Myasthenia gravis is an autoimmune disease in which communication between nerves and muscles is interrupted, leading to symptoms such as muscle weakness, drooping eyelids, or double vision.
This disease, also known as grave myasthenia, is more common in women and usually begins between the ages of 20 and 40. It is caused by an immune system change that makes antibodies attack the receptors responsible for controlling muscle movements.
There is no definitive cure for myasthenia gravis. However, a neurologist may recommend treatment with specific medications and physical therapy exercises to improve quality of life.
Common symptoms
The main symptoms of myasthenia gravis are:
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Muscle weakness that worsens with physical effort and improves with rest
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Drooping eyelids and difficulty opening the eyes or blinking
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Crossed eyes or double vision
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Fatigue when climbing stairs
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Coughing after swallowing, frequent choking, or difficulty chewing
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Hoarseness or difficulty speaking
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Head tilted forward or to the side
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Difficulty lifting the arms or writing
Symptoms usually get worse with repetitive use of the affected muscle. They can also appear or worsen when exposed to heat, during stress or anxiety, or when taking certain medications like sedatives or antibiotics.
In severe cases, respiratory muscles may also be affected, leading to what is known as a myasthenic crisis. This is a medical emergency that can be life-threatening if not treated promptly in a hospital.
Confirming a diagnosis
The diagnosis of myasthenia gravis is made by a neurologist through an evaluation of symptoms, the time of day they occur, whether they improve with rest, health history, medication use, and a physical and neurological exam.
Although diagnosis is usually clinical, the doctor may order tests to rule out other conditions with similar symptoms, such as multiple sclerosis, brainstem tumor, or polymyositis.
Tests that may be requested include electromyography, ice pack test, CT scan, or MRI. Another test that helps confirm diagnosis is the anti-AChR antibody test, which is very specific for identifying myasthenia gravis.
Possible causes
Myasthenia gravis is caused by an immune system alteration that attacks acetylcholine receptors (n-AChR) at the neuromuscular junction, as well as proteins such as muscle-specific kinase (MuSK) and lipoprotein-related protein 4 (LRP4).
These proteins are essential for nerve transmission and muscle contraction. When the electrical message cannot properly pass from neurons to muscle fibers, the muscle does not contract, resulting in the weakness characteristic of myasthenia gravis.
Certain factors can trigger or worsen myasthenia gravis, such as infections, heat, emotional stress, pregnancy, vaccination, surgery, and certain medications.
Treatment options
Treatment for myasthenia gravis must be guided by a neurologist and aims to relieve symptoms and improve quality of life.
1. Medications
Medications are the most common treatment because they are practical and usually provide excellent results. The main types are:
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Acetylcholinesterase inhibitors, such as pyridostigmine, which improve the passage of electrical signals between nerve and muscle, enhancing muscle contraction and strength
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Corticosteroids, such as prednisone or methylprednisolone, which help reduce the immune response and improve symptoms. However, they cannot be used long term due to the risk of significant side effects
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Immunosuppressants, such as azathioprine, cyclosporine, or methotrexate, which reduce immune activity and are generally used in more severe cases when symptoms do not improve with other medications
In addition to oral medications, doctors may recommend monoclonal antibodies, such as rituximab or eculizumab, or intravenous immunoglobulins, which reduce certain immune cells in the body and improve myasthenia gravis symptoms.
2. Plasmapheresis
Plasmapheresis is a therapy similar to dialysis, in which blood is removed from the body and filtered through a machine to eliminate excess antibodies that attack muscle receptors. This helps restore the electrical signal between neurons and muscle fibers.
Although effective, plasmapheresis carries some risks, such as bleeding, muscle spasms, and severe allergic reactions.
3. Surgery
Surgery, called thymectomy, is a less common treatment but may be recommended if a tumor is found in the thymus gland, which can trigger the production of antibodies that cause myasthenia gravis.
4. Physical therapy
Motor and respiratory physical therapy are also recommended to strengthen muscles, improve movement range and breathing, and prevent respiratory infections.