reflexes
  • balance
  • coordination
  • walking
  • facial function
  • vision
  • hearing
  • swallowing

A doctor may also order the following tests:

  • Blood tests: These can help rule out other underlying conditions.
  • MRI scans: These can help identify damage to the myelin sheath.
  • Lumbar puncture: Involves removing some cerebrospinal fluid to analyze it to check for the disease of the CNS.
  • Evoked potential test: Involves measuring how long it takes the brain to respond to light patterns entering the eyes.

Myasthenia gravis

To diagnose MG, a doctor will conduct a comprehensive medical history and ask about a person’s current symptoms. The doctor will perform a neurological exam to check for the following:

  • muscle coordination
  • muscle strength
  • problems with eye movement

A doctor may also order the following tests:

  • Edrophonium test: Involves injections of edrophonium chloride to temporarily increase the action of acetylcholine at neuromuscular junctions. The doctor will generally look for improved eye function.
  • Electrodiagnostics: Involves repeatedly stimulating the nerves with small pulses of electricity to test muscle fiber response.
  • Blood tests: These can check for antibodies associated with MG.
  • MRI or CT scans: These can help detect issues with the thymus.

Weakness is a common symptom of many disorders. As such, doctors often delay a diagnosis of MG if symptoms are mild or affect only a few muscles.

The relative outlooks for MS and MG are as follows:

Multiple sclerosis

MS varies widely from person to person and changes over time. Symptoms may go into remission and disappear or may recur over a period of years.

Most people with MS can expect relapses, when symptoms flare up for a period of 24 hours or longer, then abate. Doctors measure disease progression according to the worsening of symptoms over time, the number and severity of flare-ups, and the persistent effects after a flare-up resolves.

Myasthenia gravis

MG often improves with appropriate treatment. Medications can help with immune system function and neuromuscular communication.

The disease can go into remission, but this may only be temporary.

The disease progression associated with MS differs from that associated with MG. The way in which each disease progresses will also differ from person to person.

Multiple sclerosis

People with MS generally find that they recover completely after their first few flares. In some cases, relapses may even be years apart.

As the disease progresses, the time between relapses will generally shorten, and people may experience more difficulty with tremors or coordination.

Most people with MS retain the ability to walk, sometimes with a cane or crutches. Some may choose to use a wheelchair to help conserve their energy levels.

Myasthenia gravis

Treatment for MG is generally successful at addressing immune system dysfunction and strengthening muscle function. Most people tolerate the treatment well and are able to live normal or nearly normal lives.

MG may go into remission, particularly following surgical removal of the thymus.

Although MS and MG are two different autoimmune diseases with different developmental processes, they can exist together. However, this is a rare occurrence.

MS and MG are autoimmune diseases, meaning they both occur as a result of the immune system attacking healthy cells and tissues within the body.

Both diseases can cause vision and neuromuscular symptoms. However, the symptoms of MS may be more widespread.

MS and MG require treatment with medication and complementary therapies. Whereas MS is progressive, MG generally has a good outcome with treatment, and may completely resolve following surgical removal of the thymus gland.