Myasthenia Gravis (MG)
Myasthenia Gravis (MG) is a chronic autoimmune neurological disorder that disrupts the transmission of nerve-to-muscle impulses. As an autoimmune condition, the body’s immune system and immune cells mistakenly attack healthy cells, specifically targeting voluntary and skeletal muscles.
It causes weakness of muscles that increases with their use and decreases with rest. The condition is based on neuromuscular junction failure, in which nerve fibers transmit impulses to muscles to stimulate them. Upon disruption of the interface, muscles fail to respond as expected, contributing to weakness and fatigue.
Myasthenia gravis affects both men and women, occurs across all racial and ethnic groups, and most commonly impacts young adult women (under 40) and older men (over 60), but it can occur at any age, including childhood. Myasthenia gravis affects 50 to 200 people per million.
Although MG is not transmissible or hereditary in most cases, it significantly affects daily life and requires long-term management. Myasthenia gravis can be difficult to diagnose due to the subtlety of its symptoms, which can resemble other neurological disorders.
How the Condition Affects the Body
In an MG patient, the immune system produces antibodies that destroy acetylcholine receptor sites on healthy cells, disrupting normal function at the neuromuscular junction. This autoimmune attack is mediated by immune cells, such as T-lymphocytes, which contribute to the targeting of these essential receptors. Normally, nerve endings release acetylcholine, which binds to receptors on skeletal and voluntary muscles to trigger muscle contraction. When antibodies destroy these receptor sites, muscles do not receive proper signals to contract, leading to a breakdown in communication. This pathological nerve conduction, over time, results in varying degrees of muscle weakness, typically affecting the voluntary muscles that govern eye movement, facial expression, swallowing, and breathing.
While some cases are caused by antibodies to a protein called muscle-specific kinase (MuSK), most are caused by antibodies that can destroy acetylcholine receptors. The disease typically does not damage sensation or involuntary muscle, and almost all patients maintain normal mental function.
Symptoms of Muscle Weakness That Signal a Problem
Myasthenia gravis symptoms may begin suddenly or slowly. The early warning signs typically appear in the eyes, and eyelid drooping and double vision are two of the earliest changes. Symptoms tend to worsen with activity and improve with rest.
Most people with myasthenia gravis feel strongest at the start of the day and weakest at the end of the day. Fatigue accumulates with exercise and may be relieved after a period of rest, making the diagnosis at this point challenging. Some patients may experience only mild weakness, which can make diagnosing myasthenia gravis difficult, while others may encounter more extensive muscle involvement over time.
Muscle weakness is most commonly limited to specific groups, such as those involved in chewing or lifting the head. The course is variable. The weakness may fluctuate throughout the day and can worsen in the evening or with repeated use of the affected muscle. Severe weakness can occur, especially in advanced cases, and may impair vital functions such as breathing, potentially leading to a myasthenic crisis. Common symptoms of myasthenia gravis include drooping eyelids and double vision. The weakness of muscles involved in swallowing may lead to dysphagia, where food may be left in the mouth after an attempt to swallow.
What Causes It?
The actual cause of Myasthenia gravis in the majority of cases is not known. Certain genetic and environmental factors can increase the risk of developing myasthenia gravis, including specific medications and immune responses that may trigger the onset of the disease. There is, however, always a problem with an autoimmune process, whereby the body mistakenly attacks its healthy tissue.
In many adults who develop myasthenia gravis, the thymus gland remains large even after reaching adulthood, and clusters of immune cells are often present. These individuals may also develop tumors known as thymomas. The thymus, which regulates immune system activity, is hypertrophied or tumorous in MG patients. Thymectomy, or removal of the thymus by surgery, has been found to alleviate the symptoms in a few instances in such patients. Additionally, human leukocyte antigen haplotypes are associated with increased susceptibility to myasthenia gravis and other autoimmune disorders.
In limited instances, infants are born with transient MG when the mother carries autoantibodies. The neonatal type is reversible and resolves within a couple of weeks after birth.
Risk Factors You Ought to Know
Dementia is not caused by a single factor but rather by a combination of diseases and health conditions that increase dementia risk in an individual. Aging is the greatest risk factor for developing dementia, with the likelihood increasing significantly with age. However, dementia is not a normal part of aging.
Several health conditions can increase dementia risk, including immune disorders and neurological diseases such as multiple sclerosis. Brain injury, particularly traumatic brain injury, is a distinct neurological event that can lead to cognitive decline and increase the risk of developing dementia later in life. Air pollution is also associated with an increased risk of developing dementia.
- Age
MG can develop in anyone, regardless of age, but is predominantly found in women under 40 and in men over 60.
- Gender
Women get MG-positive at an earlier age than men, who get it at an older age.
