Myasthenia Gravis

Introduction:

This is a disorder of the peripheral nervous system involving antibodies that have
been produced by the body; they bind to receptor sites that normally bind acetyl-
choline. This prevents the acetylcholine from binding to the receptor sites on the
skeletal muscle, inhibiting normal muscle contraction in the affected area. The
areas of the body most commonly affected by the autoimmune disease include the
muscles in the eyes, face, lips, tongue, throat, and neck, resulting in weakness and
fatigue of these areas. The disease does not seem to be hereditary, but does have
a family tendency toward autoimmune disorders. The majority of the patients
have a hyperplasia (excessive growth of normal cells) of the thymus gland.
Myasthenia gravis is more likely to develop in young adults and is more common
in women.

PROGNOSIS

The disease can take a variety of forms from mild weakness and drooping of the
eye muscles to generalized, progressive weakness that ultimately affects respira-
tory function. Progression of symptoms will vary from patient to patient. There are
typically episodes of exacerbations and remissions. The more aggressive form of
the disease progresses more rapidly, resulting in death from respiratory failure.

SIGNS AND SYMPTOMS

• Ptosis (drooping of the eyelid) due to muscular weakness
• Diplopia (double vision) due to inability to keep both eyes focused on the
same object
• Trouble closing eyes completely; dry eyes due to muscle weakness
• Difficulty swallowing (dysphagia) due to muscle weakness
• Muscle weakness later in the day due to fatigue
• Proximal muscle weakness
• Fatigue
• In advanced disease—loss of bowel and bladder control; difficulty with res-
piratory function
• Myasthenic crisis is an exacerbation of symptoms due to insufficient
medication:
• Tachycardia
• Tachypnea
• Elevated blood pressure
• Cyanosis
• Decrease in urinary output
• Incontinence of bowel and bladder
• Loss of gag reflex
• Cholinergic crisis is an exacerbation of weakness due to too much choliner-
gic medication:
• Blurred vision
• Nausea, vomiting, diarrhea
• Abdominal cramping
• Paleness
• Twitching of facial muscles
• Small pupils (miosis)
• Low blood pressure

TREATMENT

• Administer immunosuppressants to induce remission and help control
symptoms:
• prednisone or dexamethasone initially to improve symptoms
• azathioprine and cyclophosphamide in the long term to help control
symptoms
• Administer cholinesterase inhibitors for long-term control of symptoms. These
drugs have short duration of action, therefore have to be dosed several times
during the day:
• neostigmine

NURSING DIAGNOSES

• Impaired physical mobility
• Impaired verbal communication
• Ineffective air exchange
• Self-care deficit

NURSING INTERVENTION

• Encourage frequent rest periods.
• Monitor vital signs.
• Monitor nutritional intake.
• Monitor weight.
• Monitor neurologic status for changes in pupil reaction, extraocular move-
ments, eyelid movement, facial symmetry, hand grip strength, coordination,
fine motor skills, and gait.
• Monitor respiratory status for changes in rate, effort, skin color, use of acces-
sory muscles, or change in mental status.
• Monitor gag reflex.
• Arrange for appropriate communication with staff if patient is unable to use
call bell system or unable to be heard over intercom from room.
• Explain to the patient:
• Home care needs.
• Medication use; need to maintain time schedule for medications.
• Time meals one hour after medications to decrease chance of aspiration.
• Teach use of oral-pharyngeal suctioning catheter to clear secretions.
• Avoid heat extremes (hot tubs, saunas).
• pyridostigmine
• ambenonium
• Administer natural tears or other lubricant to keep eyes moist:
• patch eyes if unable to close
• High-calorie diet of appropriate food type—patient may have difficulty
swallowing.
• Removing antibodies from plasma (plasmapheresis) may be beneficial.
• BiPAP or CPAP for enhanced air movement and oxygenation.
• Thymectomy (surgical removal of thymus gland) for patients with thymoma.
• Avoid aminoglycoside antibiotics which may exacerbate symptoms.
• Alcohol may exacerbate symptoms.