What is Myasthenia Gravis ?
Myasthenia gravis produces sporadic but progressive weakness and abnormal fatigability of striated (skeletal) muscles. Muscle weakness is exacerbated by exercise and repeated movement but improved by anticholinesterase drugs. Usually, myasthenia gravis affects muscles innervated by the cranial nerves (face, lips, tongue, neck, and throat), but it can affect any muscle group. It commonly accompanies immune and thyroid disorders. In fact, 15% of myasthenic patients have thymomas. When the disease involves the respiratory system, it may be life-threatening.
Myasthenia gravis follows an unpredictable course of recurring exacerbations and periodic remissions. No cure is known, but drug treatment has improved the prognosis and allows patients to lead relatively normal lives except during exacerbations.
Myasthenia gravis occurs at any age, but incidence is highest in women ages 18 to 25 and in men ages 50 to 60. About three times as many women as men develop this disease.About 20% of infants born to myasthenic mothers have transient (or occasionally persistent) myasthenia. Spontaneous remissions occur in about 25% of patients.
Causes of Myasthenia Gravis
Myasthenia gravis is thought to be an autoimmune disorder. For an unknown reason, the patient's blood cells and thymus gland produce antibodies that block, destroy, or weaken the neuroreceptors that transmit nerve impulses, causing a failure in transmission of nerve impulses at the neuromuscular junction.
Signs & Symptoms of Myasthenia Gravis
The first noticeable symptoms of myasthenia gravis may be weakness of the eye muscles, difficulty in swallowing, or slurred speech. Symptoms vary in type and severity. Patients often have nasal-sounding speech and weak neck muscles that give the head a tendency to fall forward or backward. These symptoms occur in about 90% of MG cases, are usually intermittent (i.e., come and go), and may disappear for weeks and then recur.
Generalized weakness often develops in the trunk, arms, and legs within a year of onset. Arm muscles usually are affected most severely. Muscle weakness tends to worsen as the day progresses, especially after prolonged activity.
Myasthenia gravis is diagnosed using a number of tests including:
Measures to relieve symptoms may include anticholinesterase drugs, such as neostigmine and pyridostigmines. These drugs counteract fatigue and muscle weakness and allow about 80% of normal muscle function. They become less effective as the disease worsens. Corticosteroids may also help to relieve symptoms. I.V. immune globulin is also used for acute exacerbations.
Some patients may undergo plasmapheresis if medications prove ineffective. This procedure is used to remove acetylcholine-receptor antibodies and temporarily reduce the severity of symptoms. I. V. immune globulin is also used for acute exacerbations.
Patients with thymomas require thymectomy, which leads to remission in adult-onset myasthenia in about 40% of patients if done in the first 2 years after diagnosis.Acute exacerbations that cause severe respiratory distress (myasthenic crisis) necessitate emergency treatment. Tracheotomy, ventilation with a positivepressure ventilator, and vigorous suctioning to remove secretions usually bring improvement in a few days. Because anticholinesterase drugs aren't effective in myasthenic crisis, they're discontinued until respiratory function begins to improve. Such a crisis requires immediate hospitalization and vigorous respiratory support.
Myasthenia gravis cannot be prevented, but avoiding the following triggers may help patients prevent exacerbations:
(c)Copyright Family-health-information.com All rights reserved
Disclaimer :- The content in this web site are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor. The web site is build for information and educational purpose only. If you are ill from any disease or notice medical symptoms, you should consult your doctor. We will not be liable for any complications or other medical accidents arising from or in connection with the use of or reliance upon any information in this web site.