Myasthenia Gravis

  1. General information
    1. A neuromuscular disorder in which there is a disturbance in the transmission of impulses from nerve to muscle cells at the neuromuscular junction, causing extreme muscle weakness
    2. Incidence
      1. Highest between ages 15-35 for women, over 40 for men.
      2. Affects women more than men
    3. Cause: thought to be autoimmune disorder whereby antibodies destroy acetylcholine receptor sites on the postsynaptic membrane of the neuromuscular junction.
    4. Voluntary muscles are affected, especially those muscles innervated by the cranial nerves.
  2. Medical management
    1. Drug therapy
      1. Anticholinesterase drugs: ambenonium (Mytelase), neostigmine (Prostigmin), pyridostigmine (Mestinon)
        1. block action of cholinesterase and increase levels of acetylcholine at the neuromuscular junction
        2. side effects: excessive salivation and sweating, abdominal cramps, nausea and vomiting, diarrhea, fasciculations (muscle twitching)
      2. Corticosteroids: prednisone
        1. used if other drugs are not effective
        2. suppress autoimmune response
    2. Surgery (thymectomy)
      1. Surgical removal of the thymus gland (thought to be involved in the production of acetylcholine receptor antibodies)
      2. May cause remission in some clients especially if performed early in the disease
    3. Plasma exchange
      1. Removes circulating acetylcholine receptor antibodies
      2. Use in clients who do not respond to other types of therapy
  3. Assessment findings
    1. Diplopia, dysphagia
    2. Extreme muscle weakness, increased with activity and reduced with rest
    3. Ptosis, masklike facial expression
    4. Weak voice, hoarseness
    5. Diagnostic tests
      1. Tensilon test: IV injection of Tensilon provides spontaneous relief of symptoms (lasts 5-10 minutes)
      2. Electromyography (EMG): amplitude of evoked potentials decreases rapidly
      3. Presence of antiacetylcholine receptor antibodies in the serum
  4. Nursing interventions
    1. Administer anticholinesterase drugs as ordered.
      1. Give medication exactly on time.
      2. Give with milk and crackers to decrease GI upset.
      3. Monitor effectiveness of drugs: assess muscle strength and vital capacity before and after medication.
      4. Avoid use of the following drugs: morphine and strong sedatives (respiratory depressant effect), quinine, curare, procainamide, neomycin, streptomycin, kanamycin and other aminoglycosides (skeletal muscle blocking effects).
      5. Observe for side effects.
    2. Promote optimal nutrition.
      1. Mealtimes should coincide with the peak effects of the drugs: give medications 30 minutes before meals.
      2. Check gag reflex and swallowing ability before feeding.
      3. Provide a mechanical soft diet.
      4. If the client has difficulty chewing and swallowing, do not leave alone at mealtimes; keep emergency airway and suction equipment nearby.
    3. Monitor respiratory status frequently: rate, depth; vital capacity; ability to deep breathe and cough
    4. Assess muscle strength frequently; plan activity to take advantage of energy peaks and provide frequent rest periods.
    5. Observe for signs of myasthenic or cholinergic crisis.
      1. Myasthenic crisis
        1. abrupt onset of severe, generalized muscle weakness with inability to swallow, speak, or maintain respirations
        2. caused by undermedication, physical or emotional stress, infection
        3. symptoms will improve temporarily with Tensilon test.
      2. Cholinergic crisis
        1. symptoms similar to myasthenic crisis and, in addition, the side effects of anticholinesterase drugs (e.g., excessive salivation and sweating, abdominal cramps, nausea and vomiting, diarrhea, fasciculations)
        2. caused by overmedication with the cholinergic (anticholinesterase) drugs
        3. symptoms worsen with Tensilon test; keep atropine sulfate and emergency equipment on hand.
      3. Nursing care in crisis
        1. maintain tracheostomy or endotracheal tube with mechanical ventilation as indicated (see Mechanical Ventilation).
        2. monitor arterial blood gases and vital capacities.
        3. administer medications as ordered.
          1. myasthenic crisis: increase doses of anticholinesterase drugs as ordered.
          2. cholinergic crisis: discontinue anticholinesterase drugs as ordered until the client recovers.
        4. establish a method of communication.
        5. provide support and reassurance.
    6. Provide nursing care for the client with a thymectomy.
    7. Provide client teaching and discharge planning concerning
      1. Nature of the disease
      2. Use of prescribed medications, their side effects and signs of toxicity
      3. Importance of checking with physician before taking any new medications including OTC drugs
      4. Importance of planning activities to take advantage of energy peaks and of scheduling frequent rest periods
      5. Need to avoid fatigue, stress, people with upper-respiratory infections
      6. Use of eye patch for diplopia (alternate eyes)
      7. Need to wear Medic-Alert bracelet
      8. Myasthenia Gravis Foundation and other community agencies