Information About Lung Cancer

Lung Cancer

Overview

What is Myasthenia Gravis?

Myasthenia Gravis (MG) translates literally from Latin to “grave muscle weakness”. It is an autoimmune disease that leads to muscle weakness that gets progressively worse with physical activity. This means patients may wake up fine but feel progressively more tired throughout the day. It improves with rest. In Singapore, Myasthenia gravis is commonly found in women below the age of 30 and men above the age of 60.

There are three main types of MG. The first being generalized MG that affects the entire body. This presents a weakness in muscles of the eyes, throat, chest walls, and limbs which result in drooping eyelids (ptosis), difficulty swallowing, breathing, and moving in respectively.

Ocular MG affects mostly the eye muscles and can cause ptosis and double vision. This is rarer among MG patients as a majority suffers from generalized MG.

Lastly, there is also a strong link between MG and Thyoma which is the tumour formation as a result of cancer to the thymus gland. Studies have shown that 20-30% of patients with a Thymoma would develop MG.

The extent to which MG affects its patient can fluctuate but may worsen with physical exertion, certain types of medication, other illnesses, or pregnancy. That’s why an individual should consult Myasthenia Gravis Singapore specialist.

Symptoms of Myasthenia Gravis

Patients usually experience weakness of the eye muscles that may spread to other muscles in the body with time. The symptoms include:

  • Drooping of one or both the eyelids (ptosis)
  • Blurred or double vision
  • Unstable or “waddling” gait
  • Weakness in the arms or legs
  • Difficulty swallowing
  • Difficulty breathing
  • Difficulty speaking clearly

The severity of MG can progress either within hours or days from the initial symptoms with tendencies to worsen with exercise towards the end of the day. If left untreated or improperly managed, MG can eventually affect the patient’s ability to swallow or breathe making it life-threatening.

Causes of Myasthenia Gravis

Motor neurons are the nerves that control muscle movement. Each nerve cell communicates with their corresponding muscle cell via neurotransmitters (chemical compounds that tell the muscle to contract) called acetylcholine (ACh) at the neuromuscular junction. In a normal scenario, Ach can bind to receptors on the muscle cells to cause a contraction. However, patients suffering from MG have a disorder that causes the body’s immune system to attack itself. Antibodies are used to attack viral particles and invade pathogens by binding to them and either blocking certain important functions or acting as a tag to tell the body to destroy the foreign substance. In MG patients, these antibodies bind to the muscle receptor instead thus blocking Ach from binding and reducing muscle contraction.

Other antibodies may also bind to ACh molecules signaling for the body to destroy them. In another pathway, antibodies may destroy proteins required by the muscle cells to create the receptors that ACh binds to.

The thymus gland located behind the breastbone has also been found to secrete a large number of these antibodies.

The thymus gland is part of the immune system that produces these antibodies. It usually shrinks so much during infancy that it becomes no longer functional in adults. However, in patients suffering from MG, they have been found to contain an excessive number of cells that produce these receptor-blocking antibodies.

Other antibodies may also bind to ACh molecules signaling for the body to destroy them. In another pathway, antibodies may destroy proteins required by the muscle cells to create the receptors that ACh binds to.

Investigation

How is Myasthenia Gravis diagnosed?

Diagnosis of Myasthenia Gravis in Singapore heavily depends on a patient’s medical history and physical examinations. Some of the tests performed by doctors are as shown below:

  • Tensilon Test: The doctor will administer a drug called Tensilon which inhibits the breakdown of ACh molecules thus allowing for the activation of the muscles. For patients who do not have MG, this will not improve muscle fatigue. However, patients suffering from MG will experience a significant improvement in strength that will last for a few minutes.
  • Electromyogram (EMG): This is the electrical analysis of nerve and muscle function that will help doctors give a conclusive report.
  • Blood Tests: Patients suffering from MG would either have blood tests that show a high level of antibodies that bind to the muscle receptors or antibodies that destroy proteins required by the muscles to build the receptors.

Treatments

This is a drug that can help patients with milder forms of MG by inhibiting the breakdown of ACh molecules thus increasing the muscle’s ability to contract. The most commonly prescribed form of the drug is pyridostigmine.

These are a type of drugs that suppresses to immune response of the body thereby reducing the production of antibodies that disrupt the muscle function. The most commonly used among this is steroid as the first line. Stronger immunosuppressants like Cyclosporine and Azathioprine will then be used to control the symptoms. This is a treatment that is administered for more serious forms of MG due to the potentially detrimental side effects of having a suppressed immune system.

Thymectomy is the surgical removal of the thymus gland. This is done in our centre using robotic-assisted surgery wherein the patient is operated on with 3-4 tiny incisions (8mm) and is usually discharged in 1 to 2 days. With this advanced platform of surgery, we are able to move away from the conventional method which is done by the opening of median sternotomy. If there is an associated tumour, then your surgeon will discuss options regarding which modality is best in your case. The earlier the surgery following the onset of symptoms, the better the chances of improved outcomes with remissions.

Blood plasma makes up more than 90% of our blood content and transports the antibodies produced by the body. The process of plasmapheresis is essentially changing the patient’s blood plasma for donor blood plasma to rid the blood of antibodies that disrupt the muscle receptors. However, it is important to note that this is a risky, expensive and time-consuming treatment.

Intravenous infusion of immunoglobulin can modulate the immune system and reduce the effects of causative autoantibodies in MG. It is used to treat MG with acute worsening, especially with breathing involvement.

For patients with MG, a healthy lifestyle and education about one’s disease can maximise management. Some of the best ways to accomplish this include:

  • Eating foods that are high in potassium such as bananas, tomatoes, apricots, and broccoli
  • Avoiding overexertion
  • Advising physicians of the diagnosis before taking prescribed drugs that may aggravate MG
  • Avoiding excessive heat

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