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Wednesday, January 29, 2014
Myasthenia gravis is an uncommon auto-immune disease, characterised by muscle weakness.
Common symptoms of Myasthenia Gravis
Myasthenia gravis presents with symptoms due to weakness of various muscles.
Common presentations of this include:
1. Drooping of one or both eyelids (usually, there is a difference in the degree of eyelid drooping). Drooping of eyelid is also called as ptosis.
2. Double vision, on looking up, down, left, right or sideways.
3. Slurring of speech or nasal twang in voice,
4. Difficulty in chewing food,
5. Difficulty in swallowing food, or nasal regurgitation of liquids,
6. Weakness of arms or legs,
7. Breathing difficulty,
8. Difficulty in holding neck straight (tends to droop forwards)
The sensations are normal in the affected parts of body.
Urinary and bowel control is preserved.
Please also note
1. Symptoms may vary at different times of day, most often they are worse in evenings,
2. There is fatiguability, symptoms get worse on repeating the same movements,
3. There may be periods (days to weeks) of remission, when all symptoms seem to disappear, only to return back later.
The following factors may trigger or worsen exacerbations:
How do we confirm the diagnosis of myasthenia gravis?
1. Clinical symptoms, as described above make us suspect a diagnosis of MG,
2. Tensilon test- where tensilon (edrophonium) injection is given, after which there is temporary improvement of symptoms such as ptosis,
3. Repetitive nerve stimulation- This test in done in the electrophysiology laboratory, where the muscle fatigue is shown (by seeing reduced amplitude with repeated stimulation of muscles),
4. Anti-Acetylcholine receptor antibody levels are elevated in about 80% of people. These antibodies are supposed to be released from thymus gland (located behind the upper chest wall in the centre). These antibodies prevent the action of acetylcholine on the muscles, making them weak.
5. CT scan of chest is done to look for enlargement or tumor in thymus gland.
6. Other less common antibodies seen in some patients with MG are anti-straited muscle antibody, anti-MuSK antibody, and anti-striational antibody.
What is the medical management of Myasthenia Gravis?
The medical management is classified into two categories:
1. Symptomatic treatment- to improve the symptoms. Pyridostigmine is commonly used.
We usually start a dose of 60 mg two times daily, and the maximum dose can be unto 720 mg per day.
Common side effects include increased salivation, abdominal pain and cramps, diarrhoea, muscle twitchings, etc.
2. Definitive treatment- is used to suppress the antibodies.
Steroids are commonly used.
Other agents used are azathioprine, mycophenolate, cyclosporine, methotrexate, and cyclophosphamide.
3. In patients with myasthenic crisis (severe disease requiring feeding tube due to swallowing problem), or requiring mechanical ventilation (due to respiratory distress), PLASMAPHERESIS (blood is purified, and antibodies are removed, something similar to dialysis) or IV IMMUNOGLOBULINS (injections are given by drip over five days) are required.
4. THYMECTOMY- the best and permanent treatment for MG is thymectomy operation. In this, the thymus gland located behind the sternum bone (chest wall) is removed by operation. This removes the source of antibodies and the disease gets cured in most people.
What is the outcome of myasthenia gravis after treatment?
Earlier, the disease had a high morbidity and mortality, as treatments were not available. However, now, with good treatments available, more than 95% people do well and are fully cured.
I hope this articles helps people with myasthenia gravis as well as their caregivers. I would be pleased to answer any further queries.
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