eMedicine Specialties > Emergency Medicine > Neurology

Myasthenia Gravis: Follow-up

Author: William D Goldenberg, MD, Clinical Assistant Instructor, Department of Emergency Medicine, Kings County Hospital Center and SUNY Downstate Medical Center
Coauthor(s): Richard H Sinert, DO, Associate Professor of Emergency Medicine, Clinical Assistant Professor of Medicine, Research Director, State University of New York College of Medicine; Consulting Staff, Department of Emergency Medicine, Kings County Hospital Center
Contributor Information and Disclosures

Updated: Jan 30, 2009

Follow-up

Further Inpatient Care

• Patients who present to the ED with myasthenic or cholinergic crisis or with increasing muscle weakness of a less severe degree require admission to a monitored setting because their course is unpredictable.¹⁶   
• Patients with complications of the disease or treatment are admitted to a level of care corresponding to the nature and severity of the complication.  
• Patients with pneumonia should be admitted because they often are taking immunosuppressing medications and are at a high risk for aspiration pneumonia.  
  • Plasmapheresis has been found to be an effective short-term treatment of acute exacerbations of myasthenia gravis.¹⁷ Plasmapheresis removes circulating antibodies including the autoimmune antibodies responsible for the disease.
  • Clinical improvement takes several days to occur and lasts up to 3 weeks.¹¹ Because of the delayed onset of beneficial effects, plasmapheresis has limited utility in the ED setting.
• Immunotherapy with intravenous gamma globulin appears to diminish the activity of the disease for unknown reasons. The benefit begins within 2 weeks and may last for several months. Approximately 65% of patients with myasthenia gravis respond to intravenous gamma globulin.³
• Thymectomy is associated with clinical improvement in 85% of cases, and 35% of patients appear to have complete remission.¹   
  • Patients past the age of puberty and younger than 50 years should have elective thymectomy as part of their treatment.¹⁸
  • The need for anticholinesterase medication fluctuates significantly in the postoperative period but overall is less than it was prior to thymectomy.²

Further Outpatient Care

• All patients with myasthenia gravis should be referred to a neurologist for ongoing care.

Inpatient & Outpatient Medications

• Pyridostigmine
• Prednisone
• Azathioprine
• Cyclosporine

Transfer

• Patients with severe exacerbations of myasthenia gravis or cholinergic crisis should be transferred only after they have been stabilized and the airway has been secured.
• Persistent hypoxemia, hypercarbia, dysrhythmias, or unstable vital signs make transfer unwise, unless appropriate care cannot be delivered at the original facility.

Complications

• The most common severe complication of myasthenia gravis is respiratory failure, which often presents with the rapid deterioration of respiratory effort that ultimately results in apnea.
• Hypoxemia and respiratory acidosis often render the patient somnolent or unresponsive, in which case a clear history may be difficult to obtain.
• Pneumonia is a common complication in patients with myasthenia gravis and often is the cause of death in fatal cases.
• Community-acquired pneumonia often is more severe in patients with myasthenia gravis because of their marginal respiratory function, inability to cough effectively, and inability to maintain tachypnea for long periods. Other types of pneumonia are more common in patients with myasthenia gravis because these patients have a higher risk of aspiration. They also have relative immunocompromise because of immunosuppressive medications. Consequently, these patients are at risk for aspiration pneumonia with mixed aerobic and anaerobic organisms, as well as unusual organisms associated with immunocompromise (eg, Pseudomonas, other gram-negative organisms, fungi).
• Chronic respiratory insufficiency
• Medication effects  
  • Excessive use of cholinesterase inhibitors can result in a cholinergic crisis.
  • Chronic use of corticosteroids can result in a large number of serious complications, including opportunistic infection, GI bleeding, hyperglycemia, osteoporosis, aseptic necrosis, and cataract formation.
  • Other immunosuppressive medications increase the incidence of opportunistic infections, renal insufficiency, and hypertension.

Prognosis

• Given the current treatment that combines cholinesterase inhibitors, immunosuppressive drugs, plasmapheresis, immunotherapy, and supportive care in an ICU setting (when appropriate), most patients with myasthenia gravis have a near-normal life span.
• Thymectomy results in complete remission of the disease in a number of patients. However, the prognosis is highly variable, ranging from remission to death.
• The mortality rate is probably less than 4%.

Miscellaneous

Medicolegal Pitfalls

• Failure to recognize impending respiratory failure
• Failure to institute appropriate monitoring and treatment, resulting in precipitous decompensation and death
• Myasthenia gravis (MG) can mimic other diagnoses in elderly persons and vice versa. Examples of such pathology include diagnoses such as congestive heart failure, pulmonary embolism, and acute myocardial infarction.

Special Concerns

• Myasthenia gravis can be transmitted vertically from an affected mother to her fetus.
• Transplacental transfer of maternal autoantibodies against the ACh receptor results in the syndrome of neonatal myasthenia.
• Infants affected by this condition are floppy at birth, and they display poor sucking, muscle tone, and respiratory effort. They often require respiratory support and intravenous feeding as well as monitoring in a neonatal ICU.
• As the transferred maternal antibodies are metabolized over several weeks, symptoms abate and the infants develop normally.
• Treatment with cholinesterase inhibitors is effective in this age group as well. However, the dosage must be carefully titrated to clinical effect.
• Approximately 10% of infants of mothers with myasthenia gravis develop clinical signs of neonatal myasthenia gravis.
• Although most of these cases are apparent within 48 hours, the presentation may be delayed as long as 10 days after delivery. This delayed presentation should be kept in mind when evaluating newborn infants in the ED for weakness or poor feeding.

The authors and editors of eMedicine gratefully acknowledge the contributions of previous authors, Edward Newton, MD, and Nick Testa, MD, to the development and writing of this article.

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