What Is Myasthenia Gravis?
Myasthenia gravis (MG) is a chronic autoimmune condition that affects communication between nerves and muscles. Normally, nerve signals trigger muscle contraction through specific receptors at the nerve-muscle junction. In MG, the immune system mistakenly produces antibodies that block or damage these receptors,weakening the signal and causing muscle weakness that worsens with activity and improves with rest. MG can affect people of any age but is most commonly diagnosed in women under 40 and men over 60.
Common Symptoms
A hallmark of MG is muscle weakness that fluctuates — often worse later in the day or after physical activity, and improved with rest.
- Drooping eyelids (ptosis)
- Double vision
- Difficulty swallowing or chewing
- Slurred or nasal-sounding speech
- Weakness in the arms, legs, neck, or fingers
- Facial weakness, affecting expressions
- Fatigue with repetitive movement
- In severe cases, weakness of the muscles involved in breathing
Types of Myasthenia Gravis
- Ocular MG: Symptoms limited to the eye muscles, causing drooping eyelids and double vision
- Generalized MG: Weakness extends beyond the eyes to affect other muscle groups, including limbs, throat, and breathing muscles
Many people who start with ocular MG go on to develop generalized MG over time.
What Causes Myasthenia Gravis?
- Abnormal antibodies attacking receptors at the nerve-muscle junction, disrupting signal transmission
- Associated in some cases with abnormalities of the thymus gland, including thymus tumors (thymomas)
- The exact trigger for the immune system malfunction isn’t fully understood
MG is not contagious and is not typically inherited, though genetic susceptibility may play a role.
Myasthenic Crisis: A Medical Emergency
A myasthenic crisis occurs when weakness affects the muscles used for breathing and swallowing, potentially leading to respiratory failure. This is a medical emergency requiring immediate hospital care. Triggers can include infections, certain medications, stress, or surgery.
How Is MG Diagnosed?
- Detailed history and neurological examination, checking for fatigable weakness
- Blood tests to check for specific antibodies associated with MG
- Edrophonium (Tensilon) test or ice pack test, in select cases
- Electromyography (EMG) with repetitive nerve stimulation to assess nerve-muscle communication
- Imaging of the chest (CT scan) to check the thymus gland
Managing Myasthenia Gravis
While there is no cure, MG can often be well-controlled with treatment:
- Medications: Such as acetylcholinesterase inhibitors, which help improve nerve-to-muscle signaling
- Immunosuppressive therapy: To reduce the abnormal immuneresponse
- Plasmapheresis or IVIG: Used for severe flares or to prepare for surgery
- Thymectomy: Surgical removal of the thymus gland, which can improve symptoms in many patients
- Lifestyle adjustments: Pacing activities, avoiding triggers that worsen symptoms, and planning rest periods
Living with Myasthenia Gravis
With appropriate treatment, many people with MG lead active, productive lives, though symptom managementoften requires ongoing care and periodic adjustments to treatment.
When to See a Doctor
Consult a doctor if you experience unexplained muscle weakness that worsens with activity and improves with rest, drooping eyelids, double vision, or difficulty swallowing or speaking. Seek emergency care immediately if breathing becomes difficult or swallowing problems become severe, as this may indicate a myasthenic crisis.