An autoimmune neurologic disorder
Myasthenia Gravis
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
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
Pathophysiology
Assessment
Onset of the disorder may be suddenMany times, symptoms are not immediately
recognized as being related to myasthenia gravisIn most cases, weakness of the eye muscles is
noticed first.
Assessment - Severe Symptoms
Ptosis – drooping of one or both eyelidsDiplopia – blurred or double visionBulbar symptoms – weakness of muscles of the
face & throatBland facial expressionDifficulty swallowing – increased risk of choking &
aspirationDysarthia – impaired speechDysphonia – voice impairmentWeakness In arms, hands, legs, neckGeneralized weakness also effects intercostal
muscles, resulting in decreasing vital capacity and respiratory failure.
Confirming the DiagnosisAcetylcholinesterase 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 patient's 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 occurInterventions
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 #2Deficient knowledge R/T drug therapy, potential for crisis
(myasthenic or cholinergic), and self-care managementOverall goal: Patient will demonstrate knowledge of
medication management, importance of rest, coping strategies, and prevention/management of complications
InterventionsTeach 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 avoid overexertion.
If eyes cannot close properly, instruct patient to patch/tape eyes closed for short intervals to avoid corneal damage.
Treatment of myasthenia gravisPharmacologic 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: antibiotics, beta-blockers, antiseizure meds, Novocain, morphine and quinine.
Possible Side Effects of Anticholinesterase Meds
Central Nervous System
Respiratory/Cardiovascular
Skeletal Muscles
Irritability Bronchial relaxation Fasciculations
Anxiety Increased bronchial secretions
Spasms
Insomnia Tachycardia Weakness
Headache Hypotension Genitourinary
DysarthiaGastrointestinal
Frequency
Syncope Abdominal cramps Urgency
Seizures Nausea, vomiting and diarrhea Integumentary
Coma Anorexia Rash
Diaphoresis Increased Salivation Flushing
TreatmentsPlasmatheresis
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 globulinTreats exacerbations of myasthenia gravis
temporarily. This procedure does not work as quickly as plasmatheresis.
These are treatments for myasthenia gravis, not cures.
Treatments
Surgical TreatmentsThymectomy: 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.
References Doenges, 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 & Suddarth's textbook of medical-surgical nursing (11th ed.). Philadelphia: Lippincott Williams & Wilkins.
