According to the Myasthenia Gravis Foundation of America, approximately 14 out of 100,000 individuals in the U.S. have been diagnosed with myasthenia gravis (MG). However, because MG is considered under-diagnosed, the prevalence is thought to be much higher.
MG is a chronic autoimmune disease characterized by muscle weakness that increases during periods of activity and improves after periods of rest. Certain voluntary muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often, but not always, involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.
Myasthenia Gravis: Symptoms
Some of the symptoms of myasthenia gravis include:
- Muscle weakness that improves after resting and gets worse after physical activity.
- Visual disturbances such as double vision, inability to hold a steady gaze, and droopy eyelids.
- Swallowing difficulties.
- Breathing difficulties.
- Shortness of breath.
Myasthenia Gravis: Diagnosis
There are many disorders that are characterized by muscle weakness, making diagnosis of myasthenia gravis difficult in some cases. Your neurologist will start by performing a complete medical and neurological evaluation. Standard tests used to diagnose MG include the following:
- Blood serum test to check for the presence of acetylcholine receptor (anti-AChR) antibodies.
- Tensilon test to determine if a patient’s muscle strength temporarily improves in response to edrophonium given intravenously.
- Electromyography (EMG) to measure the electrical activity of muscles.
Unfortunately, negative results on any or all of these tests do not rule out a diagnosis of MG.
Myasthenia Gravis: Treatment
Although there is no cure for MG, the disorder can be controlled. In fact, it is one of the more treatable neuromuscular disorders, responding well to a variety of therapies. However, the course of treatment for every patient is different. Your patient care team will tailor a program specifically to your needs that takes into account the severity of your weakness, the muscles affected, and your age, as well as any other associated medical problems.
Medications used to build muscle strength in MG patients include:
- Anticholinesterase agents, such as neostigmine and pyridostigmine, which prevent ACh destruction and increase the accumulation of ACh at neuromuscular junctions to improve neuromuscular transmission.
- Immunosuppressive drugs such as prednisone, cyclosporine, and azathioprine, which suppress the production of abnormal antibodies.
Patients taking these medications must be monitored carefully because the medications may cause major side effects.
A procedure called plasmapheresis, or plasma exchange, can also be used to treat more severe MG symptoms. Plasmapheresis is a process in which the fluid part of the blood, called plasma, is removed from blood cells by a device known as a cell separator. Several liters of blood are withdrawn intravenously and centrifuged. The patient’s red blood cells are then added either to plasma pooled from several healthy donors or to artificial plasma (plasma made of albumin and saline solution). This plasma/red blood cell mixture is then returned to the patient’s blood stream. This process removes the abnormal anti-AChR antibodies from the patient’s body. A plasmapheresis treatment takes several hours and can be done on an outpatient basis. Plasmapheresis improves MG symptoms within days and improvement lasts 6 to 8 weeks.
A thymectomy, the surgical removal of the thymus gland, is another treatment option for MG patients. This procedure often decreases the severity of, and in some cases eliminates, MG symptoms. Symptomatic improvement generally occurs gradually following the surgery, with peak effects achieved within several months or years of surgery. Candidates for this procedure include patients with a tumor of the thymus and patients under the age of 55 with generalized MG.
Myasthenia Gravis: Resources
Myasthenia Gravis Foundation of America
355 Lexington Avenue, 15th Floor
New York, NY 10017
Tel: (212) 297-2156 or (800) 541-5454
Fax: (212) 370-9047
Muscular Dystrophy Association – USA
3300 E. Sunrise Drive
Tucson, AZ 85718
National Organization for Rare Disorders
55 Kenosia Avenue
PO Box 1968
Danbury, CT 06813-1968
Tel: (203) 744-0100
Tollfree: (800) 999-6673 (voicemail only)