Myasthenia gravis (MG) can affect any of the muscles that you control voluntarily. It can affect muscles of the face, hands, eyes, arms and legs and those muscles involved in chewing, swallowing and talking. Muscles that control breathing and neck movement also can be affected.
MG does not affect involuntary muscles such as the heart, smooth muscles of the gut, blood vessels, and uterus.
The hallmark of weakness related to MG is that is worsens with sustained activity of the involved muscle(s). Eye muscle weakness worsens with reading, and double vision may improve with a brief rest. When speech is affected, symptoms worsen with prolonged talking. Extremity weakness if often noticed when holding arms over the head. Drooping of the eyelids, neck weakness and other symptoms are usually worse at the end of the day.
Symptoms, which vary in type, severity and combination, may include:
- Drooping of one or both eyelids
- Double or blurred vision
- Weakness in arms, hands, fingers, neck, face or legs
- Difficulty in chewing, smiling, swallowing or talking
- Excessive fatigue in exercised muscle groups
- Shortness of breath, difficulty taking a deep breath or coughing
MG is often called the “snowflake disease” because it differs so much from person to person. The degree of muscle weakness and the muscles that are affected vary greatly from patient to patient and from time to time.
For most people, the first noticeable symptom is weakness of the eye muscles causing drooping eyelids or double vision. In others, difficulty in swallowing and slurred speech may be the first signs. The onset of the disease is usually gradual over weeks or months, but may be more sudden. Symptoms may come and go over time, and even resolve completely for months or longer. Symptoms often are not immediately recognized as MG, especially if they are subtle or variable.
Most individuals do not develop all of the symptoms of MG. In some patients weakness remains limited to the eyes for entire course of the disease. These patients have ocular MG. Most patients have generalized MG where symptoms also involve muscles besides the eyes. When muscles involving speech or swallowing are involved, this is sometimes called bulbar weakness.
MG symptoms differ somewhat for MG patients who test positive for MuSK antibodies. Most MuSK MG patients are women, and tend to have more severe symptoms. Researchers have found that this group of patients often require higher doses of prednisone, and tend to improve more with plasmapheresis than IVIg treatments.
The course of MG during pregnancy is hard to predict. For some women, symptoms worsen; in others symptoms stay the same or improve. Because MG increases risk during pregnancy and MG medications pose risks to an unborn child, a woman with MG should discuss pregnancy with her doctor in advance.
If a person’s ability to breathe, cough, or protect their airway becomes insufficient, it’s called a myasthenic crisis. These patients require prompt treatment, and may need mechanical breathing assistance in a hospital for a period of time until their strength improves. While most myasthenics never experience a crisis, those who have trouble swallowing and talking are the ones most likely also to have trouble breathing. Progressive warning signs that swallowing, talking, and breathing are becoming compromised should be addressed immediately.
The MG-Activities of Daily Life (MG-ADL) is one tool used by physicians to determine the impact of a person’s MG symptoms on activities such as chewing or rising from a chair. Click to read more about the MG-ADL.
This information was abstracted from these sources:
The Myasthenia Gravis Fact Sheet published by the National Institute of Neurological Disorders
(updated February 19, 2016) and retrieved April 27, 2016.
Information on MuSK antibody MG is from a study reported in Muscle & Nerve, July 2011 that reviewed patient data from 110 cases of MuSK related MG.
Additional medical references were used as well.
Reviewed by the Conquer MG Medical Advisory Board, April 2016.
Unless otherwise stated, the information provided here is of a general nature, composed by non-medical personnel. It is meant to be accurate and helpful advice for MG patients. It is not intended to be medical opinion, nor is it a substitute for personal professional medical care.