Myasthenia gravis

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Ptosis, drooping of the eyelid

Superficial anterior muscles

Neuromusclar disorder - myasthenia gravis

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

• Breathing difficulty because of weakness of the chest wall muscles
• Chewing or swallowing difficulty, causing frequent gagging, choking, or drooling
• Difficulty climbing stairs, lifting objects, or rising from a seated position
• Difficulty talking
• Drooping head
• Facial paralysis or weakness of the facial muscles
• Fatigue
• Hoarseness or changing voice
• Weakness of the eye muscles, causing
  • Double vision
  • Difficulty maintaining steady gaze
  • Eyelid drooping

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A neurological examination may be normal or may show muscle weakness 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.

Tests that may be performed:

• Acetylcholine receptor antibodies (may be present in the blood)
• CT or MRI scan of the chest (may show a tumor in the thymus)
• Repetitive stimulation (a type of nerve conduction study, may be more sensitive)
• Single-fiber EMG (may be very sensitive)

Review Date: 12/21/2009
Reviewed By: 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.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).