Myasthenia GravisAn autoimmune neurologic disorder By Lexi Gray & Mary Kacic
Background Myasthenia gravis means “grave muscle weakness” It is an autoimmune disease affecting the myoneural junction About 60,000 people in the U.S. have this disease Women affected more frequently than men, at around 20-40 years of age. Men develop it later, at around 60-70 years of age.
Symptoms Causes varying degrees of skeletal muscle weakness Hallmark of the disease: muscle weakness increases during periods of activity and improves during rest. Areas that MAY be affected: eyes/eyelid movement, facial expression, chewing, talking, swallowing
Pathophysiology Normal communication between the nerve and muscle is interrupted at the neuromuscular junction (where nerve cells meet with the muscles they control) Normally, nerve endings release acetylcholine which travels through the NMJ and binds to receptors, causing muscle contraction. In myasthenia gravis, these receptors are blocked or destroyed
Pathophysiology Autoimmune disease: the antibodies that attack or block the acetylcholine receptors are produced by the body’s own immune system Thymic hyperplasia or a thymic tumor is present in 80% of people with myasthenia gravis
Assessment Onset of the disorder may be sudden Many times, symptoms are not immediately recognized as being related to myasthenia gravis In most cases, weakness of the eye muscles is noticed first.
Assessment - Severe Symptoms Ptosis – drooping of one or both eyelids Diplopia – blurred or double vision Bulbar symptoms – weakness of muscles of the face & throat Bland facial expression Difficulty swallowing – increased risk of choking & aspiration Dysarthia – impaired speech Dysphonia – voice impairment Weakness In arms, hands, legs, neck Generalized weakness also effects intercostal muscles, resulting in decreasing vital capacity and respiratory failure.
Confirming the Diagnosis Acetylcholinesterase Inhibitor Test Confirms the diagnosis of myasthenia gravis. During this test, the breakdown of acetylcholine is stopped. As a result, acetylcholine is able to accumulate at the receptor sites. For this test, edrophoniumchloride is administered IV. Facial muscle weakness and ptosis will resolve about 30 second after the drug is administered, if the patient is positive for a myasthenia gravis diagnosis. This relief lasts only 5 minutes, so it is not considered a treatment. After the drug is administered, the patients serum is then tested for acetylcholine receptor antibodies, which would also be consistent with the diagnosis. In some cases, patients with myasthenia gravis may have an enlarged thymus gland.
Nursing Diagnosis #1 Risk for aspiration R/T difficulty swallowing, weakness of bulbar muscles Overall goal: No aspiration will occur Interventions Give meals with anticholinesterase meds to inhibit breakdown of acetylcholine and increase its concentration at the NMJ Raise the HOB to semi-fowler’s position, which will ensure upper airway patency. Give food with a pudding-like consistency, which can be more easily swallowed.
Nursing Diagnosis #2 Deficient knowledge R/T drug therapy, potential for crisis (myasthenic or cholinergic), and self- care management Overall goal: Patient will demonstrate knowledge of medication management, importance of rest, coping strategies, and prevention/management of complications Interventions Teach patient about the actions of meds, and importance of regimen. The patient will verbalize the consequences delaying med intake, including S&S of myasthenic and cholinergic crisis. Teach strategies for patient to conserve their energy. The patient will develop coping strategies to
Treatment of myasthenia gravis Pharmacologic Treatment First-line med is pyridostrigmine bromide (Mestinon), an anticholinesterase that inhibits the breakdown, thus improving skeletal muscle contraction. Side effects can include fasciculations, abdominal pain, diarrhea. Immunosuppressive Therapy: Corticosteroids decrease the amount of antibody production. Cytotoxic meds (Azathioprine) inhibits production of T-and B-cells, and effects may not be seen for 3-12 months. Hepatotoxicity is a risk of using cytotoxic meds. Some common medications exacerbate the symptoms of myasthenia gravis, including:
Possible Side Effects ofAnticholinesterase Meds Central Respiratory/ Skeletal Muscles Nervous System Cardiovascular Irritability Bronchial relaxation Fasciculations Anxiety Increased bronchial Spasms secretions Insomnia Tachycardia Weakness Headache Hypotension Genitourinary Dysarthia Frequency Gastrointestinal Syncope Abdominal cramps Urgency Seizures Nausea,vomiting and diarrhea Integumentary Coma Anorexia Rash Diaphoresis Increased Salivation Flushing
Treatments Plasmatheresis This procedure removes the patient’s plasma and plasma components through a centrally placed catheter. Blood cells are separated from antibody- containing plasma. The blood cells are then mixed with plasma substitute and reinfused. Provides temporary treatment for severe symptoms. Intravenous immune globulin Treats exacerbations of myasthenia gravis temporarily. This procedure does not work as quickly as plasmatheresis. These are treatments for myasthenia gravis, not cures.
Treatments Surgical Treatments Thymectomy: Surgical removal of the thymus gland, which may result in the production of antigen-specific immunosuppression, which results in clinical improvement. Results vary; patient may have partial or complete remission, or no remission at all. Nursing considerations for the patient who received a thymectomy include monitoring respiratory function and mechanical ventilation.
Myasthenia (or cholinergic) Crisis Exacerbation of the disease process. Signs & symptoms include muscle/bulbar weakness. Causes for myasthenia crisis may include a respiratory infection, pregnancy, or medications. Primary management is focused on maintaining the airway. The nurse assesses respiratory rate, depth, breath sounds, and pulmonary function. Endotracheal intubation and mechanical ventilation may be necessary. Assess arterial blood gases, I&O, daily weight. Avoid sedatives and tranquilizers. Bradycardia and respiratory distress (emergency situations) are treated with atropine.
ReferencesDoenges, M., Moorhouse, M., Murr, A. (2010). Nurse’s Pocket Guide: Diagnoses, Prioritized Interventions, and Rationales (12th ed.). Philadelphia: F.A. Davis. ISBN: 0803622341.Smeltzer, S. C., Bare, B. G., Hinkle, J. L. & Cheever, K. H. (eds.) (2008). Brunner & Suddarths textbook of medical-surgical nursing (11th ed.). Philadelphia: Lippincott Williams & Wilkins.