What is Myasthenia Gravis?
MYASTHENIA GRAVIS (MG) is a chronic disabling autoimmune neuromuscular dosease of sever, crippling weakness. MG results from a defect in transmission of the nerve impulse to the nerve-muscle junction. The disease is characterized by adnormal weakness of voluntary muscels and increases with activity and decreases with times of rest. Symptoms include but are not limited to,difficulty breathing, moving, chewing, swallowing, speaking, and seeing. The symptoms of MG frequently create such a diagnostic dilemma, that physicians unfamiliar with the disorder may not recognize the characteristics to make an appropraite diagnosis. For this reaso, it is probable that the prevalence rate is actually higher than the current estimated 70,000 people.
Symptoms
The hallmark of myasthenia gravis is fatigability. Muscles become progressively weaker during periods of activity and improve after periods of rest. Muscles that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are especially susceptible. The muscles that control breathing and neck and limb movements can also be affected. Often the physical examination is within normal limits.
The onset of the disorder can be sudden or rapid. Often symptoms are intermittent. The diagnosis of myasthenia gravis may be delayed if the symptoms are subtle or variable.
In most cases, the first noticeable symptom is weakness of the eye muscles. In others, difficulty in swallowing and slurred speech may be the first signs. The degree of muscle weakness involved in MG varies greatly among patients, ranging from a localized form, limited to eye muscles (ocular myasthenia), to a severe or generalized form in which many muscles - sometimes including those that control breathing - are affected. Symptoms, which vary in type and severity, may include asymmetrical ptosis (a drooping of one or both eyelids), diplopia (double vision) due to weakness of the muscles that control eye movements, unstable or waddling gait, weakness in arms, hands, fingers, legs, and neck, a change in facial expression, dysphagia (difficulty in swallowing), shortness of breath and dysarthria (impaired speech, often nasal due to weakness of the velar muscles).
In myasthenic crisis a paralysis of the respiratory muscles occurs, necessitating assisted ventilation to sustain life. In patients whose respiratory muscles are already weak, crises may be triggered by infection, fever, an adverse reaction to medication, or emotional stress. Since the heart muscle is stimulated differently, it is never affected by MG.
Eye muscles
In more than half the people who develop myasthenia gravis, their first signs and symptoms involve eye problems, such as:
- Drooping of one or both eyelids (ptosis)
- Double vision (diplopia), which may be horizontal or vertical
- Blurred vision, which may come and go
Face and throat muscles
In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause difficulties with:
- Speaking. Your speech may be very soft or sound nasal, depending upon which muscles have been affected.
- Swallowing. You may choke very easily, which makes it difficult to eat, drink or take pills. In some cases, liquids you're trying to swallow may come out your nose.
- Chewing. The muscles used for chewing may wear out halfway through a meal, particularly if you've been eating something hard to chew, such as steak.
- Facial expressions. Family members may note that you've "lost your smile" if the muscles that control your facial expressions are affected.
Arm and leg muscles
Myasthenia gravis can cause weakness in your arms and legs, but this usually happens in conjunction with muscle weakness in other parts of your body — such as your eyes, face or throat. The disorder usually affects arms more often than legs. However, if it affects your legs, you may waddle when you walk.
When to see a doctor
Talk to your doctor if you have trouble:
- Breathing
- Seeing
- Swallowing
- Chewing
- Walking
