Muscle weakness can be frightening, and the cause isn’t always clear. Two conditions that can affect the face are myasthenia gravis (MG) and Bell’s palsy. Both disorders affect muscle control, which can make them hard to tell apart.

Myasthenia gravis is sometimes called “the great imitator” because it shares symptoms with other neurological conditions, including Bell’s palsy. While it’s rare for these two conditions to look exactly alike, they do have some similarities.

Read on for the differences and similarities that a doctor will evaluate when determining what’s causing your symptoms.

What Are Myasthenia Gravis and Bell’s Palsy?

Mmyasthenia gravis is an autoimmune disease, meaning the body’s immune system attacks itself. As a result, the body produces antibodies that attack the neuromuscular junction, the connection between nerves and muscles.

Think of nerves as messengers and muscles as workers. In myasthenia gravis, this handoff is disrupted, preventing signals from reaching the muscles and causing weakness.

Because myasthenia gravis results from the immune system attacking the body, it isn’t passed down in families or spread from person to person. But in rare cases, some people may have a genetic risk for developing it.

Bell’s palsy is a condition in which the facial nerve becomes inflamed. The swelling compresses the nerve, reducing the signals sent to the muscles. This means the muscles on that side of the face will be weak.

The exact cause of Bell’s palsy isn’t known, but some associated diseases might contribute to the condition. Viral infections, such as herpes simplex virus or Epstein-Barr virus, may be linked with Bell’s palsy.

Bell’s palsy may present similarly to other diseases that can affect the facial muscles, including Lyme disease, Guillain-Barré syndrome, or sarcoidosis. Pregnancy and exposure to toxins or infections can also increase the risk of developing Bell’s palsy.

Differences Between Myasthenia Gravis and Bell’s Palsy

Despite their similarities, there are differences between the conditions as well. These differences help healthcare providers determine a diagnosis and treatment options.

Who’s Affected

Although both conditions can occur at any age and in any race, they tend to appear in different age groups. NINDS reports that myasthenia gravis typically shows up in women under the age of 40 and men over the age of 60.

Bell’s palsy is more common between the ages of 15 and 60. While there’s some overlap, Bell’s palsy tends to occur in a broader age range than myasthenia gravis.

Other Symptoms

While both conditions cause muscle weakness, they affect different parts of the body. Myasthenia gravis can weaken muscles throughout the body, while Bell’s palsy is limited to the face. Unlike Bell’s palsy, myasthenia gravis symptoms may come and go, sometimes getting worse with activity and improving with rest.

In addition to affecting the muscles in the face, myasthenia gravis can affect all muscles, unlike Bell’s palsy. The muscles of the arms and legs are commonly affected, which leads to weakness.

Myasthenia gravis can also affect the muscles you use to breathe, causing shortness of breath. In severe cases, a myasthenic crisis can occur. This is a medical emergency because it makes it hard to breathe, sometimes to the point of needing a ventilator.

Bell’s palsy has a few other specific symptoms as well. Because it’s only one cranial nerve that’s affected, the symptoms usually just show up on one side of the face. Along with muscle weakness, you may experience a loss of taste on the front part of the tongue or increased sensitivity to sound on one side.

Treatments

The treatment choices for each condition are different.

MG Treatment

Myasthenia gravis has a few treatment options:

• Anticholinesterase medications — These drugs can help keep acetylcholine (a chemical that sends signals from nerves to muscles) in the neuromuscular junction for longer, which can improve communication between the nerves and muscles. This helps to improve muscle strength.
• Immunosuppressive drugs — These drugs aim to decrease the body’s overactive immune response.
• Targeted biologic therapies — Biologic therapies are medications made from living organisms. Complement inhibitors like eculizumab (Soliris and its biosimilar Bkemv) are biologic therapies that help to prevent damage to nerve and muscle function.
• Plasmapheresis and intravenous immunoglobulin — These are short-term therapies that target the antibodies of the overactive immune system. Your provider may recommend these therapies when rapid improvement is needed, such as before surgery.
• Surgery — The thymus gland, which helps control the immune system, is believed to play a big role in myasthenia gravis symptoms. The thymus can be removed in a procedure called a thymectomy.

Your doctor will talk you through all of the treatment options and help determine which ones might be best for you.

Bell’s Palsy Treatment

Bell’s palsy is closely linked to inflammation, so the first-line treatment is usually a dose of steroid medications to help reduce the swelling.

If your doctors are able to determine a specific cause for your Bell’s palsy, such as an infection, they’ll likely also give you medication to target the underlying condition. For example, if your provider discovers that you have Lyme disease, they’ll treat the infection.

Because a common symptom of Bell’s palsy is the inability to close one eye, eye care is an important part of treatment as well. This might include eye drops, ointments, or the use of an eye covering, such as an eye patch.

Prognosis

Most people with myasthenia gravis have a lifespan similar to those without the condition. While the overall life expectancy is generally normal with good management, some might continue to have significant symptoms. For the best prognosis, managing your symptoms is key.

Most people with Bell’s palsy recover completely without treatment. Full recovery can take up to six months. Early treatment with corticosteroids to reduce inflammation can improve your chances of making a full recovery.

Others with Bell’s palsy may have permanent facial weakness. People who have more severe facial paralysis or other health conditions may experience worse outcomes than those who recover completely.

Although myasthenia gravis and Bell’s palsy share some similarities, they are different conditions with their own treatment approaches. Working with a healthcare provider can help you manage symptoms and find the best treatment for your needs.