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The neuromuscular junction disorder Myasthenia gravis used to always be disabling and even fatal. But now, it can usually be managed with various therapies. The disease causes muscle weakness due to the immune system attacking neurotransmitter receptors on muscle tissue. Since the muscle can't receive the signal to contract, people with myasthenia become weak.
Basically, there are five ways of treating myasthenia gravis.
Some methods are best used in acute crises in order to keep someone out of an intensive care unit, although this is still sometimes necessary in extreme cases. Others are meant more to avoid such crises happening in the first place.
Avoid Triggers to Prevent Attacks
Because it is an autoimmune disease, anything that ramps up the immune system can potentially increase the risk of a myasthenic crisis, with severe worsening that could send someone to the intensive care unit. Noticing and avoiding any triggers is a key factor in managing the disease. For example, commonly-used medications like ciprofloxacin or other antibiotics, and beta-blockers like propranolol, lithium, magnesium, verapamil and more, can worsen the symptoms of myasthenia gravis. In general, people with myasthenia should be very cautious before starting any new medication, and watch carefully afterwards for signs of weakness.
Symptomatic Treatment
The weakness of myasthenia gravis occurs when the acetylcholine receptor is attacked by the body's immune system.
Supplementing the amount of acetylcholine available at the neuromuscular junction can help overcome this deficit. The body usually clears acetylcholine from the synapse by means of enzymes called acetylcholinesterases. Drugs called cholinesterase inhibitors can result in the acetylcholine's being left in the synapse for a longer period of time, increasing the likelihood of any particular molecule of a neurotransmitter making contact with a free receptor.
Acetylcholinesterase inhibitors include pyridostigmine (Mestinon), which is the main drug in use for myasthenia gravis. Side effects include diarrhea, cramping, and nausea. Taking the medication with food can help reduce these side effects. Strangely, sometimes excessive anticholinesterase medication has a paradoxical side effect of weakness, which can be difficult to distinguish from the myasthenia itself. This is rare if pyridostigmine is used within recommended doses, though.
Chronic Immunotherapy
Most people with myasthenia gravis end up taking medication to prevent symptoms from coming on at all. Immunotherapy targets the underlying antibodies that attack the acetylcholine receptors. By changing the immune system, the frequency and severity of attacks is reduced.
Glucocorticoids such as prednisone are often used to suppress the immune system of people with myasthenia. Other options include cyclosporine, azathioprine, and mycophenolate. All of these medications have potential side effects, some of which are quite serious. The risks of the medication must be carefully weighed against the benefits of fewer and less severe attacks of myasthenia.
Rapid Immunomodulating Treatments
Whereas chronic immunotherapy agents are intended to work over a long period of time, some situations require quick action. An example would be a myasthenic crisis, or before a surgery or other necessary event that would be expected to possibly exacerbate such a crisis. Rapid immunotherapies work within days, but their benefits only last for weeks, and they are not usually recommended over a long period of time.
Plasma exchange (plasmapheresis) removes antibodies from the circulation. The process is expensive, and typically occurs about five times over 7 to 14 days. Complications can include arrhythmia, blood cell abnormalities, muscle cramps, and more.
Intravenous immunoglobulin (IVIG) has often been shown to be helpful in diseases caused by an autoimmune reaction, but the exact mechanism is unclear. Treatment usually consists of two to five days of injections. Side effects are usually mild, but can include renal failure, meningitis, and allergic reactions.
Surgical Treatment
Most people with myasthenia gravis have an abnormality in their thymus, an immune system organ at the base of the neck. Sometimes people's myasthenic symptoms improve or even resolve after the thymus is removed during a procedure called a thymectomy. There is no guarantee of such an outcome, however. A relatively high percentage of people with myasthenia have a thymus tumor (thymoma), and doctors agree that surgery is indicated in these cases. Whether thymectomy is indicated in other cases of myasthenia gravis is less clear, and should be discussed with a neurologist on a case by case basis.
Conclusion
Myasthenia gravis is a serious disease, but there are many therapeutic options available to both reduce weakness when it occurs, and help reduce the frequency and severity of attacks. Because of potential side effects with all medications, the treatment course should be discussed with a neurologist with a good knowledge of myasthenia gravis and its potential complications.
Sources:
Adams and Victor's Principles of Neurology, 9th ed: The McGraw-Hill Companies, Inc., 2009.
Braunwald E, Fauci ES, et al. Harrison's Principles of Internal Medicine. 16th ed. 2005.
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