Myasthenia Gravis - Causes, Symptoms And Treatment

Myasthenia :- from the Greek words, myelos, meaning muscle, and astheneia, meaning weakness

Gravis :- from the Latin word, gravidus, meaning heavy (serious)

Myasthenia gravis causes sporadic but progressive weakness and abnormal fatigability of striated (skeletal) muscles. Symptoms are exacerbated by exercise and repeated movement and relieved by anticholinesterase drugs. Usually, this disorder affects muscles innervated by the cranial nerves (face, lips, tongue, neck, and throat) but can affect any muscle group.

Myasthenia gravis follows an unpredictable course of periodic exacerbations and remissions. There's no known cure. Drug treatment has improved the prognosis and allows patients to lead relatively nonnative, except during exacerbations. When the disease involves the respiratory system, it may be life-threatening.

Myasthenia gravis affects 1 in 25,000 people at any age, but incidence peaks between ages 20 and 40. It's three times more common in women than in men in this age-group; however, after age 40, the incidence is similar in women and men.

About 20% of infants born to mothers with myasthenia gravis have transient (or occasionally persistent) myasthenia for 2 to 3 weeks. This disease may coexist with immune and thyroid disorders; 15% of patients with myasthenia gravis have thymomas. Remissions occur in about 25% of patients.

What causes Multiple sclerosis?

Myasthenia gravis causes a failure in transmission of nerve impulses at the neuromuscular junction. The site of action is the postsynaptic membrane. Theoretically, antireceptor antibodies block, weaken, or reduce the number of acetylcholine receptors available at each neuromuscular junction, impairing muscle depolarization necessary for movement.

The exact cause of myasthenia gravis is unknown. However, it's believed to be the result of:

• autoimmune response
• ineffective acetylcholine release
• inadequate muscle fiber response to acetylcholine.

In addition, certain medications, such as antibiotics, beta-adrenergic blockers, lithium, magnesium, Proscar, verapamil, and quinidine, can exacerbate the disease.

Signs and symptoms of Multiple sclerosis

Myasthenia gravis may occur gradually or suddenly. Signs and symptoms include:

• weak eye closure, ptosis, and diplopia from impaired neuromuscular transmission to the cranial nerves supplying the eye muscles (may be the only symptom present).
• skeletal muscle weakness and fatigue, increasing through the day but decreasing with rest (in the early stages, easy fatigability of certain muscles with or without other findings and, later, possibly severe enough to cause paralysis)
• progressive muscle weakness and accompanying loss of function, depending on the muscle group affected, that becomes more intense during menses and after emotional stress,prolonged exposure to sunlight or cold, or infections
• blank and expressionless facial appearance and nasal vocal tones secondary to impaired transmission of cranial nerves innervating the facial muscles
• frequent nasal regurgitation of fluids and difficulty chewing and swallowing from cranial nerve involvement
• drooping eyelids from weakness of facial and extra ocular muscles
• weakened neck muscles that may become too weak to support the head without bobbing, causing the patient to tilt her head back to be able to see . weakened respiratory muscles, decreased tidal volume and vital capacity from impaired transmission to the diaphragm making breathing difficult and predisposing the patient to pneumonia and other respiratory tract infections
• respiratory muscle weakness (myasthenic crisis) that's possibly severe enough to require an emergency airway and mechanical ventilation.

Complications of myasthenia gravis may include:

• respiratory distress
• pneumonia
• aspiration
• myasthenic or cholinergic crisis.

Diagnosis information

Tests to help diagnose myasthenia gravis include:

• The tensilon test confirms diagnosis of myasthenia gravis, revealing temporarily improved muscle function within 30 to 60 seconds after I.V. injection of edrophonium or neostigmine and lasting up to 30 minutes. . Electromyography with repeated neural stimulation shows progressive decrease in muscle fiber contraction. . Serum antiacetylcholine antibody titer may be elevated.
• Chest X-ray reveals thymoma (in approximately 15% of patients).

Treatment of Multiple sclerosis

Treatment of myasthenia gravis may include:

• anticholinesterase drugs, such as neostigmine (Prostigmin) and pyridostigmine (Mestinon), to counteract fatigue and muscle weakness and allow about 80% of normal muscle function aess effective as disease worsens)
• immunosuppressant therapy with corticosteroids, azathioprine amuran), cyclosporine (Sandimmune) and cyclophosphamide (Cytoxan) used in a progressive fashion (moving on to next drug when previous drug response is poor) to decrease the immune response toward acetylcholine receptors at the neuromuscular junction.
• immunoglobulin G (BayGam) during acute relapses or plasmapheresis in severe exacerbations to suppress the immune system.
• thymectomy to remove thymomas and possibly induce remission in some cases of adult-onset myasthenia, tracheotomy, positive-pressure ventilation, and vigorous suctioning to remove secretions for treatment of acute exacerbations that cause severe respiratory distress.
• in myasthenic crisis, discontinuation of anticholinesterase drugs until respiratory function improves as well as immediate hospitalization and vigorous respiratory support.

There are several medications that may make symptoms worse and should be avoided. Therefore, it is always important to check with your doctor about the safety of a medication before taking it.

Crisis situations, where muscle weakness involves the breathing muscles, may occur. These attacks seldom last longer than a few weeks. Hospitalization and assistance with breathing may be required during these attacks. Often plasmapheresis is used to help end the crisis.

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Complications

• Restrictions on lifestyle (possible)
• Side effects of medications (see the specific medication)
• Complications of surgery
• Myasthenic crisis (breathing difficulty), may be life threatening

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Special considerations and Prevention

Careful baseline assessment, early recognition and treatment of potential crises, supportive measures, and thorough patient teaching can minimize exacerbations and complications of myasthenia gravis. Continuity of care is essential. Care measures include:

• Establish an accurate neurologic and respiratory baseline. Thereafter, monitor tidal volume and vital capacity regularly. The patient may need a ventilator and frequent suctioning to remove accumulating secretions.
• Be alert for signs of an impending myasthenic crisis (increased muscle weakness, respiratory distress, and difficulty talking or chewing).
• Be alert for signs of impending cholinergic crisis (profound weakness, increased respiratory secretions, and respiratory failure).
• To prevent relapses, adhere closely to the ordered drug administration schedule. Be prepared to give atropine for anticholinesterase overdose or toxicity.
• Plan exercise, meals, patient care, and activities to make the most of energy peaks. For example, give medication 20 to 30 minutes before meals to facilitate chewing or swallowing. Allow the patient to participate in his care.
• When swallowing is difficult, give soft, solid foods instead of liquids to lessen the risk of choking.
• After a severe exacerbation, try to increase social activity as soon as possible.
• Patient teaching is essential because myasthenia gravis is usually a lifelong condition. Help the patient plan daily activities to coincide with energy peaks. Stress the need for frequent rest periods throughout the day. Emphasize that periodic remissions, exacerbations, and day-to-day fluctuations are common.
• Teach the patient how to recognize adverse effects and signs of anticholinesterase toxicity (headaches, weakness, sweating, abdominal cramps, nausea, vomiting, diarrhea, excessive salivation, and bronchospasm) and corticosteroid toxicity (euphoria. insomnia, edema, and increased appetite).
• Warn the patient to avoid strenuous exercise, stress, infection, and needless exposure to the sun or cold. All of these things may worsen signs and symptoms. Wearing an eye patch or glasses with one frosted lens may help the patient with diplopia.
• Encourage the patient to wear medical identification jewelry at all times.