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The name myasthenia gravis means "grave muscle weakness" in reference to its hallmark symptom. Myasthenia gravis is an [|autoimmune disease] that inhibits the function of skeletal muscles, causing marked weakness in affected patients.
 * __ BACKGROUND: WHAT IS MYASTHENIA GRAVIS __**

Patients with myasthenia gravis are likely to report muscle weakness that increases during periods of activity and improves during periods of rest(3). Certain muscles such as those that control the eye and eyelid movement, facial expression, chewing, talking, and swallowing are often but not always involved in the disorder.

Approximately 60,000 people have myasthenia gravis in the United States(4).
 * __ DEMOGRAPHICS __**

Hospital admission rates suggest that myasthenia gravis is "a disease of young women and old men"(1) and that mortality rates are low for patients admitted to the hospital for the condition. Women are affected more frequently than men, and they tend to develop the disease at an earlier age (20-40 years of age). Men tend to develop the disease at 60-70 years of age.

Of the people who are diagnosed with myasthenia gravis: 72.6% are Caucasian and 61.6% are female. The length of stay for hospital admissions related to myasthenia gravis is between 2-7 days(1) ([|Incidence and Mortality Rates.pdf]).

Myasthenia gravis is caused by a defect in the transmission of nerve impulses to muscles(5). It occurs when normal communication between the nerve and muscle is interrupted at the neuromuscular junction – the place where nerve cells communicate with the muscles they control.
 * __ PATHOPHYSIOLOGY __**

In the absence of myasthenia gravis, impulses travel down the nerve, which prompts the nerve endings release a neurotransmitter substance called acetylcholine. Typically, acetylcholine binds to acetylcholine receptor sites, and muscle contraction is stimulated(5).

In myasthenia gravis, the patient's antibodies block the receptors for acetylcholine at the neuromuscular junction. Without a sufficient amount of receptor sites, the acetylcholine can't do its job and the muscles are not successfully stimulated into contraction. The antibodies blocking acetylcholine receptor sites are a misfiring of the body's immune system(5).

Approximately 80 percent of those diagnosed with myasthenia gravis test positive for the antibody type that causes the disease(5). For those who test negative for the antibody, "researchers believe that the offending antibody is directed at a portion of the receptor site rather than the whole complex"(5).

//(Copyright Wolters Kluwer 2008)//

The cells that attack the receptor sites are primarily T-cells released by the thymus gland. Thymic hyperplasia and thymic tumor are fairly common among patients with myasthenia gravis(5).

Myasthenia gravis is purely a motor disorder with no effect on sensation or coordination. The onset of the disorder may be sudden. The presenting symptoms of the disease are often generalized, and may not explicitly point to a diagnosis of myasthenia gravis. In many cases, the first noticeable symptom is weakness of the eye muscles.
 * __ WHAT ARE SYMPTOMS OF MYASTHENIA GRAVIS __**

(Posey & Spiller)

__ Localized symptoms: __
 * limited to eye muscles

__ Severe or generalized 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: increase 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.

An acetylcholinesterase inhibitor test confirms the diagnosis of myasthenia gravis. During this test, acetylcholine breakdown is halted, which gives it the ability to build up at receptor sites and work effectively with the skeletal muscles(5).
 * DIAGNOSIS **

For this test, edrophonium chloride 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. After the drug is administered, the patient's serum is then tested for acetylcholine receptor antibodies, which would also be consistent with the diagnosis(5).

In some cases, patients with myasthenia gravis may have an enlarged thymus gland, and the clinician may order an MRI to identify this complication(5).

The treatment of myasthenia gravis "is directed at improving function and reducing and removing circulating anibodies"(5). In a study of treatment in the hospital setting, common medical interventions were thymectomy (removal of the thymus), plasmapheresis (plasma exchange), and IV immune glomulin (IVIG)(1).
 * TREATMENT **

Plasmapheresis is a procedure that removes the patient's plasma and plasma components, and the plasma containing acetylcholine receptor antibodies is removed and replaced with a substitute plasma free of those antibodies. The new plasma substance is then administered to the patient, and the result is that the body has fewer circulating acetylcholine receptor antibodies(5). The relief is immediate, and lasts several weeks.

IVIG is an easier procedure than plasma exchange, but the body's response is slower.

First-line pharmocologic treatment is pyridostigmine bromide (a cholinesterase inhibitor). This medicine promotes accumulation of acetylcholine, which stimulates skeletal muscle contraction, helping to reverse the severe muscle weakness often seen with myasthenia gravis(5).
 * MEDICATIONS **

Immunosuppressive therapy (corticosteroids and azathioprine) suppresses immune responses and blocks autoantibody production (T-cells). The drug regimen includes long-term treatment with prednisone. With azathioprine, the effects of treatment may not occur for 3-12 months and patients are monitored for hepatotoxicity (4).

