Myasthenia Gravis

Myasthenia gravis is a chronic autoimmune neuromuscular disease that weakens your skeletal muscles (the muscles that connect to your bones and contract to allow you to move your arms, legs, and breathe). Myasthenia gravis is characterised by muscle weakness that worsens with exertion and improves with rest.

The disorder typically (though not always) involves specific muscles, such as:

• Eyelid and eyelid movement
• Expressions on the face
• Chewing
• Speaking
• Swallowing

Myasthenia gravis can strike without warning, and symptoms may not be noted right away. Individuals' levels of muscular weakness vary person to person.

Symptoms

Myasthenia gravis is usually associated with the following symptoms:

• Muscle weakening in the eyes (ocular myasthenia)
• Drooping of one or both eyelids (ptosis)
• Blurred or double vision (diplopia)
• Changes in facial expression
• Difficulties swallowing
• Shortness of breath
• Arm, hand, and finger weakness, as well as leg and neck weakness

Myasthenia gravis can cause respiratory failure, which necessitates prompt emergency medical attention.

Who is More Likely to Get Myasthenia Gravis?

Myasthenia gravis affects both males and women, and people of all colours and ethnicities are affected. It primarily affects young adult females (under 40) and senior males (over 60), but anyone of any age, including children, can be affected. Myasthenia gravis is not hereditary or communicable. The disease might strike more than one member of the same family at times. Although infants are rarely affected by myasthenia gravis, the foetus may receive antibodies from a female parent, a condition known as neonatal myasthenia. Neonatal myasthenia gravis is usually transient, with symptoms disappearing within two to three months of delivery. Congenital myasthenia can occur in children born to healthy female parents. This is not an autoimmune illness, but it is caused by malfunctioning genes that produce aberrant proteins in the neuromuscular junction, which connects the end of a nerve that delivers information from the brain to a muscle and can cause symptoms similar to myasthenia gravis.

Causes of Myasthenia Gravis

• Antibodies: Myasthenia gravis is caused by a gap between nerves and muscles. It occurs when neuron and muscle communication is disturbed at the neuromuscular junction, which connects nerve cells to the muscles they control.

Neurotransmitters are molecules that allow neurons (brain cells) to communicate with one another. When an electrical impulse or signal travels through a motor nerve, the nerve ends release acetylcholine, a neurotransmitter that binds to acetylcholine receptors on the muscle. Acetylcholine connecting to its receptor stimulates and contracts the muscle. Antibodies (immune proteins produced by the body's immune system) block, modify, or destroy acetylcholine receptors at the neuromuscular junction in myasthenia gravis, preventing the muscle from contracting. Antibodies to the acetylcholine receptor are the most prevalent cause, but antibodies to other proteins, such as MuSK (Muscle-Specific Kinase), can also disrupt transmission at the neuromuscular junction.

• Thymus gland: The thymus gland regulates immunological function and has been linked to myasthenia gravis. It gradually increases until adolescence, then shrinks until it is replaced by fat. The thymus is vital in the development of the immune system throughout childhood because it is responsible for creating T-lymphocytes or T cells, a type of white blood cell that defends the body from viruses and illnesses. A big thymus gland is common in individuals with myasthenia gravis. Individuals suffering from the condition have immune cell clusters in their thymus gland and are at risk of developing thymomas (thymus gland tumours). Thymomas are usually benign, however they can develop into malignancy. The thymus gland, according to scientists, sends out wrong signals to developing immune cells, allowing the immune system to target its own cells and tissues and manufacture acetylcholine receptor antibodies, laying the groundwork for an attack on neuromuscular transmission.
• Myasthenic crisis: A myasthenic crisis happens when the respiratory muscles become too weak to breathe without the assistance of a ventilator. It can be caused by an infection, stress, surgery, or a negative reaction to medication. Around 15 to 20% of persons with myasthenia gravis suffer at least one myasthenic crisis, with up to 50% having no evident explanation. Certain drugs have been known to cause myasthenia gravis; nonetheless, these treatments may still be taken if treating an underlying ailment is more important.

How is Myasthenia Gravis Diagnosed and Treated?

To confirm a diagnosis of myasthenia gravis, a clinician may perform or prescribe the following tests:

