Myasthenia gravis

Definition of Myasthenia gravis

Myasthenia gravis is a neuromuscular disorder. Neuromuscular disorders involve the muscles and the nerves that control them.

Causes, incidence, and risk factors

Myasthenia gravis causes weakness of the voluntary (skeletal) muscles. These are the muscles that create movement and are normally under your conscious control. The involuntary muscles, on the other hand, are not under conscious control (such as the muscles of your heart and many other internal organs).

Symptoms

The muscle weakness of myasthenia gravis worsens with activity and improves with rest. Weakness in affected muscles may cause:

Signs and tests

A neurological examination may be normal or may show that progressively worsens as the muscle is used. In many people with myasthenia gravis, the eye muscles are affected first. Reflexes and feeling (sensation) are normal. Weakness may affect the arms, legs, breathing or swallowing muscles, and any other muscle group.

Treatment

There is no known cure for myasthenia gravis. However, treatment may result in prolonged periods without any symptoms (remission).

Expectations (prognosis)

There is no cure, but long-term remission is possible. There may be minimal restriction on activity in many cases. People who have only eye symptoms (ocular myasthenia gravis), may develop generalized myasthenia over time.

Review

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Daniel B. Hoch, PhD, MD, Assistant Professor of Neurology, Harvard Medical School, Department of Neurology, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 12/21/2009

Superficial anterior muscles
Ptosis, drooping of the eyelid

ADAM Medical Encyclopedia

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