An autoimmune neurologic disorder

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Myasthenia Gravis

• An autoimmune neurologic disorder

By Lexi Gray Mary Kacic
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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.

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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

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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

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Pathophysiology

• Autoimmune disease the antibodies that attack or
  block the acetylcholine receptors are produced by
  the bodys own immune system
• Thymic hyperplasia or a thymic tumor is present
  in 80 of people with myasthenia gravis

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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.

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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.

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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 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.

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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-fowlers position, which
  will ensure upper airway patency.
• Give food with a pudding-like consistency, which
  can be more easily swallowed.

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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
  SS 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.

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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 antibiotics,
  beta-blockers, antiseizure meds, Novocain,
  morphine and quinine.

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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
Dysarthia Gastrointestinal Frequency
Syncope Abdominal cramps Urgency
Seizures Nausea, vomiting and diarrhea Integumentary
Coma Anorexia Rash
Diaphoresis Increased Salivation Flushing
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Treatments

• Plasmatheresis
• This procedure removes the patients 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.
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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.

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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, IO, daily weight.
• Avoid sedatives and tranquilizers.
• Bradycardia and respiratory distress (emergency
  situations) are treated with atropine.

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References

• Doenges, M., Moorhouse, M., Murr, A. (2010).
  Nurses 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.