• Physical and neurological Test: A doctor will go over medical history and do a physical exam. Several factors will be looked for by the doctor during a neurological examination.
  • Muscle strength and tone
  • Coordination
  • Sense of touch
  • Any eye movement impairment
• Edrophonium test: This test is used to detect eye muscle weakness and temporarily reduces weakness with edrophonium chloride injections. The medicine blocks the breakdown of acetylcholine and temporarily elevates acetylcholine levels at the neuromuscular junction.
• Blood test: Myasthenia gravis patients may have abnormally high levels of acetylcholine receptor antibodies. Anti-MuSK antibodies have been found in around half of myasthenia gravis patients who do not have anti-acetylcholine receptor antibodies. A blood test can also be used to detect this antibody. However, in some persons with myasthenia gravis, none of these antibodies is present; this is known as seronegative (negative antibody) myasthenia.
• Electrodiagnostic: Repetitive nerve stimulation is a diagnostic examination that involves repeatedly stimulating your nerves with short pulses of electricity to contract certain muscles. Myasthenia gravis muscle fibres, like those in other neuromuscular diseases, do not respond well to repetitive electrical stimulation. The most sensitive diagnostic for myasthenia gravis is single fibre electromyography (EMG), which identifies decreased nerve-to-muscle communication. Electromyography (EMG) can be extremely beneficial in detecting mild cases of myasthenia gravis when other tests fail to reveal abnormalities.
• Diagnostic imaging: Thymoma can be detected with diagnostic imaging of your chest, such as computed tomography (CT) or magnetic resonance imaging (MRI).
• Pulmonary function testing: Measuring breathing strength can assist forecast whether or not respiration will fail, resulting in a myasthenic crisis.

Because weakness is a typical sign of many other conditions, myasthenia gravis is frequently ignored or delayed (sometimes for up to two years) in people who have mild or localised weakness.

Treating Myasthenia Gravis

There is no known treatment currently. There are treatments available that help manage symptoms and allow you to live a normal life. Most people with myasthenia gravis live a normal life. Several treatments are available to assist reduce and improve muscle weakness, including:

• Thymectomy: By balancing the immune system, an operation to remove the bothersome thymus gland may assist to reduce symptoms. NINDS-funded research of 126 persons with myasthenia gravis and thymoma found that surgery reduced muscle weakness and the requirement for immunosuppressive medicines. Thymectomy is intended to achieve stable, long-term full remissions, which may occur in around half of those who undergo this operation.
• Monoclonal antibody: A medication that focuses on the mechanism via which cholinergic antibodies harm the neuromuscular junction. The FDA has approved the drug eculizumab for the treatment of generalised myasthenia gravis in persons who have antiacetylcholine receptor (AchR) antibodies.
• Anticholinesterase medications: Myasthenia gravis is treated with anticholinesterase drugs such as mestinon or pyridostigmine, which reduce acetylcholine breakdown at the neuromuscular junction and increase neuromuscular transmission and muscle strength.
• Immunosuppressive drugs: Prednisone, azathioprine, mycophenolate mofetil, and tacrolimus increase muscle strength by decreasing the generation of aberrant antibodies. Because the medications might have major side effects, they must be constantly managed by a doctor.
• Plasmapheresis and intravenous immunoglobulin: Treatments used to eradicate damaging antibodies that assault the neuromuscular junction in severe cases of myasthenia gravis, albeit their effectiveness normally lasts just a few weeks or months.

Plasmapheresis is a machine-assisted technique for removing harmful antibodies from plasma and replacing them with healthy plasma or a plasma replacement. Intravenous immunoglobulin is a highly concentrated infusion of antibodies derived from a large number of healthy donors that temporarily alters the immune system's function. It acts by attaching to and eliminating the antibodies that cause myasthenia gravis from circulation. Some cases of myasthenia gravis may go into remission, either temporarily or permanently, and muscle weakness may totally subside, allowing medications to be stopped.

What are the Latest Updates on Myasthenia Gravis?

The National Institute of Neurological Disorders and Stroke (NINDS) is a division of the National Institutes of Health (NIH), the world's largest scientific research funder. Myasthenia gravis, its causes, and the anatomy and function of the neuromuscular junction are still being studied by researchers. Technological breakthroughs have resulted in more quick and accurate diagnosis of myasthenia gravis, as well as new and improved treatment choices. Researchers are attempting to create better pharmaceuticals, find new techniques to diagnose and treat people, and expand treatment options.

Medication

Some persons with myasthenia gravis do not respond well to existing treatments, which often require long-term immune system suppression. New medications are being evaluated to see if they are more effective in addressing disease causes alone or in combination with existing therapeutic regimens.

Biomarkers and Diagnostics

NINDS-funded researchers are investigating the formation and function of nerve-muscle fibre connections in order to better understand the underlying mechanisms in neuromuscular development, which could lead to new therapeutics for neuromuscular illnesses such as myasthenia gravis. Researchers are also looking into new ways to detect people with undetectable antibodies and identifying potential biomarkers (signs that can help diagnose or measure the progression of a disease) to predict an individual's response to immunosuppressive drugs.

New Therapeutic Options

A NINDS-funded study discovered strong data about the benefits of surgery for persons without thymoma, putting an end to a decades-long debate. Other trials will be conducted to see whether other medications are superior to standard care options. Assistive devices such as magnetic gadgets may benefit people.

Better Care for Patients with Myasthenia Gravis

Consider taking part in a clinical study to help clinicians and researchers learn more about myasthenia gravis. Human trials are used in clinical research to assist researchers learn more about an illness and maybe identify better ways to diagnose, treat, or prevent disease. People of different ages, sexes, races, and ethnicities are needed, as well as those who are healthy or may have a problem or illness, to guarantee that study results apply to as many people as possible and that therapies are safe and effective for everyone who uses them.