What is Myasthenia Gravis?

Myasthenia Gravis is a type of neuromuscular disorder. Usually, neuromuscular disorders engage the muscles and nerves which control them. The disease is most often seen in older men and younger women; however, MG can happen to anyone of any age.

Causes for Myasthenia Gravis

Myasthenia Gravis (MG) causes weakness of skeletal and some involuntary muscles. Skeletal muscles generate movement; these muscles usually are under your control when you are awake. The involuntary muscles, though, aren't under your control. Examples of involuntary muscles are the heart muscles, muscles that assist in breathing, and other organ muscles.

Causes of Myasthenia Gravis are believed to be related to immune system malfunctions; however, the exact cause for the disease is unknown. Normally, our muscles receive chemical commands to function. The immune system releases antibodies which destroy a great number of the acetylcholine receptor sites. Acetylcholine is a neurotransmitter that communicates with the muscles to function.

Oftentimes, a person with a diagnosis of MG has thymus gland tumors. The thymus gland is part of our immune system. Thus, the primary cause of Myasthenia Gravis is believed to be caused by a malfunction of the thymus gland. In healthy adults the thymus gland is small, but in people with Myasthenia Gravis the thymus gland is usually quite large. The gland is large because it is working overtime to produce antibodies that mistakenly attack the neuroreceptors that receive neurotransmitters for movement. The enlargement of the thymus gland is sometimes caused by tumors growing in them; the tumors are usually benign (nonmalignant).

Symptoms of Myasthenia Gravis

The symptoms of MG include muscle weakness, fatigue, facial weakness, breathing difficulties, hoarseness of the voice. Other symptoms include:

Breathing difficulties (due to weakness of the muscles in the chest wall)

Difficulty rising from a sitting position

Difficulty in climbing stairs

Difficulty lifting objects

Speech difficulties

Difficulty holding head up

Drooping eyelids

Facial paralysis

Weakness of eye muscles

Double vision

Drooling

Problems with choking

Improper gag reflex (frequent gagging)

Myasthenia Gravis diagnosed

Myasthenia Gravis is diagnosed after a series of tests have been done. A neurological test can be normal or can show muscle weakness which increasingly worsens as the muscle is used. Oftentimes, people who have MG suffer from weakness in the eye muscles first. The reflexes may be tested and be normal or impaired due to weakness in the legs and arms.

The following tests are done to aid in the diagnosis of Myasthenia Gravis:

Blood tests - To measure the amount of acetylcholine receptor antibodies

Repetitive nerve stimulation - To measure nerve conduction

Chest MRI or CT - To look for thymus gland tumors

Single fiber EMG (electromylogram) test - To measure the responsiveness of muscle fibers

Treatment for Myasthenia Gravis

There is no one specific treatment for Myasthenia Gravis; however, the main goal is to treat the symptoms. Making lifestyle changes may be necessary to continue with activities. For instance, a person that could walk before becoming sick may need to get around with a cane or walker; it may even be necessary to use a wheelchair or scooter. An eye patch may be necessary for someone suffering from double vision. Stress and exposure to heat may aggravate the symptoms of MG; thus excessive stress and exposure to heat should be avoided.

Some medications such as Pyridostigmine and Neostigmine are useful to help promote communication between the muscles and the nerves. Prednisone and other medications such as Azathioprine, Mycophenolate motetil, or Cyclosporine may be used to hold back the autoimmune response which is believed to cause the muscle weakness.

Other treatments include plasmapheresis, which can reduce the symptoms for about 4 to 6 weeks. Plasmapheresis is usually done prior to surgery. This procedure clears the antibodies out of the blood. The volume removed is replaced with donated plasma.

If surgery is indicated, the thymus may be removed, especially if tumors are present. By removing the thymus gland, the patient may not need to take the above mentioned medications.

Sources:

Medline Plus

Mayo Clinic