Patients with myasthenia gravis should be aware of all medications that may exacerbate the symptoms of their condition, including: antibiotics, cardiovascular and antiseizure medications, morphine, quinine, beta-blockers, and Novocain. Atropine can mask a cholinergic crisis. Patients should also be aware of the long-term side effects related to corticosteroid use, such as osteoporosis, hypertension, hyperglycemia, and weight gain(4).

For patients with myasthenia gravis who are undergoing surgical treatment, nitrous oxide should be used with caution – it may cause respiratory depression and prolonged hypnotic effects.

The priority nursing diagnoses are as follows: Risk for aspiration R/T difficulty swallowing, weakness of bulbar muscles Recommended interventions(2): > Deficient knowledge R/T drug therapy, potential for crisis (myasthenic or cholinergic), and self-care management Recommended interventions:
 * Priority Nursing Diagnoses(2) **
 * Give meals with anticholinesterase meds to inhibit breakdown of acetylcholine and increase it 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.
 * 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 avoid overexertion.
 * If eyes cannot close properly, instruct patient to patch/tape eyes closed for short intervals to avoid corneal damage.

Click below for a PDF containing these nursing diagnoses and outcomes. [|Myasthenia Gravis Nursing Diagnoses.pdf].

Other possible nursing diagnoses for myasthenia gravis include the following:
 * 1)   Ineffective Breathing Pattern  related to respiratory muscle weakness.
 * 2) Impaired Physical Mobility related to weakness of voluntary muscles.
 * 3) Fatigue related to increased energy needs from muscular involvement.
 * 4) Self-Care Deficit related to muscle weakness, general fatigue.
 * 5) Imbalanced Nutrition: Less than Body Requirements related to dysphagia, intubation, or muscle paralysis.

Respiratory failure is with myasthenia gravis patients is linked to mortality rates(1). "Neuromuscular respiratory failure is the critical complication in myasthenic and cholinergic crisis. Respiratory muscle and bulbar weakness combine to cause respiratory compromise"(4).
 * COMPLICATIONS: Respiratory Failure**

Myasthenic crisis is an emergency situation, and a potential risk for all patients with myasthenia gravis. Signs and symptoms include muscle or bulbar weakness. Causes for myasthenia crisis may include a respiratory infection, pregnancy, or medications(4).
 * MYASTHENIC CRISIS **

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. The nurse should also assess arterial blood gases, input and output, and daily weight. Bradycardia and respiratory distress resulting from myasthenic crisis (emergency situations) are treated with atropine(4). If the patient's core muscle are not functioning, they may not be able to clear secretions by coughing and will be at risk for aspiration. They may need chest physical therapy "including postural drainage to mobilize secretions and suctioning to remove secretions"(4).

Approximately 15-20 percent of patients with MG experience this emergency exacerbation, and usually within the first two years of diagnosis. For myasthenic crisis, the length of hospital stay is 4-12 days.

**OUTCOMES FOR THE MYASTHENIA GRAVIS PATIENT**
 * Patient will verbalize an understanding of medications, including their action, when to take them, side effects, and consequences of neglecting drug regimen.
 * The patient will demonstrate knowledge of actions that can be taken to conserve energy. They will recognize the limitations of their condition and modify daily life accordingly.
 * Aspiration will not occur, and the patient will eat meals at the same time their medications will take effect. The patient will sit upright during all meals, and flex the neck slightly to facilitate swallowing. The patient will demonstrate this technique.
 * The patient will verbalize knowledge of the methods needed to preserve vision and avoid corneal damage.
 * Arterial blood gases, serum electrolytes, input and output, and daily weight will all be within normal limits for the patient(4).


 * References **

1) Alshekhlee, A., Miles, J. D., Katirji, B., Preston, D. C., & Kaminski, H. J. (2009). Incidence and mortality rates of myasthenia gravis and myasthenic crisis in US hospitals. //Neurology//, //72//(May), 1548-1553.

2) Doenges, M., Moorhouse, M., Murr, A. (2010). Nurse’s Pocket Guide: Diagnoses, Prioritized Interventions, and Rationales (12th ed.). Philadelphia: F.A. Davis. ISBN: 0803622341.

3) Myasthenia gravis fact sheet: National Institute of Neurological Disorders and Stroke (NINDS). (n.d.). National Institute of Neurological Disorders and Stroke (NINDS). Retrieved March 30, 2012, from: http://www.ninds.nih.gov/disorders/myasthenia_gravis/detail_myasthenia_gravis.htm#179983

4) 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