- Other Autoimmune Disorders
Those with thyroid disease, lupus, or rheumatoid arthritis are at a moderately increased risk.
- Family History
Although MG is not an inherited condition, susceptibility to autoimmune disease can be inherited.
Whilst not all instances are triggered by these risk factors, being aware of this will help with earlier detection and identification.
How Is Myasthenia Gravis Diagnosed?
Myasthenia gravis can be difficult to diagnose due to the subtlety of its symptoms, which can resemble other neurological disorders. It is often diagnosed through a combination of clinical testing, blood tests, and specialist nerve tests. Blood tests can help determine whether specific antibodies are present that may hinder muscle activation.
Physicians also conduct a nerve conduction test called electromyography (EMG), which checks how electrical signals travel from nerves to muscles. These tests, combined with a thorough review of medical history and symptoms, are essential in having myasthenia gravis diagnosed.
Sometimes, imaging tests such as a chest CT or MRI are performed to check for thymomas in patients suspected of having myasthenia gravis by evaluating the thymus gland for enlargement or tumors.
The “ice pack test” is an old diagnostic test employed in the treatment of eyelid ptosis. Spontaneous improvement in muscle strength in MG is observed as a transient increase following application of an ice pack to the ptotic eyelid, confirming a neuromuscular etiology.
How Is Myasthenia Gravis Treated? Methods That Work
Whereas MG cannot be cured, it is highly controllable. Treatment aims to improve muscle weakness and manage symptoms. Myasthenia gravis is treated with a combination of medications, lifestyle changes, and sometimes surgery.
Physicians start with anticholinesterase medicines such as pyridostigmine, which are cholinesterase inhibitors that increase nerve-muscle transmission, maintain muscle strength, and help prevent crises. It is important to take these medicines as prescribed, often before meals, to optimize their effect.
Immunosuppressants, such as corticosteroids or azathioprine, may be added to prevent the synthesis of pathogenic antibodies when the disease persists or worsens.
Some individuals with myasthenia gravis may experience periods of remission where symptoms disappear completely. With treatment, most people with myasthenia gravis live to an average life expectancy.
Thymectomy, surgical removal of the thymus gland, is one option, namely for the patient with thymoma. Thymectomy has even led to long-term improvement in a few instances of generalized MG, whether or not a tumor is present.
Living with Myasthenia Gravis
MG is learning to manage weaknesses and avoid symptom precipitants. Rest is required because muscles need to recover from use. Balancing physical activity with rest can help manage symptoms, as muscle weakness in myasthenia gravis often worsens with activity.
Overuse, heat, cold, stress, and certain drugs will exacerbate symptoms and should be avoided as much as possible. Although it may seem so at times, the overwhelming majority of patients have found support groups helpful in managing MG. Many people can have active, independent lives with treatment.
Follow-up is required regularly because the illness can manifest in various forms in the future. Drug therapy, psychotherapy, or surgery will have to be modified once new symptoms are encountered. Ongoing follow-up is important to manage symptoms and optimize quality of life.
Possible Complications
- Difficulty breathing: Weakness of the breathing muscles, including the diaphragm and chest muscles, can lead to respiratory failure and may require mechanical assistance.
- Difficulty swallowing: Pneumonia from aspiration or weight loss can ensue.
- Vision loss: Caused by prolonged double vision or eyelid drooping.
- Myasthenic crisis: The most serious complication of myasthenia gravis, characterized by extreme muscle weakness, particularly of the breathing muscles. This life-threatening emergency may require a respirator or ventilator to help with breathing until muscle strength returns. Approximately 15-20% of people with myasthenia gravis experience at least one myasthenic crisis in their lifetime. Myasthenic crisis can occur due to a lack of medicine, respiratory infection, emotional stress, or surgery. Precautions to prevent or minimize the occurrence of myasthenic crisis include taking anticholinesterase medicines as prescribed and avoiding contact with people who have respiratory infections.
- Drug side effects: Decades of immunosuppressive therapy expose patients to infection and other issues.
Due to these dangers, patients must work closely with their medical providers to monitor changes and adjust treatments as needed.
When to Call a Specialist
If you or your partner experiences unexplained muscle weakness — especially if it gets worse when used and better at rest — don’t wait to test. Non-localizing complaints, such as drooping eyelids, slurred speech, or difficulty chewing, may result from an undiagnosed neuromuscular illness, such as Myasthenia Gravis.
We realize the complexity of this illness at Chester Neurology. That’s why we provide complete testing, empathetic care, and individualized treatment plans. If you’ve recently been diagnosed or would like to have improved control of your symptoms, we can help.
Call us today at (914) 816-1941 or email info@chesterneurology.com to schedule an appointment.
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