What is myasthenia gravis?
Myasthenia gravis is an autoimmune disease marked by muscle weakness and fatigue that worsens during activity and improves with rest. The symptoms are activated when the immune system produces antibodies that interfere with the transmission of nerve signals to skeletal (voluntary) muscle. As a result, the affected muscles cannot contract normally. The disease is rare, occurring in one or two people per 10,000. It most commonly affects women under 40 and men over 60 but can occur at any age, even among children. Although prognosis has been poor in the past, current therapies can typically allow one to maintain a relatively normal quality of life. Some cases may even go into remission.
What are the symptoms?
In most cases, the first noticeable symptoms involve weakness of the eye muscles and include a drooping of one or both eyelids, known as ptosis. This is often accompanied by blurred or double vision as the muscles that control eye movements fatigue over time or with repeated use. In others cases, difficulty in swallowing and slurred speech may be the first signs. When it affects the limbs, myasthenia gravis can manifest as an unstable or waddling gait, weakness in arms, hands, fingers, or legs. It can cause drooping of the head and neck, a change in facial expression, difficulty in swallowing and shortness of breath or impaired speech (dysarthria).
Although it affects the whole body, there is wide variation among patients regarding the visible degree of muscle weakness involved. It can range from a localized form that is limited exclusively to the muscle of the eye (ocular myasthenia) to a more generalized and severe form that affects even the muscles controlling breathing. When this occurs - a situation known as myasthenic crisis - respiratory muscles weaken to the point where ventilation is unsustainable and requires emergent assistance with a respirator. In these patients, myasthenic crises can be triggered by anything that causes respiratory muscles to overwork and become fatigued, such as a respiratory infection (typically involving spasmodic coughing), fever, asthmatic attacks or adverse reactions to medications.
Symptoms can come on insidiously, and since weakness is a common problem of many disorders, the diagnosis can often be delayed or missed. The hallmark feature that distinguishes myasthenia from other neurologic conditions is weakness without a change in sensation. If your doctor does suspect myasthenia, there are several tests available to confirm the diagnosis.
What are the causes?
Myasthenia gravis is caused by a disruption in the transmission of nerve impulses to muscles. Normal communication between muscles and nerves occurs at the neuromuscular junction (NMJ) - the place where nerve cells connect with the muscles they control. During voluntary movement, an impulse travels down a nerve, and the nerve endings release a neurotransmitter called acetylcholine. Acetylcholine travels through the space that is the NMJ and binds to acetylcholine receptors at special sites within the muscle tissue membrane called motor end plates. When a nerve activates the end plate, an electrical impulse propagates through the muscle and generates a muscle contraction.
In myasthenia gravis, antibodies block, alter, or destroy acetylcholine receptors at the NMJ, thereby altering communication between muscle and brain, and preventing muscle contractions. It's believed that the thymus gland, a part of the immune system located in the upper chest behind the sternum, may be centrally involved in triggering or maintaining the production of these abnormal antibodies. The thymus is a key player in the development of the immune system and is especially active in childhood. It is typically large in infancy, grows gradually until puberty and then shrinks in size until by adulthood, it is relatively small. However, a large percentage of individuals with myasthenia have abnormally large thymus glands, whose tissue reveals signs of lymphoid hyperplasia- the same reaction that causes lymph nodes and the spleen to enlarge. Some people with myasthenia also have tumors of the thymus, called thymomas, and about half of these tumors are malignant. Although the exact relationship between the thymus gland and myasthenia is still uncertain, the thymus does contain receptors for acetylcholine, and it is thought that the gland may be giving incorrect instructions to developing immune cells, causing them to produce antibodies that attack their own body's tissue, particularly skeletal muscle.
Because myasthenia is an autoimmune disorder, certain factors that can make it worse include undo stress on the body, worsening fatigue, illness, extreme changes in temperature and some medications - such as beta blockers, calcium channel blockers, quinine and some antibiotics.
What is the conventional treatment?
Doctors use a variety of treatments, alone or in combination, to relieve symptoms of myasthenia gravis. Medications used for overcoming muscle weakness either block the breakdown of acetylcholine at the NMJ or try to suppress the immune system and reduce antibody production. Anticholinesterase agents like pyridostigmine (Mestinon) help improve neuromuscular transmission and increase muscle strength. They enhance communication between muscles and nerves, and although they do not cure the underlying problem, they do improve muscle contraction. Immunosuppressive drugs include corticosteroids like prednisone, and other agents like cyclosporine (Sandimmune) and azathioprine (Imuran). These medications suppress the production of abnormal antibodies, which improves muscle function as a direct result of acetylcholine no longer being interfered with. Prolonged use of these kinds of medications can produce serious side effects such as bone thinning, weight gain, diabetes, increased risk of infection, an increase and redistribution of body fat, infertility, decreased white blood cell counts, and an increased risk for certain kinds of cancer. They should be used only under proper medical guidance.
Other therapies used to treat myasthenia gravis when drug therapy is ineffective include a procedure called plasmapheresis, in which abnormal antibodies are removed from the blood through a filtering process similar to dialysis. Unfortunately, the beneficial effects usually last only a few weeks. Another therapy involves using high-dose intravenous immune globulin, which temporarily modifies the immune system and provides the body with normal antibodies from donated blood. It has a lower risk of side effects than does plasmapheresis or immune-suppressing therapy, but can take a week or two to start working and the benefits usually last less than a month or two. These therapies are often used in severe cases to help individuals during especially difficult periods of weakness.
In the 15 percent of people with myasthenia gravis who have a thymoma, the tumor needs to be removed due to its potential transformation into a malignancy. Thymectomy, the surgical removal of the thymus gland, can reduce symptoms in those individuals with or without thymomas.
For people with myasthenia gravis who don't have a tumor in the thymus, but have an abnormally enlarged gland, it's unclear whether the potential benefit of removing the thymus outweighs the risks of surgery. Some research claims that thymectomy reduces symptoms in more than 70 percent of patients who do not have thymomas and may lead to complete remission in certain individuals. However, this is still a controversial issue that is being debated in the medical literature. Most surgeons will not recommend surgery when symptoms are mild and well controlled.
What therapies does Dr. Weil recommend for myasthenia gravis?
Dr. Weil recommends the following dietary changes for myasthenia gravis and all other autoimmune diseases:
- Reduce protein intake to 10 percent of total calories; replace animal protein as much as possible with plant protein.
- Eliminate milk and milk products (substitute other calcium sources).
- Eat more fruits and vegetables (make sure that they are organically grown).
- Eliminate polyunsaturated vegetable oils, margarine, vegetable shortening, all partially hydrogenated oils, and all foods (such as deep-fried foods) that might contain trans-fatty acids. Use extra-virgin olive oil as your main fat.
- Increase your intake of omega-3 fatty acids.
- Eat plenty of foods high in potassium, such as oranges, tomatoes, apricots and their juices, bananas and broccoli.
The following supplements are also recommended:
- Take ginger (start with one capsule twice a day). Turmeric can also be helpful.
- Dr. Weil’s antioxidant cocktail and multivitamin-mineral recommendations - see my anti-inflammatory diet.
Because autoimmune diseases tend to flare up in response to emotional ups and downs, Dr. Weil encourages trying some form of mind/body treatment - hypnosis may be especially helpful. Psychotherapy, biofeedback and guided imagery are also good options. You might also try consulting a practitioner of homeopathy or Chinese medicine to explore the contributors to flare ups and the underlying problem.