Muscle weakness caused by myasthenia gravis worsens as the affected muscle is used repeatedly. Because symptoms usually improve with rest, your muscle weakness may come and go. However, myasthenia gravis symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease.

Although myasthenia gravis can affect any of the muscles that you control voluntarily, certain muscle groups are more commonly affected than others.

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, and improves or resolves when one eye is closed.

Face and throat muscles

In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause:

  • Altered speaking. Your speech may sound very soft or nasal, depending upon which muscles have been affected.
  • Difficulty 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.
  • Problems 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.
  • Limited facial expressions. Your family members may comment that you've "lost your smile" if the muscles that control your facial expressions have been affected.

Neck and limb muscles

Myasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens along 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. If your neck is weak, it may be hard to hold up your head.

When to see a doctor

Talk to your doctor if you have difficulty:

  • Breathing
  • Seeing
  • Swallowing
  • Chewing
  • Walking
  • Using your arms or hands
  • Holding up your head
Apr. 23, 2013